Full text

Turn on search term navigation

1. Introduction

According to the definition provided by the China Cement Products Standardization Technical Committee, cement-based self-leveling mortar (CSL) is a specialized mortar composed of cement-based binding materials, aggregates, fillers, and admixtures, which exhibits high fluidity when mixed with water [1]. Due to its low cost, simplified construction process, rapid curing time, and smooth surface finish, CSL has been widely utilized in various applications, including flooring materials, indoor flooring, building walls, and 3D printing [2,3,4,5,6,7,8,9]. In its flowing state, CSL possesses excellent fluidity, pumpability, and self-leveling characteristics, which significantly streamline the construction process and minimize the need for manual intervention [10]. Furthermore, CSL demonstrates rapid setting properties, achieving immediate load-bearing capacity that is suitable for high-traffic and high-pressure applications shortly after curing [11].

In order to address potential issues such as delamination, segregation, and shrinkage cracking in CSL, a variety of admixtures are typically incorporated during the design phase of the mixture to enhance its performance. These admixtures include water reducers, water retainers, set retarders, defoamers, and expansion agents, among others [12,13]. Ge et al. [14] studied the effects of four water reducers: sodium lignosulfonate (LS), naphthalene superplasticizer (PNS), aliphatic superplasticizer (HSB), and polycarboxylate superplasticizers (PCE) on the fluidity of a cement slurry. They found that PCE provides the best dispersion performance for cement while achieving high fluidity and reducing the volume shrinkage of CSL. Patural et al. [15] conducted a comparative analysis of cellulose ether water-retaining agents with varying molecular weights, assessing their effects on the water retention and consistency of cement-based mortar. Their results demonstrated that an increase in the molecular weight of the water-retaining agent corresponded with improved consistency and water retention in the mortar. Wang et al. [13] evaluated the influence of different dosages of cellulose ether water-retaining agent (CE), tartaric acid retarder (TA), and PCE on CSL performance, identifying optimal dosages of CE at 0.6 wt‰, TA at 0.5 wt‰, and PCE at 2.0 wt‰. The incorporation of these admixtures can lead to a reduction in both the water–cement ratio and the cement ratio, while simultaneously enhancing the fluidity, surface characteristics, and mechanical properties of the mortar. Nevertheless, it is important to note that while the addition of various admixtures enhances the durability of CSL, it also results in increased economic costs [16,17]. Pan et al. [18] used carrot extract as a retarder for cement mortar; this natural admixture not only acts as a setting retarder, but also enhances compressive strength. The use of natural admixtures can meet the performance requirements of CSL while providing significant environmental and economic benefits.

Traditional CSL relies on Portland cement (PC) as the main cementitious material, and the CO2 emissions generated by its production process account for 8% of global CO2 emissions and consume significant natural resources. Meanwhile, the annual emission of industrial by-products exceeds 4 billion tons, with long-term accumulation leading to environmental issues such as land occupation and heavy metal pollution [5,19]. Although the performance of CSL can be optimized by adding additives, existing research still faces bottlenecks such as environmental and cost conflicts, and insufficient utilization of solid waste [20,21,22]. Lin et al. [5] found that phosphogypsum (PG) in CSL not only serves as a filler, but also directly participates in the hydration process of cement in self-leveling mortar. Wang et al. [23] found that incorporating TG into CSL enhances the density of the mortar’s structure, thereby improving both its strength and deformation capacity. Additionally, CSL mixed with industrial by-product gypsum offers superior thermal insulation, sound insulation, fire resistance, and environmental comfort, while also reducing carbon emissions by 20% [24]. Ceramic waste is a non-degradable material that can take up to 4000 years to decompose and is challenging to recycle [25]. Gruber et al. [26] investigated the use of PG and white ceramic waste to replace 50% of PC in CSL. The compressive strength of the CSL containing 50% white ceramic waste was measured at 32.66 ± 4.26 MPa after 28 days, demonstrating very low shrinkage and hydration heat. The mixed mortar with 50% PG also exhibited strong compressive, flexural, and bonding strengths. Given the low biodegradability of plastic waste and its substantial volume, processing this waste presents significant benefits for environmental protection. Safi et al. [27] investigated the use of recycled waste plastics as fine aggregate in CSL. The study found that increasing the plastic waste content enhanced the fluidity of the mortar. Although the compressive strength of mortar containing 20–50% plastic waste decreased by 15% to 33%, it still meets the mechanical performance requirements for CSL, as specified in the Chinese standard JC/T 985-2017 [1].

Due to the differences in test methods between international (ISO) and Chinese standard (JC/T 985-2017), high-performance admixtures are expensive, and excessive use may delay the development of strength; the dosage threshold of industrial by-products to replace cement, the pretreatment process, and its influence on the hydration mechanism are still unclear. This paper first analyzes the differences in the requirements for CSL fluidity, mechanical properties, and durability between Chinese and Western standards, establishing a universal performance evaluation framework. Secondly, it reveals the regulatory mechanisms of admixture molecular structure and molecular weight on the rheological properties and hydration process of CSL. Then, the key performance parameters of CSL produced by replacing cement with different industrial by-products are provided. It quantifies the feasibility of substituting cement with PG (≤55%), TG (≤45%), ceramic waste (50%), etc., and elucidates the mechanisms of their participation in hydration reactions. Based on the collection of existing research, a summary table of basic research information on the preparation of CSL from different industrial by-products is given. Finally, several constructive suggestions are put forward for future research on the use of admixtures and industrial by-products in CSL. This review provides help for the application and development of CSL.

2. CSL Test Methods and Standards

The physical properties of CSL in a flowing state primarily include fluidity and setting time. Fluidity is a critical factor that influences the ability of CSL to self-level the floor substrate. ISO 9597:2008 [28] provides stringent guidelines for the fluidity testing method. First, the mixed mortar is poured immediately into an open pipe mold with a diameter of 40 mm and a height of 50 mm. Next, the mold is lifted vertically by 50–100 mm within 2 s and held for 10–15 s to allow for the mortar to flow freely onto a glass plate. After 4 min, the diameter of the mortar is measured in two perpendicular directions; this measurement represents the initial fluidity. The diameter of the CSL is also measured after 20 min, referred to as the 20 min flowability. According to the Chinese Standard JC/T 985-2017 [1], the fluidity of qualified CSL should be ≥130 mm. The setting time directly influences the mortar’s ability to flow freely during application, the degree of void filling, and the smoothness of the floor surface. ISO 9597:2008 [28] specifies that the initial and final setting times of mortar should be measured using a Vicat needle apparatus. The initial setting time is defined as the duration from the completion of mixing until the Vicat needle penetrates less than 5 mm, while the final setting time is determined when the Vicat needle penetrates less than 1 mm. An excessively short setting time may lead to premature solidification of the mortar, adversely affecting its final strength and durability.

Mechanical properties such as tensile bond strength, impact resistance, abrasion resistance, and dimensional change rate are critical characteristics of CSL in their hardened state. These properties are influenced by the components of the mixture and their respective proportions. Typically, mortar prisms measuring 40 mm × 40 mm × 160 mm are prepared, demolded after curing for 24 h, and subjected to performance testing after a specified period. Compressive strength and flexural strength tests are conducted at day 1 day and day 28 in accordance with ISO 679:2009 [29] for subsequent mechanical evaluation. A high tensile bond strength ensures that the CSL adheres securely to the underlying surface, contributing to the formation of a smooth finish. ISO 13007-2:2013 [30] stipulates that the specimen cured for 27 days should be bonded to the instrument. After 1 day, the load should be applied at a speed of (5 ± 1) mm/min until the specimen is destroyed. The tensile bond strength is calculated according to Formula (1). JC/T 985-2017 [1] requires the CSL test block not to crack or detach from the base plate after the impact resistance test. ISO 10545-6:2010 [31] recommends using corundum with a particle size of F80 as an abrasive to test the wear resistance of CSL at 75 r/min, and believes that after 150 revolutions, the CSL test block with a grinding pit volume less than 400 mm3 has better wear resistance. According to the Chinese standard JGJ/T 70-2009 [32], the drying shrinkage test of CSL specimens was carried out. First, the reference length of each group was measured after the specimens were cured for 24 h. Then, the length of each specimen after a certain number of days of curing was recorded, and its drying shrinkage rate was determined according to Formula (2). Table 1 summarizes the characteristics of CSL, and the standards and requirements based on the specifications.

(1)P=FS

where P is the tensile bond strength (MPa); F is the maximum failure load in Newtons (N); and S is the bonding area (mm2).

(2)ε=L0−LnL−Ld × 100%

where ε is the shrinkage value, L0 is the initial length of the sample, Ln is the length after n days, L = 160 mm, Ld is the sum of the lengths of the two shrinkage heads buried in the mortar sample.

3. CSL Component Material Types and Characteristics

3.1. Cementitious Materials

In recent decades, rising labor costs and increasing user demand for mortar workability (rapid setting, fluidity, shrinkage compensation, and smoothness) have led to the widespread use of CSLs with high fluidity and self-smoothing properties. These materials are now commonly employed in various sectors, including office buildings, apartments, retail spaces, schools, hospitals, factories, parking lots, ships, and other new construction and maintenance projects [4,11,33,34,35]. As mentioned above, cementitious materials, aggregates, fillers, admixtures, and water typically compose CSL systems [5,20,24,36,37]. PC is the most commonly used binder in CSL, as it enhances the material’s cohesion and mechanical properties [38]. However, the production of PC is invariably associated with significant CO2 emissions and high energy consumption, which has become a pressing resource and environmental concern in the application of CSL [16]. Calcium sulfoaluminate cement (CSA) is regarded as a more environmentally friendly and cost-effective binder for self-leveling systems. Compared to PC, CSA clinker requires less limestone in the manufacturing process, has a lower calcination temperature, and exhibits greater brittleness. These characteristics contribute to reduced carbon dioxide emissions and lower energy consumption [39,40,41,42,43]. Li et al. [16] utilized CSA to replace PC in a traditional ternary system consisting of PC, calcium aluminate cement (CAC), and calcium sulfate, resulting in the preparation of CSL with commendable performance. The hydration of CAC-based mortar is mainly related to the formation of ettringite and aluminum hydroxide. When the calcium sulfate in the system is depleted, ettringite dissolves, and monosulfate precipitates [4]. From a hydration perspective, calcium sulfoaluminate (CSA) also produces ettringite and aluminum hydroxide as hydration products. Conversely, once the sulfate in the pore solution is depleted and sufficient free water is available, monosulfate is formed. Additionally, the cost of CSA is only 25–50% of that of CAC, and CSL prepared with CAS cement clinker exhibits excellent mechanical properties and shrinkage compensation [11].

3.2. Aggregate

Sand is typically the aggregate and main component of a CSL mixture. The type, particle size, and shape of the sand significantly influence the fluidity, consistency, strength, water consumption, and segregation of CSL, as well as the production cost. In a study by Scolaro and Rocha [36], the effects of three different types of quartz sand on the performance of CSL were examined. The findings indicated that the shape and texture of the sand particles did not appear to have a substantial impact on the performance of CSL. The finer the particle size of sand, the better the performance of CSL. He et al. [44] proposed morphological indexes for sand particles with varying gradations. Their study concluded that the performance of sand particles exhibiting mortar morphology with influence factors between 0.86 and 1.08 is relatively excellent. Zhang et al. [45] utilized low-grade fly ash as a substitute for natural river sand in the preparation of mortar, which demonstrated good performance. This approach significantly contributes to alleviating the shortage of natural river sand resources, reducing pollution, and enhancing the utilization of solid waste resources. Canbaz et al. [46] produced CSL using three types of aggregates and a new generation of high-efficiency water reducers. They conducted a series of tests to evaluate slump, compressive strength, weight, ultrasonic pulse velocity, water absorption, shear strength, and other properties. The results indicated that finer aggregate particle sizes improved material fluidity. Notably, river sand with a particle size of 0–1 mm combined with 1% water reducer exhibited the best workability in CSL.

3.3. Filling Material

With the rapid development of industry and urbanization, the amount of solid waste generated in cities is increasing. Solid wastes such as fly ash (FA), limestone powder (LSP), waste brick powder (WBP), steel slag, and desulfurization ash have significantly impacted ecological development, and their treatment and utilization have consistently attracted considerable attention [47,48,49,50]. In recent years, the incorporation and utilization of these solid wastes in CSL have gradually become a prominent topic in both research and application. FA, which has a high content of silicon and alumina, features spherical particles that are similar in size to ordinary cement, making it an excellent additive for CSL [51]. Previous studies have demonstrated that FA can enhance the flowability and stability of mortar, as well as improve the densification and mechanical properties of its structure [2,52,53]. Moreover, FA can slow the setting time of mortar, facilitate pouring, and decrease early heat generation, thereby minimizing shrinkage. LSP filler is another commonly used material that can increase the filling capacity of the cement particle skeleton while maintaining the cohesiveness and anti-segregation properties of cement-based systems [54,55]. Reusing industrial waste and by-products as fillers for CSL raw materials is another advantage and can also be considered a sustainable waste solution [38]. The ceramic brick industry produces a significant amount of sintered clay brick waste, which typically exhibits some pozzolanic activity and can react with calcium hydroxide to form compounds that enhance strength and durability [56,57]. Zhao et al. [58] utilized WBP to partially or fully replace limestone filler at rates of 50% and 100%, resulting in early strength reductions of 5.6% and 9.3% in the mortar, respectively. However, this decline was mitigated by the pozzolanic activity of WBP, which further improved the strength at 28 days. Rizwan et al. [59] investigated the effects of mixed materials derived from various solid wastes on the fluidity, strength, microstructure, relative water absorption, and early volume stability of cement-based systems. They found that the inclusion of FA and LSP in the solid waste resulted in improved overall performance of the mortar. Xu et al. [60] discovered that incorporating a small amount of LSP to replace FA in mortar can enhance the strength of CSL. LSP effectively fills the pores of the mortar and promotes the formation of AFt. However, as the content of LSP increases, some LPs that do not participate in the reaction may have a dilution effect, leading to a reduction in the mechanical properties of the mortar. These studies provide valuable data and support for the application of limestone powder and fly ash composite systems, as well as various solid wastes in CSL.

3.4. Types of Admixtures in CSL

3.4.1. Water Reducing Agent

High-efficiency water reducers have become essential CSL formulations. Over the past 30 years, polycarboxylate superplasticizers (PCEs) have emerged as the most widely used superplasticizers in CSL due to their high water reduction rates and the ease with which their polymer structures can be modified to achieve desired properties [13,37,61,62]. As illustrated in Figure 1, when PCE is introduced into the cement slurry system, it is rapidly adsorbed onto the surfaces of cement particles due to the strong electrostatic interactions between the carboxylic acid groups in PCE and the highly charged mineral surfaces [63,64]. Concurrently, the steric effects between cement particles result in a significant increase in their dispersibility, thereby facilitating a high water reduction rate [65].

The effects of water reducers on the CSL fluidity, setting time, and crystal morphology of cementitious materials depend on the length and density of the side chain groups. Dalas et al. [66] analyzed the influence of PCE side chain length, density, and anion functionality (carboxylate, dicarboxylate, or phosphate) on adsorption. They found that modifying the anion is an effective technical approach to enhance PCE performance. Chuang et al. [67] observed that as the length of the PCE side chain group increased, the steric hindrance effect in the mortar became more pronounced, leading to greater dispersion among the cement molecules. Specifically, longer side chain groups generate greater steric hindrance around themselves. Furthermore, Liu et al. [68] discovered that PCE adsorption reduces the hydration rate of the mortar and alters the morphology and size of the crystals. This delayed hydration caused by comb PCE can also impede the early strength development of the mortar, negatively impacting its overall strength growth [62].

Zhang et al. [62] synthesized polycarboxylate ethers (PCEs) using acrylic acid (AA) and α-methylallyl-ω-hydroxypolyethylene glycol ether (HPEG) as primary monomers. By employing HPEG macromonomers with 53 repeating units (−CH2−CH2−O−), PCEs with AA/HPEG ratios of 6:1, 4:1, and 2:1 were prepared. The resulting polymers were designated as P53-6, P53-4, and P53-2, corresponding to their side chain density from high to low. Additionally, using HPEG macromonomers with 89, 53, and 10 repeating units (−CH2−CH2−O−), while maintaining the AA-to-HPEG ratio at 4:1, PCEs with varying side chain lengths were synthesized. These polymers were labeled P89-4, P53-4, and P10-4, reflecting their side chain lengths from high to low. The chemical structure of the synthesized PCEs is illustrated in Figure 2. The incorporation of different types of PCEs enhanced the fluidity of the mortar. When the side chain density was held constant, PCEs with shorter side chain lengths (Figure 3a) and those with a lower side chain density (Figure 3b) for the same side chain length exhibited higher adsorption capacity. Furthermore, it was observed that PCEs with longer side chains and higher side chain density were more favorable for early strength development (Figure 3c). In summary, as the side chain length and density of the water reducer increase, the adsorption amount decreases, while the early strength of the mortar increases [37,62,67,69,70].

Nanotechnology is an emerging field that manipulates and controls matter at the molecular level. It has enabled the scientific community to develop a variety of advanced materials applicable across multiple disciplines [71]. Miao et al. [72] utilized colloidal nano-silica (NNS) to synthesize polycarboxylate ether (PCE) containing Si-OH functional groups. Due to its superior mechanical strength, ultrafine size, pozzolanic reactivity, and excellent compatibility with cement hydrates, this new type of PCE can enhance the mechanical properties (Figure 4a) and reduce porosity (Figure 4b) of mortar while maintaining good dispersibility. The aforementioned studies indicate that modifying the structure of PCE polymers can significantly improve fluidization efficiency [73,74] and the retardation effect of PCE [75,76,77,78].

3.4.2. Water Retention Agent

Water-retaining agents primarily consist of water-soluble polymer compounds, including polyacrylates, cellulose, and natural rubber. Cellulose ether (CE) is a widely utilized water-soluble polymer for water retention modification in CSL, owing to its exceptional water-retaining and thickening properties [13,69,79,80]. CE includes hydroxypropyl methyl cellulose (HPMC), hydroxyethyl methyl cellulose (HEMC), and hydroxyethyl cellulose (HEC) [69,81]. In the production process, CE is reactivated using active sodium and subsequently reacted with functional polymers, such as methyl chloride, ethylene oxide, or propylene oxide, to produce various types of cellulose ethers [69]. The typical manufacturing process of cellulose ether is illustrated in Figure 5.

Pourchez et al. [81] found that CE is a significant controlling factor for water transport and the evolution of porous structures in mortar. The addition of CE can increase the number of pores and capillaries within the mortar. A reduction in pore size slows the transfer rate of fluid in the liquid phase. Vapor diffusion, assisted by liquid flow, primarily occurs in larger voids (Figure 6), thereby enhancing the water retention capacity of the mortar. Li et al. [82] proposed a model, illustrated in Figure 7, to explain how CE functions as a medium for water migration, influencing the hydration of CSA cement/mortar under various conditions. A CE film forms within the cement matrix. As a hydrophilic material, this CE film likely serves as a conduit for water to penetrate partially hydrated cement particles, thereby reducing the duration of the stagnation period. In CSA mortar containing sand fillers, the sand is embedded within the cement hydrate. This can lead to the formation of defects or channels at the interface between the cement hydration products and the sand, which allows for water to migrate to the non-hydrated cement particles. This process results in slow but continuous hydration, making it challenging for the mortar hydration to reach a stagnation period. The addition of a chemical additive, such as a water-retaining agent, regulates the migration rate of water within the cement/mortar matrix and promotes the hydration reaction. Patural et al. [15] found that water-retaining agents can enhance the consistency of fresh mortar, in addition to improving water retention, workability, and the usable time of the mortar. The dosage of CE significantly influences the water retention mechanism of CSL. At low doses, water retention is achieved through intramolecular water adsorption and associated swelling. At higher doses, a hydrogel-like three-dimensional polymer network forms, which blocks pores in the mortar matrix, thereby enhancing water retention [83,84,85]. As the molecular weight of CE increases, the yield stress decreases, consistency improves, and water retention increases. A comparative study examining the impact of CE on the water retention properties of various cement mortars (Figure 8) found that even a low content of CE can significantly enhance the water retention properties of different types of mortars [86,87,88].

The influence of CE on mortar is also evident in its mechanical properties. Kim and Kang [89] found that the addition of CE increased the water retention of the mortar, which facilitated the hydration of C3S and C2S, thereby improving the bonding strength of the mortar after drying. Li et al. [69] investigated the effects of three types of CE—HEC, HEMC, and HPMC—on the mechanical strength of CSA cement mortar (Figure 9). They discovered that HEC had the least impact on the mechanical properties of the mortar. However, CE also delays the hydration of cement, which prolongs the setting time and reduces early strength. These effects are generally recognized as the side effects of CE [90,91,92].

3.4.3. Retarder

Unlike the rheological optimization provided by PCE or the moisture retention offered by CE, set retarders extend the setting time by slowing down the hydration reaction rate. This extension ensures adequate working time for large-scale construction projects while preventing plastic cracking that can occur due to rapid water evaporation [93,94,95]. Commonly used retarders include tartaric acid (TA) [96,97], citric acid (CA) [98,99,100], sodium tripolyphosphate (STPP) [101,102] and protein salt (PS) [2]. These retarders are typically low-molecular-weight organic compounds that contain multiple carboxyl groups. The low molecular weight characteristic facilitates the adsorption of acid radical ions onto the surface of Portland cement particles, thereby delaying cement hydration [103]. STPP is classified as an alkaline phosphate retarder. These alkaline phosphate retarders exist in the form of sodium salts and contain multiple identical [NaPO3]2− structural units (Table 2), which contribute to their excellent retarding performance [104]. Proteins, characterized by their green, renewable, abundant, and non-polluting nature, have emerged as potential retarders for the CSL industry and have been extensively studied [104,105,106].

TA is a green retarder that can be produced from waste materials in the wine or juice industry [107,108]. Wang et al. [13] investigated the effects of adding TA on the fluidity (Figure 10a) and mechanical properties (Figure 10b) of CSL. The addition of TA slowed down the hydration reaction process of the mortar, prolonged the setting time, and increased the fluidity of CSL within the same time frame. The mechanical properties initially increased and then decreased with the rising TA content, peaking at a TA concentration of 0.4 wt‰. Notably, after 5 h, the blocking effect of TA on silicate minerals diminished, which facilitated an increase in the precipitation rate of hydration products such as calcium hydroxide and helped maintain the early strength of the mortar [109]. Kastiukas et al. [103] studied the effect of CA on the early engineering properties of CSL. Their findings indicated that the incorporation of CA resulted in a reduction of both compressive strength (Figure 11a) and flexural strength (Figure 11b) of the mortar. Furthermore, a higher concentration of CA inhibited the dissolution of cement particles (Figure 11c). J. Plank elucidated the incompatibility between cement and CA in CSL through the lens of competitive adsorption. CA demonstrates a stronger competitive adsorption capability compared to tartaric acid (TA), leading to a more pronounced detrimental effect on the mechanical properties of CSL [110]. Ltifi et al. [111] conducted various tests on PC with different amounts of STPP and found that as the STPP content increased, both the viscosity of the mortar and the degree of delay in cement hydration also increased. This phenomenon occurs because STPP reacts with Ca2+ ions in the cement mortar to form the complex [CaP3O10]3−. This complex subsequently interacts with Ca2+ and Al3+ ions on the surface of cement particles, creating an electric double-layer structure that enhances electrostatic repulsion between the particles. Consequently, the contact area between cement particles and water is reduced, delaying the cement hydration process and thereby achieving a retarding effect [112].

Ding et al. [106] utilized acrylic acid (AA) and acrylamide as raw materials to modify collagen hydrolysate (CH) derived from chrome waste through graft copolymerization, resulting in the synthesis of grafted collagen hydrolysate (GCH) for cement retardation. As the dosage of GCH increased, the setting time of the cement also extended (Figure 12a), indicating that GCH exhibits a significant cement retardation effect. Figure 12b illustrates that the addition of GCH inhibits the formation of Ca(OH)2 at 3640 cm−1 in the infrared spectrum, with this inhibitory effect becoming more pronounced as the amount of GCH increases. Figure 13a shows that cement without GCH consists of uniform needle-shaped crystals that are intertwined. In contrast, the incorporation of GCH leads to a reduction in mesh-like crystals, resulting in a smoother cement structure (Figure 13b,c). This study demonstrates that GCH not only influences the hydration rate of cement reactants, but also alters the crystal morphology of the hydration products. Their research not only effectively recovers chrome scale waste, but also provides a valuable reference for the development of protein-based retarders in CSL.

3.4.4. Other Admixtures

In addition, redispersible latex powder [113], defoaming agent [114], suspension stabilizer [115], slump retaining agent [46,116], expansion agent [117], and accelerating admixture [118] are also used in combination with CSL. The incorporation of these admixtures can reduce the porosity of CSL materials, enhance the initial hydration rate, prevent mortar segregation, and minimize shrinkage in the mortar. However, there is limited research on these admixtures, and further studies are necessary to elucidate the mechanisms and assess the feasibility of these admixtures in influencing the performance of CSL.

4. New Green CSL

4.1. Recycling Industrial Waste and By-Products During CSL Production

The production of cement in CSL will lead to an increase in greenhouse gas emissions, including CO2, NOx, and SOx [38]. However, certain by-products, such as by-product gypsum, limestone powder (LP), and porcelain waste, can serve as substitutes for natural resources and cement in the composition of CSL. The reuse of these industrial by-products not only reduces the energy consumption associated with processing natural resources, but also contributes to a decrease in greenhouse gas emissions and other harmful pollutants [119]. Lin et al. [5] explored the use of raw by-PG as a material for producing CSL. For CSL mixed with PG, it is essential to achieve good flowability, mechanical properties, bonding strength, and wear resistance. Research has demonstrated that CSLs containing more than 40% PG exhibit improved fluidity (Figure 14a) and do not experience significant loss of mechanical properties (Figure 14b). This occurs because when PCE is incorporated into the system with gypsum particles, the gypsum particles rapidly release Ca2+ and SO42− into the solution, exposing a large number of active sites. The carboxyl groups in PCE molecules react with Ca2+ to form compounds that adsorb onto the surface of the gypsum particles, providing steric hindrance that facilitates the dispersion of the gypsum particles and enhances their mobility [120]. In addition, as the content of PG increases, the shrinkage rate, bonding strength, and wear resistance of CSL all decrease (Figure 14c). According to the performance requirements outlined in JC/T 985-2017 [1], the PG content should not exceed 55%. Furthermore, to investigate the role of PG in CSL, X-ray diffraction (XRD) analysis was conducted on CSL samples with varying levels of PG doping. Figure 15 presents the XRD pattern of the hardened slurry with a composition of CSA: OPC: PG = 12: 8: x. It was observed that the volume of AFt increased with rising PG content and stabilized when x > 10. When x ≤ 10, the diffraction peak of gypsum was detectable at 1 day (Figure 15a). As hydration progressed, the diffraction peak of gypsum disappeared by 28 days (Figure 15b), indicating that the PG in CSL could be completely consumed. However, when x > 10, an excessive amount of PG may lead to a decline in CSL performance.

Titanium gypsum (TG) is an industrial solid waste primarily composed of CaSO4·2H2O. Due to its high free water content, significant impurity levels, poor mechanical properties, and challenges associated with recycling, the annual emissions of TG in China have reached 30 million tons [121]. Currently, research has explored the use of TG as a cement retarder, a binding material, and for the production of lightweight wall materials and roadbed materials; however, the application of TG remains limited [122,123,124,125]. Wang et al. [23] utilized TG as a raw material for the preparation of CSL, incorporating varying proportions of TG to replace cement in CSL. Research has demonstrated that, under a fixed PC/CSA ratio, the flowability of the mortar decreases as the amount of TG increases (Figure 16a). This trend can be attributed to the microstructure of TG, which predominantly consists of long columns and flakes, along with a significant quantity of spherical and flocculent impurities. The irregular accumulation of minerals in diverse shapes creates additional pores, leading to increased water absorption and reduced fluidity of the mortar. After the addition of TG to the CSA-PC-based mortar, the C-S-H gel produced by cement hydration fills the spaces between the TG structures, enhancing the compactness and mechanical properties of the mortar. However, an excessively high TG ratio can diminish the amount of C-S-H gel generated during cement hydration, leading to a reduction in strength (Figure 16b). Furthermore, under the influence of the C-S-H gel, some TG participates in the hydration process of C3A, resulting in the formation of additional Aft. Conversely, when the TG content is too high, the C-S-H gel is compromised by an excess of CaSO4·2H2O. In this scenario, TG primarily acts as a filler within the material, which negatively impacts the microstructure and compactness of the cement-based matrix. The underlying mechanism is illustrated in Figure 17. Additionally, the Ca2+ ions released by TG chelate with the retarder in the CSL system, leading to a reduction in both Ca2+ concentration and ionic activity. This decrease, in turn, inhibits the hydration of gypsum crystals as they transition from the hemihydrate to the dihydrate form [105].

Pereira and Camarini [126] investigated the feasibility and applicability of incorporating two types of porcelain waste into CSL, using porcelain waste as a substitute for cement. They concluded that although the two types of porcelain waste reduced flow and prolonged the setting time, they enhanced the compressive strength of CSL. Additionally, the water absorption and permeability of CSL mixed with porcelain slag met the specifications’ requirements.

The commonalities identified in the studies above suggest that it is feasible to partially substitute CSL materials with industrial by-products in CSL production. By carefully controlling the proportion of industrial by-products incorporated, the overall properties—such as mechanical strength, flowability, setting time, bonding strength, shrinkage rate, and wear resistance—of CSL containing these by-products can effectively meet the requirements outlined in the Chinese standard JC/T 985-2017 for CSL performance.

4.2. Historical Research on and Latest Engineering Applications of Industrial By-Products in CSL Production

Table 3 summarizes the application dosage and performance impact of various industrial by-products in CSL in chronological order. The data indicate that most industrial by-products, or their combinations, such as plastic waste (PW), white ceramic waste (CB), natural phosphogypsum (PN), red ceramic waste (C), insulator porcelain waste (P), PG, phosphorus building gypsum (PBG), flue gas desulfurization gypsum (FGDG), natural anhydrite (NA), ground slate (GS), and sugarcane bagasse ash (SCBA), have varying effects on CSL mixtures. These industrial by-products influence the performance of CSL in both fresh and hardened states in different ways.

The summary table indicates that incorporating white ceramics into CSL results in a lower shrinkage rate and enhanced mechanical properties [26]. One of the most prevalent industrial by-products, PG, can significantly improve the flowability of CSL due to the smaller particle size of PG waste after calcination, which enhances its flow characteristics [26]. However, adding more than 55% PG may lead to a decline in the performance of CSL mixtures, potentially due to variations in gypsum hydration products and bonding structures [21]. When these green adhesives are added individually, PG demonstrates the most significant improvement in processability; however, as the amount of PG increases, the early strength of the mixture tends to decrease. An analysis of the flowability and hardening properties of CSL reveals that PG is a promising candidate material for CSL applications [21,26,126,127]. Additionally, some studies have highlighted the effects of other industrial by-products, such as NA, SCBA, GS, and FGDG, on the performance of CSL [11,128,129,130].

Table 3

Basic research on the preparation of CSL using different green materials.

Year Green Binder Other Material Dosage Mortar Property Ref.
A B C D E F G H I
2010 GS PC, Sand GS: 0–45 total wt. % √ X X X X √ [129]
2013 PW PC, Sand, LP PW: 0–50 total wt. % √ X X √ √ [27]
2016 PG PC, CSA, Sand PG: 45–55 total wt. % √ √ X X [5]
2017 PG PC, CSA, Sand PG: 19.80 total wt. % √ √ X X X [6]
2017 NA CSA, Sand, LP NA: 0–35 total wt. % √ √ √ √ √ [11]
2018 P, C PC, Sand P: 15–50 PC wt. % √ √ √ X [126]
2018 P, C PC, Sand C: 15–50 PC wt. % √ √ X X [126]
2019 PBG CSA, PC, Granulated blast furnace slags, Sand PBG: 50 total wt. % √ √ √ √ √ √ [127]
2020 Marble and granite cutting waste (MGCW) PC, Sand MGCW: 40–50 total wt. % √ √ √ √ √ √ √ [131]
2020 SCBA PC, Sand, LP SCBA: 0–30 total wt. % X √ √ √ √ X [128]
2021 FGDG PC, Mechanochemical Syngenite, Sand, Quartz flour FGDG: 35 total wt. % X X √ √ √ √ [130]
2023 fluorogypsum (FLG) PC, Sand FLG: 92 total wt. % √ √ √ √ √ √ [19]
2024 FGDG, PG CSA, Sand PG: 90 total wt. % √ √ √ √ [21]
2024 FGDG, PG CSA, Sand FGDG: 90–100 total wt. % √ √ √ √ [21]
2024 Red mud (RM) PG, FA, Sand, Quicklime, PC RM: 11–26 total wt. % √ √ √ √ [132]
2024 PG RM, FA, Sand, Quicklime, PC PG: 11–26 total wt. % √ √ X X [132]
2024 PG, CB, PN PC, Sand PG: 474.09 kg/m3 √ √ X √ X √ [26]
2024 PG, CB, PN PC, Sand CB: 474.09 kg/m3 √ √ √ √ √ √ [26]
2024 PG, CB, PN PC, Sand PN: 474.09 kg/m3 √ X X √ X √ [26]

Note: A: liquidity; B: setting time; C: compressive strength; D: flexural strength; E: shrinkage rate; F: porosity; G: slump; H: water absorption; I: segregation. The symbols √ and X represent the positive and negative effects of industrial by-products on the performance of CSL, respectively.

5. Conclusions

This study presents the testing indicators and performance requirements for CSL in international and Chinese standards. It reviews the composition materials of CSL, discusses the types of additives used in CSL, and examines their impact on CSL performance. Additionally, the role and effectiveness of industrial by-products applied in CSL were thoroughly explored and compared. The following conclusions were drawn:

The rapid popularization of CSL is directly related to the standardization framework established by current standards (such as JC/T 985, ISO). These standards provide a clear benchmark for the normative application of CSL through quantitative indicators.

The performance of CSL is mainly affected by the composition of cementitious materials, aggregates, and fillers. Through the performance analysis of different CSLs, it can be seen that the addition of CSA instead of PC can optimize the formation of ettringite, thereby increasing the compressive strength of 28 days and reducing carbon dioxide emissions by 30% to 50%. The fine sand with a particle size of 0–1 mm has the best performance in CSL. Fly ash can enhance the fluidity and stability of CSL and improve its compactness and mechanical properties.

Water reducers, water retainers, and retarders significantly enhance the fluidity, mechanical properties, and durability of CSL by optimizing the water–cement ratio, regulating the hydration process, and improving the microstructure. Among these additives, the molecular structure of PCE (side chain length and density) directly influences its adsorption characteristics and early strength development; cellulose ether improves water retention by forming a three-dimensional network; however, excessive use of these admixtures may delay hydration and diminish early strength.

Industrial by-products such as PG, TG, ceramic waste, and limestone powder can partially replace traditional cementitious materials or aggregates, thereby reducing the environmental impact of CSL. When PG is added to the CSL system at a concentration of 55% or less, the performance of the mortar can be improved, and carbon emissions can be reduced. The incorporation of ceramic waste at 55% can enhance compressive strength, reduce shrinkage, and prolong setting time. By controlling the incorporation ratio of industrial by-products, various green CSLs can meet the requirements of mechanical properties and workability in relevant standards (JC/T 985-2017).

The use of a single admixture or by-product presents certain limitations, including the negative impact of PCE on early strength and the interference of impurities found in industrial waste with workability. To enhance overall performance, it is essential to utilize combinations of multiple admixtures or to implement synergistic modifications using by-products, such as a composite system that incorporates both fly ash and limestone powder. Additionally, the environmental risks related to the toxicity and heavy metal leaching of industrial by-products necessitate a systematic evaluation.

6. Outlook and Prospect

CSL has a wide range of applications across various fields of civil engineering. Based on the observations presented in this review, the author proposes several aspects that should be considered in future CSL research:

Future aims should be to advance the research and development of high-durability CSL materials that incorporate integrated functionalities, including waterproofing, fire resistance, and antimicrobial properties, as well as establish a comprehensive lifecycle performance evaluation system that encompasses flatness retention rate, crack resistance coefficient, and color difference stability, while ensuring the functional stability of the materials under extreme temperature and humidity conditions.

In subsequent research, fiber materials and nano-mineral additives can be incorporated into mortar to enhance its strength, toughness, and durability. Simultaneously, the balance between compressive strength and initial fluidity was optimized through orthogonal testing.

While evaluating the performance of admixtures, it is essential to consider their potential negative effects on CSL properties. Addressing the issue of crystal structure alteration caused by admixtures represents a crucial direction for the future advancement of CSL technology. Furthermore, the development of new admixtures must also fully leverage the unique chemical structures and mechanisms of action of existing admixtures.

There are still many areas that require further investigation regarding the influence of gypsum on the performance of CSL. Future research will focus on conducting pre-treatments, such as dehydration, alkalization, ball milling, and calcination, on various industrial by-product gypsum to enhance the compatibility between gypsum crystals and cement paste.

Various combinations of industrial by-products can be utilized to produce CSL, leveraging the synergistic effects of these by-products to enhance both the fresh and hardening performance of CSL. Materials exhibiting performance deficiencies can be compensated for by incorporating alternative materials. Furthermore, it is essential to explore the potential of other environmentally friendly adhesives in CSL, as many remain underutilized and have not been fully developed. This category of industrial waste and by-products includes polymer resins, pollutants from tannery wastewater, ash from Prosopis juliflora, thermosetting plastic waste, waste glass, eggshells, sludge from sewage treatment plants, ground concrete waste powder, and undeveloped waste from the paper and pulp industry, among others.

When utilizing industrial by-products, it is essential not only to consider the properties of the materials themselves but also to assess their environmental impact, including factors such as toxicity, corrosiveness, leaching rates of heavy metals, flammability, and reactivity. The integration of mass spectrometry with gas chromatography or liquid chromatography is facilitated by a comprehensive four-stage evaluation framework. This framework includes screening, mechanism analysis, process simulation, and engineering validation, enabling full-chain risk management of industrial by-products from laboratory research to engineering applications.

Author Contributions

Conceptualization, M.Z., P.Z. and F.D.; methodology, H.M. and H.L.; formal analysis, H.M. and M.Z.; investigation, H.M., H.L. and M.H.; resources, P.Z.; data curation, H.M., W.W. and M.H.; writing—original draft preparation, X.Y., H.M. and W.W.; writing—review and editing, F.D. and P.Z.; supervision, X.Y., F.D. and M.Z.; funding acquisition, M.Z. All authors have read and agreed to the published version of the manuscript.

 Data Availability Statement

No new data were created or analyzed in this study.

 Acknowledgments

M.Z. acknowledges support from the National Natural Science Foundation of China (NSFC) project. M.Z. acknowledges support from the Open Fund of Key Laboratory of solid waste treatment and resource recycle, ministry of education project.

 Conflicts of Interest

The authors declare no conflicts of interest.

Footnotes

Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Figures and Tables

Figure 1 Schematic diagram of the PCE adsorption process on the cement particle surface.

Figure 2 Chemical formula for synthesizing PCEs (n = 89, 53, 10; a:b = 1:2, 1:4, 1:6) [62] (permission has been granted).

Figure 3 Effects of various types of PCE dosages on mortar fluidity, adsorption, and mechanical properties. (a) Effects of different side chain lengths on fluidity and adsorption; (b) effects of varying side chain densities on fluidity and adsorption; (c) effects of different types of PCEs on mechanical properties. Adapted from [62] (permission has been granted).

Figure 4 Effects of different PCE@NNS dosages on mechanical properties and porosity of mortar: (a) mechanical properties and (b) pore distribution. Adapted from [72] (permission has been granted).

Figure 5 Typical manufacturing process of cellulose ether.

Figure 6 Modeling of the porous network characteristics of HPMC, and describing water transport through this specific microstructure [81].

Figure 7 Effect of CE on the hydration process of CSA cement mortar [82] (permission has been granted). The yellow line in the diagram indicates the CE molecules embedded on the surface of the cement particles, and the blue triangle indicates the accumulated hydration products. These figures are the different characteristics of CE and Hydrates in the image annotation information.

Figure 8 Effect of CE on the water retention of different types of cement (among these, OPC refers to ordinary Portland cement, P·II denotes Portland cement with an addition of 5% limestone or slag, CSA2 contains a higher proportion of dicalcium silicate (C2S), and CSA1 has a greater amount of anhydrous calcium sulphoaluminate).

Figure 9 Effects of different types of CE on the mechanical properties of mortar: (a) compressive strength and (b) flexural strength.

Figure 10 Effect of different TA dosages on mortar properties: (a) fluidity and (b) mechanical properties.

Figure 11 (a) Effect of different CA dosages on mortar compressive strength; (b) effect of different CA dosages on mortar flexural strength; (c) SEM image of mortar with 3% CA dosage at 28 days. Adapted from [103] (permission has been granted).

Figure 12 (a) The relationship between the amount of GCH and the setting time of cement; (b) FTIR spectra of cement mortar with varying GCH content [106] (permission has been granted).

Figure 13 The effect of varying GCH contents on the microstructure of hardened cement: (a) 0%, (b) 0.3%, (c) 0.5% [106] (permission has been granted).

Figure 14 (a) Effect of PG content on the fluidity of CSL; (b) effect of PG content on the flexural and compressive strength; (c) effects of PG content on shrinkage (η), bond strength (B) and wear resistance (W) [5] (permission has been granted).

Figure 15 XRD patterns of hardened pastes with different PG content: (a) 1 day, (b) 28 days [5] (permission has been granted).

Figure 16 (a) The effect of TG content on the fluidity of CSL; (b) effect of TG content on the mechanical properties of CSL.

Figure 17 The influence mechanism of different TG contents on the hydration process of CSL.

CSL characteristics, and the standards and test requirements.

CSL Property Standard Test Description Requirement (JC/T 985-2017) [1]
Appearance JC/T 985-2017 [1] Cementitious self-leveling compound for floor Uniform, no lumps, no other objects
Initial fluidity/mm ISO 9597:2008 [28] Cement—Test methods—Determination of setting time and soundness ≥130
20 min fluidity/mm ≥130
24 h flexural strength/MPa ISO 679:2009 [29] Cement—Test methods—Determination of strength ≥2.0
24 h compressive strength/MPa ≥6.0
28 d flexural strength/MPa ≥6.0
28 d compressive strength/MPa ≥25.0
28 d tensile bond strength/MPa ISO 13007-2:2013 [30] Ceramic tiles—Grouts and adhesives—Part 2: Test methods for adhesives ≥1.5
Shrinkage/% JGJ/T 70-2009 [32] Standard for test method of performance on building mortar −0.10~+0.10
Impact resistance JC/T 985-2017 [1] Cementitious self-leveling compound for floor No cracking or detachment from the base plate
Wear resistance/mm3 ISO 10545-6:2010 [31] Ceramic tiles-Part 6: Determination of resistance to deep abrasion for unglazed tiles ≤400

Performance studies of some retarders.

Organic Acid Retarder Structural Structure Functional Group Molecular Weight
Citric acid (CA) [Image omitted. Please see PDF.] —COOH—OH 192
Tartaric acid (TA) [Image omitted. Please see PDF.] —COOH—OH 150
Sodium tripolyphosphate (STPP) [Image omitted. Please see PDF.] — 368

1.JC/T 985-2017 Cementitious Self-Levelling Compound for Floor; Ministry of Industry and Information Technology of the People’s Republic of China: Beijing, China, 2007; pp. 1-13. Available online: http://www.weboos.cn/assets/basicStandard/std_1361508.pdf (accessed on 7 September 2024).

2. Zhi, Z.; Huang, J.; Guo, Y.; Lu, S.; Ma, B. Effect of chemical admixtures on setting time, fluidity and mechanical properties of phosphorus gypsum based self-leveling mortar. KSCE J. Civ. Eng.; 2016; 21, pp. 1836-1843. [DOI: https://dx.doi.org/10.1007/s12205-016-0849-y]

3. Wu, M.; Zhao, Q.; Shen, W.; Zhao, J.; Xu, G.; Zhao, D.; Xiong, X. Mix design of self-levelling mortar prepared by curshed sand with high flowability and early strengthening. Constr. Build. Mater.; 2021; 283, 122679. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2021.122679]

4. Onishi, K.; Bier, T.A. Investigation into relations among technological properties, hydration kinetics and early age hydration of self-leveling underlayments. Cem. Concr. Res.; 2010; 40, pp. 1034-1040. [DOI: https://dx.doi.org/10.1016/j.cemconres.2010.03.004]

5. Lin, Y.; Yunsheng, Z.; Yun, Y. Utilization of original phosphogypsum as raw material for the preparation of self-leveling mortar. J. Clean. Prod.; 2016; 127, pp. 204-213. [DOI: https://dx.doi.org/10.1016/j.jclepro.2016.04.054]

6. Schaefer, C.O.; Cheriaf, M.; Rocha, J.C. Production of Synthetic Phosphoanhydrite and Its Use as a Binder in Self-Leveling Underlayments (SLU). Materials; 2017; 10, 958. [DOI: https://dx.doi.org/10.3390/ma10080958]

7. Gutiérrez-González, S.; Alonso, M.M.; Gadea, J.; Rodríguez, A.; Calderón, V. Rheological behaviour of gypsum plaster pastes with polyamide powder wastes. Constr. Build. Mater.; 2013; 38, pp. 407-412. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2012.08.034]

8. Aranda, B.; Guillou, O.; Lanos, C.; Daiguebonne, C.; Freslon, S.; Tessier, C.; Laurans, M.; Baux, C. Effect of multiphasic structure of binder particles on the mechanical properties of a gypsum-based material. Constr. Build. Mater.; 2016; 102, pp. 175-181. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2015.10.171]

9. Arikan, M.; Sobolev, K. The optimization of a gypsum-based composite material. Cem. Concr. Res.; 2002; 32, pp. 1725-1728. [DOI: https://dx.doi.org/10.1016/S0008-8846(02)00858-X]

10. Zhang, S.; Xu, X.; Memon, S.A.; Dong, Z.; Li, D.; Cui, H. Effect of calcium sulfate type and dosage on properties of calcium aluminate cement-based self-leveling mortar. Constr. Build. Mater.; 2018; 167, pp. 253-262. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2018.01.146]

11. Xu, L.; Li, N.; Wang, R.; Wang, P. A comprehensive study on the relationship between mechanical properties and microstructural development of calcium sulfoaluminate cement based self-leveling underlayments. Constr. Build. Mater.; 2018; 163, pp. 225-234. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2017.12.089]

12. Yang, J.; Liu, L.; Liao, Q.; Wu, J.; Li, J.; Zhang, L. Effect of superabsorbent polymers on the drying and autogenous shrinkage properties of self-leveling mortar. Constr. Build. Mater.; 2019; 201, pp. 401-407. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2018.12.197]

13. Wang, Y.; Wu, J.; Su, L.; Zhang, Z.; Wang, Z.; Lei, T.; Lu, X.; Ye, Z. Effect of Chemical Admixtures on the Working Performance and Mechanical Properties of Cement-Based Self-Leveling Mortar. Buildings; 2023; 13, 2248. [DOI: https://dx.doi.org/10.3390/buildings13092248]

14. Ge, H.; Sun, Z.; Lu, Z.; Yang, H.; Zhang, T.; He, N. Influence and mechanism analysis of different types of water reducing agents on volume shrinkage of cement mortar. J. Build. Eng.; 2024; 82, 108204. [DOI: https://dx.doi.org/10.1016/j.jobe.2023.108204]

15. Patural, L.; Marchal, P.; Govin, A.; Grosseau, P.; Ruot, B.; Devès, O. Cellulose ethers influence on water retention and consistency in cement-based mortars. Cem. Concr. Res.; 2011; 41, pp. 46-55. [DOI: https://dx.doi.org/10.1016/j.cemconres.2010.09.004]

16. Li, N.; Xu, L.; Wang, R.; Li, L.; Wang, P. Experimental study of calcium sulfoaluminate cement-based self-leveling compound exposed to various temperatures and moisture conditions: Hydration mechanism and mortar properties. Cem. Concr. Res.; 2018; 108, pp. 103-115. [DOI: https://dx.doi.org/10.1016/j.cemconres.2018.03.012]

17. Şahmaran, M.; Christianto, H.A.; Yaman, İ.Ö. The effect of chemical admixtures and mineral additives on the properties of self-compacting mortars. Cem. Concr. Compos.; 2006; 28, pp. 432-440. [DOI: https://dx.doi.org/10.1016/j.cemconcomp.2005.12.003]

18. Pan, J.; Feng, K.; Wang, P.; Chen, H.; Yang, W. Retardation and compressive strength enhancement effect of upcycling waste carrot as bio-admixture for cement mortars. J. Build. Eng.; 2022; 62, 105402. [DOI: https://dx.doi.org/10.1016/j.jobe.2022.105402]

19. Fan, L.; Xiong, S.; Wang, W.; Zhang, J.; Zeng, L. Effect of Polycarboxylate Admixture on the Performance of Fluorogypsum-Based Self-Leveling Material. Appl. Sci.; 2023; 13, 12802. [DOI: https://dx.doi.org/10.3390/app132312802]

20. Guan, Q.; Sui, Y.; Zhang, F.; Yu, W.; Bo, Y.; Wang, P.; Peng, W.; Jin, J. Preparation of α-calcium sulfate hemihydrate from industrial by-product gypsum: A review. Physicochem. Probl. Miner. Process.; 2020; 57, pp. 168-181. [DOI: https://dx.doi.org/10.37190/ppmp/130795]

21. Xiao, X.; Li, J.; Meng, Q.; Hou, X.; Liu, Y.; Wang, X.; Wang, W.; Lu, S.; Li, Y.; Mao, Y. . Reuse of by-product gypsum with solid wastes-derived sulfoaluminate cement modification for the preparation of self-leveling mortar and influence mechanism of H3PO4. Constr. Build. Mater.; 2024; 411, 134298. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2023.134298]

22. Qi, J.; Zhu, H.; Zhou, P.; Wang, X.; Wang, Z.; Yang, S.; Yang, D.; Li, B. Application of phosphogypsum in soilization: A review. Int. J. Environ. Sci. Technol.; 2023; 20, pp. 10449-10464. [DOI: https://dx.doi.org/10.1007/s13762-023-04783-2]

23. Wang, G.; Zong, H.; Zhang, Z.; Sun, J.; Wang, F.; Feng, Y.; Huang, S.; Li, Q. Application of titanium gypsum as raw materials in cement-based self-leveling mortars. Case Stud. Constr. Mater.; 2023; 19, e02536. [DOI: https://dx.doi.org/10.1016/j.cscm.2023.e02536]

24. Silva, D.B.P.; Lima, N.B.; Lima, V.M.E.; Estolano, A.M.L.; Nascimento, H.C.B.; Vilemen, P.; Padron-Hernández, E.; Carneiro, A.M.P.; Lima, N.B.D.; Povoas, Y.V. Producing a gypsum-based self-leveling mortar for subfloor modified by polycarboxylate admixture (PCE). Constr. Build. Mater.; 2023; 364, 130007. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2022.130007]

25. Halicka, A.; Ogrodnik, P.; Zegardlo, B. Using ceramic sanitary ware waste as concrete aggregate. Constr. Build. Mater.; 2013; 48, pp. 295-305. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2013.06.063]

26. Gruber, E.T.; Effting, C.; Schackow, A.; Mendes, G.A. Performance evaluation of self-leveling mortars using phosphogypsum and white ceramic waste. Rev. IBRACON Estrut. Mater.; 2024; 17, e17103. [DOI: https://dx.doi.org/10.1590/s1983-41952024000100003]

27. Safi, B.; Saidi, M.; Aboutaleb, D.; Maallem, M. The use of plastic waste as fine aggregate in the self-compacting mortars: Effect on physical and mechanical properties. Constr. Build. Mater.; 2013; 43, pp. 436-442. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2013.02.049]

28.ISO 9597:2008 Cement—Test Methods—Determination of Setting Time and Soundness; International Organization for Standardization: Geneva, Switzerland, 2008; pp. 1-10. Available online: https://www.iso.org/standard/45571.html (accessed on 13 September 2024).

29.ISO 679:2009 Cement—Test Methods—Determination of Strength; International Organization for Standardization: Geneva, Switzerland, 2009; pp. 6-11. Available online: https://www.iso.org/standard/45568.html (accessed on 13 September 2024).

30.ISO 13007-2:2013 Ceramic Tiles—Grouts and Adhesives—Part 2: Test Methods for Adhesives; International Organization for Standardization: Geneva, Switzerland, 2013; pp. 1-21. Available online: https://www.iso.org/standard/60881.html (accessed on 13 September 2024).

31.ISO 10545-6:2010 Ceramic Tiles—Part 6: Determination of Resistance to Deep Abrasion for Unglazed Tiles; International Organization for Standardization: Geneva, Switzerland, 2010; pp. 1-3. Available online: https://www.iso.org/standard/51089.html (accessed on 13 September 2024).

32.JGJ/T 70-2009 Standard for Test Method of Performance on Building Mortar; Ministry of Housing and Urban-Rural Development of the People’s Republic of China: Beijing, China, 2009; pp. 11-12. Available online: https://www.ebiaozhun.com/std/e548168f81d340d7b335fa9ffb4ee28a.html (accessed on 7 September 2024).

33. Silva, D.B.P.D.; Pontes, I.D.O.C.; Rodrigues, M.T.J.; Lima, N.B.D.; Póvoas, Y.V. Pasta autonivelante de gesso para utilização como camada de contrapiso. Ambiente Construído; 2021; 21, pp. 311-329. [DOI: https://dx.doi.org/10.1590/s1678-86212021000200528]

34. Padilla, A.; Panama, I.; Toledo, A.; Flores, A. Development of low weight self-levelling mortars. J. Phys. Conf. Ser.; 2015; 582, 012030. [DOI: https://dx.doi.org/10.1088/1742-6596/582/1/012030]

35. Ma, Y.; Jin, M.; Wang, F.; Jacques, D.; Shen, X.; Zhang, J.; Gao, C.; Zeng, H.; Liu, J.; Liu, J. Heating-induced transformations in calcium silicate hydrate (C-S-H): In-situ investigations of composition, structure, and morphology. Cem. Concr. Res.; 2025; 190, 107819. [DOI: https://dx.doi.org/10.1016/j.cemconres.2025.107819]

36. Scolaro, T.P.; Rocha, J.C. Influence of the physical characteristics of sand and the crushed filler content on the properties of self-leveling mortars. Cerâmica; 2021; 67, pp. 179-187. [DOI: https://dx.doi.org/10.1590/0366-69132021673823070]

37. Zeng, L.; Zhu, J.; Ye, J.; Cai, W.; Zhang, J.; Wang, S. Study on the influence mechanism of water reducing agent on the properties of anhydrite-based self-leveling mortar. Case Stud. Constr. Mater.; 2023; 19, e02308. [DOI: https://dx.doi.org/10.1016/j.cscm.2023.e02308]

38. Tran, T.Q.; Kim, Y.-S.; Dang, L.C.; Do, T.M. A state-of-the-art review on the utilization of new green binders in the production of controlled low-strength materials. Constr. Build. Mater.; 2023; 393, 132078. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2023.132078]

39. Sharp, J.H.; Lawrence, C.D.; Yang, R. Calcium sulfoaluminate cements—Low-energy cements, special cements or what?. Adv. Cem. Res.; 1999; 11, pp. 3-13. [DOI: https://dx.doi.org/10.1680/adcr.1999.11.1.3]

40. Gartner, E. Industrially interesting approaches to “low-CO2” cements. Cem. Concr. Res.; 2004; 34, pp. 1489-1498. [DOI: https://dx.doi.org/10.1016/j.cemconres.2004.01.021]

41. Damtoft, J.S.; Lukasik, J.; Herfort, D.; Sorrentino, D.; Gartner, E.M. Sustainable development and climate change initiatives. Cem. Concr. Res.; 2008; 38, pp. 115-127. [DOI: https://dx.doi.org/10.1016/j.cemconres.2007.09.008]

42. Gartner, E.M.; Macphee, D.E. A physico-chemical basis for novel cementitious binders. Cem. Concr. Res.; 2011; 41, pp. 736-749. [DOI: https://dx.doi.org/10.1016/j.cemconres.2011.03.006]

43. Juenger, M.C.G.; Winnefeld, F.; Provis, J.L.; Ideker, J.H. Advances in alternative cementitious binders. Cem. Concr. Res.; 2011; 41, pp. 1232-1243. [DOI: https://dx.doi.org/10.1016/j.cemconres.2010.11.012]

44. He, X.; Fang, Y.; Peng, Y.; Shen, W.; Qiao, D.; Wang, M. Mortar’s rheological property and workability investigation based on morphology impact factor for graded sand particles. Constr. Build. Mater.; 2022; 328, 126987. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2022.126987]

45. Zhang, D.; Zhang, S.; Yang, Q. Effect of Replacing Fine Aggregate with Fly Ash on the Performance of Mortar. Materials; 2023; 16, 4292. [DOI: https://dx.doi.org/10.3390/ma16124292]

46. Canbaz, M.; Topçu, İ.B.; Ateşin, Ö. Effect of admixture ratio and aggregate type on self-leveling screed properties. Constr. Build. Mater.; 2016; 116, pp. 321-325. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2016.04.084]

47. Zhang, J.; Jin, C.; Wang, B.; Han, J.; Guo, L.; Tang, N. Study on the micro-rheological properties of fly ash-based cement mortar. Constr. Build. Mater.; 2024; 442, 137664. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2024.137664]

48. Mao, Y.; Wu, H.; Wang, W.; Jia, M.; Che, X. Pretreatment of municipal solid waste incineration fly ash and preparation of solid waste source sulphoaluminate cementitious material. J. Hazard. Mater.; 2020; 385, 121580. [DOI: https://dx.doi.org/10.1016/j.jhazmat.2019.121580] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/31740310]

49. Du, C.; Jiang, X.; Wang, L.; Yi, F.; Niu, B. Experimental study on dynamic characteristics of tailings under different consolidation conditions. Sci. Rep.; 2024; 14, 735. [DOI: https://dx.doi.org/10.1038/s41598-023-42532-0] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/38184637]

50. Cheng, X.; Tian, W.; Gao, J.; Gao, Y. Performance evaluation and lifetime prediction of steel slag coarse aggregate concrete under sulfate attack. Constr. Build. Mater.; 2022; 344, 128203. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2022.128203]

51. López-Uceda, A.; Cantador-Fernández, D.; Da Silva, P.R.; de Brito, J.; Fernández-Rodríguez, J.M.; Jiménez, J.R. Mechanical and durability performance of self-compacting mortars made with different industrial by-products as fillers. Constr. Build. Mater.; 2024; 431, 136536. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2024.136536]

52. Dong, C.R.; Zhang, Q.Y.; Chen, C.; Jiang, T.X.; Guo, Z.G.; Liu, Y.; Lin, S.L. Fresh and hardened properties of recycled plastic fiber reinforced self-compacting concrete made with recycled concrete aggregate and fly ash, slag, silica fume. J. Build. Eng.; 2022; 62, 105384. [DOI: https://dx.doi.org/10.1016/j.jobe.2022.105384]

53. Zheng, D.D.; Ji, T.; Wang, C.Q.; Sun, C.J.; Lin, X.J.; Hossain, K.M.A. Effect of the combination of fly ash and silica fume on water resistance of Magnesium-Potassium Phosphate Cement. Constr. Build. Mater.; 2016; 106, pp. 415-421. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2015.12.085]

54. Su, N.; Hsu, K.-C.; Chai, H.-W. A simple mix design method for self-compacting concrete. Cem. Concr. Res.; 2001; 31, pp. 1799-1807. [DOI: https://dx.doi.org/10.1016/S0008-8846(01)00566-X]

55. Esping, O. Effect of limestone filler BET(H2O)-area on the fresh and hardened properties of self-compacting concrete. Cem. Concr. Res.; 2008; 38, pp. 938-944. [DOI: https://dx.doi.org/10.1016/j.cemconres.2008.03.010]

56. Avet, F.; Li, X.; Scrivener, K. Determination of the amount of reacted metakaolin in calcined clay blends. Cem. Concr. Res.; 2018; 106, pp. 40-48. [DOI: https://dx.doi.org/10.1016/j.cemconres.2018.01.009]

57. Navrátilová, E.; Rovnaníková, P. Pozzolanic properties of brick powders and their effect on the properties of modified lime mortars. Constr. Build. Mater.; 2016; 120, pp. 530-539. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2016.05.062]

58. Zhao, Z.; Grellier, A.; El Karim Bouarroudj, M.; Michel, F.; Bulteel, D.; Courard, L. Substitution of limestone filler by waste brick powder in self-compacting mortars: Properties and durability. J. Build. Eng.; 2021; 43, 102898. [DOI: https://dx.doi.org/10.1016/j.jobe.2021.102898]

59. Rizwan, S.A.; Bier, T.A. Blends of limestone powder and fly-ash enhance the response of self-compacting mortars. Constr. Build. Mater.; 2012; 27, pp. 398-403. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2011.07.030]

60. Xu, H.; Chen, F.J.; Tao, H.Y.; He, Y.F.; Zhai, W.Q.; Zhang, J.P.; He, Z.H. Effect of limestone powder on properties of self-leveling mortar. Mater. Express; 2023; 13, pp. 1790-1798. [DOI: https://dx.doi.org/10.1166/mex.2023.2523]

61. Schönlein, M.; Plank, J. Influence of PCE kind and dosage on ettringite crystallization performed under terrestrial and microgravity conditions. J. Am. Ceram. Soc.; 2018; 101, pp. 3575-3584. [DOI: https://dx.doi.org/10.1111/jace.15513]

62. Zhang, L.; Miao, X.; Kong, X.; Zhou, S. Retardation effect of PCE superplasticizers with different architectures and their impacts on early strength of cement mortar. Cem. Concr. Compos.; 2019; 104, 103369. [DOI: https://dx.doi.org/10.1016/j.cemconcomp.2019.103369]

63. Yoshioka, K.; Tazawa, E.-i.; Kawai, K.; Enohata, T. Adsorption characteristics of superplasticizers on cement component minerals. Cem. Concr. Res.; 2002; 32, pp. 1507-1513. [DOI: https://dx.doi.org/10.1016/S0008-8846(02)00782-2]

64. Uchikawa, H.; Hanehara, S.; Sawaki, D. The role of steric repulsive force in the dispersion of cement particles in fresh paste prepared with organic admixture. Cem. Concr. Res.; 1997; 27, pp. 37-50. [DOI: https://dx.doi.org/10.1016/S0008-8846(96)00207-4]

65. Flatt, R.J.; Houst, Y.F. A simplified view on chemical effects perturbing the action of superplasticizers. Cem. Concr. Res.; 2001; 31, pp. 1169-1176. [DOI: https://dx.doi.org/10.1016/S0008-8846(01)00534-8]

66. Dalas, F.; Nonat, A.; Pourchet, S.; Mosquet, M.; Rinaldi, D.; Sabio, S. Tailoring the anionic function and the side chains of comb-like superplasticizers to improve their adsorption. Cem. Concr. Res.; 2015; 67, pp. 21-30. [DOI: https://dx.doi.org/10.1016/j.cemconres.2014.07.024]

67. Chuang, P.-H.; Tseng, Y.-H.; Fang, Y.; Gui, M.; Ma, X.; Luo, J. Effect of Side Chain Length on Polycarboxylate Superplasticizer in Aqueous Solution: A Computational Study. Polymers; 2019; 11, 346. [DOI: https://dx.doi.org/10.3390/polym11020346] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/30960330]

68. Liu, M.; Gao, Y.; Zhang, L.; Jiang, G.; Zeng, C.; Wang, P. The application of thermal analysis to study the hydration behavior of tricalcium aluminate-gypsum in the presence of polycarboxylate-based superplasticizers. Thermochim. Acta; 2021; 696, 178821. [DOI: https://dx.doi.org/10.1016/j.tca.2020.178821]

69. Li, J.; Wang, R.; Li, L. Influence of cellulose ethers structure on mechanical strength of calcium sulphoaluminate cement mortar. Constr. Build. Mater.; 2021; 303, 124514. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2021.124514]

70. Li, Q.; Wang, B.; Wei, Z.; Zhong, Y. Experiment and numerical simulation study of polycarboxylate superplasticizer modified cemented ultrafine tailings filling slurry: Rheology, fluidity, and flow properties in pipeline. Constr. Build. Mater.; 2024; 438, 137041. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2024.137041]

71. Basha, S.I.; Aziz, M.A.; Ahmad, S.; Al-Zahrani, M.M.; Shameem, M.; Maslehuddin, M. Improvement of concrete durability using nanocomposite coating prepared by mixing epoxy coating with Submicron/Nano-carbon obtained from heavy fuel oil ash. Constr. Build. Mater.; 2022; 325, 126812. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2022.126812]

72. Miao, J.; Lu, L.; Jiang, J. Reinforcement of ultra-low dosage of polycarboxylate ether (PCE) grafted nano-silica sol to the mechanical and durable properties of cement mortar. J. Mater. Res. Technol.; 2022; 19, pp. 3646-3657. [DOI: https://dx.doi.org/10.1016/j.jmrt.2022.06.087]

73. Peng, J.; Qu, J.; Zhang, J.; Chen, M.; Wan, T. Adsorption characteristics of water-reducing agents on gypsum surface and its effect on the rheology of gypsum plaster. Cem. Concr. Res.; 2005; 35, pp. 527-531. [DOI: https://dx.doi.org/10.1016/j.cemconres.2004.04.016]

74. Qian, S.; Yao, Y.; Wang, Z.; Cui, S.; Liu, X.; Jiang, H.; Guo, Z.; Lai, G.; Xu, Q.; Guan, J. Synthesis, characterization and working mechanism of a novel polycarboxylate superplasticizer for concrete possessing reduced viscosity. Constr. Build. Mater.; 2018; 169, pp. 452-461. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2018.02.212]

75. Uchikawa, H.; Hanehara, S.; Shirasaka, T.; Sawaki, D. Effect of admixture on hydration of cement, adsorptive behavior of admixture and fluidity and setting of fresh cement paste. Cem. Concr. Res.; 1992; 22, pp. 1115-1129. [DOI: https://dx.doi.org/10.1016/0008-8846(92)90041-S]

76. Jansen, D.; Neubauer, J.; Goetz-Neunhoeffer, F.; Haerzschel, R.; Hergeth, W.D. Change in reaction kinetics of a Portland cement caused by a superplasticizer—Calculation of heat flow curves from XRD data. Cem. Concr. Res.; 2012; 42, pp. 327-332. [DOI: https://dx.doi.org/10.1016/j.cemconres.2011.10.005]

77. Zhang, Y.-R.; Kong, X.-M.; Lu, Z.-B.; Lu, Z.-C.; Hou, S.-S. Effects of the charge characteristics of polycarboxylate superplasticizers on the adsorption and the retardation in cement pastes. Cem. Concr. Res.; 2015; 67, pp. 184-196. [DOI: https://dx.doi.org/10.1016/j.cemconres.2014.10.004]

78. Cheung, J.; Jeknavorian, A.; Roberts, L.; Silva, D. Impact of admixtures on the hydration kinetics of Portland cement. Cem. Concr. Res.; 2011; 41, pp. 1289-1309. [DOI: https://dx.doi.org/10.1016/j.cemconres.2011.03.005]

79. Pourchez, J.; Peschard, A.; Grosseau, P.; Guyonnet, R.; Guilhot, B.; Vallée, F. HPMC and HEMC influence on cement hydration. Cem. Concr. Res.; 2006; 36, pp. 288-294. [DOI: https://dx.doi.org/10.1016/j.cemconres.2005.08.003]

80. Nguyen, D.D.; Devlin, L.P.; Koshy, P.; Sorrell, C.C. Impact of water-soluble cellulose ethers on polymer-modified mortars. J. Mater. Sci.; 2013; 49, pp. 923-951. [DOI: https://dx.doi.org/10.1007/s10853-013-7732-8]

81. Pourchez, J.; Ruot, B.; Debayle, J.; Pourchez, E.; Grosseau, P. Some aspects of cellulose ethers influence on water transport and porous structure of cement-based materials. Cem. Concr. Res.; 2010; 40, pp. 242-252. [DOI: https://dx.doi.org/10.1016/j.cemconres.2009.09.028]

82. Li, J.; Wang, R.; Xu, Y. Influence of cellulose ethers chemistry and substitution degree on the setting and early-stage hydration of calcium sulphoaluminate cement. Constr. Build. Mater.; 2022; 344, 128266. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2022.128266]

83. Bülichen, D.; Kainz, J.; Plank, J. Working mechanism of methyl hydroxyethyl cellulose (MHEC) as water retention agent. Cem. Concr. Res.; 2012; 42, pp. 953-959. [DOI: https://dx.doi.org/10.1016/j.cemconres.2012.03.016]

84. Brumaud, C.; Bessaies-Bey, H.; Mohler, C.; Baumann, R.; Schmitz, M.; Radler, M.; Roussel, N. Cellulose ethers and water retention. Cem. Concr. Res.; 2013; 53, pp. 176-184. [DOI: https://dx.doi.org/10.1016/j.cemconres.2013.06.010]

85. Bülichen, D.; Plank, J. Mechanistic study on carboxymethyl hydroxyethyl cellulose as fluid loss control additive in oil well cement. J. Appl. Polym. Sci.; 2012; 124, pp. 2340-2347. [DOI: https://dx.doi.org/10.1002/app.35278]

86. Chen, N.; Wang, P.; Zhao, L.; Zhang, G. Water Retention Mechanism of HPMC in Cement Mortar. Materials; 2020; 13, 2918. [DOI: https://dx.doi.org/10.3390/ma13132918]

87. Xu, L.; Ou, Y.; Hecker, A.; Rößler, C.; Ludwig, H.M.; Yang, Z.; Wu, K. State of water in calcium sulfoaluminate cement paste modified by hydroxyethyl methyl cellulose ether. J. Build. Eng.; 2021; 43, 102894. [DOI: https://dx.doi.org/10.1016/j.jobe.2021.102894]

88. Zhou, S.-C.; Lv, H.-L.; Li, N.; Zhang, J. Effects of Chemical Admixtures on the Working and Mechanical Properties of Ordinary Dry-Mixed Mortar. Adv. Mater. Sci. Eng.; 2019; 2019, 5978089. [DOI: https://dx.doi.org/10.1155/2019/5978089]

89. You Seok, K.; Ho-Jong, K. Effect of Cellulose Based Water Retention Additives on Mechanical Properties of Cement Based Mortar. Polymer; 2015; 39, pp. 820-826. [DOI: https://dx.doi.org/10.7317/pk.2015.39.5.820]

90. Pourchez, J.; Grosseau, P.; Ruot, B. Changes in C3S hydration in the presence of cellulose ethers. Cem. Concr. Res.; 2010; 40, pp. 179-188. [DOI: https://dx.doi.org/10.1016/j.cemconres.2009.10.008]

91. Ou, Z.H.; Ma, B.G.; Jian, S.W. Influence of cellulose ethers molecular parameters on hydration kinetics of Portland cement at early ages. Constr. Build. Mater.; 2012; 33, pp. 78-83. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2012.01.007]

92. Knapen, E.; Van Gemert, D. Cement hydration and microstructure formation in the presence of water-soluble polymers. Cem. Concr. Res.; 2009; 39, pp. 6-13. [DOI: https://dx.doi.org/10.1016/j.cemconres.2008.10.003]

93. Huang, G.; Zhao, J.; Gupta, R.; Liu, W.V. Influence of tartaric acid dosage on the early-age and long-term properties of calcium sulfoaluminate belite cement composites. Constr. Build. Mater.; 2022; 356, 129257. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2022.129257]

94. Sun, F.; Pang, X.; Kawashima, S.; Cheng, G.; Guo, S.; Bu, Y. Effect of tartaric acid on the hydration of oil well cement at elevated temperatures between 60 °C and 89 °C. Cem. Concr. Res.; 2022; 161, 106952. [DOI: https://dx.doi.org/10.1016/j.cemconres.2022.106952]

95. Guan, B.; Tian, H.; Ding, D.; Wu, J.; Xiong, R.; Xu, A.; Chen, H. Effect of Citric Acid on the Time-Dependent Rheological Properties of Magnesium Oxychloride Cement. J. Mater. Civ. Eng.; 2018; 30, 04018275. [DOI: https://dx.doi.org/10.1061/(ASCE)MT.1943-5533.0002451]

96. Coppola, L.; Coffetti, D.; Crotti, E. Use of tartaric acid for the production of sustainable Portland-free CSA-based mortars. Constr. Build. Mater.; 2018; 171, pp. 243-249. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2018.03.137]

97. Telesca, A.; Marroccoli, M.; Coppola, L.; Coffetti, D.; Candamano, S. Tartaric acid effects on hydration development and physico-mechanical properties of blended calcium sulphoaluminate cements. Cem. Concr. Compos.; 2021; 124, 104275. [DOI: https://dx.doi.org/10.1016/j.cemconcomp.2021.104275]

98. Zou, D.; Zhang, Z.; Wang, D. Influence of citric acid and sodium gluconate on hydration of calcium sulfoaluminate cement at various temperatures. Constr. Build. Mater.; 2020; 263, 120247. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2020.120247]

99. Burris, L.E.; Kurtis, K.E. Influence of set retarding admixtures on calcium sulfoaluminate cement hydration and property development. Cem. Concr. Res.; 2018; 104, pp. 105-113. [DOI: https://dx.doi.org/10.1016/j.cemconres.2017.11.005]

100. Belhadi, R.; Govin, A.; Grosseau, P. Influence of polycarboxylate superplasticizer, citric acid and their combination on the hydration and workability of calcium sulfoaluminate cement. Cem. Concr. Res.; 2021; 147, 106513. [DOI: https://dx.doi.org/10.1016/j.cemconres.2021.106513]

101. Lim, H.M.; Yang, H.C.; Chun, B.S.; Lee, S.H. The Effect of Sodium Tripolyphosphate on Sodium Silicate-Cement Grout. Mater. Sci. Forum; 2005; 486–487, pp. 391-394. [DOI: https://dx.doi.org/10.4028/www.scientific.net/MSF.486-487.391]

102. Rashad, A.M.; Gharieb, M. Impact of long-term natural weathering on the properties of alkali-activated fly ash mortars modified with silica fume and sodium tripolyphosphate. Constr. Build. Mater.; 2023; 405, 133354. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2023.133354]

103. Kastiukas, G.; Zhou, X.; Castro-Gomes, J.; Huang, S.; Saafi, M. Effects of lactic and citric acid on early-age engineering properties of Portland/calcium aluminate blended cements. Constr. Build. Mater.; 2015; 101, pp. 389-395. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2015.10.054]

104. Ding, X.; Huang, W.; Li, Y.; Hu, Z.; Shan, Z. Study on retarding feature and retardation mechanism of various retarding materials on gypsum as a construction material: A review. J. Build. Eng.; 2023; 72, 106569. [DOI: https://dx.doi.org/10.1016/j.jobe.2023.106569]

105. Ding, X.; Wei, B.; Deng, M.; Chen, H.; Shan, Z. Effect of protein peptides with different molecular weights on the setting and hydration process of gypsum. Constr. Build. Mater.; 2022; 318, 126185. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2021.126185]

106. Ding, X.; Ye, B.; Dai, R.; Chen, H.; Shan, Z. A graft copolymer of collagen hydrolysate obtained from chrome leather scraps for retardation in Portland cement. J. Clean. Prod.; 2021; 284, 125408. [DOI: https://dx.doi.org/10.1016/j.jclepro.2020.125408]

107. Yalcin, D.; Ozcalik, O.; Altiok, E.; Bayraktar, O. Characterization and recovery of tartaric acid from wastes of wine and grape juice industries. J. Therm. Anal. Calorim.; 2008; 94, pp. 767-771. [DOI: https://dx.doi.org/10.1007/s10973-008-9345-z]

108. Nurgel, C.; Canbas, A. Production of Tartaric Acid From Pomace of Some Anatolian Grape Cultivars. Am. J. Enol. Vitic.; 1998; 49, pp. 95-99. [DOI: https://dx.doi.org/10.5344/ajev.1998.49.1.95]

109. Bishop, M.; Barron, A.R. Cement Hydration Inhibition with Sucrose, Tartaric Acid, and Lignosulfonate:  Analytical and Spectroscopic Study. Ind. Eng. Chem. Res.; 2006; 45, pp. 7042-7049. [DOI: https://dx.doi.org/10.1021/ie060806t]

110. Plank, J.; Winter, C. Competitive adsorption between superplasticizer and retarder molecules on mineral binder surface. Cem. Concr. Res.; 2008; 38, pp. 599-605. [DOI: https://dx.doi.org/10.1016/j.cemconres.2007.12.003]

111. Ltifi, M.; Guefrech, A.; Mounanga, P. Effects of sodium tripolyphosphate on the rheology and hydration rate of Portland cement pastes. Adv. Cem. Res.; 2012; 24, pp. 325-335. [DOI: https://dx.doi.org/10.1680/adcr.11.00028]

112. Cheng, B.; Feng, H.; Armia, E.; Guo, H.; Zhang, S.; Zhang, H. Effects of Sodium Tripolyphosphate Addition on the Dispersion and Hydration of Pure Calcium Aluminate Cement. Materials; 2023; 16, 3141. [DOI: https://dx.doi.org/10.3390/ma16083141]

113. Liu, C.; Jia, Y.M. Effect of Redispersible Latex Powder and Fly Ash on Properties of Mortar. Coatings; 2022; 12, 1930. [DOI: https://dx.doi.org/10.3390/coatings12121930]

114. Wang, S.; Zhang, G.; Wang, Z.; Huang, T.; Wang, P. Effect of defoaming agent on the properties of cement mortars with hydroxyethyl methyl cellulose through adjusting air content gradient. Cem. Concr. Compos.; 2023; 139, 105024. [DOI: https://dx.doi.org/10.1016/j.cemconcomp.2023.105024]

115. Ping, Z.; Ming, L.; Chi, Z.; Xiujian, X.; Yongjin, Y.; Fengzhong, Q.; Yuanpeng, W. Ultra-high temperature suspending stabilizer and cement slurry interface interaction law and mechanism study for ultra-deep well cementing. Constr. Build. Mater.; 2023; 409, 133979. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2023.133979]

116. Oliveira, T.V.; Cordeiro, L.D.P.; Bessa, S.A.L. Experimental study of self-leveling mortars produced with recycled concrete aggregates. Case Stud. Constr. Mater.; 2022; 17, e01294. [DOI: https://dx.doi.org/10.1016/j.cscm.2022.e01294]

117. Yu, Z.Y.; Zhao, Y.D.; Ba, H.J.; Liu, M.H. Synergistic effects of ettringite-based expansive agent and polypropylene fiber on early-age anti-shrinkage and anti-cracking properties of mortars. J. Build. Eng.; 2021; 39, 102275. [DOI: https://dx.doi.org/10.1016/j.jobe.2021.102275]

118. Zhao, W.H.; Ji, X.P.; Jiang, Y.Q.; Pan, T.H. Effect of C-S-H Nucleating Agent on Cement Hydration. Appl. Sci.; 2021; 11, 6638. [DOI: https://dx.doi.org/10.3390/app11146638]

119. Manh Do, T.; Kang, G.-O.; Kim, Y.-S. Development of a new cementless binder for controlled low strength material (CLSM) using entirely by-products. Constr. Build. Mater.; 2019; 206, pp. 576-589. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2019.02.088]

120. Zhi, Z.; Ma, B.; Tan, H.; Guo, Y.; Jin, Z.; Yu, H.; Jian, S. Effect of Competitive Adsorption between Polycarboxylate Superplasticizer and Hydroxypropylmethyl Cellulose on Rheology of Gypsum Paste. J. Mater. Civ. Eng.; 2018; 30, 04018141. [DOI: https://dx.doi.org/10.1061/(ASCE)MT.1943-5533.0002346]

121. Zha, F.; Qiao, B.; Kang, B.; Xu, L.; Chu, C.; Yang, C. Engineering properties of expansive soil stabilized by physically amended titanium gypsum. Constr. Build. Mater.; 2021; 303, 124456. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2021.124456]

122. Yuan, H.; Chen, S. Effects of titanium gypsum on high calcium fly ash system: Physical and microscopic properties, hydration, and Fe transformation. J. Build. Eng.; 2023; 78, 107653. [DOI: https://dx.doi.org/10.1016/j.jobe.2023.107653]

123. Li, X.-Y.; Yang, J.-Y. Production, characterisation, and application of titanium gypsum: A review. Process Saf. Environ. Prot.; 2024; 181, pp. 64-74. [DOI: https://dx.doi.org/10.1016/j.psep.2023.11.008]

124. Du, J.; Tian, L.; Qi, M.; Zhang, C.; Di, H.; Zhi, X.; Zhu, J. Revealing maleic acid role in the preparation of α-hemihydrate gypsum from titanium gypsum through experiments and DFT calculations. Sci. Total Environ.; 2023; 897, 166405. [DOI: https://dx.doi.org/10.1016/j.scitotenv.2023.166405]

125. Huang, K.; Cai, G.; Yan, C.; Yu, J.; Tang, L.; Zhang, J. Strength and microstructure characteristics of red-bed weathered residual soil stabilized by Titanium Gypsum-Cement. Constr. Build. Mater.; 2023; 403, 133071. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2023.133071]

126. Pereira, V.M.; Camarini, G. Fresh and Hardened Properties of Self-Leveling Mortars with Porcelain and Red Ceramic Wastes. Adv. Civ. Eng.; 2018; 2018, 6378643. [DOI: https://dx.doi.org/10.1155/2018/6378643]

127. Wang, Q.; Jia, R.Q. A novel gypsum-based self-leveling mortar produced by phosphorus building gypsum. Constr. Build. Mater.; 2019; 226, pp. 11-20. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2019.07.289]

128. Anjos, M.A.S.; Araújo, T.R.; Ferreira, R.L.S.; Farias, E.C.; Martinelli, A.E. Properties of self-leveling mortars incorporating a high-volume of sugar cane bagasse ash as partial Portland cement replacement. J. Build. Eng.; 2020; 32, 101694. [DOI: https://dx.doi.org/10.1016/j.jobe.2020.101694]

129. Barluenga, G.; Hernández-Olivares, F. Self-levelling cement mortar containing grounded slate from quarrying waste. Constr. Build. Mater.; 2010; 24, pp. 1601-1607. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2010.02.033]

130. Schiefer, C.; Plank, J. Mechanochemical syngenite as hydration accelerator for anhydrite-based self-levelling floor screeds. Constr. Build. Mater.; 2021; 308, 124982. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2021.124982]

131. Mendes, G.A.; Effting, C.; Schackow, A. Argamassa autonivelante com adição de resíduos de mármorese granitos: Propriedades físicase mecânicas. Ambiente Construído; 2020; 20, pp. 403-418. [DOI: https://dx.doi.org/10.1590/s1678-86212020000300436]

132. Li, B.; Wang, C.-Q.; Huang, H.-S. Red mud modified phosphogypsum based self-leveling mortar: Hydration mechanism, heavy metal migration law and spatial distribution characteristics. Constr. Build. Mater.; 2024; 426, 136071. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2024.136071]

Word count: 12035

Show less

© 2025 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.

Abstract

Cement-based self-leveling mortar (CSL) is a special building material that utilizes cement as the main cementitious component, combined with a variety of admixtures. Its self-leveling characteristics enable it to effectively level and fill uneven surfaces. Additionally, the innovative green CSL developed from industrial by-products can further enhance both environmental and economic benefits. This paper systematically reviews the use of admixtures and industrial by-products in the production of CSL. The main findings include the following: (i) compared to the international ISO standard, China’s standard JC/T 985 provides more detailed testing parameters regarding fluidity, mechanical properties, and shrinkage; (ii) the effect of additives on CSL is affected by its molecular weight and structure, and high molecular weight improving the workability of the additives; (iii) industrial by-products have been effectively incorporated into CSL, leading to a reduction in reduced greenhouse gas emissions and a decreased environmental impact; (iv) macro and microanalysis results of different green CSLs show that industrial by-product gypsum has the greatest potential for application in CSL. Based on these findings, this paper offers valuable reference data for the use of admixtures and industrial by-products in CSL. Furthermore, it contributes innovatively to the sustainable development of infrastructure construction.

Details

Title
Advances in the Application and Mechanism of Admixtures and Industrial By-Products in Cement-Based Self-Leveling Mortar: A Comprehensive Review
Author
Zong Meirong 1 ; Ma Haozhe 1 ; Xiancui, Yan 1 ; Zhu Pinghua 1 ; Wang, Wenhao 1 ; Liu, Hui 1   VIAFID ORCID Logo  ; Dong Faqin 2 ; Hua Minqi 3   VIAFID ORCID Logo 

1  Department of Civil Engineering, Changzhou University, Changzhou 213164, China; [email protected] (H.M.); [email protected] (X.Y.); [email protected] (P.Z.); [email protected] (W.W.); [email protected] (H.L.) 
2  Key Laboratory of Solid Waste Treatment and Resource Utilization, Ministry of Education, Southwest University of Science and Technology, Mianyang 621010, China; [email protected] 
3  School of Civil Engineering & Architecture, Wuhan University of Technology, Wuhan 430070, China; [email protected] 
First page
1709
Publication year
2025
Publication date
2025
Publisher
MDPI AG
e-ISSN
19961944
Source type
Scholarly Journal
Language of publication
English
DOI
https://doi.org/10.3390/ma18081709
ProQuest document ID
3194625143
Copyright
© 2025 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.