Effect of carbonated recycled aggregates on the mechanical properties and bonding performance of polyurethane mortar as a repair material

Introduction

Concrete, as the most widely used material in the construction industry, has the advantages of low cost and good overall performance [1, 2]. However, the process of concrete service will be affected by man-made factors (overloading, unreasonable transformation, etc.) and natural factors (extreme high temperature, earthquakes, etc.) to make its durability performance decline or even be destroyed, under the influence of these factors, the repair and reinforcement of concrete are imminent [3, 4]. In recent years, the repair technology of concrete has also been developing, introducing various types of fiber composites into the repair materials [5, 6].Fiber materials have better tensile properties than concrete; there is also the introduction of nanomaterials added to the repair material, the addition of nanomaterials to increase the density of its structure to achieve the purpose of increasing the bonding properties [7, 8]. The use of polymer concrete as a repair material has been widely used by mankind in concrete repair work [9]. The addition of polymers improves the performance of cementitious materials.

In recent years, the continued growth of construction and demolition activities has led to an increase in the utilization of natural resources as well as an increase in the generation of construction waste globally, with a large number of demolished buildings containing waste concrete [10, 11–12]. Production and use of traditional building materials lead to environmental pollution and depletion of natural resources [13]. Recycling of construction waste is an inevitable trend in the future, RA has been widely researched and put into use, to improve the replacement rate of RA and the number of times recycling can improve the utilization rate of renewable resources, and effectively alleviate the environmental pressure generated by the concrete industry [14]. This study investigated the strength of recycled aggregate concrete (RAC) including 3D printed concrete (3DPC) waste as recycled aggregate [15]. RA has physical properties such as high water absorption, high crushing value, high porosity, low apparent density, etc. The mechanical properties of its formulated mortar are poor, which seriously affects its working performance in the actual project. Carbonation is one of the most widely used methods to enhance the working performance of RA. CO₂ can react with the cement hydration products of recycled aggregates to generate CaCO₃...