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1. INTRODUCTION
Portland cement is used in concrete and is considered one of the most fundamental and widely produced materials for civic infrastructure projects around the world (1-4). Concrete is second to water in the total volume consumed per person, approximately three tons annually (3-4). However, cement production is a highly energy-intensive process. The manufacture of each ton of Portland cement emits approximately 0.8-1.0 ton of anthropogenic CO2 (depending on the ratio of clinker to cement) into the atmosphere (1-2,5). This represents 3-5% of current global emissions (1-3), which contribute to consequential environmental damage.
As a remedial measure, pozzolanic materials are now used as a partial substitute for Portland cement in concrete. Numerous studies show that SCBA can be used as a pozzolanic material when it is burned at temperatures between 600 and 1000oC and subjected to post-treatment such as recalcination or grinding. Results indicate that such post-treatments change some of the physical characteristics and chemical composition of the SCBA, as well as improve the pozzolanic potential (6-12). A post-treatment leads to the formation of silica, alumina (7-9,13), and especially amorphous silica (6-7). These compounds react with calcium hydroxide (CH), released during the hydration of cement, to form additional cementitious compounds such as calcium silicate hydrate (C-S-H), thus improving the microstructural properties of concrete and mortar mixtures. This could lead to an improvement of some durability properties without having negatives effects on physical and mechanical properties (6-8,11,14-16).
As previously mentioned, most research has focused on the effect of post-treatments of the SCBA in order to improve its potential activity and mechanical properties when used as a pozzolan in mortar and concrete; nevertheless, such treatments demand high levels of energy and contribute, once again, to generating contaminants. SCBA is a by-product widely available in Mexico. According to Mexico’s Union Nacional de Cañeros (National Union of Sugarcane Producers) (17), approximately 54 million tons of sugarcane are produced annually, from which some 15 million tons of bagasse are obtained. Akram et al. (18) reported that each ton of sugarcane produces approximately 0.62% of residual ash. This suggests that in Mexico approximately 0.34 million tons of SCBA are produced every year, which are mainly deposited in open garbage dumps, causing significant disposal problems and pollution.
Taking...