Due to enormous growth in industrial development, the consumption of cement is substantially increased in the recent times and the cement manufacturing industry produces annually about 1.35 billion tons of the greenhouse gas emissions which are about 7% of the total greenhouse gas emission by man‐made to the atmosphere. At the same time, the thermal power plants have been generating huge quantity of fly‐ash, which is not being recycled properly. This creates huge burden on solid waste management. Hence, to minimize the emission of CO2 from cement industry and to increase the utilization of fly‐ash, a geopolymer technology is one of the viable solutions. In terms of global warming, the geopolymer technology‐based fly‐ash activated by an alkaline activators not only have potential to significantly reduce carbon footprint of ordinary portland cement concrete, but also shows considerable promise for applications in concrete industry as an alternative binder to the Portland cement. This paper provides a brief status of fly‐ash based geopolymer paste and concrete, encapsulates, and analyses critically the most significant research findings on various properties of geopolymer concrete (GPC) over the past two decades. Also, it identifies the important factors to be considered in improving the performance of GPC at elevated temperatures as well as at ambient temperatures. Collation and analysis of more than 100 research papers in this area may provide a valuable stating document for further research.
Utilization of recycled aggregate from the construction and demolition waste as a partial substitution of natural aggregate in the concrete has been increased in the recent times in order to minimize the consumption of natural resources and the harmful effects to the environment. The present investigation mainly focuses on the influence of different fibers on mechanical and other properties of concrete made with 50% of recycled coarse aggregate (RCA) as well as concrete with 100% natural aggregate. Three types of fibers such as Woolen fibers (WF), Glass fibers (GF), and Steel fibers (SF) were used in both normal and recycled aggregate concrete mixes. The workability, compressive strength, split tensile and flexural strengths, modulus of elasticity, density, water absorption and volume of voids, and ultrasonic pulse velocity (UPV) properties of all the mixes were investigated. From the experimental findings it was observed that the fibers significantly improve the mechanical properties of both normal and recycled aggregate concretes. Further among the WF, GF, and SF, SFs had shown more positive impact on the properties of concrete. K E Y W O R D S compressive strength, flexural strength, glass fibers, recycled aggregate concrete, steel fibers, ultrasonic pulse velocity (UPV), woolen fibers
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