Mechanical properties and microstructure analysis of fly ash geopolymeric recycled concrete.

TL;DR: This study investigates the specimen size effect on compressive and splitting tensile strengths of geopolymeric recycled aggregate concrete, revealing size-dependent strength reductions and proposing analytical models for size effect laws, with implications for sustainable and low-carbon construction.

TL;DR: In this paper , a detailed analysis of parameters specific to cenospheres, which distinguish them from other solid fly ash particles and open new possibilities of their utilization, is presented.

Abstract: Low-calcium fly ash (LCFA)and ground granulated blast furnace slag (GGBS)-based geopolymer concretes are ecofriendly novel concrete to be used as an alternative to traditional OPC concrete. Natural resources are used in the production of cement, while industrial and demolished concrete wastes such as GGBS, LCFA, and recycled concrete aggregate (RCA) are used in the production of geopolymer concrete (GPC) to save natural resources. In this study, the aim is to produce a novel geopolymer concrete with a fairly high strength, up to 85 MPa as compared to the strength achieved so far by other researchers using RCA, GGBS, and LCFA. In addition to this, the emphasis is to utilize the used coarse aggregate obtained from demolished waste. The other objective is to produce the concrete usable in arid regions where water is scarce. These objectives have been accomplished in two steps have followed. In the first step, the preparation of solid and liquid binders was accomplished. The actual solid binders were decided based on trial solid binders consisted of LCFA and GGBS in the ratios of 3:2, 2:3, and 1:4. The liquid binder taken was a solution of silicate and hydroxide of sodium. In the second step, used coarse aggregate after removing the old mortar coating from the surface, was used as a substitute for 25%, 50%, 75%, and 100% of natural coarse aggregate in the GGBS–LCFA-based GPC. The impact of the RCA on the workability, physical and mechanical properties, and durability properties of the produced GPC was determined. The mechanical properties of all the mixes were satisfactory. However, the GPC with sample mix F40G60R0 has proved to be the most satisfactory of all the properties. Sample mix F40G60R50 with 50% RCA and 60% GGBS addition showed the highest compressive strength of 84.31 MPa among all the mixes except sample mix F20G80R0. The presence of RCA in the matrix increased the number of nucleation sites available in the interfacial transition zone (ITZ), resulting in a denser matrix structure. The major difficulty faced was the complete removal of the old mortar coating from the used coarse aggregate to produce RCA. The results revealed that GPC may include a high percentage (up to 100%) of RCA with 60% of GGBS to give sufficient strength for practical applications.

TL;DR: In this paper , the authors present the importance of the ITZ, their chemistry and microstructure, consequences of theITZ, the effect of pozzolana in cement matrix on interfacial transition zone, and the role of temperature in establishing the CSH gel in the structure.

TL;DR: In the last few years, technological progress has been made in the development of new materials such as "geopolymers" and new techniques, such as ''sol-gel'' as mentioned in this paper, opening up new applications and procedures and transforming ideas that have been taken for granted in inorganic chemistry.

TL;DR: In this paper, the mechanism of activation of fly ash with highly alkaline solutions is described, and the product of the reaction is an amorphous aluminosilicate gel having a structure similar to that of zeolitic precursors.

TL;DR: In this paper, the potential position of and drivers for inorganic polymers (“geopolymers”) as an element of the push for a sustainable concrete industry are discussed.

TL;DR: The concrete industry is known to leave an enormous environmental footprint on Planet Earth as discussed by the authors, which contributes to the general appearance that concrete is not particularly environmentally friendly or compatible with the demands of sustainable development.