Experimental investigation on the mechanical and fracture evaluation of carbon Fiber-Reinforced cementitious composites with Nano-Calcium carbonate

•Different GPM cementitious composites are fabricated.•Effect of micro-carbon fibers and n-calcium carbonate is investigated.•Various mechanical, fracture, and microstructural properties are assessed.•Improvement in mechanical efficiency of GPM cementitious composite is observed. Geopolymer (GPM) cementitious composites can be efficiently employed as a practical substitute for cement to avoid the high carbon footprint and to develop sustainable concrete construction. Limited research is available in the previous studies that examine the efficiency of GPM composites including micro-fibers and nano-particles. Therefore, it is necessary to investigate the efficiency of fiber-reinforced (FR) GPM composites comprising nano-particles for their practical implementations towards environmental sustainability. The present investigation has struggled to improve the mechanical and microstructural efficiency of micro carbon-FR fly ash-based GPM mixes by incorporation of different quantities of nano calcium carbonate (n-calcium carbonate). Four different extents of n-calcium carbonate i.e. 1%, 2%, 3%, and 4% wt. % of the mix was used to fabricate GPM mixes comprising a fixed extent of micro carbon fibers (i.e. 1% wt. %). A control mix with 1% micro carbon fibers having no extent of n-calcium carbonate was also fabricated for comparison purposes. The average results of six samples from each mix were used to assess various mechanical and fracture features of GPM mixes. The microstructural analysis was also performed on the tested samples employing scanning electron microscopy. The outcomes of the present investigation exhibited that the use of 3% n-calcium carbonate in carbon-FR-GPM mix portrayed the optimum results for hardness and compressive strength whereas employing 2% n-calcium carbonate delineated the optimum results for flexural strength, fracture toughness, and impact strength of composites. The SEM analysis of samples illustrated that including n-calcium carbonate considerably accelerates and ameliorates the microstructure of GPM.