Abstract
In this study, three different hardening accelerating admixtures (sodium carbonate, lithium carbonate and a blend of sodium and lithium carbonates) were employed to prepare calcium sulphoaluminate cement-based mortars. The workability, setting times, entrapped air, elasto-mechanical properties such as compressive strength and dynamic modulus of elasticity, free shrinkage, water absorption and carbonation rate were measured and mercury intrusion porosimetry were also performed. Experimental results show that a mixture of lithium carbonate and sodium carbonate acts as a hardening accelerating admixture, improving the early-age strength and promoting a remarkable pore structure refinement. Finally, sodium carbonate also reduces the water absorption, the carbonation rate and the shrinkage of mortars without affecting the setting times and the workability.
Highlights
IntroductionThe construction sector has been looking for some solutions able to reduce the environmental impacts typical of building materials, related to the use of Portland cement, which requires a considerable amount of raw non-renewable natural resources and a great energy input during the clinker production [1].Several strategies have been proposed by different authors [2,3] aimed at improving the sustainability of cementitious materials: reduction of the greenhouse gases emission by using alternative fuels [4,5], replacement of Portland cement (OPC) clinker with low-carbon supplementary cementitious materials (SCM) [6,7,8], utilization of wastes [9,10] and development of alternative binders (such as alkali-activated materials) [11,12].One of the most interesting and simple ways to reduce the environmental impact of mortars and concretes is using calcium sulphoaluminate cement (CSA) as a partial replacement of ordinaryPortland cement [13]
Two sustainable CSA-based mortars in which OPC is totally replaced by supplementary cementitious and SM 2, respectively) in which OPC is totally replaced by supplementary cementitious materials materials (SCMs, ground granulated blast furnace slag (GGBFS) according to EN 1516-7 and low (SCMs, ground granulated blast furnace slag (GGBFS) according to EN 1516-7 and low calcium fly calcium fly ash (FA) according to EN 450-1) and hydrated lime CL-90S class
A small increase in workability was observed in mortars manufactured with sodium carbonate admixtures or SC–lithium carbonate (LC)
Summary
The construction sector has been looking for some solutions able to reduce the environmental impacts typical of building materials, related to the use of Portland cement, which requires a considerable amount of raw non-renewable natural resources and a great energy input during the clinker production [1].Several strategies have been proposed by different authors [2,3] aimed at improving the sustainability of cementitious materials: reduction of the greenhouse gases emission by using alternative fuels [4,5], replacement of Portland cement (OPC) clinker with low-carbon supplementary cementitious materials (SCM) [6,7,8], utilization of wastes [9,10] and development of alternative binders (such as alkali-activated materials) [11,12].One of the most interesting and simple ways to reduce the environmental impact of mortars and concretes is using calcium sulphoaluminate cement (CSA) as a partial replacement of ordinaryPortland cement [13]. Several strategies have been proposed by different authors [2,3] aimed at improving the sustainability of cementitious materials: reduction of the greenhouse gases emission by using alternative fuels [4,5], replacement of Portland cement (OPC) clinker with low-carbon supplementary cementitious materials (SCM) [6,7,8], utilization of wastes [9,10] and development of alternative binders (such as alkali-activated materials) [11,12]. One of the most interesting and simple ways to reduce the environmental impact of mortars and concretes is using calcium sulphoaluminate cement (CSA) as a partial replacement of ordinary. For this reason, ternary mixtures of OPC, CSA and calcium sulphate (gypsum, anhydrite or hemihydrate) were largely investigated and properties like rapid setting times, fast.
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