Mechanical, environmental, and economic assessment of sustainable cement mortar using Afghan natural pozzolan as a partial replacement for cement

Using natural pozzolan to produce cement-based mortar is one of the suitable solutions to reduce cost, energy consumption, and environmental impacts. In this experimental study, the paste replacement methodology (replacement of partial cement wt% with supplementary cementitious material) is used. Natural pozzolan, as vernacular material with high silicate aluminate originating in Afghanistan, is replaced (6, 13, and 20%) with cement in mortar. Various tests such as slump, compressive strength, tensile strength, water absorption, freezingthawing cycles, relative length change, pull-off test, and microstructure analysis have been performed to study the properties of fresh and hardened mortar. The findings showed that the use of natural pozzolan containing a high level of silicate and aluminate as a replacement of cement in mortar improved 56 days compressive and tensile strength of mortar by 2.2 and 6%, respectively, water absorption was reduced by 1.6%, and the resistance to the freezing and thawing cycles was increased 10.7% as well compared to the reference samples. In addition, the results of economic analysis and sustainable development indicators assessment of mortar showed that using this replacement methodology was economically acceptable and reduced the potential of global warming and energy consumption by 13% of the production of one ton of cement using standard technology. The optimum replacement percentage was selected at 13% without compromising the mechanical properties of mortar.