Sulphate Induced Strength Loss Index Optimisation of Periwinkle and Clam Shell Ash Hybrid Pozzolana Concrete

Abstract

The globe yearns for sustainability in meeting the present and future needs of man. Hence, research into a more sustainable modes of harvesting, processing and use of nature’s raw resources is evidently timely. Cement replacement is opined on the need to reduce the environmental as well as economical limitations associated with its production, while been configured to allow for adequate strength and durability. This paper introduces the mechanical behaviour of ternary blended cement composed of Portland limestone cement, calcined periwinkle and clamshell ashes in concrete exposed to a sulphated medium. Combined I-optimal mixture design was used to statistically develop and diagnose models from laboratory-analysed data and used to optimize calcination temperature and synergistic ratio, as well as the compressive strength and sulphate induced strength loss index (SISLI). For a constant sulphate medium of 5% sodium sulphate solution, the volatile calcination temperature range (25^oC – 200^oC) was separated from the placid (335^oC – 800^oC) during optimization. In comparison to a 28-day control SISLI of 16.47%, the optimal calcination temperature for SISLI was restricted at 606.7^oC, yielding a respective SISLI of -0.078%. With respect to synergistic ratio, the developed model suggests that increasing the concentration of clamshell ash lowers the calcination temperature needed to improve concrete's resistance to sulphate attack, however, a balance needed for other mechanical and durability variables provided a ternary configuration of 54.6%PLC:25.1%PSA:20.3%CSA at a calcination temperature of 606.7%. The developed model can hence be integrated into the engineering society in decision making and policies associated with the adequate use of periwinkle and clamshell ashes as components of a ternary blended cement in concrete exposed to a sulphated environment.