Influence of strong alkaline substances (sodium carbonate and sodium bicarbonate) in mixing water on strength and setting properties of concrete

Abstract

The quality of mixing and curing water plays a vital role in production and application of concrete. In the present study, the effect of strong alkaline substances like sodium carbonate (Na₂CO₃) and sodium bicarbonate (NaHCO₃) on setting time and strength development of concrete is assessed under the laboratory conditions. The results indicate that Na₂CO₃ in deionised water accelerates the initial as well as final setting times whereas the other compound NaHCO₃ retards the initial and final setting times in all concentrations. Na₂CO₃ and NaHCO₃ in deionised water decrease the compressive and tensile strength of concrete specimens significantly at 28 days and 90 days. Comparison of the results of strong alkaline compounds with those of the control mix reveals that both Na₂CO₃ and NaHCO₃ decrease the compressive and tensile strength significantly. The rate of decrease is increasing with the increase in concentration. The present work analyses the hydration characteristics of concrete using the technique of X-ray diffraction (XRD) and useful conclusions are obtained regarding the influence of strong alkaline substances.