Implication of concrete with chemical admixture cured in low temperature on strength, chloride permeability and microstructure

Abstract

Concrete does not gain complete strength when cured in low temperature as the hydration of cement does not take place completely. The concrete cured in cold weather does not gain early strength and leads to improper setting and uneven strength gain due to the freezing of the water mixed with the cement. Hence, there are many strength-related problems faced at site due to cold weather particularly in parts of north India where the temperature reaches below freezing point of water during the winter season. The study focused on the effect of combination of accelerator, superplasticizer and air-entraining admixture on microstructure, compressive strength and chloride ion penetration of concrete cured at +5 °C and a comparative study with normal cured concrete with chemical admixture. Five different mixes were used containing varying amount of accelerators, superplasticizers and air-entraining admixture of a manufacturer which are available for use in India. The results for compression strength show that the concrete mix with higher dosage of accelerator had higher strength. The strength results were nearly the value of normal cured concrete with chemical admixture. Rapid chloride permeability test showed very low permeability for all of specimens of last mix, and results were nearly comparable to normal cured concrete. The microstructure study of concrete with admixture ensures a dense structure formation resulting in higher strength at low temperature.