Влияние пластифицирующих добавок на процесс твердения бетона в условиях сухого жаркого кли-мата

Abstract

The negative impact of a dry hot climate on the strength characteristics of heavy concrete is considered. At elevated air temperatures, significant evaporation of moisture from the solidified concrete mix may subse-quently lead to the formation of cracks and other deformations in the concrete body. The abovementioned problems can be prevented by introducing plasticising additives into the concrete mix. The compressive strengths of concrete made of concrete mixtures with different percentages of plasticising agents and ex-posed to elevated temperatures are determined in the study. The compressive strength of the studied sam-ples was determined in accordance with GOST 10180-2012 “Concretes. Methods for determining the strength of the control samples." The optimum amount of the additive CentramentAir 202 in concrete is 0.25% by weight of cement, while the increase in compressive strength of concrete is 11.5% at the age of 14 days and 1.7% at the age of 28 days, in relation to the compressive strength of the control composition. The in-troduction of the hyperplasticiser MC-PowerFlow 2695 in the amount of 0.4 to 0.6% by weight of cement reduces the compressive strength of concrete samples by an average of 29% at the age of 14 days and by 39.4% at the age of 28 days. Superplasticiser CentramentN 101 in an amount of from 0.6 to 1% by weight of cement reduces the compressive strength of concrete samples by 11.5% ÷ 35% at the age of 14 days and by 19–37.4% at the age of 28 days. The optimal amount of MC-Techniflow 70 additive in concrete is 1.2% by weight of cement, while the compressive strength of concrete is increased by 2.1% at the age of 14 days and by 0.6% at the age of 28 days. According to the results of the experiments, a highly plasticis-ing additive MC-Techniflow 70 with an optimal dosage in the amount of 1.2% by weight of cement was acknowledged as effective, allowing to obtain high strength characteristics both at 14 days of age (29.2 MPa) and at 28 days of normal hardening (35.0 MPa).