The influence of lightweight aggregate, freezing-thawing procedure and air entraining agent on freezing-thawing damage

摘要

This article presents the results of a study dealing with the concrete resistance to repeated cycles of freezing and thawing of nonair entrained, fine lightweight aggregate (LWA) and air-entrained concrete when tested in accordance with ASTM C 666, procedures A and B. The water-to-binder ratios (w/b) of the mixtures ranged from 0.25 to 0.35, and the percentage of cement replacement by silica fume were 7% on a weight basis and constant throughout study. Binder dosage was 500kg/m(3) and constant. LWA was pumice aggregate (PA) and expanded perlite aggregate (EPA). PA and EPA were replaced by 10, 20, and 30% of total volume of 1 m(3) as a fine aggregate (0-2 mm fine aggregate fraction). Also one group was produced with air entraining agent by 0.1% ratio of binder dosage. The 200 freeze-thaw cycles were carried out according to ASTM C666/C666M-15, procedure A and B. The compressive strength, ultrasonic pulse velocity, relative dynamic modulus of elasticity and dry unit weight of mixtures were investigated. Based upon the analysis of the test data, it is concluded that samples contain air-entrained agent and 10% LWA were more durable than that of control sample. With the increasing of the LWA content the freeze-thaw resistance of samples decreased. Thus, higher content of LWA is not recommended when it is to be subjected to repeated freeze-thaw cycles. Freezing-thawing procedures were compared with each other and found that procedure A was more severe than procedure B.