The problem of the equivalent time to start the internal frost resistance test on self-compacting concrete with supplementary cementitious materials. (November 2020)

• Record Type: Journal Article
• Authors: Łaźniewska-Piekarczyk, Beata; Piekarczyk, Adam
• Is Part Of: Journal of building engineering. Volume 32(2021)
• Publication Date: 2020-11
• Subjects: Self-compacting concrete -- Frost-resistance -- Supplementary cementitious materials -- Non-destructive tests -- Relative dynamic modulus of elasticity; Building -- Periodicals; 690.05
• DOI: 10.1016/j.jobe.2020.101503
• Languages: English
• ISSNs: 2352-7102

Abstract

Abstract: The article presents the results of tests on frost resistance of self-compacting concretes made with the use of cement containing mineral additives after 150 freezing and thawing cycles. Concrete with types of cement containing 30 and 50% blast furnace slag, cement with 30% silica fly ash and with types of cement containing both slag and ash with a combined proportion of 60% (30% both mineral components) and 80% (45% slag and 35% ash). The relative dynamic modulus of elasticity determined based on the ultrasonic pulse transit time RDM UPTT was used as the basis for the measure of frost resistance. The tests were carried out on cubic specimens with a side length of 150 mm, which are standard for testing the compressive strength of concrete. The relative dynamic modulus of elasticity RDM UPTT has proved to be a qualitatively correct measure of concrete's frost resistance. The RDM UPTT values corresponded to the values of the auxiliary measure, which in this case was the relative decrease in specimen mass. It was confirmed that tests on frost resistance of concretes with mineral additives should be started in the so-called "equivalent time" depending on the cement composition. Due to the varied increases in concrete strength over time, the consideration of "equivalent time" is intended to improve the reliability of testing methods, including the ultrasonic method. Tests have also shown that the use of an additive in the form of silica fly ash can weaken concrete frost resistance, especially when the fly ash to clinker ratio is high. A positive effect of the addition of granulated blast furnace slag on the frost resistance of concrete was also noticed. Highlights: The results on the frost resistance of self-compacting concrete with blast furnace slag and silica fly ash proved that: Direct and indirect tests of frost resistance of the concrete should not start after the 28 th day but much later. Time to start the direct and indirect frost resistance tests is 56 or 90 days of hardening, in the so-called "equivalent time". Replacing Portland cement with slag and fly ash in an amount of over 50% negatively affects the frost resistance of concrete.