The influence of wollastonite and microsilica on durability, freeze and thaw of concrete in sulfate and chlorate environment

Kazemi, Milad (2018) The influence of wollastonite and microsilica on durability, freeze and thaw of concrete in sulfate and chlorate environment. Masters thesis, University of Mohaghegh Ardabili.

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Text (بررسی تاثیر ولاستونیت و میکروسیلیس بر دوام بتن در برابر ذوب و انجماد در محیط سولفاته و کلراته) Milad Kazemi.pdf Download (772kB) | Preview

Abstract

In contrary to the inherent durability of concrete, there are so many concrete structures that don’t show effective properties against coid and drastic weather. One of the most important reason of demolition of concrete in cold region of iran emanate from freeze and thaw cycles of concrete. Strength of concrete against freeze and thaw cycles depends on and high stress on concrete, especially when water of aggregates becomes solid and alters volume of concrete in cold weather. This change in valume creates fine cracks in concrete. That finally cause decline in strength and invited numerous investigations. The problem becomes more critical when concrete in addition to continuous freeze and thaw is placed in destructive environments such as chlorate and sulfate. In this study effect of microsilica (0%, 5% and 7.5%) and wollastonite (0%, 5%, 10% and 12.5%) replaced with cement on four condition of control samples, cyclic samples in normal environment, cyclic samples in sulfate environment were investigated. Totally 432 samples were created wich were divided into 4 groups of 108. 108 samples were measured as control samples at the age of 28, 56 and 74 days (simult aneously with completion of cycles of 45, 100 and 150) and three other 108 groups were also subjected to freezing and thawting tests according to the ASTM C 666B standard after 45, 100 and 150 cycles). Compressive strength and ultrasonic testing (dynamic modalus of elasticity) of samples after freeze and thaw cycles were considered as a perseverance criteria of concrete. In studying the effect of microsilica mixing with wollastonite the highest compressive strength was obtained for 5% microsilica with 5% wollastonite.

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