Experimental Study on Autogenous and Drying Shrinkage of Steel Fiber Reinforced Lightweight-Aggregate Concrete

Shunbo Zhao,Xiaoyan Zhang,Changyong Li,Mingshuang Zhao

doi:10.1155/2016/2589383

Abstract

Steel fiber reinforced lightweight-aggregate concrete (SFRLAC) has many advantages applied in structural engineering. In this paper, the autogenous shrinkage and drying shrinkage of SFRLAC for up to 270 days were measured, considering the effects of types of coarse and fine aggregates with the changes of water-to-binder ratio and volume fraction of steel fiber, respectively. The properties of mix workability, apparent density, and compressive strength of SFRLAC were also reported and discussed in relation to above factors. Test results show that the development of autogenous and drying shrinkage of SFRLAC was fast within 28 days and tended to be steady after 90 days. The development of autogenous shrinkage of SFRLAC reduced with the increasing water-to-binder ratio and by using the expanded shale with higher soundness and good water absorption, especially at early age within 28 days; the later drying shrinkage was reduced and the development of drying shrinkage was slowed down with the increasing volume fraction of steel fiber obviously; manufactured sand led to less autogenous shrinkage but greater drying shrinkage than fine lightweight aggregate in SFRLAC. The regularities of autogenous shrinkage and drying shrinkage of SFRLAC expressed as the series of hyperbola are analyzed.

Highlights

Shrinkage is a common phenomenon of concrete, which can induce tensile stress when the shrinkage is restrained, and may lead to cracking and reduce the service life and durability of concrete structures [1]
(1) The mix slump was affected by water-to-binder ratio obviously and tended to reduce with the increase of volume fraction of steel fiber
(2) The apparent density of Steel fiber reinforced lightweight-aggregate concrete (SFRLAC) increased with the volume fraction of steel fiber and reduced somewhat with the increase of water-to-binder ratio (W/B); it was less than 1850 kg/m3 or 1950 kg/m3 by using lightweight sand or manufactured sand, respectively

Summary

Introduction

Shrinkage is a common phenomenon of concrete, which can induce tensile stress when the shrinkage is restrained, and may lead to cracking and reduce the service life and durability of concrete structures [1]. As the volume of cement hydration products is less than the sum of volumes of water and binders, pores and capillaries formed in the hardened cement paste. Autogenous shrinkage takes place because of the self-desiccation of pores and capillaries, resulting from the continuous hydration of binder materials after initial setting. Drying shrinkage takes place mainly due to the free water evaporated from the pores and capillaries near element surfaces to ambient air. The main factors influencing drying shrinkage are concrete strength, cement type, geometry, curing condition, and starting age [1,2,3,4] as well as some properties of concrete mix such as cement dosage, fine aggregate percentage, air content, and slump [1, 3, 4]. The coarse aggregate is the bone of concrete, which constrains the shrinkage of concrete in different degrees depending on the type, grading, maximum size, fine aggregate percentage, and volume ratio of aggregate in concrete [5]

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Conclusion