Effect of recycled materials on strength and autogenous shrinkage of ultra-high performance concrete

Document Type : Research Article

Authors

1 Department of CIVIL ENGINEERING , QAZVIN BRANCH, ISLAMIC AZAD UNIVERSITY, QAZVIN, IRAN

2 Faculty of Engineering, Civil Engineering Department, Kharazmi University, Tehran, Iran

Abstract

The aim of this study is to decrease the silica fume (SF) content of UHPC by using natural zeolite (NZ) with different levels of replacement (25%, 50% ,75% and 100% by volume), in order to mitigate autogenous shrinkage with almost equivalent mechanical performance. The results demonstrated that addition of NZ as replacement of SF had a positive effect on maintaining internal RH in the higher range as well as in reducing the autogenous shrinkage of UHPC. The mixtures with 25%, 50%, 75% and 100% replacing SF by NZ had lower autogenous shrinkage compared to reference mixtures containing 100% SF. The results of Thermogravimetric and microstructure analysis indicated that NZ had appropriate pozzolanic activity. The results of the compressive strength test showed that by replacing 50% SF with NZ, the 90 days compressive strength of 164.37 MPa could be achieved, which was only slightly lower than the reference mixture with a 90 days compressive strength of 169.07 MPa. replacing SF with NZ yielding a cost-effective solution. By replacing 50% NZ replacement of SF, UHPC mix with 90 days compressive strength over 150 MPa, with low autogenous shrinkage and relatively low cost can be produced.

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