Influence of Fly ash Content on Physical and Mechanical Properties of Magnesium Oxychloride Cement Concrete

Abstract

Abstract: In order to expand the application fields of magnesium oxychloride cement (MOC) materials, magnesium oxychloride cement concrete (MOCC) with different fly ash content was prepared by using bischofite, light burned magnesia and fly ash as cementitious materials, in which bischofite is a by-product of potassium fertilizer extracted from salt lake. The influence of fly ash content on compressive strength, phase composition, micromorphology and pore structure of MOCC were studied. The results show that with the increase of fly ash content, the compressive strength of MOCC gradually decreases. When the content of fly ash is 40% (mass fraction), its 300 d compressive strength decreases to 39.99 MPa, which is a decrease of 22.52%. The main hydration products of MOCC are 5Mg(OH)₂·MgCl₂·8H₂O(5·1·8) and Mg(OH)₂. The addition of fly ash does not produce a new crystal phase. The addition of fly ash increases the porosity and harmful pore volume of MOCC, thereby reducing its compressive strength. Ordinary Portland cement concrete was prepared with the same water-cement ratio. The comparative test results of compressive strength show that although the compressive strength of MOCC with 40% fly ash is lower than that of MOCC without fly ash, it is still 19.66% higher than that of ordinary Portland cement concrete at 300 d age, indicating that MOCC has higher compressive strength than that of ordinary Portland cement concrete.

Key words: bischofite, magnesium oxychloride cement concrete, microstructure, fly ash, compressive strength, setting time

CLC Number:

TU528

LIU Pan, CHANG Chenggong, LIU Xiuquan, DONG Jinmei, ZHENG Weixin, XIAO Xueying, WEN Jing. Influence of Fly ash Content on Physical and Mechanical Properties of Magnesium Oxychloride Cement Concrete[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2021, 40(5): 1564-1572.

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