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Materials 2016, 9(3), 146; doi:10.3390/ma9030146

Pozzolanic Reactivity of Silica Fume and Ground Rice Husk Ash as Reactive Silica in a Cementitious System: A Comparative Study

1
Guangdong Provincial Key Laboratory of Durability for Marine Civil Engineering, College of Civil Engineering, Shenzhen University, Shenzhen 518060, China
2
Department of Architectural and Civil Engineering, City University of Hong Kong, Hong Kong, China
3
Department of Mechanics and Civil Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632, China
4
Ceneter for Durability and Sustainability Studies of Shandong Province, Qingdao Uiniversity of Technology, Qingdao 266033, China
*
Authors to whom correspondence should be addressed.
Academic Editor: Jorge de Brito
Received: 10 November 2015 / Revised: 15 February 2016 / Accepted: 17 February 2016 / Published: 1 March 2016
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Abstract

This study comparably assessed the pozzolanic effect of silica fume (SF) and ground rice husk ash (RHA) as supplementary cementing materials on the properties of blended cement pastes and concretes. A commonly commercial silica fume (SF) and locally-produced rice husk ash (RHA) samples with two finenesses (one with larger size than cement and the other with smaller size than cement) were used in this study. Material properties of SF and RHA were experimentally characterized. Hydration and mechanical properties of cement pastes incorporating SF and RHA were determined by thermogravimetric analysis (TGA) and compressive strength tests, respectively. Properties of concretes regarding workability, mechanical property, durability, and microstructure were evaluated. Results showed that, although the finely ground RHA used in this study possessed lower SiO2 content and higher particle size compared to SF, it exhibited comparable pozzolanic reactivity with SF due to the nano-scale pores on its each single particle, leading to a higher specific surface area. The optimal replacement levels of SF and RHA were 10% by weight of cement in pastes and concretes. Although addition of SF and RHA led to a significant reduction in slump for the fresh mixtures, inclusion of up to 30% of SF or 15% of ground RHA did not adversely affect the strength of concretes. At the same mix, incorporation of finely-ground RHA in cement composites provided comparable mechanical properties, hydration degree, and durability with SF blended cement composites, owing to the porous structure and high specific surface area of RHA particles. Microstructure morphology analysis of concretes explored by scanning electron microscopy (SEM) further validated the strength and the durability test results. View Full-Text
Keywords: silica fume; rice husk ash; pozzolanic reactivity; strength; chloride ion penetration resistance; morphology silica fume; rice husk ash; pozzolanic reactivity; strength; chloride ion penetration resistance; morphology
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Xu, W.; Lo, T.Y.; Wang, W.; Ouyang, D.; Wang, P.; Xing, F. Pozzolanic Reactivity of Silica Fume and Ground Rice Husk Ash as Reactive Silica in a Cementitious System: A Comparative Study. Materials 2016, 9, 146.

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