Physical and Mechanical Properties of Concrete with Locally Produced Metakaolin and Micro-silica as Supplementary Cement
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RESEARCH PAPER
Physical and Mechanical Properties of Concrete with Locally Produced Metakaolin and Micro‑silica as Supplementary Cementitious Material Sadaqat Ullah Khan1 · Tehmina Ayub2 · Nasir Shafiq3 Received: 3 July 2017 / Accepted: 23 June 2020 © Shiraz University 2020
Abstract Malaysia is among the countries that have abundant reserves of raw material to be used to form metakaolin (MK). Only a few studies are available in the literature, which examines the potential of the development of metakaolin through calcination and its use as supplementary cementitious material (SCM). The use of MK as SCM is essential to utilise the local resources and to reduce the carbon footprint and embodied energy in the use of cement. Thus, MK developed at laboratory scale, produced through using local source, is compared with the commercially available micro-silica by investigating their properties in this paper. The concrete made of MK and micro-silica was tested under compression, split tension and bending. The comparison of the phase difference between MK and micro-silica had carried out through X-ray diffraction pattern. Besides, an interfacial transition zone of concrete made of MK and micro-silica had observed through field emission scanning electron microscopy. A total of three mixes of concrete had prepared, out of which one was without cement replacement and served as control mix. The remaining two mixes were 10% cement replacement with micro-silica and MK. The results showed that MK has high reactivity with portlandite in concrete due to its irregular structure and the amorphous phase. The compressive strength was 4% higher with MK as compared to micro-silica at an early age. MK concrete displayed a higher split tensile strength of approximately 14% and 35% and a higher load-carrying capacity of approximately 15% compared to micro-silica and competitive with control concrete at ages 7–90 days. Keywords Metakaolin · Compressive strength · Split tensile strength · Load–deflection behaviour · Interfacial transition zone
1 Introduction Metakaolin (MK) is amorphous silica, which is a treated substance acquired through the calcination of refined kaolinite (or kaolin) (Newman 2003; ACI 363R-92 1992). MK was * Tehmina Ayub [email protected] Sadaqat Ullah Khan [email protected] Nasir Shafiq [email protected] 1
Urban and Infrastructure Engineering Department, NED University of Engineering and Technology, Karachi, Pakistan
2
Civil Engineering Department, NED University of Engineering and Technology, Karachi, Pakistan
3
Civil and Environmental Engineering Department, Universiti Teknologi PETRONAS, Seri Iskandar, Perak, Malaysia
recognised as a mineral admixture in 1990 (Newman 2003); however, at that time, it was not known that MK had a positive effect on concrete strength due to its consistency variation. Martin (1995) stated that the use of MK in concrete increased the compressive strength to 110 N/mm2 (16 ksi). Ding and Li (2002) compared MK and silica fume concrete in terms of compressive stre
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