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Impact of temperature and duration of calcination of metakaolin on the compressive strength of metakaolin incorporated concrete
Published in Alka Mahajan, Parul Patel, Priyanka Sharma, Technologies for Sustainable Development, 2020
The Process of Calcination: The pozzolanic reactivity of a pozzolanic material depends upon its physical characteristics like its particle size, crystallanicity, LOI and chemical composition. Metakaolin is a manufactured pozzolanic material and its calcination temperature and the duration of calcination affects its physical characteristics. (Kaloumenou M, Badogiannis et al,1995, & M.H.Zang et al. 1995). Thus, for a manufactured product like metakaolin, its manufacturing process is an important aspect which has to be clearly understood to manufacture a highly reactive pozzolanic material. Metakaolin (Al2O3.2SiO2) or AS2, typically consists of alumina and silica. It is obtained by heat treating kaolin clay under controlled temperature conditions (650°C-850°C) for a certain period of time (residence time). During this process of heat treatment, the crystalline structure of kaolinite gets converted into a highly amorphous phase called metakaolin (Kakali G. Perraki T et al. 2001, J.A.K: R.Kostuch, 2000 & B. B. Sabir, 1996). The major reorganization occurs in the Al-O network of the structure, whereas the Si-O network remains intact. The initial days pozzolanic reactivity of metakaolin is due to the highly unstable Al-O atoms of the network. This highly reactive alumina immediately reacts with the cement hydration products mainly CH to form other crystalline products such as calcium aluminate hydrates (C3AH6, C4AH13) and calcium aluminosilicate hydrates (C2ASH8,). The later days pozzolanic reactivity in metakaolin is due to silica network (Si-O) (Bai J. 1999).
Effect of natural rubber latex in concrete with metakaolin admixture
Published in Sheela Evangeline, M.R. Rajkumar, Saritha G. Parambath, Recent Advances in Materials, Mechanics and Management, 2019
Metakaolin is a mineral admixture obtained by refining the kaolin clay. It was further refined to produce amorphous aluminosilicate which shows good ability of reactiveness towards concrete. Metakaolin was obtained from the English.
2 cement for sustainable concrete
Published in Paolo Gardoni, Routledge Handbook of Sustainable and Resilient Infrastructure, 2018
Metakaolin has a higher cost than other SCMs; in US dollars, metakaolin is approximately $300–$500/ton compared to $100–$120/ton for cement and $40–$50/ton for fly ash. This limits its use in concrete, though performance can be quite good. Recently, there has been a strong push toward exploring other clay minerals and low purity kaolinite bearing-minerals (Fernandez et al. 2011; Taylor-Lange et al. 2015; Alujas et al. 2015; Hollanders et al. 2016), with an interest in expanding availability and reducing cost. Results have shown that calcined smectic (montmorillonite/bentonite) clays are pozzolanic, though less so than calcined kaolinitic clays. Blends of clays containing kaolinite and some montmorillonite also show promising performance.
Synergic effect of some waste pozzolans on the mechanical and shielding properties of geopolymer concretes
Published in Radiation Effects and Defects in Solids, 2023
Barış Bayrak, Ali Öz, Esra Kavaz, Gökhan Kaplan, Oğuzhan Çelebi, Haluk Görkem Alcan, Abdulkadir Cüneyt Aydın
GBFS consists of SiO2, Al2O3, CaO, and MgO; and it is nearly the same Portland Cement due to hydration reaction. However, if the ratio of GBFS in the mixture is increased, the concrete compressive strength decreases because of the delay of hydration (21). On the other hand, as a result of development of the iron and steel material industry, utilizations of GBFS are increasing. For instance, at the stage of iron production, GBFS as waste material occurs the approximately 30% of the iron material (22). SF is a waste material that is a by-product of the electric arc furnace processing of elemental silicon or silicon alloys (23,24). SF is preferred by researchers in the concrete mixture owing to very small particle size and high pozzolanic reactivity. Moreover, SF is a type of pozzolanic material (25,26). Metakaolin (MK) is not only pozzolanic material, but also the product from kaolinite clay. MK has the positive effect on the mechanical and durability properties of concrete owing to very small particle size (27). Due to the fact that MK consists of huge level silica and alumina, the C/S ration of C–S–H gel increases in the geopolymer concrete mixture (28).
Properties of metakaolin-based green pervious concrete cured in cold and normal weather conditions
Published in European Journal of Environmental and Civil Engineering, 2022
Armin Azad, Sayed-Farhad Mousavi, Hojat Karami, Saeed Farzin, Omid Rezaifar, Ali Kheyroddin, Vijay P. Singh
Pervious concrete is known as a solution for water-sensitive urban design. Cementitious materials are usually used as replacement of cement to reduce emission of carbon dioxide to atmosphere. Metakaolin is a cementitious material which shows acceptable performance in conventional concrete. Results of the present study showed that for pervious concrete, metakaolin could have a diverse performance in the structural properties, with respect to curing situations. For samples cured in spring (normal air temperature), metakaolin was a substitute for cement with an appropriate performance in the structural properties. However, using metakaolin in previous concrete samples, cured in winter (cold air temperature), results in negative impacts on the structural properties, specifically the compressive strength. The mixtures with 5%, 10%, 15%, 20% and 25% metakaolin which were cured in winter had 12%, 23%, 28%, 47% and 36% less compressive strength than the samples cured in spring, respectively. In addition, it was found that adding a low amount of quartz, dolomite and vermiculite, as fine aggregate, could have positive impacts on the compressive strength in both groups of samples, cured in winter and spring. Therefore, it is suggested not to use metakaolin in pervious concrete which is going to be cured in winter. Also, if for some reasons metakaolin should be utilised in samples to be cured in winter, it is proposed to add the mentioned minerals to compensate the low compressive strength.
Effects of metakaolin on mechanical and microstructural properties of ultra-high performance cement-based composites
Published in Journal of Sustainable Cement-Based Materials, 2018
Zhidan Rong, Guang Jiang, Wei Sun
To achieve such a high strength material, a low water-to-binder ratio (normally w/b < 0.2) should be applied with ultra-fine reactive powders. As a result, the mechanical properties of UHPCC are more susceptible to the type of cementitious materials and aggregate size, as compared to those of ordinary concrete. As is well known, fly ash (FA), silica fume (SF) and ground granulated blast furnace slag (GGBFS) are the traditional pozzolanic materials widely used to partially replace cement to prepare concrete and UHPCC. Metakaolin (MK) is an ultra-fine pozzolan, manually manufactured by calcination of purified kaolin clay at a temperature ranging between 650 and 900 °C to drive off the chemically bound water and destroy the crystalline structure [8]. The pozzolanicity of MK is even superior to SF [9]. A lot of research has been carried out over the last two decades to understand the influence of MK on properties of cementitious materials [10–13].