Abstract
Portland cement concrete is the most commonly used construction material in the world for decades. However, the searches in concrete technology are remaining growing to meet particular properties related to its strength, durability, and sustainability issue. Thus, several types of concrete have been developed to enhance concrete performance. Most of the modern concrete types have to contain supplementary cementitious materials (SCMs) as a partial replacement of cement. These materials are either by-products of waste such as fly ash, slag, rice husk ash, and silica fume or from a geological resource like natural pozzolans and metakaolin (MK). Ideally, the utilization of SCMs will enhance the concrete performance, minimize environmental pollution and mitigate the drawbacks of cement production attributed to the highly CO2 emission. In general, MK's ultra-fineness and high pozzolanic activity are exhibited a remarkable performance of concrete in terms of strength and durability. However, the filler effect, acceleration of cement hydration, and the pozzolanic reaction with calcium hydroxide (CH) are the main factors influencing the performance of metakaolin as a cementitious material. Therefore, numerous researches have been undertaken on inclusion MK in concrete and mortar and production of (free-cement concrete) geopolymer concrete. This paper reviews some of previous native researches on effect of using Iraqi metakaolin as a pozzolanic material in different types of concrete. The standpoint of this review will guide the researchers on the importance of utilization of local MK and highlight the missing researches toward completing a comprehensive understanding of incorporation Iraqi-metakaolin in concrete technology.
Highlights
Portland cement concrete is the most commonly used construction material in the world for decades
This review paper summarizes some of the national researches regarding the effect of using Iraqi activated kaolinite clay as a partial cement replacement in different types of concrete
This study included the geographical information of kaolinite deposits in Iraq, chemical compositions, and thermal optimization treatment of metakaolin
Summary
Most of SCMs are by-products from industrial waste like fly ash (FA), ground granulated blast furnace slag (GGBS), and silica fume (SF), while some of them are pure as a natural pozzolan. The kaolinite flakes become more deformed and condensed into disordered, amorphous material known metakaolin. This product has a highly reactive transition phase, pozzolanic activity, and suitable for use as supplementary cementing materials in concrete applications (Khatib, et al, 2018), (Rashad, 2013), (Wang, et al, 2018). The results show that the optimum calcination temperature of Iraqi kaolin clay is at 700°C for one hour. Not much different from these findings, (Sldozian, 2012) has found that among (500, 700 and 900) °C, the highest compressive strength of concrete mixtures containing (5, 10, 15 and 20) % of MK would be gained by calcination Iraq kaolinite clay at 700°C for 1hr.
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