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  • The objective of the present work is to search


    The objective of the present work is to search for the optimum blend when 12.5–50% metakaolin is substituted by RHA and reacted with 10 M sodium hydroxide solution to produce geopolymers. It was hypothesized that the amorphous Bacitracin from RHA will increase the Si/Al ratio of the mix and in situ react with sodium hydroxide to form the silicate gel that will contribute to the polycondensation reaction to improve the performance of the resulting geopolymer. The chemical and mineralogical characteristics and the specific gravity of raw materials were determined. The consistency and setting time of fresh geopolymer pastes were tested. Hardened products underwent tensile strength test based on the standard test method for tensile strength of chemical resistant mortars, grouts and monolithic surfacings, ASTM C 307-03 (2012) [30] for potential use of the elaborated material in non-structural applications in construction like repairs within tension zone and grout works (filling and sealing). Scanning Electron Microscopy coupled with Energy Dispersive Spectrometry (SEM /EDX) and thermo-gravimetric (TG) analyses were also applied on hardened pastes test specimens.
    Materials and experimental procedure
    Results and discussions
    Conclusions The performance of geopolymers made with MK partially substituted by RHA in the presence of 10 M sodium hydroxide solution was studied. From the investigations carried out, the following conclusions can be drawn:
    Conflict of interest
    Introduction Globally, a net rice production of 678 million tones was observed during 2009 season by Food and Agriculture organization [1], [2] and from such amount of rice, a rice husk of 20% is obtained [3]. This amount is considered as waste materials according to industrial point of view. After incineration of Rice husk, the Rice Husk Ash is remain as waste materials [3], [4]. The need of limiting the content of carbon produced during the production of cement drove the scientific research toward the use of industrial by-products to be incorporated as a supplementary cementitious materials (SCMs) [5]. According to Islam et al. [6], cement factory normally released approximately one tone of CO2 for the net production of one tone of cement. A substantial research has been also carried out on the use of Rice Husk Ash (RHA) as a pozzolonic SCMs. The biodegradability of rice husk is very less as compared to wheat straw and other agro waste product and also it has been observed that burning of Rice husk took a longer time and consequently environmental annoyance produced [5]. The Rice Husk Ash normally contain up-to 20% amorphous silica which is considered as the highest amount of silica in residue of plants [7], and this silica content with high reactivity may be enhanced under controlled combustion conditions [8]. RH that burnt under controlled environment to convert into ash accomplished the chemicals composition and physical characteristics of minerals admixtures [9]. Pozzolonic behavior of RHA mainly depends upon the size of ash particles, the surface area of the ash [10], [11], [12], [13], the crystallization phase of silica and the silica content in RHA. Under controlled temperature, the combustion of RH produces amorphous silica content and particles of large surface areas [14]. To obtain good quality ash, special type of furnace or incinerators for burning and grinding techniques for RH are adopted. The burning procedure of RH was developed from the burning in the open air in 1970s to liquidized layers technique in 1990s [9]. In the liquidized technique, controlled temperature and time of combustion was considered as the best achievement in the combustion technology [15]. In this method, a moderate temperature for a short time is mandatory to obtain a good content of ash. However, many researchers collect RHA directly from rice mills [9], [16]. In literature, the use of RHA as a supplementary cementitious materials due to its pozzolonic nature with economical and environmental benefits are available [15], [17].