Abstract
The geopolymer cement is a suitable alternative material for Portland cement due to their environmental compatibility, low curing temperature, and high strength. In this research, Kaolin was used as a raw material for the construction of a geopolymer cement, while sodium hydroxide was an alkali hydroxide. Kaolin is calcined at 750 °C to obtain meta-kaolin. Geopolymer samples were prepared at various curing temperatures (25, 50, and 75 °C), different curing times (3, 7, 21, 28, and 60 days) and with different activator ratios (0.6-0.9). The thermal analysis of kaolin was done via DTA/TGA. Investigation on the geopolymer cement structure and phases were performed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and magic angle spinning nuclear magnetic resonance (MAS-NMR). Also, the effects of temperature and time of curing and Na2O/SiO2 molar ratio were studied. The results showed that the maximum compressive strength was 115MPa, which obtained at a molar ratio of Na2O/SiO2=0.9, a curing time of 60 days, and a curing temperature of 75°C. The microstructure of cement was studied using scanning electron microscopy (SEM).
Highlights
Concrete is the most commonly used material in the building industry to build and develop the infrastructure
Meta-kaolin is shown as 2SiO2Al2O3 or Si2O5Al2O2 and is typically prepared at temperatures from 600 to 900 °C, but have reports indicated that the appropriate meta-kaolin for geopolymers is obtained at 700-750 °C [22,23]
The results of DTA showed that the conversion of kaolin to meta-kaolin occurs at a temperature range of 500-600 °C
Summary
Martinović et al [11] investigated the synthesis of low cement concrete by ultrasonic measurements and image analysis. Geopolymers provide compressive strength and high corrosion resistance into Portland cement. The geopolymer concrete technology produces five times less CO2 compared to Portland cement [16,17,18]. Many attempts have been made to study and improve the properties of geopolymer cement. Liu et al [19] investigated the nano-mechanical properties of the geopolymer/cement matrix in recycled aggregate concrete. After the geopolymer cement is produced, its mechanical and chemical properties were investigated. The effect of curing temperature and Na2O/SiO2 ratio on mechanical properties and microstructure were studied
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