AN INVESTIGATION ON THE DETERMINATION OF THE COMPRESSIVE STRENGTH OF META-KAOLIN BASED GEOPOLYMER CONCRETE UNDER DIFFERENT CURING CONDITIONS

ABSTRACT

Cement is a well-known binding material indispensably place in construction works. Production and consumption of cement is an index of industrial development but excess of production of cement pollute the environment by releasing CO2 gas. Due to the carbon dioxide emission arising from the production of cement, alternative concrete that is environmentally friendly such as metakaolin geopolymer concrete have been developed. However, the performance of metakaolin based geopolymer concrete (MKGC) when exposed to aggressive environment particularly sunlight, oven (elevated temperature), room temperature and calcium hydroxide has not been investigated. In that regard, this project focuses on the effect of various curing conditions (oven, sunlight, room temperature and calcium hydroxide) on the compressive and split-tensile strength of metakaolinbased geopolymer concrete. And the main goal of this project report is assessed the performance of metakaolin based geopolymer concrete (MKGC) when subjected to the four curing conditions as mentioned above. Cylindrical MKGC cube specimens of grade 25 were prepared using a mix ratio of 1:1.6:3.7 with a diameter of 5cm and 10cm height. After preparing the specimens, they were placed in an electric oven at a temperature of 60oC for 6 hours. Thereafter, the specimens were stored in the laboratory at ambient temperature for 7 days. A control specimen was cured at room temperature. Some tests were performed for calcium hydroxide. And the influence of Ca(OH)2 concentration (8 and 12 M) and curing conditions as oven temperature (40 ̊C and 60 ̊C), time (12 and 6 hours) and sunlight on compressive strength of metakaolin-based geopolymer (MKGC) was evaluated. After the exposure of the specimens to elevated temperature (100oC for 4 hours), alkalinity (calcium hydroxide), and sunlight, it shows that the ratio of split-tensile to compressive strength was about 10% when 1% Ca(OH)2 was applied. The results reveal that, the best performance conditions of geopolymerization of metakaolin based concrete in other to develop a higher compressive strength of 20MPa are; 12M Ca(OH)2 and 60°C at 7 curing days under sunlight. With these conditions, the results also indicate that this type of concrete has high rate of hardening, where it is possible to gain more than 80% of the 14days strength at 7days ages when using optimal temperature curing.