Investigation of concrete strength made with nanoparticles and metakaolin in acid and sulphate solution

Abstract

The investigation of concrete strength with nanoparticles and metakaolin in acid and sulphate solutions was the aim of this study. The nanoparticles were obtained from rice husk through sol-gel method and beneficiated metakaolin from kaolin to replace cement in concrete. The compressive strength results at 56 days were computed for various mixes. From the results, mix number 5 (1%NS 20%MK), 10(2%NS 15%MK) and 15(3%NS 10%MK) had the highest compressive strength of 39.36N/mm2, 40.20N/mm2 and 41.78N/mm2 showed the most strength development at 28days respectively. This is 10.7%, 9.8% and 14.8% strength increment over the control sample. The water absorption test of the concrete samples revealed that mix number 10 had the least water absorption at 69% less than the control sample. After 28days of 5% sulphuric acid and 5% agnesium sulphate immersion, mix number 10 also showed a compressive strength reduction by 9.7% and .2% more than the compressive strength before immersion. The sample with no additive was found to have 30.8% and 23.8% compressive strength reduction more than the compressive strength before immersion. The scanning electron microscopy (SEM) of the samples showed that, mix 10 had a more compact, homogenous and dense structure after 28days of immersion which explains the high strength. Energy Dispersion X-ray spectroscopy (EDS) also showed that the Ca/Si of mix 10 which was 0.83 and 0.65 after 28days of immersion in acidic and sulphate solutions respectively was within the range of optimal performance of concrete. X-ray diffraction analysis showed the development of ettringite, gypsum and silica gel as a result of the disintegration and reaction of the chemicals with hardened material.