Investigation of mechanical properties of geopolymer concrete produced from locally available cementitious material - “Nech afer”

Abstract

Due to the rapid growth of infrastructure and the resulting increase in demand for construction materials, cement usage has also increased. However, cement production is a significant contributor to global carbon dioxide emissions, accounting for approximately 5% of the total. To promote sustainability in the construction industry, it is essential for experts in engineering and science to collaborate in developing and implementing eco-friendly building materials. The main objective of this research to investigate the mechanical properties of geopolymer concrete produced from locally available cementitious materials - ‘’Nech-Afer’’ and analysis failure mode of concrete. The study employed a geopolymer concrete mix design to determine the optimal superplasticizer, molarity, and curing temperature based on mortar trials. Six samples of geopolymer concrete were prepared, each with varying ratios of Na2SiO3 to NaOH of 2, 2.5, and 3 and replacement percentages of soil of 25%, 50%, and 75%. For each variable, three sets of specimens were created to test their compressive and split tensile strength at 7 and 28 days. A total of 120 specimens, including concrete cubes and cylinders, were prepared and cured for 7 and 28 days. To investigate the failure behavior of concrete under compressive load, a cubic specimen used for finite element model is created as an experimental setup. The results showed that using 14M and 2% of superplasticizer, along with a curing temperature of 80°C, resulted in a 17.27% increase over the control at a 75% replacement of Nech-afer in mortar after 7 days. It appears that the slump value of the concrete increases with an increase in the percentage of soil replacement, and also as the ratio of Na2SiO3 to NaOH increases, the workability of the concrete increase. This study found that the compressive strength of the alkali activated concrete is better than the control mix for all ratios of Na2SiO3 to NaOH and up to 50% of soil replacement at both the 7th and 28th-day ages. Additionally, the split tensile strength improved for all ratios of Na2SiO3 to NaOH at 25% of soil replacement at 7th and 28th-day ages. The combination of a 2.5 ratio of Na2SiO3 to NaOH and 50% of soil replacement resulted in the highest split tensile strength. These results suggest that the alkali-activated concrete (AAC) with 14M, a 2.5 ratio of Na2SiO3 to NaOH, 2% of superplasticizer, 80°C curing temperature and 50% of soil replacement is a suitable material for the construction industry. The investigation validated the experimental and finite element results is differentiated 6.7% respectively.