Splitting Tensile Strength Analysis of High-Strength Concrete Using Ureolytic Bacteria from Local Landfill as Microbial Self-Healing

Abstract

High-strength concrete is a brittle material due to its low tensile strength. Splitting tensile strength of concrete can be used to determine the concrete tensile capacity. High-strength concrete has high bearing capacity and good durability during its service life but excessive loads and extreme environmental influences can reduce its strength, thus, early maintenance is needed. Efforts that can be made are applying self-healing concrete using ureolytic bacteria obtained from local landfill Gampong Jawa, Banda Aceh, namely Bacillus sp. Splitting tensile strength test of concrete was carried out using cylindrical specimen with diameter 15 cm and height 30 cm. Bacillus sp. bacteria can produce calcium carbonate (CaCO3) as concrete crack-healing with the help of precursors, i.e., urea and Ca2+ ion along with nutrient broth as their nutrients. To ensure better bacterial viability, the bacteria along with their precursors and nutrients were encapsulated with diatomaceous earth and then coated with cement paste. Variations used are the concentration of bacteria along with their precursors and nutrients, i.e., 1.27%, 1.53%, and 1.79% from cement weight. To activate the CaCO3 formation by bacteria, the specimens were cracked first with a load of approximately 40% of its splitting tensile strength after being soaked in water for 7 days, then soaked again in water for 28 days for crack-healing before being tested. Splitting tensile strength analysis showed that the higher the concentration of Bacillus sp. bacteria, the greater the difference of splitting tensile strength between initial cracking load and after self-healing treatment, which indicates better crack-healing efficacy.