The fabrication of Portland cement causes numerous problems accompanying the large exhaustion of gas. Even if fly ash, an industrial by-product produced in thermoelectric power plants, is recycled in concrete by partial replacing of cement, more than 50% remains still discharged in marine and ashore landfills and, continue to provoke environmental problems. Recently, active research has been dedicated to alkali-activated concrete that does not use cement as binder. This alkali-activated concrete as a cement zero concrete activated by alkali solution using bottom ash rich in Si and Al instead of cement is effective in reducing gas exhaustion. This study is a basic research for the fabrication of concrete without cement and using 100% of bottom ash among the industrial by-products. Therefore, the purposes are to develop cement zero concrete by evaluating the mechanical properties by age according to the change of the molar concentration and ratio (SH/SS) of the alkali-activator and the curing temperature, and to investigate the reaction mechanism. From the test results, the compressive strength increased with larger molar concentration and the optimal curing temperature was 60°C. In addition, the measurement of the leaching according to the molar concentration of fly ash having similar chemical composition showed that the leaching of Si4+ and Al3+ increased. Compared to 6M, the leached quantities of Si4+ and Al3+ were twice larger for 9M and 12M. The formation of gel at the surface of fly ash indicated that fly ash was more activated in higher alkaline environment.
Mechanical properties of alkali-activated concrete: A state-of-the-art review
