Alkaleri Metakaolin Powder Performance Evaluation by Response Surface Method.

Alkaleri metakaolin (AMK) based geopolymer binder has been identified as one of the alternatives to the Ordinary Portland Cement (OPC), which qualifies the criteria for green construction material. In this work, 20No of experimental mix proportions (RUNs) were designed by Central Composite Design (CDD) of Response Surface Method (RSM). Mixture of AMK and Alkaline Solution was heated for 45mins at 60oc with stirring interval of 15mins, after which aggregates were added to the hot mix. 60No of 100X100X100mm cubes were cast. Samples were tested at the 28th day of ambient curing. The reported Compressive Strengths are the average of the 60 sample tested with 38.6N/mm2 as the maximum, hence established the experimental optimum mix proportion (EOMP). The ANOVA model developed statistically validated by having F-value of 15.54 and P-value of less than 0.0001 indicating that the model is statistically significant. Also, the adequate precision of 10.7850 which is greater than 4.00 indicates adequate signal and desirable. Furthermore, the difference between predicted R2 and adjusted R2 is less than 0.2 testifying that they are rationally in good agreement. Effects of three principal variables namely: molarity of sodium hydroxide, sodium silicate to sodium hydroxide ratio, and fineness (particle size) on the properties of the fresh and hardened AMK geopolymer concrete (normal consistency, soundness, setting times, slump, dry density, water absorption, compressive strength, flexural strength, split tensile strength, sorptivity and acid attack) were investigated. All the results for the properties investigated were found to have fallen within the ranges of the international standard codes such as ASTM and British Standard, hence AMK is qualify to be used as Metakaolin based geopolymer binder.