Screening Nigerian Kaolin for Use as Potential Sources of Geopolymer Materials

Abstract

The search for alternative low cost and environment friendly binder has led to the screening of Nigerian kaolinite clay for the production of geopolymer binders. Three batches of geopolymer binders were synthesised using five Nigerian kaolinite clays, locally synthesised sodium silicate and NaOH. The clays were Ikere Ekiti (Ekiti State) kaolin, Ikare (Ondo State) kaolin, fired clay (Ozubulu, Imo state), Enugu (Enugu state) kaolin, and laterite (Lagos State).The first batch was activated with sodium silicate and water in ratio one to one. The second batch was activated with sodium silicate and water in ratio one to half and the last batch was activated with sodium silicate and sodium hydroxide in ratio one to one. Six mixes for each sample were prepared for the first and second batches of geopolymer binder. They were cured at room temperature for seven days, 75oC, 150oC and 500oC. The last batch of the geopolymer binder was cured at 150oC. The result of the research confirmed that compressive strength of kaolinite clay based geopolymer binder increased with increase in curing time from 7 days room temperature to 500oC. All geopolymers activated with both sodium silicate and sodium hydroxide demonstrated sharp increase in their compressive strength values when compare with geopolymer activated with sodium silicate and water. Comparing the geopolymers activated with both sodium silicate and NaOH in ratio one to one with ASTM Specification Standard, Ikare sample satisfied ASTM Specification Standard C62 and C90. Similarly, Ikere Ekiti geopolymer satisfied ASTM Specification Standard C62, C90, C216, and C902. Water absorption test performed showed that all the samples have good water absorption capacity at different conditions when compared with ASTM Specification Standard for water absorption, except Enugu kaolin and Ozubulu clay which did not satisfied the ASTM requirements at room temperature and at 75oC. Nigerian kaolinite clays have potentials to be used as geopolymer binders which may be applied in construction.