ABSTRACT
This project is aimed at investigating the use of activated silicate based materials for the stabilization of rural road construction. Conventional stabilizers like the use of cement, lime, chemicals has been used in the past; also, pozzolanic materials like the slag, silica fumes, fly ash has also been used but when these materials are activated, they show more cementatious properties which enable them to fare better as stabilization materials.
The materials used include granulated Slag from Beta Glass Company and rice husk ash (RHA) with activators of (sodium silicate and sodium hydroxide) because of their availability, non toxic and non environmental effect. The activated materials and the Ordinary Portland Cement (as control) were used to stabilize the soil at different percentages of 0, 3, 6, 9 and 12% by mass of the dry soil. Laboratory tests which include compaction tests, Atterberg limit tests, California Bearing Ratio (soaked and unsoaked) and unconfined compressive strength tests UCS (up to 21days) were carried out on the stabilized soil.
The test results showed that the addition of the stabilizers to the natural soil produced an improvement in the mechanical and engineering properties of the soil as follow; the consistency tests performed showed that the liquid limits were enhanced to 39.62% from the natural 35.50% for Rice husk activated and similar results were seen for Ordinary Portland Cement that also increased to 39.16% whereas at 9% slag activated, it increased to 37.19%. The UCS characteristics of the soil after stabilization showed that the OPC increased in strength linearly to 2.34N/mm2 at 12% for 21days while for slag geopolymers, strength values increased up to 0.811N/mm² at 3% while Rice husk ash geopolymers obtained a peak value of 0.860N/mm² at 9%. The peak values recorded for both alkaline activated materials were lower than the conventional 1.72N/mm2 strength of cement stabilized base course soil as stipulated by Nigeria general specification (1997). But the minimum value of 0.687N/mm2 as specified by Ingles and Metcalf (1972), for sub base material; all the peak values of both materials met the requirement. In view of the CBR results obtained, 12% addition of slag geopolymers is recommended as the optimum amount strength gained at 37.21% and 35.31% for unsoaked and soaked CBR respectively (which is up to federal ministry of works specifications for sub base of 30%) compared to 15.44% of the natural sample. Clearly from the overall results recorded, it showed that both geopolymers can rival or substitute for cement stabilization at different percentage blending since there is significicant improvement on the properties of the soil as compared to the results of ordinary Portland cement OPC used as the control for the stabilization of the soil for a low traffic road pavement structural components construction.
