Index and Strength Properties of Rice Husk Ash Stabilized Laterite Soil Using Calcium Hydroxide and Sodium Silicate as Activators
1*Adedokun, S. I., 2Amoo, J. O. and 3 Nwaobasi, C. A…
1,2,3Civil and Environmental Engineering, University of Lagos, Lagos, Lagos State, Nigeria.
DOI: 10.36108/laujoces/6202.61.0232
Abstract
This paper examined the impact of alkali activator (calcium hydroxide and sodium silicate) and rice husk ash (RHA) on geotechnical features of A-7-6 (7) classified laterite soil. Soil samples were admixed with 0-15%RHA and 0-6% activator solution, containing Ca(OH)2 and Na2SiO3 in ratio 1:2, by dry weight of soil specimen. Chemical tests were carried out on the soil and RHA specimens to assess their oxide compositions. Atterberg limits, unconfined compressive strength (UCS) and statistical tests were conducted at 5% significant level to evaluate the influence of alkaline activation and RHA on soil properties. Results showed that the soil sample is a laterite with the Silica Sesquioxide Ratio (SSR) of 1.28 while the RHA is a class F pozzolan having the sum of silica, alumina and ferrite amounted to 80.96%. The liquid limit (LL) slightly increased with the addition of 15%RHA from 41.37 to 43.84%, but decreased to 37.36% as 6% activator was added to the soil. Conversely, the plasticity index (PI) increased from 16.37 to 31.79% when treated with 6% activator solution, but declined to 3.97% as 15%RHA was added. Adding 15%RHA to the soil enhanced the workability, leading to about 80% decline in plasticity. The UCS values at 28th day curing increased from 290 to1469 kN/m2 and 946 to 1663 kN/m2 under British Standard Light and Heavy compactions, respectively. The lower p-value of 9.31E-06 observed for activator showed the more significant impact of the activator in enhancing strength values of soil than the RHA that has a p-value of 1.01E-05. Findings revealed that the addition of activator and RHA improved the index and strength properties of the soil. The 4-6% activator addition that achieved a higher strength than the minimum UCS of 1500 kN/m2 specified for subbase course is thereby recommended for strength enhancement of the soil.
Keywords: Alkali activation, Geotechnical features, Rice husk ash, Laterite soil, Sodium silicate.