OPTIMIZATION AND MODELLING OF RICE HUSK ASH-CLAY SOIL STABILIZATION

ABSTRACT

The over dependent on the utilization of industrially manufactured soil improving additives (cement, lime etc), have dept the cost of such stabilized soils financially high.  The hitherto have continued to deter the underdeveloped and poor nations of the world from providing accessible pavement to their rural dwellers who constitute the higher percentage of their population and are mostly, agriculturally dependent.  A number of researchers have studied the physical and chemical properties of rice husk ash.  The high percentage of siliceous material in rice husk ash indicates that it has potential pozzolonic properties.  Findings show that RHA which are waste materials can be used to upgrade expansive soil as a construction material.  Thus the use of agricultural waste (such as rice husk ash – RHA) will considerably reduce the cost of construction and as well reducing the environmental hazards they cause. However it appears that none of these studies referred to any guideliens in the binder selection process.  Thus, the study obtained the empirical models of soil material characteristics such as California Bearing Ratio (CBR), Optimum Moisture Content (OMC) and Maximum Dry Density (MDD), which are desirable for road construction.  The empirical models which are based on Scheffe’s optimization theory were developed from the experimental results of soils obtained from three different locations in south – eastern Nigeria.  The results show that A – 6 soil type improved to A – 2 – 6 after stabilization with RHA.  CBR value of the soil improves to an average of 14.47% from 5.67%.  Surprisingly, r the average value of the MDD reduces to 1.58kg/m3 from 1.89kg/m3.  While average OMC went up from 16.63% to 21.93%.  The empirical models show a very close result to the experimental results.  Since RHA is much cheaper than lime and cements, use of rice husk ash in soil stabilization can result in cost reduction in construction.