Soil improvement is one technique widely used to reduce the problem of geotechnical engineering project which construct on such soft clay. It is well know that soft clay have the poor engineering properties are low shear strength, low bearing capacity and high settlement [1]. The improvement method by soil stabilization was done by using stabilizer mixed with soft soil to improve undesirable properties of soft soil. The cementitious material was typically applied as stabilizers are ordinary portland cement (OPC) which is a general construction material, reasonable costs and readily available material in country. The studies revealed that the use of OPC as stabilizer in soil improvement effected to increased compressive strength, high bearing capacity and low settlement [2].
However, OPC was stilled valuable cost material and then an increase used of its consequence high cost of construction project. The feasibility idea to reduce used of OPC quantity by replaced with pozzolanic materials was studied by researchers [3,4]. The interesting one of pozzolanic materials is bagasse ash (BA). BA is a natural agricultural waste that generated by the production process of sugar factory. The raw bagasse was applied as fuel material in heating process and become ash after burnt. Office of the cane and sugar board of Thailand [5] reported an annual cane production in about of 104 million tons and 650,000 tons become ash approximately [6]. The studies revealed that the chemical composition of BA mainly consist of silica (SiO2), alumina (Al2O3) and ferric Oxide (Fe2O3) which can be used as pozzolanic material for partial cement replacement in concrete [7]. Due to the BA composition was differ in difference source, those studied was suggest investigating before used.
The application of BA in civil engineering work has been proposed by some researchers. The replacement of cement with 20%BA by dry weight was optimum content used in concrete which effected to increase in strength with curing time. The advantage of BA was to reduce the chloride diffusion by more than 50% without any adverse effects on other properties of the hardened concrete [8]. For special concrete, BA was ground for finely particle and then replace by cement to produce high strength concrete. It is found that the BA of 10–30% by dry weight affected to rise up strength, increase the resistance capability for chloride penetration and decrease porosity [9]. For construction material, the combination of clay and BA can be produce clay brick which present a similar property in order to compare with original clay brick. It is state that BA can be applied as a filler material for clay brick production consequence to reduce the natural raw materials by replace with waste residue [10]. In addition, the use of BA not only takes advantage of cement reduction which consequent to low construction cost but also mitigates the environmental problems by dusting and leaching from the storage area.
The main objective of the study was to determine the compressive strength of stabilized soil using OPC alone and partially replacement of OPC with BA. Based on compressive strength test, the optimum ratio by BA replacement was purposed. The strength development of stabilized soil was investigated with curing time and changes on stabilized soil structure were observed using scanning electron microscopy (SEM).