Abstract: Cement Deep mixing method applied in Lowland areas, is often set at W/C = 1.0. Also, W/C is determined based on empirical experience so far, and Engineers seem reluctant to increase the amount of water (w/c > 1). They have concerns over the possibility of insufficient mechanical strength of improved soil columns due to the amount of water. So, based on X-ray fluorescence data analysis instrument, our research is dealing with the evaluation of the chemical composition of elements responsible for soil-cement hardening on six specimens with parameters such as W/C ratio, the amount of cement C, the curing, and the mixing times. Then, the main components identified and quantified that interest us are silicon dioxide, calcium oxide, alumina, iron oxide and magnesium oxide. Especially about the amount of silica and calcium oxide which most influence the hardening process of the soil cement, we have the uniform tendencies of its percentage for W/C = 1.5 after 10min of mixing time and when the curing time becomes important (28 days). Then, combined with the strength 𝑞􀯨 distribution at 100 different points of each specimen, taken by needle penetration, the one with W/C = 1.5 and C = 110 kg/m3 is more uniform than the others. Finally, W/C = 1.0 is not the most effective ground improvement specification to consider when performing deep mixing treatment on cohesive soft soil such as Ariake clay.