Abstract: By-product materials like lime kiln dust(LKD),cement kiln dust,and fly ash are usually used to modify pavement subgrades.The behavior of soils modified with LKD was more complex than that with lime due to the presence of various compounds besides lime in LKD.The electrical conductivity behavior and the development of shear strength of LKD modified soils were described.The chemical processes were tracked with the variation of electrical conductivity of soil monitored by time domain reflectrometry(TDR) technology.Hyperbolic-type models were proposed to estimate the LKD dosage and to predict the development of shear strength with the variation of electrical conductivity.Compared with the conventional test methods,the use of TDR was expected to provide better understanding of the rate and extent of chemical reactions between chemical modifiers like LKD and soil and be useful for compaction quality control.