Laboratory TDR monitoring of physico-chemical process in lime kiln dust stabilized clayey soils

By-product materials like lime kiln dust(LKD) and cement kiln dust(CKD) begin to be used in the highways and airfield subgrades for improving natural soils to make them suitable construction materials.Most often,dry density and water content are measured in the field for the quality control purposes.Due to the complex physico-chemical reactions in the mixture,the maximum dry density and the optimum water content of the stabilized soils are always quite different from those of natural soil,which make it difficult to evaluate the quality of the stabilized soil.The physico-chemical process in LKD stabilized soil resulted in the change of the electromagnetic properties,which could be monitored by robust,automated,time domain reflectrometry(TDR) technology.LKD stabilized orchard clay with different dosages of LKD and water content were compacted in standard molds.The electrical conductivity and apparent dielectric constant were monitored by TDR to investigate the physico-chemical processes.Needle penetrometer tests were also done on replicate samples at different curing time.It was found that the variation of electrical conductivity and apparent dielectric constant with time was an indicator of short-term cation exchange and agglomeration and long-term pozzolanic reactions.The decrease of electrical conductivity with time coincided with the increase of the penetrometer resistance.The initial(less than one day) reduction of conductivity was strongly related to the dosage of LKD,while the long term reduction was related to the strength development.The paper presented the potential applications of TDR technology to the LKD stabilized soil in the field quality control.