Effect of adding lime waste and sodium chloride on bentonite swelling behavior and infiltration rate

Abstract

Bentonite is artificial clayey soil that not only has the tendency to swell or increase in volume but also to shrink or decrease in volume due to variations in water content. In geotechnical engineering field, this soil causes severe damage to structures that are founded. The aim of this study is to investigate the effect of adding lime waste which is obtained from Abou Korkas sugarcane factory and sodium chloride on swelling properties of bentonite as a chemical stabilization process. In this regard, important techniques (SEM and EDX) were carried out to identify the mineralogy and microstructure variations before and after stabilization. Bentonite shows considerably different engineering behavior mainly depending on the mineralogical and chemical compositions. The results of the physical (geotechnical) tests indicated that lime waste and NaCl additives decreased the free swelling and increased the water infiltration of bentonite; the free swelling of the studied bentonite sample was 490% and free swelling for treated bentonite samples ranged between 250% and 370%, with an average of 297%. SEM and EDX analyses showed that all clay minerals are transformed to new flocculated cementitious compounds, such as calcium silicate hydrated (CSH) and calcium aluminate hydrated (CAH) so that bentonite texture is improved. The infiltration rate generally increases with either increase in salinity and electric conductivity; the values of infiltration rate were increased from 25 to 60 mm/h for the studied samples with an average value of 43.33 mm/h, due to reduction in clay content and a corresponding increase in the percentage of coarse particles. Utilization of solid wastes results in soil stabilization provides opportunity for cost savings in roadway construction, which will be of economic importance in developing countries.