Swelling behavior of kaolinitic clays contaminated with alkali solutions: A micro-level study

Abstract

Alkali contamination of soils results in repeated structural failure when exposed. Though the effects of alkali on different soils have been investigated in recent years, a systematic research approach aimed at establishing swell behavior in non-swelling kaolinitic clays when exposed continuously with varying concentrations of alkali solution as pore fluid and its micro-level investigation is not well documented. Series of one-dimensional free swell tests and micro-level studies (XRD, SEM) have been carried out to investigate the alkali induced swell in non-swelling kaolinitic clays. Naturally available red earth and two commercial clays, namely ball clay and china clay, which predominantly contains kaolinite mineral are selected for the study. The swell test results showed that all three clays exhibited high swelling with alkali solutions (0.1N, 1N, 4N, 8N) when compared with water. The magnitude of swell observed in clays interacted with alkali solution ranged from a minimum of 8% to maximum of 56% depending upon the concentrations exposed. China clay showed a minimum swell of 8% with 8N alkali solution to a maximum swell of 22% with 4N alkali solution and red earth showed a minimum swell of 18% with 8N alkali solution to a maximum of 27% with 0.1N alkali solution. Whereas, ball clay showed a minimum swell of 12% with 0.1N alkali solution and maximum swell of 56% with 8N alkali solution. The resulted magnitude of alkali induced swell in clays is attributed to dispersion of clay particles and new mineral formations. To explore the formation of new minerals and morphological transformations a micro-level investigation is carried out on representative samples collected at the end of free swell tests. The formation of zeolite minerals viz. sodalite and cancrinite were evidenced from XRD results and rosette type structures were observed from SEM studies.