Assessment of alkali-induced heave in soil and its stabilisation using slag

Soil–alkali-interaction results in unexpected heaving and other negative effects of soil properties, which can lead to complete failure of structures. An investigation was carried out on the impact of highly concentrated sodium hydroxide alkali on the heaving behaviour of low-plasticity clay. The effect of ground-granulated blast-furnace slag as a stabiliser for alkali-interacted soil was also investigated. The interaction of alkali with the soil showed heaving up to 5.25% after 30 days, while a slag content of 20% showed maximum suppression of heave. The alkali-interacted soil stabilised with slag was also compared with un-interacted soil mixed with slag. There was a marginal increase in friction angle with an increase in curing period, and a significant increase in cohesion for both. A substantial improvement in unconfined compressive strength was also evident with increased slag content and curing period. The results were supported by microstructural examinations. The application of slag as a liquid-based stabiliser for alkali-interacted soil was also conducted using electrokinetics. Statistical analysis indicated that the curing period was a dominant parameter in affecting the compressive strength of un-interacted soil while, for alkali-interacted soil, slag content was more dominant.