Strength properties of hexametaphosphate treated soils

The present technical note focuses on the potential application of sodium hexametaphosphate (HMP) in geo-environmental engineering. HMP may have many applications in geotechnical and geo-environmental engineering such as: improvement and stabilization of tailing dams, rehabilitation of old landfills, construction of new clay liners, containment and permeable barriers, etc. In this technical note, it is observed that the strength of silty-clayey sand containing a high concentration of metals (like tailings) is increased by mixing of HMP. On the other hand the strength of the kaolinite clay that may be used during the construction of a liner has been reduced by mixing with HMP. In order to study the influence of HMP, soil mixtures with various amount of HMP are prepared to conduct unconfined compression tests. The strength of the HMP-treated kaolinite specimens is always less than the kaolinite specimens for four weeks. HMP has decreased the strength of silty sand during the first days. However, the cations in the soil (specially Ca and Fe) may lead to precipitation and sorption mechanism to govern and, therefore, the strength increases noticeably up to 740%.