Flowability and density characteristics of controlled low-strength material using native high-plasticity clay

In pipeline construction projects when high-plasticity clayey soils are encountered in the excavated trench material, they are typically landfilled and better quality materials are imported from outside quarry sources for use as bedding and haunch-zone materials. This practice has detrimental environmental and cost impacts; therefore, an efficient reutilization of this high-plasticity excavated material to produce controlled low-strength materials (CLSMs) to use as bedding and haunch-zone materials will have major sustainability benefits. As part of an ongoing research study, novel CLSM mix designs were developed by utilizing native high-plasticity clayey soils from the excavated trench material. Due to the high-plasticity nature of the soils, it is essential to address both flowability and density property requirements prior to validating them against other engineering properties. Hence, several CLSM mixtures with the native clayey soils as ingredients were initially designed as per a flowability criterion to establish the optimum quantities of chemical binders and water quantities. Later, these mixes were verified for satisfying a density property criterion. This technical note presents the step-by-step procedure followed in preparing these mixes along with test results obtained from various mixes designed as part of the testing program. Based on these results, it was evident that CLSM mixes with high-plasticity clays can be developed that meet both flowability and density criteria. The success of this research enhances sustainability efforts in pipeline construction projects because this study showed that excavated clayey soils can be successfully reused in CLSM applications rather than landfilling them.