Sustainable stabilization of sabkha soil using recycled concrete waste and marble waste with cementitious binders: Strength, durability, and microstructural assessment

In arid regions, especially the Arabian Peninsula and the Middle East, sabkha soils present serious geotechnical issues due to their high soluble salt concentration, limited bearing capacity, and poor engineering qualities. It is therefore challenging to use sabkha soils as a base material or subgrade without first being treated. In view of this, there is the need to improve the stability of sabkha soils by means of waste utilization of waste materials such as recycled concrete waste (CW) and marble waste (MW). In this study, sabkha soils were replaced with CW and MW at proportions of 25%, 50%, and 100% of the dry weight of the soils with the addition of ordinary Portland cement (OPC) at ratios of 5% and 10% of the total dry mix weight. Similarly, the effect of adding metakaolin (MK) and gypsum (G) at 10% of the cement weight on the properties of the improved sabkha soils was determined for selected mixes. Evaluation of the samples was done via the UCS, CBR test, Proctor standard compaction test, and fragmentation durability tests in addition to the microscopic evaluation using X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was observed that as the substitution ratio increased, there was an increase in MDD but a reduction in OMC in the soil when it was replaced by concrete or marble waste. In addition, there was an increase in UCS when the sabkha soil was replaced with concrete or marble waste. It was observed that a mixture consisting of 25% concrete or marble waste with 5% ordinary Portland cement and 10% metakaolin had excellent mechanical properties, as it produced the highest UCS values, CBR value, and abrasion resistance. Moreover, this system successfully eliminated the negative effects of harmful mineral salts in the sabkha soil using concrete and marble waste treatment and cementitious binders. Therefore, it is concluded that the use of concrete and marble waste in sabkha soil, along with additional cementitious materials, is an ideal solution.