Deep Soil Mix (DSM) is a proven method of ground improvement for deeper underlying soft soil layers which are otherwise impractical to reach using conventional shallow soil stabilization and replacement methods. The predominant binder materials used are Ordinary Portland cement (OPC) and Lime (CaO) but negative effects to the environment from manufacture and increasing construction cost have prompted research into alternative materials. This review identifies pozzolans and filler materials as possible supplements or partial substitutes for better results. The DSM method and binder reaction processes during treated soil strength development are outlined and effectiveness of different pozzolans (Fly Ash, Silica Fume, Ground Granulated Blast Furnace Slag, Rice Husk Ash, Kaolin, and Metakaolin) and filler materials (e.g. fine sand) discussed together with their influence factors. With many pozzolans, a clear optimum dosage is observed where improved strength peaks. Aluminosilicate pozzolans perform better over siliceous pozzolans with Metakaolin (MK) identified as the most effective pozzolan for enhancing compressive strength. Up to date research results on these materials are compiled. MK blended cements are readily available and can be readily applied for initial field tests. Treated soil strength may be regulated with addition of filler materials to further reduce reliance on cement.

Ordinary Portland Cement (OPC) and Lime (CaO) have traditionally been used as binder materials for Deep Soil Mix (DSM) ground improvement. Research has been conducted into possible alternatives such as pozzolans to reduce reliance on either cement or lime. However, pozzolans still undergo similar calcium-based reactions in the strengthening process. In this review, further alternative binder materials for soil strength development are explored. These recent developments include fiber reinforcement materials, alkali activation methods, nanomaterials and geopolymers, which can potentially achieve equal or improved performance. Research to date has shown that alkali-activated materials and geopolymers can be equivalent or superior alternatives to pozzolanic supplemented cement binders. The case is made for GP cements which potentially produces 80% less CO2 than conventional portland cement during manufacture. One-part AAM and GP cements are a promising substitute for portland cement in DSM. A combined approach which incorporates both Ca and alkali activated/geopolymer types of materials and hence reactions is proposed.

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