|
| Improvement method | Modifier | Cost analysis | Effect analysis |
|
| Physical | 1. Weathered sand | The cost of physical improvement is lower than that of chemical improvement. | Sand particles have certain hardness and particle size, and the mixing difficulty of sand in expansive soil is obviously less than that of lime, cement, fly ash, and other fine materials in expansive soil. Mixing sand with expansive soil can effectively improve the shear strength of expansive soil, reduce the cohesion of soil, increase the internal friction angle, and reduce soil swelling characteristics; however, physical improvement is slow and inefficient compared to chemical improvement. |
| 2. Fine silica sand |
| 3. Sandy soil and marble waste |
| 4. Sand and expanded polystyrene (EPS) |
| 5. Disintegrated sandy soft rock |
|
| Chemical | 1. A mixture of activated fly ash (α -FA) and sisal fibres into expansive soil | Lime and cement are resource materials, and the cost of these materials as stabilizing materials is higher than that of industrial waste such as fly ash and alkali slag; the cost of some admixtures is relatively low, such as ES-SSP-C-N. In all of the improvement methods, the chemical improvement technology is the most costly, but its treatment effect is the best. | The greatest advantage of chemical improvement is that it can improve the bad engineering properties of expansive soil in essence, and theoretically eliminate the expansion and contraction of expansive soil. It is a hot field in the engineering treatment technology of expansive soil at home and abroad and is widely used. |
| 2. Slaked lime and fly ash |
| 3. Admixture consisting of fly ash and ground granulated blast furnace slag and lime |
| 4. Slag added into the type I/II Portland cement |
| 5. NaCl solutions |
| 6. Admixtures consisting of expansive soil, cement, steel slag powder, and NaOH (ES-SSP-C-N) |
| 7. Paraffin-based liquid phase change material (pPCM) and paraffin-based microcapsule phase change material (mPCM) |
|
| Biological | 1. Put bacteria into the vegetable garden soil, and put moulds and actinomycetes into the organic matter to make solid bacteria, respectively | The sustainable environmental benefits attributed to the improvement achieved with biopolymers far exceed those of traditional stabilizers. These methods also exhibit ecological, safe, and economical characteristics. However, this technology is not mature enough for practical application. | Biological metabolic activities can promote the cementation of soil particles, and microbial corpses can also be used as inter particle fillers. Theoretically, it is one of the effective methods to improve expansive soil by microorganism, but microbial improvement of expansive soils requires systematic and complex projects; this approach is still at the stage of theoretical analysis and experimental research. |
| 2. Biological enzymes |
| 3. Guar gum biopolymer |
| 4. Oyster powder |
|
| Solid waste | 1. Phosphorus tailings | The treatment cost of solid waste is reduced, and the cost of expansive soil treatment is low. However, the improvement effect is also poor. | A successful case of “treating waste with waste” that reduces the pollution of solid waste to the environment and achieves resource utilization of solid waste. The modification effect of expansive soil is good, which can effectively improve the fissure property and strength of expansive soil, reduce the expansion potential and plasticity index, and improve the road performance of expansive soil subgrade. |
| 2. Iron tailings sand |
| 3. Waste rubber tires |
| 4. Glass fibres combined with epoxy |
| 5. Resin, polypropylene fibres |
| 6. Quarry dust, cement bypass dust (CBPD) |
| 7. Calcium lignosulfonate (CLS) |
| 8. Sand-grade recycled glass (RG) |
|
