Deep Soil Mixed Piles with Microcapsule-Based Self-Healing Grout

Deep soil mixing piling involves the use of augers, through which a grout is injected and mixed with soil, forming soil-grout columns. A recent development to the grouts in deep soil mixed piles has been the application of the concept of self-healing materials, that can be triggered by damage and self-heal without the need for external intervention. This concept would be particularly valuable for piling applications, many of which are inaccessible, are installed in aggressive environments or are prohibitively expensive to maintain. The authors are part of a large leading national consortium developing biomimetic materials for infrastructure through EPSRC funding of a programme grant: Resilient Materials for Life (2017-2022, £5M). The Cambridge team has been developing microcapsule-based self-healing systems for cementitious grouts. The self-healing grout incorporating microcapsules was mixed with soil using a laboratory-scale model pile mixing apparatus. The microcapsules embedded in the soil-cement matrix are triggered by damage and releasing the healing agent that repairs the damage. The effective self-healing of cracks was verified by the recovered permeability of microcapsule-containing model piles. Properties investigated were the distribution and rupture of microcapsules, and microstructure of the deep soil mixed model piles by CT scan and scanning electron microscopy analysis.