Workability and Crack Recovery Performance Investigation of IPDI Microcapsules–Based Self-Healing Cement Paste

Isophorone diisocyanate (IPDI) was encapsulated successfully within double-layered shells, and final microcapsules showed outstanding self-healing functions in cement paste. The well-dispersed microcapsules had a diameter of 347.0±103.4 μm, shell thickness of 3.1±0.4 μm, and core fraction around 74.8%±1.9% by weight. The diameters of microcapsules were adjustable by varying agitation rates. The beginning weight-loss temperature of microcapsules was 200°C, implying good thermal stability. The final microcapsules affected slightly the workability and setting time of fresh self-healing cement paste. Although the mechanical strength of hardened self-healing cement paste was decreased with the increase of microcapsule concentrations, the open porosity was improved obviously from 33.5% (control samples) to 31.8% when 5.0% by weight of microcapsules was introduced. The interfaces of microcapsules were compatible enough with cement paste without obvious delamination. Especially, the self-healing cement paste showed outstanding self-healing functions in open air when 10.0% by weight of microcapsules was introduced.