Durability of superhydrophobic engineered cementitious composites

Key elements of infrastructures throughout the United States are displaying poor durability, especially in northern regions where freeze-thaw damage is prevalent. One main factor leading to the early deterioration of concrete is related to the infiltration of water into the porous structure of the concrete matrix. To account for this, sealers or water repellant coatings are often applied on the surface of cementitious materials to reduce the ingress of water into the material. However, when the material develops micro-cracks, which is unavoidable, water can easily penetrate and saturate the bulk of the material. By incorporating a hydrophobic admixture within the concrete mix, water is restricted to enter the capillary voids and porous space, where, upon freezing, damage occurs. This type of modification is achieved in superhydrophobic engineered cementitious composites (SECC) designed with hydrophobic or superhydrophobic air voids evenly distributed throughout the cementitious matrix, providing effective protection against water infiltration. Moreover, SECC incorporates fiber reinforcement tuned to limit the crack opening. The reported research demonstrates the improved durability in fiber reinforced cementitious materials by creating a 3-dimensional hydrophobization to reduce the water absorption and permeability as well as to improve the freeze-thaw performance.