Expansive fiber crack-resistant waterproofing agent (referred to as "fiber expanding agent") is powder, which is based on ordinary crack-resistant waterproofing agent, adding polypropylene fiber, so that the tensile strength, toughness, impermeability, crack resistance of concrete can be significantly improved; the micro-cracks caused by the factors such as solid-plastic shrinkage, drying shrinkage and temperature change in concrete or mortar can be reduced, and the concrete can be greatly improved. Fracture resistance, impermeability, impact resistance and seismic resistance. This product is made of sulphoaluminate micro-expansion agent, polypropylene fiber, waterproofing agent and other organic and inorganic materials. It is widely used in underground anti-cracking and waterproofing engineering, super-long structure engineering, civil air defense engineering, highway pavement, tunnel, port, waterworks, power plants, reservoir dams, military engineering with special anti-seepage and anti-explosion.

During the hardening process of cement concrete, the volume of concrete shrinks due to the reaction of cement and hydrate. In the later period, the shrinkage is caused by the evaporation of free water in concrete. These shrinkage stresses exceed the tensile strength of cement matrix, and micro-cracks will occur in concrete. The development of micro cracks is about 70% during the 3-7d gel period, when the tensile strength of concrete is less than 1Mpa. After adding expansion fiber anti-cracking waterproofing agent into concrete, anti-cracking waterproofing agent can compensate for drying shrinkage and cold shrinkage of concrete during hardening process. Fibers are evenly dispersed in concrete to form a chaotic support system, which disperses the directional stress of concrete, prevents the occurrence and development of early concrete plastic cracks, greatly improves the anti-seepage ability of concrete cracks, and improves concrete quality. Toughness, thereby prolonging the service life of concrete. In addition, because the fiber itself has a certain strength, the fiber evenly disperses in the concrete and forms the anchorage function, which can absorb certain destructive energy instantaneously, and help to reduce the concrete plastic shrinkage and stress during freeze-thaw. At the same time, the addition of numerous fiber monofilaments can effectively hinder the segregation of aggregates, ensure the early uniform water release of concrete, thus reducing the formation of settlement cracks.