Effect of polypropylene fiber and expansion agent on plastic shrinkage cracking property of cement mortar
The effects of polypropylene fiber content, fiber length and expansion agent on the plastic shrinkage cracking properties of cement mortar were studied. The results show that the plastic cracking resistance of cement mortar increases with the increase of fiber content. The longer the fiber length is, the greater the plastic cracking resistance of cement mortar is. When the fiber content is low (0.05%), the expansion agent has a better effect on controlling the plastic crack of mortar than the fiber content (0.15%). The superposition effect of polypropylene fiber and expansion agent is better under suitable conditions.
Since the existence of cement concrete, the crack problem has not been completely solved, and has become a hot spot of great concern. There are two basic technical routes to solve the problem of concrete cracks in China: one is to add expansion agent to prepare expansive concrete, and the other is to add synthetic fiber to prepare synthetic fiber concrete. Many projects using expansive concrete have successfully solved the problem of concrete cracking, but some projects have not been successfully solved, mainly because expansive concrete has a certain range of application and use conditions, and the need for more strict maintenance measures, otherwise not only can not crack, but may make concrete cracks. For the second method, its research and engineering practice are relatively lagging behind, but in recent years, it has developed rapidly, more and more applications in engineering, there are many successful examples, of course, some people have questioned its cracking resistance.
At present, the international consensus is that fiber concrete is an effective way to improve the crack resistance and toughness of concrete, especially polypropylene fiber has a very unique role in solving the early plastic cracking of concrete and reducing the drying shrinkage deformation of concrete. There are tens of millions of polypropylene fibers distributed in each cubic cube of concrete, forming a three-dimensional powerful spatial support system, improving the internal quality of concrete, making concrete permeability resistance, crack resistance, toughness, impact resistance, fatigue resistance, impact resistance and other properties have been significantly improved, extending the service life of the structure.
