Effect of 3-chloro-2-chloromethyl-1-propene modified polypropylene fibers on compressive strength performance in cementitious systems

Abstract

The service life of cementitious systems is reduced as a result of the different environmental effects to which it is exposed. In order to increase the performance of cementitious systems, chemical-mineral additives and fibers are added to the systems in question. While fibers absorb some of the stresses formed in the paste phase of the cementitious system, they transfer some of them to the more durable region of the matrix, limiting crack propagation. Various studies are carried out to increase the adhesion of fibers to the cementitious paste-fiber interface. The most common of these is to change the fiber shape and surface roughness with the help of mechanical processes. For example, improving the fiber-concrete matrix interface by hooking and bending processes is a widely preferred method. In this way, the bond strength can be significantly increased. However, these measures can reduce the stiffness of the fibers themselves. In addition, hooking and bending processes can be problematic in terms of their applicability to microfibers. In addition to physical modifications, chemical processes can also be performed to create a high-affinity fiber-matrix interface. In this study, surface modification was applied to the surface of 6 and 12 mm long polypropylene fibers with 3-Chloro-2-Chloromethyl-1-Propen chemical. In this context, mortar mixtures were prepared by changing modified and unmodified fibers by 0.5% of the aggregate volume. In all mortar mixtures, water/cement, sand/binder and spreading values were kept constant as 0.485, 2.75 and 200±20 mm, respectively. In order to provide the desired flow value, a single type of polycarboxylate-ether based high-level water-reducing additive was added to the mixtures at different rates. CEM I 42.5 R type cement and crushed limestone aggregate were used in all mixtures. According to the obtained results, adding fiber to the mixture and increasing the fiber length, regardless of the fiber type, increased the need for water-reducing additive for the target workability value. Surface activation of 3-chloro-2-chloromethyl-1-propene slightly improved the workability in short fibers, while no significant effect on spreading was observed in long fibers. Surface activation had no significant effect on compressive strength.