Effects of Poly(vinyl alcohol) on Fiber Cement Interfaces. Part I: Bond Stress-Slip Response

This is the first part of a two-part article describing the effects of The addition of polymers to a cement matrix can add adding poly(vinyl alcohol) (PVA) to a cement based matrix to irasignificantly to the magnitude of the "adhesion" comprove the bond at the fiber-matrix interface. Two types of fibers were ponent of bond at the fiber-matrix interface. For examused, steel and brass fibers (simulating brass-coated steel fibers) in ple, Wei et al. [7,8] found that the pull-out force of a a series of pull-out tests where the load versus global slip up to fiber was almost quadrupled by adding 15% by weight complete pull-out was recorded. The measured slip was that at the of cement of a water-dispersion of acrylic polymer parsection where the fiber penetrates the matrix. The first article deticles. This improvement was suggested to arise from scribes the mechanical effects of the addition of PVA, while the the small size (50 to 100 nm) of the acrylic polymer second article presents the microscopic observations. Correlation beparticles which, being smaller than the cement partitween the two studies is pointed out in the second part and conclucles, are able to fill in the porous zone that typically sions are drawn. In particular, it is observed that the addition of surrounds the fibers. In the work described here, a PVA in the amount of 1.4% by weight of cement matrix leads to a water-soluble polymer, poly(vinyl alcohol) (PVA), was significant improvement in the bond strength as well as in the used. This polymer is dispersed as molecules which frictional resistance, thus pull-out work, after the peak load. ADare orders of magnitude smaller than particles, and the VANCED CEMENT BASED MATERIALS 1994, 1, 115--121 question to be answered is whether a much smaller