Modification of Cement Mortars by Polymeric Latexes and Their Use for Repairing Concrete
G. Mantegazza, A. M. Penn, and S. Tattoni
Appears on pages(s):
compressive strength; corrosion; cover; ductility; durability; flexural strength; latex; modulus of elasticity; mortars (material); permeability; repairs; workability; General
Reports the results of an experimental research program on polypropylene fiber reinforced cement mortars. The purpose of the work was to define the effects produced on a basic mortar by addition to the mixture of various synthetic polymers in the form of latexes. The significant features considered that characterize a cement mortar formulated for repairing concrete structures include workability, low permeability, dimensional stability, mechanical resistance (compressive and flexural strength), Young's modulus of elasticity, ductility, toughness, and durability. The test results suggest that optimal characteristics have been obtained (given a minimum percentage of fibers) with a content of 10 percent silica fume by weight of cement and by using acrylic acid copolymer water dispersion at the rate of 9 percent of the solid polymer to cement. For protective use, it is possible to modify the basic mortar by a styrene-butadiene copolymer water dispersion; however, the modification of the basic mortar by using styrene-acrylic polymer latex generates a product suitable either for repairing or coating of reinforced concrete structures. The reliability of this last modified mortar as a protective coating has also been investigated. The most significant results relate to the penetration of Cl- and SO 4-ions, variation of bond strength between mortar and concrete, and effectiveness of a thin layer of such a cement composite, correlated to rate of steel corrosion. Equivalent criteria have been described comparing different mortar covers, with the minimum cover thickness of concrete as prescribed by European codes, by using an electrochemical test procedure.