Development of fiber reinforced concrete repair materials

Abstract

Early age shrinkage cracking remains a critical concern for cement-based repairs and overlays. Fibers mitigate such cracking, but no standardized technique of assessing the performance of a given fiber exists. Recently, a novel technique of making such an assessment was developed at The University of British Columbia (UBC). In this test method, currently being balloted through the ASTM, an overlay of fiber reinforced concrete (FRC) material to be tested is cast directly on a fully matured sub-base with protuberances, and the entire assembly is subjected to controlled drying. Cracking in the overlay is then monitored and characterized. The technique was recently employed to develop "crack-free" overlay materials for two repair sites. One was a parking garage in Downtown Vancouver, British Columbia, and the other was the plaza deck at The UBC Aquatic Center. For the parking garage, a carbon fiber reinforced concrete and for the plaza deck, a cellulose fiber reinforced concrete were developed. Both overlays were instrumented with strain sensors and data were monitored over the Internet.Key words: fiber reinforced concrete, shrinkage cracking, strain monitoring, carbon fibers, cellulose fibers.