Goal 4 Long Life Pavement Rehabilitation Strategies-Rigid: Flexural Fatigue Life of Hydraulic Cement Concrete Beams

This document compares the results of flexural fatigue tests performed on experimental concrete beams made of the standard Caltrans concrete mix and five other fast-setting mixes. The three research objectives were: to investigate the fatigue characteristics of the fast-setting mixes, to compare the fatigue life of all the mixes tested, and to contrast this experiment's results with those of similar published studies. The experimental concrete samples included the standard Caltrans mix (using Portland cement type I/II) and five fast-setting mixes that used one of three cements: Portland cement type III, calcium sulfoaluminate, or calcium aluminate. Beams were fabricated from each mixture were used to determine the materials' flexural strength (or modulus of rupture) and fatigue life (or number of cycles to failure) at stress ratio levels of 0.70 and 0.85, and, in most cases 0.75. Three subsequent data analyses compared the number of cycles to failure of each mix at each stress ratio level, applied regression to compare the fatigue life of each fastsetting mix with the Caltrans standard mix, and applied regression to compare this study's results with common models for beam flexural fatigue life found in the literature. The study's main conclusions were: (a) fast-setting concrete mixes present similar or higher fatigue resistance than the standard Caltrans type, (b) at a stress ratio 0.70 all the mixes presented similar fatigue resistance, but at a stress ratio of 0.85 the Type III Portland cement mix displayed the longest fatigue life, and (c) linear regression curves generated by the tested mixes compared better to the "zero maintenance" model — the most common fatigue-life model used in concrete pavement engineering — than they did to the NCHRP 1-26 model.