Short-term creep and shrinkage strains were monitored at early age on hydrated Portland cement pastes prepared with two different water-cement ratios (0.35 and 0.50). Creep experiments were conducted in an environmentally controlled chamber maintained at (96 ± 2)% relative humidity. The three ages at loading investigated were 18, 24 and 30 hours. The stress-strength ratio applied to the specimens at the age of loading, using a miniature loading system, was 0.30. Cement paste specimens were in the form of "Tshaped" columns with a minimum thickness value (for the web and flanges) of less than 1.2 mm. Load-induced hydration (not normally considered in creep prediction) of normal strength cement paste (w/c=0.50) was found to occur at early times following the loading at 18 hours. An analytical model was developed in order to predict the creep coefficient of normal and high strength cement pastes from early age data. The model accounts for load-induced hydration effects.
The present study consists of investigating the carbonation resistance of two series of concrete mixtures designed for three classes of concrete (25, 35, and 45 MPa compressive strength at 28 d) and using American Society for Testing and Materials (ASTM) type I Portland cement and two commercially used fly ashes meeting the ASTM standards at the level of 20%, 35%, and 50% of the total weight of cementitious materials. The carbonation resistance was determined on samples moist cured for 3, 7, and 10 d and exposed to a CO2-enriched environment (3% CO2 at 23 °C and 65% relative humidity) for 140 d to accelerate the carbonation; it was also determined on samples moist cured for 7 d and exposed to an indoor and outdoor natural environments for 4 years. A mathematical model allowing the prediction of the depth of accelerated carbonation of fly ash concrete mixtures is presented.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.