| Recently, a 3-year research study to further investigate the effects of time and temperature on various early-age concrete properties was awarded by the National Science Foundation. The environment of which concrete is cured contains several variables including: temperature, relative humidity, wind, and solar radiation. Each of these factors can affect properties of concrete such as strength, durability, shrinkage, and creep. Out of these factors, the ambient curing temperature is probably the most important factor in terms of affecting the strength development of concrete. Therefore, the concrete maturity method is used to study the affects of time and temperature on ultimate strength. Nurse and Saul proposed a maturity function using the product of time and temperature in early 1950s. Afterward, Freiesleben Hansen and Pedersen developed a new method of maturity concept using Arrhenius equation in 1977. In a relatively recent study, Tank and Carino made the previous equations simpler in order to easily apply the maturity method to construction field situations. However, each of these functions has inherent limitations. As a result the purpose of this research is to develop an improved function that reduces or eliminates the main limitation which is the effects of early age temperature on the long-term ultimate strength. Therefore, laboratory experiments using various temperatures were completed before developing the model. In this research, variable curing temperatures were selected to simulate the field condition of mass concrete curing and to study how this temperature affects strength development of concrete. This dissertation focuses on studying the characteristics of concrete at early age and how the early age temperature affects long-term strength on a maturity function. Both normal and high performance concretes were utilized. |
