The effects of environment, materials and quality control on the physical properties of concrete

Abstract

In order to improve the current design and construction guidelines for a continuously reinforced concrete pavement (CRCP) that is maintenance free for at least 20 years, an extensive literature review and laboratory investigations for physical properties of concrete were performed. The tests conducted can be classified into three categories: strength tests, volume and weight changes, and other tests. The strength tests include compressive, pullout, flexural and modified compressive strength, and the volume and weight change tests include shrinkage and weight loss measurements of prisms and moisture content and moisture loss measurements of cubes. The other tests include time of setting test and abrasion resistance by sandblasting. The nine test parameters investigated in this study are divided into three categories: environmental factors, material variations, and quality control. The number of combinations of these parameters are too large to accomplish within a reasonable time. The total number of tests was therefore reduced to 116 based on typical materials used and environmental conditions encountered in Texas. An Evaporometer developed by the Texas State Department of Highways and Public Transportation was used to measure evaporation rates for several environmental conditions, and to combine the environmental factors such as air and concrete temperatures, relative humidity and wind speed into one variable. The results showed good correlations with a PCA chart within the ranges investigated and were found to be of great value in predicting most of the physical properties of concrete, such as strength development and shrinkage characteristics. Regression equations for strength and shrinkage as a function of evaporation rate, slump and age of concrete are provided for predicting the performance of CRC pavement. A new method of determining the degree of hydration of concrete based on moisture measurements was developed and tested in this study. The degree of hydration can be used for calculating the capillary porosity and gel/space ratio of concrete, both of which are very important parameters which affect the shrinkage and strength properties of concrete.