Evaluation of laboratory and field techniques to improve portland cement concrete performance
This dissertation is presented as a compilation of five papers. Each paper is presented as a chapter in the dissertation and includes a short literature review, research data, significant findings, and references. A general conclusion section follows the main body of the dissertation and summarizes the significant findings and includes recommendations for further research.
The first paper presents a paste and concrete laboratory study investigating the two-stage mixing process and its effects on portland cement concrete mix consistency and concrete performance. In the paste study, mixing energy was varied to determine the effects on rheological and compressive strength properties. The concrete study investigated the two-stage mixing process and its effects on fresh and hardened concrete properties.
The second paper details a new characterization procedure for portland cement using the heat signature. A Type I/II portland cement was used to determine the effects of initial water and initial cement temperature on the heat signature of the paste. Several other portland cements, including blended cements, were also investigated to show the differences in cement chemistry when comparing the heat generation curves.
The third paper investigates the effects of differing air entraining agent, water reducing agents, and supplementary cementitious materials on the air void structure of fresh mortar samples. The air void analyzer was used to document the air void structure and identify anomalies or incompatible material combinations. Cubes were cast for compressive strength testing at seven days to show incompatible combinations in terms of retarded strength gain.
The fourth paper uses AVA data from a sixteen state pooled fund study to evaluate the AVA sampling locations. Samples were obtained from the slip formed concrete surface on vibrators and between vibrators from sixteen states. AVA samples were obtained before the paver on three states. Statistical analysis (t-test) was conducted at an alpha level of 0.05 to determine significance.
The fifth paper presents data on the heat signature of ternary mixes. The heat signatures were characterized and the results were modeled using slope 1 and slope 2, maximum temperature, time to maximum temperature, area under the heat signature curve, initial set, and final set.