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.
AbstractWith the current demand for portland cement concrete (PCC) sustainability, supplementary cementitious materials (SCMs) are often used in concrete mixtures to improve the mixture properties in ...both fresh and hardened concrete. In this research, sixteen concrete mixtures (one control mixture, three binary mixtures, and twelve ternary mixtures) with various combinations of fly ash, slag, and portland cement were fabricated. The thermal and mechanical properties of the selected ternary mixtures were measured at various ages, and the critical temperature gradient through the slab thickness was generated by using the enhanced integrated climatic model (EICM). By using the measured mechanical properties, nonlinear temperature gradients obtained from EICM, and CTE gradients throughout the slab thickness, Westergaard-Bradbury solution was used to calculate the critical tensile stress on the PCC pavements. The analysis results show that all the ternary mixtures with the replacement of 30% slag and 30% fly ash, and replacement of 50% slag and 20% fly ash did not exceed 100% tensile stress-to-strength ratio at all ages.
Celotno besedilo
Dostopno za:
DOBA, FGGLJ, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Wanting to be thinner Wu, Zhong; Rupnow, Tyson
Roads & bridges,
01/2018
Magazine Article
As a durable, economical and low-maintenance concrete material, roller-compacted concrete (RCC) is steadily becoming the choice for many pavement applications. And researchers in Louisiana are ...testing just how thin those applications can go. Spearheaded by Louisiana Transportation Research Center’s (LTRC) Zhong Wu and Tyson Rupnow, researchers launched a study titled, "Performance of Thin RCC Pavements Under Accelerated Loading". Overall, the results showed that a thin RCC over soil cement-pavement structure has a superior load-carrying capability. The 6-in RCC sections carried an estimated 87.4 million and 19.4 million equivalent single axle load to failure for the strong and weak base, respectively. By using a thin RCC in lieu of an HMA layer for a low-volume pavement where heavy or overloaded trucks frequently travel in Louisiana, not only can it be cost-effective in construction, but it also could potentially extend pavement service life with less of a maintenance need.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
