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Masters Theses in the Pure and Applied Sciences was first conceived, published, and disseminated by the Center for Information and Numerical Data Analysis and Synthesis (CINDAS)* at Purdue University in 1957, starting its coverage of theses with the academic year 1955. Beginning with Volume 13, the printing and dis semination phases of the activity were transferred to University Microfilms/Xerox of Ann Arbor, Michigan, with the thought that such an arrangement would be more beneficial to the academic and general scientific and technical community. After five years of this joint undertaking we had concluded that it was in the interest of all concerned if the printing and distribution of the volumes were handled by an international publishing house to assure improved service and broader dissemination. Hence, starting with Volume 18, Masters Theses in the Pure and Applied Sciences has been disseminated on a worldwide basis by Plenum Publishing Corporation of New York, and in the same year the coverage was broadened to include Canadian universities. All back issues can also be ordered from Plenum. We have reported in Volume 39 (thesis year 1994) a total of 13,953 thesis titles from 21 Canadian and 159 United States universities. We are sure that this broader base for these titles reported will greatly enhance the value of this impor tant annual reference work. While Volume 39 reports theses submitted in 1994, on occasion, certain uni versities do report theses submitted in previous years but not reported at the time.
Understanding the early age behavior of concrete is an important issue in construction of concrete structures since different factors during construction, such as design consideration, material usage, and environmental influence, can alter the original configuration of the structure intended by the engineers and hence the structure may experience and exhibit undesired consequences. The primary interest of this research was to model the behavior of concrete under environmental excitations, such as the variation of temperature and relative humidity, during the early age after concrete placement. Experimental test results were obtained and mathematical models were developed for this research. Modeling the effect of curing process in response to the relative humidity variation was one of the main objectives of this research. A mathematical model for back-calculating the diffusion coefficient of cured concrete from experimental test was proposed. This back-calculated diffusion coefficient of concrete was indicative of the effectiveness of curing application provided during construction. Corner deflection model for predicting lift-off displacement and climatic stress model for predicting crack formations were formulated in order to predict the distress behavior of concrete for a given design and construction scenario. Probabilistic models for lift-off displacement and cracking were formulated to predict the probabilities of such distresses. Material properties, such as strength, elastic modulus, creep, drying shrinkage, were obtained from experimental program and were used as input in these distress prediction models. In order to assess the effectiveness of different curing compounds, two indices, such as curing index and overall curing index, were proposed. These indices were able to distinguish the difference in performance among different curing compounds. For validating the proposed corner lift-off displacement model and climatic stress model, numerical simulations were performed and the obtained results were compared with the field observations. The probabilistic models for predicting lift-off displacement and cracking behavior were validated by comparing the numerical simulation results with the field observations at Houston Intercontinental, TX. The predictions from these models were found to be in close agreement with the experimental observations. Furthermore, in order to assess the impact of a given design and construction, analytical study was performed with these models. In the sensitivity analysis, parameters of interest were the geometry of the structure, the effect of curing application, and the influence of time as well as the season of construction on the distress potentials. Numerical simulations indicated that the curing application was able to lower the early age distress potentials. The thicker slabs/overlays versus the thinner ones exhibited differences in performance in terms of distress potentials. The analytical study also revealed that it was possible to vary the distress potentials by varying the time as well as the season of construction. Finally, a constructability index was proposed in order to assist in decision making with regard to different designs and construction scenarios with a view to minimize the distress potentials in concrete structure. The results indicated that the constructability index was able to capture and demonstrate the effect of different parameters mentioned above on the constructability of rigid pavement/overlay projects. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/152618
Restraint and intrinsic stresses in concrete at early ages are vitally important for concrete structures which must remain free of water-permeable cracks, such as water-retaining structures, tunnel linings, locks and dams. The development of hydration heat, stiffness and strength, also the degree of restraint and, especially for high-strength concrete, non-thermal effects, are decisive for sensitivity to cracking. Determining thses stresses in the laboratory and in construction components has led to a clearer understanding of how they develop and how to optimize mix design, temperature and curing conditions. New testing equipment has enabled the effects of all the important parameters to be qualified and more reliable models for predictiong restraint stresses to be developed. Thermal Cracking in Conrete at Early Ages contains 56 contributions by leading international specialists presented at the RILEM Symposium held in October 1994 at the Technical University of Munich. It will be valuable for construction and site engineers, concrete technologists and scientists.
This report describes the use of tables developed to help determine problems that may result from early thermal effects in concrete. The thermal behavior of concrete can be estimated from a knowledge of concrete temperature, air temperature, type of cement, and content of cement in the mixture. The thermal effects tables can be used to predict whether too high a temperature will be reached in the pavement; whether early thermal cracking will result from larger differences between the temperature of the concrete slab and the temperature of either the air or the base; or whether there is a risk of early cracking of the concrete. Examples of the use of the table are given along with guidelines for avoiding undesirable thermal effects.
This book provides a State of the Art Report (STAR) produced by RILEM Technical Committee 254-CMS ‘Thermal Cracking of Mas-sive Concrete Structures’. Several recent developments related to the old problem of understanding/predicting stresses originated from the evolution of the hydration of concrete are at the origin of the creation this technical committee. Having identified a lack in the organization of up-to-date scientific and technological knowledge about cracking induced by hydration heat effects, this STAR aims to provide both practitioners and scientists with a deep integrated overview of consolidated knowledge, together with recent developments on this subject.