Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains x, 131 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 114-117).

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

<p>The purpose of work was to show properties of concrete modified with wooden fibres and to compare whem with unmodified concrete in order to show influence of these wooden fibres on chosen properties and to check if using of these types of admixtures is benificial in economical and technical point of view.</p>

Thermal distress in asphalt concrete pavements is a widespread problem around the world. Thermal cracking can be divided into two modes of distress: low temperature cracking and thermal fatigue cracking. Low temperature cracking results from extremely cold temperatures; thermal fatigue cracking results from daily temperature cycles. Low temperature cracking is attributed to tensile stresses induced in the asphalt concrete pavement as the temperature drops to an extremely low temperature. If the pavement is cooled, tensile stresses develop as a result of the pavement's tendency to contract. The friction between the pavement and the base layer resists the contraction. If the tensile stress equals the strength of the mixture at that temperature, a micro-crack develops at the surface of the pavement. Under repeated temperature cycles, the crack penetrates the full depth and across the asphalt concrete layer. The thermal stress restrained specimen test (TSRST) was identified as an accelerated laboratory test to evaluate the thermal cracking resistance of asphalt concrete mixtures. The TSRST system developed at OSU includes a load system, data control/acquisition system and software, temperature control system, and specimen alignment stand. The overall system is controlled by a personal computer. A TSRST is conducted by cooling an asphalt concrete specimen at a specified rate while monitoring the specimen at constant length. A typical thermally-induced stress curve is divided into two parts: relaxation and non-relaxation. The temperature at which the curve is divided into two parts is termed the transition temperature. The temperature at fracture is termed the fracture temperature and the maximum stress is the fracture strength. An extensive number of TSRSTs over a wide range of conditions were performed to investigate the thermal cracking resistance of asphalt concrete mixtures. The TSRST results provided a very strong indication of low temperature cracking resistance for all mixtures considered. A ranking of mixtures for low temperature cracking resistance based on the TSRST fracture temperature was in excellent agreement with a ranking based on the physical properties of the asphalt cements. It is highly recommended that the TSRST be used in mix evaluation to identify low temperature cracking resistance of asphalt concrete mixtures. The TSRST showed very promising results regarding the effect of all variables which are currently considered to affect the low temperature cracking of mixtures. The variables considered to have significant affect on the low temperature cracking resistance of mixtures in this study include asphalt type, aggregate type, degree of aging, cooling rate, and stress relaxation. / Graduation date: 1994

Concrete structures deteriorate in their operating environment under the combined action of harsh environmental conditions and external loading. Although the applied load can lead to a certain degradation of the structure, the main long-term deterioration mechanism involves moisture movement and the transport of chlorides within concrete. In order to build durable and reliable structures, it is necessary to be able to accurately predict the movement of moisture and chlorides within concrete.<p> In the case of unsaturated concrete, the transport of chloride ions is integrally associated with prediction of moisture fluxes in concrete. Even the diffusion of chloride ions depends on the degree of saturation of the concrete since concrete must have a continuous liquid phase for diffusion to occur. Therefore, simple diffusion theory, used in the current literature, is not sufficient to predict the diffusion of chloride ions in the case of unsaturated concrete. Most diffusion models described in the current published literature are applicable to concrete structures that are permanently wet and invariably underestimate the amount of chlorides penetrating the concrete of structures subjected to wetting and drying cycles. The research presented in this thesis reviews current knowledge, mathematical models and test methods pertinent to the movement of moisture and transport of chloride ions in unsaturated concrete.<p> A laboratory testing program was established to characterize the material properties of concrete mixes with water-cement ratios 0.4, 0.5 and 0.6. Concrete was characterized by its saturated hydraulic conductivity, moisture retention function and dependence of diffusion coefficient on degree of saturation. A geotechnical centrifuge was used to determine the saturated hydraulic conductivity of the concrete samples. Values of the saturated hydraulic conductivity of the samples were in the range of 10-11-10-12 m/s.<p> The moisture retention function of concrete samples was determined using a vapour equilibrium technique. The experimental moisture retention data was used to determine van Genuchten parameters for each of the concrete mixtures and subsequently used to determine the capillary pressure-degree of saturation relationship and relative permeability-degree of saturation relationship as a ``closed- form`` analytical expression. An electrical resistivity technique was used to determine the dependence of the chloride diffusion coefficient on the degree of saturation of the concrete. The result was compared with the Millington and Quirk model. Most of the experimental results should be useful to researchers in the field, as well as the engineering community at large, considering that they are rarely found in the concrete literature.<p> Simulations were made to determine the influence of various parameters measured during experiment on movement of moisture and transport of chloride ions in unsaturated concrete using TOUGH2, a multiphase, multicomponent, model that simulates coupled heat, moisture and salt transport in saturated and unsaturated rocks.

Asphalt and Portland cement concrete constitutes a significant portion of the total infrastructure all over the world. It has been reported that much of this concrete infrastructure is now approaching or has already passed its original design life. Thus it is critical to be able to quantitatively assess the condition of these concrete components. In order to rehabilitate or repair the civil infrastructure, nondestructive evaluation (NDE) techniques have been of great interest for infrastructure management agencies. However concrete components present several specific NDE challenges that must be addressed. . Concrete naturally exhibits large scale heterogeneous microstructure with a great deal of local material property variability, For this reasons, many conventional NDE techniques that work well for steel and other homogeneous materials cannot be applied to concrete; concrete is unable to transmit high frequencies, as the heterogeneity of the concrete causes signals of smaller wavelengths or wavelengths equal to the nominal aggregate size to be scattered and severely attenuated. Nevertheless, progress has been made towards accurate and reliable in-place NDE of concrete structures and materials, for example impact echo, ultrasonic pulse velocity method, and the ultrasonic wave transmission method. However, the detection of smaller sized defects or remote defects that are located away from the testing location still pose problems. In addition, the large size and potential limited access conditions of civil structures raise additional challenges. To overcome the limitations of current NDE techniques for concrete, this research considers two different types of ultrasonic waves (coherent and incoherent wave) to quantitatively characterize and monitor defects in heterogeneous concrete materials. The global objective of this research is to determine the feasibility and applicability of using these ultrasonic waves as a global, rapid, reliable, and non-biased technique for the routine screening of defects or monitoring of concrete structures and materials. Three different problems are considered: 1) characterization of segregation in asphaltic concrete, 2) crack depth determination in pier cap of concrete bridge structure, and 3) monitoring of self-healing process in cement-based concrete.

Concrete structures deteriorate in their operating environment under the combined action of harsh environmental conditions and external loading. Although the applied load can lead to a certain degradation of the structure, the main long-term deterioration mechanism involves moisture movement and the transport of chlorides within concrete. In order to build durable and reliable structures, it is necessary to be able to accurately predict the movement of moisture and chlorides within concrete.<p> In the case of unsaturated concrete, the transport of chloride ions is integrally associated with prediction of moisture fluxes in concrete. Even the diffusion of chloride ions depends on the degree of saturation of the concrete since concrete must have a continuous liquid phase for diffusion to occur. Therefore, simple diffusion theory, used in the current literature, is not sufficient to predict the diffusion of chloride ions in the case of unsaturated concrete. Most diffusion models described in the current published literature are applicable to concrete structures that are permanently wet and invariably underestimate the amount of chlorides penetrating the concrete of structures subjected to wetting and drying cycles. The research presented in this thesis reviews current knowledge, mathematical models and test methods pertinent to the movement of moisture and transport of chloride ions in unsaturated concrete.<p> A laboratory testing program was established to characterize the material properties of concrete mixes with water-cement ratios 0.4, 0.5 and 0.6. Concrete was characterized by its saturated hydraulic conductivity, moisture retention function and dependence of diffusion coefficient on degree of saturation. A geotechnical centrifuge was used to determine the saturated hydraulic conductivity of the concrete samples. Values of the saturated hydraulic conductivity of the samples were in the range of 10-11-10-12 m/s.<p> The moisture retention function of concrete samples was determined using a vapour equilibrium technique. The experimental moisture retention data was used to determine van Genuchten parameters for each of the concrete mixtures and subsequently used to determine the capillary pressure-degree of saturation relationship and relative permeability-degree of saturation relationship as a ``closed- form`` analytical expression. An electrical resistivity technique was used to determine the dependence of the chloride diffusion coefficient on the degree of saturation of the concrete. The result was compared with the Millington and Quirk model. Most of the experimental results should be useful to researchers in the field, as well as the engineering community at large, considering that they are rarely found in the concrete literature.<p> Simulations were made to determine the influence of various parameters measured during experiment on movement of moisture and transport of chloride ions in unsaturated concrete using TOUGH2, a multiphase, multicomponent, model that simulates coupled heat, moisture and salt transport in saturated and unsaturated rocks.

Saturated permeability is likely a good method for characterizing the susceptibility of portland cement concrete to various forms of degradation; although no widely accepted test exists to measure this property. The hollow cylinder dynamic pressurization test is a potential solution for measuring concrete permeability. The hollow cylinder dynamic pressurization (HDP) test is compared with the radial flow through (RFT) test and the solid cylinder dynamic pressurization (SDP) test to assess the accuracy and reliability of the HDP test. The three test methods, mentioned above, were used to measure the permeability of Vycor glass and portland cement paste and the results of the HDP test were compared with the results from the SDP and RFT tests. When the HDP and RFT test results were compared, the measured difference between the mean values of the two tests was 40% for Vycor glass and 47% for cement paste. When the HDP and SDP tests results were compared, the measured difference with Vycor glass was 53%. The cement paste permeability values could not be compared in the same manner since they were tested at various ages to show the time dependency of permeability in cement paste. The results suggest good correlation between the HDP test and both the SDP and RFT tests. Furthermore, good repeatability was shown with low coefficients of variation in all test permutations. Both of these factors suggest that the new HDP test is a valid tool for measuring the permeability of concrete materials.

Although pervious concrete was first used in the nineteenth century, it has only recently begun to increase in popularity. As urban areas expand, the problems associated with runoff management have become more challenging. The focus on the negative environmental effects associated with pavement runoff has also increased. These two issues have spurred the recent interest in pervious concrete pavements.Pervious concrete, however, has deficiencies which limit its application as pavements. These limitations include low compressive strength, flexural strength, clogging, and other durability issues. The overall purpose of this project was to provide tools to evaluate and improve the durability and strength of pervious concrete such that it may be more confidently employed in urban roadways. The specific objectives of this project were to (a) investigate the effect of mixture design on strength of pervious concrete (including the effect of fibers), (b) evaluate effect of clogging materials on coefficient of permeability, (c) and investigate the use of the dynamic pressurization test to evaluate the durability of pervious concrete, (d) develop a simple model for predicting removal of clogging particles from pervious concrete pavement surface pores. This thesis documents the results of the laboratory testing, and presents recommendations for mixture proportioning. In addition, recommendations are provided for optimizing the balance between compressive strength and permeability.

This research targets Metakaolin as main material, with various kinds of combination materials and binder, and uses a mechanism to make colding metakaolin lightweight aggregate and then makes five different proportion of metakaolin lightweight aggregate, with an aim to know the effects of different proportion on aggregate through the destruction of point load , sift analysis , and unit weight. Choosing suitable aggregate based on ACI norm to set three groups of different water-cement ratio A(0.54)¡BB(0.46)¡BC(0.35) to mix into lightweight aggregate concrete, this is to find out the correlation between physical properties and mechanical behavior of metakaolin lightweight aggregate concrete through pressure resistance , splitting off , absorption capacities. The result shows that different proportions of metakaolin lightweight aggregate also take different effects, a suitable formula is selected in accordance with the application. Of all the groups, group D (cement¡Gslaked lime¡Gmetakaolin¡Gfly ash¡Gsand =12.5%¡G12.5%¡G28.125%¡G 9.375%¡G37.5%) has the best mechanical and physical performance. The mechanical properties such as pressure resistance and splitting strength of aggregate made from metakaolin lightweight aggregate concrete can meet up with CNS and ASTM norms, and it is superior to fly ash lightweight aggregate concrete.