Call number: LD2668 .T4 1958 B69 / Master of Science

Residual moisture from incompletely dried aggregates would most likely remain in the Warm Mix Asphalt (WMA) due to its lower production and compaction temperature, resulting in harmful effects on field performance. Dynamic modulus has been recognized as a parameter that reflects the overall behavior of asphalt mixtures and possesses promising correlations with field performance. This study aims to investigate the effects of moisture susceptibility of WMA on dynamic modulus and simulate the field performance with the aid of Mechanistic-Empirical Pavement Design Guide (MEPDG) software. Four distinct sets of WMA specimens were prepared as follows: 1. fully dried aggregates without moisture conditioning; 2. fully dried aggregates with moisture conditioning; 3. incompletely dried aggregates without moisture conditioning; and 4. incompletely dried aggregates with moisture conditioning. Simple Performance Test (SPT) was employed to collect the raw data of dynamic modulus tests and master curves were constructed from the reduced data using Hirsch model. The results show that moisture can negatively influence the dynamic modulus values and moisture conditioning had more effect than residual moisture from incompletely dried aggregates. Two types of distress, fatigue cracking and rutting, were analyzed in the simulation. Moisture can significantly decrease the resistance against rutting and to a lesser extent, the resistance against fatigue cracking.

Digitized by Kansas Correctional Industries

Digitized by Kansas Correctional Industries

In environments of high moisture exposure, carbon fibre-reinforced polymer (CFRP) reinforcement is believed to be a good alternative to steel due to its non-corrosive properties. However the CFRP matrix experiences other types of changes, mechanical deterioration and transverse swelling, with exposure to moisture and sustained stresses. Specifically for structural applications, few studies have investigated the effects of moisture and stress-induced matrix-dominated changes to the CFRP-concrete bond when the CFRP rods are cast into concrete as prestressed reinforcement. Experiments were conducted to measure the transverse swelling and moisture uptake rates of stressed and unstressed CFRP rods immersed in water and concrete pore solution (CPS). CFRP rods were also embedded in concrete and immersed in water to observe whether the transverse swelling of the rods would cause the concrete to crack. Pull-out tests were conducted on stressed and unstressed CFRP rods cast in concrete cubes and immersed in water for up to 125 days. Six CFRP prestressed concrete prisms were fabricated, three were immersed in water for over 125 days and three were left in lab conditions before being tested in three-point bending. Moisture-induced transverse swelling did not appear to cause cracking of the concrete covering CFRP rods in water, contrary to the prediction of the thick-walled cylinder model, but possibly caused an increase in the CFRP-concrete radial contact pressure. The imposition of sustained bending stresses on wet CFRP rods was found to cause premature failure, believed to be a result of matrix softening and microcracking. These observations of swelling and matrix degradation were believed to affect the CFRP-concrete bond. The pull-out tests of unstressed CFRP rods indicated an increased likelihood for bond failure in the CFRP matrix with moisture exposure. This resulted in greater variations in the ultimate and residual bond stresses of the wet samples compared to the dry controls. For the prestressed pull-out samples, higher magnitudes of prestressing resulted in lower bond failure loads. Both outcomes are indicative of matrix weakening with moisture and stress exposure. However despite this, the three-point bending tests revealed no significant differences in behaviour between the wet and dry prestressed prisms. Although the wet prisms exhibited slightly greater variation in their post peak load behaviour compared to the dry prisms, in line with the observations from the pull-out tests. The work from this thesis reveals that despite observations of matrix deterioration and transverse swelling in CFRP rods exposed to moisture and stress, the effect of these changes to the overall behaviour of a CFRP prestressed concrete member are minimal. Any long-term effects are unlikely to cause significant changes to the behaviour of the member. However, the CFRP-concrete bond may be more variable in members exposed to moisture, which should be allowed for in the design process. Therefore CFRP is a promising alternative to steel reinforcement in high moisture environments, with good long-term durability.

Typescript. / Digitized by Kansas Correctional Industries

Typescript. / Digitized by Kansas Correctional Industries

This thesis addresses various issues in connection with the measurement of moisture content in timber. The early parts include long term experimentally based studies which culminated in producing recommendations to existing British Standards for equilibrium moisture content (EMC) of timber in internal environments. Findings consistently showed lower EMCs than existing recommended values; these are believed to be caused by socio-economic factors. Intermediate sections of the thesis continue with tests on electrical methods of moisture content measurement to establish a basis for comparability and the claimed accuracy of currently available moisture meters in the market. To this end, the performance of a wide range of resistance-type moisture meters in worldwide use was critically investigated under laboratory conditions - it was established that even under the strict controlled conditions of the study, large discrepancies are not uncommon (as great as 13% moisture content difference was observed). While some instruments consistently underestimated, others overestimated under identical conditions. Lack of agreed standards for species corrections and temperature correction factors were found to be the main cause of disagreement between the meters. Further discussions include the layout for a proposed standard in which agreed values for species and temperature correction factors would be established. In the latter part of the thesis moisture gradients in timber, the causes and the current methods of assessment are discussed. In particular, the performance of a leading brand capacitance-type moisture meter was systematically investigated both in the absence and in the presence of predetermined moisture gradients. It was established that moisture gradients severely affect the measured moisture content. A computer controlled capacitance measurement system based on resonance detection was developed to initially replicate the behaviour of conventional capacitance-type moisture meters, and to further investigate possible moisture gradient detection protocols. Two electrode designs were used in order to investigate methods by which moisture gradients could be detected. It was shown that a multi-plate electrode can be used to detect moisture gradients in timber to depths of at least 10 mm.

The thesis has the objective of design a methodological model for evaluate and compare the behaviour of external walls exposed to moisture phenomena. The comparison is related to different variables us for example: thermal conductivity, thermal transmitance, moisture content in the element along the time, P.O. Fanger theory of comfort, risk grouwth of mould among the others parameters. The model is developed in function of two softwares that permit sensibilyze the performance of building elements in relation of the presence of different quantities of moisture inside of them along the year. In this case, the model is probe with the use of TRNSYS 15 and WUFI 3.2 Pro softwares. The results show that there are many differences in the analysis of the different parameters in the cases with the materials in dry and wet state. Also, is possible to realize that the improve of any constructive solutions they are amortized in periods of time that no exceed more than three years in relation to the save of energy for the improvement in the themal conductivity of the materials.

Thesis (Ph. D.)--Oregon State University, 1971. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.