Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2010. / Committee Chair: Jacobs, Laurence; Committee Co-Chair: Kurtis, Kimberly; Committee Member: Kim, Jin-Yeon. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Supervisors: David W. Fowler and B. Frank McCullough. Vita. Includes bibliographical references.

The mechanical properties of the polymer-modified mortar are markedly improved over conventional cement mortar. We utilized recycled ABS in powder form and a polymer latex emulsion, polymer percentage ranges from 0 to 25 percent by polymer/cement ratio were investigated. The mechanical properties investigated were compression strength and adhesion strength. Compression strength effects did not have an impact on adhesion strength. Adhesion strength was calculated with pullout testing apparatus designed by the author. Results indicate that recycled ABS had a lower adhesive strength than the acrylic latex emulsion and the base mortar, but did increase in adhesive strength when mixed with maleic-anhydride. The adhesive strength was investigated for a Fiber Reinforced Polymer (FRP) made of an "E" glass fiber that is a continuous strand roving oriented and pre-tensioned longitudinally in an isopthalic polyester matrix material. The FRP rebar was compared to standard steel rebars, and found that the standard steel corrugated rebar had a higher adhesive strength, due to mechanical interlocking. This was clarified by measurements using a smooth steel rebar. Characterization of the polymer-modified mortar was conducted by pore analysis and scanning electron microscopy. Scanning Electron Microscopy was implemented to view the polymer particles, the cement fibrils formed by the hydration, and to prove Ohama's theory of network structure.

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Concrete is probably the most widely used construction material in the world. In the Arabian Gulf region, deterioration of concrete due to the aggressive environment is recognized to be the main factor affecting their structural integrity. The durability of concrete structures can be preserved by various protection methods; however, using cement replacement materials is one of the most effective and economic methods of maintaining their stability as well as extending their service life. The aim of this project is to study four interrelated aspects, namely, (1) the effect of hot environment on the properties of fresh concrete incorporating mineral admixtures, (2), the influence of exposure environment on the engineering properties of hardened concrete, under various curing conditions, without and with mineral admixture, (3), the differences in porosity and pore structure of the same set of mixes, and, (4) the effect of outdoor exposure on the durability-related properties of concrete. To achieve the above aims, the experimental programme involved the study of five different mixes of combinations of silica fume/slag and silica fume. The effects of real exposure to the Arabian Gulf environment of these mixes subjected to four curing regimes, namely, continuous water curing, no water curing after demolding, and air drying after 3 and 7 days of initial water curing were investigated. The properties investigated include (1) consistency and setting times of cement pastes, workability and workability loss with time, (2) engineering properties such as compressive strength, dynamic modulus of elasticity, pulse velocity, shrinkage, expansion and thermal expansion, (3) microstructural properties such as porosity and pore size distribution, (4) durability-related properties such as permeability, water absorption and carbonation depth. The results show that exposure to hot environment results in rapid setting times, faster loss of slump, higher porosity, coarser pore structure and more permeable concretes. It was found that part cement replacement by silica fume and slag improves the quality of concrete mixtures, refined the pore structure and produced concretes with very low porosity and continuous pore diameter in both indoor and outdoor environment. The properties of concrete containing mineral admixture appear to be more sensitive to poor curing than the plain concrete, with the sensitivity increasing with increasing amount of slag in the mixture.

The use of asbestos fibres in construction products has been banned in European countries for about two decades due to its effect on human health. At present, many developing countries use asbestos cement board as one of the most important construction products for roofing, cladding and partition walls. The Hatschek process is the most commonly used method to produce asbestos Fibre Cement Board (FCB). There are two major problems for the asbestos FCB manufacturers in replacing their products with non-asbestos FCB. The first one is finding materials and fibres that are available and competitive in price compared to asbestos fibres, and the second is providing inexpensive machines and equipment to produce non-asbestos FCB. In this research, an effort has been made to solve these two major problems. After the initial laboratory investigations on several natural and synthetic fibres some of the fibres with potential use in FCB were chosen for the further investigations. A slurry vacuum dewatering process was then designed and made for the laboratory use. The performance of material selections and mix designs selected from the laboratory studies were subsequently verified with factory Hatschek process in a factory site trial. Many specimens with natural and synthetic fibres incorporating silica fume and limestone powder were made and tested in the laboratory. Silica fume and limestone powder were used for enhancing flexural strength and suppression of alkalinity to reduce breakdown of the cellulose fibres. The results of mechanical, physical and II durability tests were analysed. The microstructure of the fibres and composites was also studied by SEM (Scanning Electron Microscopy). At some stages, mix design optimization was carried out to gain the highest flexural strength. The most suitable mixes were chosen for the factory site trials. A number of full-scale non-asbestos trial boards were made successfully in an asbestos FCB factory and tested in accordance with the current national and international standards. The results indicated that the trial boards fulfilled the requirements of the relevant standards. Based on the outcome of this research, a combination of acrylic fibres and waste cardboard in a mix incorporating silica fume and limestone powder in addition to Portland cement can be used to replace asbestos fibres. Although broadly compatible with the asbestos cement production process, this formulation change will necessitate some changes to the existing production lines in asbestos cement factories to produce non-asbestos FCB.

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Today's concrete is no longer a simple combination of cement, aggregates and water. With increased use of various types of waste materials as supplementary cementitious materials and chemical admixtures, material incompatibility problems have been observed in concrete construction. As a result, some of the greatest problems in concrete manufacturing occur when concrete does not stiffen or harden on time. To this end, a new innovative type of cementing technique (based on the principles of magnetorheology) is presented that allows for the real-time control over the stiffening or setting behavior of concrete. In traditional magnetorheological (MR) fluids, magnetic particles are mostly submerged in Newtonian carrier fluids using high volumetric contents (40-50%) of magnetic particles. A key interest in this work was to investigate if using a non-Newtonian carrier fluid like cement paste with low dosages of magnetic particles would yield an MR effect. Rheological tests were conducted on paste mixtures containing small dosages of magnetic particles (less than 2% volume fraction) and when a magnetic field was applied, it was determined that the shear resistance of the paste could be altered significantly. The response of the paste was found to be dependent on the magnitude of the applied field, concentration of the magnetic particles and surface chemistry of magnetic particles. Furthermore the magnetic particles used in this research to create the MR cement paste did not have any effect on cement hydration products or on compressive strength results. It was shown that the rheological behavior of cement paste could even be adapted to simulate "setting" behavior when an MR-based approach is used. Thus, the potential to create a cement-based material whose fresh state behavior can be adapted on-demand by the user to achieve a desired behavior may soon be a reality. Such a material can be useful in applications in which controlling the fresh-state behavior is critical, and could transform the way cement-based materials are cast. In addition, possibilities to create a smart cement-based composite from the fresh to the hardened state may be possible if the magnetic particles could later be used for structural health monitoring. / text

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