No description available.

Fabric as a flexible formwork for concrete is an alternative giving builders, engineers, and architects the ability to form virtually any shape. This technique produces a superb concrete surface quality which requires no further touch up or finishing. Woven polyole-fin fabrics are recommended for this application. A permeable woven fabric allows excess water from the concrete mix to bleed through the mold wall, and therefore reduce the water-cement ratio of the concrete mix. Due to the reduction in water-cement ratio, higher compressive strength in fabric formed concrete may be achieved, as also suggested by earlier research. The current research study was conducted to investigate and document the changes in concrete strength and overall quality due to use of commercially available woven polyolefin fabrics. Use of fabric formwork will contribute to decreased construction cost, construction waste, and greenhouse gas emissions. Two sets of tests were conducted as a part of this research study including comparison of compressive strength of fabric formed versus PVC formed concrete cylinders and comparison of be-haviour of the fabric formed reinforced columns versus cardboard formed reinforced concrete columns. Variables in this research were limited to two types of fabric with dif-ferent permeability (Geotex 104F and Geotex 315ST) and two types of concrete; concrete made with conventional Portland cement and no flyash herein called normal concrete (NC) and concrete with 30 percent flyash in its mix design (FAC). The laboratory results revealed that fabric Geotex 315ST is an ideal geotextile for forming concrete. It was also found that the effects of fabric formwork on concrete quality in a large member are limited mostly to the surface zone and the core of the concrete remains the same as a conventionally formed concrete. Even though fabric formed cylinder tests showed an average of 15% increase in compressive strength of the concrete samples, compressive strength of the reinforced columns did not dramatically change when com-pared to the companion cardboard formed control columns. This research confirmed that fabric formwork is structurally safe alternative for forming reinforced concrete columns.

Fabric as a flexible formwork for concrete is an alternative giving builders, engineers, and architects the ability to form virtually any shape. This technique produces a superb concrete surface quality which requires no further touch up or finishing. Woven polyole-fin fabrics are recommended for this application. A permeable woven fabric allows excess water from the concrete mix to bleed through the mold wall, and therefore reduce the water-cement ratio of the concrete mix. Due to the reduction in water-cement ratio, higher compressive strength in fabric formed concrete may be achieved, as also suggested by earlier research. The current research study was conducted to investigate and document the changes in concrete strength and overall quality due to use of commercially available woven polyolefin fabrics. Use of fabric formwork will contribute to decreased construction cost, construction waste, and greenhouse gas emissions. Two sets of tests were conducted as a part of this research study including comparison of compressive strength of fabric formed versus PVC formed concrete cylinders and comparison of be-haviour of the fabric formed reinforced columns versus cardboard formed reinforced concrete columns. Variables in this research were limited to two types of fabric with dif-ferent permeability (Geotex 104F and Geotex 315ST) and two types of concrete; concrete made with conventional Portland cement and no flyash herein called normal concrete (NC) and concrete with 30 percent flyash in its mix design (FAC). The laboratory results revealed that fabric Geotex 315ST is an ideal geotextile for forming concrete. It was also found that the effects of fabric formwork on concrete quality in a large member are limited mostly to the surface zone and the core of the concrete remains the same as a conventionally formed concrete. Even though fabric formed cylinder tests showed an average of 15% increase in compressive strength of the concrete samples, compressive strength of the reinforced columns did not dramatically change when com-pared to the companion cardboard formed control columns. This research confirmed that fabric formwork is structurally safe alternative for forming reinforced concrete columns.

ACI Committee 544's repeated drop-weight impact test for concrete is often criticized for large variations within the results. This paper identifies the sources of these large variations and accordingly suggests modifications to the ACI test. The proposed modifications were evaluated and compared to the current ACI test by conducting impact resistance tests on 40 specimens from two batches of polypropylene fiber-reinforced concrete (PPFRC). The results obtained from both methods were statistically analyzed and compared. The variations in the results were investigated within the same batch and between different batches of concrete. The impact resistance of PPFRC specimens tested with the current ACI test exhibited large coefficients of variation (COV) of 58.6% and 50.2% for the first-crack and the ultimate impact resistance, respectively. The corresponding COV for PPFRC specimens tested according to the modified technique were 39.4% and 35.2%, indicating that the reliability of the results was significantly improved. It has been shown that, using the current ACI test, the minimum number of replications needed per each concrete mixture to obtain an error below 10% was 41 compared to 20 specimens for the modified test. Although such a large number of specimens is not good enough for practical and economical reasons, the reduction presents a good step on the development of a standard impact test.

No description available.

This study was conducted to evaluate the effect of curing and mix design parameters, such as cement content and water to cementitious materials ratio, on the strength and durability characteristics of plain and silica fume cements exposed to a hot-marine environment. Specifically, the effect of curing and mix design parameters on chloride diffusion, shrinkage and carbonation of cement mortar specimens exposed to a hot-marine environment was evaluated. The results indicated that high water to cement ratio significantly influenced the durability performance of concrete through: (1) accelerating chloride diffusion and carbonation, (2) increasing the shrinkage and weight loss, and (3) reducing the compressive strength. Similarly, increasing the cement content increased the shrinkage for a given w/c ratio. However, the chloride diffusion and carbonation were minimized and strength was enhanced due to increasing cement content. The mix design parameters, namely, water-cement ratio and cement content significantly influenced the performance of both Type I and Type V cements, while the influence of these parameters on the performance of silica fume cements was insignificant. Although Type I cement mortars performed better than Type V cement mortars, the performance of silica fume cement was the best in terms of reduced chloride diffusion, carbonation and shrinkage, and enhanced strength. The beneficial effects of silica fume cements, were however, only evident in specimens subjected to good curing. Therefore, to extend the useful service-life of reinforced concrete structures exposed to hot-marine environments, the following mix design is recommended: (i) cement content should not be less than 350kg/m³; (ii) Type I cement with 10% silica fume; (iii) water to cementitious materials ratio of not more than 0.45; (iv) good curing.

No description available.

The work described in this thesis is concerned with the behaviour, analysis and design of reinforced concrete beams. A brief historical review of the methods of analysis on deep beams is given. The current major codes of practice and design manuals associated with reinforced concrete deep beams are reviewed. This study has been useful in identifying the limitations of the current design documents on the subject of deep beams. Because of the acute shortage of information regarding buckling, web-opening and combined loading, three test programmes are performed to provide experimental evidence on these topics. Their behaviour is examined in terms crack developments, crack patterns, modes of failure, in-plane and lateral displacements, ultimate loads, strains and stresses. The ultimate buckling strength of the slender deep beams without web-openings are analysed using the methods described in the CIRIA Guide (1977). Adopting the same methods in the guide, an attempt has been made to analyse the buckling strength of deep beams with web-openings. Based on the structural idealization of Kong et al (1973), a modified approach is proposed for the ultimate shear strength of deep beams with web-openings. In addition, the CIRIA ultimate shear interaction equation for deep beams under combined top and bottom loadings is studied and an equation is proposed for the uniformly distributed loading cases. Finally, based upon these findings, some design recommendations are given.

It is well known that arching action in reinforced concrete slabs resulting from surrounding restraining elements is responsible for much greater collapse loads than those estimated considering flexural effects only. However, the subject needs to be better understood and simplified if it is to be reliably applied in broader practice. This thesis presents a rational treatment of the problem. By limiting the scope of investigation to one-way slab systems, for the first time an explicit method of calculating the load-carrying capacity of elastic- plastic slab strips with a laterally rigidly restrained boundary condition is derived. Application of the proposed model to specimens selected from four experiment programs proves its reliability in ultimate strength calculations. The proposed model is then employed in a parametric study of structural responses of deck slab strips. The parametric study shows that a longer span, lightly reinforced deck slab system is still adequate in strength if it is cast in higher strength concrete and sufficient lateral restraint is available.

It is well known that arching action in reinforced concrete slabs resulting from surrounding restraining elements is responsible for much greater collapse loads than those estimated considering flexural effects only. However, the subject needs to be better understood and simplified if it is to be reliably applied in broader practice. This thesis presents a rational treatment of the problem. By limiting the scope of investigation to one-way slab systems, for the first time an explicit method of calculating the load-carrying capacity of elastic- plastic slab strips with a laterally rigidly restrained boundary condition is derived. Application of the proposed model to specimens selected from four experiment programs proves its reliability in ultimate strength calculations. The proposed model is then employed in a parametric study of structural responses of deck slab strips. The parametric study shows that a longer span, lightly reinforced deck slab system is still adequate in strength if it is cast in higher strength concrete and sufficient lateral restraint is available.