International Concrete Abstracts Portal

Concrete specimens with unidirectional embedded AR-glass rovings were stored in a climatic test chamber at 40 °C (104 °F) and 99 % r.h. After this storage, the bending strengths of the specimens were tested. The uncovered fibers were observed with an Environmental Scanning Electron Microscope (ESEM). The specimens made of the low alkaline matrix and AR-glass rovings showed no strength losses. Whereas, the specimens reinforced with E-glass showed dramatic losses of strength and corrosion of glass fibers. Also, the specimens made of the high alkaline matrix and AR-glass reinforcement showed losses of strength. A corrosion of the fibers could not be detected. Causes for the measured losses of load capacity when using AR-glass reinforcement and Portland cement matrix are the weak points inside the interface fiber-matrix, caused by portlandit crystals. Storage tests in simulated pore solution of 80 °C (176 °F) and pH 13 showed clearly, that glass corrosion cannot start before the protective fiber size is at least partially dissolved. In this case, the VET-AR-glass fibers are of advantage. During the alkaline attack on the unprotected AR-glass surface, the content of zirconium dioxide determines the corrosion resistance for the respective glass. In this case, the NEG-AR fibers are of advantage. The investigations show, that durable fiber concretes and textile reinforced concretes with AR-glass respectively can be produced by optimizing the mixtures. In this respect, the climatic test chamber storage proved to be an accelerated aging test.

Strengthening by textile reinforced concrete noticeably increases both the ultimate load bearing capacity as well as the serviceability - especially deflections, crack widths and crack spacing are reduced. Beside that there are still some practical applications. This paper will give an overview of the ongoing research work with this new composite material Textile Reinforced Concrete (TRC).

Mechanical properties of a cement-based matrix - grid (CMG) system developed for masonry rehabilitation are discussed. CMG system is a composite consisting of a sequence of layers of cement-based matrix and alkali resistant (AR)-glass coated reinforcing grid. The experimental program included tension and flexural tests of composites with special consideration to long term durability. Variables studied include effect of composite thickness, fabric orientation, and effect of accelerated aging on the tensile and flexural responses. Results indicate that samples in the cross machine direction (XMD) showed the best combination of high tensile strength (in excess of 5 MPa?0.725 ksi) and Ultimate strain value (2.36%) as compared to the machine direction (MD) with (5 MPa?0.725 ksi and ultimate strain of 1.8%). After 28 days of accelerated aging, tensile strengths reduced to about 3.87 MPa?0.56 ksi for the MD and XMD directions respectively, representing average reductions of 23% and 17%. In the flexural samples, cross machine samples (XMD) show a combination of high flexural strength (15-17 MPa?2.18-2.47 ksi) and Maximum deflection (of 15-22 mm?0.59-0.87 in) as compared to the MD samples. Higher stiffness of fabrics in the cross machine direction due to the manufacturing process was the source of such differences in behavior. The first crack strain in flexure is as much as the ultimate tensile strength in tension for many composites. A discussion of comparison of tensile and flexural stress measures is presented.

This paper presents the research activities in the field of textile reinforced concrete carried out by the Institute of Textile and Clothing Technology (ITB) of the Technische Universitaet Dresden, Germany. Extensive research has been conducted with the aim to fully use the tensile strength of the applied high-performance fiber material in the reinforcing textile. To achieve this, the textile machinery was adjusted and improved and new testing methods were developed. This research has resulted so far in several innova-tive applications for the repair of buildings as well as the production of precast concrete members. This paper was originally presented in 2005 Spring ACI Convention, New York under the title "State of the art and perspectives of textile reinforcements of con-crete components."

This paper describes two models used in the modeling strategy for textile reinforced concrete. The modeling of multi-filament yarns and of the bond between yarn and matrix is focused on micromechanical aspects of the material behavior. The calibration procedure of the model is explained on an example of a detailed experimental and numerical study of pull-out specimen. We demonstrate the use of the model for numerical homogenization to derive effective parameters at the meso level. In parametric studies we analyze the influence of local imperfections in the microstructure arising in the production process on the meso- and macromechanical properties of the material.