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).

The research presented in this paper focuses on a cement-based matrix-grid (CMG) system developed for masonry rehabilitation. The objectives of the research and development program were to determine the mechanical properties of the CMG system and to assess its effectiveness for improving unreinforced masonry (URM) wall seismic performance from a load bearing capacity and deflection limits point of view. 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 materials and structural tests. Tensile and flexural tests were carried out on unaged and aged composite to assess its long term durability up to the equivalent of approximately 129 years service life. Selected tensile test results are presented in this paper, whereas full details of materials tests are presented in a separate paper. Structural tests included in-plane shear concrete masonry unit (CMU) walls. Three composite configurations were explored and the results were compared with those obtained using various fiber reinforced polymer (FRP) systems overlay configurations also tested in in-plane shear. Retention of tensile properties over time was approximately 75-80% after the equivalent of approximately 50 years service life. Structural test results demonstrated the ability of the cement-based system to strengthen the walls, and showed superior performance of field CMG system compared to FRP alternatives. X-cracking failures were observed, there was no delamination of the system from the CMU walls, and the system held the masonry pier together at failure. Due to its advantages and unique properties this system is a potential alternative to traditional and new FRP masonry rehabilitation and strengthening techniques.

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.

The failure mechanisms of textile reinforced concrete (TRC), which is a composite of bundles of long fibers and fine-grained concrete, are complex. Even after fracture of the constituents AR-glass and concrete the bond behavior has an important influence on the effective material behavior of the composite. Therefore, any realistic numerical simulation of the TRC composite behavior requires an accurate model of the bond between the reinforcement and the matrix as well as between the filaments within the roving. This paper summarizes the main characteristics of TRC. Further, an adhesive cross linkage approach is used to model the different bond aspects within the roving. In addition to this analytical approach some numerical simulations are presented.

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.