دانلود رایگان مقاله اثر شتاب پیری بر روی رابط کاربری بتن آرمه نساجی جوت

abstract

In this work the degradation mechanisms of concrete reinforced with natural jute textile are discussed. Double-sided pullout tests were performed on specimens reinforced with polymer-coated and uncoated jute fabrics. To obtain a composite with an enhanced durability performance a matrix with partial replacement of the Portland cement by metakaolin was used. Before testing, the specimens were subjected to accelerated aging conditions. After a curing period of 28 days in water the samples were exposed to a temperature of 40
C and a relative humidity of 99% over 28, 56, 90, 180 and 365 days. Microstructural analyses were performed to evaluate the degradation of the jute yarn and the fibermatrix interphase using an environmental scanning electron microscope. Thermogravimetric analysis was carried out in order to evaluate the calcium hydroxide content. The pullout results showed that coated fabrics formed a stronger bond than did the uncoated. For ordinary Portland cement matrix the maximum fiber pullout force decreased up to 85% after six months of accelerated aging. In the MK matrix the degradation process was retarded substantially. Polymer coatings improved the bond between fiber and matrix and reduced fiber degradation.

5. Conclusions

The following conclusions can be drawn from the present work on the interface properties of jute-textile-reinforced concrete exposed to accelerated aging: - Double-sided pullout tests performed after accelerated aging showed that the OPC composite system yielded better results for specimens with coated fabric, although at 180 days there was a complete loss of ductility. At 180 days of aging, the matrix and coated fibers showed major signs of degradation, and no typical fiber pullout could be observed due to the failure of the fabric immediately after the cracking of the matrix. At 365 days of aging the specimens could no longer withstand the aging process. The hypothesis is that the aging process became more severe at 365 days for OPC matrix e coated fabric, since a reaction may have occurred between the coating and calcium hydroxide, while in the matrix with metakaolin the pozzolanic reactions consume the calcium hydroxide, leading to an increase in the density of the matrix and thus protecting the fiber and coating.