مهندسی عمران شریف (Nov 2020)
EFFECT OF COMBINED USE OF GLASS AND POLYMER FIBERS ON MECHANICAL PROPERTIES, SHRINKAGE, AND DURABILITY PROPERTIES OF CEMENT COMPOSITES
Abstract
In this study, the mechanical properties and durability of composites containing fibers and polymers were investigated. For this purpose, calcium aluminate cement and Portland cement were used as binding agents. Glass fiber and polymer (Forton VF-774 ) were used to modify the mix. The specimens were prepared using 2\% and 4\% glass fiber (vol./vol) and 5\% polymer by cement weight. The length of the fibers was 25 mm. The mechanical tests performed consist of compressive strength, flexural strength, tensile strength, flexural toughness and impact strength, and RCMT as well as the shrinkage test. The compressive strength test was performed at the ages of 1, 7, 28 and 90 days. The mixtures made of calcium aluminate cement had higher compressive strength due to faster formation of microstructure than the Portland cement mixtures so that 90 -day compressive strength of Portland cement mix was comparable to 90 1 -day compressive strength of calcium aluminate mortar. By adding the polymer to the mixtures, the compressive strength was reduced. It was also observed that by increasing the glass fiber content from 2\% to 4\%, compressive strength became lower. Upon increase in age, the compressive strength was enhanced due to the formation of polymer films in the porous structure of the mixtures and improvement of the cement hydration. In polymer modified specimens, the flexural strength was also increased due to the production of polymer films in the structure of mixes. Flexural strength was increased with the addition of glass fibers due to high aspect ratio of the glass fibers and well-formed Interfacial Transition Zone (ITZ). The addition of glass fiber from 2\% to 4\% influenced the bending strength of polymer specimens and had an enhancing effect on the tensile strength, flexural toughness, and impact resistance. However, in the durability test, fiber incorporated mixtures had higher chloride ion penetration. Adding fibers to the blends reduced the amount of shrinkage.
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