Materials used for structural applications must possess high strength and durability. Portland cement concrete does not have high acid resistance because its principal hydration product is calcium hydroxide, which has very high solubility in water. This soluble phase can be lowered by replacing part of the cement with coal fly ash, which also results in an increase of the strength of hardened concrete. The aim of this work was to improve the compressive and tensile strengths and the durability of hardened cement pastes with the addition of coal fly ash and engineered iron-oxide nanoparticles. The improved cement pastes are to be used for pervious concrete. A three-factor factorial design was used to find the appropriate proportions of water, coal fly ash and engineered iron-oxide nanoparticles that could lead to the highest strength and durability of the cement paste composites. Tensile and compressive strengths were measured after curing the specimens in water for 3, 7, 28, 56 and 86 days. Acetic and sulfuric acid solutions were used for the acid resistance test. Specimens used for this test were cured for 28 days in tap water and then placed in the acid solutions. The weight loss of the specimens was recorded after 3, 7, 28, 56 and 86 days of curing in the acids solutions, and then they were broken to measure their compressive strength. Preliminary results showed that the rate at which coal fly ash-added specimens gained resistance was higher at long term curing period. The addition of engineered iron-oxide nanoparticles to the mixtures enhanced workability and compressive strength of the cement pastes. The specimens prepared with low water to powder ratio resulted in poor hydration of the cementitious paste and consequently low compressive strength. Iron leaching in deionized water, sulfuric acid and sodium chloride solutions, and corrosion tests are currently under investigation.

Characterization of cement paste containing coal fly ash and engineered iron-oxide nanoparticles

247th National Meeting (2014)

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