Effect of fineness and dosage of fly ash on selected properties of mortars
- Concrete Institute of Australia
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- Conference Proceeding
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In this paper, a laboratory investigation was carried out to evaluate the effect of fineness and levels of fly ash on the selected fresh, hardened and durability properties of mortars such as flow, compressive strength, drying shrinkage, strength activity index and alkali-silica reactivity. Portland cement was partially replaced by 20%, 30% and 40% of three kinds of fly ashes with different fineness (classified, run-of-station and ground run-of-station fly ashes). Fixed water to binder ratio of 0.40 and sand to binder ratio of 2.5 with a fixed dosage of water reducer were maintained for these mixes. In addition, some mixes containing classified and run-of-station fly ash with 50%, 60% and 70% cement replacement with fixed water to binder ratio of 0.55 and sand to binder ratio of 5 with a fixed dosage of water reducer were cast to evaluate the effect of fineness of fly ash in low strength mortar. Moreover, the effectiveness and required level of classified and run-of-station fly ash on mitigating alkali-silica reactivity are evaluated using accelerated mortar bar test method, and the results are reported in this paper. The results showed that all kinds of fly ashes improved the flowability of the mix with superior performance for the finer fly ash. X-ray diffraction and compressive strength test results demonstrated the effect of fineness of fly ash in decreasing the crystalline phase, increasing reactivity and improving the strength development. Drying shrinkage was decreased considerably with the inclusion of all kinds of fly ashes at all replacement levels. Incorporation of 25% classified and run-of-station fly ash is needed to control the expansion of mortar bars due to alkali-silica reactivity by the reducing the alkalinity of the mix.
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