Effect of Fly Ash on Rheology and Strength of Recycled Aggregate Concrete

Abstract

As the amount of construction wastes increase, reuse of demolished concrete is being considered in research areas. Reflecting these interests, this experiment was performed to clarify concrete's mechanical property and workability using recycled aggregate as a coarse aggregate. Eleven cases of concrete specimens were produced by changing the rates of replacement of coarse recycled aggregate, replacement of fly ash, design strength, and moisture state of coarse aggregate. Compressive and tensile split strength tests were taken to study the mechanical properties of hardened concrete. To verify flowability of fresh concrete, a slump test and a flow curve test using ICAR Rheometer were performed. It was found that using recycled aggregate and fly ash leads good workability by testing slump and flow curve. The yield stress of fresh concrete decreased with increase of recycled aggregate substitution rate. Through the test, it was confirmed that there is inversely proportional relationship between the slump and yield stress roughly. Recycled aggregate concrete containing fly ash has considerably lower plasticity viscosity than not containing fly ash. Strength test results showed that recycled aggregate tended to decrease compressive and tensile strength of concrete, when recycled aggregate was used as a coarse aggregate. Using over 30% recycled aggregate caused significant decreases in compressive and tensile strength. Replacing 30% cement with fly ash was helpful to improve the long-term strength of concrete.

Effect of Recycled Coarse Aggregate on Compressive Strength and Mechanical Properties of Concrete

“…이러한 건설폐기물의 증가 는 최종 매립장의 증설 부담을 가중시키는 원인으로 작 용하고 있으며, 기존 매립지는 포화상태가 되어 신규 매 립지를 부설하기 위해서는 매립지 선정에 있어 사회적인 문제가 발생 하는 상황에 도달하였다. [1][2][3] 또한, 강모래와 강자갈의 고갈로 인해 석산으로부터 골재를 수급하고 있는 상황이며, 건설용 골재 생산을 위 한 석산 개발은 주위의 환경과 밀접한 연관성이 있어 제 한을 받고 있다. 따라서, 이러한 문제를 해결하기 위한 대안의 하나로서 건설폐기물에서 생산한 순환골재의 재 활용 확대가 바람직하며, 이에 대한 심도있는 연구가 필     @             ⓒ     요한 상황이다.…”