PROCESSING AND PROPERTIES OF RECYCLED AGGREGATE CONCRETE BY

ii As interest in sustainable materials such as recycled aggregate concrete (RAC) rises, effort, it is important to understand the properties of RAC that relates to its use in construction. To respond to this need, various tests were performed to investigate the properties of RAC. Properties of RAC are highly affected by processing. Processing variables indeed in this study are two-stage mixing approach (TSMA) and control of RAC initial moisture contents. By two-stage mixing approach, the compressive strength of RAC improved with different initial moisture states of recycled coarse aggregates. However, in case of shrinkage, some previous studies showed that RCA can absorb larger amount of water than natural aggregates because RCA has a higher porosity which leads concrete to increase shrinkage. To make a balance strength with shrinkage, our tests were performed by various mixture batches. In addition, ring and dog bone tests were studied when the specimen is restrained and is affected by internal tensile stress. With using 74 % initial moisture states of recycled coarse aggregates, the compressive strength was similar to that of normal concrete and the drying shrinkage was less. Furthermore, test with using recycled fine aggregates(RFA) was performed and fly ash was used to reduce shrinkage of RAC. As RFA increases, the shrinkage of the specimen also increased because RFA is composed with mortar which plays an important role in volume of porosity. ii