Shrinkage Deformation of Concrete Containing Recycled Coarse Aggregate

The long term properties of Concrete containing Recycled Coarse Aggregates (CRCA) were investigated. Initially, series of short term tests were carried out to determine the density, workability, absorption and compressive strength of concrete with and without locally available recycled aggregates from demolition wastes. The water cement ratio of 0.52 was adopted for all the mixes, while the coarse aggregate in concrete was replaced with 0%, 25%, 50% and 100% recycled coarse aggregates.
The test results indicated that the replacement of normal coarse aggregates by recycled aggregates up to 25% had no significant effect on the compressive strength but higher levels of replacement reduced the compressive strength. A replacement level of 100% caused a reduction of about 27% in compressive strength.
The shrinkage deformation characteristics of concrete made with 25% recycled coarse aggregate were compared with those of normal concrete. Eight 10cm x 10cm x 40cm concrete sealed and unsealed short columns made with and without RCA, were under investigation for 120 days. The results of the investigation showed that the basic shrinkage strains of normal concrete is about 1.07 times greater than that of CRCA (with 25% RCA). The drying and total shrinkage strains of CRCA (with 25% RCA) are respectively 2.56 and 1.26 times greater than that of normal concrete. 25% RCA content in concrete was therefore considered for use in load bearing structural elements.