RCA CONCRETE: A STUDY OF PROPERTIES IN THE FRESH STATE, STRENGTH DEVELOPMENT AND DURABILITY

The paper describes a study undertaken to examine the use of recycled concrete aggregates (RCA) in concrete mixes. The effect of RCA on concrete ceiling strength is also discussed. The workability tests showed a reduction in slump with increasing proportion of RCA in the mix, but it remained within allowable margins (± 25mm). The mixes with more than 50% coarse or 30% fine RCA were found to be harsh and exhibit increased bleeding. This inherent instability can be overcome by using a filler material, such as coarse PFA. The results showed that the original concrete type had little or no influence on the strength development of concrete. Up to 30% coarse or 20% fine RCA was also found to have a negligible effect on strength but thereafter, there was a gradual reduction in strength with increasing RCA content. A method of accommodating the effects of high proportion of RCA, involving simple adjustment to the water/cement ratio of the mix was proposed. It was shown that RCA concrete can develop engineering properties and durability similar to natural aggregate concrete, providing equal 28 day strength is achieved. Issues relating practical use are also discussed.

• ABSTRACT

• INTRODUCTION

• EXPERIMENTAL DETAILS

• USE OF RCA IN CONCRETE MIXES

• PERFORMANCE OF RCA CONCRETE

• CEILING STRENGTH OF RCA CONCRETE

• PRACTICAL ISSUES FOR USE

• CONCLUSIONS

• ACKNOWLEDGEMENTS

• REFERENCES