This study was aiming to evaluate the fundamental characteristics
of the concrete using RCA for its application to structural concrete
members by examining strength, chloride ion penetrability,
and carbonation resistance. The concrete evaluated in this study
used 100% coarse RCA, various replacement levels of natural aggregate
with fine RCA, and several levels of fly ash addition. From the
experimental studies presented herein the following conclusions
were drawn.
(1) Compressive strength of mortar gradually decreased as the
amount of the fine RCA increased. At 100% of the replacement
level, the mortar strength decreased by about 33% at
28 days. At over 60% of the replacement level of fine by
RCA, the strength reduction was more significant.
(2) Regardless curing conditions and fly ash addition, the 28 day
strength of the recycled aggregate concrete was greater than
the design strength, 40 MPa, up to 60% of the natural fine
sand replacement by RCA with a complete replacement of
coarse aggregate with the recycled. It could be, hence, said
that when the fine RCA are used for the structural concrete
members with the 100% coarse RCA the fine aggregate can
be replaced up to 60% by fine RCA.
(3) The steam curing method did not detrimentally affect the
strength development of the recycled aggregate concrete
up to 28 days in this study.
(4) The recycled aggregate concrete for the structural member
applications achieved sufficient resistance to the chloride
ion penetration and the resistance can be even more reduced
by adding fly ash.
(5) The measured carbonation depth increased with the addition
of fly ash when the replacement level of fine aggregate
by RCA was 30% or below. However, this relationship
became unclear at the levels of 60% or greater. Based on
the measured carbonation depth, mostly below 10 mm,
and comparison to other studies, the concrete using RCA
was thought to be able to attain a satisfactory carbonation
resistance.
From the results in this study, it is believed that the recycled
aggregate processed from construction and demolition waste can
successfully be applied for production of structural member concrete
provided that a proper mix design and curing method are
used.