FRESH AND HARDENED PROPERTIES OF RECYCLED CONCRETE AGGREGATE MODIFIED BY IRON POWDER AND SILICA

Abstract

In recent years, significant attention has been given by researchers to use recycled concrete
aggregate (RCA) instead of natural aggregate (NA) in concrete mixes to decrease the demand on the natural
aggregate resources and to reduce its environmental effects. This research work was carried out to investigate
the efficiency of using RCA in concrete mixes in place of natural coarse aggregate. 90 cubes of (100 x 100 x
100 mm) with different percentages of RCA (0%, 30%, 45%, and 60%) at water to cement ratio of 0.4 and
using 0% and 2.5% super plasticizer were casted. For that mix which was prepared with 45% of RCA 54 cubes
of (100 x 100 x 100 mm) were casted with different percentages of iron powder in place of fine aggregate (10%,
15%, and 20 %). Hardened test was examined to measure the compressive strength after 7, 14 and 28 days of
curing. Fresh property test was conducted (Slump test) to study the efficiency of using RCA on workability.
The results of the study showed that the fresh property was decreased by increasing the RCA replacement. The
compressive strength of the RCA was deceased by increasing the RCA replacement. For specimens casted
using 45% of the RCA the compressive strength was increased by increasing iron powder replacement.