Concrete is made of cement paste, coarse aggregates, fine aggregates, and with or without other
additional material. One type of coarse aggregates is the utilization of concrete wastes, as
coarse aggregates, to be recycled, which is known as recycled concrete. Solid wastes which
come from concrete damage caused by various natural disasters and demolitions of old
structures can harm the stability of the environment.
One of the major challenges of our present society is the protection of environment. Some of the
important elements in this respect are the reduction of the consumption of energy and natural raw
materials and consumption of waste materials. These topics are getting considerable attention
under sustainable development nowadays. The use of recycled aggregates from construction and
demolition wastes or from hardened leftover concrete is showing prospective application in
construction as alternative to primary (natural) aggregates. It conserves natural resources and
reduces the space required for the landfill disposal.
In this paper, the compressive strength and the tensile splitting strength of recycled aggregate
concrete (RAC) with different replacement percentages of recycled coarse aggregate (RCA)
were investigated experimentally. The recycled aggregate was obtained from crashed laboratory
concrete specimens. Concrete specimens were made and tested with different RCA replacement
percentages of 0%, 30%, 50%, 70% and 100%, respectively evaluated at 7, 14 and 28 days

curing periods. The fresh and hardened properties of new concrete were studied and compared
with concrete made using natural materials or aggregates. Significant differences were observed
between the properties of the recycled aggregates of various particle size groups, while the
crushing age had almost no effect. The properties of the concrete made with recycled aggregates
were inferior to those of concrete made with virgin aggregates. Compressive strength of recycled
aggregate concrete (RAC) showed a decrease of up to less than 30% compared to natural
aggregate concrete (NAC). RAC water absorption was higher compared to NAC because of
remains of mortar on its rough surface


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