BEAHAVIOUR OF REINFORCED CONCRETE BEAMS MADE OUT OF RECYCLED CONCRETE

Concrete is the most widely used construction material. Waste concrete represents an unavoidable
product of concrete industry. It is produced because of the dentolition of concrete structures,
rejected concrete, leftover fresh batches, unwanted elements in pre-cast factories, etc. Waste
concrete is usually discarded in landfills causing very serious euvironmental problems. As the
interest in recycling waste materials is, nowadays, getting an increasing worldwide attention, there
is an environmental incentive for recycling waste concrete with the other types of recycling. In a
previous paper by the author et. al., the properties of recycled concrete have been given a detailed
study. The present investigation is aimed at understanding the effect of using recycled concrete on
the behaviour of reinforced concrete beams. Waste concrete with no information about its previous
mix properties and original strength and quality is used. The waste concrete is manually crushed
and then tested for grading, bulk unit weight, and water absorption. Concrete specimens; cubes,
beams, and cylinders from mixes made out of crushed concrete as a part of coarse aggregate are
prepared and then tested for the uniaxial compression, splitting tension, and flexural strengths. The
uni-axial stress-strain behaviour and the modulus of elasticity are also obtained. A total of eighteen
reinforced concrete beams have been casted and tested to study the behaviour of beams made out
of recycled concrete. This number of beam specimens is divided into six groups. Three groups of
beams are tested for shear loading while the other three groups were aimed for flexural loading.
Both of the flexural and shear groups of beams consisted of three categories each of three beams.
The first category of beams was made out of normal concrete with normal coarse aggregate from
gravel while the other two categories are made out of recycled concrete with coarse aggregate
from crushed concrete. The latter two categories had two various ratios of crushed concrete as a
part of the coarse aggregate. The study brings out the important results that; the use of recycled
concrete reduces both the load carrying capacity and the stiffness of beams while the design
equations, given by various codes, for normal concretemay be iipplicable for reinforced beams
made out of recycled concrete without great loss of accuracy.