Civil Engineering Reference
In-Depth Information
Where a, b and s are the regression coefficients whose values are 8917, 2348 and
0.85 respectively.
From the experimental results in various references and also their own, Xiao
et al. (
2006b
) proposed the following expression to relate the CS and the MO of
RCAC:
10
5
2
:
8
þ
40
:
1
f
cu
E
¼
ð
5
:
12
Þ
5.3.5 Flexural and Shear Performances
Several investigations were undertaken to understand the flexural and shear per-
formances of concrete containing RCA. Here, some results will be highlighted
from relevant references.
Razaqpur et al. (
2010
) observed higher ultimate FS in reinforced RCAC beams
than in conventional concrete beams regardless of the source of RCA or the
tension and steel contents of the beam. The RCAC were prepared using a new
mixing method where the total mortar content (new and old) in RCAC and con-
ventional concrete were the same. The flexural failure modes and cracking patterns
of both types of concrete were similar. The mid-span deflections of both types of
concrete also met the American ACI 318 M-05 specification limit. However, the
RCAC beams showed lower cracking moments and slightly smaller crack spacing
than the conventional concrete beam.
Sato et al. (
2007
) observed higher flexural deflection for reinforced concrete
beams containing RCA than for conventional concrete under the same moment and
w/c value. In these conditions, they observed similar ductility factors, ultimate
moments and crack spacing in the control concrete beam as well and the concrete
beams containing coarse or fine RCA but the crack width of concrete containing
coarse or fine RCA were larger than that observed in the conventional concrete
beam. The crack spacing and crack width of the RCAC beam containing coarse
RCA were in the ranges of 0.92-1.37 and 0.57-1.3 times those of the conventional
concrete beam respectively. The same parameters for RCAC containing fine RCA
were 0.74-1.26 and 1.1-1.7 times those of the conventional concrete. They did not
detect any cracking or deflection for 1 year under wet conditions but observed
many cracks and two times more deflection than in the conventional concrete
beam under dry condition when the concrete beams containing fine RCA and
conventional concrete were kept under sustained bending moment equivalent to
100 N/mm
2
in tension rebar stress in reinforced concrete sections. Regardless of
the type of aggregate, the ultimate moments of the concrete beams can be pre-
dicted from the Japanese code, JSCE 2002e.
Tsujino et al. (
2007
) investigated the flexural performance of concrete con-
taining
untreated
and
oil-coated
low
and
medium
qualities
RCA
as
coarse
