Civil Engineering Reference
In-Depth Information
improvement of the CS of RCAC after prolonged curing. The gain in CS also
increased with the RA and RCA contents in concrete.
5.3.2 Splitting Tensile Strength
Like for CS, the splitting tensile strength (STS) of concrete containing RA or RCA
is normally lower than that of conventional concrete and increasing the addition of
CDW aggregate into concrete further lowers it. Table
5.11
shows some typical
data. The causes for CS reduction are also responsible for STS reduction.
According to de Brito and Alves (
2008
) the lower mechanical properties of the
recycled aggregates when compared to the natural ones lead to a fall in the STS of
the concrete containing CDW aggregate as the substitution rate increases.
After analysing literature data de Brito and Robles (
2010
) reported that the
replacement ratio of natural aggregate by CDW aggregate had slightly less effect
on the reduction in STS than that observed in CS. Table
5.12
shows the differences
in 28-day STS and CS of RAC and RCAC from conventional concrete determined
from the data presented in various references. A great variation in the reduction in
STS due to the incorporation of RCA or RA in concrete was observed, probably
due to the variations in experimental parameters and properties of CDW aggre-
gates used in the various studies.
From the results presented in Table
5.12
it can also be concluded that the
inclusion of RA or RCA into concrete had little impact on STS or that the CDW
aggregate mixes had higher STS than conventional concrete up to a given
replacement level. This is probably due to the improvement in aggregate-cement
paste bond strength, which induces a higher increase in STS than in CS (Kou and
Poon
2008
).
Corinaldesi (
2009
) observed similar STS for RCAC prepared with and without
mixing FA into Portland cement. Etxeberria et al. (
2007a
) observed higher STS of
Table 5.11
28-day splitting tensile strength of concrete containing various amount of CDW
aggregate
Reference
Type of aggregate
Tensile strength
(MPa)/substitution level (%)
Gomez-Soberon (
2002
)
RA/fine ? coarse
3.7/0; 3.7/15; 3.6/30; 3.4/60; 3.3/100 (v/v)
Gonzalez-Fonteboa and
Martinez-Abella
(
2008
)
RCA/coarse
3.15/0; 3.00/50 (v/v)
Kou and Poon (
2008
)
RCA/coarse
2.43/0; 2.40/20; 2.35/50; 2.26/100 (v/v)
