Civil Engineering Reference
In-Depth Information
Fig. 3.12 Relationship
between Los Angeles
abrasion value and
compressive strength (Topçu
1997
)
Fonteboa and Martınez-Abella (
2007
) found lower abrasion values for coarse
aggregates than that for fine aggregates.
The Los Angeles abrasion value of CDW aggregate prepared from high-
strength concrete is higher than that prepared from low-strength concrete (Hasaba
et al.
1981
; De Juan and Gutiérrez
2009
; Tabsh and Abdelfatah
2009
). The change
in Los Angeles value with respect to compressive strength value is presented in
Fig.
3.12
(Topçu
1997
). The Los Angeles abrasion value of CDW aggregate can
be improved by changing the crushing procedure. Li et al. (
2009
) determined the
Los Angeles abrasion value of 24.2 % for CDW aggregate crushed using a jaw
crusher, and a value of 20 % when an impact crusher is used after crushing of
CDW aggregate by a jaw crusher.
3.5.4.2 Strength and Toughness
The strength of aggregate affects the strength properties of the resulting concrete.
The strength of aggregate depends on the composition, texture and structure of
aggregate (Neville
1981
). In some reports, the crushing strength of CDW aggre-
gate is reported as a 10 % fines value. In the 10 % fines value determination test, a
higher numerical result denotes a higher strength of aggregate (Neville
1981
).
According to BS 882: 1992, a minimum value of 150 kN is required for aggregate
to be used in structural elements. On the other hand, a minimum of 100 kN is
required for minor structural elements, pre-stressed concrete elements, road con-
struction and insulation barriers (BS 882: 1992 and ASTM D448-03: 2000).
According to BS 882:1992 and ASTM 2940-03:2000 specifications, a 10 %
crushing value of 50 kN is sufficient for aggregate to be used in concrete prepared
for applications such as non-structural element, base course, embankment and fill
(Tam and Tam
2007
).
The strength of CDW aggregate, reported as the 10 % crushing value, is pre-
sented in Table
3.8
. The crushing value of CDW aggregate is in all cases lower than
that of normal aggregate. However, in the majority of the cases, this value meets the
100 kN criteria for various applications specified in the BS and ASTM standards.
