Use of Industrial Waste as Aggregate: Properties of Concrete - Recycled Aggregate in Concrete - page 121

Fig. 4.8 Splitting tensile
strength of concrete with
CBA aggregate (Aggarwal
et al. 2007 )
with CBA. For a given content of admixture, the flexural strength of CBA concrete
became higher than that of control concrete. Their results are presented in Table 4.1 .
4.2.2.4 Splitting Tensile Strength
The splitting tensile strength of concrete decreases as replacement percentage of
fine aggregate by CBA rises and increases with the curing age (Agarwal et al. 2007 ).
The highest and lowest gains in splitting tensile strength were observed at 20 and
50 % replacement of fine aggregates with bottom ash, respectively (designated M2
and M5). Plain concrete reaches 64, 77 and 88 % of 90-day strength at 7, 28 and
56 days of curing, respectively, whereas these values for concrete with CBA at 20,
30, 40 and 50 % replacement levels were in the ranges of 62-86 %, 60-83 %,
56-83 % and 53-84 %, respectively. Their results are presented in Fig. 4.8 .
Ghafoori and Bacholc ( 1996 ) reported that the inclusion of CBA in concrete
had more influence on splitting tensile strength than on compressive strength. At
low cement content (500 lb/yd 3 of concrete), the splitting tensile strength of
concrete with CBA aggregate was lower than that of conventional concrete at the
early ages of curing and was similar after 56 days of curing. However, the initial
dormant period of CBA concrete can be overcome by adding admixtures to this
type of concrete. On the other hand, the splitting tensile strength of both types of
concrete was similar for the concrete mix with 600 lb/yd 3 of cement. These results
are presented in Fig. 4.9 .
4.2.2.5 Static Elastic Modulus
The static elastic modulus of concrete with CBA is significantly lower than that of
conventional concrete. Ghafoori and Bacholc ( 1996 ) reported that the higher
elastic modulus value of conventional concrete than that of CBA concrete was due
to the lower paste porosity of conventional concrete than that of CBA concrete, as
the w/c value of conventional concrete was lower than that of CBA concrete, as
well as to the higher bulk density of natural sand aggregate than that of CBA