Use of Industrial Waste as Aggregate: Properties of Concrete - Recycled Aggregate in Concrete - page 117

addition of CBA by comparison with conventional concrete is due to the increased
demand of water during the mixing of concrete with CBA.
Andrade et al. ( 2007 ) reported that the water, absorbed during mixing, is
desorbed at a later stage and increases bleeding. Decreases in water/cement (w/c)
ratio and addition of air-entraining admixture can significantly decrease bleeding
of concrete with CBA (Andrade et al. 2009 ; Ghafoori and Bucholc 1996 ).
4.2.1.3 Density
As the density of CBA is considerably lower than that of normal fine and coarse
aggregates, the inclusion of CBA aggregate in concrete decreases its unit weight or
density. Another factor that is pointed out in some of the studies is the higher w/c
ratio of concrete with CBA than in conventional concrete, which introduces more
air bubbles in the concrete mix. Figure 4.3 shows the density of concrete with two
different size ranges (Lee et al. 2010 ). The size ranges of the CBA aggregate
present in concrete mixes F1 and F2 are, respectively, 0-2 and 2-8 mm. A sig-
nificant decrease in density was observed due to the incorporation of CBA
aggregate in concrete. Yüksel et al. ( 2007 ) reported about 30 % reduction in fresh
density of concrete briquette (block) with CBA used to replace 50 % (in volume)
of 0-4 mm sand.
4.2.2 Hardened Concrete Properties
4.2.2.1 Density of Concrete
Just like for fresh-state density, the incorporation of CBA aggregate also decreases
the dry density of hardened concrete due to the low bulk density of CBA aggregate.
Experimental results of two different types of concrete are presented in Fig. 4.4 .
Fig. 4.3 Density of concrete
with CBA aggregate (Lee
et al. 2010 )