Civil Engineering Reference
In-Depth Information
and Brito, 2007; Brito and Alves, 2010) state an improvement. This reduction
is attributed to reductions in physical and mechanical properties from the
recycled aggregate itself, since it generally has abrasion resistance values
lower than those of conventional aggregates.
The high abrasion of recycled concrete aggregate partly reflects the large
amount of mortar adhered to the natural aggregate (Tavakoli and Soroushian,
1996). This behaviour also occurs to brick ceramic recycled aggregate (Brito
et al., 2005).
The poor performance by recycled concrete may be avoided when preparing
high compressive strength concrete. limbachiya et al. (2000) found similar
abrasion resistance of 50, 60 and 70 MPa concrete produced with 100%
recycled aggregate concrete and Poon et al. (2002) found a 60 MPa recycled
concrete abrasion around 12% higher than conventional concrete abrasion.
This probably occurs due to the high abrasion resistance of the high-strength
mortar.
Brito and Alves (2010) state the abrasion resistance of concrete with
recycled aggregates tends to increase (less loss of mass) due to the greater
adherence between particles provided by the more porous surface of recycled
aggregates.
It may be concluded that even with a possible decrease in the abrasion
resistance for recycled aggregate concrete for medium strength, it is possible
to produce recycled concrete with a satisfactory abrasion resistance. For this,
it is necessary to increase the concrete mortar abrasion resistance.
14.4.8 Drying shrinkage
According to Mehta and Monteiro (2008), the particle size distribution, the
maximum size, and the shape and texture of the aggregates are factors that
influence the concrete drying shrinkage. However, the aggregate's modulus
of deformation is considered the most important factor.
Corinaldesi (2010) points out that when the finer coarse recycled aggregate
fraction is used to produce concrete, low values of shrinkage are detected at
an early age (7 days). Corinaldesi and Moriconi (2010) found significantly
lower drying shrinkages in recycled aggregate concretes. In both cases, the
authors suggest the 'curing effect' as the reason for this behavior, propitiated
by the pre-soaking of water into porous of recycled aggregate particles.
However, the great majority of authors, such as ravindrarajah and Tam
(1985, 1987b) Tavakoli and Soroushian (1996), Sagoe-Crentsil et al. (2001),
Poon et al. (2002), Ajdukiewicz and Kliszczewicz (2002), Shayan and Xu
(2003) and Dhir et al. (2004b), had drying shrinkage 12% to 61% higher in
recycled aggregate concrete than conventional concrete. Besides, there are
studies that show increases up to 100% (ravindrarajah and Tam, 1987a;
Katz, 2003).
