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Aggregates
grading used in pervious concrete are normally either single size coarse
aggregate or grading between 19-9.5 mm. rounded and crushed aggregates, both
normal and lightweight, have been used to make pervious concrete. The aggregate
used should meet requirements of ASTM D448 and C33/C33/M. Fine aggregate
content is limited in pervious concrete mixtures because it tends to compromise
the connectedness of the pore system. The addition of fine aggregate may
increase compressive strength and density but correspondingly reduce the flow
rate of water through the pervious concrete mass.

Aggregate quality in pervious concrete is equally important
as in conventional concrete. Flaky or elongated particles should be avoided.
The narrow-grade coarse aggregate should be hard and clean, and free of
coatings such as dust or clay, or other absorbed chemicals that might
detrimentally affect the paste/aggregate bond or cement hydration. Aggregate
sources with a service record of acceptable performance are preferable. In the
absence of a source with an acceptable service record, a combination of tests could
be conducted to provide a basis for assessing the suitability of a candidate
aggregate for incorporation into a pervious concrete mixture. Unit weights of
aggregates should be determined in accordance with ASTM C29/C29M (Neptune
and Putman 2010). In general, as the Cu of
the aggregate increased that is, the gradation became less uniform or single
sized and well-graded, the strength increases, whereas the porosity and
permeability decreases.

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The
compressive, split-tensile, and flexural strengths are inversely related to
permeability. As the permeability increased, the strength properties of pervious
concrete mixtures decreased. The compressive, split-tensile, and flexural
strengths increased with the Cu to points, after which a decrease in
strength was observed. This is consistent with the literature; as the aggregate
size decreases, the binding area increases and results in an improvement of the
strength (Yang and Jiang 2003).

 

Nguyen
et al. 2013 studied the use of sea shell by products in partial replacement of
aggregates in pervious concrete both as an environment friendly building
material and a potential component. (W.T. Kuo et al 2013) demonstrated Washed
municipal solid waste incinerator bottom ash (MSWIBA) of maximum size 12.5 mm
was used as a substitute for natural aggregate and results shows that there is
no significant difference in connected porosities, compressive strength and
permeability coefficient.

 

Gaedicke
et al. 2014 studied three different types of coarse aggregate namely pea
gravel, limestone and a blend of RCAB of maximum size 9.5mm.

The
use of waste material such as recycle aggregate in pervious concrete further
increases its environmental benefits by reducing the amount of materials
extracted from quarries and riverbeds. Li and Rizvi et al

.

F.
Tittarelli et al. 2014. Evaluated no-fines concrete with
compressive strength ranging from 7 to 30 MPa by changing the w/c
from
0.41 to 0.34 and the a/c ratio from 8 to 4.

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