grading used in porous 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 porous concrete. The aggregate
used should meet requirements of ASTM D448 and C33/C33/M. fine aggregate
content is limited in porous 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 porous concrete mass.
quality in porous 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
porous concrete mixture. Unit weights of aggregates should be determined in
accordance with ASTM C29/C29M.
and Putman2010)In general, as the Cu of the aggregate
increased that is, the gradation became less uniform or single sized and more
well-graded the strength also increased,
whereas the porosity and permeability decreased.
compressive, split-tensile, and flexural strengths are inversely related to
permeability. As the permeability increased, the strength properties of porous
concrete mixtures decreased. The compressive, split-tensile, and flexural
strengths increased with the Cu to points, after which a decrease in
strength was observed
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
et al. 2013 studied the use of sea shell by products in partial replacement of
aggregates in porous 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
et al.2014 studied three different types of coarse aggregate namely pea gravel,
limestone and ablend of RCAB of max. Size 9.5mm.
use of waste material such as recycle aggregate in porous concrete further
increases its environmental benefits by reducing the amount of materials
extracted from quarries and riverbeds. Li and Rizvi et al.
Tittarelli et al. /2014) no-fines concretes with compressive strength ranging from 7 to 30
MPa were obtained by changing the w/c
0.41 to 0.34 and the a/c ratio from 8 to 4.