1. The storm water can rapidly filtered into soil, and the groundwater
resources can recharge.
2. The surface is air and water permeable and the soil below can
be kept wet. It improves the environment of road surface.
3. The pervious concrete pavement can absorb the noise of vehicles,
which creates quiet and comfortable environment.
4. The pervious concrete pavement materials have holes that can
cumulate heat. The pavement can adjust the temperature and
humidity of the Earth’s surface and eliminates the phenomenon
of hot island in cities.
Since its various environmental benefits, pervious concrete is
one of the most important emerging technologies for sustainable
facilities and infrastructure. Therefore, pervious concrete is recognized
as the best solution for storm water management and one of
the key elements of sustainable development by US Environmental
Protection Agency [2,3].
The mix design of pervious concrete is different from the conventional
one. The materials mix design of PC is composed of Portland
cement, uniform coarse aggregate (allowing relatively little
particle packing), approximately 7% fine aggregate by weight of
total aggregate and water. The addition of a small amount fine
aggregate as sand provided additional compressive strength, better
durability and high resistance to freeze/thaw cycles. Generally,
pervious concrete mix consists of 270–415 kg m3 of cement,
1190–1480 kg m3 of aggregate and water to cement ratio ranged
from 0.27 to 0.40. The typical 28-day compressive strength ranges
from 3.5 to 28.0 MPa and permeability coefficient varies from 0.2
to 5.4 mm s1 [2,3]. Additionally, the characteristic pore sizes
range from 2 to 8 mm depending on the type of aggregates and
the method of compaction [2,7].
Many previous studies have reported the proprieties of pervious
concrete in varying the water-to-cement ratio, aggregate-tocement
ratio, aggregate sizes, binder material type or effects of compaction
energy [1–8]. However, the number of publications on the
method for the design of pervious concrete mix is very limited.
There can be mentioned here the American concrete institute
method [2], Zouaghi’s method [8] and Zheng’s method [9]. Moreover,
these design methods are not complete; they present many
disadvantages, as shown in Table 1. For example, they do not indicate
how to determine the w/c ratio or they do not take into account
the effect of compaction on the properties of concrete, etc.
Therefore, there are no recognizing methods to establish the mix
design of pervious concrete at the present time, the pervious concrete
mixture proportions are always selected from experimental
studies [3].
2. Principal of the proposed mix proportioning method
In this paper, a modified method is proposed for mix design of
PC. This method is based on the quantification of the layer of
cement paste coating the gravel and on the assumption that the
cementious paste act only as a coating; it does not fulfill the void
among the grains of gravel. This method of mixture proportioning
is divided into three steps: the determination of aggregate volume,
cement paste volume and water–cement ratio.
2.1. Determination of aggregate volume
Aggregate occupies most of the pervious concrete’s volume and
is the principal load-bearing component. In this section, four
hypotheses were adopted for the determination of aggregate
volume.
Hypothesis #1. To facilitate the calculation, the aggregate is
assumed of spherical shape. Only a perfect sphere can be characterized
by a single value of size which is the diameter. The purpose
of this equivalent sphere hypothesis is to describe an object in
three dimensions by a single value.
Fig. 1 shows the components of ordinary concrete in which
aggregates are spaced by the cement paste. Assuming that, the
aggregates are compacted at maximum to have the solid volume