ABSTRACT in large exposed areas such as parking

 

 

ABSTRACT

 

 

 

 

Pervious concrete layer is one of the effective
concrete pavement mixes to address a number of important environmental issues,
such as recharging groundwater and reducing storm water runoff. Portland Cement
Pervious Concrete (PCPC) is produced by eliminating most or all of the fine
aggregate in the mix, which allows interconnected void spaces to be formed in
the hardened matrix. These interconnected void spaces allow the concrete to
transmit water at relatively high rates. effect of different size fractions of
coarse aggregate, water-to cement ratio, cement content, and coarse aggregate
volume on the relationships between compressive strength, tensile strength,
porosity, and permeability. The mixtures used in this study consisted of either
one or two aggregate sizes. Linear regression relationships were developed to
establish relationships between density and porosity, compressive strength and
permeability, tensile strength and permeability, and compressive strength and
porosity. The results showed that properties such as permeability, porosity,
are significantly affected by using either one or two coarse aggregate sizes.

We Will Write a Custom Essay Specifically
For You For Only $13.90/page!


order now

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ii

Introduction

 

Pervious concrete is a special class of concrete
that has a relatively high proportion of large sized pores (2–8 mm typically),
and a larger volume fraction of such pores (15–30% typically).This is achieved
by gap grading the coarse aggregates and either eliminating or minimizing the
volume of fine aggregates in the mixture. Pervious concretes have been found to
be very effective in recharging groundwater and conserving water resources,
making it an effective storm water management tool when used as a surface
course in large exposed areas such as parking lots, residential streets,
driveways and manhole cover, low volume pavements, and sidewalks etc. Recently
there has been considerable interest in using pervious concrete to mitigate the
tire-pavement interaction noise in concrete pavements.

 

In 1852, Richard Langley used a
predecessor of pervious concrete for the construction of two concrete houses on
the Isle of Wight in the United Kingdom. This concrete consisted of only coarse
gravel and cement.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure
(1): Slab of pervious concrete allow water to pass
through the porous.

 

 

 

 

1

 

With the population growth and the continual
urbanization, our cities are being covered with the impervious surface areas
such as residential and commercial buildings. Because of the lack of water and
air permeability of the common concrete pavement, the storm water is not
filtered underground, the runoff is rapidly increased. Therefore, the drainage
system gets overloaded and flash flooding becomes inevitably. In addition, with
the impervious surface, it is difficult for soil to exchange heat and moisture
with air; therefore, the temperature and humidity of the Earth?s surface cannot
be adjusted. This brings the phenomenon of greenhouse and hot land effects in
city. At the same time, the plash on the road during a rainy day reduces the
safety of traffic of vehicle and foot passenger.

 

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
element.

 

1.   
Pervious concrete consists of
cement, water and coarse aggregates (no fine) so due interconnected voids, 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 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.

 

Unlike conventional concrete, which has void ratio from 3-5%, pervious
concrete can have void ratio from 15-30% depending on its application. Pervious
concrete characteristics differ from conventional concrete are

 

1.   
Compared to conventional
concrete, pervious concrete has low compressive strength, high permeability and
lower unit weight approx 65-75% of conventional concrete.

 

2.   
Higher hydraulic conductivity than conventional
concrete.

 

 

 

 

 

 

 

 

 

2

Basic Principle

 

Pervious concrete mainly consists of coarse
aggregate, Portland cement and water. It is different from conventional
concrete in that it contains no fines in the initial mixture. The aggregates usually
consist of a single size and are bonded together at its point of contact by a
paste formed by the cement and water. The result is a concrete with high
percentage of interconnected void that, when functioning correctly, permit the
rapid percolation of water through concrete. Compared to conventional to
concrete, pervious concrete has lower compressive strength and higher
permeability.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure
(2): View of pervious and conventional concrete in same
weather condition.

 

 

Historical Back Ground

 

In Europe, pervious concrete, most commonly
referred to as Gap graded concrete, has been used in the construction industry
for approximately 150 years. The initial usage of this type of concrete in
Europe was in applications such as prefabricated panels, steam-cured blocks or
load- bearing walls for single and multi-story houses and, in some instances,
in high-rise buildings.

 

In 1852, Richard Langley used a
predecessor of pervious concrete for the construction of two concrete houses on
the Isle of Wight in the United Kingdom. This concrete consisted of only coarse
gravel and cement. It is not mentioned in the published literature again until

 

3

 

1923, when a group of 50 two-story houses were
built with clinker aggregate in Edinburgh, Scotland. In the late 1930s, the
Scottish Special Housing Association Limited adopted the use of pervious
concrete for residential construction. By 1942, pervious concrete had been used
to build over 900 houses.

 

A larger amount of pervious
concrete was used after World War II when sufficient volumes of building brick
could not be produced to support housing needs. Less expensive building
construction methods were explored and pervious concrete was one of them. In
some countries, coarse aggregate was used for the production of pervious
concrete and in other countries, brick rubble was utilized. Over time, the
brick rubble was exhausted and replaced by crushed or natural coarse aggregate.
Lower production costs led to the acceptance of pervious concrete as a building
material. Pervious or gap graded concrete was mostly used in construction
housing applications.

 

Many new houses were built using
pervious concrete in the United Kingdom, Germany, Holland, France, Belgium,
Scotland, Spain, Hungary, Venezuela, West Africa, the Middle East, Australia,
and Russia.

 

After World War II, porous
concrete became wide spread for applications such as cast-in-place load-bearing
walls of single and multi-storey houses and, in some instances in high-rise
buildings, prefabricated panels, and stem-cured blocks (Ghafoori et al. 1995).
Also applications include walls for two-story houses, load-bearing walls for
high-rise buildings (up to 10 stories) and infill panels for high-rise
buildings (Tennis et al. 2004).

 

 

 

 

Applications of Pervious Concrete

 

Pervious concrete is only as good as its design and
installation. The initial design and proper installation is absolutely critical
for long term durability and proper functioning of the entire system. It is
important for the designer and contractor to be fully aware of the possible
consequences of improper design and installation, and to have a full
understanding of the function of each component in a pervious pavement system.

 

It is
used in following:

 

1.       
Low-volume traffic pavements

 

2.       
Sidewalks and pathways

 

3.       
Parking areas

 

4.       
Sport courts

 

5.       
Noise barrier

 

6.       
Slope stabilization

 

7.       
Well linings

 

8.       
Tree grates in sidewalks

 

9.       
Foundations

 

10.   
Floors for greenhouses

 

11.   
Aquatic amusement centres

 

12.   
Hydraulic structure

 

13.   
Artificial reefs

 

14.   
Pavement edge drains.

 

Pervious concrete can replace
traditional impervious pavement for most pedestrian and vehicular applications
except high-volume/high-speed roadways. Pervious concrete can be designed to
handle heavy loads, but surface abrasion from constant traffic will cause the
pavement to deteriorate more quickly than conventional concrete, due to this
Pervious concrete has performed successfully in pedestrian walkways, sidewalks,
driveways, parking lots, and low-volume roadways, tennis courts etc.

 

The proper
utilization of pervious concrete is a recognized best management practice by
United States Environmental Protection Agency (EPA) for providing first flush
pollution control and storm water management. As the environmental benefits
from pervious concrete allow it to be incorporated into municipal green
infrastructure and low impact development programs. In addition to providing
storm water volume and quality management, the light

 

 

7

 

colour of concrete is cooler than conventional asphalt and
helps to reduce urban temperatures and improve air quality.

 

1.    Low-volume traffic pavements: Pervious concrete is used in low volume traffic areas (the roads which connect rural and
urban areas with the main roads). Pervious concrete comprises the surface layer
of the permeable pavement structure and consists of Portland cement, open-graded
coarse aggregate (typically 5/8 to 3/8 inch), and water. Admixtures can be
added to the concrete mixture to enhance strength, increase setting time, or
add other properties. The thickness of pervious concrete ranges from 4 to 8
inches depending on the expected traffic loads.

 

2.   
Sidewalks and pathways: Pervious
concrete consists of cement, water and coarse aggregates (no fine aggregates). So these have higher water and
air conductivity than conventional concrete and the soil below can be kept wet.
It improves the environment and adjusts the temperature and humidity of the
Earth?s surface.

 

3.   
Parking areas: After proper compaction of the
native soil, geotextile febric is usually
placed to protect against fine migrating up into the aggregate base. The
aggregate base (recharge bed) is placed and compacted and then the ready mixed
concrete is placed, spread and levelled with various types of vibratory screeds
or friction tube. This followed by some form of surface rolling process
designed to compact approximately top 13mm (.5 inch) of the surface. Very soon
after pervious concrete is placed, joint should be cut by modified rolling
device behind the final rolling process.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure (5): View of parking area made up of
pervious and impervious both the concrete.

 

 

 

 

8

 

4.   
Sport courts: Sport Base has been designed for
use in applications that require a temporary
court, or in areas where concrete is not feasible or practical. When drainage
is a design requirement, Sport Base may provide a better solution that pervious
concrete. The following factors should be considered when choosing between
Sport Base and pervious concrete.

 

·     
Drainage: The limiting factor in any Sport
Base installation, as with pervious concrete, will be the drainage rate of the base over which it is installed.
When proper sub-base preparation is followed, Sport Base tiles will easily meet
any required drainage specification.

 

·     
Portability: Sport Base is very easy to
install and to remove, whereas pervious concrete
is a permanent surface.

 

·     
Easy installation: A full court using Sport Base
tiles can be installed in a matter of hours.
There is no additional time required for mixing, curing or drying.

 

·     
Safety: Sport Base tiles provide
excellent shock absorption, resulting in a much safer surface with a lower probability of injury.

 

·     
Environmentally Friendly: Sport
Base tiles are made from 100% recycled materials. Even materials that have been recycled multiple times can be used.

 

·     
Repair and maintenance: in areas
of high sedimentation, pervious concrete systems will lose permeability as sediment builds up in the voids. An
aggressive maintenance schedule of vacuum sweeping and high pressure washing is
required to remove sediment build up. If sedimentation occurs around the edges
of Sport Base tiles, they can be independently removed in order to clean out
the sediment build up, and then put back in place.

 

5.     
Noise barrier: The open structures of the
pervious concrete causes a difference in arrival time between direct and reflected sound waves. This difference
decreases the noise level intensity, causing porous concrete pavements to
absorb the sound. This property has drawn the interest of many researchers to
create quiet pavements.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

9

6.     
Slope stabilization: When the
surface is not level, the depth of
the pavement

 

and sub base must be designed to meet the desired
runoff goals, or more complex options for handling water flow may be used.
Pervious concrete

 

pavements have been placed successfully on slopes
up to 16%. In these cases, trenches have been dug across the slope.

 

7.      Well lining: Using sufficient paste to coat and bind the aggregate particles together creates a system
of highly permeable, interconnected voids that drains quickly.

Figure
(6): Elevation and plan view

 

drawings of sloped installation.

 

 

 

Typically, between 15% and 25% voids
are achieved in the hardened concrete, and flow rates for water through
pervious concrete typically are around 480 in. /hr (0.34 cm/s, which is
5gal/ft2/ min or 200 L /m2/min.

 

This percolation capacity of pervious concrete allows
continuous lifting of water from well and recuperation of water in the well
from sides/base of well without any failure or damage.

 

8.      Foundations: Structures those are constructed near water bodies or in
the bank of water bodies. There is
possibility of water logging around the structure, to protect structure from
dangers due to water pounding/logging around the structure. Construct
foundation with pervious concrete to drain water under ground and keep
surrounding clear.

 

 

 

 

 

 

 

 

 

 

 

 

10

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure (7): Show drain of water to underground soil.

 

 

 

 

Pervious concrete properties

 

1.  
Fresh property:

 

The plastic pervious concrete mixture
is stiff compared to traditional concrete. Slumps, when measured, are generally
less than 3?4 in. (20 mm), although slumps as high as 2 in. (50 mm) have been
used. When placed and compacted, the aggregates are tightly adhered to one
another and exhibit the characteristic open matrix.

 

For quality control
or quality assurance, unit weight or bulk density is the preferred measurement
because some fresh concrete properties, such as slump, are not meaningful for
pervious concrete. Conventional cast cylinder strength tests also are of little
value, because the field consolidation of pervious concrete is difficult to
reproduce in cylindrical test specimens, and strengths are heavily dependent on
the void content. Concrete working
time typically is reduced for pervious concrete mixtures. Usually one hour
between mixing and placing is all that is recommended. However, this can be
controlled using retarders and hydration stabilizers that extend the working
time by as much as 1.5 hours, depending on the dosage.

 

 

 

 

 

 

 

 

11

2.  
Hardened properties:

 

a.   Density and
porosity: The density of
pervious concrete depends on the properties and proportions of the materials used, and on the compaction
procedures used in placement. In-place densities on the order of 1600 kg/m3 to
2000 kg/m3 are common, which is in the upper range of lightweight concretes. A
pavement 5 in. (125 mm) thick with 20% voids will be able to store 1 in. (25
mm) of a sustained rainstorm in its voids.

 

b.   Permeability: The flow rate through pervious concrete depends on the
materials and placing operations.
Typical flow rates for water through pervious concrete are (288 in./hr or 0.2
cm/s) to (770 in./hr or 0.54 cm/s), with rates up to (1650 in./hr or 1.2 cm/s)
and higher having been measured in the laboratory (Crouch 2004).

 

c.    Compressive
strength: Pervious concrete
mixtures can develop compressive strengths
in the range of 3.5 MPa to 28 MPa, which is suitable for a wide range of
applications. Typical values are about 17 MPa. As with any concrete, the
properties and combinations of specific materials, as well as placement
techniques and environmental conditions, will dictate the actual in-place
strength.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure (8): Relationships among porosity, strength and permeability for
pervious concrete (Sriravindrarajah R
et al).

 

 

 

12

 

d. Flexural strength: Flexural strength in pervious concretes generally ranges between about 1 MPa and 3.8 MPa. Many factors
influence the flexural strength, particularly degree of compaction, porosity,
and the aggregate:cement (A/C) ratio. However, the typical application
constructed with pervious concrete does not require the measurement of flexural
strength for design.

 

e.    Shrinkage: Drying shrinkage of pervious concrete develops sooner, but
is much less than conventional
concrete. Specific values will depend on the mixtures and materials used, but
values on the order of 200*10-6 have been reported
(Malhotra 1976), roughly half that of conventional concrete mixtures. The
material?s low paste and mortar content is a possible explanation. Roughly 50%
to 80% of shrinkage occurs in the first 10 days, compared to 20% to 30% in the
same period for conventional concrete.

 

f.   
Durability:

 

·     
Freeze-thaw resistance: Freeze-thaw resistance of pervious concrete in the field appears to depend on the saturation
level of the voids in the concrete at the time of freezing. In the field, it
appears that the rapid draining characteristics of pervious concrete prevent
saturation from occurring. Anecdotal evidence also suggests that snow covered
pervious concrete clears quicker, possibly because its voids allow the snow to
thaw more quickly than it would on conventional pavements.

 

Research indicates
that entrained air in the paste dramatically improves freeze-thaw protection
for pervious concrete (Neithalath 2003; Malhotra 1976). In addition to the use
of air-entraining agents in the cement paste, placing the pervious concrete on
a minimum of 6 in. (150 mm) often up to 12 in. (300 mm) or even 18 in. (450

 

mm)   
of a drainable rock
base, such as 1-in. (25-mm) crushed stone, is normally recommended in
freeze-thaw environments where any substantial moisture will be encountered
during freezing conditions (NRMCA 2004).

 

·     
Sulphate resistance: Aggressive chemicals in soils or water, such as acids and sulphates, are a concern to
conventional concrete and pervious concrete alike, and the mechanisms for
attack are similar. However, the open structure of pervious concrete may make
it more susceptible to attack over a larger area. Pervious concretes can be
used in areas of high-sulphate soils and groundwater if isolated from them.
Placing the pervious concrete over a 6-in. (150-mm) layer of 1-in. (25-

 

mm)   
maximum top size
aggregate provides a pavement base, storm water storage, and isolation for the
pervious concrete.

 

13

 

·     
Abrasion resistance: Because of the rougher surface texture and open structure of pervious concrete, abrasion and
ravelling of aggregate particles can be a problem, particularly where
snowploughs are used to clear pavements. This is one reason why applications
such as highways generally are not suitable for pervious concretes. However,
anecdotal evidence indicates that pervious concrete pavements allow snow to
melt faster, requiring less ploughing.

 

 

Conclusions

 

Pervious concrete pavements are a very cost-effective
and environmentally friendly solution to support sustainable construction. Its
ability to capture storm water and recharge ground water while reducing storm
water runoff enables pervious concrete to play a significant role. Pervious
concrete is a smart sustainable option with very high potential. Pervious
concrete is an ideal solution to control storm water, re-charging of ground
water, flood control at downstream and sustainable land management.

 

Unfortunately there is not a
precise recipe for pervious concrete that will yield a high compressive
strength and porosity. Testing along with analysis of existing systems is the
best method for developing a range of values which will lead to a functional
design.

 

Therefore areas subjected to high
volumes should not be constructed of pervious concrete but either asphalt or
conventional concrete. Another concern is maintenance vehicles such as garbage
trucks. Although existing parking lots are able to withstand these vehicles
driving

 

24

 

through the lot, that portion of the pavement where these vehicles load
and unload is heavily damaged. Recommendations are that pervious concrete
should not be placed in areas subjected to repeated heavy loads.

 

Testing of pervious concrete
provides additional information as to selecting appropriate ratios. An A/C
ratio less than 5 in combination with a W/C ratio in the range of 0.35 –0.39
provided the highest compressive strength without jeopardizing permeability.

 

Higher A/C ratios do not supply enough cement and higher W/C ratios tend
to eliminate void spaces.

 

Recommendations are that pervious concrete be
limited to areas that are subjected to small vehicle loads with occasional use
by larger vehicles.

 

 

x

Hi!
I'm Barry!

Would you like to get a custom essay? How about receiving a customized one?

Check it out