PERVIOUS CONCRETE : A CONCRETE STEP TOWARDS A GREENER EARTH

 

 

 

Vaibhav Babtiwale, Zonal In charge (CS)

Ambuja Cements Ltd. Nashik, (Maharashtra)

 

ABSTRACT: At many projects water logging at parking and walkways is the major issue especially during monsoon as pavements and floors are normally impermeable. This results in considerable amount of investment in repairs and providing storm water drain systems, which may get clogged during peak over flow. Besides this there are many other problems that arise due to the above. In such situations it is very important to think about an economical solution which helps in getting rid of all above problems. The best solution to above problem is pervious concrete.

 

1.      WHAT IS PERVIOUS CONCRETE?

 

Pervious concrete pavement is unique and effective means to address important environmental issues and support green, sustainable growth. By capturing storm water and allowing it to seep into the ground due to its design properties, pervious concrete is instrumental in recharging ground water, reducing storm water runoff. In other words we call it as a “RAIN WATER HARVESTING CONCRETE”.

This pavement technology is helpful in creating more efficient land use by eliminating the need of water retention bodies, costly storm water drainage and repair cost, which otherwise would have been incurred due to water accumulation. In doing so, pervious concrete has the potential to lower overall project costs thus making it more economical.

 

1.1.   Benefits of pervious concrete

 

 

a)     Environmental benefits

 

·    Helps in saving precious water which otherwise goes to drains.

·    Helps in keeping earth below wetter, greener and cooler.

·    Recharging ground water level.

·    Replace costly water harvesting systems.

·    Eliminates use of asphalt which normally causes environmental pollution.

·    Use of fly ash thus reducing pollution.

 

b)     Other benefits

·    Eliminates the need of costly water drainage systems.

·    Rough texture thus avoiding skidding of vehicles.

·    Low maintenance cost.

·    Stronger and durable for light traffic loads.

·    Use of local building material.

·    Lower cost compare to other pavement solution.

·    Conventional construction practices.

·    Use local semi skilled mason or labor.

 

 

 

2.      BUILDING MATERIALS FOR PERVIOUS CONCRETE:

The basic advantage with this type of concrete is the use of locally available building material like course aggregate, fine aggregate, cement, chemical admixtures etc. Details of building materials used are as tabulated below refer table 1,2 and 3.

 

Table 1. 20 mm aggregates properties: Crushing value 20%, specific gravity 2.75 (other parameters confirming to IS 383 - 1970)

 

IS Sieve Size

Cumulative % Retained

Cumulative % Passing

20

1

99

16.0

55.85

44.15

12.5

98.25

1.75

10

100

0

6.3

0

0

 

Table 2. Sand properties (specific gravity 2.52 and other parameters confirming to IS 383 - 1970)

In many countries it is also termed as no fines concrete but looking to possibilities of aggregate failure we have used   fine aggregate, 5% of Coarse Aggregate quantity. With 5% fine we have conducted 5 trials but got less strength compared to 0% Fines

 

Sieve Analysis of Fine Aggregate:-

IS Sieve Size

Cumulative % Retained

Cumulative % Passing

4.75

11.5

88.5

2.36

30.5

69.5

1.18

56

44

600 mcr

82.4

17.6

300 mcr

95.9

4.1

150 mcr

99

1

Pan

100

0

 

2.1 MIX DESIGN

We have conducted Mix Design as per Ambuja Method.

 

Table 4. Mix Proportions

A/C ratio – 4.0

W/C ratio – 0.44

 

Material

Quantity per CUM (Kg)

Ratios

Cement

384

A/C  -  4.0

Coarse Aggregate

1459

W/C  - 0.44

Fine Aggregate

77

(5%)

Water

169 lits

 

Plasticizer

  1%

Sikkacem

 

 

2.2 Test Results:

 

Following strength results were obtained. Total 14 trials (Including 5 tests of 5% fines) were conducted at Nashik concrete laboratory. Cubes were cured in gunny bags and not in curing tanks so as to create exact site conditions.

As such there is no Code available for Pervious Concrete. As per ASTM C 1688, Slump & air Content test are not applicable to pervious Concrete. Fresh dencity has been measured & comes to 2120 Kg/ Cum. (Avg. wt of Cube is 7.15 kg)

As per ACI 522 R -06, Drainage rate of Conc. Pavement will vary from 2 to 18 gallons / min/sqft. In our case it comes to 4.5 to 6.0 gallons/min./sqft

 

Table 2.1.1. Compressive Strength with 5% fines

 

Age (Days)

Wt. of Cubes (Kg)

Strength (Kg/cm2)

3

7.95

151.2

7

8.0

174.0

28

8.0

234.0

 

 

Table 2.1.2. Compressive Strength with no fines

 

Age (Days)

Wt. of Cubes (Kg)

Strength (Kg/cm2)

3

8.10

155.5

7

8.05

210.6

28

8.15

308.2

 

 

Table 2.1.3   Flexural Strength with no fine aggregate

 

Material Used

Result

Pervious Concrete Without Chicken Mesh

3.52 KN

Pervious Concrete with Wire Mesh

3.80 KN

Pervious Concrete with Chain Link

5.00 KN

 

There are chances that porosity of this pavement may get blocked by the passage of time. If it happens same may be cleaned by pressure water jet. It is not recommended for heavy traffic loads.

 

Photographs:

 

Porosity   

 

              

 

 

Wire Mesh

 

    

 

 

With Wire Mesh   

 

                       

 

 

With Chain Link

 

        

 

 

Actual Slab

                                                 

 

 

Flexural Strength Check

 

 

 

3.0   Cost comparison:

 

Type of Pavement

Rate* (Rs./Sqft)

Perviousness

Remarks

Kota Stone

100

Impervious

Drainage Required

Shahbadi Stone

110

Impervious

Drainage Required

Kaddapa Stone

120

Impervious

Drainage Required

Ferro Concrete Block

125

Impervious

Drainage Required

Normal Concrete

80

Impervious

Drainage Required

Pervious Concrete

75

Pervious

Drainage not Required

 

* As per prevailing market rates as in April, 2012 in Nashik, Maharashta.

The above table indicates that pervious concrete is not only eco-friendly but also pocket-friendly.

Pervious concrete pavement is very economical compare to other pavements.

 

 

CONCLUSION

Pervious concrete is one of finest solution towards water logging problems especially at parking and walk ways. It also helps in saving precious water. Though the use of such concrete is at very preliminary stage but is expected to increase in future looking to enormous advantages.

We used chicken mesh for achieving the tensile strength but after results we conclude that, tensile strength was better with Chain link instead of chicken mesh.

Future Scope:- Maximum tensile strength might be achieved by minimizing the spacing between the mesh we have used.

Pervious concrete “what a concrete step towards a green earth”…….

 

 

References:-

· Benefits of Pervious Concrete, Source: www.tadaysconcretetechnology.com

· Pervious Concrete Wikipedia

· Pervious Concrete by ACI Report No. 522 R 06

· Pervious Concrete by National Readymix Concrete Association (NRMCA)

· Optimizing The Strength And Permeability Of Pervious Concrete Ryerson University Department Of Civil Engineering Amanda Lidia Alaica.

· NDMVP final Year Students project on “Improving Strength of porous Concrete” by Mr. Akshay Mahale, Mr. Chetan Misal, Mr. Yogesh Shejwal & Mr. Vivek Sonje.