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Making Green Porous Concrete for Rain Water Harvesting and Urban Pavements


Published on Feb 27, 2019

Abstract

Due to urbanization and improper drainage, flooding is a common phenomenon. The pavements and courtyards are presently covered with impervious concrete cement blocks which will not allow rain and drain water to percolate and reach groundwater table. Most of the cities get flooded even with little rainfall due to poor infiltration and drainage. Moreover, these concrete surfaces emit thermal radiation and create heat islands and enhance the global climatic temperature. If paving material is of pervious nature, it will enhance rain water harvesting and will recharge groundwater aquifers below urban areas. But all the available paving materials are impervious and heat emitting in nature, which creates health hazards too. In order to solve this problem, a cost effective, pervious concrete pavement block with a green cover on the top can be made from locally available materials. The more void space in this pavement blocks will allow water to percolate freely downwards and allow grass to be cultured and grown on top of this pavement block other than green aesthetic look and cool eco-friendly environment.

Keywords : Pavement blocks, green porous concrete, urban pavements, infiltration, drainage, rain water harvesting, groundwater recharge, eco-friendly concrete.

Objectives:

1. To evaluate the aggregate suitability for preparing a porous pavement block based on their size gradation, compatibility, angularity and toughness index.

2. To evolve optimum size of coarse aggregate for maximum effective porosity and permeability.

3. To determine the strength characteristics such as tensile splitting strength, compressive strength and abrasion resistance to evaluate the suitability of porous concrete for pavement blocks.

4. To determine the porosity and permeability of the standard 15cm X 15cm X 7.5cm porous concrete in order to understand its effectiveness in groundwater infiltration and rain water harvesting.

5. To study the effect of grass turf laid porous concrete pavement blocks in its permeability characteristics.

Methodology

 Different types of coarse aggregates viz: river side pebbles and crushed granite stones were analysed for their size gradation, angularity, surface roughness, impact factor etc., to understand the best suitable material for coarse aggregate.

 Different mix designs have been carried out and optimum water: cement: aggregate ratio identified.

 Different grade size of OPC and PPC available in the market have been tested for understanding the strength characteristics in standard pavement blocks.

 Media for culturing grass seeds has been prepared and tested its effectiveness in various conditions.

 The porous concrete block specimens of standard size 15cm X 15cm X 15cm have been casted and tested for evaluating compressive strength and water absorption at 7 and 28 days as per IS 15658:2006.

 The pervious concrete pavement blocks (15cm X 15cm X 7.5cm) have been tested for porosity, permeability, tensile splitting strength, compressive strength and abrasion resistance with and without grass turf at 28 days as per IS15658:2006.

Permeability Test

Result

From the above tests and research experiments the green porous concrete blocks found to be having compressive strength of 12.67 MPa (7 days), split tensile strength of 1.87 MPa, porosity of 30-40%, permeability of 1.21cm/s and slump of 0 mm.

Conclusion:

From the cost benefit analysis, it is found that the cost of this will be half of the present pavement blocks in the market thanks to the voids created, the type of aggregates used and optimum water consumption. From these studies, it is proved that the Green Porous Concrete Pavement Block is an alternate pavement block for many open utility area/surfaces such as open courtyards around buildings and public utility areas, gardens, playgrounds, green walls, etc., It may reduce the heat islands around buildings, provide clean surfaces covering around trees, rainwater and drain water harvesting, reduce floodwater accumulation and save drainage construction, reduce power consumption, dried surface immediately after heavy rain, etc.

Scope for Future Work:

Pervious concrete is having a lot of potential and demand in the construction industry thanks to its infiltration property and reduction in temperature around due to its breathing holes present. It is similar to conventional concrete but manufactured without or minimum of fine grained aggregates. The voids present in the block in the absence of fine aggregates allow water to flow through the concrete, and drain through the sub-grade filtering surface water reducing overall storm water runoff enhancing groundwater recharge.

The need for pervious concrete has grown. It’s definitely growing and spreading but it still has a long way to go. The greatest market potential for Green Porous Concrete is parking lots, Parks, road with light traffic, pedestrian walk way, green houses, courtyards, playground, etc. It can also be used as a structural drainage fill behind retaining walls. It is the brightest star in the Green Building movement asit has green grass turf on its surface, that gives aesthetic look and on the same hand helps to reduce the power consumption.

Project Done By Mr. Ujjwan Krishna Manandhar, Mr. Shubhankar Seth, Mr. Utkarsh






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