PERVIOUS CONCRETE

PERVIOUS CONCRETEANNAMACHARYA INSTITUTE OF TECHNOLOGY AND SCIENCES

PRESENTED BY G. GURU LATHA 13701A0115

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Topics To Be DiscussedWhat is pervious concreteHistoryMix designCompositionSubgrade applicationsCompaction methodsApplicationsAdvantagesDisadvantagesconclusion

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What Is Pervious ConcretePervious concrete is a special type of concrete with a high porosity used for concrete flatwork applications that allows water from precipitation and other resources to pass through it, thereby reducing the runoff from a site and recharging ground water levels.

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History Of Pervious Concrete Pervious concrete was first used in the 1800s in Europe. It became popular again in the 1920s for two story homes in Scotland and England. It became increasingly viable in Europe after the Second World War due to the Scarcity of cement. It did not become as popular in the US until the 1970s

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Mix DesignAggregatesCementious MaterialsWaterAdmixtures Ranges Of Materials Design Void Content: 15% to 30% Water to Cement Ratio: 0.28 to 0.40 Binder to Aggregate Ratio: below 0.256

A mix design with little water can create a very weak binder. This will create a very dry mix that is susceptible to spalling and crumbling.

Correct amount of water

A mix design with too much water can collapse the void space, making an almost impenetrable concrete surface

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AggregatesPervious concrete has little or no fine aggregates in the mixture. Aggregate size is typically between 3/8 to1/2 inch maximum

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Cementious materialsTypically type-I cement is used for the production of pervious concrete.Supplementary cementious materials such as fly ash or slag can be used in exchange up to about 25% (fly ash) and up to about 50%(slag) of cement.

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WaterWater meeting standard requirements for conventional concrete can be used for the production of pervious concrete

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AdmixturesAir entraining admixtures may be used to improve the freeze/thaw durability of the paste/mortar.

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Typical composition of pervious concreteThe Pervious Concrete LayerSub-grade LayerDrainage12

Sub-grade LayerThis is the undisturbed soil underneath the sub-base layer. Sub-grade layer infiltration rate determines how much water can be absorbed within a given time. This directly affects the size of the sub-base layer. If the infiltration rate is too low, larger sub-base or drainage should be considered. If the sub-grade is too fine, it may be necessary to place geo-textile in between the sub-base and sub-grade to minimize the migration of fine soil particles into the sub-base. Omitting this could lead to clogging and reduced retention capacity13

Pervious Concrete Layer

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DrainageA drainage system is not always necessary but may be needed when the infiltration rate of the sub-grade layer is low and water contained in the sub-base cannot be absorbed by soil quickly enough.

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Sub Grade ApplicationsLeveled subgradeElevated subgrade16

Leveled Subgrade Layer

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Elevated sub grade layer

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Compaction MethodsRoller compaction

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2. Compaction by plate compactors

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3. Mechanical / manual vibrating screeds

Commonly used technique, which is simple and fast.

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Keep in mind.Maintenance such as vacuuming or sweeping may be required in certain areas to preserve pervious propertiesPervious concrete is only as good as its design and installation.

vacuum for sweeping pervious pavements

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APPLICATIONS

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ADVANTAGES

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Environmental benefitsReduces storm water runoffWater management practicesMitigation surface pollutants pervious water allows recharging the ground level

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Safety

Reduce tire soundPrevents glare

EconomicsLow maintenance costMore life span26

DISADVANTAGESExtended curing timeLimited use in heavy vehicle traffic areasFrequent maintenance is requiredCompressive strength is lowSpecial care in expansive soils & high ground water conditions

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CONCLUSIONThe pervious concrete helps the water to infiltrateCities with pervious pavements would be safer for traffic, be cleaner and less pollution

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