impacts of air pollution on building material

7/28/2019 Impacts of Air Pollution on Building Material

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Impacts on materials fall into four categories;

1. Discoloration

2. Material loss3. Structural failure

4. Soiling


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Surface discoloration is the non-uniformity of

colour or hue on the surface of a single concrete

placement. There are no valuation studies or material

inventories from which estimates of the costs of

discoloration can be estimated

However, such costs are probably very small


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A material loss; acid rain is leaving its mark on

buildings, statues and other man-made structures.

Limestone and marble are particularly vulnerable

because acids attack their principal constituent, calcium

carbonate. These reactions produce water-soluble

substances that easily leach out and weaken the

structure.


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Structural failure refers to loss of the load-carrying

capacity of a component or member within a structure

or of the structure itself.

Structural failure is initiated when the material is

stressed to its strength limit, thus causing fracture or

excessive deformations.


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In a well-designed system, a localized failure

should not cause immediate or even progressive

collapse of the entire structure.

Ultimate failure strength is one of the limit

states that must be accounted for in structural

engineering and structural design.


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Soiling is an optical effect (a darkening of reflectance) and

results primarily from the deposition of airborne particulate

matter to external building surfaces

The soiling on the brick consists of a thin but tenacious layer

and follows a fairly regular pattern.


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Material Sensitivity to air

pollution

Stock-at-risk

Brick very low Very large

Mortar moderate to high very large

Concrete low very large

limestone, marble)

atural stone

(sandstone

high (severely affected by SO2) large (especiallyculturally

valuable objects)

Unalloyed steel high (severely

affected by SO2)

very small

Stainless steel very low medium


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Aluminium very low medium

Copper low low

Lead very low low

Nickel and nickel-

plated

high (especially in

SO2 polluted

environment)

very low

Zinc and galvanised

steel

high (especially in

SO2 polluted

environment)

medium


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Acid Rain Since the beginning of the Industrial Revolution soiling and

degradation of buildings in urban areas has been noticeable.

The cause of this has often been attributed to the effects of air

pollution.

The pollutants that form acid rain are principally sulphur

dioxide and nitrogen oxides; both of these are released fromthe combustion of fossil fuels like coal and oil. Since the

Industrial Revolution emissions of both have increased.


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Most structures and buildings are affected by acid

deposition to some degree because few materials are

safe from these effects.

In addition to atmospheric attack structures that are

submerged in acidified waters such as foundations

and pipes can also be corroded.


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It mainly refers to loud and irritating

sound which disturbs the peaceful life.


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Industries

Traffic

Electrical generators

Construction activities

Explosions


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Damages structures by developing

cracks.

High intensity sound can break window

panels.


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These types of stones are commonly used forbuildings and monuments- include granite,

sandstone,limestone, marble and slate.

Reviews have concluded that acid deposition damage

to siliceous stones is negligible, and therefore attention

is confined here to calcareous stones, i.e. limestone,

marble and calcareous sandstones. These have been

extensively used as building materials in Europe.


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The current opinion is that brick is unaffected bysulphur dioxide attack. However, the mortar

component of brickwork is not. Mortar consists of

sand, calcium hydroxide and other carbonate phases.

The primary agent of mortar erosion is acid attack on

the calcareous cement binder


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Portland cement, the major binding agent in mostconcrete, is an alkaline material which is susceptible toacid attack. Potential impacts to concrete includesoiling/discoloration, surface erosion, spalling and

enhanced corrosion of embedded steel. However, for all these impacts (with the exception of

surface erosion) damages are more likely to occur as aresult of natural carbonation and ingress of chloride

ions, rather than interaction with pollutants such as SO2 The main factor influencing the durability of concrete

is the corrosion of embedded steel reinforcement.


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In new concrete, these bars are protected from acidcorrosion by the alkaline characteristics of the

cementitious component of the concrete.

As surface erosion does not affect structural integrity it

has no impact on concrete durability. However, in badly

prepared concrete, when carbonation has already led to

steel corrosion, cracks will develop rendering the

system more accessible to attack by SO2, as thecorrosion products of steel occupy a greater volume

than the steel.


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SHAHAARBAN.P

impacts of air pollution on building material

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