Weathering course: An aggregate mixture which is made with waste building materials which can create a protection field, thermal insulation, good cooling effect and also allows weather-related moisture to easily pass through and away from the building.
TYPES OF WEATHERING COURSE BASED ON MATERIALS USED:
1 . Extruded Polysterene Insulation Weathering Course Treatment.
Brick Bat Coba Weathering Course Treatment.
Brick Bat Coba Weathering Course Treatment.
* PCC with Brick Bats Lime Concrete With Brick Bats
3 . Brick Jelly Weathering Course System.
4 . Weathering Tiles.
Extruded And Expanded Polystyrene Insulation:
(EPS) foam is a closed-cell insulation that’s manufactured by “expanding” a polystyrene polymer; the appearance is typically a white foam plastic insulation material (the likes of which can be found as merchandise packaging).
(XPS) foam is a rigid insulation that’s also formed with polystyrene polymer, but manufactured using an extrusion process, and is often manufactured with a distinctive color to identify product brand.
Pros and Cons of EPS and XPS
· Recyclable products that assist with LEED points.
· Won’t support mold or mildew growth.
· Long-term, stable R-value.
· Can be placed below grade.
· Can be utilized for inverted assemblies (over membrane).
· Exposure to sun will deteriorate the product.
· Solvents/solvent-based materials cause irreversible damage.
· Elevated temperatures (above 250 degrees F.) will “melt” polystyrene.
· Incompatible with certain thermoplastics, polystyrene insulations are known to draw plasticizers out of thermoplastic membranes, causing permanent degradation.
· Polystyrene is flammable, requiring proper placement in any assembly.
BRICK BAT COBA
The brick bat coba is used particularly for waterproofing of flat roofs, primarily RCC with some thermal insulation (mud phuska) in the coastal region.
· Provides thermal insulation.
· Assists in smooth and easy flow of rainwater.
· Helps in protecting and maintaining structures against corrosion.
· Locally available materials can be used.
Drawbacks Of Brick Bat Coba
BBC’s thickness is maintained at 125mm to 150 mm, which accumulate unnecessary weight on terrace. A thick surface is neither a solution of waterproofing nor of heat insulation. On the contrary, if water seeps through BBC, this thick surface works as a water reservoir and does not allow water to evaporate easily.
Impossible to repair:
If water travels below BBC, it exits wherever it finds a path and we cannot anticipate the source cracks on BBC that need to be repaired. Normally in such cases, we do patch work which hardly provides any solutions.
Removing BBC from entire terrace is time consuming and requires lot of labor efforts. Some part of BBC fixed with mother surface so well that if we make an attempt to dismantle it, surface gets damaged.
Rigidness in BBC surface:
Generally, cracks appear in BBC due to climatic variations. Building surfaces that are exposed to temperature variations require flexibility. Even if, we do patch work or grouting in cracks, it may prevent leakages for a while but reappears after few months.
In areas where external factors such as climate variations and heavy rainfall are not exist, BBC can provide satisfactory work but only if it is applied properly. In these days, there is lack of skilled manpower and poor supervision further increases possibility of poor applications which leads to a failure. Even the basis requirements such as leveling, grouting etc. are not maintained properly.
Lime Concrete with Brick Bats:
A concrete made from a mixture of lime, sand, and gravel is said to be as lime concrete. It was widely used before the lime was replaced by Portland cement.
Properties of lime concrete
· Lime concrete provides good bases to bear the sufficient loads and also provide certain degree of flexibility.
· It adjusts very well when it is in contact with surface.
· Lime concrete also exhibits certain degree of water proofing property and thus prevents subsoil dampness in floors and walls.
· Lime concrete also exhibits volumetric stability.
· It can be made easily and can be available at much cheaper rates.
· It also resists weathering effects and is very durable.
· Lime Allows Buildings To Breathe.
· Lime Contributes To A Healthy Environment.
· Self Healing properties.
Drawbacks of Lime concrete
1. Hydraulic lime usually gains strength in time greater than the time in which cement concrete gains same value of strength.
2. Lime concrete takes a long time to cure, and while the ancient world had lots of time, today time is money.
3. Lime concrete does not harden in water but stays soft. So there are situations where it cannot be used.
4. More labour may be needed.
5. Future projects may be more costly.
PCC with Brick Bats:
The intimate mixture of cement, sand, course aggregate (jelly) and water is known as plain cement concrete. Small quantities of admixtures like air entraining agents, water proofing agents, and workability agents may also be added to impart special properties to the plain cement concrete. In cement concrete no reinforcement is provided.
· Strong in tension as well as compression.
· Resistant to erosion and abrasion.
· They can be made of any desired strength.
· Easily molded.
1. The tensile strength of plain cement concrete is about one-tenth of its compressive strength.
2. The main steps of using plain cement concrete are mixing, casting, and curing. All of this affects the final strength.
3. The cost of the forms used for casting PCC is relatively higher.
4. For multi-storied building the RCC column section for is larger than steel section as the compressive strength is lower in the case of RCC.
5. Shrinkage causes crack development and strength loss.
Brick Jelly Weathering Course System.
· Cost effective
· Resource efficient
· Locally available
· Heat transferred delayed not stopped.
· Absorbs heat all day and radiates throughout the night.
· Bricks are porous; it absorbs all water and acts as a reservoir above roof slab.
· Just contains a few waterproofing protection properties, no specific waterproofing material applied.
· Increases AC usage.
· Without periodic maintenance, the entire roof slab is at risk.
· Cumbersome, Time consuming and not consistent
· Extreme temperature differences between indoor / outdoor causes thermal stress.
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