Defects of Bricks

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Defects of Bricks:
•Over-burning – Burnt beyond complete vitrification
•Under-burning – Burnt less not to cause complete vitrification
•Bloating – Spongy swollen mass over the surface due to excess carbonaceous matter and sulphur
•Black Core – Due to bituminous matter or carbon
•Efflorescence – Grey of white crystallization of alkalis on the surface, due to water absorption
•Chuffs – Deformation due to rainwater falling or hot bricks
•Checks or Cracks – Due to lumps of lime getting in contact with water
•Spots – Dark sulphur spots due to iron sulphides
•Blisters – Broken blisters due to air entrapped during molding
•Laminations – Thin lamina produced due to air entrapped in voids of clay

Types of Brick Bonds

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Types of Brick Bonds:

In brick masonry, there are many techniques to stack bricks. These different arrangements are known as bricks bonds. Each bond has its own characteristics. Following are the commonly used bricks bonds.
1.Stretcher Bond
2.English Bond
3.Flemish Bond
4.Common/American/English Garden Wall Bond
5.Flemish Garden Wall Bond
6.Herringbone Bond

1. Stretcher Bond
•Easiest bond to lay & it minimizes the amount of cutting required.
•Originally used for single brick walls.
•It is used for cavity walls as less cutting is required.
•Walls are half brick wide.
•No two adjacent vertical joints should be in line.

2. English Bond
•Alternative courses of headers and stretchers.
•One header placed centrally above each stretcher.
•This is a very strong bond when the wall is 1 brick thick (or more thicker).
•One of the strongest brickwork patterns.

3. Flemish Bond
•Alternate bricks are placed as header and stretcher in every course.
•Each header is placed centrally between the stretcher immediately above and below. This is not as strong as the English bond at 1 brick thick .
•It can be successfully applied in cavity wall.

4. Common/American/English Garden Wall Bond
•A pattern made like Stretcher bond but with a row of headers replacing every nth course (n is usually odd).

5. Flemish Garden Wall Bond
•In this variant of Flemish bond, one header is placed at every third stretcher.

6. Herringbone Bond
•It is a purely decorative bond. It is used in floor and wall panels.

TYPES OF PORTLAND CEMENT

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PORTLAND CEMENT

TYPES OF PORTLAND CEMENT

  1. Ordinary Portland Cement (Type I)
  2. Modified Portland Cement
  3. Rapid Hardening or High Early Strength Portland Cement (Type III)
  4. Quick Setting Cement
  5. Low Heat Portland Cement (Type IV)
  6. Sulphate Resistant Portland Cement (Type V)
  7. Water Repellent Portland Cement
  8. Water Proof Portland Cement
  9. High Alumina Cement
  10. Portland Slag Cement
  11. Air Entraining Portland Cement (Type I-A, II-A, III-A)
  12. Pozzolana Portland Cement
1. Ordinary Portland Cement

It is used in general construction works. All other varieties of Cement are derived from this Cement.

  • White Cement
    • OPC with pure white color produced with white chalk or clay free from iron oxide.
    • Instead of coal, oil fuel is used for burning.
    • Much more costlier than OPC.
  • Colored Cement
    • Suitable pigments used to impart desired color.
    • Pigments used should be chemically inert and durable under light, sun or weather.
 2. Modified Portland Cement
  • This cement on setting develops less heat of generation than OPC.
  • It is best suited in hot climate for civil works construction.
3. Rapid Hardening or High Early Strength Cement (Type III)
  • Gains strength faster than OPC. In 3 days develops 7 days strength of OPC with same water cement ratio.
    • After 24 hours – not less than 160 kg/cm2
    • After 72 hours – not less than 275 kg/cm2
    • Initial and final setting times are same as OPC.
    • Contains more tri-calcium silicate (C3S) and finely ground.
    • Emits more heat during setting, therefore unsuitable for mass concreting.
    • Lighter and costlier than OPC. Short curing period makes it economical.
    • Used for structures where immediate loading is required e.g. repair works.
4. Quick Setting Cement
  • Sets faster than OPC.
  • Initial setting time is 5 minutes.
  • Final setting time is 30 minutes.
  • Used for concreting underwater and in running water.
  • Mixing and placing has to be faster to avoid initial setting prior to laying.
5. Low Heat Cement
  • Low percentage (5%) of tri-calcium aluminates (C3A) and silicate (C3S) and high (46%) of di-calcium silicate (C2S) to keep heat generation low.
  • It has low lime content and less compressive strength.
  • Initial and final setting times nearly same as OPC.
  • Very slow rate of developing strength.
  • Not suitable for ordinary structures.
    • Shuttering required for long duration so cost will increase.
    • Prolonged curing is required.
    • Structure utilization will be delayed.
6. Sulphate Resistant Portland Cement
  • Percentage of tri-calcium Aluminate (C3A) is kept below 5% resulting in increase in resisting power against sulphates.
  • Heat developed is almost same as Low Heat Cement.
  • Theoretically ideal cement. Costly manufacturing because of stringent composition requirements.
  • Used for structures likely to be damaged by severe alkaline conditions like bridges, culverts, canal lining, siphons, etc.
7. Water Repellent Portland Cement
  • It contains a small percentage of water-proofing material with the cement and is manufactured under the name “Aqua-crete”.
  • The cement is prepared with ordinary or rapid hardening cement and white cement.
  • It is used in to check moisture penetration in basements etc.
8. Water Proof Portland cement
  • It is prepared by mixing ordinary or rapid hardening cement and some percentage of some metal stearate ( Ca, Al etc).
  • It is resistant to water and oil penetration.
  • It is also resistant to acids, alkaline and salt discharged by industrial water.
  • It is used for water retaining structure like tanks, reservoir, retaining walls, pool, dam etc
9. High Alumina Cement
  • Black chocolate color cement produced by fusing bauxite and limestone in correct proportion, at high temperature.
  • Resists attack of chemicals, Sulphates, seawater, frost action and also fire. Useful in chemical plants and furnaces.
  • Ultimate strength is much higher than OPC.
  • Initial setting time is 2 hours, followed soon by final setting.
  • Most of the heat is emitted in first 10 hrs. Good for freezing temperatures in cold regions (below 18°C).
  • Develops strength rapidly, useful during wartime emergency.
  • Unsuitable for mass concrete as it emits large heat on setting

10. Portland Slag Cement

  • Produced by mixing Portland cement clinker, gypsum and granulated blast furnace slag.
  • Cheaper than OPC, blackish grey in color.
  • Lesser heat of hydration. Initial setting in 1 hr and final setting 10 hrs.
  • Better resistance to soil agents, sulphates of alkali metals, alumina, iron and acidic waters.
  • Suitable for marine works, mass concreting.
  • Due to low early strength, not suitable for RCC.
11. Air Entraining Cement
  • OPC with small quantity of air entraining materials (resins, oils, fats, fatty acids) ground together.
  • Air is entrained in the form of tiny air bubbles during chemical reaction.
  • Concrete is more plastic, more workable, more resistant to freezing.
  • Strength of concrete reduces to some degree.
  • Quantity of air entrained should not be more than 5% to prevent excess strength loss.
12. Portland Pozzolana Cement
  • OPC clinker and Pozzolana (Calcined Clay, Surkhi and Fly ash) ground together.
  • Properties same as OPC.
  • Produces less heat of hydration and offers great resistance to attacks of Sulphates and acidic waters.
  • Used in marine works and mass concreting.
  • Ultimate strength is more than OPC but setting timings are same as OPC.

Kitchen makeovers

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Having a keen eye for detail and visualizing the usage pattern can make any kitchen very comfortable to use.

Kitchen makeovers

Providing ample space for kitchen appliances assumes importance while planning an uncluttered cooking space. Courtesy: Image Home Design

A large part of a housewife’s time is spent in the kitchen. So shouldn’t the kitchen design be ideal, making it comfortable for the lady of the house?
Having a keen eye for detail and visualising the usage pattern can make any kitchen, be it small or large, very comfortable to use. For example, planning a place for the mixie or sandwich toaster close to an electrical socket makes a very big difference as you don’t have to carry them around to where the socket is. As these small appliances do not take up too much space, they can be placed on a small raised counter.
Usually, there is no special place assigned for a heavy appliance like a wet grinder. Providing lowered counter slabs and special power points may help a lot. With the increasing number of kitchen appliances being used these days such as dishwashers, water purifiers and microwave ovens, providing ample space for them assumes importance while planning the kitchen. Small details like providing space to keep the cookery books definitely add life to the kitchen space.
Usually, the person cooking stands in front of the stove staring at a blank, dull wall. Would it not be much better to rather see some open space as you cook? A large opening in front of the cooking range with a high sill would be nice. Having just as many openings as possible, would create a brighter kitchen with better ventilation, allowing the cooking odours to escape easily.
Some of us may like to have breakfast right in the kitchen, so, providing a small opening and a counter arrangement could give the kitchen space a lot more meaning. This counter could also serve as a pantry at other times when you have guests over for lunch or dinner, and helps in reducing the clutter and congestion on the dining table. Food can be served and removed in the order perceived.
Additional area like a small utility or a service balcony, do make a big difference. You could put your washing machine there or gather vessels for washing. There could also be a small foldable ironing board for some quick ironing work in an emergency. This makes the space multi utilitarian serving yet compact.
Also not many kitchens have electric chimneys or hoods, so the wall along the cooking range gets really tarred and soiled in the long run. We could look at having darker colour wall tiles and the material or finish on the walls could ideally be easily washable and smooth. Even the counters and flooring could be of a natural hard material to prevent stains from cooking. Materials like the black granite, the kotah and cuddapah might be just right for a kitchen space.
Everything apart, the television soaps and serials seem to be part of our daily life. So we could give provision for a television set or may be a small openable shutter that could be opened up to see the television in the living area. This serves to open up the kitchen space, making it larger and more flexible, enriching the life of one and all in the house.

Steps that matter

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To facilitate an easy movement from one level to another, the location of staircases should be carefully considered, especially in vertical buildings.

ImageA good design and comfortable ergonomics of staircase is mandatory

STAIRCASES OCCUPY an important position in the design of a structure. Especially in small plots with buildings designed vertically, easy movement from one level to another depends on the location of staircases. So a good design and comfortable ergonomics of staircase is mandatory. Let us take a look at what would be an ideal location for stairways, the various types and the materials to be used.

The inner part of the house, which shall not be seen or accessed by visitors from the verandah or the front living areas, is one ideal location. To give a fancy impression, sometimes the staircases are provided in the living room. This arrangement lacks privacy and does not provide security. Ideally, the staircase could be in the dining room or in the family room depending on its central location.

The types of staircase can be classified according to usage and form — a main staircase, a service staircase and a fire escape staircase. A main staircase would be the primary one, to be centrally located and used by the residents. Service staircases can be located outside the house. They could be used by the service staff and housekeepers for terrace access and other services. Fire escape staircases are more important in multi-storey buildings. These are made mostly of steel or fire retardant materials.

In the olden days, staircases were made with mud and straw. Over the years, the craftsmanship and engineering have evolved remarkably. So has the structural system. From the simple waist slab type to the folded plate, to the free-standing type, staircase structures have really come of age. A circular folded plate type staircase in concrete cast in plywood would cost about Rs. 30,000 per flight. A similar staircase with RCC slab and a brick step would cost Rs. 10,000 per flight.

For ergonomics and safety reasons, the staircase tread has to be 10″ wide and the risers 5.5″ to 6″ high. There has to be sufficient mid-landings for a pause between two flights.

To match the architectural style and interior ambience, staircase can have a similar material and colour scheme. Wood has been the preferred material as it gives warmth to the space and lends itself to work and style. The finishes can be varnish, enamel, wax, and so on. Hard woods such as teak and oak, and exotic woods have a longer life but need to be constantly maintained in case of heavy usage.

Handrails made of wood can be very expensive, whereas a hollow circular metal handrail along with wooden balusters might be a good solution as well. Contemporary materials such as glass and metal are being increasingly used for both staircases and handrails as the primary material or a cladding material.

Lighting in staircases has to be considered in depth as it is crucial for safety. It is best to opt for lighting that remains constant from one end of the staircase to the other. Skylight over the top of the staircase can be a good solution, as the sunlight will illuminate the whole staircase to an equal degree.