FIRE RESISTING PROPERTIES OF COMMON BUILDING MATERIALS

Fire resisting properties of common building materials such as stone, brick, timber, cast-iron, glass, steel and concrete are mentioned below.

1. STONE

The stone is a bad conductor of heat. But it suffers appreciably under the effects of fire. The stone is also liable to disintegrate into small pieces when heated and suddenly cooled. Granite explodes and gets easily disintegrated in case of a fire. Limestone is easily crumbled even by ordinary fire. Sandstones of compact composition with fine grains can generally stand moderate fire successfully without the formation of serious cracks.

2. BRICKS

It is found that bricks are not seriously affected until very high temperature of 12000C to 13000 C are reached. This is due to the fact that a brick is a poor conductor of heat. If the type of mortar and quality of workmanship are good, brick masonry generally offers good resistance to fire. However, a brick has its own structural limitation for use in buildings.

3. TIMBER

As a general rule, structural elements made of timber ignite and get rapidly destroyed in case of fire. Further, they add to the intensity of fire. But timber used in heavy sections may attain a high degree of fire-resistance because timber is a very bad conductor of heat. This is the reason why time is required to build up sufficient heat so as to cause a flame in timber. In order to make timber more fire resistant, the surfaces of timber are sometimes coated with certain chemicals such as ammonium phosphate and sulphate, borax and boric acid, zinc chloride, etc. such a treatment on timber surfaces retards the rise of temperature during fire. The timber cam also be made fire-resistant by the application of certain paints on its surface.

4. CAST IRON

This material is rarely used as structural material at present. This material flies into pieces when heated and suddenly cooled. Hence, when this material is used in construction, it is covered either by brickwork of one brick thickness or any other fire resisting material such as concrete.

5. GLASS

This material is a poor conductor of heat and its expansion due to heat is small. Cracks are formed I this material when heated and then suddenly cooled. Reinforced glass with steel wire is ore fire-resistant than ordinary glass and it can resist sudden variation in temperature without the formation of cracks. Wired glass, even if it breaks, keeps the fractured glass in its original position.

6. STEEL

Steel is a good conductor of heat and hence, it is rapidly heated in case of fire. It is found that steel loses its tensile strength with the increase in heat and the yield stress of mild steel at 6000C is about one-third of its value at normal temperature. Hence, under intense fire, the unprotected steel beams sag, the unprotected steel columns buckle and the structure collapses. Steel completely melts at a temperature of 14000C. It is also found that if the surface paint is not specially made fire-resistant, it assists in spreading the flame on the surface and thereby it adds to the intensity of fire.

If steel plate or sheet form is fixed to framework, it becomes affective is resisting the passage of flame. Such construction is widely adopted in manufacturing fire-resisting doors and windows.

7. CONCRETE

Concrete has got very good fire resistance. The actual behaviour of concrete in case of fire depends upon the quality of cement and aggregates used. In case of reinforced concrete and prestressed concrete, it also depends upon the position of steel. Larger the concrete cover, better is the fire resistance of the member.
There is no loss in strength in concrete when it is heated up to 250°C. The reduction in strength starts if the temperature goes beyond 250°C. Normally reinforced concrete structures can resist fire for about one hour at a temperature of 1000°C. Hence cement concrete is ideally used fire resistant material.

HOW TO SELECT DOORS & WINDOWS FOR HOUSE? (4 FACTORS TO CONSIDER)

Doors and windows are the important part of a house. Right type of doors and windows for house would greatly enhance its overall look and appearance. There are many verities of door and windows available in market. So the process of selection of appropriate doors and windows for house is quite difficult.

There are several factors to be considered before finalizing the option for their adoption.

Selection of Door and Window

FACTOR FOR CONSIDERATION

There are many factors which influence the type of doors/windows to be selected for the house. Out of which the 4 important factors are as follow:

• Climatic Condition
• Function and Location
• Type of Material
• Architectural Design

1. CLIMATIC CONDITION

• In areas closer to the sea it would be advisable to use a material which is not affected by corrosion and accordingly steel frames and shutters would not be a good option.
• In extreme climatic condition (either hot or cold) the sizes of the doors and windows should be such that there is least effect of the external environment to that within the house.
• In moderate climatic condition the extent of sunlight coming into the house has to be considered and accordingly the area for glazing has to be decided.

2. FUNCTION AND LOCATION

• Doors should be picked at according to the function they are expected to perform. For example. Front door and back door may have two totally different sets of requirements, and they are different from interior doors.
• Exterior doors should always be of a sturdy material and should have secure fastening.
• Interior doors, on the other hand, should be light enough for all family members to handle easily.

3. TYPE OF MATERIAL

• Careful consideration has to be given to the type of material to be used.
• Good materials include heavy wood, steel, glass or fiberglass construction, which will serve well for many years.

4. ARCHITECTURAL DESIGN

• The final step would be to choose the design including colour scheme of door/window, the liking and taste of which varies from individual to individual.

WHAT ARE THE BASIC PROPERTIES OF HEAT INSULATING MATERIALS?

THE BASIC PROPERTIES OF HEAT-INSULATING MATERIAL

In architecture, the material which prevents the outflow of indoor heat is normally called adiabator. On the other hand, the material which prevents the inflow of outdoor heat is called heat insulator. These two are collectively called heat-insulating materials.

This kind of material is mainly used for walls, ceilings, thermal equipment and thermal pipelines. It is sometimes used to preserve heat in winter construction. Generally, it may also be used a lot for refrigerating chamber and equipment.

It is known that heat current flows from high temperature to low temperature. In order to keep the room warm in winter, constant indoor heat supply must be provided to compensate for the heat loss due to the temperature difference. This problem can be partly addressed by using the heat-insulating material. For example, a six-storey residential building of four units in Beijing, China, uses the frame structure of mineral cotton composite plate, and this reduces the heat loss by 40% compared with masonry-concrete structure.

According to the statistics, a good insulation building can cut down the fuel consumption by 25% to 50%. And to achieve this, one should consider the following questions:

• What kind of structure is easy to lose heat, and vice versa;
• How the composition of the material relates to its heat-insulating property;
• What are the factors that influence the material’s heat-insulating property, and
• How to select the proper material.

Exterior protected construction is made of different building materials, the thermal conductivity and specific heat of which are the important parameters to the designation of the wall, roof, floor, and to the heat engineering calculation. The material with low thermal conductivity and high specific heat can improve the heat-insulating property of the exterior protected construction and keep the indoor temperature stable.

The basic requirement for selecting heat-insulating material is that the thermal conductivity is well below 0.23 W/ (m*K), the apparent density below 600kg/m3, and the compression strength above 0.3MPa. Moreover, the material’s hygroscopicity, temperature stability, and corrosion resistance all need taking into account according to the characteristics of the project.

The following is an introduction of the basic properties of the heat-insulating material.

1. THERMAL CONDUCTIVITY

Thermal conductivity is the measurement of the heat transfer ability of the material itself. It is influenced by the material constitution, porosity, temperature of the surroundings, and the direction of the heat current.

THE MATERIAL CONSTITUTION

The thermal conductivity can be influenced by the material’s chemical composition and molecular structure. Material with simple chemical composition and molecular structure has higher thermal conductivity than the complex.

POROSITY

The thermal conductivity of solid matter is higher than that of air. Therefore, the higher the porosity is, the lower the thermal conductivity will be. In this aspect, not only the porosity matters, but also the size, distribution, shape, and connectivity of the pores.

HUMIDITY

Materials in damp conditions have higher thermal conductivity. What should be noted is that if water is frozen, its thermal conductivity will become higher. This is because the thermal conductivity of water is 20 times higher than that of air while that of ice is 80 times higher than air. Therefore, special attention should be taken to guard the heat insulating material against damp.

TEMPERATURE

If the temperature becomes higher, the thermal conductivity increases accordingly. As the temperature rises, the thermal motion of the molecular solids becomes more active; the heat conduction of the air in the pore gets boosted, and the radiation effect of the pore wall is strengthened.

THE DIRECTION OF HEAT CURRENT

In case of the material being anisotropic (like the fibrous material wood), when the heat current flows parallel to the fibers, there will be no strong resistance; However, when the heat current flows against the fibers, strong resistance will be incurred.

2. TEMPERATURE STABILITY

Temperature stability is the ability of the material to retain its original property when exposed to heat. It is generally expressed by the ultimate temperature, exceeding the point of which the material will lose its heat-insulating function.

3. STRENGTH

The heat insulating material is usually measured by its compression strength and flexural strength. As the material is highly porous, its strength is weak. Thus it is better not to allow the heat insulating material to carry more weight.

Source:- civilblog.org