Jun 24 2014

Foundation Walls and Basements

Basements are quite common in many parts of the country and almost unheard of in others. Where the frost line is relatively shallow and the footings are therefore close to the finish grade, only a short foundation wall (or stem wall as they are sometimes called) is needed to bring the construction above ground to provide support for the building frame. In cold climates where footings are required to be set deep in the ground to avoid frost heave, foundation walls may have to be several feet tall to reach above grade. With a little additional excavation, the footings can be set deeper and the foundation wall height extended sufficiently to accommodate construction of a habitable basement that is fully or partially below grade. The taller the foundation wall required by footing depth, the less additional work required to enclose a basement space.

Jan 20 2014

Concrete Finishing

The tops of concrete slabs, driveways, patios, and sidewalks must be leveled and finished to apply an appropriate surface texture. Surface finishes may be simple and utilitarian or more elaborate and decorative.

Floating, Troweling, and Brooming

The tops of footings and walls are left unfinished after the concrete has been vibrated, but flat concrete elements such as slabs, driveways, sidewalks, and patios must be leveled on top and an appropriate finish applied.

Special Finishes

An exposed aggregate finish will add color and texture to a driveway, sidewalk or patio, as well as a non slip finish. The concrete should be poured in small, manageable areas so that the aggregate can be seeded into the surface before the concrete becomes too hard. The seeding method of creating an exposed aggregate finish takes about three times longer than normal finishing so it is usually done in smaller sections.

Jan 7 2014

Characteristics of good brick

The essential requirements for building bricks are sufficient strength in crushing, regularity in size, a proper suction rate, and a pleasing appearance when exposed to view.

Size and Shape: The bricks should have uniform size and plane, rectangular surfaces with parallel sides and sharp straight edges.

Color: The brick should have a uniform deep red or cherry color as indicative of uniformity in chemical composition and thoroughness in the burning of the brick.

Texture and Compactness: The surfaces should not be too smooth to cause slipping of mortar. The brick should have pre compact and uniform texture. A fractured surface should not show fissures, holes grits or lumps of lime.

Hardness and Soundness: The brick should be so hard that when scratched by a finger nail no impression is made. When two bricks are struck together, a metallic sound should be produced.

Crushing Strength: should not be less than 10 N/mm2

Brick Earth: should be free from stones, crushed stone, sand, organic matter, saltpetre, etc.

Jan 2 2014

Planning Suitable Building Orientation

Orientation means setting out the plan of the building with respect to north-south and east-west directions to provide an opportunity to user to enjoy sun-shine and breeze when required and to avoid the same whenever not required. This is also known as planning the aspect of a building. Aspect means arrangement of doors, windows in the external wall to make good use of nature. This term has nothing to do with the architectural aspect of outlook of building. Kitchen should have eastern aspect to enjoy morning sunshine, means, kitchen should be located on the eastern side of the building to make use of morning sun rays.

Dec 31 2013

Characteristics of Concrete

1- Strength and Durability

Used in the majority of buildings, bridges, tunnels and dams for its strength
Gains strength over time
Not weakened by moisture, mould or pests
Concrete structures can withstand natural disasters such as earthquakes and hurricanes
Roman buildings over 1,500 years old such as the Coliseum are living examples of the strength and durability of concrete

2- Versatility

Concrete is used in buildings, bridges, dams, tunnels, sewerage systems pavements, runways and even roads

3- Low maintenance

Concrete, being inert, compact and non-porous, does not attract mould or lose its key properties over time

4- Affordability

Compared to other comparable building materials e.g. steel, concrete is less costly to produce and remains extremely affordable

5- Fire-resistance

Being naturally fire-resistant concrete forms a highly effective barrier to fire spread

6- Relatively low emissions of CO2

CO2 emissions from concrete and cement production are relatively small compared to other building materials.
80% of a buildings CO2 emissions are generated not by the production of the materials used in its construction, but in the electric utilities of the building over its life-cycle (e.g. lighting, heating, air-conditioning)

7- Energy efficiency in production

Producing concrete uses less energy than producing other comparable building materials.
A study quoted by the NRMCA concluded that the energy required to produce one ton of concrete was 1.4 GJ/t compared to 30 GJ/t for steel and 2GJ/t for wood

8- Excellent thermal mass

Concrete walls and floors slow the passage of heat moving through, reducing temperature swings
This reduces energy needs from heating or air-conditioning, offering year-round energy savings over the life-time of the building
One study quoted by the NRMCA found that concrete walls reduce energy requirements for a typical home by more than 17%

9- Locally produced and used

The relative expense of land transport usually limits cement and concrete sales to within 300km of a plant site.
Very little cement and concrete is traded and transported internationally
This saves significantly on transport emissions of CO2 that would otherwise occur

10- Albedo effect

The high “albedo” (reflective qualities) of concrete used in pavements and building walls means more light is reflected and less heat is absorbed, resulting in cooler temperatures
This reduces the “urban heat island” effect prevalent in cities today, and hence reduces energy use for e.g. air-conditioning

Dec 4 2013

Building Foundation

The foundation is the most critical part of any structure and most of the failure is probably due to faulty foundations rather than any other cause. The purpose of foundation is to transmit the anticipated loads safety to the soil.

Basic requirements:

To distribute the total load coming on the structure over a large bearing area so as to prevent it from any movement.
To load the bearing surface or area at a uniform rate so as to prevent any unequal or relative settlement.
To prevent the lateral movement of the structure.
To secure a level or firm natural bed, upon which to lay the courses of masonry and also support the structure.
To increase the suitability of the structure as a whole, so as to prevent it from overturning or sliding against such as wind, rain, frost etc.

Nov 28 2013

Curing of concrete

Curing of concrete is one of the essential requirement of process of concreting. Curing is process of keep the set concrete damp for some days in order to enable the concrete gain more strength.

Purposes:

Curing protects concrete surfaces from sun and wind
Presence of water is essential to cause the chemical action which a companies the setting of concrete

Nov 26 2013

Preparation of concrete mix

There are two types of concrete mixing

(i)Hand mixing

(ii)Machine mixing

Hand Mixing: This method of mixing concrete is resorted to when the quantity if concrete to be used in a work is insufficient to warrant the necessity of machine. This is used with advantage in places where machinery cannot be used on account of their non-availability or in works near a hospital where the noise of machine is not desirable. Hand mixing is done on a clean, hard and impermeable surface. Cement and sand are first mixed dry with the help of shovels until the mixture attains uniform color. Aggregative are then added to this mixture and the whole mixture is then turned by shovels until the stone pieces uniformly spread throughout. After this, desired are quantity of water is poured into the heap from a can fitted with a rose. The mass is then turned until a workable mixture is obtained. It is advised to add 10% extra cement to guard against the possibility of inadequate mixing by this method.

Machine Mixing: The machine used for mixing concrete is termed as concrete mixer. Two types of concrete mixers are in common are

1. Continuous mixers

2.Batch mixers

Continuous mixers are employed in massive construction where large and continuous flow of concrete is desired. The process of feeding the mixing is more or less automatic. The machine requires careful supervision so as to obtain the concrete mix of desired consistency.

In batch type of concrete mixer. The desired proportion of materials are fed into the hopper of a drum in which the materials get mixed by the series of blades or baffles inside the mixer. Batch mixers are further two types 1. Tilting drum type 2. closed drump type. In the first type, components are fed in the revolving drum in a tilted position and after sometime the concrete mix is discharged by tilting the drums in the opposite direction. In the latter type the drum remains rotating in one direction and emptied by means of hopper which tilts to receive the discharge.

While using the mixer, coarse aggregates should be fed first, sand and cement should be put afterwards. In this revolving state, the components get mixed while water is poured with the help of can. The concrete should be for atleast 2 minutes, the time being measured after all the ingredients including water have been fed into the drum.

Oct 30 2013

About Cement

Cement in its broadest term means any substance which acts as a binding agent for materials natural cement (Roman Cement) is obtained by burning and crushing the stones containing clay, carbonates of lime and some amount of carbonate of magnesia. The clay content in such stones is about 20 to 40 percent. Natural cement resembles very closely eminent hydraulic lime. It is not strong as artificial cement, so it has limited use in practice.

Artificial cement is obtained by burning at very high temperature a mixture of calcareous and argillaceous materials in correct proportion. Calcined product is known as clinker. A small quantity of gypsum is added to clinker and it is then pulverized into very fine powder is known as cement. Cement was invented by a mason Joseph Aspdin of leeds in England in 1824. The common variety of artificial cement is known as normal setting cement or ordinary cement or Portland cement.

Aug 31 2013

Bricks

Concrete Blocks and Bricks

Bricks are obtained by moulding clay in rectangular blocks of uniform size and then by drying and burning these blocks. As bricks are of uniform size, they can be properly arranged, light in weight and hence bricks replace stones.

Composition Manufacture Process.

Composition – Following are the constituents of good brick earth.

Alumina : – It is the chief constituent of every kind of clay. A good brick earth should contain 20 to 30 percent of alumina. This constituent imparts plasticity to earth so that it can be molded. If alumina is present in excess, raw bricks shrink and warp during drying and burning.

Silica -A good brick earth should contain about 50 to 60 percent of silica. Silica exists in clay either as free or combined form. As free sand, it is mechanically mixed with clay and in combined form; it exists in chemical composition with alumina. Presence of silica prevents crackers shrinking and warping of raw bricks. It thus imparts uniform shape to the bricks. Durability of bricks depends on the proper proportion of silica in brick earth. Excess of silica destroys the cohesion between particles and bricks become brittle.

Lime– A small quantity of lime is desirable in finely powdered state to prevents shrinkage of raw bricks. Excess of lime causes the brick to melt and hence, its shape is last due to the splitting of bricks.

Oxide of iron – A small quantity of oxide of Iron to the extent of 5 to 6 percent is desirable in good brick to imparts red colour to bricks. Excess of oxide of iron makes the bricks dark blue or blackish.

Magnesia – A small quantity of magnesia in brick earth imparts yellow tint to bricks, and decreases shrinkage. But excess of magnesia decreases shrink leads to the decay of bricks.

The ingredients like, lime, iron pyrites, alkalies, pebbles, organic matter should not present in good brick earth