Precast cement concrete blocks construction


Manufacturing

Mould:

Moulds will be manufactured utilizing mellow steel plates and mild steel plots for hardening the plates.

The shape ought to be either fixed sort or (box with four side dividers settled at corners, and top and base open) or split sort.

Split sort might be either singular or group mould. Where the compression of the solid is done physically, the mould might be either fixed sort or split sort. At the point when the sythesis of the compaction of the pieces is finished with surface vibrator, themould  might be just split sort (individual or gang mould)

Demoulding should be carried out 5 to 10 minutes after compaction. If there should arise an occurrence of fixed sort mould it may be pulled up with one side handles while pushing down the pieces with the place at top with help of finger. If there should arise an occurrence of split mould, the sides might be evacuated first and the segment plates (gang mould) should be pulled up in this manner.

Subsequent to demoulding, the pieces might be secured until they are adequately solidified to allow taking care of without dam.

Proportion:

The typical proportion of the blend should be as given. To acquire maximum strength, the water-cement proportion and working mechanism of the blend has to be controlled and appropriate compaction of concrete in the mould makes sure of age.

Casting:

After the process of blending, the concrete has to be positioned in the moulds straight away, being transported in metal gamelas or other suitable containers or by a chute.

The concrete has to be blended in a concrete mixer and the water-cement proportion has to be the least smallest, preferably by the utilization of a minute immersion vibrator or either  table vibrator.

 Curing:

The blocks which are stiffened should then have to be immersed and cured in a curing water tank or in a curing yard and has to be kept incessantly damp for minimum of 14 days.

 Drying:

After the process of curing, the blocks have to be thoroughly dried for duration of 14 days to 30 days based on weather prior to being utilized on the work. The blocks have to be allowed to fulfill their original shrinkage prior to the process where they are laid in a wall.

Dimensions:

Concrete masonry building units should be created in volumes and shapes to facilitate various construction needs. They incorporate  various factors like, header, jamb, bull nose, and partition block, stretcher, corner, double corner or pier, jamb and concrete floor units.

Concrete block hollow (exposed or closed) or solid has to be indicated to by its titular dimensions.

The nominal dimensions of concrete block should be, as follows:

Length : 400,500 or 600 mm

Height : 200 or 100mm

Width : 50, 75, 100, 200, 250 or 300mm

Furthermore, block should be produced in half lengths of 200, 250 or 300mm to match up to the full lengths.

Tolerance:

The greatest variation in the length of the units should not exceed more than +5mm and maximum variation and height and width of unit, should not exceed +3mm.

Density:

The void blocks should be given cavities in such a technique so as to make sure the maximum block density of 1600 kg/m3. The block density refers to the density is the density evaluated by dividing the mass of a block by the aggregate volume consisting holes or cavities.

Construction of Masonry

For the single storeyed buildings, the voids of blocks in establishment and cellar brick work should be topped off with sand and just the top establishment course should be of strong blocks. Be that as it may, for at least two storeyed buildings, solid blocks should be utilized as a part of establishment courses, plinth, and cellar dividers, unless generally showed. In the event that empty squares are utilized, their hollows should be topped off with bond concrete 1:3:6 utilizing 12.5 mm ostensible size totals.

  1. Wetting the blocks
  2. Layering
  3. Provision for window and door frames
  4. Intersecting walls
  5. Provision of roofs
  6. Piers
  7. Finishings

Pros & Cons

Advantages:

  1. High quality concrete is manufactured as it is feasible to have good technical facility in factories
  2. It is not compulsory to give joints in pre-cast manufacturing
  3. The labor necessary in the manufacturing procedure of pre-cast units could be trained with ease.
  4. The moulds utilized for preparation of the pre-cast units are of steel with precise dimensions in all directions. These moulds are comparatively more tough and they can be utilized multiple times.
  5. The pre-cast articles might be given the needed shape and concluded with preciseness.
  6. The pre-cast structures could be dismantled when necessary and they could be utilized elsewhere.

Disadvantages:

  1. If not efficiently handled, pre-cast units may incur damage while transporting
  2. It is hard to create satisfactory connection among pre cast members
  3. It is required to manage specific tolls for moving and lifting cast units.