(1) Raw materials utilized in Concrete Blocks :
The primary materials for developing the concrete blocks are aggregates, cement and water. Different types of aggregates are applied with changeable degree of success and they consist of crushed stones, gravel, volcanic cinders, foamed slag, furnace clinker, etc. In order to choose the aggregates, the factors like weight, texture or composition of the unit designed should be considered. The stability, texture and low-cost of the concrete block are subject to the grading of the aggregate cautiously. The cost will be reduced if locally accessible aggregate is used. The ordinary Portland cement is utilized for raw material. The required water should be the normal potable water.
(2) Concrete blocks manufacturing process:
The completely automatic plants are used to develop concrete blocks with superior strength. These automatic machines can made superior quality concrete blocks. But huge capital investment is required to set up & operate these machines. The transportation cost from the production area to the place of actual use will also be reduced for concrete blocks if the manually operated machines are installed at construction site itself.
The following manufacturing process is required for developing the concrete blocks :-
(i) Choice and ratios of ingredients: The primary factor for selecting the ingredients is the desirable strength of the block. If the coarse aggregate is mixed in perfect ratio, the strength of the quantity of cement applied will be superior.
(ii) Blending of ingredients: The aggregates, cement and water should be blended in a proper way. The mixing should be done through a mechanical mixer. While mixing manually, great care is necessary to check that the cement and aggregates are initially blended comprehensively in dry state and the water is then included slowly.
(iii) Positioning and vibration: The mixed concrete material is delivered into the mould box up to the top level and check carefully that the box is filled uniformly. The vibration of concrete is performed until it is set evenly in the mould box.
(iv) Curing: The block is drenched with water after around one day of casting and it should be sustained for at least 7 days and if possible up to 28 days. If the time for curing extends for a prolonged period, the block will be superior.
(3) Benefits of concrete blocks:The application of concrete blocks as a masonry unit is found on several construction sites due to the following benefits:
- It extends the carpet area of the building due to the small width of concrete block with regards to the brick masonry wall.
- It offers superior thermal insulation, improved fire resistance and strong absorption capacity.
- It can save major agricultural land which is applied for manufacturing bricks.
- The blocks are developed in an efficient manner so that the vertical joints can be taken back automatically and so the time spent for the careful supervision is minimized.
- The process for developing concrete block masonry is simpler, rapid and stronger as compared to the brick masonry.
- The shape and size of the concrete block is very accurate and it simplifies the work of a mason.
- As the numbers of joints are minimized, the time is saved for developing the mortar.
- The utility will be augmented by creating the reinforced concrete block (RCB) masonry units. The blocks are provided with two holes for arranging perfect reinforcing bars and the structure with RCB units could carefully withstand wind and earthquakes, if so designed. The conventional beams and columns are totally removed and the structure with RCB units will have a superior appearance.