Concrete blocks are one of the most popular construction materials in Nepal which are used in the construction industry almost everywhere. Also called cement blocks, they are used for constructing exterior and interior load bearing walls, partition walls, fire-safe walls, piers, columns and retaining walls. They are lightweight and are easy to put together.
The void area of hollow concrete blocks is greater than 25% of the total area. The solid area of hollow bricks should be greater than 50%. This composition makes the structure lightweight and equally durable, strong and long lasting.
Cement, aggregate, and water are used to prepare concrete blocks. The cement-aggregate ratio in concrete blocks is 1:6. Aggregate used is of 60% fine aggregate and 40% coarse aggregate. Other additives that can be used are volcanic ash, granite rubble, sand, broken glass, brick, concrete, hardened cement, expanded clay, river gravel, crushed stone, sawdust etc.
The standard size of concrete hollow blocks in Nepal is 390X200X190 mm3 (15.35X8X7.5 inches). There are also other variations with different widths in 390X150X190 mm3 (15.35X6X7.5 inches) and 390X100X190 mm3 (15.35X4X7.5 inches).
The standard side surface area of a concrete hollow block in Nepal is 0.0741 meter square. For a 100 meter square wall, we need 1350 units of hollow blocks.
The minimum compressive strength required for a concrete block is 3 N/mm2 . Grade A concrete blocks have strength between 5 to 15 N/mm2 while Grade B blocks have strength between 3.5 to 5 N/mm2.
The required density for Grade A concrete blocks is more than 1500 kg/m3 while for Grade B, it is between 1100 to 1500 kg/m3.
The prices of concrete hollow blocks in Nepal depends upon the manufacturers, quality of products, competition in the market and the district where the manufacturing is done. The average price in different districts in Nepal is Rs 58 per block. The price also varies with the ratio of cement used, the cost of cement in the manufacturing place and the delivery charge. The average price in Kathmandu for a 6 inch wide block is Rs 75 and for a 4 inch wide block is Rs 65. The cheapest blocks are in Makwanpur where the average cost per block is Rs 33 which is below the overall average. For high quality concrete hollow blocks from premium brands that provide assurance of durability and reliability, the average cost is Rs 86 for a 4 inch wide block and Rs 100 for a 6 inch wide block without delivery charge.