Solid and hollow concrete blocks are manufactured in factories to meet the requirements of building blocks in cities and towns. These blocks may be called as artificial stones, since they replace the stones in the masonry construction. They are manufactured with lean mixes of cement, sand and aggregates of sizes less than 12 mm. Instead of sharp edged aggregates, round aggregates are professed in the manufacture of these blocks. The properties and uses of these blocks is given in this article.
(i) Solid Concrete Blocks: Solid concrete blocks of size 400 mm × 200 mm × 150 mm are commonly manufactured. To reduce the weight of the block no fine concretes are preferred. No fine concrete is the concrete in which fine aggregate is not used, but round aggregates of size less than 12 mm are used. IS:2185 (part I) 1983 covers the requirement, for such blocks.
The blocks should satisfy the strength requirement of 4 N/mm2. Their density should be as low as possible, so that handling is not difficult. They should have sharp edges which are at right angles to each other.
These blocks are used for load nearing wall construction also.
(ii) Hollow Concrete Blocks: To reduce the weight of concrete blocks, they may be made hollow as shown in Fig. 5.1. Hollow blocks of sizes 400 mm × 200 mm × 190 mm (nominal size 400 × 200 × 200 mm) and also of sizes 400 mm × 300 mm × 190 mm (nominal size 400 × 300 × 200 mm) are manufactured. IS:2185 (part I) 1983 covers the specifications for these blocks.
These block need richer mixes. Fine aggregates upto 60% and coarse aggregates upto 40% are used.
These blocks also should satisfy the strength requirement of 4 N/mm2. They should have truely right angled corners.
Advantage of using concrete blocks is that the construction activity is fast. Mortar requirement for finishing the surface is less. Pointing alone is sufficient, in other words plastering is not necessary.
Table 5.2 gives the differences between solid and hollow concrete blocks.
Both solid and hollow blocks can be used for the construction of load bearing as well as partition
walls. They are ideally suited for the construction of compound walls.