Use of hand moulded chip concrete blocks for single storey houses

Abstract

Sri Lanka is at present facing serious environmental problems due to over-exploitation of its natural resources as building materials. The examples are the problem associated with sand mining and clay mining. Sand is extensively used for brickwork construction. Clay is used for manufacturing of bricks. Therefore, there is an urgent need to find alternative building materials that can reduce the use of these depleted natural resources.

In this context, hand moulded chip concrete (HMCC) blocks can play an important role. It can reduce or eliminate the use of sand by using quarry dust and chips; both are by products of metal crushing industry. These blocks can be manufactured to any desirable width since the width of the mould can be adjusted. Thus, it is possible to anufacture 125 mm and 100 mm blocks that can be used for external and internal walls, respectively. These thicknesses are allowed according to the building regulations. It is also possible to give a reasonable finish so that there is a possibility to avoid plastering.

With a detailed experimental study, it is recommended that 1:8:14 cement, fine aggregate and chip mix could be used for manufacturing of the blocks. As the fine aggregate, sand or quarry dust can be used depending on the availability. It can give a strength in excess of 1.2 N/mm2 recommended in SLS 855 : Part 1 : 1989.

It was found that a characteristic strength of 0.9 N/mm2 can be safely used for the block walls constructed with HMCC blocks. This is a strength sufficient for majority of probable load cases that occur in a single storey houses.

A cost study carried out has indicated that the hand moulded chip concrete blocks can have a cost comparable with these available in the market. Since these blocks can be cast by the house builder at the site, it would be advantageous for rural communities who depend on small loans or grant for the construction of the houses, given by the governmental or non-governmental organizations.