CHAPTER ONE
INTRODUCTION
This research work means to determine the different properties of sandcrete blocks moulded with a locally excavated sand, in terms of compressive strength, durability and cost and economic importance, and that of River Sand. And after, compare the two strengths of the sandcrete which will help in recommending the right give the desired strength for the designed strength for a particular purpose. NSUDE as case study, Nsude is in Udi, Enugu west, Enugu State.
1.1 BACKGROUND OF THE STUDY
Sandcrete is a yellow-white building material made from a binder (Portland cement), sand in a ratio of circa 1:8, and water. Sometime other ingredients may be added to reduce the amount of Portland cement such as “pozzolanas and rice husk ash”. Sandcrete is similar but weaker than mortan for which the ratio is 1:5. Sandcrete is usually used as hollow rectangular blocks similar to concrete masonry units, often 45cm (18”) wide, 15cm (5.9”) thick and 30cm (12”) with hollows that run from top to bottom and occupy around one third of the volume of the block.
1.2 STRENGTH AND USAGE
The final compressive strength of sandcrete can be as high as 4.6N/mm2 which is much less than concrete’s 40N/mm2. Sandcrete is unsuitable for load-bearing columns, and is mainly used for walling of a house – making a fence – Septic tank and soak away tank’s – Building a generator’s house. In Nigeria, measured strength of commercial available sandcrete blocks was found to be between 0.5 and 1N/mm2, which is well below the 3.5N/mm2 that is legally required. This development may be due to the need of the manufacturers to keep the price low, and since the main cost-factor is the Portland cement, they reduce that, which results in a block that starts behaving more like loose sand.
1.3 SANDCRETE BLOCK SIZES
They are many different types of blocks used in modern building, they include: · 9” hollow blocks (450mmx225mmx225mm) · 6” hollow blocks (450mmx150mmx225mm) · 6” solid blocks (450mmx150mmx225mm) · 5” solid blocks (450mmx125mmx225mm) · 9” solid blocks (450mmx225mmx225mm)
1.4 CONSTITUENT MATERIALS OF SANDCRETE BLOCKS
These include cement, fine aggregate (sharp sand) and water.
1.4.1 CEMENT
This refers to any adhesive and the material used in connection with block and it is referred to as “hydraulic cement” because the setting and hardening depends on the preserve of water. The cement widely used in civil work is called “Ordinary Portland Cement”.
1.4.2 FINE AGGREGATE
The two major types of sand used are white and coloured sand. The sand were not free from materials such as dust, silt, tree roots etc. The sources of sand include pits, rivers and sea.
1.4.3 WATER
Any type of water available can be used to mould sandcrete blocks. This includes water from stream, rivers, boreholes etc.
1.5 STATEMENT OF THE PROBLEM
Apart from bad mixing ratios, which happen even some sandcrete blocksproducers add more yield of blocks, some other things can cause blocks to be in bad condition which can affect the quality of the sandcrete produced.