Design, Development and Performance Evaluation of a Multiple Sandcrete Blocks Moulding Machine

Design, Development and Performance Evaluation of a Multiple Sandcrete Blocks Moulding Machine

Chapter One

Aim and Objectives

The aim of this research work is to design and fabricate a multiple sandcrete block moulding machine that can simultaneously mould three (3) blocks suitable for use by small and medium scale enterprises (SMEs).

The specific objectives of this dissertation are:

To carry out design analysis of the multiple blocks moulding
To fabricate and assemble the block moulding machine that will produce three (6 inch hollow) standard blocks in a single operation
To carry out performance evaluation of the
To carry out the comparative cost analysis of the design machine with the conventional block mould

CHAPTER TWO

LITERATURE REVIEW

Blocks were first known to have been in use at the river basin region of Mesopotamia as early as about 10,000 BC. The region had no stone or marble as those of ancient Egypt and Greece. So instead of using stones and marble, clay, mud, silt, and straw were used to make blocks that were baked before use (Swamy, 1986).

However, the durability became possible when blocks were fired in kilns. Excavations have uncovered perfectly fired blocks as far back as 5000 BC. Clay, silt and stave mix blocks, fired in kilns were used for a very long period up till 3000 BC when gypsum and lime mortar were used in the construction of the pyramids in Egypt. Many other similar materials were used, leading to the discovery of Portland cement and the production of concrete (Encarta, 2004).

Cement is one of the oldest forms of building materials which had existed for over 12 million years. It originated when the earth underwent an intensive geological change, as a result of chemical reaction which occurred between limestone and oil shale as they burned. Natural deposits of cement are found in Israel while interest in cement as a building material began in 1970s.

In 1973, John Smeaton found that the calcinations of limestone containing clay gave hydraulic lime which harden when water was added in controlled amount. In 1824 Joseph Aspdin invented Portland cement by burning finely grounded lime stone (chalk) with finely divided clay in a lime kiln until carbon dioxide was removed. This was the composition and method of producing cement, but modern methods have varied the compounds and controlled the composition (Olaf, 1974).

Concrete is an example of artificial engineering material made from cement, fine aggregate sand, coarse aggregate gravel mixed in the environment of air and water. Sometime a precise volume of air is introduced into the concrete mixture to produce desired properties such as improved workability, ductility, durability and also reduction to crack. Today, moulded concrete shapes are delivered to sites in plastic forms (Parry, 1979).

Fresh concrete is thoroughly mixed to adequate thickness desirable for the moulding process. This is followed by the filling of die cavity with the mixture, compacting and ejection of the green block from the cavity. Die cavities or moulds come in various sizes according to desired block size. Curing and drying complete the block production process.

The coarse and fine aggregate that make up part of the concrete are known as fillers while cement and water serve as binders. The fillers make up 70 to 80% of the concrete volume. Thus the binders which are expensive make up a smaller percentage, which lower cost (Swamy, 1986).

Two types of cement in the market are Portland and Ashpatic cements. Portland cement is used extensively as structural material. Asphatic cement is used for pavings. Concrete is reinforced before curing, with glass, fibres, and steel rods, to prevent cracks, and improve tensile and compressive strength.

Blocks

Blocks are the dominant units for modern wall construction in Nigeria and indeed West Africa. They are of many types depending on the constituent materials. The constituents also determine the structural characteristics of the blocks. The major types are sandcrete blocks (water, cement and river sand), soilcrete blocks (water, cement and laterite), concrete blocks, bricks (burnt clay and additives) and mud blocks.

The blocks come in various sizes and shapes and can also be classified as hollow or solid blocks and are bonded with binders, usually sand-cement mortar or lime. Blocks, according to Project National de Researche/Development (1994), can be regarded as a member of the concrete family. This is especially true for sandcrete blocks which differ from concrete by the non-inclusion of coarse aggregate in the mix.

Sandcrete blocks are composite material made up of cement, sand and water, moulded into different sizes (Barry, 1969). Nigerian Industrial Standard (NIS): 87- 2004) defined sandcrete as a composite material made up of water, cement and sand. It differs from concrete in terms of material composition because of the non-inclusion of coarse aggregate in the mix, and from mortar in that the slump is zero. As a matter of fact, sandcrete is often referred to as zero slump concrete. The behaviour of sandcrete is similar to that of concrete and for that reason the terms concrete and sandcrete will be used interchangeably in this work.

Sandcrete blocks are by far the most common type of block used in modern day construction in Nigeria. The sand, according to the NIS 87: (2004) “Shall be river, crushed or pit sand, clean and sharp and free from loam, dirt, organic or chemical matter of any description.” Their major advantages as compared to the other types of block are their easy mode of production and the speed of laying them. Their major setback is obviously their poor thermal and hygrometric properties. This can greatly affect their durability especially when they are permanently exposed to the elements.

To improve these properties, the walls formed with sandcrete blocks are normally rendered with cement-sand mortar. Sandcrete blocks are classified as solid or hollow blocks. Hollow blocks have cavities in them while the solid ones have no cavities. The length, width and height of the major sizes of sandcrete blocks produced in Nigeria are as follows:

CHAPTER THREE

MATERIALS AND METHODS

This chapter outlines the procedures adopted for implementation of this dissertation in order to achieve the stated objectives

The Description of the Multiple Sandcrete Blocks Moulding Machine

The multiple sandcrete block moulding machine has a rectangular shaped chassis that provides support for the machine as well as space for attaching some of the components of the machine. The machine also has a U-shaped frame attached to the chassis vertically at the midpoint., this arrangement helps in guiding both the moulds box and the ram when they are been lifted or lowered during operation. The machine mould box has three compartments for simultaneous casting of blocks. However, two (2) vertical rod were used to link it to the chassis with the aid of bearing for easy lifting and lowering during block production.

The chassis provides rigid support while the bearing provides lubrication and impact translatory motion to the mould box. These vertical rods connected to the box are extended to form the arm of the machine which is used by the operator to lift or lower the box during casting. In order to exert the required compaction pressure on the mixed sancrete, aram with six (6) pressure platens was arranged just above the mould box which keeps the sandcrete mix pressed in the mould box during vibration. Since vibration of the mix is vital to aid the agglomeration and compaction of the block, it was achieved by an assembly of eccentric weight and a compactor drive shaft driven by 3-phase electric motor at 1450 rpm which is higher than the speed used by Olusegun and Adeboye (2009). The eccentric weight was welded off the centre of the shaft to create an off-centre-rotation thereby generating vibration in the machine.

CHAPTER FOUR

RESULTS AND DISCUSSION

This chapter presents the design calculations for the multiple sandcrete blocks moulding machine and analyses the results of the compressive strength and water absorption tests carried out on samples produced from the newly designed and fabricated sandcrete block moulding machine as compared with those obtained from a conventional machine.

CHAPTER FIVE

CONCLUSION AND RECOMMENDATIONS

Conclusion

From the design analysis and performance evaluation, the following conclusions were drawn:

A mobile multiple sandcrete block moulding machine was successfully designed and developed which can be operated by only two (2) semi-skilled labours without the use of pallet for curing the sandcrete
The newly developed sandcrete block moulding machine was able to produce three (3)standard 450mm x 225mm x 150mm (6 inches) sandcrete blocks simultaneously at the rate of 1.4 block per minute leading to total production of 664 blocks per eight hours working
The performance evaluation tests carried out on sample sandcrete blocks from the developed machine revealed that they have average compressive strength of 78N/mm²and water absorption of 10.35%, which compare favourably with samples from commercial machine.
The cost of production for the multiple sandcrete block moulding machine was estimated to beN 105,600.00.

Recommendations

For further work and improvement on this research, the following are recommended:

Design should be optimized to accommodate mould with higher number of cavities of other sizes (e.g. 9 inches) to increasethe production rate of the machine.
The ejection mechanism of the machine should be automated by the use of electric motor for the safety of the
A tray should be incorporated directly opposite the mould box for easy feeding of the sandcrete mix into the

REFERENCES

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