Quality and standardization of all construction materials are of paramount importance and serves as a yard sticks for measurement reflecting the level of development attained by a nation. Sandcrete blocks are construction materials which have gained wide acceptance and used in the construction industries because of the many characteristics properties attached to them. In this research the study enhanced on the compressive strength of hollow sandcrete block. The test was done in accordance with the British Standard 2028(1968), while grain size distribution analysis was conducted on the sand aggregate and crushing stone used which is suitable for block making. Compressive strength test was carried out on the sandcrete block for each percentage of replacement on 7, 14 and 28days. Result of the experiment shows that the inclusion of crushing stone in the sand cement enhances the compressive strength of sandcrete block. Sandcrete block made with (1:8) mix proportion using 20% granite fine replacement give optimum compressive strength of 6.58N/mm². While the block produced using 15% has 5.77N/mm², control has 4.41N/mm², 5% has 4.39N/mm² and 10% has 4.04N/mm². Standardization of block manufacturing process and strict supervision of the manufacturer by the council for the regulation of engineering practice in Nigeria were recommended as measures to improve the qualities of sandcrete blocks.

Key Words: Sandcrete blocks, Compressive strength, Construction, Standardization.

1.1 Background of study
Blocks are made from mixture of sand, cement, and water and are called sandcrete blocks they are used extensively in all Africa countries including Nigeria for wall in building for a long time until perhaps few years ago, Abdullahi, M. (2005), this are manufacture in many part of Nigeria without any references to any specification either to suit local building requirement or for good quality work. Apart from using block wall for laterite, wood, and other forms of walling units have been used in building construction, but they have not made much progress when compare to the use of blocks.

The same can also be of bricks, the properties of block of interest include comprehensive strength, fire resistance, durability thermal conductivity and sound resistance these properties are dependent on the relative proportion of the constituent and the method of production process.

Traditionally, sandcrete blocks are made of cement, natural river sand, and water.

The constituent is mixed and placed in a mould which is remove immediately after compaction and leveling of the top. The newly produced block is self –supporting; hence they are often referred to as zero slump concrete. Individual blocked are joined together, after curing, to form walls using cement –sand mortar. But due to the scarcity and high cost of natural sand, there have been a growing interest especially in the developing countries in the use of crushed stone (or granite fines) in the production of blocks , concrete , and masonry product . Sand –quarry dust blocks are sandcrete block in which the sand portion has been partially replaced with granite fine (crushing stones)

The use of quarry dust or crushed stone in hollow sandcrete block according to Chaturanga, Arama,Wiranjith ,Dissanayake ,Haniffa, and Patanbandige (2008) is desirable because of the benefits such as useful disposal of a byproduct , and reduction of river sand consumption and increase in strength . Crushing stone has rough, sharp and angular particles, and as such causes a gain in strength due to better interlocking. Crushing stone has been identified as possible replacement for sharp sand inn concrete works.

Granite rock is abundant in Nigeria giving rise to many quarry sites with large heaps of quarry dust, hence, quarry dust can be reasonably used as alternative to river sand, Shahul and Seker,(2009) observed that natural sand is not usually graded properly and has excessive silt, while quarry rock dust does not contain silt or organic impurities and can be produced to meet desired gradation and fineness as per requirement . This consequently contributes to improving the strength of sandcrete block. Agbede, Joel ,(2004) described quarry dust as a cohesionless sandy material acquired either naturally (which is rare) or artificially by the mechanical disturbance of parent rocks (blasting of rocks )for construction purpose composed largely of particles with a diameter range from 0.05mm to 5.00mm . They found in their study on “suitability of granite stone is cheaper than River Benue sand during rainy season.

1.2 Statement of the Problem
River sand and cement are the major components of the building materials in the construction industry. The manufacturing of sandcrete blocks heavily relies on river sand and cement. As construction activities continue to increase, there is an over reliance of river sand and cement in sandcrete blocks production and in the entire building industries. This has caused negative impact on the environment. Sand harvesting and mining activities during cement production causes the destruction of vegetation, reduces fertile land and farm productivity and exposes the local community to food shortage (Kavilu, 2016). According to Lawane and Pantet (2012), the building sector is responsible for more than 50% of CO2 emissions and energy consumption due to production of building materials and construction operations. The process involved in the manufacture of cement has also led to high emissions of CO2 to the environment.

Building materials are the largest single input in housing construction. According to Adedeji (2010) about sixty per cent (60%) of the total housing expenditure goes for the purchase of building materials; Arayela (2005) on the other hand says that cost of building materials constitute about 65% of the construction cost. Oyewobi and Ogunsemi (2010) states that building materials form the main factors that restrict the supply of housing and ascertain that they account for between 50-60 percent of the cost of buildings.

The significant increase in cost of construction has resulted into a shortage of decent housing in Africa. For example Kenya’s housing deficit is estimated at 200,000 housing units per year (Mwololo, 2016). This is a figure that local developers and the government are unable to meet due to the ever-rising costs of conventional building materials (Mwololo, 2016). These housing deficit means that majority of the population lives in substandard housing. New and cheaper sources of masonry system such as use of prefabs and compressed stabilized soil blocks are being exploited (Thuita, 2016). The use of alternative sources of the materials are limited due to inadequate data to encourage their utilization.

The available sources of natural fine aggregate are also getting exhausted (Palaniraj, 2003). This has lead formation of exigent legislation regarding the environment. Consequently, quality building materials have be transported from long distance, adding to the cost of construction. In some cases, natural fine aggregate may not be of good quality. Therefore, it is necessary to replace or supplement natural fine aggregate used in sandcrete. Locally available fine aggregate and pozzolanic materials needs to be exploited and used partially or completely in sandcrete blocks production without compromising the quality of sandcrete blocks.

Studies have reported a loss of strength when cement is replaced with an agro waste material (Adewuyi et al. 2013; Oyekan & Kamiyo, 2011). A blend of coarse lateritic sand and fine marine sand, proposed in this research, has potential of producing high strength sandcrete block. This allows less cement to be blended together with an agro waste pozzolanic materials such as SBA without compromising the recommended sandcrete strength.

Studies and subsequent use of nonconventional materials in sandcrete production would lead to the reduction of the environmental impact, reduce cost of construction, reduce house shortage, supplements the available sand and cement sources and provide data to encourage their utilization. The dry stacked hollow sandcrete blocks (DHSBs) made with non-conventional materials proposed in this research would help in reducing these problems.

1.3 Objectives
1.3.1 Main Objective
comparing the compressive strength of manual compacted sandcrete hollow blocks to machine vibrated sandcrete hollow blocks

To investigate the structural performance of dry sandcrete hollow blocks produced using lateritic sand and marine sand, as complete replacement of fine aggregate, and machine vibrated sandcrete hollow blocks as partial replacement for cement.

1.3.2 Specific Objectives
1. To assess the performance and determine the optimal mix of lateritic sand and marine sand as fine aggregates, and bagasse ash as partial replacement of cement for production of sandcrete blocks.

2. To assess the performance of dry sandcrete hollow blocks made from optimal mix.

3. To assess the structural behavior and failure mode of wall models made from the dry sandcrete hollow blocks.

1.4 Research questions
1. What is the performance and the optimal mix of lateritic sand and marine sand as fine aggregate, and bagasse ash as partial replacement of cement for production of sandcrete blocks?

2. Does the optimal mix of SBA, and blended lateritic and marine sand produces DHSBs that meets the strength and durability requirements for hollow sandcrete block?

3. What is the structural behavior and failure mode of wall models made from the types of DHSBs?

1.5 Justification
The most common walling materials are building stones, blocks and clay bricks. The escalating price of building stones and clay bricks coupled with the depletion of the natural sources for the materials necessitates the development of an alternative walling materials. Use of laterite and marine sand eliminates use of river sand in sandcrete blocks, also cement use is reduced by use of pozzolanic machine vibrated sandcrete hollow blocks in cement. Reducing the amount of cement used in building will decrease the amount of CO2 emitted and energy used for construction. The large carbon emissions come from electricity generation, transport, industries and building operations. Also, when compared with fired clay bricks, the production of sandcrete blocks does not involve the firing process.

Research shows that there is an over reliance of natural fine aggregate in construction industry. The conventional river sources are also getting depleted. The inherent properties of lateritic sand and marine sand make them suitable for use as fine aggregate in producing dry stack hollow sandcrete block. The technique of building with dry stack hollow blocks eliminates the need for mortar and consequently reduces volume of the required building materials and subsequently the cost of construction.

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Item Type: Project Material  |  Size: 42 pages  |  Chapters: 1-5
Format: MS Word  |  Delivery: Within 30Mins.


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