COMPARING THE STRENGTH OF BLOCKS MADE FROM CEMENT AND LATERITIC SOIL WITH LATERITIC AND BITUMEN

1.0 Introduction

1.1 Background Of The Study

Most African countries are confronted with acute housing problems regardless of their socio-economic and developmental challenges. While the situation is felt by majority of the population, the most affected are the low-income earners, the unemployed and rural dwellers. This has been attributed to the adaptation of highly mechanized and capital-intensive production facilities in an attempt to meet the ever-increasing demand for building materials. One way to improve this situation is by making basic materials available in sufficient quantities, and at affordable prices, to prospective builders, including low-income earners.

One building material which has arguably revolutionized the construction industry in Ghana is sandcrete block or brick normally used as a walling unit. These walling materials have been an essential element in the housing delivery in Ghana predominately due to their affordability, availability, versatility and durability characteristics.
In Ghana, the supply of quality sand for construction purposes has seen a sudden surge in demand which hasunequivocally been associated with numerous environmental and habitat damage not forgetting the skyrocketing cost of procuring this material. Some of these challenges have compelled researchers to intensify works on alternative building materials which could satisfactorily perform wholly or partially as a substitute for the natural sand in the production of sandcrete blocks so as to bring down the cost of construction. One of the forefront suggestions has been the provision of local alternatives to the use of natural sand as fine aggregates.

One such material is the fines of laterite (particle sizes < 10mm) known to have some similar physical characteristics as conventional sand. Previous works [21] on laterites shows sharper variations in the particles sizes than sand after preliminary assessment of the particles size distribution. This has quicken interest on the use of laterite in structural masonry works especially concrete as the particle sizes contribute significantly to the strength properties of building materials.

Lateritic soils undergoes weathering and laterization processes which involve chemical and physico-chemical transformation of primary rock-forming minerals that are rich in secondary oxides of iron, aluminium or possibly both laterite constituents and clay minerals [8]. These processes occur predominately in the tropics by intensive and long-lasting weathering of the underlying parent rock. It is nearly devoid of base and primary silicates but may contain large amount of quarts, and kaolinite. It has been used in the construction of Adobe, Wattle and daub and making bricks for buildings. Although, its use as a construction material has been extensive, it is hardly accepted due to insufficient technical data, hence limiting its wider application in the analysis and design of structures built of laterites.

In recent times, researchers have shifted focus on the alternative material like laterite for sand in the production of concrete referred to as laterized concrete. The use of laterite as fine aggregate was first studied by. He concluded that concrete containing laterite fines in place of sand could satisfactorily be used for structural members. It was also discovered that the most suitable mix of laterized concrete for structural purposes is (1:1½:3), using batching by weight with a water/cement ratio of 0.65, provided that the laterite content is kept below 50 percent of the total fine aggregate content [3]. Using a combination of crushed granite, sharp sand and fine laterite was used in their experiment, they further asserted that compressive strength of not less than 25N/mm2 was obtained at 28days for the mix with laterite content between 25-50%. It was also reported [12] that incorporating laterite soil should not exceed 20% of the sand used in their sandcrete block production in Ota, Nigeria.

Whilst the use of laterite as a substitute for sand in concrete has been extensively documented, the same cannot be said of its use in the production of sandcrete bricks especially in Ghana. Since laterite varies extensively, averred that the compressive strength of lateritic soil is dependent on the source from which they were collected. It is therefore imperative to find an avenue of utilizing laterite in the production of sandcrete bricks which can reduce cost and environmental destruction due to its availability.

1.2 Statement Of Problem

High cost of building materials has been the bane of construction industry in the developing countries of the world as a result of importationof most of the building materials. As prices increase sharply, there is a growing awareness to relate research to local materials as alternatives for the construction of functionalbut low-cost dwellings both in the urban and rural areas of Nigeria. One of such local material that is being researched is lateritic soil. Lateritic soil has been one of the major building materials in Nigeria for a long time. The main reason lies on the fact that it is readily available and the cost of procuring it is relatively low.

Lateritic soil possesses other advantages which makes it potentially a very good andappropriate material for construction, especially for the construction of rural structures in the developing countries. These merits include little or nospecialized skilled labour required for laterizedsandcrete blocks production and for its use in other construction works; and laterized concrete structureshave potentially sufficient strength compared with that of normal concrete (Lasisi and Ogunjimi,1984).

This study is part of the continuing effort to investigate the characteristics of lateritic soils, stabilized (mostly with cement or lime) or unstabilized, reinforced or unreinforced, with the view to improving such characteristic. This study is specifically focused on the effects of replacement of the conventional fine aggregate(sand) with lateritic soils found in Ota on the compressive strengths of laterizedsandcrete blocks.Lateritic soils are essentially the products of tropical weathering usually found in areas where natural drainage is impeded (Amu et al., 2011; Lasisi and Osunade, 1984). From an engineering point of view, laterite or lateritic soil is a product with red, reddish brown and dark brown colour, with or without nodules, ability to self-harden, concretions, and generally (but not exclusively)found below hardened ferruginous crusts or hard plan (Ola, 1983). Lasisi and Ogunjide (1984) assert that the degree of laterization is estimated by the silica sesquioxides ratio (SiO2/ (Fe2O3 + Al2O3)). Silica-Sesquioxide (S-S) ratio less than 1.33 are indicative of laterites; those between 1.33 and 2.00 are lateritic soils and those greater than 2.00 are non-lateritic types.

According to Akintorinwa et al., (2012), lateritic soil abounds locally and its use is mainly limited to civil engineering works like road construction and land fill operations. It is less utilised in the building industry except in filling works. In lieu of the abundance of lateritic soils and its availability, its optimumuse in building production could positively affect the cost of buildings leading to the production of more affordable housing units (Joshua and Lawal, 2011). Its use in the building production is not yet generally accepted because there are no sufficient technical data on it, hence limiting its widerapplication in building construction work (Udoeyo et al., 2006).

Studies are currently going on in the use of lateritic soil in concrete production where laterite is made to partly or wholly replace conventional fine aggregate in the production of concrete known as laterized concrete; and in the production of brick units such as Compressed Laterized Brick (CLB) usually stabilised withcement. Presently, these applications are mostly limited to buildings in rural areas and low income housing projects which are mostly situated at satellite areas (outskirts) ofCentral Business Areas (CBA’s).

This research project is aimed at investigating the effects ofpartial replacement of sand with lateritic soil in the production of sandcrete blocks. It sought to compare the variouspercentage replacements with the standard requirements of a sandcrete block as specified in the Nigerian National Building Code (Federal Republic of Nigeria, 2006) and derive the maximum replacement that will satisfy the code.

1.3 Purpose Of The Study

The research project work is on comparing the strength of blocks made from cement and lateritic soil with lateritic and bitumen. Due to continue use of the aggregate, river sand is becomes scare and the production of concrete is degrading the environment. It affects the living organism of river severely because the surface of river sand goes downwards in the river bed. This will affect the storage capacity of river and leads to severe water scarcity during lean season. So there is an imperative need to develop alternative materials for replacing natural river sand in concrete.

For reducing the usage of the raw material large replacement is done using the various by-product materials that are available in the present day. Many studies are made with several other materials which gave the concrete to be a material made of recycled material. The properties of concrete in fresh and hardened state are studied in the various papers that are used as a reference for this. Some of the properties are compressive strength are the major one that are considered.

1.4 Research Questions

1. Can lateritic soil be used to replace sand in the production of sandcrete blocks?
2. What effect has the partial replacement of sand with lateritic soil in production of sandcrete blocks?

1.5 Significance Of Study

This research work is imperative to find an avenue of utilizing laterite in the production of sandcrete blocks which can reduce cost and environmental destruction via its availability. This project work is of great significance to engineers and building construction experts, as well as the academia and body of knowledge.

This research project also will serve as a reference point to other future researchers and students on related fields of study.

1.6 Study Justification

From preliminary works, the closest construction element with laterite as part of its material in masonry is the compressed laterized earth brick stabilized usually with cement or lime. The use of this brick is either in the rural areas or in a low cost housing project.

Unfortunately, despite the establishment of about twenty brick manufacturing plants in Nigeria since 1976 and the low-cost of locally produced bricks, their application in the building construction industry has not gained much popularity except in very few occasions where the government took the initiative to deliberately utilise stabilized compressed lateritic and clay soil like the case of Aco Hi Techin Lugbe, Abuja and few others (Joshua and Lawal, 2011).

Hence, this study seeks to find a way of incorporating laterite in the production of sandcrete hollow blocks.
Sandcrete blocks are constructional masonry units that have been generally accepted to the extent that when an average individual thinks of building, the default mind-set is the use of sandcrete hollow blocks.

Hence, this research seeks to find a way of incorporating the use of laterite in its production for a probable cost reduction, local content utilisation, creation of local employment and development of indigenous technology as a result of its ready availability.