EFFECT OF PARTIAL REPLACEMENT OF SAND WITH LATERITIC SOIL IN SANDCRETE BLOCKS

ABSTRACT

Of recent, the attention of most researchers is shifting towards the optimization of building materials by using local contents; the use of indigenous materials; and local industrial by-products unique and abundant in certain localities. This study therefore explored ways in which lateritic soil could be utilised in hollow sandcrete block production in Ota, Ogun State, Nigeria. Sandcrete blocks were made with lateritic soil taken from different sources replacing the conventional fine aggregate (local river sand) in steps of 10% up to 60%. Their compressive strengths determined to check for conformity with standard sandcrete block as specified in the  Nigerian National Building Code (2006) with a view to determine the acceptable  percentage replacement. Soil tests were performed on the lateritic soil samples to characterise the soils. Classification of the lateritic soil samples within Ota revealed that the lateritic soils are mostly sandy clay of high plasticity and may replace sand by up to 20%, though an approximate linear decrease in strength with increasing sand replacement with lateritic soil was observed. This percentage replacement can be recommended to the block making industries within Ota with a view to encouraging utilization, though it is encouraged to confirm the percentage before embarking on mass block production.

CHAPTER ONE

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 has unequivocally 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.