RESIDUAL STRENGTH OF LATERIZED CONCRETE AT ELEVATED TEMPERATURE

RESIDUAL STRENGTH OF LATERIZED CONCRETE AT ELEVATED TEMPERATURE

ABSTRACT

The study investigated the residual strength of laterized concrete at elevated temperatures. Two concrete mixes incorporating 0 and 20% laterite as a replacement by weight of sand was prepared. A concrete mix ratio 1:2:4 (cement: sand/laterite: granite) with water cement ratio of 0.70 was used for the study. The laterite in fine aggregate was varied from 0 – 20% at 20 interval. Specimen cured for 28days were subjected to varied elevated temperatures of 150, 300, 450 and 600ºC, and later subjected to uniaxial compressive loading test. The results however showed that at varying percentage replacement of sand with laterite, compressive strength of laterized concrete decreases. Also, with increased temperature, the strength also decreases. A maximum compressive strength value of 20.96N/mm was obtained for the mix with 25% laterite -75% sand at 150ºC, which indicates the strength of laterized concrete that is sufficient for use at elevated temperature not exceeding 150ºC.

CHAPTER ONE

INTRODUCTION

1.1       Background of Study

Concrete is a hardened end product of mixture of cement, coarse and fine aggregate and water, where the cement act as binder and the aggregate been fine or coarse served as filler in the presence of water that aid the reaction.

The use of alternative constituent in construction material is now a global interest due to high demand and scarcity of raw material for conventional concrete and it has led to high cost of construction material. This has compelled researchers to intensify work on laterite with a view of investigating its usefulness as partly or wholly replacing river sand as fine aggregate in conventional concrete. According to Osunade, (2002) sand in concrete production is the second most costly item per unit volume of concrete. Therefore by replacing sand with laterite soil which is under ultilized presently in Nigeria can help reduce the cost of construction.

Laterite is available in most humid, tropical and sub-tropical countries. It is considered as a product of highly weathered geologic material and is rich in sesquioxides (secondary oxide of iron, aluminium or both). Laterite has been found very useful over decades as a constructional material for shelter and approximately 30% of world’s present population still lives in laterite structure (Cofirman, et al; 1990). Laterite is a cheap, environmentally friendly and abundantly available building material in the tropical region (Ata, O., 2003; Olusola, K., 2005; and Binici, H. et al, 2004).

When concrete contains laterite in its raw form as partly or whole replacement for fine aggregate (sand) in concrete production, it is referred to as latcon or laterized concrete. Concrete as a leading construction material in civil engineering is sometimes exposed to elevated temperatures due to hazard (vodak et al., 2004). The compressive strength of concrete is essentially reduced when it is exposed to elevated temperatures which may result in undesirable failure of the structure. To assess the strength of concrete after a fire entails determining the strength sample subjected to crushing which leads to loss of sample. This becomes imperative to search for other means of strength assessment that will be viable.

1.2       Aim and Objectives  

1.2.1    Aim

The study is aimed at determining the residual strength of laterized concrete at elevated temperatures using compression testing machine.

1.2.2    Objectives

The objectives of the study are as follows;

• To prepare cubes and cylinder of (150 x 150 x 150mm) of normal and laterized concrete and subject them to 25°C, 150°C, 300°C, 450°C and 600°C respectively.
• To cool the cubes subjected to elevated temperatures by natural cooling (open air cooling).
• To determine the residual compressive strength of normal concrete and laterized concrete using compression testing machine.

1.3       Justification

Despite the abundance of laterite soil all over Nigeria, the need for its usage as partially or wholly to replace fine aggregate in concrete as laterized concrete cannot be over emphasized. Presently its suitability and residual strength are determined by destructively. Hence, it is imperative to derive a means of determining these properties accurately. Uniaxial compressive machine will help to solve the problem.

1.4       Scope of Study

This research project focuses on assessing the quality (strength) of laterized concrete at elevated temperatures using uniaxial compressive testing machine.

1.5       Limitation of Study

The findings of this study will depend on the empirical relationship between concrete strength and the machine.

CHAPTER TWO

LITERATURE REVIEW

2.1      Concrete

Generally concrete is a construction material which comprise of about 60% to 80% of aggregates either as fine or coarse (Chang, 2011). It has been used extensively in construction industry for many years. Concrete is a hardened end product of cement, coarse aggregate, fine aggregate and water when combined and mixed together in a right proportion. Concrete scientific principles (CSP, 2012) says that concrete constituent are mixed properly together, deposited and allowed to solidify into a rock-like structure through hydration.

It is important to select the constituent materials for concrete, combine them in right proportion so as to produce a suitable concrete for a particular purpose.

2.1.1    Types of Concrete