APPLICATION OF SCHEFFE’S MODEL IN COMPRESSIVE STRENGTH OPTIMISATION OF CONCRETE USING RICE HUSK ASH AS PARTIAL REPLACEMENT OF CEMENT

ABSTRACT

This  study  investigates  the  economic  application  of  scheffe’s  model  in  compressive strength optimisation of rice husk ash-cement concrete. Physical properties of the aggregates such as specific gravity, bulk density and sieve analysis were determined. Specific gravities of fine and coarse aggregates were 2.64 and 2.66 respectively. The bulk densities were 1745kg/m3 and 1660kg/m3 respectively. From the sieve analysis test, the sand belonged to zone 2 and well graded with coefficient of gradation of 1.04. Ninety 150mm x150mm x 150mm cube specimens were produced for the compressive strength test. Model was fitted to data obtained on the compressive strength and mathematical model was developed based on Scheffe’s model. The formulated model was tested for adequacy at 95% level of confidence using t-statistic and was found to be adequate. The compressive strength of concrete was observed to decrease with increase in the percentage replacement of cement with rice husk ash. The reduced value of the compressive strength may be due to lower specific gravity value of rice husk ash compared to that of cement. The blending of the two materials caused a reduction in strength value of the end product since specific gravity is strength related. The reduced compressive strength value may also be due to the fact that rice husk ash has less binding properties compared to cement.  After 28 days of water curing, the concrete gave an average optimum compressive strength value of 22.84N/mm2 corresponding to a mix proportion of 0.95, 0.05, 1, 2 (cement, rice husk ash, sand, granite) at a water-cement ratio of 0.4.This compressive strength value obtained at 5% replacement is within the recommended value required for plain concrete works, lean concrete, simple foundations, masonry walls and other simple construction works in low-cost housing constructions.

CHAPTER ONE

1.0 INTRODUCTION

1.1 Background to the Study

The high cost of building materials such as cement, has hindered most citizens of Nigeria from affording their own accommodation (Umoh and Ujene, 2013; Aho and Utsev, 2008). In Nigeria and specifically Niger state, there are a lot of natural building and construction materials, namely, laterite, sharp sand, stones, timber and bricks. Despite the availability of these construction materials, most citizens of Nigeria still find it difficult to afford their own shelters (Uwe, 2010). Most of the housing units in Nigeria are constructed using concrete which has Ordinary Portland Cement (OPC) as a basic component material (Anyaogu and Eze, 2013; Onwuka et al., 2013).

Cement is a scarce and costly building and construction material across the globe and the demand for it is growing on daily basis. There is therefore an urgent need to bring down the cost of cement by searching for alternative materials that can partially or fully replace the cement used in concrete and mortars, without affecting its strength, quality and/or other structural characteristics adversely. These materials will help the low income earners to afford their own houses most especially in the developing countries, such as, Nigeria (Coutinho, 2003).

Concrete is the most common and  versatile building and construction material in the world. According to Neville and Brooks (1990), concrete is a product of water, cement and aggregates which, when sufficiently hardened, is used to support various structural loads. The strength of concrete depends on the relative proportions of the component materials (Gambhir, 2004). Invariably, the total cost of concrete production is dependent on the availability and cost of its component materials. To reduce the cost of concrete materials and construction, efforts are being geared towards the use of abundant local building and construction materials either to totally or partially replace cement in concrete production. These materials are called pozzolanas. One of their major advantages in concrete is their slow hydration, which means low rate of heat development, which is very important in concrete production (Otoko and Chinwah, 1991). According to Kovacs (1975), good pozzolanic reaction reduces the porosity of the paste and therefore, improves impermeability of concrete.

The  present  study  on  the  use  of  Rice  Husk  Ash  (RHA)  as  a  pozzolan  in  concrete production is one of such efforts. The use of RHA as partial replacement of cement will reduce the cost of concrete and helps in the provision of low-cost houses for both the rural and urban dwellers. However, the maximum utilization of RHA in concrete production is limited due to lack of knowledge of the structural properties of RHA-cement concrete as well as the production techniques required.

This study is concerned with the application of Scheffe’s model in optimizing the compressive strength of concrete using rice husk ash (RHA) as partial replacement of cement. This will involve the formulation of mathematical models and the determination from the formulated mathematical models, the mix proportions that would predict and optimize the compressive strength of RHA-concrete. It is believed that research into the compressive strength of RHA-concrete will enhance its maximum utilization.

1.2 Statement of the Research Problem

Cement is the most important and expensive component of concrete. In Nigeria, the dependence on Portland cement for construction works is a source of concern. This is because cement plants are a significant source of sulphur dioxide, nitrogen dioxide and carbon monoxide and dioxide, which have adverse impacts on human health and  the environment. Major projects in Nigeria are sometimes, not completed due to the high cost of production. Although new cement factories are being built to increase the availability of cement, the demand for cement is still high. Consequently, concrete structures and houses needed to accommodate the growing population of Nigeria, are expensive to construct. Low income earners, therefore, find it difficult to afford shelters of their own. Thus, the partial replacement of cement with a pozzolan such as RHA has become a necessity in order  to  reduce  the  cost  of  construction  of  concrete  structures  and  houses,  without adversely affecting the quality and strength. Apata and Alhassan (2012) studied the use of local materials such as rice husk ash, calcined clay, lime and fly ash as partial replacements for cement in concrete. They reported that up to 10% replacement of cement with these local materials can be used for low cost housing construction. Habeeb and Fayyadh (2009) studied the effect of rice husk ash on the average particle size on properties of concrete. They found that low strength values were obtained at early ages, while at age 28 days, concrete containing finer rice husk ash attained higher strength than the concrete sample having coarser rice husk ash particles. Nair et al. (2006)   in their study on the use of rice husk ash as a replacement material to cement for rural housing, found that rice husk ash could be used to partially replace ordinary portland cement for rural housing.

1.3 Aim and Objectives of the Study

The aim of this study is to apply Scheffe’s model in the optimisation of compressive strength of concrete using rice husk ash (RHA) as partial replacement for cement.

The objectives are to:

(i)        Determine the physical properties of aggregates.

(ii)       Determine the compressive strength of RHA-cement concrete, when RHA is used as partial replacement and the optimum content of RHA in the mix.

(iii)      Formulate a mathematical model that will adequately predict the compressive strength of RHA-cement concrete.

1.4 Justification of the Study

This work would be beneficial to the society in the following ways:

(i)        The results of this research will form an important part of literature on the use of natural pozzolana as replacement of cement in materials for concrete production.

(ii)       The  results  of  the  compressive  strength  from  this  research  will  serve  as reference  materials  to  both  students  and  practicing  civil  and  structural engineers in design and construction of RHA-cement concrete mixes.

(iii)      The models developed will be used as design codes and standards for the determination of design mixes and proportions of RHA-cement concrete.

1.5 Scope of the Study

The scope of this study includes to determine:

i.         The physical properties of aggregates used for the laboratory experimentation.

ii.        The  compressive  strength  of  RHA-cement  concrete  at  zero  percent  (0%) replacement of cement with RHA. (Control specimen).

iii.         The compressive strength of RHA-cement concrete at varying percentages (%) of replacement of cement with RHA.

iv.        Formulate  a  mathematical  model  based  on  Scheffe’s  technique  to  predict  the compressive strength of RHA-cement concretes.

₦8,000.00 – DOWNLOAD FULL PROJECT DOWNLOAD FULL PROJECT Added to cart

---

---

---

---

Related Project Topics :