EVALUATION OF THE MECHANICAL PROPERTIES OF KENAF BIO FIBROUS CONCRETE COMPOSITES CONTAINING SORGHUM HUSK ASH

ABSTRACT

Fibrous Concrete Composite (FCC) is a high performance concrete that possesses an improved tensile strength and ductility under sustained load compared to Plain Concrete (PC). As a result of global search for sustainable, renewable and green materials to achieve a bio based economy and low carbon foot print environment, the use of fibre to produce fibrous concrete composite has continuously received significant research attention. Due to the growth amount of waste generation from agricultural product, there has been a developing interest in the utilization of waste in producing building materials to achieve potential benefits. This research evaluate the mechanical properties of kenaf bio fibrous concrete composites (KBFCC) containing sorghum husk ash (SHA) as partial replacement of Ordinary Portland Cement (OPC). Five volume fractions of kenaf fibre (KF) varying from 0% to 1.0% at an interval of 0.25% with a uniform length of 50mm was used with OPC concrete mixes. Another five mixes were made that replaced OPC with 10% SHA. Fresh properties of these mixes to evaluate the workability were measured using slump test, VeBe  test,  compacting  factor  test  and  fresh  density  test.  It  was  observed  that  the combination of kenaf fibre and SHA decrease the slump values and increase the VeBe time of fresh concrete, the slump value of PC and the mix containing SHA were 160mm and 140mm respectively, also the mix containing fibre volume of 1% of OPC and one with SHA and fibre volume of 1% were 40mm and 25mm respectively. For the compacting factor and fresh density tests, it was observed that, as the fibre content increases there was decrease in both the compacting factor test and fresh density test. The decrease in fresh density and compacting factor was due to the density of the fibre (1200kg/m3) and the lower specific gravity of SHA (2.32) to that of OPC (3.15). The addition of kenaf fibre to either OPC or SHA concrete mixes showed a positive interaction that led to high tensile and flexural strengths, thereby increasing the concrete ductility with higher energy absorption and improved crack distribution. The maximum increases in tensile and flexural strengths compared to those of plain concrete were achieved by the addition of 0.5% kenaf fibre at the age of 56 days for the mix with OPC alone and with the mix that has SHA which are 5.35N/mm2,6.55N/mm2  and 5.15N/mm2, 5.90N/mm2 respectively. For effective waste management, use of agro waste materials such as SHA and agricultural plant such as KF can be effectively put to use in the production of a sustainable concrete material and thus provide optimum economic benefit. It is recommended that SHA and KF should be incorporated into concrete mixes aimed at improving the splitting and flexural strength of concrete. The study showed that the use of KF and SHA in the production of sustainable green concrete is technical and environmentally achievable.

CHAPTER ONE

1.0       INTRODUCTION

1.1       Background to the Study

Concrete is a construction substance consist mainly of cement, coarse aggregates, smooth aggregates, as well as water in a fixed ratio. Concrete’s utility in a variety of construction and structural engineering uses is undeniable. Offshore structures, shotcrete, Hydraulic structures, foundations in earthquake environments, graded slabs, thin/dense replacements, architectural panels, broken walls, precast materials, footings, worldwide transport infrastructural networks such as highway network, bridges, trains, airports, canals, and many other applications have all benefited from it over the years. The advantage of having the lowest quotient between the strength and the cost as compared to other usable products is not far-fetched from the cause for its general acceptance for use in various infrastructure productions. (Tejchman and Kozicki, 2010; Yatim et al., 2011; Bicanic et al., 2014).

Fibre reinforced concrete is a form of concrete that contains fibrous materials that are spread and oriented uniformly within the concrete matrix. The concept “fibre reinforced concrete” (FRC) was described by ACI 544 (1999) as “a concrete made of hydraulic cements comprising fine or fine and coarse aggregates and discontinuous distinct fibres.” Synthetic fibres,  steel  fibres,  natural  fibres,  and  glass  fibres  are also  widely found in concrete. After the introduction of fibre reinforced concrete, different research has been done on a variety of fibre materials to ascertain the true characteristics and benefits of the component. (Ogunbode et al., 2016). For many, the high price rate of cement poses a significant  barrier  to  sustainable  housing.  The  government  of  Nigeria  has  initiated  a mortgage repayment program in order to provide 10,000 homes for its citizens. (Andrews and Jonathan, 2014).  Polozzonic materials are used to replace a portion of the cement in concrete made from agro wastes such as corncob ash, rice husk ash, sorghum husk ash, and palm kernel fuel ash, which are all inexpensive and readily available.

Pozzolanas are “siliceous or siliceous and aluminous materials that have little or no cementitious properties in themselves, but when finely divided and in the presence of moisture, they can react with calcium hydroxide (CaOH) liberated during the hydration of OPC at ordinary temperatures to form compounds with cementitious properties.” (ASTM C 618, 1981). Pozzolanas are “siliceous or siliceous and aluminous materials that have little to no cementitious properties in themselves, but when finely separated and in the presence of moisture, they can react with calcium hydroxide (CaOH) liberated during the hydration of OPC at ordinary temperatures to form compounds with cementitious properties.”

High production cost per ton of capital relative to cement, low cost promotion of waste disposal,  decreased  emissions  by  these  wastes,  and  expanded   famers’  commercial foundation when the said waste is sold, thus promoting further production are some of the advantages to be benefited by the utilization of agro waste in the part  substitution of cement. (Mahmoud et al., 2012).

One of the building industry’s focuses has been on recycling, like the use of renewable biodegradable fibre and the use of industrial waste as a partial replacement for cement in concrete. (Ogunbode et al., 2016), This is as a result of current worldwide challenge of carbon footprint or the effect of greenhouse due to the introduction of excess CO2 into the air during the processing of cement and synthetic materials. This is due to the moment worldwide difficulty of carbon footprint or greenhouse effect due to the release of excess CO2 into the atmosphere during the production of cement and synthetic materials (Olutoge et al., 2010; Nattapong et al., 2011; Rubenstein, 2012). In the last few years, research has been  carried  out  to  enhance  the  method  of  using  fibre  insulation  to  improve  the performance of concrete sections of buildings. The majority of these projects, however, have focused on steel fibre and non-renewable resources (Abdul et al., 2015; Sarangi and Sinha, 2016).  Both developing and developed countries are increasing their adoption and use of bio fibres in the building industry. Bio-degradable products, such as kenaf bio fibrous concrete, are becoming more common. (Ogunbode et al., 2016).

1.2       Statement of the Research Problem

The growth in global population and income in the twenty-first century has increased the need for sustainable materials. These requirements occur as a result of landfills piling up due to massive depositions of accumulated garbage, the earth’s environment shifting as a result of CO2 emissions into the air during the production of new products and cement, and natural resources becoming extinct. (Olutoge et al., 2010; Nattapong et al., 2011).

Concrete’s shortcomings, such as its low energy absorption and poor tensile strength, cause initial cracks and failure. (Ogunbode et al., 2016). These cracks in the concrete’s surface provide a pathway for harmful species such as sulphates, moisture, chloride, and carbon dioxide to enter the concrete, causing the reinforcement to corrode and compromise the structure’s durability. The two aforementioned problems, namely CO2  emissions into the atmosphere during cement processing and poor tensile and energy absorption of concrete, necessitate the conduct of this study.

1.3       Aim and Objectives of the Study

The purpose of this study is to look into the mechanical properties of kenaf bio fibrous concrete composites incorporated with SHA in order to create a sustainable green concrete that is both technically and environmentally viable.

The following objectives were established in order to accomplish the above goal, to:

i            Determine the effects of fibre volume fractions  on the fresh characteristics of KBFCC containing SHA.

ii          Evaluate the influence of varying fibre volumes fractions on strength properties of SHA based Nigeria kenaf bio fibrous concrete.

iii          Investigate the relationships between compressive strength, tensile strength and flexural strength of Nigeria based kenaf bio fibrous concrete containing SHA.

1.4       Scope of the Study

The focus of the study is on the kenaf bio fibrous concrete composites with sorghum husk ash  mechanical  properties  as  a  partial  substitute  for  cement  (compressive  strength, separating flexural strength, and tensile strength). The thickness of the kenaf fiber geometry used in the study was 50 mm. The fibres used in the research were alkaline-treated kenaf fibre. The fibers were included at volume fractions of 0 per cent, 0.25 per cent, 0.5 per cent, 0.75 per cent, and 1 per cent. The amount of cement  level substitution by weight of sorghum husk ash was 10%. Within 24 hours, many of the specimens included in this analysis were cast and demoulded. The mechanical properties research specimens were being cure in water for 7, 28, and 56 days.

1.5       Justification for the Study

Sorghum husk is a kind of agricultural waste that is abundant in Nigeria. Sorghum husk ash is a by-product of sorghum husk combustion which is not adequately disposed of, it would have a detrimental impact on the atmosphere and human health (Ogunbode et al., 2017). The amount of agro waste that is dumped into the landfills can be minimized by using SHA. Furthermore, by substituting SHA for cement and using kenaf fibre, contamination caused by carbon dioxide emissions from cement processing can be minimized. The formation of cracks is a big issue with concrete. As a result, a significant solution to reduce concrete brittleness is needed. In relation to the topic at hand, Toutanji (1999); Sun et al., (2001) reported that fibre reinforced cementitious composites can fix concrete brittleness.

Also, Beigi et al. (2013); Medina et al. (2014) stated that ductile material with pozzolanic mixture demonstrated remarkable ductility when passed through mechanical loading so also is the resilience under various environmental exposures, according to the report. The consequences of this research are important, particularly considering the recent trend of fibre reinforced concrete being a common building medium and the fact that environmental problems influence everybody in society. The need for this research work arises as a result of its positive impact on academics, who will contribute to researchers’ knowledge, the construction industry, which will produce high-performance structures, and the economy, which will benefit from the use of waste to create wealth.

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