ABSTRACT
Waste materials utilization is one of the central concerns of waste management approaches in recent years. The developments in cement and concrete technology towards the production of sustainable concrete by using waste materials and cellulosic fibre is gradually attaining acceptance because of its technological, economic and ecological advantages. This research investigated the potential use of a natural fibre known as Kenaf fibre and Rice Husk Ash (RHA) from agricultural waste towards achieving a bio fibrous concrete with enhanced impact resistance and strength properties. Four mixes with varying percentage of RHA from 0% to 15% at an interval of 5% without fibre was used as a basis for comparison against another four mixes made with 50 mm length fibre of 0.5% volume fraction and RHA of 0% to 15% as supplementary cementing material. The drop weight impact test method was adopted in determination of the impact resistance strength and energy absorption of the RHA based kenaf fibrous concrete. It was found that the addition of Kenaf fibre decreased the slump values and increased the VeBe time of fresh concrete. Also, the inclusion of RHA at varying percentage had a reducing effect on the workability of both the fibreless and the fibrous concrete. At later ages, the compressive strength of the fibrous concrete mixtures containing RHA significantly increased and the obtained values were higher than the mix with OPC alone. The positive interaction between Kenaf fibres and RHA leads to high tensile strength, flexural strengths and impact resistance, thereby increasing the concrete ductility with higher energy absorption and improved crack distribution. The study established that Kenaf Fibre (KF) at 5% and 10% Rice Husk Ash (RHA) resulted in; 12%, 26.3%, 30.8% and 3.9% in compressive strength, splitting tensile strength, flexural strength and energy absorption values respectively compared to the control. It is concluded that Kenaf fibre and rice husk ash can be used as building materials in the construction of sustainable concrete.
CHAPTER ONE
1.0 INTRODUCTION
1.1 Background to the Study
Concrete with its low durability and rigidity has been subsumed as a brittle and frail material (Ogunbode et al., 2016). Therefore, the urgent commitment of a greater energy absorption and impact defiance is required in various applications like deck of bridges, industrial floors, highway paving etc. Enhancing the properties of concrete can be achieved by further incorporation of some additional components. (Hsie et al., 2008; Ogunbode et al., 2016). Fibre reinforced concrete (FRC) is a composite material made of Portland cement (PC), coarse and fine aggregates, and a dispersion of discontinuous short fibres. Natural fibres, Polymeric fibres (polypropylene, nylon etc), glass fibres, metallic fibres, and fibres from consumer waste have emerged as common fibres employed in FRC (Babafemi & Boshoff 2015). As the introduction of FRC in the construction industry emerged, a great deal of challenges has been encountered during the evaluation of the real properties and advantages of different types of fibres. Over time, natural fibres of different kinds have been outstanding and applied in concrete mixtures. Kenaf fibres with volume fractions ranging from 0.5% to 1.0% has been frequently used as a supplementary reinforcement in concrete and have reported an enhanced tensile strength (Lam & Jamaludin, 2015; Ogunbode et al., 2018). But there is a dearth of literature on its effect on energy digestion and impact defiance of concrete.
Ordinarily, incorporating various types of fibres in concretes can enhance its ductility. Tejchman et al., 2010; Arango, 2012 also worked on exploiting the importance of a system that fights against the development of cracks as well as enhancing how much work the concrete matrix can take. Quite a number of studies have been done to examine how ductile FRC can be by the impact test, and results have shown that when fibres are added, the impact defiance of this mixture is improved. (Razavi, 2017). Fibrous concrete containing pozzolanic materials have been previously fabricated and studied with conventional concrete (Hossein, 2016). In recent decades, detection and recognition of pozzolanic ashes as supplementary cementious materials (SCMs) used in concrete rapidly increased for practice in research and concrete industries. One of the inclusions in the ash family is RHA, which is obtained by burning rice husks deposited as waste from rice mills. This waste ash is usually available in African Sub-Sahara and South-East Asia regions where production of rice plays a significant role in the national economy. This study seeks to experimentally find out the combined effect of kenaf fibre and RHA in enhancing the impact resistance and strength of concrete.
1.2 Statement of the Research Problem
Despite several approaches, waste materials utilization has become an emerging interest for waste management. The advancements concrete and cement technology has taken towards the production of sustainable concrete by using waste materials and cellulosic fibres is gradually attaining acceptance due to the advantages it possesses in the ecological, technological and economic advantages. In the past years, some fibres (glass, carbon, steel fibres etc.) are frequently being used for strengthening of RC structures due to their mechanical properties (i.e. high modulus of elasticity, relative low extension coefficient, and corrosion resistance). However, these materials are expensive in terms of costs and material production. Besides, they are also not biodegradable materials. Kenaf fibres have considerably received attention to be used in different applications. This acceptance is due to its being environmentally friendly and its desirable characteristics such as a great and excellent stiffness and strength in particular.
Over the past decades, researches on the impact and clot of kenaf fibres on concrete and concluded that kenaf fibres curtails the compressing force and workability of concrete. However, kenaf fibres have demonstrated a positive reaction with respect to its toughness coupled with its strength (Lam & Jamaludin, 2015; Ogunbode et al. 2016).
The study of Nagrale et al. (2012) reported that addition of 15% RHA influences the density of concrete by reducing the weight concrete to about 72-75%. Hence, an effective use of RHA concrete is in the production of concrete with low weight where they can be applied in building up of structures where the weight is very significant. Nagrale et al. (2012) further explained the incorporation of RHA with results showing an increase in strength of concrete with a reduction in how much water the concrete absorbs. Therefore, with the presence of RHA in concrete, it can be used in areas where concrete can get in touch with water. In addition, with a significant increase in strength, pozzolanic properties and workability of membranes, RHA offers the possibility act as an admixture. Habeeb & Mahmud (2010) described the impact RHA has on the resilience characteristics of concrete to be significant. Results showed that the extensive strength of composite concrete with 10% RHA was substantially improved. They also reported that having about 20% of cement with RHA produced a valuable strength with no negative impact on concrete strength.
A recent notion of study that requires a comprehensive review is in the combined effect of RHA and kenaf fibres on the characteristics of concrete. With little research being done on the utilization of these fibres in enhancing concrete performance, conducting a detailed study on concrete having a broad range of mixing ratio is very vital. Considering the fact that a small amount of short fibres has been considered in improving the properties of concrete, this makes it easier to utilize kenaf fibres in order to achieve a greater defiance effect of concrete with fires in them.
This study seeks to investigate the potential use of a natural fibre known as Kenaf fibre and Rice Husk Ash (RHA) from agricultural waste towards achieving a bio fibrous concrete with enhanced impact resistance and strength properties.
1.3 Aim and Objectives of Research
This research aims to study the influence of Rice Husk Ash (RHA) on the impact resistance of Kenaf Fibrous Concrete (KFC) with a view of producing a concrete with enhanced ductility and ability to withstand impact load. The specific objectives of this work are to:
i. Determine the physiochemical properties of the constituent materials.
ii. Evaluate the influence of RHA on the fresh properties of KFC.
iii. Determine the effects of RHA content on compressive, tensile and flexural strength properties of KFC.
iv. Assess the influence of RHA content on the impact resistance of the KFC.
1.4 Scope and Limitation of Study
This work would be tested and experimented in nature and majorly focus on applying developed KFC composite containing RHA at replacement levels of 0 to 15% at 5% step intervals of Portland Cement (PC) and kenaf fibre at fibre length and content is 50 mm and 0.5% respectively. Kenaf fibre was used as an addition while RHA was used as supplementary cementing material. Therefore, an essential number of investigations and analysis were performed. This study emphasizes on the properties of concrete (mechanical and physical) considered to be within specified limits set by the objectives.
The kenaf fibre used in the study is Nigeria based and obtained from manchock local government area in Kaduna State to be precise. In order to removed pectin, cellulose and lignin, the fibres were treated with Sodium Hydroxide (NaOH). The RHA was initially acquired in the husk state and then burnt to ash form in a locally fabricated incinerator. The study emphasizes on the impact resistance of the composite using drop weight impact test methods. KFC specimen testing for impact resistance was conducted on standard size specimens. 100 mm x 100 mm x 500 mm prism were in use while undergoing the drop weight impact test as given in the work of Razavi (2017). The focal variables considered are the effect of RHA inclusion in 0.5% KFC (0% to 15% at 5% interval) and Height of Drop weight (500 mm and 1000 mm) on concrete sample. The specimens had been tried at hydration days (7, 28 and 56) respectively.
1.5 Justification for the Study
Elimination of the huge amounts of agricultural waste and synthetic waste materials generated in our environment has been a very difficult task to achieve in the past years. Nevertheless, the environmental defects can be reduced by providing more sustainable usage of these waste materials. This is known as the Waste Hierarchy’’. Its objective is to reduce, recycle, or reuse waste, the latter being the desired option of waste disposal as illustrated.
Since short discontinues fibres has been proposed for the development of the concrete performance, the use of kenaf fibres will result in a reduction of the amount of synthetic fibre used which is generated from petroleum product. This will help to reduce the generation of CO2 that have relative effect on the ozone layer of the earth leading to global warming. Promoting the use of kenaf fibre as a fibre material in fibrous concrete production will increase the plantation of kenaf plant which contributes to our environment by reducing the CO2 in the atmosphere and achieving a cleaner environment. The change aimed in achieving a renewable and long-term improvement due to the effects of strains placed on reducing CO2 and greenhouse gases which gives an increase in the demand in the fibre market. Switching into a renewable and biological inclined system demands alternating certain resources (Plant or animal based) materials.
On ecological grounds products should then be preferred that are based on photosynthetic CO2 fixation. The benefit of those sustainable resources is that they can be regrown within the foreseeable future, without negative side-effects on global bio-diversity. Therefore, competitive products based on renewable resources need to be developed that have high quality, show excellent technical performance and harm the environment less than current products based on petrochemical materials (van Dam, 2009).
The inclusion of kenaf fibre and replacing Portland cement with RHA helps to enhance the brittleness properties of concrete. Appropriate use of SHA in the concrete product will significantly develop the mechanical properties of concrete which will in turn decrease the pressure on the industrial and domestic consumption of Portland cement. As both SHA and kenaf fibre are from agricultural source requiring minimal spending, their use will considerably decrease the overall cost of construction, thereby justifying the name of “Green Concrete Composite”. Consequently, the mixture of SHA and Kenaf fibre to produce concrete composite will open up new research opportunities.
This material content is developed to serve as a GUIDE for students to conduct academic research
ASSESSMENT OF THE IMPACT RESISTANCE BEHAVIOUR OF RHA BASED KENAF FIBROUS CONCRETE
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