CHAPTER ONE
1.0 INTRODUCTION
1.1 GENERAL BACKGROUND TO THE STUDY
The effect of bamboo leaf ash blended with cement on the engineering properties of lateritic has been investigated so as to establish the optimum bamboo leaf ash content suitable for stabilizing lateritic block for building construction. Since these materials are readily in abundance, it is expected to impact positively on the building industry in Nigeria (Guardian Online News, 2010). The current housing deficit is put at about 16 million housing units nationwide and this must be brought to acceptable international standard of one housing unit per one household. This requires the professional participation and the use of local materials to subsidize the exorbitant cost of building materials. The poor state of infrastructure development in Nigeria has been held responsible for our slow pace of progress in all areas of human endeavours. Hence, there is a need for the execution of local capable construction materials in order to upgrade the infrastructure development of the country. There have been a good number of research works to attain this specific goal and government is trying all her best to ascertain that such is realistic. It is not just owing a housing unit but one that will meet up with standard construction techniques, buildability and maintainability standard and ultimate design limit state. In addition, a housing unit that will provide a maximum comfort for the occupants or users. The prevailing economic disaster has prompted the need for m1ore than ever for man to explore the available resources around him. Also the high cost of building materials, especially cement has aided the exploration of the building industries. In Nigeria for instance, efforts have been made on exploration of building materials and even shortage of building materials and escalating prices of those available are responsible for the current acute shortfall in the provision of adequate housing unit both in urban and rural areas.
Hydraulic lime (HL) is a general term for varieties of lime (calcium oxide), or slaked lime (calcium hydroxide), used to make lime mortar which set through hydration: thus they are called hydraulic. The other common types of lime mortar Maloney, (2010) set through carbonation (re-absorbing carbon dioxide (CO2) from the air) and are sometimes called air lime. Hydraulic lime provides a faster initial set and higher compressive strength than air lime and eminently hydraulic lime will set in more extreme conditions including under water. Calcium reacts in the lime kiln with the clay minerals to produce silicates that enable some of the lime to set through hydration; any unreacted calcium is slaked to calcium hydroxide which sets through carbonation: These are sometimes called semi-hydraulic lime and include feebly and moderately hydraulic lime, NHL 2 and NHL 3.5. The terms hydraulic lime and hydrated lime are quite similar and may be confused but are not necessarily the same material: hydrated lime is any lime which has been slaked whether it sets through hydration, carbonation, or both (Haygreen, et. al. 1989).
The utilization of raw materials (local) is one method of reducing the cost of production (construction). The international symposium for industrial development held in Athens in 1967 recommended that developing countries should where necessary give higher priority to the development of building materials in order to achieve greater efficiency in their construction activities, better utilization of local materials resources and saving in foreign currency. The high cost of building materials has been observed to be the major factor besetting housing delivery in Nigeria (Okoli, 1998). This has been partly traced to the rising cost of cement; which is commonly used in the production of sandcrete blocks, concrete and as stabilizing admixture in soil blocks. In addition, there are also issues arising from the production processes of cement which ranges from huge energy consumption to large emission of CO2; a major greenhouse gas. Hence, for a nation which is faced with what can be described as an unprecedented energy crisis and with the global campaign against the emission of greenhouse gasses to curb warming of the environment, it is only appropriate to seek alternative means to the use of cement in the effort to achieving the goal of housing delivery (Frais M. et al, 2012). All over the world, Pozzolans have been discovered to be viable alternative binder to cement, especially in the realm of partial replacement. Pozzolans are fine silica and alumina rich materials which when mixed with hydrated lime produce cementitious materials suitable for stabilization and construction needs. Recently, it was reported that bamboo leaf ash is an equally good pozzolanic material which reacts with calcium hydroxide to release additional calcium silicate hydrate (C-S-H); the main cementitious component (Dwivedi et al. 2006, Singh et al. 2007, Frias et al. 2012).
Concrete is one of the most widely used construction material worldwide and there is an increase in the production of concrete to meet the ever-increasing demand for housing and other infrastructure. Cement, which is the main binder in the production of concrete, mortar, sandcrete blocks and other cement products, is very expensive particularly in developing countries (Samuel Awoyinfa, 2013). The exorbitant and steadily increasing cost of cement has made concrete, mortar, sandcrete blocks and other cement products expensive and consequently increasing the cost of construction of houses and other infrastructure that uses cement.
Yusoff et al. (1992) studied the chemical composition of one, two and three year old bamboo (Gigantochloa scortechinii). The carbohydrate content of bamboo plays an important role in its durability and service life. Durability of bamboo against mould, fungal and borers’ attacks is strongly associated with its chemical composition. Furthermore, the ash content of bamboo is also made up of inorganic minerals, primarily silica, calcium and potassium. Manganese and magnesium are two other common minerals. Silica content is the highest in the epidermis, with very little in the nodes. Reactions of this ash (heated at moderately high temperatures) with calcium hydroxide are known to be pozzolanic in nature. The mechanism for this display of strength is the reaction of silicates with lime to form secondary cementitious phases (calcium silicate hydrates with a lower Ca/Si ratio) which display gradual strengthening properties usually after 7 days.
Dwivedi et al. (2006) reported the reaction between calcium hydroxide (CaOH) and bamboo leaf ash for 4 hours of reaction, using the differential scanning calorimetry (DSC) technique, while Singh et al. (2007) studied the hydration of bamboo leaf ash in blended Portland cement. Bamboo leaf ashes were obtained in a laboratory electric furnace at 600°C calcining temperature for 2 hours of retention. Once calcined, the ashes were ground and sieved below 90 µm, fineness similar to that of Portland cement. The ash showed grey colour. These studies concluded that bamboo leaf ash is an effective pozzolanic material. When 20% weight of bamboo leaf ash was mixed with OPC, the compressive strength values of mortars at 28 days of hydration were found to be quite comparable to those of OPC.
Ernesto et al. (2007) discussed the characterization and studied the pozzolanic behavior between calcium hydroxide (CaOH) and bamboo leaf ash (BLA) obtained by calcining bamboo leaves. Based on the chemical composition, morphology and XRD pattern test on bamboo leaf ash, they concluded that this kind of ash is formed by silica with a completely amorphous nature and a high pozzolanic activity. Sabir et al. (1998) measured the uni-directional water absorption of mortar and concrete. They tested the sorptivity of various mortars, found out the variation in sorptivity with curing period and investigated the compressive strength. McCarter et al. (1996) studied the absorption of water and chloride ion penetration into concrete and found that sorptivity is to be minimized to bring down problems due to either chloride ion penetration or sulphate attack on concrete. Bai et al. (2002) found from their studies that addition of fly ash increases sorptivity, whereas addition of silica fume reduces sorptivity. Therefore, bamboo leaf ash a local occurring material has attracted interest in many circles as a cheap source of pozzolanic cementic material for the production of larger construction that can be used in construction. Hence, the use of pozzolan as a cementic material for building processes cannot be over-emphasized.
1.2 STATEMENT OF THE PROBLEM OF THE STUDY
Durability of concrete is of great concern in the construction. The availability of cement in the construction industry has been observed to be the most binding agent and materials been used within the construction industry. Since the inception of this material, some material has been discovered to replace the cement, such materials are bamboo leaf ash and hydraulic lime.
The recent increase in the price of building materials which lead to high cost of construction. It has been observed that high cost of cement is considered as one major factor of increase in cement which has been a major problem since there is no alternative for binding agent. Setting time are been considered to be moderate and other type of cement which brings about idea of using hydraulic lime and bamboo leaf ash.
Effectively, collaborative use of adequate nature of cement materials has been considered as a way to provide an alternative means for effective binding within the construction industry and where as local materials like bamboo leaves are being wasted. Pozzolan being readily available and cheaper will eventually bring a lot of cost savings.
1.3 RESEARCH QUESTIONS
i. Is bamboo leaf ash appropriate as replacement for pozzolanic material?
ii. Does bamboo leaf ash have the properties (chemical and physical) that make it conventionally appropriate for construction work?
iii. Does bamboo leaf ash relative property content adequate stability and ultimate strength required for construction
1.4 AIMS AND OBJECTIVES
The aim of this study is to investigation bamboo leaf ash as a pozzolanic material.
The objectives of this study are:
i. To assess the compressive strengths of different percentages of bamboo leaves and hydraulic lime as a pozzolanic material.
ii. To determine the workability of bamboo leaves and hydraulic lime as a pozzolanic material.
iii. To determine the setting time of bamboo leaves and hydraulic lime as a pozzolanic material.
1.5 SIGNIFICANCE OF THE STUDY
Durability of concrete is of great concern in the construction. Hence, this is concerned with investigation of bamboo leaf ash as a pozzolanic material on compressive strength of concrete. The recent increase in the price of building materials which lead to high cost of construction, also the population increase in urban area like Ibadan (Oyo state ), Lagos (Lagos state), Port –Harcourt (River state), Abuja (FCT), etc; have created a lot of housing problem, where as local materials like bamboo leaves are being wasted. Pozzolan being readily available and cheaper will eventually bring a lot of cost savings.
1.6 SCOPE OF THE STUDY
This research work cover the production of pozzolan cement from bamboo leaves and hydraulic lime and tested to determine the strength, workability and setting time.
1.7 METHODOLGY
This project is experimental based project.
Materials: Hydraulic lime
Bamboo leaf ash
Cement
Sand
Gravel
Test: Compressive strength
Workability
Setting time
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