CHARACTERISTICS OF BURNT CLAY BRICKS CONTAINING POLYTHENE AND SAWDUST AS ADDITIVES

Abstract

Over the years excessive energy consumption is one of the major problems associated with burnt bricks production. This study assessed the characteristics of burnt bricks containing polythene and sawdust as additives. Trial test was prepared from standard mix obtained from literature. It was done for different percentages of additives (0%, 5%, 10%, 15%, and 20%) blend of sawdust and polythene. A total of 324 bricks samples were cast out of which 216 were used for dry and wet compressive strength. Specimen samples were fired at temperatures of 800⁰C-1300⁰C. The results obtained showed that the highest dry compressive strength obtained in the control samples fired at 1100⁰C with 15N/mm² and a minimum dry compressive strength of 12N/mm² when fired at 800⁰C. Specimen samples A containing 20% polythene fired at 1100⁰C had dry compressive strength of 13.1N/mm² and a minimum of 7N/mm² at 800⁰C. Samples E containing 20% sawdust fired at 1100⁰C had a dry compressive strength of 6N/mm² and a minimum of 4N/mm² at 800⁰C. It was observed that there was a decrease in compressive strength as the percentage of polythene decreases and sawdust increases. It further reveals that the control at temperatures of 800⁰C, 900⁰C and 1000⁰C exhibited low water absorption capacity of 11%, 11.6% and12.8% respectively, compared to the polythene and sawdust with 13%, 13.5% , 14% and 15%, 15.2 and 15.4% respectively. However both the control and samples containing additives showed 0.5% resistance to abrasion at firing temperatures of 800⁰C-1000⁰C. The research concluded that regarding the dry compressive strength, wet compressive strength and abrasion resistance, the samples met the minimum strength requirement specified by (IS: 1077) at temperatures of 800⁰C, 900⁰C, 1000⁰C and 1100⁰C considered and have good resistance to abrasion according to (Gupta and Gupta, 2004) hence are suitable for use in the construction of buildings as a walling material. It was also concluded that samples with additives are more stabilised before firing than the control, though higher strength was obtained in the control than the samples with additives and both met the specification by (IS 1077: (1992).The research recommends that bricks with polythene and sawdust are badly distorted at temperature of 1200⁰C which may be attributed to the internal heating contributed by the additives.

CHAPTER ONE

INTRODUCTION

1.1        Background to the Study

Clay is regarded as a kind of natural earth. When mixed with water it becomes plastic, mouldable and becomes hard again on drying and firing. Clay is a very fine grained, unconsolidated rock matter, which is plastic when wet, but becomes hard and stony when heated. It has its origin in natural processes, mostly complex weathering, transported and deposited by sedimentation within geological periods. It is composed of silica (SiO₂), Alumina (Al₂O₃) and water (H₂O) plus appreciable concentration of oxides of iron, alkali and alkaline earth, and contains groups of crystalline substances known as clay minerals such as quartz, feldspar and mica (Folaranmi, 2009).

According to Hendry and Khalaf (2001) clays used for brick making vary broadly in their composition and are dependent on the locality from which the soil originates. Different proportions of clays are composed mainly of silica, alumina, lime, iron, manganese, sulphur and phosphates. The principal properties of bricks that make them superior building units are their strength, fire resistance, durability, beauty and satisfactory bond and performance with mortar.

Additionally, Mamlouk and Zaniewski (2006) bricks do not cause indoor air quality problems. The thermal mass effect of brick masonry can be a useful component for fuel-saving, natural heating and cooling strategies such as solar heating and night-time cooling. They have moderate insulating properties, which make brick houses cooler in summer and warmer in winter, compared to houses built with other construction materials. Clay bricks are also non-combustible and poor conductors.

Environmentally friendly waste recycling has been one of the very important research fields for many decades. Mamlouk and Zaniewski (2006) established that a popular trend by researchers has been to incorporate wastes into fired clay bricks to assist the production of lightweight bricks. The utilisation of these wastes reduces the negative effects of their disposal. Many attempts have been made to incorporate waste in the production of bricks including rubber, limestone dust, wood sawdust, processed waste tea, fly ash, polystyrene and sludge. Researchers investigated on the potential use of uncontrolled burning rice husk ash to produce lightweight fired-clay brick and revealed that lightweight brick could be produced by increasing the RHA replacement. Though, the compressive strength of the brick was reduced (Danupon, T., Perapong, T., and Sarawut, J., 2008)

Wastes can be recycled by incorporating them into building materials and is a practical solution to pollution problem. The utilisation of wastes in clay bricks usually has positive effects on the properties, although the decrease in performance in certain aspects will also be observed. Vieira, C. M. F., Andrade, P. M., Maciel, G. S., Vernilli, Jr. F., and Monteiro, S. N., (2006) states that the positive effects of utilizing these wastes to the production of lightweight bricks with improved shrinkage, porosity, thermal properties and strength can be obtained by incorporating the recycled wastes. Most importantly, the high temperature in clay brick firing process allows volatilisation of dangerous components, changing the chemical characteristics of the materials, and incorporation of potentially toxic components through fixation in the vitreous phase of the waste utilised (Vieira et al., 2006).

Lightweight bricks are generally preferred because they are easier to handle and thus their transportation costs are lower. The development of lightweight bricks allows brick manufacturers to reduce the total clay content through the introduction of holes or incorporation of combustible organic waste particles that reduce the mass of the brick while maintaining the required properties. Moreover, lower energy consumption during firing from the contribution of the high calorific value provided by many types of waste has also been studied (Dondi, M., Marsigli, M., & Fabbri, B., 1997). Furthermore, Demir (2008) also utilised various organic residues such as sawdust, tobacco residues and grass from industrial and agricultural waste. These residue materials have long cellulose fibres. Differing amounts of waste were incorporated in the clay bricks – 0%, 2.5%, 5% and 10%. All samples were fired at 900°C while one batch was left unfired. According to Demir (2008), while maintaining acceptable mechanical properties, these wastes could act as an organic pore forming agent in clay bricks and increased the porosity, thus, improving the insulation properties. Adding organic residues increased the plasticity and, thus, increased the water content required. A residue addition of 10% is not suitable as the drying shrinkage increased excessively due to the effect of cellulose fibres. The dry strength of the brick increased but the compressive strength of the fired samples reduced by the addition of the residues. Kayali (2005), made bricks with 100% fly ash as the solid ingredient called FlashBricks. The equipment and techniques used in manufacturing the bricks were similar to those used in the clay brick industry. Samples were fired at 1000°C to 1300°C and were formed into moulds. Fired Flash Bricks produced bricks that were 28% lighter than standard clay bricks. In terms of appearance, the fired Flash Bricks have a reddish colour similar to a standard brick but a rougher texture was observed on the surface of the brick. In a similar study by Pimraksa, K., Wilhelm, M. and Wruss, W. (2001) bricks were also made using 100% lignite fly ash. The effect on the mechanical properties of four different treatments of fly ash: sieved -63+40 μm fly ash, sieved -40 μm fly ash, ground 5 hour fly ash and ground 10 hour fly ash were investigated. The optimal firing temperature was between 900°C to 950°C at 3°C/m for each type of the manufactured samples. Most samples tested demonstrated less than 4% of weight loss and less than 3% of shrinkage value. The results from the experimental work conducted demonstrated that bricks manufactured with -40 μm fly ash and fired at 950°C obtained better results in mechanical strength, specifically, in compressive strength (5.63 MPa) and bending strength (1.31 MPa) compared to red fired clay bricks, common clay bricks and facing bricks.

1.2 Statement of Research Problem

Recycled materials such as Sawdust and Polythene are wastes that are generated from either postconsumer or post-industrial (pre-consumer) sources. Rebecca (2013) in her research revealed that the bulk of waste generated in Nigeria constitute about 57% food waste, 13% plastic waste and 8% paper waste. These wastes amongst others contribute to degradation of our environment (Pappu, A., Saxena M., and Asolekar S. R., 2007). Clay is the most important raw material for burnt bricks. They acquire their strength and durability when they are heated to redness. Problems associated with high energy consumption in burnt bricks production and environmental degradation motivated researchers to work on alternative ways of solving this problems.

Quarrying operations for obtaining the clay are energy intensive, adversely affect the landscape, and generate high level of wastes. The high temperature kiln firing not only consumes significant amount of energy, but releases large quantity of greenhouse gases. Clay bricks, on average, have an embodied energy of approximately 2.0 kWh and release about 0.41 kg of carbon dioxide (CO₂) per brick (Alonso-Santurde, R., Coz, A., Viguri, J.R., Andres, A., 2012) and (Danupon, T., Perapong, T., and Sarawut, J., 2008) recommended that this problem can be reduced by addition of fuels to the clay such as sludge, polystyrene, sawdust, rice husk etc. High cost is involved in cleaning up waste from disposal sites and activities to do away with such waste which causes air pollution through burning fossil fuel, gas, coal, and oil amongst others and releases harmful gases such as carbon dioxide, carbon monoxide, nitrogen oxides, sulphur dioxide, and tiny solid particles into the atmosphere. These wastes must, in no way, present a threat to human health, to the air, to surface water and groundwater, or to the land. One possible means of safe disposal would consist of high-temperature incineration under rigidly controlled conditions. Effective utilisation of these wastes will likely help to reduce the negative effects of their disposal. However, in order to reduce these problems the potential wastes can only be recycled if the properties and the environmental pollutant of the new manufactured brick meet the specific requirements and comply with the relevant standards (Christine, 2004).

Rebecca (2013), highlighted that sustainable waste management is therefore critical in ensuring both the current and future generation have access to a clean and productive environment. It was stated that proper waste management structure such as recycling and collection of waste from the point source should be enacted to prevent further accumulation of solid waste. Also extensive waste management on how to recycle, reuse, reduce and respond to waste. Waste management is a challenge, but there are sustainable solutions to it.

1.3 Justification for the study

The use of burnt bricks in buildings is not very common as compared to concrete blocks despite the availability of clay used in its production. It is also common that certain additives are added to burnt brick raw mixes to produce different effects in the finished product. It is expected that the additives used in this research will serve as fuels which will provide more heating to the firing process thereby reducing the fuel and power consumption in burnt bricks production. It will also provide pores in the bricks which will allow the heat from the firing to quickly reach the innermost part of the bricks cores and as a result avoid unburnt core of the bricks

According to (Emmanuel A., 2008) the additives acts as a consolidating or fusing agent. It is also expected that the additives used in this research will help to increase the bonding of the particles and as such help to increase the strength of the bricks and also increase its resistance to abrasion. Introduction of this waste materials as additives will help to reduce the waste in the environment and reduce cost of purchasing clay for bricks. According to (Ayangade, J. A., Olusola, K. O., Ikpo, I. J. and Ata, O. 2004) cost of materials in construction account for two-third of the total construction cost.

1.4 Aim and Objectives

1.4.1    Aim

The aim of the research is to assess the combined effect of polythene and sawdust on the properties of burnt bricks with a view to establishing their suitability for use in burnt bricks production.

1.4.2    Objectives

1. To determine the physical and chemical properties of Bomo clay and sawdust ash.
2. To establish the mechanical properties of burnt bricks produced with additives (polythene and sawdust).

• To determine the durability properties of burnt bricks produced with additives (polythene and sawdust).

1.5 Scope and Limitations

1.5.1    Scope

This research is focused on assessing the properties of burnt bricks made with polythene and sawdust as additives by determining its wet and dry compressive strength, abrasion resistance, water absorption, exposure to sulphuric acid at 800⁰C, 900⁰C, 1000⁰C and exposure to elevated temperatures of 1100⁰C, 1200⁰C and 1300⁰C.

1.5.2    Limitations

In view of the wide range of properties of burnt bricks and the non-availability of some vital apparatus/equipment tests such as thermal insulation, thermal conductivity, tensile strength, refractoriness, shrinkage and porosity were not assessed.

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