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CHAPTER 1 INTRODUCTION
1.1
GENERAL The constant developmental activities in civil engineering and
growing industrial activities have created a continuous demand for building materials which satisfy all the stringent requirements regarding the short-term and long-term performance of the structure. As the structures of tomorrow become taller and more complex, the materials of construction will be required to meet more demanding standards of performance than those in force today (Fuller 2006). India’s present housing shortage is estimated to be as high as 31 million according to census and out of these shortages 24 million units are in rural areas and 7 million units in urban areas. Such a large housing construction activities require a huge amount of money. Out of this total cost of housing construction, building materials contribute to about 70% of cost in developing countries like India. The increase in the popularity of using environmental friendly, low-cost and light weight construction materials in building industry has brought about the need to investigate how this can be achieved by benefiting the environment as well as maintaining the material requirements affirmed in the standards (Turgut Paki and Algin Halil Murat 2007).
2 In the construction industry, building technology is heading towards an entirely new era because of the usage of industrial wastes in various forms of building material production. For instance, the use of waste rubber, glass powder, industrial waste fibres, wood sawdust wastes and limestone powder wastes in building material production has received diligent attention over the past few years. This is quite understandable because it is slowly but increasingly being recognized that the economic progress in construction depends more on an intelligent use of materials and constant improvement of available materials.
1.2
INNOVATION OF PAPERCRETE Papercrete is a material originally developed 80 years ago but it is
only recently rediscovered. Papercrete is a fibrous cementitious compound comprising waste paper and Portland cement. These two components are blended with water to create a paper cement pulp, which can then be poured into a mould, allowed to dry and be utilized as a durable building material. It should be noted that papercrete is a relatively new concept with limited scope. Papercrete has three derivatives, namely fibrous concrete, padobe and fidobe. The fibrous concrete is a mixture of paper, Portland cement and water. There are no harmful by-products or excessive energy use in the production of papercrete. Padobe has no Portland cement. It is a mix of paper, water and earth with clay. Here clay is the binding material. Instead of using the cement, earth is used in this type of brick. This earth should have clay content of more than 30%. With regular brick, if the clay content is too high the brick may crack while drying, but adding paper fiber to the earth mix strengthens the drying block. It gives flexibility which helps to prevent cracking. Fidobe is like padobe, but it may contain other fibrous material.
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1.3
BRIEF HISTORY OF BRICKS All over the world, bricks are the most widely used construction
materials for the construction of buildings. The bricks are obtained by moulding clay in rectangular blocks of uniform size and then by drying and burning the blocks. As the bricks are of uniform size, they can be properly arranged. The common brick is one of the oldest building materials and it is extensively used at present as a leading material in construction. In India, the process of brick making has not changed since many centuries except in some minor refinements. There has been hardly any effort in our country to improve the brick-making process for enhancing the quality of bricks. Also the structures in view of their compressive strength, structural stability and relative low cost have not undergone any drastic change. But it has two major drawbacks, namely self weight and brittleness. 1.4
PAPER Paper is a natural polymer which consists of wood cellulose, which
is the most abundant organic compound in the planet. Cellulose is made of units of monomer glucose (polysaccharide). The links in the cellulose chain are a type of sugar as ß-D-glucose. Despite containing several hydroxyl groups, cellulose is water insoluble. The reason is the stiffness of the chains and hydrogen bonding between two OH groups on adjacent chains. The chains pack regularly in places to form hard, stable crystalline regions that give the bundled chains even more stability and strength. This hydrogen bonding is the basis of papercrete’s strength. By applying a force on the paper the hydrogen bond between the water and the cellulose molecule is broken. Coating cellulose fibers with Portland cement creates a cement matrix, which encases the fibers for extra strength to the mix. Cellulose hydrogen bonds are shown in Figure 1.1.
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Figure 1.1 Cellulose hydrogen bonds in paper The links in the cellulose chain are a type of sugar: ß-D-glucose. The cellulose chain bristles with polar -OH groups. These groups form many hydrogen bonds with OH groups on adjacent chains, bundling the chains together. Viewed under a microscope, it is possible to see a network of cellulose fibers and smaller offshoots from the fibers called fibrils.
Figure 1.2 Fibrils are offshoots of fibers
Figure 1.3 Fibrils network
Figure 1.2 and 1.3 show fibers and fibrils network to form a matrix, which becomes coated with Portland cement. When these networks or matrices of fibers and fibrils dry, they intertwine and cling together with the power of the hydrogen bond. 1.5
FLYASH Flyash is a by-product of the combustion coal in the thermal plants.
It is removed by the dust collection system as fine particle residue from the combustion gases before they are discharged into atmosphere.
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Depending upon the collection system, varying from mechanical to electrical precipitators or bag houses and fabric filters, about 85% to 90% of the ash from the flue gases is retrieved in the form of flyash. Flyash accounts for 76% to 8 % of the total coal ash and the remainder is collected as bottom ash or boiler slag. The bottom ash and boiler slag are much coarser and are not pozzolanic in nature. It is thus important to recognize that all the ash is not flyash and the flyash produced by different power plants is not equally pozzolanic. Testing shows that the bricks meet or exceed the performance standards listed in ASTM C 216 for conventional clay brick. It is also within the allowable shrinkage limits for concrete brick in ASTM C 55, and standard specification for Concrete Building Brick. It is estimated that the production method used in fly ash bricks will reduce the embodied energy of masonry construction by upto 90% (Chusid et al 2009). 1.6
CURRENT RESEARCH TRENDS In the last decade, a large demand has been placed on building
material industry especially owing to the increasing population which causes a chronic shortage of building materials. As a result, civil engineers have been challenged to convert the industrial wastes into useful building and construction materials. Accumulation of unmanaged waste especially in developing countries has resulted in an increased environmental concern. Recycling of such wastes into building materials appears to be viable solution not only to such pollution problems but also to the problem of economic design of buildings. The current pool of knowledge pertaining to papercrete was obtained predominately through many anecdotal field experiments and
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observations. Yet very little by way of peer reviewed research exists in regard to this material. 1.7
OBJECTIVES OF THE STUDY The objectives of the present investigation are: To utilize the waste materials like paper, flyash etc, in the process of manufacturing new type of eco-friendly bricks, namely papercrete bricks. To manufacture and study the strength and durability of the papercrete bricks in order to effectively use these papercrete bricks commercially for construction purposes. To extend the investigation further to study the structural behavior of the papercrete brick masonry experimentally and theoretically.
1.8
METHODOLOGY OF THE STUDY In order to accomplish the aforesaid objectives, the research work
has been divided into nine major parts. They are: (i)
Material collection
(ii)
Study of properties of materials
(iii) Specimen making (iv) Preliminary tests (v)
Optimization of mix
(vi) Behavioural studies on the papercrete bricks and masonry units
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(vii) Comparison of results with conventional bricks (viii) Comparison of results with software analysis (ix) Viability and cost analysis
PROPERTIES OF MATERIALS
MAKING THE SPECIMEN
PRELIMINARY TESTS
COMPRESSIVE STRENGTH
PERCENTAGE OF WATER ABSORPTION
BIO-DEGRADATION
MIX OPTIMIZATION
STUDIES ON STRENGTH OF PAPERCRETE BRICKS
STUDIES ON BEHAVIOUR OF PAPERCRETE MASONRY UNIT
COMPARISON WITH FEM ANALYSIS
COMPARISON WITH CONVENTIONAL BRICKS
VIABILITY AND COST ANALYSIS
CONCLUSION / SUGGESTION
Figure 1.4 Methodology – Flow chart The flowchart in Figure 1.4 represents the methodology of the present work and describes each and every stage of work as well.
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1.8.1
Collection of Materials To attain these goals, materials were collected from various
sources. Material collection is the basic and important step in any project. Yet, the material that is used in a project should not cause any damage to the environment. In the study, paper is the main constituent material. Seshasayee paper board (SPB) mill, Pallipalayam (3 km from the institution) and TNPL paper mill, Karur (30 km from the Institution) are nearby. Both are ISO certified paper mills. Also a lot of small paper mills (Cardboard manufacturing factories) are surrounded by our locality. Papers are collected by two forms. (i) slurry form and (ii) dry form. Slurry form (Paper pulp) was bought from SPB and TNPL. Dry form i.e. old newspapers especially The Hindu is collected from college hostel and college Library. Of these two forms, slurry form is not good enough in fibre content because the slurries are the final output effluent after recycling process. So the news papers were collected and converted to slurry form (paper pulp) using small flour machine. Flyash was collected from Mettur Thermal Plant (dry ash) and the properties were studied. Ricehusk-ash, and micro silica were purchased from an authorized company dealer and those properties were studied. 43 grade cement and sand were collected and the properties were studied as per BIS standard. Also, the water proofing materials were bought from various dealers and the properties were studied and it was conformed with the respective companies. 1.8.2
Preparation of Specimen Waste papers or old news papers were collected from in and around
the locality and shredded into little pieces and then immersed in water bucket.
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After 15 days, the wet papers were taken out and poured into flavor machine. The machine pulverized the paper and it was converted to paper slurry (paper pulp). Normally the paper pulp would be in wet condition. Using pressed filtering, the excess amount of water was expelled. Now, the paper pulp with some residual water content was ready to mix with other ingredients. All the ingredients (excluding paper pulp) were in dry state. All the ingredients were poured into the mixer drum and mixed uniformly electrically. Then the papercrete matrix was sent to collecting drum through conveyor belt. Here the moulds received the matrix and pressing unit compressed the fresh matrix with 10 kN/mm2 hydraulically. Then the bricks were taken out from mould. The size of the papercrete bricks was 230mm X 110mm X 70mm. Within 15days, i.e. after hearing the metallic sound when strikeout the brick surface, the specimen was ready for testing. 1.8.3
Optimization of Mix Through Preliminary Tests As per Indian standards, BIS recommends (IS:1077-1992 and
IS:3495-1992) only four tests for clay bricks, i.e. determination of (a) compressive strength, (b) water absorption, (c) efflorescence and (d) warpage. Of these tests, efflorescence and warpage are observation tests. In this regard, compressive strength and percentage of water absorption are the main criteria for influencing the optimization of papercrete mix. In these stages, paper and cement are the main essential materials for papercrete matrix. Additionally, flyash and/or ricehusk ash and/or silica fume are added with and without sand. From more than 24 trial mixes, successive mix was found out. In order to improve the resistant of water absorption, different types of water proofing agents were added in desirable
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dosage to papercrete matrixes. Finally, depending upon the compressive strength, percentage of water absorption and also bio-degradation test, the papercrete mix was optimized. 1.8.4
Studies on Papercrete Bricks and Masonry Unit The flyash based coated papercrete bricks were studied for
compressive strength, percentage of water absorption, acid resistance, behaviour under elevated temperature, sorptivity and thermal conductivity. Before the masonry construction, the loading frames were designed and the set up was installed on rigid firmed floor in structural engineering laboratory. In the first stage, loading frame was tested without infilled masonry and recorded the behaviour of frame using Prosof software. Then, flyash based papercrete brick masonry and conventional clay brick masonry were infilled in the loading frame separately. The behaviour of infilled masonry walls were studied. 1.8.5
Comparison of Results The results from compressive strength, percentage of water
absorption, acid resistance and sorptivity of flyash based papercrete bricks were compared with conventional clay bricks and modular flyash bricks. The results from the behaviour of infilled flyash based papercrete brick masonry wall were compared with conventional clay brick masonry wall. Also a model infilled flyash based papercrete brick masonry wall is created using ANSYS software and compared with experimental results. 1.8.6
Viability and Cost Analysis The preliminary test results show some negative points. But by
taking the efforts from literature support and discussing with field and
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academic experts, the negative points were rectified by using internal and external water proofing admixtures. So the coated papercrete bricks are the viable and sustainable material in nature and environment. The cost of the material plays an important role in the construction industry. The cost analysis of papercrete bricks was studied at the end of the project and it was compared with conventional clay and modular flyash bricks. The cost of conventional clay bricks and modular flyash bricks were calculated based on July 2011 rate at Namakkal District, TamilNadu, India. 1.9
ORGANISATION OF THE THESIS The thesis consists of nine chapters. The first chapter gives a brief
introduction to the investigations carried out and explains the research significance of the proposed investigation. Chapter 1 presents the objectives of the study and methodology to be followed for the research work. Chapter 2 reviews critically the previous studies in the fields of utilization of waste materials and papercrete. Towards the end of this chapter, a summary of earlier works and the scope of the present investigation are discussed in detail. Chapter 3 describes the properties of papercrete ingredients. Chapter 4 deals with the effect of mineral admixture in papercrete bricks. In this chapter the effects of addition of flyash, micro silica, rice husk ash, sand and cement on the various mechanical properties like compressive strength, water absorption were studied. Concluding remarks of these studies are presented at the end of the chapter. Based upon the chapter 4, some negative observations have been faced. Rectifications of these problems are given in Chapter 5 under the title of Papercrete mix optimization with flyash and based on the trial mixes, the papercrete mix was optimized. In view of that, bio-degradation test was conducted on flyash based papercrete building bricks. The chapter deals with the studies on the micro characterization of
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papercrete bricks also and at the end of the chapter concluding remarks of the studies are noted. Chapter 6 is devoted to study the strength and durability of the coated flyash based papercrete bricks. Finally, it presents a comparison of these results with conventional brick results. In Chapter 7, the strength and behavior of flyash based papercrete masonry are delineated. In this chapter, ANSYS modal has been proposed in order to compare and verify the results. Cost analysis of flyash based papercrete brick is done in Chapter 8 and also it is compared with the cost of the conventional brick. Finally, the conclusions arrived at in each chapter are summarized in Chapter 9. At the end of this chapter, the social outcome of the project in the present research work is highlighted and the scope for future work is also suggested.
