GEO-POLYMER FERROCEMENT SLABS

A PROJECT REPORT

Submitted in partial fulfillment for the award of the degree of

BACHELOR OF TECHNOLOGY

in

CIVIL ENGINEERING

by

MANAS PRATAP SINGH

(11BCL0108)

PRANAV PHALPHER

(11BCL0155)

School of Mechanical and Building Sciences

MAY 2015

ACKNOWLEDGEMENT

First of all we are thankful of our project guide Professor Sofi A., under whose guidance we were able to complete our project. We are wholeheartedly thankful to her for giving us her valuable time, attention and for providing us a systematic way for completing our project on time. We would like to thank her for her co-operation & assistance. We would thank all the lab maintenance staff for providing us assistance in various h/w & s/w problem encountered during course of our project. We also take this opportunity to express a deep sense of gratitude to Dr.Venkata Ravi BabuMandla, Program Chair, Civil Engineering for his cordial support, valuable information and guidance, which helped us in completing this task through various stages. Last but not the least, we pay our deepest gratitude to Prof. S. K. Sekar, Dean, SMBS for all his efforts in choosing the topic and keeping us on the right path throughout. Our first experience of project has been possible, thanks to the support staff of many friends and colleagues.

Place        : Vellore                                                     Signature of the Students

         :                                                                                   (Manas Pratap Singh)

                                                                                                (Pranav Phalpher)

TABLE OF CONTENTS

EXECUTIVE SUMMARY

The large global production of fly ash and rapid advances in geopolymer technology and knowledge mean that a viable alternative to ordinary portland cement concrete is now available, in the form of alkaline-activated class F fly ash geopolymer concrete. The aim of this research is to examine a potential mix design process for this emerging product. A process that can be worked through in a calculated way in order to find the full range of mix proportions to meet a particular targeted product has not been investigated or submitted to date. This research seeks to bridge this gap, which is currently preventing the more widespread use of geopolymer concrete (GPC). This work is a largely experimental investigation into mixture proportion and strength relationships, attempting to detail a large amount of data which will be utilised at the core of the process to be investigated. It was found that the process proposed and investigated does form a valid mix design process. It has been proven that a practical mix design process for GPC has been created.

Efforts are needed to develop innovative and environmentally friendly material in order to reduce the greenhouse gas emissions. The purpose of this experimental investigation is to study the flexural behaviour of fly-ash based geo-polymer ferro-cement elements. Ferro-cement composite is a rich Geo-polymer mortar mix of 1:1. The alkaline activators used consist of Sodium hydroxide and sodium silicate. The length of first batch of ferro-cement elements was chosen as 400 mm, width 150 mm and depth of the section was 30 mm. Nine number of rectangular slab were prepared with different meshes such as Square woven, Square welded and Expanded metal mesh. This batch is oven dried for curing. The number of layers in each mesh was varied from single, double and triple layers. Based on the test results, load v/s deflection curves were down. The effectiveness of the Square woven, Square welded and Expanded metal mesh were compared and results showed that slabs with square welded mesh triple layer were most suitable and cracked at highest load.

LIST OF TABLES

LIST OF FIGURES

List of Symbols, Abbreviations and Nomenclature

kN – Kilo Newton

M – Molar (molarity is the concentration of a solution given in gram

moles of solute per liter of solution.

CHAPTER-1

INTRODUCTION

The purpose of this experimental investigation is to study the flexural behaviour of flyash based geo-polymer ferro-cement elements. An attempt has been made to study the behaviour of ferro-cement slabs in flexure.  Cement is replaced by fly-ash 100 % in a mix in order to reduce the pollution caused due to production of cement (CO2 formation). Also the slabs formed with geo-polymer ferro-cement slabs are provided with extra reinforcement by providing 1,2 and 3 layers each of  Square woven, Square welded and Expanded metal mesh. The best combination which gives highest strength is considered as the successful outcome.Extensive consumption of natural sources, massive amount production of industrial wastes and environmental pollution require new solutions for a more sustainable development. The use of modern day cement contributes to two billion tons of carbon dioxide (CO2) annually in to the atmosphere, which makes it the third largest man-made source of CO2. The production of cement is responsible to produce one ton of CO2 per ton of cement produced, and the cement manufacturing industry is causative to contribution of 7% of global CO2 emission, which is one of the greenhouse gases that cause climate change due to global warming. Besides, production of cement is energy intensive and is only succeeding to steel and aluminium production. Meanwhile, the growth of the coal fired power plant industry produces flue gases from hydrocarbon combustion that generates extensive particulate emissions such as fly ash, bottom ash as waste products. These solid waste ashes from coal fired boilers have previously been dumped into the landfill that contributes to the subsequent environmental contamination. Hence, green demands are raised for alternative ways to utilize the ashes to mitigate further environmental pollution by copious uncontrolled disposal of the coal ashes in the landfills.

The term geo-polymer was first applied by Davidovits to alkali aluminosilicate binders formed by the alkali silicate activation of aluminosilicate materials. Geopolymer is amorphous to semi-crystalline equivalent of certain zeolitic materials with excellent properties such as high fire and erosion resistances and high strength materials. The most used alkaline activators are a mixture of sodium hydroxide or potassium hydroxide (NaOH or KOH) with sodium water glass or potassium water glass. The activator solution used in this work is NaOH and sodium water glass. The concentration of NaOH solution can be used is 16M. Prefabricated floor is used in the construction industry as an alternative system to overcome the formwork problems (cost and delay in construction) in addition to getting better quality control. The prefabricated elements made of reinforced concrete are extremely heavy and difficult to transport, placing in position and to construct. Alternatively, thin ferrocement panels are being used in floor construction for low cost housing due to its low cost and good structural performance. Ferro-cement is suitable for low-cost roofing, pre-cast units and man-hole covers. It is used for the construction of domes, vaults, grid surfaces and folded plates. It can be used for making water tanks, boats, and silos. Ferrocement is the best alternative to concrete and steel. Generally, ferrocement shells range from 10 mm to 30  mm in thickness and the reinforcement consists Ferrocement is a type of thin wall reinforced concrete commonly constructed of hydraulic cement mortar reinforced with closely spaced layers of continuous and relatively small size wire mesh which may be made of metallic or other suitable materials. Since ferrocement possess certain unique properties, such as high tensile strength-to-weight ratio; superior cracking behavior; lightweight; moldability to any shape and certain advantages, such as utilization of only locally available materials and semi-skilled labor/workmanship, it has been considered to an attractive material and a material of good promise and potential by the construction industry, especially in developing countries. It has wide-ranging applications, such as in the manufacture of boats/barges; prefabricated housing units; biogas structures; silos, tanks, and recently in the repair and strengthening of structures. Ferrocement is a highly versatile construction material and possess high performance characteristic, especially in cracking, strength, ductility, and impact resistance. As its reinforcement is uniformly distributed in the longitudinal and transverse directions and closely spaced through the thickness of the section . Since ferro-cement bends itself to precasting and hence, precast ferro-cement elements can be prepared to meet the strength and serviceability conditions. There is an ample scope for mass production and standardization together with the economy in construction.

1.1 Objectives

The main objective of the present investigation is to study the behaviour of Geo-polymer Ferro-cement slabs (replacement of cement with 100% activated fly-ash). Geo polymer mortar is prepared by sand :flyash plus activator solution in 1:1 ratio .Slabs are casted using different meshes and tested under the UTM. The primary objective of this study was development of viable housing components which could be used as multipurpose structural elements.In this context, multipurpose structural elements are meant as ferrocement element, which can act both as floor and wall elements. Ferrocement slab stiffened by square and rectangular section was found to be a suitable shape for multipurpose elements. In this investigation, ferrocement element having the shape of rectangle was chosen.

1.2 Motivation

Cement industry is one of the major contributors to the emission of greenhouse gasses like carbon dioxide which is about 1.35 billion tons annually. Day by day the World’s Portland cement production increases with the increasing demand of construction industry which crossed one thousand million tons per year. On the other side, fly ash is the waste material of coal based thermal power plant, which is available abundantly but creates disposal problem. Hence in order to reduce the emission of greenhouse gas by lowering cement production and finding effective use of fly-ash which would cause problems of disposals, a lot of problems can be evaded.

1.3 Background

Concrete, as a major construction material, is being used at an ever increasing rate all around the world. Almost all of this concrete is currently made using OPC, leading to a massive global cement industry with an estimated current annual production of 2.8 billion tonnes  and increasing by 3% annually . OPC production is an extremely energy-intensive process, and therefore there has been a significant push in the past two decades to develop alternative binders, other than OPC, to make concrete. This has largely been due to the requirement to address the environmental effects associated with OPC concrete.

Almost all research into GPC technology was initially directed towards the behaviour and reactions of the geopolymer binder component, while in the past decade there has been a shift towards studying the mechanical properties and mix design. While this work, as a consequence of studying the individual effects of parameters has discussed mixture design, not yet has a full mix design process been investigated. The term full mix design process is hereby defined as a process that could be used to calculate all mixture proportions and produce a result within an acceptable range of an initial targeted compressive strength.

All previous studies/results do not broadly allow this; they simply publish results for limited mixture proportion examples. If a mix design process that enables a designer to calculate a set of mixture proportions for a wide range of strengths and curing parameters could be developed, then the use of FA-based GPC would be much simpler for persons other than academic researchers.

It is likely then, that if a relatively simple mix design process were available, more people would be prepared to use the product. If this wider use of GPC could occur, then the environmental and potential financial benefits associated with GPC could be realised. In the process, the increasing demand for OPC may stall. However at a lower and more realistic level, it would enable much easier use of GPC for researchers and engineers alike. If the design of a GPC mixture can become broadly viewed in the same (relatively simple) light as an OPC concrete mix design, then its use has the potential to become much more widespread. This research and testing could be significant in the near future as it could lead to the wider use of GPC technology, building upon previous research in the area.

The reason we use Geo-polymer mortar is because it is a cementitious material, better alternate to cement, as it possesses the advantages of rapid strength gain, elimination of water curing, good mechanical and durability properties and also the manufacturing of Portland cement emits large amount of CO2 into the atmosphere.

The production of one ton of Portland cement liberates about 1 ton of carbon dioxide to the atmosphere. Geo-polymer mortar is a binder material, produced from an alumino-silicate activated in a high alkali solution. Molarity is the concentration of sodium hydroxide in alkaline solution. The increase in molar concentration results in increase in the compressive strength. Hence, 16M is considered as the favourable molarity to attain high compressive strength.

CHAPTER 2

PROJECT DESCRIPTION AND GOALS

The large global production of fly ash and rapid advances in geo-polymer technology and knowledge mean that a viable alternative to ordinary Portland cement concrete is now available, in the form of alkaline-activated class F fly ash geo-polymer concrete. The aim of this research is to examine a potential mix design process for this emerging product. This research seeks to bridge the gap, which is currently preventing the more widespread use of geo-polymer concrete (GPC). This work is a largely experimental investigation into mixture proportion and strength relationships, attempting to detail a large amount of data which will be utilised at the core of the process to be investigated.

The experimental investigations of the resistance of geo-polymer mortar slabs to impact loading. For this, specimens of size 400 mmx150mmx30mm were casted with the reinforcement provided by different meshes. The shape of woven and weld mesh are square and the expanded mesh has a diamond shape, each mesh has 15 x 15mm opening size, the length and width of the meshes are chosen as 400 x 150mm. Thickness of joint in each mesh 7.22mm and the diameter of wire is 1.5mm. The meshes are available in role form, they have density of above 0.9 g/cm3, tensile test conducted on the meshes indicate they have tensile of structural of about 34.5Mpa. These slabs are subjected to single point loading system using Universal Testing Machine (UTM).

The significance of this research can only be judged upon how it is developed upon or embraced by researchers and academics. If it is recognised by a number of people, or the findings further published in others work, then this process for GPC mix design has a better chance of being embraced and further developed. If the mix design process for GPC can become accepted and viewed as practically useful as that of OPC concrete, then it has the potential to become used on a more widespread basis. This requires a concrete industry mindset change on the topic of GPC, so that GPC design and use is viewed as accessible, realistic and practical, rather than unusual and

unpractical. The project team believes that this research and its findings will be used and developed, creating wider knowledge and application of the acceptable mix design process to be detailed.

CHAPTER 3

TECHNICAL SPECIFICATION

While the overall goals, strategies and objectives have been stated, the specifications of the components will be determined as they are identified for their applicability in the project. The overall system will meet the specifications as stated.

Whilst studying the chemistry of geopolymers is not the aim of this research, this area must broadly be looked at to gain an understanding of the topic at hand. The reaction of a solid aluminosilicate with a highly concentrated aqueous alkali hydroxide or silicate solution produces a synthetic alkali aluminosilicatematerial which is now generically called a geopolymer [7]. More simply, an alkaline liquid chemically reacts (at a relatively fast rate) with silicon and aluminium molecules contained in an active pozzolanic material (FA in this case) to produce a binder.

It is mostly agreed that the result of the above reaction is an amorphous three-dimensional network, however the formation mechanism of the geopolymer network is still debated . Yet this lack of agreement has not inhibited further study, as it has proven to be a predictable and reliable reaction

The following materials are employed in this work:

• Fine aggregate (sand)

• Low calcium fly ash

• Geopolymers (NaOH + sodium silicate

  Steel Meshes :

• Square woven and Square welded (square)
• Expaned metal mesh (hexagonal)

II. The pozzolan used here is the low calcium fly ash of class-f obtained from the Tuticorin thermal power plant. The chemical composition of the fly ash, as determined by X-ray fluorescence analysis is given.

III. Geopolymer is a combination of the following compounds:

• Pozzolans (fly ash, silica fumes, Ground Granulated Blast-furance Slag, Metakaolin)
• Activator solution (silicates of sodium or potassium)
• Alkali powder (hydroxides of sodium or potassium)
• A high-range water reducing ligno-sulfonated normal

CHAPTER 4

DESIGN APPROACH AND DETAILS

4.1 Design Approach

The mechanical properties, including compressive strength, of FA-based GPC are influenced by a large number of parameters that interact in a complex and relatively unknown manner. This is somewhat different to OPC concrete, where the value of the water-to-cement ratio is the sole primary consideration for strength. In this research, the number of influencing parameters determined by the mix design itself has been found to be mainly four.

They are mentioned below

1. Water to Geopolymer Solids Ratio (W:GPS)

So as to assist in the design of Class F FA-based GPC mixtures, a parameter called the ‘water-to-geopolymer-solids ratio’ (by mass) (W:GPS) was devised , and is now used by most GPC mix researchers. The W and GPS components are the total of water (from sodium silicate, sodium hydroxide and any extra water) and geopolymer solids (from fly ash, sodium hydroxide solids and sodium silicate solids) respectively. Testing has shown that the compressive strength of GPC increases as the W:GPS ratio by mass decreases , while the workability expectedly decreases. This is universally agreed upon by GPC researchers.

2. Alkaline Liquid to Fly Ash Ratio (AL:FA)

This ratio, second to the W:GPS, forms the second important ratio in the mix design of GPC. There is an interconnectivity between the ratios of W:GPS and AL:FA, therefore generally as AL:FA increases compressive strength increases. In some studies, AL:FA has been kept constant , however it is believed by the author of this report that in this area there is a lack of knowledge, and therefore it will be further investigated in this research.

3. Ratio of Sodium Silicate to Sodium Hydroxide Solution (Na2SiO3:NaOH)

The Na2SiO3:NaOH solutions ratio, which then also affects the W:GPS and AL:FA ratios, is important as it contributes to the properties of the alkaline liquid which is the activator in the binder-producing reaction in any GPC. It is unanimously agreed upon that as this ratio increases so too does the compressive strength . This ratio has been bracketed as NaOH is costlier than Na2SiO3, and research of very high ratios  has not been carried out.

4. Molar Concentration of Sodium Hydroxide

A second parameter that affects the quality/content of the alkaline liquid is the molar concentration of NaOH. Experimental results from previous research have all shown that a higher concentration in the NaOH solution results in higher compressive strength [2, 8]. Effects of a concentration greater than 16M have not been investigated; however, this does not form the emphasis of this research.

C. Similarities and Differences between OPC Concrete and GPC

An important area to investigate within FA-based GPC is how it works, and to distinguish it from OPC concrete. Whilst GPC is a concrete-like material, it is fundamentally different to the normal Portland cement (OPC) concrete that we see every day. However, there are also a number of similarities between the two.

D. Mix Design Procedures

1. Current Mix Design Procedures for OPC concrete

There are various presently-used mix design procedures for OPC concrete, including :

a. American method

b. British method

c. Any number of methods used by individuals as a result of their experiences

This area is very well established and trusted due to the amount of time spent studying and using OPC concrete over the past couple of centuries. However, it is important to note that while there are established mix design procedures, the process is still only a guide that should first be tested, altered and then re-produced for practical use.

2. GPC Mix Design Research

There has been a large amount of research into GPC technology over the past two decades as the potential benefits have become recognised. Almost all initial research was directed towards the behaviour and reactions of the binding paste. In the past decade there has been a shift towards studying the short-term mechanical properties, along with a sizeable study of the effects of different parameters in the mix proportions.

Significant progress in regards to the effects of varying the different parameters has since been made, and this work is vitally important in the overall study of GPC. This review of current literature has found that where a mix design process is prescribed, it mostly refers to the resulting compressive strengths for given mix proportions, and gives reasons why those certain parameters are acceptable. Hence a full mix design process has not been determined by any researcher. This is a significant gap of knowledge, and forms the basis for this research.

The experimental investigations of geo-polymer mortar slabs subjected to UTM under single point loading system. For this, specimens of size400mmx 150mmx 30mm were casted with single, double and triple layer of square welded, square woven and expanded metal mesh and were tested  under UTM.

The Design consists of a mould which is filled with GPC and in between there are 1,2 and 3 layers of wire meshes to provide strength. The tests carried out later i.e., after this review shall give us the best suited wire mesh out of the three ( Square mesh, Square woven mesh and Expanded metal mesh) and either 1, 2 or 3 number gives the best test results

4.2 Codes and Standards

a. ACI Committee 549 , “state of the art report on ferrocement” ACI 549R97, in Manual Of Concrete Practice, ACI, Detroit, 1997.

b. ACI Committee 5491R88, Guide For Design Construction And Repair Of Ferrocement, ACI 5491R88 and 1R93 in Manual of Concrete Practice.

c. IS 383 1970 : Specification for Coarse and Fine Aggregates From Natural Sources For Concrete [CED 2: Cement and Concrete]

d. IS 38121 2003 : Specification for Pulverized Fuel Ash, Part 1: For Use as Pozzolana in Cement, Cement Mortar and Concrete [CED 2: Cement and Concrete]

e. IS 23863 1963 : Methods of test for aggregates for concrete, Part 3: Specific gravity, density, voids, absorption and bulking [CED 2: Cement and Concrete]

f. IS 14858 2000 : Requirements for compression testing machine used for testing of concrete and mortar [CED 2:Cement and Concrete].

4.3 Constraints and Tradeoffs

Constraints

Economic : The overall cost of project is about Rs. 5000/. The cost can go up due to the wastage of chemicals due to experimental errors. The production cost is expected to cost less than slabs made with cement.

Environmental : Also, geo-polymer mortar is a cementitious material, better alternate to cement, as it possesses the advantages of rapid strength gain, elimination of water curing, good mechanical and durability properties and also the manufacturing of Portland cement emits large amount of CO2 into the atmosphere.

Sustainability : The basic aim is to find the extent to which the flyash based geo-polymerferrocement slabs can be made more sustainable with different meshes and different curing procedures.

Tradeoffs

When Flyash was taken as a 100% replacement for cement in 400mm x 150mm x 30mm slabs, the slabs could not be put in the oven as the space in it was small for it and water curing for geopolymerferro-cement slabs is not feasable. So, the design was changed and the the dimensions of the slabs were taken as 400mm x 150 mm x 30mm.

400mm x 150mm x 30mm slabs were casted and are cured by oven drying for 48 hours

CHAPTER 5

SCHEDULE, TASK AND MILESTONES

There are three major milestones as well as several smaller tasks that must be achieved in order to reach the milestones. The three milestones are:

The alkaline liquid is prepared at least one day prior to cast. Firstly, the NaOH solution is prepared for the required molarity and then it is mixed with Na2SiO3 in 1:1. Finding optimum Water-Binder ratio of the mix and also the molarity of the binder.Molarity on Compressive Strength of Geopolymer Mortar 85 proportion. The samples were prepared for 8M, 10M and 16M. (where, M–molarity). For e.g. 8M means, concentration of NaOH in one litre of water is 8 × 40 = 320gm (where 40 is the molecular weight of NaOH). Mix proportions for various samples are illustrated in

Table 5.2: Mix proportions of materials used in experiment.

Specimen   Molarity   Water binder ratio   Activator-Fly Ash ratio   Sand–Fly Ash ratio

Sample 1        8                   0.30                           0.50                                    1.0

Sample 2        10                 0.30                           0.50                                    1.0

Sample 4        16                 0.30                           0.50                                    1.0

• Casting and curing

The fly ash and the alkaline solution are first mixed together in specified proportion for 5 minutes. Sand is then added and mixed for another 5 minutes. The mortar samples have been casted in steel moulds of size 70.6mmX70.6mmX70.6mm. The mortar is then filled in mould in two layers and hand compacted using cylindrical plunger. After casting, geopolymer mortar samples are left to room temperature for one hour under atmospheric pressure and uncontrolled humidity conditions and are cured in an oven at 85°C for 48 hours. At the end of curing period the oven is turned off and the materials is allowed to cool down inside the oven to room temperature. The samples are then removed from the mould and they are left to air curing (drying) at room temperature before being used in tests.

• Casting the slabs, demoulding and putting in the oven for drying.

Weld mesh were cut to appropriate dimensions to suit the configuration of square elements. The weld mesh were placed at the appropriate position to make the slab. The element were cast using the plastering techniques on the level floor of casting yard using very simple wooden formwork. The mould was placedon the level platform of casting yard after applying a thin coat of oil. The mortar mix is put inside the mould and made level while keeping the meshes at particular intervals.

• Finding the number of meshes to be used as well as the mesh to be used

CHAPTER 6

PROJECT DEMONSTRATION

The rectangular ferrocement elements were tested to study their flexural behaviour. The general testing arrangement, test set up, instrumentation and testing procedure are explained in the following section. The element was made ready for necessary instrumentation and observation of readings. After arranging the necessary arrangement to measure the strain at middle span, dial gauge were mounted below at middle of the span. The deflection

measurements were taken from the middle points.

6.1 Testing Procedure

Testing is done for 400mm x150mm x 30mm size slabs. The slab is fixed in UTM under single point loading system. The slab is kept on the frame and UTM is set. The load is applied gradually on the slab, for every 0.20kN of load application the corresponding deflection reading should be taken. The load should be gradually increased and loading is done till the failure. The first crack load corresponding to that was noticed as the first crack load. The failure load is noted and corresponding deflection is also noted the slab failed due to flexure. The load and deflection reading is taken and the graph is drawn against load vs deflection.

Figures of tests performed on slabs.

6.1 Test being carried out on slab with square woven mesh with single layer

6.2 Crack on square woven mesh with single layer

6.3 Universal testing machine being set

6.4 Crack on expanded metal mesh with triple layer

6.5 Crack on square welded mesh slab with double layer

6.6 Slab placed in UTM

6.7 Deflectometer placement  

6.8 Expanded metal mesh triple layer slab placement in UTM

6.9 Crack on square woven mesh with double layer

6.10 Crack on slab with the load application in progress

After the slabs undergoing tests, tables are made and load versus deflection is checked. This helps in forming graphs for final results and conclusions.  

                           TABLE 6.1 EXPANDED METAL MESH SINGLE LAYER  

TABLE 6.2 EXPANDED METAL MESH DOUBLE LAYER

TABLE 6.4 SQUARE WOVEN MESH SINGLE LAYER

TABLE 6.5 SQUARE WOVEN DOUBLE LAYER

                                        TABLE 6.6 SQUARE WOVEN TRIPLE LAYER

CHAPTER 7

RESULTS AND DISCUSSION

For Expanded Metal mesh slab with single layer, Initial crack for the Triple layer occurred at 2.6kN, for Double layer occurred at 2.2kN andfor Single layer occurred at 1.8kN.

         Deflection (mm)

                                   Figure 7.1 EXPANDED METAL SINGLE LAYER

            Deflection (mm)

                                  FIGURE 7.2 EXPANDED METAL DOUBLE LAYER

1. 
2.                                                          Deflection (mm)

                                                      7.3 EXPANDED METAL THREE LAYER

For Square Woven mesh slab with single layer, Initial crack for the Triple layer occurred at 2.2kN, for Double layer occurred at 2kN andfor Single layer occurred at 1.8kN.

                                           DEFLECTION (mm)

                        FIGURE 7.4 SQUARE WOVEN SINGLE LAYER

DEFLECTION (mm)

    FIGURE 7.5 SQUARE WOVEN DOUBLE LAYER

                                   DEFLECTION (mm)

                           FIGURE 7.6 SQUARE WOVEN TRIPLE LAYER

For Square Welded mesh slab with single layer, Initial crack for the Triple layer occurred at 4.6kN, for Double layer occurred at 2.8kN andfor Single layer occurred at 2.2kN.

                DEFLECTION (mm)

1.                                     FIGURE 7.7 SQUARE WELDED SINGLE LAYER

                                           DEFLECTION (mm)

DEFLECTION (mm)

FIGURE 7.9 SQUARE WELDED THREE LAYERED

Hence, it can be seen through the results above that the best-suited mesh for slabs is SQUARE WELDED and the number of mesh layers should be three (3) in number.  As it cracks at highest load and bears it as well i.e. 4.6 kN.

CHAPTER 8

SUMMARY

The ferrocement structural elements involved in this study are having a simple crosssection and it can be fabricated easily with the help of simple formwork.

Increasing the number of steel mesh layers from 1 to 3 caused a substantial increase in flexural strength and energy absorption to failure. It was observed that the linear first stage ceases with the initiation of cracking in mortar on the tension force. The load carrying capacity of the specimens, however, continues to increase because the meshes start carrying additional load. with further increase in load, the tension face of the specimen starts cracking following by cracking of the compression face and finally forming a major failure of the compression face and finally forming a major failure crack at the middle of the specimen.

It was also observed that the flexural strength of the section increasing the number of wire mesh layers. This is because of the increased percentage of steel meshes in the specimens and the increased depth of mesh layers from the neutral axis. For the same number of mesh layers, it was found that the strongest configuration in both elastic and inelastic ranges results from the smallest spacing because of the increase in volume fraction of the mesh in longitudinal and transverse direction of the specimens

From this study it can be considered the Weld mesh is resulted in significant improvement in their flexural behaviour compare to woven and expanded mesh. The use of weld mesh in the ferrocement structure gives more strength and significant improvement to the ferrocement.

CHAPTER 9.

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CHAPTER 10

APPENDIX GANTT CHART