Project Report

JOMO KENYATTA UNIVERSITY OF AGRICULTURE AND TECHNOLOGY

DEPARTMENT OF CIVIL, CONSTRUCTION AND ENVIRONMENTAL ENGINEERING

ECE 2505 FINAL YEAR PROJECT

TITLE APPLICATION OF U-BOOT TECHNOLOGY IN KENYA

NJUGUNA ANNE WANJIKU E25-0126/04

PROJECT SUPERVISOR ENG. MAN’GURIU

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DECLARATION “I declare that this is my original work. I also confirm that to the best of my knowledge, this report has not been presented in this or any other university for examination or for any other purposes. This work forms part fulfillment of the requirements for the award of the degree of Bachelor of Civil, Construction and Environmental Engineering of the Jomo Kenyatta University of Agriculture and Technology”.

Signed (Author) _______________________Date________________ Njuguna Anne Wanjiku

CERTIFICATION I have read this report and approved it for examination.

Signed (Supervisor) ____________________ Date______________ Eng. Manguriu

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DEDICATION To almighty God for the life and strength he has granted me. To my family and friends for their treasured encouragement and support.

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ACKNOWLEDGEMENT I wish to sincerely acknowledge the contributions of all those who assisted me either directly or otherwise towards the undertaking of this study.

The success of this research is attributed to Jomo Kenyatta University of Agriculture and Technology for providing material and financial support and all the staff of the department of civil, construction and environmental engineering for their invaluable contribution.

Special thanks to Eng. Mang’uriu, my supervisor, for rigorously guiding me through the research process. To my classmates, thank you for your creative criticism and ideas.

Any errors or omissions that may be contained in this research report do not in any way reflect the contributions of the parties mentioned above and I would take full responsibility for the same.

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ABSTRACT Developments in the building industry are geared toward cost effective and environmentally sustainable construction. Concrete is the most common construction material used in the world and cement is the main ingredient in concrete. However, cement manufacturing is a source of greenhouse gas emissions, accounting for approximately 7% to 8% of CO2 globally. In view of these facts, it is important to reduce the environmental impacts of cement production by reducing the quantity of concrete that is used in construction. This paper seeks to find out whether the u-boot slab is cheaper compared to traditional solid slab used in Kenya, and to find out the amount of concrete reduction that is achieved by use of u-boot slabs and its impact on the environment, and also compare the strength characteristics of u-boot slab and traditional solid slab.

The study involved the design and analysis of two-way spanning solid slab, and u-boot slab. Structural detailing was carried out for the slabs and bar bending schedules and bill of quantities were prepared. The u-boot slab and a solid slab were also cast and strength tests were carried out on them.

From the study, it was found that the use of u-boot slab resulted in a saving of concrete of about 10%, and up to 25% decrease in carbon dioxide emissions when compared to a solid slab with internal beams. The u-boot slab was also found to have bigger spans of up to 18m, while solid slabs had a maximum span of 9m for a given load. For fixed spans the u-boot slab had a higher bearing capacity compared to solid slabs. A comparison of the total cost for the two slabs showed that the u-boot slab was more expensive and this is mainly due to the cost of importing the u-boots which are currently not produced in the country.

From the study it was concluded that the u-boot slab is most suitable for slabs with high loading, with live loads of 5kN/m2 and above and where large open spaces are required. Use of the u-boots was also encouraged for the sake of environmental preservation. To cut down on costs of acquiring the u-boots, it was recommended that local production of the units should be considered.

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CONTENTS DECLARATION .......................................................................................................................... ii CERTIFICATION ..................................................................................................................... ii DEDICATION .......................................................................................................................... iii ACKNOWLEDGEMENT ........................................................................................................ iv ABSTRACT ............................................................................................................................... v 1. INTRODUCTION ................................................................................................................ 1 1.1 BACKGROUND INFORMATION ..................................................................................... 1 1.2 POLYPROPYLENE ............................................................................................................ 2 1.4 PROBLEM STATEMENT .................................................................................................. 3 1.5 PROBLEM JUSTIFICATION ............................................................................................. 3 1.6 OBJECTIVE ........................................................................................................................ 4 1.6.1 General Objectives .................................................................................................. 4 1.6.2 Specific objectives ................................................................................................... 4 1.7 RESEARCH HYPOTHESIS ............................................................................................... 4 1.8 LIMITATIONS OF THE STUDY ....................................................................................... 4 1.9 EXPECTATIONS OF THE STUDY ................................................................................... 4 2. LITERATURE REVIEW .................................................................................................... 5 2.2

PRE-STRESSED CONCRETE...................................................................................... 5

2.3

HOLLOW-CORE SLABS ............................................................................................ 5

2.4

BI-AXIAL SLABS ....................................................................................................... 6

2.5

WAFFLE SLAB ........................................................................................................... 6

2.6

BUBBLE DECK TECHNOLOGY ............................................................................... 7

2.7

U-BOOT TECHNOLOGY ........................................................................................... 7

2.8

BENEFITS OF U-BOOT SLAB................................................................................... 9

2.9

RAFT FOUNDATIONS. ............................................................................................ 10

2.10

SHEAR REINFORCEMENT OF SLAB .................................................................... 11

2.11

FIRE RESISTANCE ................................................................................................... 12

2.12

CONCRETE MIX ....................................................................................................... 13

3. RESEARCH METHODOLOGY...................................................................................... 14 3.1

INTRODUCTION ...................................................................................................... 14

3.2

SLAB DESIGN ........................................................................................................... 14

3.3

U-BOOT FORMWORK ............................................................................................. 14

3.4

SIEVE ANALYSIS .................................................................................................... 15

3.5

SLUMP TEST............................................................................................................. 15

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3.6

U-BOOT LAYOUT .................................................................................................... 16

3.8

STRENGTH TESTS ................................................................................................... 18

3.9

MEASUREMENT OF QUANTITIES ....................................................................... 19

4. RESULTS AND DISCUSSION ........................................................................................ 20 4.1

SIEVE ANALYSIS .................................................................................................... 20

4.2

SLUMP TEST............................................................................................................. 22 4.5.1

CONCRETE .................................................................................................. 27

4.5.2

STEEL REINFORCEMENT ......................................................................... 27

4.5.3

SPAN COMPARISON .................................................................................. 27

4.5.4

ECONOMIC FEASIBILITY ANALYSIS .................................................... 28

5. CONCLUSION AND RECOMMENDATIONS ............................................................. 29 BIBLIOGRAPHY .................................................................................................................. 30 APPENDIX ............................................................................................................................. 31 APPENDIX 1: DESIGN CALCULATIONS ....................................................................... 31 APPENDIX 2: STRUCTURAL DRAWINGS ..................................................................... 34 APPENDIX 3: BAR BENDING SCHEDULES ................................................................... 35 APPENDIX 4: MEASUREMENT OF QUANTITIES & BILL OF QUANTITIES ........ 36 BUDGET ................................................................................................................................. 41

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LIST OF TABLES AND FIGURES FIG 1: SECTION OF SLABS WITH U-BOOT ........................................................................ 1 FIG. 2: BUBBLE DECK SLAB ................................................................................................ 7 FIG. 3: U-BOOT UNIT ............................................................................................................. 8 FIG. 4: U-BOOT SLAB LAYOUT............................................................................................ 9 FIG. 5: SECTION OF RAFT FOUNDATION WITH U-BOOT ............................................. 10 FIG 6: THE U-BOOT ELEMENT USED FOR THE SLAB. .................................................. 14 FIG 7: SIEVE ARRANGEMENT ........................................................................................... 15 FIG 8: CASTING OF THE U-BOOT SLAB ........................................................................... 16 FIG 9: CURING OF THE U-BOOT SLAB ............................................................................. 17 FIG 10: CURING OF THE SOLID SLAB .............................................................................. 17 FIG 11: COMPRESSIVE TEST .............................................................................................. 18 FIG 12: SLAB TESTING ........................................................................................................ 19 TABLE 1: FINE AGGREGATE GRADING .......................................................................... 20 FIG 13: GRAPH OF TABLE 1 ................................................................................................ 21 TABLE 2: COARSE AGGREGATE GRADING ................................................................... 21 FIG 14: GRAPH OF TABLE 2 ................................................................................................ 22 TABLE 3: SLUMP TEST. ....................................................................................................... 22 TABLE 4: COMPRESSIVE STRENGTH TEST .................................................................... 23 TABLE 5: SOLID SLAB TEST RESULTS ............................................................................ 24 TABLE 6: U-BOOT SLAB TEST RESULTS ......................................................................... 24 FIG 15: DEFLECTION CURVES FOR THE SOLID AND U-BOOT SLABS ...................... 25 FIG 16: STRAIN CURVES FOR THE SOLID AND U-BOOT SLABS ................................ 25 FIG 17: FAILURE IN SOLID SLAB, CRACKS .................................................................... 26 FIG 18: FAILURE IN SOLID SLAB, SHEAR ....................................................................... 26 FIG 19: FAILURE IN U-BOOT SLAB, CRACKS ................................................................. 26 TABLE 7: COMPARISON OF QUANTITIES ....................................................................... 27 TABLE 8: COST COMPARISON .......................................................................................... 28 FIG 20: COST COMPARISON BETWEEN A U-BOOT SLAB AND A SOLID SLAB....... 28

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1. INTRODUCTION 1.1 BACKGROUND INFORMATION With the current global economic recession and deterioration of the environment, Engineers and researchers worldwide are seeking to introduce technology that is environmentally friendly and cost efficient. With regard to building technology, efforts are being made to reduce the concrete requirement in construction, increase the load bearing capacity of structures and cut on construction costs.

In case of horizontal slabs, the main obstacle with concrete constructions is the high weight, which limits the span. For this reason major developments in reinforced concrete have focused on enhancing the span, either by reducing the weight or overcoming concrete's natural weakness in tension. Pre-stressed concrete was invented to overcome concrete’s weakness in tension, thereby enabling longer span. To reduce the weight of the slabs, voided slabs were introduced. The voids reduce the amount of concrete in the slab thereby reducing the weight of the slab enabling longer spans to be built. Depending on the method used to create the voids, it may also serve to reduce the cost of construction.

The u-boot formwork is the modular element made of recycled polypropylene for use in building lighter structures in reinforced concrete cast in the work site. This new lighter structure is achieved by enclosing the u-boot within the concrete cast to create voids. Slabs built with u-boot can form the structural elements of various building systems, such as floors, rafts and so on, for both civil and industrial buildings.

Fig 1: Section of slabs with U-boot

S1 and S2 represent the lower and upper concrete layers respectively, while h is the height of the u-boot and Ht is the total slab thickness.

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1.2 POLYPROPYLENE Polypropylene is a thermoplastic polymer, made by the chemical industry and used in a wide variety of applications, including packaging, textiles, stationery, plastic parts and reusable containers of various types, laboratory equipment, loudspeakers, automotive components and polymer bank notes. It is commonly used for plastic moldings where it is injected into a mould while molten, forming complex shapes at relatively low cost and high volume. This process is used to make the u-boot formwork.

The u-boot is made of polypropylene, which unlike polystyrene, is not toxic even if it is burnt. Polystyrene releases toxic styrene monomers at room temperature. Polypropylene is resistant to many chemical solvents, bases and acids, and does not deteriorate with time or lose its characteristics. PP is normally tough and flexible, especially when copolymerized with ethylene. This allows polypropylene to be used as an engineering plastic. Polypropylene is economical and has good resistance to fatigue. It has a melting point of approximately 160oC (320oF).

1.3 ENVIRONMENTAL BENEFITS Benefits associated with the u-boot slab are mainly environmental in nature, the main one being the cutting down on the amount of concrete used in construction. Concrete is the most common construction material used in the world, in fact it is the second most used product on the planet, after water. Cement is the principal ingredient in concrete. The production of one tonne of cement results in the emission of approximately one tonne of CO2, created by fuel combustion and the calcination of raw materials. Cement manufacturing is a source of greenhouse gas emissions, accounting for approximately 7% to 8% of CO2 globally. An additional benefit of the u-boot slab is the reduction of plastic waste in the environment, since the u-boot units are made from recycled plastic. The considerable growth in use of plastics is due to its beneficial properties that include extreme versatility. They are lighter than competing materials, their transportation is easier and cheaper, they are extremely durable, and they have good resistance to chemicals, water and impact, are safe and hygienic for food packaging, possess excellent thermal and electrical insulation properties and are relatively cheaper to produce.

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This has made them popular and the reverse is that more than half of the plastics end up as solid waste, contributing to the biggest challenge to municipal solid waste management all over the world. In view of the magnitude of the plastic waste and the resultant environmental ramifications, the Government has identified plastic waste as a major solid waste problem in urban centers.

1.4 PROBLEM STATEMENT With depleting natural resources, deteriorating environmental conditions and tough economic times, it is important to find construction technology that is environment-friendly and cost effective.

1.5 PROBLEM JUSTIFICATION In an effort to achieve vision 2030, Kenya is trying to keep up with technological developments that are taking place worldwide. In construction industry, we seek to apply methods that save on cost and cement especially with the diminishing quantity of natural resources available. Preservation of the environment is now a key issue in all aspects of life and finding an environmental-friendly technology is of great advantage.

The cement industry has made significant progress in reducing CO2 emissions through improvements in process and efficiency, but further improvements are limited because CO2 production is inherent to the basic process of calcinating limestone. Cement is needed to satisfy basic human needs, and there is no obvious substitute, so there is a trade-off between development and sustainability. In view of these facts, it is important to reduce the environmental impacts of cement production by reducing the quantity of concrete that is used in construction.

The u-boot technology encourages recycling of plastic waste is one approach that has positive ramification in creating informal employment among the youth and offering an environmentally sound solution to plastic waste management.

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1.6 OBJECTIVE 1.6.1 General Objectives To investigate the practicability and benefits of the U-boot technology in Kenya, and establish whether it is necessary to encourage its local production and use in the country.

1.6.2 Specific objectives

•

To find out whether the u-boot slab is cheaper compared to traditional steel reinforced slab used in Kenya.

•

To investigate the amount of concrete reduction that is achieved by use of u-boot slabs and its impact on the environment.

•

To compare the strength characteristics of u-boot slab and traditional slab.

1.7 RESEARCH HYPOTHESIS If the U-boot technology is applied in Kenya, it will save on the cost of construction and help preserve our environment among other benefits.

1.8 LIMITATIONS OF THE STUDY •

Time factor: the time allocated may not be adequate for a comprehensive coverage of the study. That notwithstanding, major effort will be put in place to ensure a comprehensive coverage of the same within the stipulated time.

•

Financial constrain: the funds available may not be sufficient to cater for the financial needs of the study.

1.9 EXPECTATIONS OF THE STUDY The study seeks to determine whether the U-boot slab is appropriate for use in Kenya and the significance it will have. If it is beneficial, its local production and use will be encouraged in the construction work.

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2. LITERATURE REVIEW 2.1 INTRODUCTION Reinforced concrete slabs are used in floors and roofs of buildings and as decks of bridges. Slabs may span in one direction or two directions and may take many forms such as in-situ solid slabs, ribbed slabs or pre-cast units. They can be supported on monolithic concrete beams, steel beams, walls or directly by the structures columns (Morsley, 1990).

While concrete has been used for thousands of years, the use of reinforced concrete is a relatively recent invention, usually attributed to Joseph-Louis Lambot in 1848. Joseph Monier a French gardener, patented a design for reinforced garden tubs in 1868, and later patented reinforced concrete beams and posts for railway and road guardrails.

In his book ‘Concrete slabs, Analysis and design’ (1984), L. A Clark describes developments of reinforced concrete as mainly focusing on enhancing the span, either by reducing the weight or overcoming concrete's natural weakness in tension. Some of the inventions include Pre-stressed concrete, hollow core slabs and waffle slabs.

2.2 PRE-STRESSED CONCRETE Pre-stressed concrete was invented by Freyssinet in 1928 to overcome concrete’s weakness in tension, thereby enabling longer spans. The technique of pre-stressing has several applications in civil engineering but the most common is in pre-stressed concrete where a pre-stress is applied to a concrete member and this induces an axial compression that counteracts all or part of the tensile stress set up in the member by applied loading (Hurst, 1989).

Compared to normal reinforced concrete for a given span and loading, a smaller pre-stressed concrete member is required (Hurst, 1989). This saving of dead load of a structure is particularly important in long span structures such as bridges where dead load is a large proportion of total load. Pre-stressing also helps to save on concrete material for members.

2.3 HOLLOW-CORE SLABS To reduce the weight of the slabs, voided slabs were introduced. Voided slabs reduce the amount of concrete by introducing voids in the slab. This is achieved by removing part of the concrete below the neutral axis, where concrete has a limited effect, and in some cases replacing it with some lighter form of construction. Solid sections are maintained in top and bottom where high stresses can exist. Hence, the slab is fully functional with regards to both positive and negative bending (Morsley, 1990).

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Hollow floor slabs are prefabricated, one-way spanning, concrete elements with hollow cylinders. Due to the prefabrication, these are inexpensive, and reduce building time, but can be used only in one-way spanning constructions, and must be supported by beams and/or fixed walls.

2.4 BI-AXIAL SLABS Due to the limitations in hollow-core slabs, primarily lack of structural integrity, inflexibility and reduced architectural possibilities, focus has been on biaxial slabs and ways to reduce the weight. Several methods have been introduced during the last decades, but with very limited success, due to major problems with shear capacity and fire resistance as well as impractical execution.

For decades, several attempts have been made to create biaxial slabs with hollow cavities in order to reduce the weight. Most attempts have consisted of laying blocks of a less heavy material like expanded polystyrene between the bottom and top reinforcement, while other types included waffle slabs and grid slabs. Of these types, only waffle slabs can be regarded to have a certain use in the market.

2.5 WAFFLE SLAB The waffle slab may be visualized as a set of crossing joists, set at small spacing relative to the span, which supports a thin top slab. The recesses in the slab, often cast using either removable or expendable forms, decrease the weight of the slab and allow the use of a large effective depth without the accompanying dead load. The large depth also leads to a stiff structure. Waffle slabs are generally used in situations demanding spans larger than perhaps about 10m. They may be designed as either flat or two way slabs (Roper, 1991).

However, the use of waffle slabs will always be very limited due to reduced resistances towards shear, local punching and fire. The idea of placing large blocks of light material in the slab suffers from the same flaws, which is why the use of these systems has never gained acceptance and they are only used in a limited number of projects in Spanish-speaking countries.

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2.6 BUBBLE DECK TECHNOLOGY In the 1990s, a new system was invented, eliminating the above problems. The so called Bubble Deck technology invented by Jorgen Breuning, locks ellipsoids between the top and bottom reinforcement meshes, thereby creating a natural cell structure, acting like a solid slab. For the first time a voided biaxial slab is created with the same capabilities as a solid slab, but with considerably less weight due to the elimination of superfluous concrete. However, the ellipsoids are not easy to layout and are not stackable which results in high transportation costs.

Fig. 2: Bubble deck slab

2.7 U-BOOT TECHNOLOGY The u-boot formwork is the modular element made of recycled plastic for use in building lighter structures in reinforced concrete cast in the work site. It has a truncated pyramid shape and a lower base 52 x 52 cm. it is composed of feet, lateral flaps and upper tips used as spacers in order to create alveolar voids in concrete massive slabs. Units need to be laid out on site on predisposed deck or in a factory on a precast slab. They come in element height of 16, 20, 24, 32, 36, 40, 44, 48 cm; feet of 0, 5, 7, 10 cm; flaps of 12, 14, 16, 18, 20 cm.

Axonometric projection

Single u-boot

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Double u-boot

Plan Fig. 3: U-boot unit

In these figures, B represents the width of the u-boot, h is the height and I is the height of the u-boot feet.

The lighter structures is made up of two layers, one on top of the other, separated and connected to each other by a grid of beams at right angles which are formed when the u-boots are put in place. The beams transfer stresses to the pillars of the structure, which allows slabs of long spans to be built. The slabs are able to take high loading and do not need internal beams, a perimeter edge beam is sufficient. All that is needed is to leave a massive area around the column- called mushroom pillar- which is thick as slab and varies on a shear stress basis.

Slabs built with u-boot can form the structural elements of various building systems, such as double floors, floors, rafts and so on, for both civil and industrial buildings. With its high inertia levels, this building system makes it possible to build large scale constructions.

The biggest advantage of the u-boot is that it is stackable. The second innovation is the shape: U-boot creates a grid of orthogonal "I" beams, so the calculation of the reinforcement can be effected by any static engineer according to the Euro code, British standards or local norms.

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Fig. 4: U-boot slab layout

2.8 BENEFITS OF U-BOOT SLAB 1. 2.

The open created by the slab give greater design freedom, and makes change of use easier Reduced amount of concrete in the slab thereby reducing the environmental impacts of cement production.

3.

Reducing the weight of the slab enabling longer spans to be built.

4.

Reduction of plastic waste in the environment, since the u-boot units are made from recycled plastic.

5.

The u-boot slab does not require internal beams. This results in reduced storey heights and smooth ceilings.

6.

The u-boots are light and stackable making them easy to transport, stockpile and layout.

7.

The slab is easy to smooth once the formwork is taken off and if false ceiling is required the layout is faster.

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2.9 RAFT FOUNDATIONS. Amongst foundations of different kinds, raft foundations are the most common. This is due to advantages like high stiffness due to static bi-directional behavior, good load distribution capacity on the ground, it absorbs stresses coming from the building with differential subsidence close to zero and they are easy and quick to layout. When stresses increase or ground bearing capacity decreases, a thick raft foundation is needed. This means more concrete and more pressure on the ground, and therefore building costs increases.

U-boot formwork is designed to create a lightened Fig slab and raft foundations. Once placed in concrete, it creates an alveolar structure, with two slabs of different thickness, linked together by an orthogonal grid of beams of different width. In doing so, an ideal light structure for raft foundations is carried out. Statistically it is considered as a grid of I beams which rationally distributes masses for the purpose of inertia in order to obtain high stiffness with a minimum concrete quantity. In some special cases, foundation piles are not needed due to the combination of lightness and stiffness.

Fig. 5: Section of raft foundation with U-boot

In the figure above, S1 and S2 represents the lower and upper concrete layer respectively, while h is the height of the u-boot and Ht is the total height of the raft foundation.

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2.10

SHEAR REINFORCEMENT OF SLAB

The direction of principal compressive stresses across the span of a homogeneous concrete slab take the form of an arc, while the tensile stresses take the form of a catenary or suspended chain. Towards the mid-span, where the shear is low and the bending stresses are dominant, the direction of the stresses tends to be parallel to the beam axis. Near the supports, where the shearing stresses are greater, the principal stresses are inclined at a steeper angle, so that the tensile stresses are liable to cause diagonal cracking (Morsley, 1990). For this reason, hollow slabs are made solid near the supports and if the slab is supported by a monolithic beam the solid section acts as the flange of a T-section. The slabs are also made solid under partitions and concentrated loads because they cause punching shear.

The main difference between a solid slab and a voided biaxial slab refers to shear resistance. Due to the reduced concrete volume, the shear resistance will also be reduced. Other types of voided biaxial slabs have reduced resistances towards shear, local punching and fire. In practice, the reduced shear resistance will not lead to problems in the u-boot slab, as the units are simply left out where the shear is high, at columns and walls.

According to William L. Gamble and Robert Park (2000), slabs may be divided into two major categories: beamless slabs and slabs supported on beams located on all sides of each panel. There are many hybrid variants, and many otherwise beamless slabs have beams at the edges of the structure and around large openings, such as those made for elevators and stairways.

The u-boot slab is a form of flat, beamless slab as its weight is totally supported directly on columns. The strength of a beamless slab is often limited by the strength in punching shear at sections around the columns. The limited depth of the slabs makes the anchorage of the shear reinforcement difficult. Because of this problem, spearheads of structural steel have been developed for slabs at interior columns.

Spearheads consist of crossing steel arms welded together at a common level, to pick up both some shear and moment load from the concrete. These arms which are totally within the slab thickness pick up shear and moment beyond the column and bring the load to bearing on the column. The bottom flanges of the steel shapes are extended beyond the top flanges to pick up shear load that will exist low in the slab. The critical section for shear on the concrete is thus moved to a larger perimeter (Ferguson, 1979).

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Beams reduce headroom and impose restrictions on the use of space beneath (Oladapo, 1981). The absence of beams results in more spacious rooms with greater architectural freedom and easier change of use. In addition to these advantages, beamless slabs have an economy of formwork and once the formwork is removed the plane surface makes false ceilings unnecessary.

2.11

FIRE RESISTANCE

J. M Davis defines fire resistance as the ability of an element of construction to resist collapse, to resist penetration of flames and hot gasses while at the same time maintaining structural integrity and to keep the unexposed face sufficiently cool so as not to ignite materials in contact with it. Determination of fire resistance involves the exposure of the element to severe standard fire and the resistant time determined used to prevent fire spread from one compartment to another.

The fire resistance is a matter of the amount of concrete layer. The fire resistance is dependent on the temperature in the rebars and hence the transport of heat. As the top and bottom of the u-boot slab is solid, and the rebars are placed in this solid part, the fire resistance can be designed according to demands.

BS 8110 provides tabulated values of minimum dimensions and nominal covers for various types of concrete members which are necessary to permit the member to withstand fire for a specified period of time.

According to some studies carried out by the Polytechnic of Milan, slabs lightened by means of polystyrene explode after only 20 minutes when exposed to fire load. This is due to the presence of warm air in cavities which increases pressure and partially due to styrene sublimation. In order to avoid slab explosions, vents are to be placed into slabs to maintain constant pressure into cavities. CSI laboratories carried out a fire test on a slab lightened by means of u-boot with a 3cm concrete cover and the structure was certified REI 180 minutes.

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2.12

CONCRETE MIX

The u-boot slab requires concrete grade 30 (1:1:2) with a slump of between 150mm-200mm to enable it to flow between the u-boots. This high slump is achieved by using high-range water reducing admixtures (superplastisizers)

Superplastisizers are used to increase the workability of the concrete mix. These are modern types of water reducing admixtures which are very effective. Chemically, they are sulphonated melamine formaldehyde condensates and sulphonated naphthalene formaldehyde condensates. The admixtures are adsorbed on the cement particles, giving them a negative charge which leads to repulsion between the particles and results in stabilizing their dispersion. Air bubbles are also repelled and cannot attach to the cement particles. In addition, the charge causes the development around each particle of a sheath of oriented water molecules which prevent a close approach of the particles to one another. The particles have a greater mobility and water freed from the restraining influence of the flocculated system becomes available to lubricate the mix so that the workability is increased.

At a given water/ cement ratio, this dispersing action increases the workability by raising the slump from 75mm to 200mm. the resulting concrete can be placed with little or no compaction and is not subject to excessive bleeding or segregation. Superplastisizers produce workable concrete with extremely high strength due to the reduction of water-cement ratio (Neville, 1989).

It is important for the flowing concrete mix remains cohesive and suitable for pumping. One way of doing this is to increase the fine aggregate content by 4 to 5 percentage points: and more for very coarse sand. This ensures cohesion and prevents segregation. Another approach involves the adjustment of fines relative to maximum aggregate size and cement content. Some water reducing agents are more effective when used in mixes containing pozzolanas (natural or artificial material containing silica in a reactive form) than in plain mixes.

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3. RESEARCH METHODOLOGY 3.1 INTRODUCTION The study will deal with the design and casting of both the u-boot slab and the traditional steel reinforced slab so as to compare their strength and economic characteristics. In all design calculations, a two way spanning slab panel of dimensions 6m x 8m was used.

3.2 SLAB DESIGN For the purpose of design, a two way spanning slab panel of side 6m x 8m was used. Design procedure was done in accordance to BS 8110 (1997): Part 1, section 3.6. A traditional simply supported reinforced concrete slab, a flat slab and a u-boot slab were designed. The objective of this was to determine and compare dimensions and reinforcement that would be required for the slabs. Bar bending schedules and structural drawings were produced for the slabs.

3.3 U-BOOT FORMWORK The formwork that will be used for the study has lower base 520 x 520 mm. The element height is 160 mm and has 100 mm feet, with 120 mm lateral flaps. This will produce a slab of 260mm thick. However, u-boot elements of different dimensions can be used depending on the structure being constructed and the intended loading.

Fig 6: The u-boot element used for the slab.

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3.4 SIEVE ANALYSIS Sieve analysis test was carried out on the fine and coarse aggregates used to determine the relative proportions of different aggregate sizes as they are distributed among certain size ranges.

A representative sample of the aggregates was taken and weighed. A stack of sieves was prepared, with the sieves having larger opening sizes being placed above ones with smaller opening sizes. The aggregate was poured onto the stack of sieves from the top and shaken. The mass of the aggregate retained in each sieve was taken and the data collected was tabulated.

Fig 7: Sieve arrangement

3.5 SLUMP TEST A slump test was carried out to determine the workability and consistency of the concrete used for casting the slabs.

First, one third of the slump cone was filled with concrete then tamped 25 times using a steel rod. More concrete was added to the two thirds mark and the taming was repeated as before. The whole cone was then filled up with excess concrete and tamped again 25 times. The excess concrete was removed from the top of the cone using a rolling motion of the tamping rod until flat. The cone was then slowly lifted and the concrete was allowed to slump. After it had stabilized, its height was measured. This was done for six samples and the results were tabulated.

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3.6 U-BOOT LAYOUT First, a flat and complete surface was prepared with a wooden deck. Then inferior steel reinforcement was laid out in the two orthogonal directions as designed. Lattices were then placed in order to space out upper reinforcements.

Afterwards, the u-boot was put in place. The u-boots’ cone shaped feet raise them above the lower surface and concrete can therefore be cast to fill the lower slab. Upper bending steel bars were placed in two directions- shear and punching reinforcement- to complete reinforcement.

The concrete grade 30 (1:1:2), with a water-cement ratio of 0.6 was used for the slab. An admixture (superplasticizer) was used to achieve a slump of between 150mm-160mm to enable the concrete to flow between the u-boots. The slump test was carried out on the concrete that was used for the casting of the slab to detect variations in the uniformity of the mix.

Due to the floating pressure exerted on the u-boots, concrete was cast in two different phases. In the first phase, a thickness equal to feet height was filled and compacted. The second casting was carried out only when the first concrete layer began to set. Finally the casting was leveled up in the traditional way.

Fig 8: Casting of the u-boot slab

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Fig 9: Curing of the u-boot slab

3.7 SOLID SLAB First, the formwork was prepared with using timber. Then steel reinforcement was laid out in the two directions as designed. The concrete grade 30 (1:1:2), with a water-cement ratio of 0.6 was also used for the slab. An admixture (superplasticizer) was used to achieve a slump of between 150mm-160mm. The slump test was carried out on the concrete that was used for the casting of the slab to detect variations in the uniformity of the mix. The concrete was put in layers and compacted using a poker vibrator. Finally the casting was leveled up in the traditional way.

Fig 10: Curing of the solid slab

17

3.8 STRENGTH TESTS Concrete cubes were cast alongside the u-boot slab and then subjected to crushing under compression in order measure the concrete strength in its hardened state to ensure that it was above the minimum strength specified.

For this test, the cube moulds of 150mm sides where cleaned and a thin layer of oil was applied on their inner surface. A sample of the concrete was placed in the cubes in three layers of equal depth and each layer was compacted by a poker vibrator. The surface was then leveled off using a trowel. The cubes were labeled and after 24 hours they were transferred to a curing tank. The cubes were allowed to cure for 28 days after which they were tested on a cube crushing machine.

Fig 11: Compressive test

18

For the slabs tests, the slab center was marked after the slab was put in place. A sensor was fixed on the side of the slab to sense the strain and a transducer was fixed to measure the deflection. A hydraulic jack was used to apply a point load at the center of the slab and a data logger produced the output. The loading applied was gradually increased to a point where cracks developed. The loading at this point was noted then increased again to a point of complete failure. The setup for the experiment was as shown below.

Fig 12: Slab testing

3.9 MEASUREMENT OF QUANTITIES The measurement of material quantities for the slabs was done in accordance to the Civil Engineering Standard Method of measurement. This was done for the sake of comparison. A bill of quantities was prepared for concrete, reinforcement steel, and formwork and expressed in monetary terms, according to the current market prices.

19

4. RESULTS AND DISCUSSION 4.1 SIEVE ANALYSIS From the sieve analysis test, the mass of the aggregate retained in each sieve was taken and the data collected was tabulated as shown below. From the above graphs it can be seen that both the fine and the coarse aggregates are uniformly graded meaning that the aggregates are of approximately the same size.

Fine aggregate grading Wt.

Wt.

retained

passing

(g)

(g)

5.00

42.00

1485.50

2.75

2.75

97.25

2.00

45.50

1440.00

2.98

5.73

94.27

1.18

219.00

1221.00

14.34

20.07

79.93

0.60

385.00

836.00

25.20

45.27

54.73

0.30

560.00

276.00

36.66

81.93

18.07

0.20

220.50

55.50

14.44

96.37

3.63

0.10

55.50

0.00

3.63

100.00

0.00

Total

1527.50

Sieve sizes (mm)

% retained

Cumulative % retained

% passing

Table 1: Fine aggregate grading

20

FINE FINEAGGREGATE AGGREGATEGRADING GRADING

cum ilative % passing cum ilative % passing

120 120 100 100 80 80 60 60

Series2 Series2

40 40 20 20 0

0

0.1 0.1

0.2 0.2

0.3 0.6 1.18 0.3 0.6 1.18 Sieve sizes Sieve sizes

2

5

2

5

Fig 13: Graph of table 1

Coarse aggregate grading Sieve

Wt.

Wt.

sizes

retained

passing

(mm)

(g)

(g)

20.00

1250.00

3362.50

27.10

27.10

72.90

14.00

992.00

2370.50

21.51

48.61

51.39

10.00

1672.50

698.00

36.26

84.87

15.13

5.00

653.50

44.50

14.17

99.04

0.96

2.36

35.00

9.50

0.76

99.79

0.21

1.18

9.50

0.00

0.21

100.00

0.00

Total

4612.50

% retained

Cumulative % retained

% passing

Table 2: Coarse aggregate grading

21

Coarse aggregate grading Coarse aggregate grading

% P assin g % P assin g

80 80 70 70 60 60 50 50 40 40 30 30 20 20 10 10 0 0

Series2 Series2

1.18 1.18

2.36 2.36

5

10 5 10 Sieve size Sieve size

14 14

20 20

Fig 14: Graph of table 2

4.2 SLUMP TEST The results of the slump test were tabulated as shown below. From the table, we see that the concrete mix was of uniform consistency with a slump varying between 150mm to 160mm. this homogeneity improves the quality and structural integrity of the cured concrete. Average slump for the concrete mix was 155mm.

SLUMP TEST RESULTS Sample no.

Slump (mm)

1

155

2

157

3

160

4

154

5

150

6

156 Table 3: Slump test.

22

4.3 COMPRESSIVE STRENGHT TEST The data obtained for the compressive test was as tabulated below. The compressive strength of the concrete varied between 29.04 N/mm2 and 32.36 N/mm2 which was suitable for the specified concrete strength of 30 N/mm2. Ideal density for cured concrete is 2360 Kg/m3. The density obtained for the cubes varied between 2315.33 Kg/m3 and 2565.60 kg/m3, with the average density being 2393.59 Kg/m3. Average compressive strength for the concrete cubes was 29.98 N/mm2.

CUBE TEST RESULTS (28 day strength)

Sample

Mass

Ave. Cube

Area

Volume

No.

(Kg)

dimensions

(mm2)

(mm3)

Ultimate load (KN)

Density (Kg/m3)

Compressive strength (N/mm2)

1

8.225

152

23104

3511808

67.1

2342.18

29.04

2

8.546

154

23716

3652264

70.2

2339.97

29.60

3

8.659

150

22500

3375000

72.8

2565.60

32.36

4

8.456

154

23716

3652264

71.4

2315.33

30.11

5

8.562

153

23409

3581577

68.8

2390.68

29.39

6

8.456

152

23104

3511808

67.9

2407.76

29.39

Table 4: Compressive strength test

23

4.4 SLAB TEST RESULTS As the loading on the slabs was gradually increased, the values of the deflection and the strain was recorded and tabulated as shown below. SOLID SLAB LOADING Load Load Reading (µ) (t) 50 106 146 207 262 313 371 420 479 540 590 642 702 751 810 865

0 56 96 157 212 263 321 370 429 490 540 592 652 701 760 815

0.00 1.01 1.73 2.83 3.82 4.73 5.78 6.66 7.72 8.82 9.72 10.66 11.74 12.62 13.68 14.67

Reading 17 31 45 64 78 93 108 121 137 153 166 181 199 215 235 255

DEFLECTION Deflection Deflection (µ) (mm) 0 14 28 47 61 76 91 104 120 136 149 164 182 198 218 238

0.00 0.55 1.09 1.83 2.38 2.96 3.55 4.06 4.68 5.30 5.81 6.40 7.10 7.72 8.50 9.28

STRAIN Strain Reading (µ) 9 20 26 39 51 60 70 83 99 120 144 174 212 244 285 334

0 11 17 30 42 51 61 74 90 111 135 165 203 235 276 325

Table 5: Solid slab test results

U-BOOT SLAB LOADING Load Load Reading (µ) (t)

Reading

DEFLECTION Deflection Deflection (µ) (mm)

STRAIN Strain Reading (µ)

38 100 153 202 265 317 374 425 488 539 593 662 708 755 849

0 62 115 164 227 279 336 387 450 501 555 624 670 717 811

0.00 1.12 2.07 2.95 4.09 5.02 6.05 6.97 8.10 9.02 9.99 11.23 12.06 12.91 14.60

26 54 78 98 126 144 163 181 199 217 233 255 271 291 358

0 28 52 72 100 118 137 155 173 191 207 229 245 265 332

0.00 1.09 2.03 2.81 3.90 4.60 5.34 6.05 6.75 7.45 8.07 8.93 9.56 10.34 12.95

6 9 12 18 28 35 43 46 31 16 10 8 8 10 4

0 3 6 12 22 29 37 40 25 10 4 2 2 4 -2

891

853

15.35

372

346

13.49

5

-1

Table 6: U-boot slab test results

24

Fig 15: Deflection curves for the solid and u-boot slabs

Fig 16: Strain curves for the solid and u-boot slabs

The value of deflections recorded for the two slabs was plotted against the loading applied to the point of failure. The solid slab failed at a loading of 56.7 KN while the u-boot slab failed at a loading of 79.5KN. Even though the u-boot slab was able to take higher loading, its deflection was more than that of the solid slab as indicated in the graph above. The strain curves for the two slabs show that the solid slab had higher strain values compared to the u-

25

boot slab, which indicated more deformation. From the figures below we notice that the solid slab had more extensive cracks than the u-boot slab. From the test, it was concluded that the strength properties of the u-boot slab were better than those of the solid slab.

Fig 17: Failure in solid slab, cracks

Fig 18: Failure in solid slab, shear

Fig 19: Failure in u-boot slab, cracks

26

4.5 QUANTITIES

COMPARISON Solid slab

U-boot slab

Concrete (m3)

12.42

11.2

Formwork (m2)

68.25

56.86

Steel reinforcement (Kg)

1614

1597

Table 7: Comparison of quantities 4.5.1

CONCRETE

Data obtained from the measures of quantities (Appendix 4) shows that for the slab panel chosen for design and for the given loading the u-boot slab requires less concrete than the solid slab with internal beams. The difference of concrete used was 1.1 m3 which amounts to a saving of 8.76% of concrete when u-boot slab is used in place of a solid slab with internal beams. This translates to a reduction of 0.653 tonnes of carbon dioxide produced through the process of cement production. For an entire structure, this reduction in carbon dioxide released to the atmosphere is significant in conserving the environment. In cases where a solid flat slab is required for the same loading and span, the saving in concrete is increased to about 25% as the thickness of the flat slab is more than that of a slab with internal beams (Appendix 1- flat slab design). 4.5.2

STEEL REINFORCEMENT

The difference in the quantity of steel used for the two slabs was not significant. The steel reinforcement for the u-boot slab was less than that for the solid slab by 1.1% 4.5.3

SPAN COMPARISON

At the design stage, different spans of the slab were tried. The design of the u-boot slab was possible for spans as high as 18m, with an increase of the slab thickness. This is up to 50% further than traditional structures. This makes the u-boot slab ideal for building slabs of big spans with a high bearing capacity and is suitable for structures that require significant open spaces like industrial or commercial buildings. Design of the solid slab failed for spans greater than 8m.

27

4.5.4

ECONOMIC FEASIBILITY ANALYSIS

Cost comparison (Ksh) Solid slab

U-boot slab

Concrete

121,716

111,054

Formwork

31,800

24,928

Steel reinforcement

193,680

191,640

Labour

41,664

48,607

U-boots

-

34,200

Total cost

388,860

410,429

Table 8: Cost comparison

200000 180000 160000 140000 120000 100000 80000 60000 40000 20000 0

solid slab u-boot slab

steel

formwork

Fig 20: Cost comparison between a u-boot slab and a solid slab The total cost of materials used for the u-boot slab is higher than that used for an equivalent solid slab by Ksh 14,262, which is 4.2% higher. This higher cost is due to the acquisition of the u-boot units which currently have to be imported. The cost of the 76 u-boot units required for the slab panel is Ksh 34,200, which includes the cost of importation. This can be reduced if in future the u-boots are produced locally, and since they are produced from recycled materials the cost will be reduced significantly. The cost of labour is also slightly higher for the u-boot slab and this is attributed to the extra input in laying out the u-boots and placing of the upper reinforcement. The cost of all other materials is lower for the u-boot slab which implies that this method of construction can be more economical in future with local production of the u-boot units.

28

5. CONCLUSION AND RECOMMENDATIONS From the study, it was found that the use of u-boot slab resulted in a saving of concrete of about 10%, and up to 25% decrease in carbon dioxide emissions when compared to a solid slab with internal beams. The u-boot slab was also found to have bigger spans of up to 18m, while solid slabs had a maximum span of 9m for a given load. For fixed spans the u-boot slab had a higher bearing capacity compared to solid slabs. A comparison of the total cost for the two slabs showed that the cost of u-boot slab was higher by 4.2%.

Additional benefits of the flat u-boot slab over the beam and slab floor include the simplified formwork and the reduced storey height. Windows can extend up to the underside of the slab and there are no beams to obstruct the light and circulation of air. The absence of sharp corners gives greater fire resistance as there is less danger of the concrete spalling and exposing the reinforcement. The u-boots are light and stackable making them easy to transport, stockpile and layout. The u-boot is recommended for slabs with high loading, with live loads of 5kN/m2 and above and where large open spaces are required. Use of the u-boots is also encouraged because it is environmentally green and sustainable as it results in reduced energy & carbon emissions. To cut down on costs of acquiring the u-boots, it was recommended that local production of the units should be considered. This will result in reduced plastic waste in our environment and also create employment opportunity in the production industry.

29

BIBLIOGRAPHY 1.

Corley, W. G. (1968). Spearhead reinforcement for slab. ACI, 65 , 14.

2.

Ferguson, P. M. (1979). Reinforced concrete fundamentals, fourth edition.

3.

Gamble, W. L. (2000). Reinforced concrete slabs. John Wiley & Sons.

4.

Hanson, N. W. (1968). Shear and moment transfer between concrete slabs and columns. PCA research and developement laboratories , 10.

5.

Hurst, M. K. (1989). Pre-stressed concrete design. Chapman and Hall.

6.

J, C. R. (1984). Concrete slabs analysis and design. Elsevier applied science publishers.

7.

karger-Kocsis, J. (1995). Polypropylene copolymers and blends. Technology and engineering.

8.

Morsley, W. (1990). Reinforced concrete design. Macmillan press LTD.

9.

Neville, A. (1989). Concrete Technology.

10. Oladapo, O. (1981). Fundamentals of the design of concrete structures. Evans brothers LTD. 11. Roper, D. C.-A. (1991). Concrete structures. Longman publishers.

30

APPENDIX APPENDIX 1: DESIGN CALCULATIONS U-boot slab calculations Slab dimensions Long span= 8m Short span=6m Imposed load= 5kN/m2 Finishes= 0.5kN/m2 Number of u-boots in slab= 76 U-boot dimensions: 0.52 x 0.52 x 0.16 Volume of void in slab: 0.52 x 0.52 x 0.16 x 76 = 3.288 m3 Volume of slab: 8 x 6 x 0.26 = 12.48m3 Volume of concrete in slab: 12.48 – 3.288 = 9.192 m3 Slab self weight: 24 kN/m3 x 9.192 = 220.608 kN Finishes: 0.5 kN/m2 x 48 = 24 kN Live load: 5 kN/m2 x 48 = 240 kN Ultimate load: 1.4(220.608 + 24) + 1.6(240) = 726.451 kN Moments: 0.083 x 726.451 x 8= 482.364 kNm Shear: Edge column: 0.45 x 726.451 = 326.903 kN First interior support: 0.6 x 726.51 = 435.906 kN

31

BEAM LOADING - U-BOOT SLAB Beam A Dead load Slab: 235.152/ (8 x 6) x (3 – (6/8)2) = 4.899 kN/m Self weight: 0.5 x 0.3 x 24 = 3.60 kN/m Total = 15.544 kN/m Imposed load = 12.19 kN/m

Beam 1 Dead load Slab: 235.152 / (8 x 6) x 6 /3 = 9.798 kN/m Self weight = 3.60 kN/m Total loading = 13.3 kN/m Imposed load = 10 kN/m

32

BEAM LOADING – SOLID SLAB Beam A Dead load Slab: 4.7 x 6 (3 – (6/8)2) / 6 = 11.459 kN/m Self weight: 0.45 x 0.30 x 24 = 3.24 kN/m Total dead load = 14.70 kN/m Imposed load 5 x 6 (3 – (6/8)2) / 6 = 12.19 kN/m

Beam B Dead load Slab: 11.459 x 2 = 22.918 kN/m Self weight: 0.55 x 0.30 x 24 = 5.28 kN/m Total = 28.198 kN/m Imposed load 12.9 x 2 = 24.38 kN/m

Beam 1 Dead load Slab: (4.7 x 6) / 3 = 9.40 kN/m Self weight = 3.24 kN/m Imposed load (5 x 6) / 3 = 10 kN/m Beam 2 Dead load Slab: 2(4.7 x 6) / 3 = 18.8 kN/m Self weight = 5.28 kN/m Imposed load 2(5 x 6) / 3 = 20 kN/m

33

APPENDIX 2: STRUCTURAL DRAWINGS

34

APPENDIX 3: BAR BENDING SCHEDULES

35

APPENDIX 4: MEASUREMENT OF QUANTITIES & BILL OF QUANTITIES

36

MEASUREMENT OF QUANTITIES- SOLID SLAB Item

Quantity

Units

Provision of concrete grade 30 (1:1:2), 20mm

1

8.000

aggregate in slab 175mm thick

6.000 0.175

Provision of concrete grade 30 in beam 1 & 2,

2

450 x 300 mm

0.450

1

(450 x 300) mm

1.62

8.000 0.450 0.300

Provision of concrete grade 30 in beam B,

8.4

6.000

0.300 Provision of concrete grade 30 in beam A ,

Total

1

(550 x 300) mm

1.08

8.000 0.550 0.300

1.32

High yield strength steel bars R8

27

12

324

Y10

22

12

264

Y12

74

12

888

Y16

4

12

48

Y20

15

12

180

Formwork, fair finish, plane horizontal

1

8 6

Formwork, fair finish, plane vertical

2

6.000 0.450

1

1.65

8.000 0.275

1

4.4

6.000 0.275

1

3.6

8.000 0.550

2

5.4

8.000 0.450

1

48

2.2

8.000 0.375

3.0

37

MEASUREMENT OF QUANTITIES- U-BOOT SLAB Item

Quantity

Provision of concrete grade 30 (1:1:2), 20mm

1

Units

Total

aggregate in slab 260mm thick (hollow) 9.322 Provision of concrete grade 30 in beam 1

1

(450 x 300) mm

6.000 0.450 0.300

Provision of concrete grade 30 in beam A ,

1

(500 x 300) mm

0.81

8.000 0.500 0.300

1.2

High yield strength steel bars R8

34

12

408

Y10

76

12

912

Y12

60

12

720

Y16

3

12

36

Y20

6

12

72

Formwork, fair finish, plane horizontal

1

8 6

Formwork, fair finish, plane vertical

1

8.000 0.500

1

2.7

0.240 8.000

1

4

0.450 6.000

1

48

1.92

0.04 6.000

0.24

38

SOLID SLAB BILL OF QUANTITIES QUOTATION

Item

No.

Description

Qty

Unit

Rate

Amount

(All Provisional)

Concrete works Vibrated

Reinforced

Concrete

mix

(1:1:2) as described in : -

A

175 mm thick slab

8.4

C.M

9,800

82,320

B

Beams (450 X 300)

2.7

C.M

9,800

26,460

C

Beams (500 X 300)

1.32

C.M

9,800

12,936

Sawn formwork as described in :

C

Soffits of slab

48

S.M.

400

19,200

D

Edge of slab 175 mm high

4.9

S.M

400

1,960

E

Beams

26.6

S.M

400

10,640

1614

K.G.

120

193,680

Reinforcement

F

Assorted reinforcement

TOTAL

FOR SLAB CARRIED TO

SUMMARY

347,196

39

U-BOOT SLAB BILL OF QUANTITIES QUOTATION Item

Description

No. Qty

Unit

Rate

Amount

260 mm thick u-boot slab (hollow)

9.322

C.M

9,800

91,356

B

Beam (500 X 300)

1.2

C.M

9,800

11,760

C

Beam (450 X 300)

0.81

C.M

9,800

7,938

(All Provisional) Concrete works Vibrated Reinforced Concrete mix (1:1:2) as described in : A

Sawn formwork as described in

C

Soffits of slab

48

S.M.

380

18,240

D

Edge of slab 260 mm high

7.28

S.M

380

2,766

E

Beams

10.32

S.M

380

3,922

Assorted reinforcement

1597

K.G.

120

191,640

U-boot units

76

No.

450

Reinforcement

F

34,200

TOTAL FOR SLAB CARRIED TO SUMMARY

361,822

40

BUDGET Item 1

Field work Cost

2

Stationery, photocopying/printing, Binding

Cost 2,000

1,500 3

Labour

1,500

4

Materials

4,000

5

Contingencies

1,000

Total Budget

10,000

41