M 2008 CEET 28 ZIRIMWABAGABO Leodomir GS20020131.pdf

8/21/2019 M 2008 CEET 28 ZIRIMWABAGABO Leodomir GS20020131.pdf

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PROJECT ID: CEET/ 07/48

KIGALI INSTITUTE OF SCIENCE AND TECHNOLOGY

INSTITUT DES SCIENCES ET DE TECHNOLOGIE DE KIGALI

Avenue de l’ Armée, B.P. 3900 Kigali, Rwanda

FACULTY OF ENGINEERING

DEPARTMENT OF CIVIL ENGINEERING AND ENVIRONMENTAL TECHNOLOGY

A PPROJECT

ON

submitted by

ZIRIMWABAGABO LEODOMIR

Under the Guidance of

Mr. KAYINAMURA FRANCIS

Submitted in partial fulfillment of the requirements for the award of

BACHELOR OF SCIENCE DEGREE IN

CIVIL ENGINEERING AND ENVIRONMENTAL TECHNOLOGY

FEBRUARY 2008

“ Comparison between concrete

blocks and bricks from Ruliba”


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CHAPTER I : 1.0 : INTRODUCTION.

1.1: Statement of problem.

At the beginning as history tell it, people lived in a primitive way. They lived in caves

and later small communities were developed and shelters were put up. At that time,

natural building materials was easily available and have been used as the technology in

construction of buildings were developed.

Although, clay bricks and concrete blocks are improved in order to obtain safe and

esthetic locations, their price are not affordable for every one. Since, raw materials for

manufacturing building materials are cheap and rise day to day. For instance, one bag of

Portland cement (50kg) was being bought at 5,000rwf ten years ago, but now costs

13,000rwf . It means that, this increases 10% every year.

Similarly, labor cost increases for a considerable rate. In addition, cutting trees for firing

ceramic materials damages our forest which leads to environmental problems, and as a

result, the sustainable development is not ensured.

1.2 : Objectives of study.

Due to cheapness of building materials and the environmental problems due to

deforestation , this project intends to achieve the following objectives :

• To facilitate the community to select required structural materials in terms of

stability, economy and esthetic;

• To learn which type of structural materials can be used to improve engineering

structure at reasonable price;

• To decide what kind of structure to make;

• To minimize the deforestation rate due to cutting trees for firing the bricks;

• To make sure the safety of the building and to give a good appearance to a

building;

• To enable individual to be familiar with before hand the outlay of the work.


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1.3: Justification.

The Engineering sector is in position to discover which bricks or blocks available in plenty, which can be utilized to put up the building structure of acceptable qualities, with

low cost, thus necessitate the making comparison between concrete blocks and bricks

from Ruliba, which are current building materials mostly used in Rwanda.

It is not easy to decide which kind of structural materials to use in construction because

of different building material made by diverse organizations which appear on market.

Generally, some people prefer to use little cost structural material without consideration

of other necessary properties. In fact, diverse factors should be considered such as

economics, structural and environmental factors.

Moreover, rural and urban communities have no required knowledge about building

structure. For that matter it is important to inform them on structural blocks and bricks

commonly available on market like concrete blocks and Ruliba bricks.

One of the government policy is to protect the environment by reducing the deforestation

velocity due to use of timber in various purposes. Then, the production of ordinary bricks

was reduced.

As a solution, it is time to give the information on modern structural bricks and blocks

which complete engineering requirements. The building development requires the

construction of apparent building. For achieving this purpose it necessary to be familiar

on face bricks most used in construction of houses like Ruliba bricks compared to

concrete blocks.


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1.4 : Scope of study.

This study was conducted on manufacturing place as well as site of construction where

bricks and blocks are considered as basic building materials. It includes the cost, some

properties and technical specifications necessary to achieve the project.

As the basic of this topic is Ruliba bricks and concrete blocks, that is reason why some

experiments like laboratory test was conducted as well as considerable readings in

relation to the topic was proceeded to compare the cost and the strength of both.


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CHAPTER II. 2.0 : LITERATURE REVIEW.

2.1 : Varieties of bricks and blocks.

Bricks may be defined as small a cored building unit of rectangular shape that is

composed of organic non-metallic substances of mineral origin hardened by heat or

chemical action. Blocks are similar defined but have larger dimensions than that of

bricks. Blocks are larger than bricks.

2.1.1 : Clay bricks.

Clay bricks like other ceramic products are based on clay, to which various amount of

quartz and feldspar have been added. Selected proportions are mixed with water, shaped,

dried and fired to produce the structural clay products of brick, roof and structural tiles

etc.

Types of bricks.

Bricks of masonry units may be solid, hollow, or architectural terra cotta. All types can

serve a structural function, a decorative function, or a combination of both. The various

types differ in their formation and composition.

Building bricks.

Also called common or hard bricks, are made from ordinary clay and are fired in kilns.

These bricks have no particular shoring, markings, surface texture, or color. Because

building bricks are generally used as the burning courses in either solid or cavity brick

walls, the harder and more durable type are preferred.


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Face bricks.

Face bricks are of better quality and has better durability and appearance than structural

brick. Because of this, face bricks are used in exposed wall faces. The most common face

brick colors are various shades of brown, red, gray, yellow, or white.

Clinker brick.

Clinker brick is over burned in the kiln. Clinker bricks are usually rough, hard, durable,

and sometimes irregular in shape.

Pressed brick.

Pressed brick is made by a dry-press, rather than by kiln firing. Pressed brick have

regular, smooth faces, sharp edges, and perfectly square corner. Normally, they are used

like face brick.

Glazed Brick.

Glazed brick has one surface coated with a white or colored ceramic glazing. The glazing

forms when mineral ingredients fuse together in glasslike coating during burning. Glazed

bricks are particularly suited for walls or partitions in hospitals, dairies, laboratories. And

other structures requiring sanitary conditions and ease of cleaning.

Fire brick.

Fire brick is made from a special type of clay. This clay is very pure and uniform and is

able to withstand the high temperatures of fireplaces, boilers, and similar constructions.

Fire bricks are generally larger than other structural bricks and are often hand-molded.


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2.1.2 : Calcium silicate bricks.

Raw materials: Siliceous aggregate, a high calcium lime and water; very fine aggregate

:1.15 mm sieve.

Size: 215 x 102.5 x 65 mm

Density:1700 kg/ m3

Strength:14-27.5 N/mm2

2.2 : Bricks forming process.

2.2.1 : Manufacture process.

After raw clay has been screened and crashed, machine-made bricks are formed either by

extrusion and cutting, or by pressing. Plastic clays may be extruded as continuous column

of rectangular section (with or without perforations) which is cut into individual bricks by

wire, acting like a chisel cutter, as it emerges from the die.

2.2.2 : Firing.

Firing transforms the raw clay brick into a rigid continuous (although usually porous

ceramic by way of a complicated succession of physical and chemical changes. Water is

lost rapidly as the kiln temperature rise above 1000C.

The clay minerals decompose between 400 and 7000 c. At about 900

0C crystalline silica,

alumina and spinel compounds appear and the mineral mullite 3Al2O32SiO2 forms above

about 10000

C.

The minor oxide constituents include Na2O, K 2O, MgO, CaO, and FeO produce relatively

low melting eutectic mixtures with principal components of SiO2 and Al2O3, so that some

melting may occur below 10000C.


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2.3 : Technical specification of bricks.

2.3.1: Strength of bricks.

Bricks often have to withstand great compressive stresses. The durability of the masonry

depends upon the strength of the bricks. Common building bricks should have a

minimum strength of 35 kg/cm2 . Also, the compressive strength of any individual brick

should not fall below the average compressive strength specified for the corresponding

class of brick by more than 20% .

The average compressive strength of common burnt clay bricks is given

in table 2.1.

Class

designation

Average

strength not

less than

kgf/cm2

(N/mm2) Compressive

strength less

than kgf/cm2

(N/mm2)

350

300

250

200

175

150

125

100

75

50

35

350

300

250

200

175

150

125

100

75

50

35

(35)

(30)

(25)

(20)

(17.5)

(15)

(12.5)

(10)

(7.5)

(5)

(3.5)

400

350

300

250

200

175

150

125

100

75

50

(40)

(35)

(30)

(25)

(20)

(17.5)

(15)

(12.5)

(10)

(7.5)

(5)

Table 2.1:Average compressive strength of common burnt clay bricks. IS :1077- 1976.


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2.3.2: Test for compressive strength.

The specimen brick is immersed in water for 24 hours. The frog of the brick is filled flush

with 1:3 mortar and the brick is stored under damp jute bags for 24 hours followed by

immersion in clean water for three days. The specimen is then placed between the plates

of compression testing machine.

Load is applied axially at a uniform rate of 14N/mm2(140Kg/cm

2) and the maximum load

at which the specimen fails is noted for determination of compressive strength of brick

given by:

Compressive strength = Maximum load at failure/Loaded Area of bricks (Average of

five results shall be reported).

2.3.3: Compressive strength and other mechanical properties.

The compressive strength is the only mechanical property used in brick specification. It is

the failure stress measured normal to the bed face. Bricks are tested wet, normally with

frogs filled with hardened mortar. A considerable variation is found between individual

bricks and a batch of ten is tested to obtain a mean strength.

Generally, compressive strength decreases with increasing porosity, but strength is also

influenced by clay composition and firing. The compressive strength is limited by brittle

fracture and is sensitive to individual flows in the sample under test, including those

associated with large particles, fissures formed during shaping, and shrinkage cracks. The

young’s modulus of elasticity of brick ceramic lies usually in the range 5 to 30KN/mm2.


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2.3.4: Factors affecting compressive strength.

Arnold W. Hendry in structural masonry (1998) have stated the important factors in

determining the compressive strength of masonry as follow:

1. Unit characteristics: Strength; type and geometry like solid, perforated, hollow,

relative height; absorption.

2. Mortar characteristics: Strength developed by mix, water/ cement ratio, water

retentivity; relative deformation and relative thickness.

3. Masonry: Bond; direction of stressing; local stress.

Some of these factors, such as the unit characteristics, are determined in the

manufacturing process, while others, such as mortar properties, are susceptible to

variations in constituent materials, proportioning, mixing and accuracy of construction.

2.3.5: Size of bricks.

The International Standard states that the length of brick should be equal to two

times width plus one joint size of 10mm. So that, the length = 2width+1 joint. Most

commonly used bricks format are 215x102,5x65mm and 210x100x63mm with

mortar joints of 10mm the size becomes respectively 225x112,5x75mm and

220x110x73mm.


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2.4: Concrete blocks features.

2.4.1: Concrete block technology.

Concrete block technology offers a speedier, cost effective, environmentally sound

alternative to conventional walling materials like bricks, stones, compressed earth blocks,

etc... It is based on the principle of densification of a lean concrete mix to make a regular

shaped, uniform high performance masonry unit.

Concrete block technology can be easily adapted to suit special needs of users by

modifying design parameters such as mix proportion, water/cement ratio and type of

production system. It is an effective means of utilizing wastes generated by stone

crushers, quarrying and stone processing units. The technology has high potential in areas

where raw materials are easily available.

2.4.2: Business.

The concrete block technology package is a highly profitable business for micro and

small scale building material producers and construction companies. The market for

concrete blocks is growing at a rapid rate, specially in the areas where burnt bricks are

not easily available or are of poor quality.

2.4.3: Product.

The specifications and the characteristics of a concrete block depend on the machine usedto manufacture concrete blocks. The most common size of solid concrete blocks is

300x200x150mm. The basic raw material is cement, fine aggregate and coarse aggregate.

Very little water is used. This is possible only with mechanized compaction and vibration

and gives the block high quality in spite of the lean mix, which uses very little cement.


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Weight of a concrete blocks can be surface engineered by using pieces of stone or

ceramic waste on their face. Another common type are hollow concrete blocks. They are

made with a richer mix, but offer a number of advantages, such as lighter weight, easier

handling and facility for conducting or reinforcement through the hollows.

2.4.4: Unique features of concrete block technology :

• Cost effective compared to other traditional walling systems

• Maximum utilization of stones wastes and local resources

• Structural performance can be engineered

• Decentralized local production

• Offers business opportunities

2.4.5: Production process.

Concrete blocks are usually produced using a semi-mechanized stationary type machine.

The other production systems are-manual moulds which require hand tamping, a mobile

semi-mechanized egg-laying machine and fully mechanized system which combines

compression and vibration.

High quality machines provide optimum vibration in the mix so that the ratio of cement

used can be reduced substantially without compromising on the strength of the blocks.

The machine also compacts and consolidates the mix so that the blocks are uniform in

size and attain desired physical properties.

The blocks are cured for a minimum period of 14 days, before they are ready to use. On

an average 600-800 blocks can be made in 8 hours by 1 skilled and 6-8 semi-skilled

workers.


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2.4.6:Building with concrete blocks.

Concrete blocks can be used like any other masonry unit to build foundations, walls,

arches and corbels, etc. A typical concrete block is equivalent to 4.5 bricks, thusconstruction is faster than with other masonry units. The mortar used is also less which

results in cost saving. They are compatible with other materials like fired bricks, dressed

stone and compressed earth blocks for composite wall construction.

Acceptability of concrete blocks is very high in urban areas for all types of buildings.

They are very popular as a long lasting, low maintenance and investment for institutional

and industrial buildings. The permanence of a cement based product is making concrete

blocks a preferred choice in rural areas as well.

2.4.7: Perforated and hollow block units.

A number of investigators have studied the effect of different types of units on

compressive strength and an extensive series of tests were undertaken by West et Al. at

the British Ceramic Research Association to examine the compressive strength of

brickwork built with a variety of wire-cut bricks having different hole patterns with

perforation ratios up to 20 per cent.

The results of these tests showed that if the brickwork strength was calculated on the

basis of a standard crushing test on the unit, the perforation pattern made little practical

difference. In these tests, the perforations were either circular holes or slots with round

ends, but in some tests reported by Monk the units had rectangular slots, and these tests

showed reduced compressive strength in prisms. It would seem probable that such slots

would introduce stress concentrations, not only in service but also in manufacture, which

would be a source of weakness.


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Schellbach has examined the strength of various types of highly perforated units and has

found that the highest ratio of masonry strength to unit strength was obtained with a

perforation ratio of 38-43 per cent. Schellbach’s study included examination of stress

concentration factors associated with different perforation patterns, and he concluded that

these remain within acceptable limits even with rectangular slots, provided that the

corners are well rounded.

Hollow block masonry may be built with the cores either unfilled or filled with concrete .

In the former case the mortar joint may cover the whole of the bed face of the block (full-

bedded) or only the outer shells (face-shell-bedded). These different construction

methods result in considerable variations in structural behavior and this quite clearly

results in a more complex situation than for solid units in assessing masonry strength.

It is usual to take the strength of hollow units which are to be laid full-bedded as the

maximum test load divided by the gross area of the unit. This value is then used to

determine the masonry strength as if the unit were solid.

The stress conditions and mode of failure of shell-bedded hollow block masonry differ

considerably from those in solid block masonry. They have been investigated by Shrive

who has shown that tensile stresses are developed in the webs of the blocks, which

eventually lead to failure.

Hollow block work masonry is frequently built with the cores filled with concrete (grout).

The compressive strength of this type of masonry is found to be considerably less than

the sum of the strengths of the hollow block and concreted core tested separately, even

when the materials are of approximately the same nominal strength.

This is because there is a difference in the strains in block and fill materials at ultimate

load.

Thus Hamid and Drysdale have found the strain at ultimate strength of fill material used

in their investigations to be about 0.0024 compared with the strains at failure of the block

material of 0.0036. BY Arnold W. Handry in Structural Masonry (1998)


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2.4.8: Benefit of using concrete blocks .

It is faster to built with concrete blocks than with bricks and the amount of mortar is

reduced to less than half. If face shell bedding is used, in which the mortar is placedonly along the edges of the blocks, the consumption of mortar is reduced by a further

50%. However, the total cement required for the blocks and mortar is far greater than that

required for the mortar in a brick wall.

2.5: Concrete blocks forming process.

2.5.1: Mix proportion of blocks.

Concrete blocks are often made of 1:3:6 concrete with a maximum aggregate size of

10mm or a cement-sand mixture with a ratio of 1:7, 1:8 or 1:9. These mixture , if

properly cured, give concrete blocks a compressive strength well above what is required

in one-storey building.

The blocks may be solid, cellular or hollow. Cellular blocks have cavities with one endclosed while in hollow the cavities pass through. Lightweight aggregate such as cracked

pumice stone is sometimes used. Blocks are made to a number of coordinating sizes, the

actual sizes being About 10mm less to allow for the thickness of the mortar.

2.5.2: Blocks manufacturing.

Blocks can be made by using a simple block- making machine operated by an engine

or by hand. They can also be made by using simple wooden moulds on a platform or

floor. The mould can be lined with neat steel plate to prevent damage during

tamping and to reduce wear on the mould. In large-scale production steel moulds are

often used.


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The wooden mould is initially oiled overnight and need not be oiled each time it is

filled. It is sufficient to wipe it clean with a cloth. The concrete, of stiff or plastic

consistency placed in layer is compacted with a 3 kg rammer. The mould has a

steel plate cut to the shape of the Block which is put on as a lid and held dawn

as the hollow-making pieces are then loosened and the sides of the mould removed

with a swift motion. All parts of the mould should be slightly tapered so they can be

easily removed from the block.

Starting the day after the block have been made, water is sprinkled on them for two

weeks during curing. After 48 hours the blocks can be removed for stacking. But the

wetting is continued. After curing, the blocks are dried. If damp blocks are put in wall,

they will shrink and cause cracks. To assure maximum drying, the blocks are dried. If

damp blocks are stacked interspaced, exposed to the prevailing wind and in the case of

hollow blocks, with the cavities laid horizontal to form a continuous passage for the

circulating air.

2.5.3: Decorative and Ventilating blocks.

Decorative concrete or sand/cement blocks can serve several purposes:

• Provide light and security without installing windows, or shutters.

• Provide permanent ventilation.

• Give an attractive appearance.

In addition, some are designed to keep out rain while others include mosquito-proofing.

Blocks of simple shape can be made in a wooden mould by inserting pieces of wood to

obtain the desired shape, but more complicated designs usually require a professionally

made steel mould.


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2.6.Mortar for jointing.

Mortar is a plastic mixture of water and binding materials used to join concrete blocks,

bricks or other masonry units. It is desirable for mortar to hold moisture, be plastic

enough to stick to the trowel and the blocks or bricks and finally to develop adequate

strength without cracking.

Mortar need not be stronger than the units it joins. In fact cracks are more likely to appear

in the blocks or bricks if the mortar is excessively strong. There are several types of

mortars each suitable for particular applications and of varying costs. Most of these

mortars include sand and ingredient.

In all cases the sand should be clean, free of organic material, be well graded

(a variety of sizes) and not exceed 3mm of silt in the sedimentation test. In most cases,

particle size should not exceed 3mm as the mortar will be " hash″ and difficult to work

with. Lime mortar is typically mixed 1 part lime to 3 of sand. Two types of lime are

available.

Hydraulic lime hardens quickly and should be used within an hour. It is suitable for both

above and below ground applications. Non-hydraulic lime requires air to harden and can

only be used above ground. If smoothed off while standing, a pile of this type of lime

mortar can be stored for several days.

Cement mortar is stronger and more waterproof than lime mortar, but is difficult to work

with because it is not "fat″ or plastic and falls away from the blocks or bricks during

placement. In addition, cement mortar is more costly than other types.

Consequently it is used in only a few application such as dump-proof course or in

some limited areas where heavy loads are expected. A 1:3 mix using fine sand is

usually required to get adequate plasticity.


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Compo mortar is made with cement, lime and sand. In some localities a 50:50

cement-lime mix is sold as mortar cement. The addition of the lime reduces the cost

and improves the workability. 1:2:9, cement-lime-sand mix is suitable for general

purposes, while a 1:1:6 is better for exposed surfaces and a 1:3:12 can be used for

interior walls or stone walls where the extra plasticity is helpful.

Mortar can also be made using pozzolana, bitumen, cutback, or soil. A 1:2:9 Lime

pozzolana-sand mortar about equals a 1:6 cement-sand mortar. Adobe and stabilized soil

blocks are often laid in a mortar of the same composition as the blocks.

Table 2.2 and 2.3 provide information on the materials required for a cubic Meter of

various mortars and the amount of mortar per square meter for several building units.

Starting with cement mortar, strength decreases with each type, although ability to

accommodate movement increases.

Table 2.2: Materials required per Cubic Meter of mortar.

Type Cement bag Lime kg Sand m3

Cement mortar 1:5 6.0 - 1.1

Compo mortar 1:1:6 5.0 100.0 1.1

Compo mortar 1:2:9 3.3 13.5 1.1Cement mortar 1: 8 3.7 - 1.1

Compo mortar 1:3:12 2.5 150.0 1.1

Lime mortar 1:3 - 200.0 1.1

Table 2.3: Mortar Required for Various Types of Walls.

Type of wall Amount required per m2 wall

11.5 cm brick wall 0.25 m3

22.2cm brick wall 0.51m3

10cm sand-cement block wall 0.008m3




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2.7 : Cost in structural materials.

2.7.1: Economy in construction.

According to B.N. Dutta in estimation and costing in civil engineering, the construction

should be done as economic as possible by organizing labor, materials, supervision etc.

All designs and working drawing should be prepared well in advance. Requirement of

materials should be worked out and materials should be organized, collected and stocked

close to the site of working well in advance so that work is not held up for want of

materials.

Materials should be stored at suitable place so that they can be mixed and supplied to the

mason and other artisans readily with least possible lead and delay.

Laborers should be well organized to use then fully and the number of different category

of labor should be controlled and their work supervised to get maximum work from them.

The whole construction shall be completed as quickly as possible so that the supervision

cost may be minimum possible.

Over head costs should be as low as possible, local materials should be used as far as

possible which will be cheap, and save cost of transport. Locally available stone, timber

etc, should be used which will reduce cost of transport. As cement and steel are costly

and are not readily available, stone slab may be use in roof slab instead of reinforced

concrete.

2.7.2: Unit cost.

For a given production figure, fixed and variable costs are added together and total

divided by the number of blocks produced giving the unit cost. This enables the price of

blocks to be set at a sensitive level. It is useful to calculate the effect of changes in cost or

in productivity on the unit cost. The costs of raw materials and stabilizer remain

identical.


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2.7.3: Cost estimating.

The estimated cost is prepared in order to know the probable cost of construction before

starting the project works. If the money available lower than the estimate, attempts must

be made to reduce the cost, by reducing the work or by changing the specifications.

In preparing the estimate the quantities of different items of work are calculated and from

these quantities the cost is calculated. For that matter a knowledge of drawings is

essential. The one who can understand and read a drawing can find out the dimensions in

length, breadth, height or depth etc. Calculations consist mainly of a length x breadth x

height for volumes and length x breadth or length x height for areas.

In the preparation of estimates one has to go into details of each item however big a

small it might be. Nothing should be left or missed. An estimator should picture the

object (the structure in his mind from the study of drawings and specifications).

Alternatively the estimate can be done by measuring the length, breadth and height

from the existing structure.

If estimate is exceeded it becomes difficult to the engineer to explains and account

for additional money. Inaccuracy in preparing estimate; mission of items, changes

in design improper rates etc.., are the reason for exceeding the estimate, throughincrease in the rates is one of the main reason.

In forming a correct estimate, care should be taken to find out the dimensions of all

items correctly, and to avoid omissions of any kind of work or part there of. The rate

of each item should also be reasonable and workable.

The rate in estimate provide for the complete work, which consist of the cost of

materials, transport, cost of water, taxes, establishment and supervision cost

reasonable profit of contractor, etc. In preparing estimate the principle to be followed

is to make each item or dimension clear and intelligible so that they can be

understood, checked or verified by any body. A remark column may be introduced

and notes may be given where necessary.


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2.7.4: Methods of estimating.

1. Estimate : Previous to stating the construction project it is compulsory to know its

probable cost which is worked out by estimating. An estimation is a computation of the

quantity required and payments expected to be incurred in the construction of a work.

The estimate is the probable cost of a work and is determined theoretically by

mathematical calculations based on the plans and drawings and current rates.

Approximate estimate may be prepared by various methods but accurate estimate is

prepared by detailed estimate method.

2. Actual cost : The actual cost of work is known at the completion of the work.

Account of all expenditure is maintained day to day during the execution of work in the

account section and at the actual cost should not differ much from the estimated cost

worked out at the beginning.

3. Detailed estimate : Preparation of detailed estimate consists of working out the

quantities of different items of work and then working out the cost. The estimate is

prepared in two stages :

a. Details of measurements and calculation of quantities.

The whole work is divided into different items of work as earth work, concrete, etc.. and

the items are classified and grouped under different sub-heads, and details of

measurement of each item of work are taken out and the quantities under each item are

computed in the prescribed form known as measurement form.

b. Abstract of estimated cost.

The cost under item of work is calculated from the quantities already computed at

workable rate, and the total cost is worked out in prescribed form, abstract of estimate

form. A 1.5% to 3% is also added for contingencies, to allow for petty contingent

expenditures, unforeseen expenditures, changes in design, changes in rates, etc. Which

may occur during the execution of work charge establishment.

The grand total thus obtained is estimated cost of work.


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3. Rates. Rates of different items in the estimate are the current rates for the completion

of the items of work which include supply of materials, transport, labor, scaffolding

overheads, contractor's profit, taxes, etc.

By IVOR H. Seeley in building construction technology.


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CHAPTER III . 3.0 : RESEARCH METHODOLOGY.

3.1 : Data collection techniques.

The first and most important information was extracted from library and Web site. All

most literature review concerning bricks and blocks Like sizes, strength, mix ratio,

manufacture, raw materials etc are recorded from engineering published materials.

The second data collection technique applied in this research is the site Visiting. The

most concerned site is "BRIQUETERIE RWANDAISE RULIBA″ (BRR).The objective

that visit was to Collect the data / information about the Bricks produced by that factory

like technical specifications, cost, availability and the center of market. The information

tabulated below was extracted from syllabus of Ruliba factory.

Sizes of bricks/

Blocks (mm)

Mass (kg) Pieces/m2 cost/ piece

(rwf)

cost/m2

(rwf)

400 x 175 x 120 10.5 20 434.24 8684.8

400 x 175 x 95 6.9 25 316.24 7906

250 x 175 x 190 8.9 20 408.28 8165.6

250 x 175 x 95 4.35 36 198.24 7136.64

250 x 120 x 95 3.15 36 135.94 4893.84

260 x 125 x 68 2.6 52 80.24 4172.48

210 x 100 x 63 2 60 76.7 4602

210 x 50 x 63 1 60 47.2 2832

210 x 100 x 63 3 60 231.28 13876.8

Table 3.1 : Variety of Ruliba bricks and their relatives prices.


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The third data collection technique used is experiment like laboratory test. The crushing

strength test was conducted in order to know the resistance of Ruliba bricks under applied

load. Prepared sample is placed between the compressive machine plates and the load is

applied regularly and axially to the sample. The maximum load at failure divided by the

loaded area of the brick determine the crushing strength of the brick.

The observation method are used to know attractive appearance that presented Ruliba

bricks, the uniformity of color; surface and edges. Hand manipulation may necessary to

test the roughness of materials surface.

The visit was also been conducted on field were the construction works by using concrete

blocks took place. The technical specifications like mix proportion, size and the strength

was been recorded. The interview method were applied to know the real situation on the

construction field.

Production and construction cost.

Estimation and costing of two typical walls is a benchmark of this study. Two typical

walls were considered in order to make safe comparison . One is constructed with Ruliba

blocks (210x100x63), the second with concrete blocks (400x200x150).

Calculations consist mainly of a length x breadth x height for volumes

and length x breadth or length x height for areas.


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3.2 : Data organization for analysis.

3.2.1 : Calculation of masonry unit cost.

A) Bricks from Ruliba.

For calculation of masonry unit cost for Ruliba bricks, four items are considered: The

unit cost of bricks, transport, mortar for binding units and labor cost.

1. Cost of bricks.

The cost of Ruliba bricks are fixed according to their mass, sizes and properties. To be

familiar on their unit cost, the price of one brick must be multiplied by the number of

bricks required to make one cubic meter of masonry.

Sizes (mm) Pieces/m3 cost/ piece

(rwf)

Cost/m3

(rwf)

400 x 175 x 120 114 434.24 49503.36

400 x 175 x 95 143 316.24 45222.32

250 x 175 x 190 114 408.28 46543.92

250 x 175 x 95 206 198.24 40837.44

250 x 120 x 95 300 135.94 40782

260 x 125 x 68 433 80.24 34743.9

210 x 100 x 63 600 76.7 46020

210 x 50 x 63 1200 47.2 56640

210 x 100 x 63 600 231.28 46256

Table 3.2: Unit cost of Ruliba bricks.


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2. Transport cost.

The transport cost depends upon the distance of and the weight of materials. At

reasonable distance, say from Ruliba to any where in Kigali city, one tour of five tones

costs 35,000rwf of transport. In table below, the unit cost presented, is estimated

basically to that information by calculation the transport cost of one kg per km multiply

by the number of bricks contained in one cubic meter of masonry.

In other Provinces, it is very strange to use Ruliba blocks because of high carrying price.

For instance, In districts like Musanze (North); Nyanza (south); Kayonza (Eastern) and

Karongi(Western), the transport costs lie between 60,000rwf and 80,000rwf per trip. The

table bellow illustrates the estimated transportation cost for different sizes.

Sizes (mm) Mass (kg) Bricks

per trip

Bricks per

one m3

cost/kg/km

(Rwf)

Cost/m3/km

(Rwf)

Unit cost at

20 km

400 x 175 x 120 10.5 476 114 3.7 421.8 8436

400 x 175 x 95 6.9 725 143 2.4 343.2 6864

250 x 175 x 190 8.9 562 114 3.1 353.4 7068

250 x 175 x 95 4.35 1149 206 1.5 309 6180

250 x 120 x 95 3.15 1587 300 1.1 330 6600

260 x 125 x 68 2.6 2500 433 0.7 303.1 6062

210 x 100 x 63 2 2500 600 0.7 420 8400

210 x 50 x 63 1 5000 1200 0.35 420 8400

210 x 100 x 63 3 1667 600 1.0 600 12000

Table 3.2: Unit cost of transport at 20km distance of various size of Ruliba bricks.


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3. cost of mortar.

Ratio: 1:4

One part of cement over four parts of sand:

Volume of brick with joint = 0.220 x 0.110 x 0.073 = 0.0017666m3

Number of bricks = 1/0.001766 = 566 bricks

Volume of net brick = 0.210 x 0.100 x 0.063 = 0.001323m3

Total volume of bricks : 566 x 0.001323 = 0.749m3

Volume of mortar : 1- 0.749 = 0.251m3

Unit volume of cement : 1/5 x 0.251 = 0.0502 m3

Mass of cement : = 0.0502 x 1500 = 75.3 kg

Unit cost of cement = 12000/50 x 75.3 = 18072 rwf

Unit volume of sand : 4/5 x 0.251 = 0.2008m3

Unit cost of sand : 35000/5 x 0.2008 = 1405.6 rwf

Unit cost of mortar = Unit cost of cement + Unit cost of sand

= 18072 +1405.6

=19477.6rwf

4. Labor cost.

Sizes (mm) Built

bricks

per day.

Number of

bricks in m3.

Labor Cost of

one brick (rwf)

Labor cost of

one m3(rwf)

400 x 175 x 120 19 114 353.68 40239

400 x 175 x 95 24 143 280 40040

250 x 175 x 190 19 114 353.68 40239

250 x 175 x 95 38 206 176.84 36429

250 x 120 x 95 56 300 120 36000260 x 125 x 68 84 433 80 34640

210 x 100 x 63 120 600 56 33600

210 x 50 x 63 240 1200 28 33600

210 x 100 x 63 120 600 56 33600

Table 3.4 : Unit labor cost of masonry for various sizes of bricks.


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One mason is paid 560rwf / hour

One porter is paid 280rwf/ hour

Total = 840rwf/ hour i.e. 840 x 8 =6720rwf.

One porter and one mason can built 120 bricks of 210 x 100 x 63 mm sizes per day.

B) Concrete blocks.

Three main items must be taken into account in estimation of unit cost of wall made with

concrete blocks. Then, the unit cost of wall =(Cost of blocks + labor cost +cost of

mortar). It is more economic to make blocks on place of work to avoid the transport cost

of finished units.

The cost of blocks combines both the cost of raw materials and which of former. So that,

his is paid around 40rwf per block. For that case, the transport fees of raw materials may

be considered. On market, one trip of sand bought between 35,000rwf and 40,000rwf,

while one bag of cement costs 11,0000rwf for imported Hima Portland cement and

13,000rwf for local Portland cement.

For labor cost, one mason and one porter can build about 60 blocks of 400 x 200 x 170

mm sizes per day. The day of work is equivalent of eight hours. Most employers does not

consider the security and other taxes for their employees which is wrong. Then, the labor

cost of one mason is 560rwf per hour, while the porter paid 280rwf per hour.

The cost of mortar for binding concrete blocks units is estimated like the cost of blocks.

The difference lies in their mix proportion ratio in which, that of mortar is one part of

cement to four parts of aggregate.


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1.Unit cost of blocks.

Net volume of blocks in one cubic meter of wall.

Net volume of one block: 0.40 x 0.20 x 0.17 = 0.0136 m3.

Volume of block with 10 cm joint : 0.41 x 0.21 x 0.18 = 0.0155m3.

Number of blocks : 1/0.0155 = 64.5 blocks.

Net volume of blocks in 1m3:0.0136 x 64.5 = 0.877m3.

2.Unit cost of raw materials.

Mix proportion : 1: 14.

Unit volume of cement : 1/15 x 0.877 = 0.058 m3.

Mass of cement: 0.058 x 1500 = 87 kg.

Cost of cement: 12000/50 x 87 = 20880rwf.

Unit volume of sand: 14/15 x 0.877 = 0.818m3.

5m3 costs 35000rwf i.e. 7000rwf/m3.

Unit cost of sand: 0.818 x 7000 = 5726rwf.

Former unit cost: 40 x 64.5 = 2580rwf.

unit cost of blocks = 20,880 + 5,726 +2,580 =29,186rwf.

3.Unit cost of mortar for binding materials.

Ratio: 1:4

Unit volume of mortar : 1- 0.877 = 0.123 m3

Unit volume of cement :1/5 x 0.123 = 0.024m3

Mass of cement: 0.024 x 1500 = 36 kgUnit cost of cement: 12000/50 x 36 = 8,640rwf

Unit volume of sand: 4/5 x 0.123 = 0.098 m3

Unit cost of sand: 35000/5 x 0.098 = 686rwf

Total unit cost of mortar: 8,640 + 686 =9,326rwf.


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4.Labor unit cost.

One mason is paid to 560rwf / hour and one porter is paid 280rwf/ hour.Labor cost = 840rwf/ hour i.e. 840 x 8 = 6,720rwf

As said above, one unit of volume contains 64.5 blocks sized to

400mm x 200mm x170mm.Then, the output of one mason is 60/64.5=

0.930m3 per day.

From this, the determination of unit labor cost is simple. That must be

equal to 6,720/ 0.930 x 1=7,226rwf.

The unit cost of blocks wall = 29,186 + 9,326 + 7,226 = 45,738rwf.

Table 3.5 : Unit cost comparison of Ruliba bricks wall and concrete wall.

Ruliba bricks (1m3) Concrete blocks (1m

3)

Descriptions Unit cost(rwf.) Descriptions Unit cost (rwf.)

1. Bricks unit cost 45,172 Blocks unit cost 29,186

2. Trans. Unit cost 7,779 Trans. Unit cost -3.Mortar unit cost 19,477.6 Mortar unit cost 9,326

4. Labor unit cost 36,487 Labor unit cost 7,226

Total unit cost 108,915.6 Total unit cost 45,738


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3.2.2: Data related to technical specifications.

A)Technical specification of Ruliba bricks.

Report of laboratory test for strength and density.

Purpose: This laboratory test is conducted in order to state some mechanical properties

of Ruliba bricks like compressive strength and the density . This test will help us to make

comparison of Ruliba bricks properties with that of concrete blocks.

Hypothesis.Each structural wall must withstand against natural and artificial action like compressive

stress, capillarity, etc. That will depend on resistance of its structural materials say bricks.

The problem behind is to know the ability of these materials to support the applied loads

in order to make safe design. As the Ruliba brick is the case study, it required to know the

crushing strength of that product.

Materials and apparatus.

- Two Ruliba bricks samples;

- Balance;

- Ruler;

- Crushing- machine.

Procedure.

• Preparation of samples;

• Measurement of loaded area;

• The brick is then weighted ;

• The specimen is then compressed between the plates of testing machine.

• The maximum load at failure is noted as the crushing load of the brick.


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Results and data.

Sample 1: Length (L1) = 26 cm

Width (W1)= 12.5 cm

Height (H1)= 6.8 cm

Number of Hollow (N)= 6

Length of hollow (l1) = 7.8 cm

Width (w1) = 2.7 cm

Height (h1) = 6.8 cm

Crushing load = 240 KN

Loaded area = (L1 x W1) – (l1 x w1) x N

= (26 x 12.5) – (7.8 x 2.7) x 6 = 199 cm2

Crushing strength = Crushing load / loaded area of brick.

= 240/199

= 1.21 KN/cm2

Sample 2 : Length (L2) = 26 cm

Width (W2)= 12.5 cm

Height (H2)= 6.8 cm

Number of Hollow (N)= 6

Length of hollow (l2) = 7.8 cm

Width (w2) = 2.7 cm

Height (h2) = 6.8 cm

Crushing load = 440 KN

Loaded area = (L2 x W2) – (l2 x w2) x N

= (26 x 12.5) – (7.8 x 2.7) x 6 = 199 cm2

Crushing strength = Crushing load / loaded area of brick.

= 440/199

= 2.21 KN/cm2


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Density:

Sample 1: Total volume of brick = 26 x 12.5 x 6.8 = 2210 cm3

Total volume of voids = 7.8 x 2.7 x 6.8 = 143.208 cm3

Total volume of solid = 2210 – 143.208 = 2066.792 cm3

Density = Weight (W1)/ Total volume of solid

= 2.633/2066.792 x 10-6

= 1273.95 Kg/m3

Sample 2: Total volume of brick = 26 x 12.5 x 6.8 = 2210 cm3

Total volume of voids = 7.8 x 2.7 x 6.8 = 143.208 cm3

Total volume of solid = 2210 – 143.208 = 2066.792 cm3

Density = Weight (W2)/ total volume of solid

= 2.643/2066.792 x 10-6

= 1278.79 Kg/m3

Average Density = (D1 + D2)/2

= (1273.95 + 1278.79)/2

= 1276.37 Kg/cm3

Conclusion and recommendation.

The result of test show that there is a great difference between the crushing strength of

sample number 1 and that of sample number 2 . The previous observations made on

samples was shown that there was small crack on sample 1, which is the reason of that

difference in strength. So that, result given by the corresponding sample must be ignored

and consider the second result as the crushing strength of Ruliba bricks.i.e.2.21 KN/cm2.

As density, the average of two solutions gives the density of 1276.37 kg/cm3.

As recommendation, it better to control carefully the samples before testing and to take

more samples during laboratory test.


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Table 3.6: Technical specifications of Ruliba bricks.

Types Sizes (cm) Mass(kg) Mass density

(kg/m3)

Average compressive

strength (kg/cm2)

Hollow block 40 x 17.5 x 12 10.5 1250 2.16

Hollow block 40 x 17.5 x 9.5 6.9 1037.6 1.79

Hollow block 25 x 17.5 x 19 8.9 1070.6 1.85

Hollow block 25 x 17.5 x 9.5 4.35 1046.6 1.81

Hollow block 25 x 12 x 9.5 3.15 1666.7 2.88

Hollow block 26 x 12.5 x 6.8 2.6 1276.37 2.21

Hollow brick 21 x 10 x 6.3 2 1511.7 2.62

Hollow brick 21 x 5 x 6.3 1 1511.7 2.62

Fire brick 21 x 10 x 6.3 3 2267.6 3.92

B)Technical specification of concrete blocks.

Table3.7: Technical specifications of concrete blocks.

Parameters Description

Typical size 300 x 200 x 150

Average compressive strength at 28

days.

50-110 kg/cm2

Mix proportion 1:12-14 (1 part of cement: 12:14 part

sum graded aggregate)

Water absorption in 24 hours Less than 10% by weight


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3.3 : Results presentation.

3.3.1: Strength and density.

The result from laboratory test show that the crushing strength and the density of Ruliba

bricks are respectively equivalent to 2.21kg/m2, and 1276.37 kg/m

3.While

the compressive strength of concrete blocks varies from 50 to 110 kg/m2. Those

parameters recorded after 28 day of manufacture, depends on method of manufacture, the

quality and mix proportion of raw materials. Then, the compressive strength of blocks

made by block-making machine is greater than that of man- made blocks.

3.3.2: Cost.

All most costs of bricks from Ruliba are not affordable by every one in this country. But

are reasonable depending on raw materials used, modern technology used and the esthetic

aspect presented by those products.

All costs of Ruliba bricks fixed according to their Functions, sizes and mass are tabulated

below:

Table 3.8: Total unit cost of masonry for various sizes of bricks.

S i z e s ( m m )

4 0 0 x 1 7 5 x 1 2 0

4 0 0 x 1 7 5 x 9 5

2 5 0 x 1 7 5 x 1 9 0

2 5 0 x 1 7 5 x 9 5

2 5 0 x 1 2 0 x 9 5

2 6 0 x 1 2 5 x 6 8

2 1 0 x 1 0 0 x 6 3

2 1 0 x 5 0 x 6 3

2 1 0 x 1 0 0 x 6 3

Bricks unit cost 49,503 45,222 46,544 40,837 40,782 34,744 46,020 56,640 46,256

Trans. Unit cost 8,436 6,864 7,068 6,180 6,600 6,062 8,400 8,400 12,000

Mortar unit cost 19,478 19,478 19,478 19,478 19,478 19,478 19,478 19,478 19,478

Labor unit cost 40,239 40,040 40,239 36,429 36,000 34,640 33,600 33,600 33,600

Total unit cost 117,656 111,604 113,329 102,924 102,860 94,924 107,498 118,118 111,334


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The cost of concrete block is influenced by which of its constituents and the production

cost. For a ratio of 1:14, one bag of cement is used to produce 36 blocks with sizes 400 x

200 x 200mm.Also, for sand, one trip of five tones costs 35,000rwf. The production cost

is 40rwf per block. (man-made block.). For that, total cost of concrete block is about

500rwf.

3.3.3: Availability.

Ruliba bricks are available at Ruliba factory(B.R.R) situates at Nyabarongo bridge in

Nyarugenge District in Kigali city Province. They are obtained in abundance in different

form , function and sizes.

Concrete blocks are easily available, because they can be produced on work site. The

advantage of producing blocks on site is to avoid the transport cost, to control the quality

of raw materials, to organize the proportion mix process and to save money.

Some peoples produce blocks and sell them at 500-700rwf per block but, the mix

proportion of raw materials is critical because they want to gain more profit.

3.3.4: Materials used.

The clay and shale are the basic raw materials used in Ruliba bricks making. The use of

fuel has replaced that of wood in order to reduce the deforestation velocity.

Raw materials for producing concrete blocks are cement, sand and aggregate with ratio of

1:3:6. The maximum aggregate size is 10 mm. The quality of raw materials must be well

controlled in order to get final product of good properties.


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3.3.5: Method of manufacture.

Bricks from Ruliba factory are made mechanically by using machine. Prepared plastic

clay are extracted as continuous column of rectangular section with or without

perforations which is cut into individual bricks by wire.

Continuously, those bricks are fired up to 900 - 11000 C .Below that temperature, all

components react and dissolves ones with others , forming monolithic material.

Blocks may be made by using machine or hand after mixing raw materials at required

ratio. The obtained product is cured during two weeks by sprinkling water up to it

maximum strength. Produced blocks can be solid ,cellular or hollow depending on mould

used.

3.3.6: sizes.

Ruliba bricks are available in various sizes. Each client buy the products according to his

appreciation . The bricks of greatest sizes are similar to those of blocks are commonly

used in construction of contour walls. Small bricks are used in construction of building

walls.

Products Function Sizes (cm)

Hollow block Face wall 40 x 17.5 x 12

Hollow block Face wall 40 x 17.5 x 9.5

Hollow block Face wall 25 x 17.5 x 19


Hollow block Face wall 25 x 12 x 9.5


Hollow brick Face wall 21 x 10 x 6.3

Hollow brick Face wall 21 x 5 x 6.3

Fire brick Fire resistant 21 x 10 x 6.3

Table 3.9: Different sizes of Ruliba bricks.


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Sizes are that the main difference between blocks and bricks. The fist one have great

sizes while the second one have small sizes. so that, common sizes of blocks are 400 x

200 x 200mm; 400 x 200 x 175mm; 400 x 200 x 150mm; 300 x 200 x 150mm etc.

3.3.7 : Center of market.

The center of market is Kigali city, because of reasonable distance from Ruliba. It is not

easy to get market in others provinces or district for reason of high transport cost. In

addition, most richest people and companies live in Kigali town.

Concrete blocks are popular because of its cheapness and resistance. In addition, it

manufacturing process not requires high technology and more instruments. Even if the

binder like cement is cheap, their cost is affordable comparatively to other structural

materials.


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CHAPTER IV . 4.0 : DISCUSSIONS.

4.1: Cost comparison.

Let us to consider two structural wall of 10m length, 3m height, and 0.20 m thick

constructed respectively with Ruliba bricks and concrete blocks.

The abstracts of estimation and costing of those walls are presented bellow.

4.1:Abstract of estimation and costing of typical wall made in Ruliba bricks.

SN Items of work Units Quantities Rate Total cost (rwf)

1 Bricks work

with cement

mortar

m3 6 108,916 653,496

2 Jointing outside

and inside

m2 60 4000 240,000

3 Varnishing m2 60 2,500 150,000

Total 1,043,496

Table 4.2:Abstract of estimating and costing of typical wall made in concrete blocks.

SN Items of work Units Quantities Rates(rwf) Total cost(rwf)

1 Blocks work with

cement mortar

m3 6 45,738 274,428

2 Plastering with

cement mortar

m2 60 4,000 240,000

3 Painting m2 60 2,500 150,000

Total 664,428


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As seen in above tables, only three items are considered in each case. It is observed that

the total cost of wall made with concrete blocks is lower than that which is constructed in

Ruliba bricks.

4.2:Compressive strength comparison.

Brick/Block Sizes in mm. Compressive

Strength(kg/cm2)

Density(kg/m3)

Concrete block 300x200x150 50-110 2250

Bricks from

Ruliba

260x125x68 22.1 1276.37

Table 4.3:Size, compressive strength, density of concrete blocks and bricks from Ruliba

factory.

General comparison of concrete blocks with Bricks from Ruliba.

Concrete blocks Bricks from Ruliba

High Compressive strength

Less cost

Can be produced on site

Has not good appearance

Are most available

Are require plastering

Are not require jointing

The manufacturing process is not

complicated

Less variability of sizes

Machine and hand made products

Are not burned

Their density is high

Low compressive strength

High cost

Are produced on factory

Has good appearance

Are only available on factory

Not requires the plastering

It requires jointing

The manufacturing process is

complicated.

Most variable of sizes.

Machine-made products

Are burned

Their density is low


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CHAPTER V. 5.0 : CONCLUSION AND RECOMMENDATIONS.

5.1 : Conclusion.

According to results obtained and the discussion made, it is shown that the Concrete

blocks should be preferable before bricks from Ruliba because of it durability and it low

cost. But, in point of view architectural aspect, the bricks from Ruliba are dominant

because of it good looking when is used in construction of wall. That is due to their

regular corners and joint when Portland cement mortar is used in jointing.

The unit cost of wall made with Bricks is greatest due to its transport cost, method of

manufacture and it availability. The time required to built the structural wall with each of

both materials is different. In addition, it is not easy to use Ruliba bricks for people who

lives away of Kigali city and its surrounding in reason of transport price.

For that case, most people prefer to use concrete blocks in their construction project.

Also, the concrete blocks are most used in internal and external wall where the plaster is

required. As environmental sector, the problem are similar for both materials when the

engines used produce gas waste which is very dangerous to the atmosphere.

As conclusion, the results of this project show that concrete blocks are compressive

resistant, less expensive but less esthetic comparatively to Ruliba bricks. So that, it is

advantageous to use concrete blocks fist of Ruliba bricks.

5.2 : Recommendations.

After the completion of this project, the recommendations given are follow:

The concrete blocks should be adopted in construction of buildings fist to Ruliba

bricks because of they durability as well as they cheapness.

The price of Ruliba bricks should be minimized as possible in order to facilitate

the population to construct the esthetic building with low cost .

The mix proportion of Ruliba bricks should be controlled in order to improve they

qualities.


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REFERENCES.

A. Books.

1.Arnold W. Handry (2003)“ Structural Masonry” Addison Wesley longmen

limited , England.

2. E. Paul Degarmo, JT.Black and Ronarld A. KOHSER (1997) “Materials and

processes in manufacturing”, New delhi.

3. Ivor H. Seely, (1992) “Building technology”, customer services department,

mac millan Distribution Ltd. England.

4. Prof. BN Dutta, “Estimating and costing in civil Engineering” UBS

Distributors Pvt Ltd.

5. Tata Mc (2003) “Civil Engineering materials”, Graw- hill publishing company

Limited, New-delhi.

B. Web sites:

http://www. Google.com

http:// www.scoland.gov.uk


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APPENDICES.

The information below, was given by one of mason of B. L HARBET RWANDA

Limited. The Structural materials used are Reinforced concrete, modern bricks and

blocks.

Statement of calculation of monthly salary for mason.

Enterprise : B.L HARBERT RWANDA Limited

Works : Construction of New American Embassy

Site: KACYIRU

Rate to pay 560rwf/hour

Pay type FRW Rate Hours worked Total

RT Basic 560 152.00 85,120

Over time 1.5 840 83 69,720

Over time 1.7 952 47 44,744

Double Time 1,120 22 24,640

Gross to pay 224,224Frw

PAYE Per Tax table 51267.2

NSSF 3% of Gross Pay 6726.72

FARG 1% of basic 851.20

Net to pay 165,378.88Frw


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i

DECLARATION.

I, ZIRIMWABAGABO Léodomir, declare that the project entitled “ COMPARISON

BETWEEN CONCRETE BROCKS AND BRICKS FROM RULIBA” is my own work.

It has never been presented any where in Institute or University for the same purpose.

ZIRIMWABAGABO Léodomir………………………………


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Dedication.

To:

My God;

My family;

All who have contributed to this work.


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iii

ACKNOWLEDGEMENT.

The author is grateful to all who contributed to the successfulness of the

present study, in particular way thanks goes to Mr. KAYINAMURA Francis

who provided guidance to the present research work.

Special thanks go to KIST Staff and students for their immeasurable

technical assistance and their availability to assist in application of class

theories and practices.

I m grateful to the staff of Ruliba factory who provided me with useful data

that made this study possible. The bless of God for all who gave a helping

hand to the successful completion of the present work.


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iv

ABSTRACT.

The current technology involves the construction of building with update

materials require low cost and stability. Given that, some one who

desires to construct a building, the common question to be asked for is how

to get cheap and esthetic building materials.

Raw materials for manufacturing concrete blocks are expensive. For

instance, on one bag of local Portland cement costs 13.000rwf .On the other

hand, cutting trees for firing clay bricks leads to deforestation which affectsour environment.

The bed rock of this project is to take out the confusion during the choice of

sustainable building materials, the best objective in building design, as well

as to show how it is possible to build up the buildings using materials which

may resist against natural actions.

Main assumption of this project, are the selection of structure materials,

require low cost and durability; the ability to withstand against the

expensiveness of raw material and the design for environment.

In order to make excellent comparison, different techniques were employed.

Information about topic from libraries, website field visit of Ruliba factory

BRR was tracked down. The crushing strength test was conducted in order

to check the resistance of Ruliba bricks. In addition, the cost of two typical

walls constructed in materials under comparison was estimated.


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v

TABLE OF CONTENTS.

Certificate

Declaration………………………………………………………………………………..i

Dedication………………………………………………………………………………...ii

Acknowledgement……………………………………………………………………….iii

Abstract…..…………………………………………………..…………………………..iv

Table of contents……………………………………........................................................v

List of tables……………………………………………………………………………..vi

List of symbols and abbreviations …………………………………………………….vii

Appendices

CHAPTER I .

1.0 : Introduction ……... ……... ……... ……... ……... ……... ……………………..1

1.1 : Statement of problem……………………………………………………...…………1

1.2 : Objectives of study… ……... ……….…….............................................................1

1.3 : Justification………………………………………………………………………......2

1.4 : Scope of study………………………………………………………………………..3

CHAPTER II .

2.0 : Literature review…………………………………………......................................4

2.1: Varieties of bricks and blocks ……………………………………………………..4

2.1.1 : Clay bricks……………………………………………………...………….4

2.1.2 : Calcium silicate bricks ………………………………...…………………..6

2.2 :Bricks forming process………………………………………………...…………….6

2.2.1 : Manufacture process……………………………………………………….6

2.2.2 : Firing……………………………………………………………………….62.3 : Technical specification of bricks…………………………………………...………..7

2.3.1 : Strength of bricks …………………………………………………..……...7

2.3.2 : Test for compressive strength ……………………………………..……...8

2.3.3 : Compressive strength and other mechanical properties……………….…..8

2.3.4 : Factors affecting compressive strength……………...................................9


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2.3.5 : Size of bricks ………………………………………..................................9

2.4 : Concrete blocks features……………………………………………………..........10

2.4.1 : Concrete block technology…………………………………………...…..10

2.4.2 : Business ……………………………………………………………….....10

2.4.3 : Product ………………………………………...........................................10

2.4.4 : Unique features of concrete block technology……...................................11

2.4.5 : Production process ……………………………………………………….11

2.4.6 : Building with concrete ………………………………………………...…12

2.4.7 : Perforated and hollow blocks…………………………………………….12

2.4.8 : Benefit of using concrete blocks………………………………………….14

2.5 : concrete blocks forming process……………………………………………………14

2.5.1 : Mix proportion of blocks ………………………………………………...14

2.5.2 : Blocks manufacturing ……………………………………………………14

2.5.3 : Decorative and ventilating blocks….. ……... ……... ……………………15

2.6 : Mortar for jointing…………………………….........................................................16

2.7: Cost in structural materials………………………………………………………….18

2.7.1 : Economy in construction ………………………………………………...18

2.7.2 : Unit cost ………………………………………………………………….18

2.7.3 : Cost estimating …………………………………………………………19

2.7.4 : Method of estimating …………………………………………………….20

CHAPTER III .

3.0 : Research Methodology ……………………………………………………..........22

3.1 : Data collection techniques………………………………………………………….22

3.2 : Data organization for analysis……………………………………………………...24

3.2.1 : Calculation of masonry unit cost…………………………………………24

3.2.2 : Data related to technical specifications……………..................................30


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3.3 : Results presentation………………………………………………………………...34

3.3.1 : strength and density………………………………………………………34

3.3.2 : Cost……………………………………………………………………….34

3.3.3 : Availability…………………………...……………..................................35

3.3.4 : Materials used…………………………………………………………….35

3.3.5 : Method of manufacture………………...…………………………………36

3.3.6 : Sizes…………………………………...……….........................................36

3.3.7 : Center of market……………………………..…………………………...37

CHAPTER IV .

4.0 : Discussions ………………………….………….…………………………………38

4.1 : Cost comparison……………………………………………………………………38

4.2 : Compressive strength comparison…………..…………….......................................39

CHAPTER V.

5.0 : Conclusion and recommendations……………..….………………………..........40

5.1 : Conclusion .……………………….……………….................................................40

5.2 : Recommendations…………………………………………………………..............40

References……………………………………………………………………………….41

Appendices


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LIST OF TABLES.

Table 2.1:Average compressive strength of common burnt clay bricks…………………..7Table 2.2: Materials required per Cubic Meter of mortar………………………………..17

Table 2.3: Mortar Required for Various Types of Walls………………………………...17

Table 3.1 : Varieties of BRR Bricks/ blocks and their relative prices………………...…22

Table 3.2 : Unit cost of Ruliba bricks……………………………………………………24

Table 3.3 : Unit cost of transport at 20km distance of various size of

Ruliba bricks………………………………………………………………...25

Table 3.4 : Unit labor cost of masonry for various sizes of bricks………………………26

Table 3.5 : Unit cost comparison of Ruliba bricks wall and concrete wall……………...29

Table 3.6: Technical specifications of Ruliba bricks…………………………………….33

Table 3.7 : Technical specifications of concrete blocks…………………………………33

Table 3.8 : Total unit cost of masonry for various sizes of bricks……………………….34

Table 3.9 : Different sizes of Ruliba bricks ……………………………………………..36

Table 4.1 : Abstract of estimation and costing of typical wall made in

Ruliba bricks………………………………………………………………...38

Table 4.2 : Abstract of estimating and costing of typical wall made in

concrete blocks………………………………………………………………38

Table 4.3 : Size, compressive strength, density of concrete blocks and ………….........39

bricks from Ruliba factory.


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List of symbols and abbreviations.

Abbreviations Descriptions units

KIST Kigali Institute of Sciences and Technology

B.R.R Briqueterie Rwandaise Ruliba

CEET Civil Engineering and Environmental Technology

L1 Length of brick for sample number 1 cm

L2 Length of brick for sample number 2 cm

W1 Width of brick for sample number 1 cm

W2 Width of brick for sample number 2 cm

H1 Height of brick for sample number 1 cm

H2 Height of brick for sample number 2 cm

N Number of hollows -

l1 Length of hollows for sample number 1 cm

l2 Length of hollows for sample number 2 cm

w1 Width of hollows for sample number 1 cm

w2 Width of hollows for sample number 2 cm

h1 Height of hollows for sample number 1 Cm

h2 Height of hollows for sample number 2 Cm

D1 Density of brick for sample number 1 Kg/cm3

D2 Density of brick for sample number 2 Kg/cm3

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M 2008 CEET 28 ZIRIMWABAGABO Leodomir GS20020131.pdf