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Choose the right

Cement

CEMENT

A guide to selecting the right cement for your building requirements

Choose the Right Cement

01 Introduction

09 Kumanga

15 Ordinary PortlandCement

21 Building Tips

22 The Basics

25 Ordering & EstimatingMaterials

27 Plaster

29 Mortar

31 Common Defects & Foundation Tips

33 Wall Tips

34 Finishing Tip

35 Storing & Handling of Cement

02030405

What makes a Good Cement?

Misconceptions about Cement

Lafarge in Malawi

The Lafarge Group

CONTENTS

Intr

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2010 | YOUR GUIDE TO CEMENT | PAGE 1

he Lafarge brand represents values that set trends in the industry today and are an active commitment to sustainable development: so vital for the well-being of future generations. Our values mean:• respect and nurturing for our diverse employees by providing: - equitable employment opportunities - development opportunities to encourage everyone to reach

their full potential • proactively translating our concern for the environment into action plans for:

- rehabilitating our quarries - reducing ʻgreenhouse gasʼ emissions through better

technology and innovative fly ash extended products - reducing the dependence of the cement industry on non-

renewable resources • social responsibility: - assisting the development of neighbouring disadvantaged

communities, by setting up learnership programmes, to create a core of marketable skills

- actively promoting closer long term relationships by assisting in problem solving and demonstrating real concern for the well-being of nearby communities.

What’s in a Name?In 76 countries around the world, the Lafarge brand name stands for leadership in building materials: leadership that has been achieved by applying the knowledge within the Group to bring innovative products and solutions to satisfy the needs of our customers.

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| YOUR GUIDE TO CEMENT | 2010

CEMENT

What makes aGood Cement?

A word of advice from an experienced builder:

“Save on the cost of your building materials by good control, never by lowering quality – it is a false economy!”

We involve ourselves in the work of architects and developers and pioneer cements that extend the boundaries of design. We talk to new construction entrepreneurs and DIY homeowners and innovate more user-friendly, efficient products and support services. We work at building long-term business relationships. We listen to the marketʼs needs and innovate new products and services that differentiate us from our competitors.

Our cements are designed to give you more:

• Industrial control standards that ensure consistent high quality.• Product performance and handling properties that exceed your expectations.

Lafarge products are backed by service:

• Access to technical advice from our Sales Team.• Innovative general support service through our Customer Care Centre.

At Lafarge, cement is not a commodity but the exciting bond that enables the creation of luxury office blocks reaching a mile into the sky, huge sports stadiums, graceful bridges, massive dams, elegant sculptures or just a simple dwelling that you can call home!


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Misconceptionsabout CementMyth: “It says 50kg on the bag, so it must contain 50kg of

cement!”Fact: It should contain 50kg but it is a case of ʻBuyer Bewareʼ!

Not all companies have accurate enough equipment or the management systems to achieve this.

Buy a well-known brand name product. The Lafarge name is your guarantee: our cement is certified by MBS which isclearly marked on all our packaging, assuring buyers of themass of cement they have paid for.

Myth: “Cement extenders reduce the quality of a cement.”Fact: On the contrary, research and development over the

last thirty years has shown that, formulated correctly, quality extenders significantly improve many performance characteristics of hardened concrete, while making concrete and mortar mixes more user-friendly for the builder.

Myth: “Any cement will do for general construction work: just go for the cheapest!”

Fact: Why risk having a poor concrete job? Ask your builderʼs merchant for advice. A good quality branded cement can make concrete and mortar mixes that are easier to mix and place. The finished concrete is also stronger and more durable.

Myth: “A good mortar depends only on how well you mix the materials.”

Fact: Thorough mixing of the materials until a uniform colour is achieved is always essential to avoid a patchy finished appearance and areas of weak strength. However, a good quality cement, makes mixing easier. The resulting more workable, “buttery” mix leads to a higher work rate.

Myth: “The strongest concrete is made with pure cement, not the cements blended with extenders.”

Fact: Properly cured concrete containing quality extenders will achieve a more durable and higher ultimate strength concrete.


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The Lafarge NameThe business of Lafarge meets the basic human need for building materials.

What a Lafarge Bag of Cement Means for You:

- An assurance of quality and performance- A product designed to meet your needs: needs that have been

identified from our work with architects, engineers and everyone in the construction process

- A formulation that has benefited from the international Groupʼs technical know-how to create an innovative, user-friendly product

Lafarge in Malawi trades as Lafarge Cement Malawi Ltd, ISO 9001: 2000 Certified Company and produces two reputable brands of cement namely: Ordinary Portland Cement (OPC) and Kumanga Masonry Cement.

Lafarge Cement Malawi Ltd is continually growing from strength to strength because of the experience and technical resources of the international group. The company has well qualified people in research and development in construction materials to ensure that your needs are met by producing world-class quality Lafargeʼs cement.

Locally, our Quality Assurance Department is supported by the unique technical and laboratory resources of Malawi Bureau of Standards (MBS) in conjunction with European Prestandard

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The Lafarge GroupLafarge is the world leader in building materials, with top-rankingpositions in all of its businesses: Cement, Aggregates & Concrete andGypsum. The Groupʼs 90 000 employees in 76 countries, generatedsales in 2007 of Euros 17,6 billion (over R210 billion).

The Group is:• Customer focused• Concerned for peopleʼs well-being• Concerned for the future

Concern for the environment

Lafarge combines its skills and technical resourceswith the expertise of others for greater effectiveness inthe environmental control field:

• Lafarge was the first industrial group to enter into a worldwide partnership with the environmental protection organization, WWF (World Wide Fund for Nature).

• Lafarge is a founding member of CSI (Cement Sustainability Initiative) which actively promotes responsible management and the worldwide reduction of carbon dioxide emissions by the industry.

• Lafarge is co-chair of the “Energy Efficiency in Buildings” Project, which works towards the objective of zero net energy use in buildings.

Lafarge is theonly company inthe constructionmaterials sectorto be listed in the2008 ‘100 GlobalMost SustainableCorporations in theWorld’

Leading the way with technologyThe Group technical resources include:

construction

Ku

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CEMENT

KUMANGA MC 22.5 XIntroduction Kumanga: MC 22.5X is a masonry cement that achieves superior workability, without air entraining agents, manufactured from Portland Cement Clinker, Gypsum and other additives according to MBS 413:2002 (equivalent to EN413-1).

The superior workability and normal 28 days’ strength development, in particular, make KUMANGA the ultimate solution to the quality demands of all bricklaying, plasterwork, floor screed, pointing, brick & block making in large construction projects as well as Individual Home Builders (IHB).

Product Attributes• NomenclatureX = Contains no air entraining agents 22.5 = Cement StrengthMC = Masonry Cement

• WorkabilityThis hydraulic binder produces very workable ‘buttery’ mortar and concrete mixes that require less effort and are easier to place

• StabilityKUMANGA mortar mixes have a better response to vibration, filling formwork more completely without aggregates falling to the bottom of the pour before setting specifically in brick/block making.

• BleedingKUMANGA has improved water retention and less bleeding for reduced cracking and better finishes.


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Productapplications.• Masonry work: mortars, plasters and screeds • Brick and Block making eg. Stabilised Soil Blocks, Solid/Hollow Cement blocks, Hydraform Bricks• Soil stabilization in road construction

Advantagesoftheproduct• Easiermixing• More workable ‘buttery’ mixes for block/brick layers• Easier laying with higher work rate • Economic value to MHC• Less wastage during plastering and brick/block laying due to enhanced cohesion in the mixes• Cost differential between Kumanga & OPC is MK 300.00 per bag which cumulatively becomes a huge saving• 50 kg Kumanga has bigger volume than 50 kg OPC hence bigger volume mixes for use in rendering plastering and masonry work. ConfidenceThe most significant party in the construction industry: YOU, will get everything you expect from Lafarge, the world-leading cement producer. Our products undergo constant rigorous testing for customer satisfaction guarantee. YOU may also request for weekly product quality certificates so that you have confidence that KUMANGA will:

• have consistent high quality performance • enhance your on site productivity • deliver beyond your expectations • produce superior finishing• give you effective back up service and technical support from our engineers.


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CEMENT CONCRETE SAND1 Wheelbarrow Load

(2x 50kg bags)

STONE5 Wheelbarrow Load

TYPICAL APPLICATION

Mortar for bricklaying &plastering


(2x 50kg bags)

STONE8 Wheelbarrow Load

Brick & BlockMaking Mix

Note: • Use the same container for measuring materials in a batch• 2 x 50 kg Pockets of Kumanga MC22.5 X are = 1 standard (65 litres) buildersʼ wheelbarrow

RecommendedVolumeMixProportions

WhenWorkingWithKUMANGAMasonryCement

Mortar is a mixture of sand, cement and water which is used for bonding bricks and plastering. Plaster is a decorative or protective coating to concrete and masonry walls and concrete ceilings. When mixing mortar, firstly measure your quantity of sand according to your mix proportions and pile it up on a water holding surface, preferably concrete or metal, in a saucer shape to avoid draining water (locally known as mtondo). It is advisable to use a concrete mixer where affordable. Before adding water to the sand piled up on the mtondo, add cement according to the recommended mix proportions and mix thoroughly until the dry mix has a uniform colour. Now you can add water slowly to small portions of the dry mix according to your required volume. Claybricks absorb water from mortar mix resulting in poor adhesion and subsequent cracking of plaster works. Wet clay bricks before laying them and plastering. The walls for rendering plaster should be rough and free of dirt for grip.

OPC

3


ORDINARY PORTLAND CEMENT CEM I 32.5NIntroduction Lafarge Ordinary Portland Cement (OPC) is a general purpose cement developed to have a wide range of concrete and mortar applications from domestic to heavy industrial constructions. OPC is manufactured according to EN 197-1: 2000 Prestandards.

OPC is technical cement that combines normal strength development and performance at all stages with versatility and it is recommended for high specification structures.

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StrengthClass

CompressiveStrengthMPa InitialSettingTime(Min)

Soundness(expansion)

mm

EarlyStrength StandardStrength

2days 7days 28days32.5 N - >=

16.0>= 32.5

<= 52.5 >= 75 <= 10

Product Attributes• Mechanicalandphysicalproperties

• WorkabilityOPC produces very workable concrete mixes that achieve a minimum setting time of 320 minutes which gives you ample time to work with your concrete.

• StabilityOPC concrete mixes have a better response to vibration, filling formwork more completely without aggregates falling to the bottom of the concrete pour before setting.

• BleedingOPC concrete has less bleeding hence less sand streaking along the shutter giving better off shutter finishes.

Note:Ninthestrengthclassdenotesnormalearlystrengthdevelopment


Productapplications.

a) LowStrengthConcrete(15MPa) Suitable for mass concrete and unreinforced single storey foundations b) MediumStrengthConcrete(25MPa) Suitable for reinforced or unreinforced foundations, slabs, footpaths, driveways as well as domestic & light industrial floors c) High-StrengthConcrete(30MPa) Suitable for reinforced concrete, heavy duty floors and precast items such as concrete flagstones.

Note:MPa=MegaPascals:unitofmeasureofforce/pressureperunitarea

Advantagesoftheproduct• It is suitable for high specifications projects • can be used for general cement applications

ConfidenceThe most significant party in the construction industry, YOU, will get everything you expect from Lafarge, the world-leading cement producer. Our products undergo constant rigorous testing for customer satisfaction guarantee. YOU will have confidence that OPC will:

• have consistent high quality performance • enhance your on site productivity • deliver beyond your expectations • produce superior finishing• give you effective back up service and technical support from our engineers.

CEMENT

CEMENT

RecommendedVolumeMixProportions


(2x 50kg bags)

STONE2 Wheelbarrow Load 2 Wheelbarrow Load

TYPICAL APPLICATION

Reinforced concrete (suspended slab, water tight concrete, heavy duty undustrial floors)


(2x 50kg bags)


Medium Strength Concrete (driveway, light industrial floors-unreinforced)


(2x 50kg bags)


Home Concrete (foundations, footing domesic floors – unreinforced)

Note: • Use the same container for measuring materials in a batch• 2 x 50 kg Pockets of Kumanga MC22.5 X are = 1 standard (65 litres) buildersʼ wheelbarrow


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Tipsforsuccess• GoodQualityMaterials

Cement: Kumanga Masonry Cement & Ordinary Portland Cement (OPC)assures you of good quality and reliability beyond any reasonable doubt.

Sand: Clean good quality sand will help you achieve the desired finishing. Sand should not be contaminated with silt, clay or organic matter lest your plaster cracks

Water: Remember, the more the water you add, the weaker the concrete or mortar. Always use clean, good quality water in the optimum quantity that will give a good water:cement ratio and produce a workable mortar suitable for rendering plastering and masonry work.

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w:c ratio = mass of water / mass of concrete

w:c ratio strength

ProtectandCureKeep all your concrete work wet for strength development for at least 28 days. Curing also avoids cracking. Gently spray your concrete work with water or protect it with plastic sheets or wet hessian sacks to prevent it from drying out.

STRE

NG

TH a

s %

of

the

28 D

AY

STRE

NG

TH

AGE (Days)

Not Cured

3-Days Moist Cured

7-Days Moist Cured

28-Days Moist Cured100%

75%

50%


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THEBASICS1.1 Knowthedeferencebetween“cement”,“concrete”“mortar”and “plaster”:• Cement is a manufactured dry powder used as a binding material for concrete, plaster and mortar• Cement is one of the raw materials used along sand and stone to make concrete• Concrete is a composite of all the materials (cement, sand, stone and water) mixed together• Mortar is a mixture of cement, sand and water. • Mortar is a workable paste used to bind construction blocks/ bricks together and fill in gaps between them to give strength and stability to a wall.• Plaster is also a mixture of cement, sand and water but is used as a decorative coating to concrete, masonry walls and concrete ceilings.

1.2 Whatqualityofstoneshouldbeusedinmakingconcrete?• Stone should be clean, hard and have durable particles.• The actual source of stone is less important than the size of the particles. • Single-sized particles are more economical to use. 1.3 Isthequalityofsandimportant?• Yes. The quality of sand has a very marked effect on the quality of concrete and plaster.• Sand with poor grading generally gives a mix that is less workable, less economical and less easy to bring a good finish.• Poor quality sand is the major cause of cracking in plasters• Sand should not contain excessive amounts of clay. • Excessive clay/fines in sand causes cracking and reduces strength of mortar• An excess of fines may lead to an excess of mortar on the surface but this type of surface will wear rapidly under traffic.• Lack of fines in sand results in a harsh concrete which is hard to compact and to bring a good finish.• Do not use sands that the fines may have been washed out.


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1.4 Whatisthebesttypeofsand?• The best sands are “evenly graded” – they contain particles of a wide range of sizes; medium sizes predominates but the coarsest and the finest are also present.• Sand should be clean- grass, leaves, roots etc are harmful.

1.5 DidyouknowthatSandusedforconcreteisdifferentfrom sandusedforPlastersandMortar?• Concrete - River sands give good workability for concrete as they often consist of hard rounded particles, free from clay and reasonably clean.• For plaster and mortar – soft/smooth, loamy and non- gritty sand 1.6 Istheactualsourceofsandimportant?• No. The actual source of sand is not a reliable guide to its quality.• Sand quality can only be determined only by making trial mixes.

1.7 Howcanyouchecksuitabilityofsand?• Do a trial mix using: 5kg cement and 25kg of sand• With good quality dry sand, 5 litres water should be enough to give a good plaster mix• If more than 6 litres are needed: find better sand!

1.8 Doesthequalityofwaterusedinconcretematter?• Yes. Drinking water is normally suitable for making concrete and mortar• Murky or dirty looking water e.g. from a borehole or dam, should be tested by a laboratory before it is used.

1.9 Doesitmatterwhichtypeofcementused?OfCourse!!• All cements are NOT the same even if the description on the bag looks similar!• Each type of cement is manufactured for specific application • ALWAYS follow manufacturer’s instructions and recommendation to achieve the best results.

1.10 WhatfactorsshouldIconsiderinselectingtypeofcement?• The first consideration should always be the PURPOSE i.e where is it going to be used• The impact of the choice of cement on the cost of the application• The strength suitable for the application• If early strength gain is required to save time and money spent on labours and formwork


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1.11 Whatisthebestwaytomeasureabatchofconcretei.ecement, sandandstone?• Weight batching is the preferred method but it requires more sophisticated equipment to ensure accuracy as such, batching by volume is generally used for small jobs and projects.• A standard builder’s wheelbarrow is normally used to measure the correct volumes of cement, stone and sand to make a required batch of concrete.

1.12 Whatisthevolumeofastandardbuilder’swheelbarrow?• A builder’s standard wheelbarrow holds 65litres of material

1.13 Howmanybagsofcementareequivalenttoonestandard builder’swheelbarrow?• A bag of 50kg of cement is approximately 33 litres• Two Bags of 50kg cement are equivalent of 65 litres HENCE 2x50kg bags = 1 standard builder’s wheelbarrow.• On each bag of 50kg cement, a mixing proportion indicating:

1.14 Intheabsenceofastandardwheelbarrowwhatothertoolcan beused?• Any other container/tool can be used such as a bucket, oil or paint drums but the rule is: “Always Use the same size container to measure all the ingredients!”• A shovel is NOT recommended to measure materials as you cannot judge the quantities accurately.

1 Wheelbarrow Load(2x 50kg bags)=


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ORDERING&ESTIMATINGMATERIALS1. CONCRETE1.1 There are three grades/classes of concrete specified for general building work:a. Lowstrengthconcrete(15MPa) Suitable for unreinforced foundations (single storey only), mass fill, infill masonry.b. Mediumstrengthconcrete(25MPa) Suitable for unreinforced slabs or floors, reinforced slabs and foundations, footpaths and domestic drivewaysc. High-strengthconcrete(30MPa) Suitable for reinforced concrete, heavy duty floors and precast items such as concrete flagstones.

Note:MPa=Megapascals:themeasureofforce/pressureperunitarea)

1.2 To order cement, stone and sand, it is important to calculate how much concrete you need.

1.3 Follow the following steps to calculate the area required to place concrete:1.3.1 Measure : the depth or height, length and width of each element in metres1.3.2 Multiply : Height x Length x Width(measured in metres) = Volume of concrete required in cubic metres (m³)1.3.3 Add : volume of each element together using the recommended mixing proportion to calculate amount of material to order

1.4 ALWAYSREMEMBER: 1m³ = 1,000 litres m³ = length x height x width 1 Standard Wheelbarrow = 65 litres 2 Bags of 50kg cement = 1 Standard Wheelbarrow

CEMENT CONCRETE SAND STONE

Low Strength , 10-15MPa

Medium Strength 20-25MPa

High Strength 25-30MPa

5.8 7.7 9.2

650

620

600

10

9.5

9

.65

.62

.60

.65

.62

.60

10

9.5

9

650

620

600

Litres Wheel-barrow m³ Litres Wheel-barrow m³

Table 1: One cubic metre of concrete using 19mm stone (Typical stone)


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1.5TipsonMixingConcreteAlways stick to recommended mix proportions – be accurate and consistent• Work on a clean, hard surface such as concrete floor or metal sheet• Do not mix concrete directly on the ground: • The mix will become contaminated with soil• The ground absorbs mixing water from the fresh mix, affecting workability and potential• The time from mixing the materials to the placing of the concrete should not exceed 45 minutes. If there is going to be delay, cover the concrete with plastic.• If there has been an unavoidable delay before placing the concrete and it resists being turned over a few times with a spade, than it has started to setting. • Do not try to weaken the concrete by adding water. It is better to make a new batch.

1.6TipsonCommonApplicationsofConcrete DomesticFoundations• The performance of concrete floor on the ground depends on underlying material providing support.• Provide a carefully compacted 100-150mm thick layer of suitable fill material immediately below the concrete.• Finish the surface of this foundation layer smoothly. • Where the foundation is wet, dampproofing is necessary. Cover the foundation with polyethylene (plastic) sheeting.• The plastic prevents the concrete from absorbing moisture from the ground below.• Immediately before placing the slab, carefully and thouroughly dampen any foundation or adjacent part of the building not covered with plastic sheeting to prevent absorption of moisture from the concrete.

FloorSlabs• Concrete floor slabs for domestic or light duties should be at least 100mm thick• Do not lay panels larger than 3m² but where rectangular panels are required the length to width ratio should not exceed 1.25.• After placing the concrete, keep the slab covered for at least for at least 7 days to attain full strength and minimize any tendency to crack.


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ScreedsandToppings• Ascreedisalayerofwell-compactedmaterial(cement,coarse sand and water) applied to a floor slab.• The thickness of screeds should not be more than 30mm • A topping is a layer of concrete designed to provide a dense, abrasion resistant surface• Common cause of cracking in concrete floors is poor bond between topping and base course – always ensure a full-depth concrete slab.• Preparation of the surface is of utmost importance to achieve a good bond • Chip the surface and remove all dust and debris• Absorptive surfaces should be soaked to ensure water is not drawn from the screed mix to the surface floor.• Pour the concrete in panels not more than 30mm thick and 3m²• Domestic screed mix is 1:4- using river or pit sand i.e (2 50kg Bags and 4 wheelbarrows)• Do not sprinkle cement powder on the surface to absorb bleed water or to improve finish – the surface will be prone to crumbling and scaling• Do not sprinkle water on the on the surface or finishing 1 PLASTER

1.5 Plasteristhemixtureofsandandcement.

1.6 Sand-cementplasterisusedadecorativeorprotectivecoating forinternalandexternalwalls,concreteceilingsandreservoirs.

1.7 Tipsonplasterandplastering:• Freshly mixed plaster should be uniformly mixed, easily workable and have good water retention.• The receiving surface should be rough and free of dirt, dust and flakes of paints. Roughness improves adhesion by providing a positive “key” for plaster to grip.• Do not make more plaster than can be used in 2 hours. Mix small batches as required. Trying to restore its workability with water will not give satisfactory plaster.• If plastering work is done in direct sun, it should be protected from sun and drying winds for at least 7 days. Periodical watering, covering by wet sack or plastic sheeting and sand application are among means of achieving protection.


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1.8 SandQualityisimportantforplasters:• Poor quality sand is the main cause of cracking in plasters• Pit sands are often the best for plasters• The sand should not have excessive amounts of clay - too much clay requires high water content.• Always remember: source of sand is an indication of quality.

1.9 Workability• Builders lime may be added for improved workability if sand lacks fines or is single sized. Use a maximum of 40 litres of building lime per 50kg of cement.• Do not use lime to replace cement- only as an addition to cement.• Test for workability by tilting the trowel: a good workable mix will slide off. If it sticks to the towel, the sand contains too much clay.

1.10 EstimatingQuantities

1.10.1 Materialsforplastercanbeestimatedbyareai.e.m²

1.10.2 Toplasteranareaof8.5m²,pleasefollowtherecommended mixproportionsshownbelow.

CEMENT CONCRETE SAND

1 x 50 Kg Bag 1.5 x Wheelbarrow Load

RECOMMENDED PLASTER MIXES

CLASS IPlaster recommended for highly stressed units and areas exposed to dampness (reservoirs swimming pools etc)


1 x 50 Kg Bag 2.5 x Wheelbarrow Load

CLASS IICommonly used plaster (Internal & External Walls, Ceilings)


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2 MORTAR 2.5 Mortarisalsoamixtureofcementandsandbutithasthe followingmainfunctions:

2.5.1 Bondbricks/blockstogetherandhelpresistsidewaysforces

2.5.2 Provideanevenbedtodistributetheloadonthewall

2.5.3 Sealthejointsagainstrain

2.6 Mortarshouldbereadilyworkabletoallowtheblock/ bricklayertoproducesatisfactoryworkatarapidrate.

2.7 TipsonworkingwithMortar:• Mortar should be soft, plastic and must spread easily• It must be thoroughly mixed to a uniform colour• Sand should be clean and not have too high a clay content• Joints should be as thin as possible. Thick layers are wasteful in mortar.• Do not make too strong a mortar as it is unnecessarily costly and could lead to cracking• Do not make more mortar than could be used in 2 hours. Trying to restore workability by adding water weakens the mortar.• If mortar has to be left in the sun before being used, cover with plastic sheeting or wet sack.• Clay bricks should be wet for laying• Cement bricks or blocks are laid dry

2.8 Whatisthequalityofagoodbrick?

Check and examine the bricks to be used in a building before they are laid in the wall and they should meet the following requirement:• They should be sound free from crack or flow and from stone and lumps of any kind especially pieces of line• The brick must be uniform in size, with sharp angles and edges, and the surface true and square to each other, this insure neat work• Good building brick should be quite hard and well burned. A simple and generally satisfactory test for common bricks is to strike two of them together, or to strike one with the edge of a mason’s trowel, if the brick give a ringing sound it is generally sufficiently strong for any ordinary work. A dull sound shows the brick is soft or shaky


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• The quantity of water absorbed is also important. A good brick should not absorb more the one tenth its weight in water. A good test is to weigh the brick first then immerse it in water for 24 hours and weigh it again. From the increased in weight, the percentage of water it has absorbed may be found. Very soft under burned bricks often absorb from 25 to 35 percent of water. Weak light red brick, often used in filling the interior of walls, will absorb about 20 to 25 percent while the very best brick may absorb not more than 5 percent and should , if possible be used for outside walls and foundation wall and piers

2.9 DidYouKnow?• The strength of an ordinary brick is 5MPa• Bonding bricks with mortar having strength of around 5 MPa or slightly more (which you easily get when Kumanga is used) gives satisfactory results.• Due to elastic nature of ‘too strong mortar’ if used as binder for ordinary bricks, cracking is enhanced.

2.10 EstimatingMortarQuantities

2.10.1 Tolay1000bricksuse:

• 3 Bags of Kumanga cement and 9 wheelbarrow loads of sand (.6m³)• REMEMBER:50normalclaybricksmakeuponesquaremetre


2 x 50 Kg Bag 4 x Wheelbarrow Load

RECOMMENDED MORTAR MIXES

CLASS IMortar recommended for damp course or load bearing brickwork


2 x 50 Kg Bag 6 x Wheelbarrow Load

CLASS IICommonly used mortar for normal load- bearing applications(laying bricks and blocks)


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COMMONDEFECTS1. Peelingoffofplastera. Whatcausespeelingoffofplaster?• Non-complying materials i.e unclean sand & cement• Incorrect mixing ratios i.e adding too much sand in a mortar material mix.

b. WhatistheRemedy?• Adhere to design mix ratios while using complying materials and re-plaster.

2. Crackinga. What causes cracking of walls • Poor workmanship of brick laying• Use of weak or partially broken bricks• Mortar ‘too strong‘ as a binder for a particular quality of bricks• Laying clay bricks while very dry and failure to periodically moist the binding bed of mortar.

b. Whatisthepreventivemeasure• Professional brick laying hence Umisili initiative by Lafarge Cement Malawi• Avoid using partially cracked bricks during brick laying• Avoid use of ‘too strong mortar’ as binder for ordinary bricks. Mortar made from Kumanga is the most appropriate for brick laying• Wet clay burnt bricks before use and periodically spray water to the binding bed of mortar (at least for one day).

FOUNDATIONTIPSApoorfoundationwillsentenceyourhousetoanearlygrave…• Set out the layout of the house or structure to be built in accordance with the site layout drawings. Make sure that you closely observe the depths of excavations indicated on your drawing

• Choose a well known and trusted brand of cement for your project i.e. Kumanga cement found at Lafarge Cement Malawi and all its appointed agents and distributors is the best cement for all your brickwork


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• Identify a source of good quality sand and quarry, refer to our basic tips to know how you can identify good quality sand and quarry

• Identify a skilled and well trained builder especially under the Lafarge Cement Umisili program. To get hold of such builders near your area, please contact Lafarge Cement offices for more information

• To have a stable base for the foundation, use Kumanga cement to make concrete. To achieve suitable strength use a mix proportion of 2 bags of Kumanga cement, 2 wheelbarrows of sand and 3 wheelbarrows of quarry (stone). Mix this with 30 liters of water (one and a half pale of water)

• Firstly measure and pile aggregate on your mixing surface. Then measure your required sand amount and pile it on top of the aggregate. Before adding water, pile your cement on top of the aggregate and sand and then dry mix it until the whole mix has a uniform colour. Now you can start adding water and continue mixing your small portions. If you have access to a concrete mixer, then your job becomes easier for you.

• Pour the concrete on the excavated floor of the foundation. The thickness of the concrete must be 75mm throughout the foundation. This is called the blinding layer and is very important since it provides a more stable base for the foundation and hence reduces settling of the structure

• After the blinding layer has cured and hardened (at least 2 days after casting), start construction of the foundation walls with good quality bricks, refer to our basic tips to know how you can identify a good quality brick

• Prepare a Class III mortar mix. To achieve this measure 2 bags of Kumanga cement against 8 wheelbarrows of well graded sand. Please note that 2 pockets of 50 kg Kumanga MC22.5 X are equal to 1 standard (65 litres) builders’ wheelbarrow.

Remember,thestrengthofyourmortardependsonyourwater:cementratio,morewater,lessstrength!

Settling is the periodic sinking of the structure or house. The total allowable settling for a structure is 20mm orless. Settling of more than 20mm causes the structure to be unstable and to crack or even collapse


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• Once a Class III mortar mix is prepared with a qualified Umisili builder, build the foundation wall. Make sure it is well leveled and positioned as per the drawings

WALLTIPSAwellbuiltbrickwallmusthaveafootingsizedforpropersupport

• Choose a well known and leading branded masonry cement. Kumanga cement is just the best cement from Lafarge Cement Malawi that was tailor-made to meet perfectly your masonry requirement

• Identify a clean and good quality sand for your mortar mix

• Identify a source of good quality bricks

• Source a well trained and knowledgeable builder in your area, preferably, one who has been trained through the Umisili program by Lafarge Cement Malawi

• Brick wall are intended to be laid as a veneer wall (meaning against another wall, like on a house)

• Make sure you have all the tools that will be needed• Start by putting a brick down at each end of where you want the wall to go. Don’t put any mortar down yet. Measure from the outer edge of the brick at one end to the outer edge of the brick at the other end to get the length of the wall

• Now that you have measured you can start laying bricks at both ends. Prepare a class III mortar mix. To achieve this measure 2 bags of Kumanga cement against 8 wheelbarrows of well graded sand. REMEMBER, THE STRENGTH OF YOUR MORTAR DEPENDS ON YOUR WATER:CEMENT RATIO, MORE WATER, LESS STRENGTH. Put your level on top of them and make sure the bricks are level. Measure away from the wall on both ends of the bricks that you just laid. Put your level against the face of the bricks to make sure that they are straight

• After you have a couple of courses laid on both ends, hook a line up at both ends, so it lines up with the very top of the bricks. Now you can go through the middle and lay every brick to the line


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• Keep laying your ends up then fill in the middle till you get to your destined height. Make sure you check with a level in the middle of the wall time and again to make sure that it is staying level. If one side gets too high, lay the bricks tighter on the end.

FINISHINGTIPSThe aesthetics of your home is primarly dependant on the quailty of your finish - so get it right:

• Plastering• Pointing• Floor• Drainage• Driveway


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Storing andHandling Cement Before handling cement, take a momentto look at the top priority in any task - theSafety issues:

Cement is such a commonly available product that many people will have used it without giving any thought to their personnel protection. Although cement poses little immediate hazard, it is important to take sensible handling precautions.

Personal ProtectionSuitable protective equipment (goggles, masks,boots and gloves) and clothing should be worn during the handling of wet or dry cement.

Cement is designed to react strongly with water and go hard, therefore:

Protect bags of cement from rain, moisture in the ground and moisture from the air. Preferably store pallet loads and loose bags in a warehouse or weatherproof shed:

- keep loose bags off the ground/floor. (Use plastic sheeting or spare pallets)

- stack pallets only two high (three high is unstable and will be a SAFETY HAZARD)

- close windows and doors to stop damp air blowing over the bags

- make tidy stacks with wide aisles so that forklifts do not tear the bags

Stored cement must not be exposed to moisture

Storing Bags of Cement


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If material has to be stored outside:Preferably cover palletised loads with a waterproof tarpaulin to provide additional protection against the elements. Stack loose bags on a platform of spare pallets or timber slats covered in plastic sheeting:

- Cover the bags with sheeting

- Create a ridge for the sheeting so that rain runs off

- Weigh down the edges of the sheeting with stones or timber to prevent winds blowing it away

Planning your stacks:Arrange your stacks so that the first-in cement can be the first out (FIFO). This is important because even well-stored cement will begin to deteriorate after approximately 3 months.

Do not store cement next to products such as gypsum-based building materials, fertilisers or other chemicals. Small amounts of contamination can cause a big problem with the cement.

Forklift drivers should be made aware of the cost of bag breakages. A breakage means cement is lost and time is also lost clearing up:

- Bags should be staked under cover on spare pallets on a flat, level area that has been checked free of sharp objects

Handling Bags of Cement


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Lifting should be carried out with the forklift tines parallel to the floor to avoid overstressing the pallet.Remember:

- not to overload the forklift (many forklifts are only deisgned to lift one pallet at a time)

- not to damage the wooden slats or the bags when inserting the forklift tines into the pallet

- to stack the top pallet neatly on the bottom one

- Persons who are not trained to handle cement bags (usually 50Kg) can easily hurt their backs when lifting or manhandling full bags by themselves. Lifting should preferably be done by two people.

- Lift bags by bending the knees and keeping a straight back to minimise the chance of back strain.

- Always lift a bag by putting hands underneath to support it, never by holding the ends. This bends the bag and can cause the bottom to tear open.

Manual handling must be done carefully to avoid damaging the bag or injuring the handler:

- Do not drop bags of cement from head height or from the bed of the truck


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- Always roll a bag over before lifting it. Check the underside of any damage. Rolling also loosens the cement and reduces the chance of the bag splitting.

- Never drag a bag over a pallet, a floor or bed of a truck. Instead always roll it.

- Never walk on the cement bags.

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Lafarge Cement Malawi Ltd.

Makata Heavy Industrial Area,P.O. Box 523, Blantyre, Malawi.

Tel: +(265) 1 870 031Fax: +(265) 1 871 026

www.lafarge.com

September 2010

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