repaire and rectify

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Sector: ConstructionOccupation: Masonry l 2

Unit of Competency: REPAIR AND RECTIFY MASONRY STRUCTURE

Module Title: REPAIR AND RECTIFY MASONRY STRUCTURE

Institution:Alamata Tvet Center(alamata, Tigray, Ethiopia)



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CONTENT

TITLE PAGE

INRODUCTION 1

SUMMARY OF LEARNINIG OUT COMES 1

HOW TO USE THIS TTLM 2

LEARNING GUIDE 2

INFORMATION SHEET =1 2

INFORMATION SHEET =2 3

INFORMATION SHEET=3 4

OPERATION SHEET=3 5

Self- check= 3 6

Model ANSWER=3 7


OPERATION SHEET=4 9


OPERATION SHEET=5 11





LAP TEST 15



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Introduction

Welcome to the module “ REPAIR AND RECTIFY MASONRY STRUCTURE ”. This learner’s guidewas prepared to help you achieve the required competence in ““Basic Apparel Production Level2 ”.”. This will be the source of information for you to acquire knowledge and skills in this particularoccupation with minimum supervision or help from your traines. mary of

LEARNINIG OUT COMES

After completing this training guide you should be to;

LO1: plan and Prepare for workLO2: Locate damaged section of masonry structureLO3: Install lifting/lowering equipmentLO4 Remove damaged structureLO5 Select matching componentsLO6 Replace components

Lo7 Cleanup work area, tools and equipment’s

HOW TO USE THIS TTLM

Read through the learning guide carefully. It is divided into sections that cover all the skills &knowledge that you need.Read information sheets &complete the self- check at the end of each section to check yourprogress.Read &make sure to practice the activities in the operation sheets. Ask your trainer to showyou the correct way to do things or talk to more experienced person for guidance.

*when you are ready ask your trainer for instructional assessment and provide you with feed-back from your performance.



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LEARNING GUIDE

Learning activities Special activities

Read topic plan & prepare Refer to I formation sheet# 1

Answer self- check 1 Compare your answer with modelanswer# 1Read topic: Locate damaged section ofmasonry structure

Refer to information sheet# 2

Read topic: Install lifting/loweringequipment

Refer to information sheet #3

Answer self- check 3 Compare your answer with modelanswer#3

Read topic: Remove damaged structure Refer to information sheet #4

Read topic Select matching componentsRefer to information sheet #5

Read topic Replace componentsRefer to information sheet #6

Read topic Cleanup work area, tools andequipment’s

Refer to information sheet #7

INFORMATION SHEET ONE LO1

A work plan is an outline of a set of goals and processes by which a team can accomplish thosegoals, offering the reader a better understanding of the scope of the project.Work plans, whether used in professional or academic life, help you stay organized whileworking on projects. Through work plans, you break down a process into small, achievable tasksand identify the things you want to accomplish.Learn how to write a work plan so that you can be prepared for upcoming projects.

LO2 Locate damaged section of masonry structure

Located damaged section is, clearly identified and confirmed with architect’s requirements.Determined Extent of damaged section and overall dimensions of replacement stone correctly.Superficial or fine cracks are generally removed by treating the surface with while wash, softdistempers, silicate cement paints, etc.Cracking of concrete structures can never be totally eliminated, but practitioner should be awareof the causes, evaluation techniques, and the methods of repair.Before remedies are sought, correct diagnosis will decide whether ratios factory repair ispossible.The development of cracks and their repair is a perpetual problem involving considerable costand inconvenience to the occupants.



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The structural cracks may be active and dormant crack where a movement is observed tocontinue is termed active, whereas the crack where no movement occurs is termed dormant astatic.

The following information may help in diagnosing the cracks.

i) Whether the crack is new or old

ii) Type of crack i. e. whether it is active or dormant

iii) Whether it appears on the opposite face of the member also.

iv) Pattern of cracks

v) Soil condition, type of foundation used, sign of movement of ground.

vi) Study specifications, method of construction used and the test results at the site.

The various aspects of the problem are follows.

a) Cracking due to weathering

b) Cracking due to carrion of reinforcement

c) Cracking due to poor construction practices

d) Cracking due to construction over loads

e) Cracking due to errors in design and detailing

f) Cracking due to extremely applied load

LO3 Install lifting/lowering equipment

Lifting equipment

'Lifting equipment' means work equipment for lifting and lowering loads. This includes lifting accessories and attachments used for anchoring, fixing or supporting the

equipment.

Examples of lifting equipment include:

overhead cranes and their supporting runways motor vehicle lifts vehicle tail lifts and cranes fitted to vehicles a building cleaning cradle and its suspension equipment lifting accessories

Lifting accessories are pieces of equipment that are used to attach the load to lifting equipment,providing a link between the two. Any lifting accessories used between lifting equipment and theload may need to be taken into account in determining the overall weight of the load.



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Examples of lifting accessories include:

Fiber or rope slings chains (single or multiple leg) spreader beams magnetic and vacuum devices



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SELF CHECK 3

Answer the following questions

1. Write lifting accessories. 2. Define 'Lifting equipment'



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LO4 Remove damaged structure

Damaged section is accurately and safely cut out to predetermined dimensions without damageto surrounding stone.Waste materials are safely lowered and removed from site in accordance with job and OH&Srequirements.Bedding planes to support replacement stone accurately formed to minimize size of replacementstone.When considering the removal of any one of the load bearing members, masonry building, thestructure above must remain stable, but it does not need to remain serviceable in this theoreticalsituation.In designing for the removal of a load bearing wall, the partial safety factors that have to be usedare reduced.The Approved Document allows limited collapse of parts of a structure when a vertical supporthas been notionally removed,

OPERATION SHEETOPERATION TITLE : Remove damaged structure

PURPOSE : - TO KNOW MORE ABOUT DISPOSAL SYSTEM

TOOLS AND MTERIALS :-wheel borrowspadetrowel

PROCEDURE :-Prepare disposal tools

PRECAUTION:- Use safety tools and materials. Care from sharp materials.

QUALITY CRITERIA :-the students can evaluate his success in performing the operation.

LO5 Select matching components

Color and type, materials and styles of existing complex stone components associated withopenings, arches, string and plinth courses, straight and curved walling copings identified andmatched with replacement stone to architect's specifications.



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LO6 Replace components

Dimensions and profile of replacement components are correctly determined and appropriatetemplates made.Replacement and profile components are accurately worked to match dimensions.Replacement components drilled/ slotted for dowels/brackets in accordance with fixingspecifications.Replacement components correctly handled and raised to position for placement.Components placed, fixed and bedded in location with adhesive or mortar according tospecification.Vertical joints filled with mortar or sealant, where applicable, to specifications.Stonework cleaned using dry, liquid or chemical means in accordance with type of stone lay.

Methods of Repairing

Objective : - After completing the learning element the trainee will be able to methods of repair

depending on the condition of the concrete to be repaired. The repair of cracked or damaged structure can be done using different methods. Simple method

of repairing concrete which is called ordinary procedures is explained.

Ordinary Procedure

External or fine cracks are generally removed by treating the surface with while wash, soft

distempers, silicate cement paints, etc. The methods and materials used for the repair of patches

of deteriorated in the structures are described and the repair is carried out in two stages.

(I) Preparation Surfaces

The cracked and weaken areas are chipped out to the solid concrete. The edges should be cut out

as straight as possible and right angled to the surface with caners reminded with in the hole.

The edges are slightly (somewhat) undercut to provide keys at the edge of the patch.

The thickness of the edges should not less than 25mm to prevent(to stop ) then from breaking

under load.

All the loose material should be cleaned and the surface should preferably be watched out before

actual patching work is started.

Care should be taken to remove excess water from the cavity.

The grout mix and the quantity of mixing water should be the same as that of mortar in the

replacement material. The patching material should be filled in before the layer of grout dries.

(II) Filling of the Patch

The material to be used for patching may either be mortar or concrete depending upon the

extent of repair.



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The methods generally used for filling the material are:-

a) Dry packing

b) Concrete replacement

c) Mortar replacement

d) Grouting

e) Pre packed concrete

Dry Packing

The method consists of the hand placing of low water content mortar in to slats followed by

tamping or ramming of mortar into place, producing intimate contact between the mortar and

the existing concrete. Because of the low water-cement ratio of the paste, there is little

shrinkage, and the mortar provides a durable, strong and water tight patch.

The portion of the dormant (non-active) crack adjacent to the surface should be widened to a

slat about 25mm wide and 25mm deep with a power driven saw tooth bit.

The slat should be undercut so that base width is slightly greater than the surface width. After

the slot is cleaned and dried, a bond coat consisting of cement slurry equal amount of cement

and fine sand mixed with water to a fluid paste consistency, should be applied.

A mortar consisting of one part of cement to three part of sand passing a 1-18mm sieve and just

enough water to make the mortar stick together when molded into a ball by hand is placed in the

slat immediately.

The water content for the mix should be carefully chosen because excess water will increase

shrinkage which may loosen the replaced material, where as less water will not make a sound

solid pack.

The dry pack material should be filled properly in compacted layers of about 10mm thick. Each

layer being scratched before placing the succeeding layer to secure good stick of about 200 to

300mm long the and up to 215mm diameter with a hammer.

Most curing can be done by supporting a strip of folded wet burfap along the length of the crack.



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Concrete Replacement Method

This method is used for large and deep patches like these encountered in the repair of old and

weaken portion of concrete structure where concrete is to be placed to a minimum depth of

150mm.

The general Applications of this method are in the repair of walls, piers, parapets and for re

facing walls and waterways.

In plain concrete, the substandard area is prepared as explained earlier, but when the repairs

are to be made in the reinforced concrete, the reinforcing bars should not be left partially set in ,

but at least 25mm clearance should be provided around each expired bar.

In case a wall repairs, the top of the hole should be cut to a fairly horizontal line with a 1 to 3

upward slope from back towards face to prevent formation of an pockets at the top during

vibration.

The bottom and the sides of the hole should be cut sharp and approximately square.

All form work points should be mortar tight. Before placing the front sections of form work for

each lift the surface of the old concrete should be crated with cement grant having the same

water cement ratio so that for the mortar in the replacement concrete.

To reduce shrinkage, a minimum period 30 minutes is allowed to elapse between the lifts. The

water cement ratio of the replacement concrete should be the same as that used in the new

structure. The striping time may vary from 20 to 48 hours depending upon the location and

extend of repair.

Mortar Replacement Method

The method is suitable for cavities which are too wide or two shallow for dry pack and

concrete replacement, respectively.

It is used for shallow depressions no deeper than the far side of the reinforcing bars nearest

the surface. For replacement of deteriorated concrete, the method is suitable for miner

restorations.

The mortar replacement can be done by hand or can be applied by using small pressure guns. For hand placing, the mortar should have to same part the mortar used in the mix of which is

made. In the case of pressure gun, the ratio recommended is 1 part of cement to 4 parts of

sand.



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Grouting

The wide and deep cracks may be repaired by filling them with Portland cement grout.

The grout mixtures may contain cement and water of cement plus sand and water,

depending upon the width of the crack. However, the water-cement ratio should be kept as

low as practicable to maximize strength and minimize shrinkage. Water-reducing admixtures may also be used to improve the properties of the grout. The

procedure consists of cleaning the concrete along the crack; providing built-up grout spaces

at gaps, close the crack between the spaces with a cement paint.

The method is particularly useful for repairing wide cracks in gravity dams, concrete walls,

etc.

Pre packed concrete

This type of concrete is used to repair old works and is generally adopted when the

conventional placing of concrete is difficult.

It is advantageously used on larger repair jobs, under water placement, resurfacing of dams,

and repair of tunnel linings, piers and spillways.

It is made by forcing mortar into the voids of a compacted mass of clean and well graded

coarse aggregate in the form.

The aggregate is wetted after compacting it and then grouting is done by pumping the mortar

into the forms.

It must contain the repair member or area in a form of sheet metal or other similar material

and seal the bottom. The aggregate is then placed in the form and grout lines are attached to

inlet plugs.

(iii) Curing of Repair Work

The curing of patch material requires much more care than required for a complete structure.

There is a tendency of old concrete around to absorb moisture from the replacement material.

The curing methods commonly used are:

I. Horizontal repaired surface can be cured by pending or by placing wet gunny bags.

II.Damp or wet burlap protection s can be used.

III.Where the above two methods are not applicable, membrane curing can be used.

Original curing with water followed by membrane curing is very effective.



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Lo7 Cleanup work area, tools and equipment’s

It is essential to clean the damaged surface if repairs are to be successful. This can be done in

a number of ways, depending on the size and accessibility of the repair.

Cleared work Area material, tools maintained equipment and stored. Waste and unwanted material disposed of safely. Unused materials stored.

LAP TEST PRACTICAL DEMONSTRATION

NAME_________________ DATE_____________TIME STARTED_________ TIME FINISHING________

INSTRUCTION:ANSWER THE FOLLOWING QUESTION

1. How can repair masonry structure?

repaire and rectify

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