concrete task 02

8/18/2019 Concrete Task 02

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Unit : Concrete Design TechnologyTask : 02

Student ID : 504585 EN No! :Candidate Na"e : #!# Channa $riyade%aDate o& Su'"ission : 2(!04!20)*



CONCRETE DESIGN TECHNOLOGY TASK NO 02

INTRODUCTION

Today

construction industry is solely developing

around the concrete where its adaptability of change

of qualities when change the involvement of its

ingredients cements aggregates or water! "or that concretes

are put through some comple# process which involvement of comple#

machineries and high demand of labor concentration!

Page | 2SKILLS COLLEGE OF TECHNOLOGY




T$%&' O" CONT'NT

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Task 2.1 Describe methods (process) used to produce concrete

Considering different methodologies and wor5 involved concreting process can be divided into multiple

stages

• %atching

• 6i#ing

• (lacing

• 7andling





• transporting

• Compacting

• Curing

• "inishing

Batching

%atching Is measuring the ingredient amount of the concrete! %atching can be done in two different ways

they are by volume and by weight! 'ach way has different methodologies wor5 advantages and

disadvantage

8olume batching

8olume batching is the method which ingredients of concrete are measured in volume for the

proportioning! %atch bo#es or gauge bo#es are used to measure the aggregate volumes and for 4*5g

cement bag cement volume will equal the volume of gauge bo#! Normally nominal proportion mi#tures

are used and volume batching are popular for small construction wor5 where the uniformity of concretewill be relatively unimportant!

9eight batching

this method is performing by measuring ingredients by weight! "requently in design concrete mi#es this

type of batching method is used!

&atter method is considering most accurate because it is based on proportion of material by weight butformer method is widely used because of the simplicity!

Mixing

purpose of mi#ing is to distribute all the ingredients in a concrete mi# uniformly in the paste! It fulfills by

either rotating or stirring the mi#! To avoid adverse outcomes li5e segregation ma#imum mi#ing time

should be calculated considering following facts!

Type of mi#er

,i:e of mi#er

,peed of rotation

$ggregated properties





Charging

"ig .!. 0 concrete mi#er

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Placing

(lacing concrete is putting adequate concrete amount in to different places without degrading the

characteristics of concrete and quality of the construction!

9hen placing concrete following factors should be considered

6aintain the qualities of concrete

9ater cement ratio

6inimum air percentage

&ess slump

$void segregation

6itigate e#cessive hori:ontal movement

$dequate consolidation

)ood placement capacity

Choose suitable equipment

Trimming the subgrade

,ubgrade moistening

Compacting the subgrade

9hen concrete placing following should be avoided

o ,aturated subgrades should avoid to maintain bearing capacity

o "ro:en subgrade deposits

o Do not Deposit continuously

o Do not place layer within layer until before former layer sets





Compaction

During all the stages in concrete manufacturing air get trapped in concrete mass

6ain purpose of compaction is to remove the entrapped air in concrete mass

'ntrapped air reduces the strength of concrete and hamper the durability 4< of voids reduces3*< and .*< reduces 4*< of its strength

6ethods of compaction

.! 7and compaction

+! 8ibration compaction

3! (ressure and =olting compaction

/! ,pinning compaction

inishing

Concrete finishing is process which to provide uniform aesthetic durable concrete floor! Depending on

the surface finishing methods are differs as following

"ormed finish

It is the finishing method used for concrete pouring to formwor5! "ormed finish possess

different variations!

%asic finish

(lain finish

,pecial finish

Unformed finish

It is finishing method used to non>formwor5s such as payments and wal5ways

%asic

Ordinary

(lain

,pecial

,pecial concrete finishes

)rit blasted surface finishes

$cid etched surface finishes

Tooled surface finishes

Curing

Curing is the process of maintaining adequate moisture and temperature for hydration process

immediately after the placing and finishing of concrete! (roperly cured concrete results to improve

important qualities of concrete as strength water tightness free:ing and thawing resistance absorption

resistance durability volumetric stability





"ig .!+; > curing of concrete floor

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"ollowing are the numerous curing methods used in construction but burlap sprayed with water is suitable

for most concrete curing!

(onding and immersion

"ogging and sprin5ling

9et coverings

Impervious paper

(lastic sheets

Internal moist curing

,team curing

Insulating blan5ets

Transporting

9hen transpotiing concrete following factor?s integrity should be avoid

.! 'arly stiffing

"lash or false setting

$ccelerated hydration

+! Delays





Due to ineffective route planning

Ineffective labor management

'rrors in equipment selection

Unforeseen incidents disasters

3! ,egregation

'rrors in placing method

Using inappropriate mi#ing rate

/! Drying out

Due to hotness and the dryness of weather

Use of admi#tures and silica fumes that results water bleeding





Task 2.2 !xplain "actors considered in the rein"orcement o" concrete

Reinforcements are mainly used for improve the tensile strength of the concrete and also can used for

withstand compulsive loads preventing bac5ings and crac5ing! %ased on structural calculations structural

design for the reinforcement should be calculated included commodity of reinforcement cross section

and the location! )enerally bar arrangements are based on

,pace available in concrete member

Depth of concrete which covering by reinforcement

,i:e of coarse aggregates

,i:es and numbers of bars to be installed

Covering for reinforcement

Concrete covering for reinforcement should be provide for the protection and for the durability for the

reinforcements! ,uitable concrete cover should be provided intended generally for following purposes!

"ire resistance

(revent from e#posure conditions

"or bond and anchorage

"ire resistance

structural design should be able to withstand a fire! stages of structural collapsed under fire are

crac5ing and local damages yielding of reinforcement and large displacement with suspensioneffects! Reinforcement should be suitable anchored to this from thic5ness of concrete cover type

and si:e of aggregates

'#posure conditions

Relevant specification for concrete should be applied referring relevant codes and guidelines

based on the environmental and ground condition of the construction!

%onding to concrete

%ond and anchorage

The properly adheres cement that bond with the reinforcements are ma=orly contributes to transfer

the tensile stress form the concrete to reinforcements! Therefore reinforcements should be clean

and free from rusts oils greases stri5ing agents! Under load reinforcement tends to slip out from

the original position therefore adequate adhesion between cement and reinforcement is important!

Technique often used to prevent reinforcement slips is to hoo5ing or bending the reinforcement in

terminals





"ig +!.; > Reinforcement bending methods


$ssembling and securing of reinforcement

In different types of reinforcement designs are used in different structures in beams and columns

structural designs are shaped as a cage while in slabs reinforcement designed as a net or mat! To hold

reinforcement in positions lin5s or strips are used! These lin5s also provide the anchorage of

reinforcement!

&ocation and placement of reinforcement

"i# spaces and fi# places for reinforcement is necessary for ensure the adequate cover for reinforcement

and to prevent displacement while placing and compacting of concrete





"ig +!+; > concrete spacer


,pacer bloc5 can be made from plastic metal or concrete! This bloc5 can bind with reinforcement on site

using high quality non corrosive binding wire

"ig +!.; Concrete wheel spacer "ig+!+; concrete mesh spacer

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Page | SKILLS COLLEGE OF TECHNOLOGY




Task 2.# Describe ho$ plant and e%uipment is used in concreting

Concrete should be mi#ed thoroughly until its components are uniformly distributed! 6i#ing can be done

by

.! Using hand shovels

+! ,tationary mi#ers

3! Ready mi# concrete mi#ers

6i#ing using hand shovels

6i#ing of concrete using hand tools wheelbarrows li5e shovels is less output process with

following disadvantages

Need considerable labors

7ard to gain the desired properties of concrete

,low process with less economical outcome

"ig 3!.; concrete mi#ing using hand shovels


.! ,tationary 6i#ers





,tationary concrete mi#er Consist of tilting or non>tilting drum with open revolving blade or paddle!

Capacity Is up to 2m3! These mi#ers are used when =ob site concrete is needed

"ig 3!+; ,tationary mi#er


+! Ready mi# concrete mi#ers

Ready mi# concrete mi#ers use to provide fresh and non>hardened which produce off site! They can be

manufactured with any of following method

Central 0 mi#ed concrete

6i#ed completely is stationary mi#er

Delivered in agitated or non>agitated truc5

,hrin50 mi#ed concrete

Concrete which partially mi#ed in stationary mi#ers are completed mi#ing in

shrin5 mi#ers!

Truc5 0 mi#ed concrete

6i#ed completely in truc5 mi#er

$fter mi#ing concrete should be appropriately handled and transported before early stiffening!

Transporting and handling can be done in many ways

Concrete Transporting Methods





9heelbarrows and buggies

used in shallow flat hauls onsite construction

ideal on inside =obsites

slow and intensive labor requirement

(umps

Distribute concrete from central discharge point to all formwor5s in the site

$dvantage of this method is pipeline consumes less space it can be e#tended

mobility and ability to stream continuously

%ut it needed continuous supervision to avoid segregation

Dump truc5s

There are two 5inds of dump truc5s are used in transporting concrete

.! $gitator truc5s

$ vehicle combined with agitator body concrete mi# being rotated throughout the travel time to provide

freshly mi# concrete from point of mi#ing to the placing!

Used for; > used for transport concrete for all used distance within reach of .!4h travelling

$dvantage; > operated from central mi#ing plants

,pecial requirements; > concrete should deliver within .!4hours and onsite crew and equipment should be

ready to handle concrete





"ig 3!3; agitator truc5


+! Non agitating truc5s

Truc5s which not having agitation system

Used for; > transport concrete on small distances on smooth roads

$dvantages; > cost of the truc5 is less than agitator truc5

,pecial requirements; > limited slump should be maintained segregation should be avoided Discharging

done at a higher point

"ig 3!/; Non agitator truc5






,5ip buc5ets

Used; > attached to cableways cranes and helicopters

$dvantages; > 'nable full versatile of cranes cables and helicopters

'nable to overcome natural barriers @height water lac5 of accessA

Clean discharge

,pecial requirements; > buc5et si:e is depending of the si:e of the concrete batch and capacity of placing

equipment

"ig 3!/; s5ip buc5et






Concrete &andling !%uipments

Concrete compaction vibrators

,urface vibrators

,urface vibrators are applied to top of concrete surface for downward compaction

Used in compacting and leveling of slabs floors pavements and all the flat surfaces

The most common type is double vibrating beam screed

Immersion vibrator

Immersion vibrators are used to compact inner concrete on a surface

"ig 3!/; wor5er using immersion vibrator






"ig 3!/; parts of immersion vibrator


The radius of the vibration action of the machine is depends on the diameter of the head amplitude and

frequency! 6ost vibrators have vibration radius of .**mm to B**mm!

(ower trowels and floats

These are light construction machinery which used smooth the finish of concrete floor! There are few

types li5e ride on power trowels which operates sitting up and riding the machinery and wal5 behind

power trowels where operator handle the trowel by wal5ing behind!

,cabblers

,cabblers are the compressed air machine which used for remove thin layers of concrete from the

surfaces! it also uses for add decorative patterns to concrete! It achieved with tipped roads witch attached

in the bottom pounding the surface in rapid succession





Task 2.' !xplain "actors considered in the use o"" "orm$ork and "alse $ork in concreting

"ormwor5 is term used for the temporary container which use to support and form wet concrete until it

gained enough strength to be self>supporting! Usually they are made from timber metal or plywood!

"ormwor5 should be adequately rigid to maintain the desired line and level and sufficiently tight to prevent loss of bleeding of water and mortar! ,i:es weights arrangement of formwor5 should be

allowing to ease of handling erection stri5ing and reusability

!

"ig /!.; framewor5 and falsewor5

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"alse wor5 is the temporary system of support for formwor5! "alse wor5s includes ad=ustable steel props

fi#ed as struts to the sides of foam wor5! Under a load false wor5s are prone to movements and

displacement and when concrete is placed and compressed falsewor5s are tend to displace To increase

the load bearing capacity and the stiffness of the falsewor5 hori:ontal and diagonal braces are added tothe design of falsewor5 points where multiple falsewor5s are tight together at different intermediate

points as a single unit!

%oth formwor5 and falsewor5 should be adequately resilient enough to support the weight of wet

concrete and pressure from placing and compacting the concrete!





"alsewor5 are usually under stress 2*< of their bearing capacity! ,election of materials and design of

falsewor5 must be considerate about installation stri5ing ability and reusability! "alsewor5 capacities

should be chec5ed before purchasing and effects of permanent environmental and imposed loads

! %, 424 code is stated that considering wor5man?s safety during erection all the falsewor5 should

design to withstand +!4< of the vertical load acting hori:ontally! During the design installation and

utili:ing of formwor5 quality wor5manship and frequent precise inspection will ensure the safety of thewor5man!

,tri5ing of "ormwor5

,tri5ing of formwor5 is the term used when dismantling the formwor5 after concrete gained enough

strength! It is determined by the test results outcomes from cube tests!

Removal timing of formwor5 is depending on the rate of concrete?s strength gain in cold weather

hydration process is depleted therefore concrete strength gain is delayed! In that 5ind of temperature rapidhardening concrete can be used!

"ormwor5 removing process should be careful to not results damage to the concrete surfaces specially to

the edges! uic5 removal can be effect impulse load on the concrete! $fter removal of formwor5 surface

should be covered with polythene or wet burlap about 4 days to fully cured the concrete! 7eavy loads

shouldn?t be placed on the concrete immediately and should only be placed after properly cured and

properly tested!

,tri5ing $gents

,tri5er agents are applied inner face of the formwor5 to ensure easier stri5ing minimi:e the discoloringand decrease the formation of blowholes! "or the purpose of easier stri5ing interfaces of formwor5 are

wetted thoroughly from water before .+ hours before concrete placing!

Uneven colors of concrete happen due to different amount of water absorption in the concrete surfaces

and blowholes are the outcomes of the entrapped air between the formwor5 and the concrete surface!

$pplying mould oil with emulsifying agents in to the formwor5 surfaces will avoid the discoloring

boreholes and it will help to the stri5ing! %ut e#cessive stri5ing agents must not be applied because it will

result retardation in hydration process and it will reduce the bondage between reinforcements and the

concrete!

Reasons for formwor5 and falsewor5 failures

• Improper connections

• '#cessive vibration or consolidation of concrete

• Improper bearings

• '#cessive stri5ing

• errors in design of falsewor5





• 'rrors in placement of falsewor5

• &ac5 of strength in formwor5

• Noncompliance of codes specifications and standards

• Improper modifications

• Negligence of supervisions

• Unsuitable bracings• '#cessive pouring rate of concrete!

(revention from formwor5 and false wor5 failures

"or ensure safety wor5ing enviroment ris5s which arisign when erecting utili:ing and dismantling of

formwor5 and falsewor5 should be eradicated as following

(reparation of fromwor5 plan including drawing and written specification for fabrication

erecting and dismantling

Compliance with all the codes regulations and ordinance regarding falsewor5 and falsewor5

(ost signboardsguidelines to ensure wor5ers safety "ollow instructionprocedures and guideline provided by the manufacturers

Carry out surveys and inspections reguralry for earthfills debris overhead wires

(rovide safety equipments for wor5ers

Inspect all the formwor5 and falsewor5 material before using





Task 2. !xplain health and sa"et *best practice *to be "ollo$ed $hen concreting

6ethod statements are used in construction to ma5e sure get the desired outcome without substantial

in=ury or loss of person or property! 6ethod statements are prepared in pre>construction stage for the

ma=or activities in the pro=ect! 6ethod statement provide the necessary communication between the

parties relative to the activities before the start!

During a construction a pro=ect specific legislations li5e 7ealth and safety at wor5 act management of

health and safety at wor5 regulations and construction design and management regulations are

mandatory to follow and comply in order to ensure the health and safety of the wor5er by identify ris5s

and eliminate them in the design stage and ensure cooperation between wor5ers!

In the process of identify the ris5 ris5 assessment files are made to find out the ris5 associated with the

activities in the pro=ect!

7a:ards identifications

(resume the way it happens to whom

Refer to previous records of such incidents

'valuate ris5 and state precautions

In concrete manufacturing process following ris5s are avilable and solutions for them should be applied

Ris5s in concrete manufacturing

'#cessive e#posure to cement dust results irritation of eye s5in and respiratory system

Improper safety arrangements in equipment

"alls trips and slips

Chemical burning

"ormwor5 and false wor5 failures





CONCL!SION

Concrete is a worldwide effective construction compound where it undergone lot of processes with

machines materials chemical to be effective in respective environment! &ot of planning methods

testing innovations and legislations are undergone to develop its effectiveness in to ne#t level and provide safety to the wor5ers occupants and the environment!





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concrete task 02

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