Exercise 5

1. Standard Forms of Building Contrtacts will normally require Contractors to provide TWO ( 2 ) types of indeminities to the Client . Identify and describe these indemkinities with example .

1)  Indemnities against claims losser from damage for example at case of fire  , theft and vandalism .
      Insurance
   Insurance injured against third party when fire happen the material of the thrid party will also make she / he lose .


2. Contractors will normally purchase insurance to protect themselves from loss and liability . Identify and describe FIVE ( 5 ) different categories of Insurance Risks ( not events ) that the Contractor will normally insure against .

- EMployer liability to employees - Contractor shall take and maintain in the joint names of employer , contractor , sub-con in respect to personal injuries / death & injury / loss and damage of property due to work excavation .
- THird party liability - The policy shall cover 3rd party liability for personal injury / death / damage to property
- Damage property - Event of fire , theft , vandalism  and breakage
- Insurance of work - Contractor shall take CAR ( Contractor all risk ) insurance policy for a value not less than the contract sum under joint names of Employees , COntractor and sub-con including professional fees and removal of debris .
-Contractor have insurance for plant , mechanaries and equipment .

3 ) Identify 5 types of events or perils which the Contractor will  need to cover against loss .

•  Fire 
• Lighting 
• Explosion 
• Earthquake 
• Volcanism 
• Tsunami 
• Storm 
• Cydone 
• Flood 
• Inundation 

4. Explain the meaning of the term " Performance Bond " and its purpose . 

 - A bond issued to one party of a contract as a guarantee  against the failure of the other party to meet obligations specifie in the contract . 

Purpose - Performance bond are used by owners who are not sure that they can fully trust their contract , and want a safety net that will pay them back if the project goes wrong with a performance bond , owners can specify exactly what kind of work they want done and hold the contract to it . Government agencies and larger coperation require performance bonds for this reasons . 

Exercise 3

a) Based on PAM 2006 Form of the Building Contract , discuss whether the Contractor is entitled to an Extension of Time and a Loss and ? or Expense claim in the followings situations :

i)The Contractor  was instructed to suspend his foundation works for two months due to a poor response to the newly launched housing project by the Developer .

A :  - In this case  , that was due to developer fault so the Extension of Time should be proven .
      - The two months was long time and mass feel of worker . sO THERE WAS CLIENT  , developer's fault that's why the claims must be proven .

ii ) The quantity of removal of roack unforeseenbly tripled that allowed in the provisional quantity , resulting in additional 30 days being spent on this activity .

A: Because the responsible was not at neither contractor or client , so it was suppose to give extension of time in the project .
  - The contractors riosk was including  the quantityu of removal rock , so it did not have any claims to the contractors .

iii ) The Architect was made to wait for confirmation of the revised external colour scheme by the EMployer for three weeks when the contractor is in the finishing stage of his works .

A : - Late confoirmation was given by the Client , Devloper fautly because of this contractor manage to get extension of time .
  - The late confirmation will cause a lot of loss to contractors  because that was developer fault , so contractor manage to get claims .

Iv ) A two - months duration was allowed for pilling the Contractor in his Master Works Programme . it took him two and half month to complete the piling work and he is claiming for two weeks extensions on the ground that the Architect had accepted and approved his work programme .

A :  Because the Architect are acce[ted amd a[[rpved tje extemsopm works so the extension  of time for the element was accepted .
   -  Submission of work programme does mean the contractors can relieve the complete the works , so the claims was not accepted .

v ) Just before the Hari Raya balik kampung rush , the Contractor without an Architect's Instruction complied with JKR;s urgent order to widen the adjoining road and lay new concrete kerbs to make it safer for road users . The contractor mobilizred half of his existing workforce to complete this addtional works in 5 days .

A:  The client was order to do the addittional work which was a variation of the project , so contractor manage to get extension of time .
  - The vatiation order has received directly for client , so the claims should accepted /

B ) Define the term Relevant Events' in the context of Extension of TIme under PAM 2006 Form of Building Contract and discuss any FOUR (4) of those " Relevant Events' stated in the Extension of TIme provision contained in Clause 23.8 .

Clause 23
 - 23.8 ( a )  Force Majeure  - It was act of god like tsunami , earthquake and volcano .
- 23.8 ( b ) Exceptionally in element wheather - The heavy rain at Johor and Kelantan .
-23.8 ( c )  Loss and / or damage occasioned by one or more of the contingencies referred to in clause 20.A , 20.B or 20.C as the case may be , provided always that the same is not due to any negligence , omission , default and / or beach of contract by the Contractor and / or Nominated sub- Contractors

 - The developer got addiction work , variation to the project .

-23.8 (a) Civil commation , strikje or lockout affecting any of the trades employed upon the works or any of the trades engaged oin the preparation , manufacture or transportation  of any materials and goods required for the works .
- The rte of transportation material or price of the material .

2d

The liquidated acertained Damages only valid or the Contractor only has required to pay for Liquidated Ascertained Damages when the Client or Architect has issued certificate of non - completion

2d

The liquidated acertained Damages only valid or the Contractor only has required to pay for Liquidated Ascertained Damages when the Client or Architect has issued certificate of non - completion

Building act and contract

If the certificate of Non-Completion has been issued on 30th December 2008 and the Extension of TIme was not approved , the Contractor only finished theoir work on 15th January 2009  . How much Liquidated Ascertained Damanges that Contractor has to pay to the client ?

15 days x RM 2,250.00 = RM 33,750.00


C) Based on the Table Q6 what is the total amount of variation works ?
 
  Total variation works  = adjusted sums - contract sum

= RM 5,900 , 000.00 - RM 5,000,00.00
=RM 900 ,000 .00

Sources

• Natural 
• ( crushed rocks , sand and gravel ) 
• From river beds , quarries , sea-beds , cooled volcanos 
• Artificial ( man - made ) 
• - Broken bricks , blast furnace slag 

Agggregates

• Minerals filler materials 
• Collection of small particles 
• 60-70 percent of concrete are aggregates ( 3/4 volume ) 
• Cheap : - economical to have more aggregates in concrete 
•  High volume of stability 
• Reduce the heat of hydration of concrete 
• Better durability 
• Classified under 2 categoris 
• Coarse aggregates - pass through 75mm mesh sieve and are entirely retained on 4.75mm ( 3/16 in ) 
• Aggregates greater than 75mm known as cyclopean aggregates 
• Fine aggreates ( sand ) - size smaller than 4.75mm but completely retained on 0.07mm mesh . 
• Silt - 0.06 -0.02 mm 
• Clay - smaller than 0.02mm 

Water repellers

• Decrease permeability 
• Prevent absorption of rain water 

Bonding agents

• Increase bond strength between new and old concrete surface ( sometime cement - paste slurry is been used ) 
• Use for patching and remedial work 
• Adverse effect : some reduction in compressive strength . 

Bonding agents

• Increase bond strength between new and old concrete surface ( sometimes cement - paste slurry is been used ) 
• Use for patching and remedial work 
• Adverse effect : some reduction in compressive strength 

Superplasticisers

• Some as water reducer : - but more effective 
• Disperse by coating cement particles thus separating and dispersing the cement in the water phase . 
• Use to facilitate placing e.g pump mix ( high workability ) , give early and extremely high strength and durability ( reduction of w/c ratio ) 
• Adverse effect : Increase bleeding and segregation tendency , increase shrinkage 

Water reducer

• Increase workability or slump ( if w/c remain ) , strength ( reduce water ) ; 
• Reduce cement and water content ( given same workability and strength ) 
• Use to facilitate placing or to give higher strength and durability . 
• Adverse effect : - increase drying shringkage , some types may increase bleeding and retard the setting time . 

Retarder

• Delay onset of setting and hardening i.e extending the time between initial mixing and final compaction 
• Use in hot weather where large concrete pour 
• Frequently used in ready - mixed concrte 
• Uses influenced by aggregates type and grading 
• Do not adversely affect 28 days strength 
• Adverse effect : increase bleeding with some type , increase drying shrinkage , reduction of early - strength development 

Accelerator 2

• calcium chloride ( most common ) , calcium formate 
• Increase rate of setting and hardening 
• High heat evolution 
• Use in winter and rapid removal of formwork 
• Adverse effect : increase drying shrinkage reduce resistance to sulphate attack   , >2% calcium chloride > corrosion of rebar 

Accelerators

• Should be chloride - free eg .  Calcium formate to avoid metallic corrosion and reduction in concrete strength . 
• Affect setting only 
• Use for emergency repair work ( stop pressure leaks ) . 

Air - Entrainer

• Formation of small srtable discrete bubbles 
• Improved workability ( higher slump ) 
• Increase resistance to frost action 
•  Reduction in bleeding and water gain 
• Use for road and runway construction 
• Adverse effect : some reducrtion in strength 
• The incorporation of void space within concrete decreases its crushing strength by 6% for every 1 % of air-entrained > However , itg is partially offset by using lower water content 

Types of admixture

• Air - entrainers 
•  Accelerators 
• Retarders 
• Water reducers 
• Superplasticisers 
• Bonding agents 
• Water repellers 

Admixtures

- Hydration
- Liberation
- Formation of pores
- Development of gel
  to achieve      workable , finishable , strong , durable and watertight concrete .

Admixture vs additive

• Admixture 

- SUbstqnces ( other than cement , water aggregates or rebar ) aded during or immediately before mixing to improve / alter the properties of concrete ( eg. accelerators ) 

Note : Doses are usually very small ( < 1 % ) 

   - Effect very sensitive tovariation in dose 

   - Side effect 

Additive 

 - Substance added by cement manufacturers to modify properties of cement ( eg. gypsum ) . 

Water use

Maximum permitt concentration of various harmful elements as suggested by I.S.I

• Organic solid  0.02 %
• Inorganic solid  0.30% 
• Sulphates 0.05%
• Alkali chlorides   0.1%  

Admixtures 

• Other than using special cement , admixture can be used to change certain properties in concrete more effectively 
• TO reduce cost of concrete construction 
•  To ensure quality of concrete during mixing , transporting , placing , and curing in adverse weather conditions 
• To overcome certain emergencies during concreting operations . 

Seawater

Does not have adverse effect on the strength and durability of concrete but will cause

• Surface dampness 
• Efflorescence 
• Staining 
• Risk of corrosion of steel 
• More rapid and early strength gain but 28-days strength will be lower i.e. 10-20 % ( can be compensated for by using a lower w/c ratio ) . 

Why use clean water ?

• Impurities in water ( large quantity of suspended solids , excessive amount of dissolved solids or salts , or appreciable amount of organic materials ) will 

•  Affect setting 
• Affect strength 
•  Cause staining on concrete surface 
• Cause corrosion of reinforcement 
• Drying shrinkage 
• Efflorescence 
• Acidic water affect setting and hardening of concrete  , alkaline water > quick setting and low strengths . 

Water ( FUnction )

• Chemical reaction with cement and thuis causing it to set and harden 
• Lubricate the aggregates in concrete 
• Mixing , placing and compacting concrete 
• Washing aggregates 
• Curing 
• 
  

VEBE test

• Test for low workability / drier mix 
• Slump test is carried out in cyclinder 
• Lowered glass plate to surface of slump 
• Switched on vibrating table 
• Record time taken ( in second ) for remoulding ( for concrete slump to take the shape of cylinder - when lower surface of the glass plate is fully covered with cement grout ) . 

Compacting factor test

• Test for drier concrete mix 
• compacting factor = weight of partially compactedc concrete / weight of fully compacted concrete . 

Tests of workability

• Do not measure individuals characteristic ( consistency , mobility and compactability ) 
• Provide useful and practical guide on workability of mix 
• Workability affect cost - unworkable concrete mix require more labour and time for full compaction . 
• Workability test must be completed within 15 minutes 
• Sampling : Taken after 0.3m cube of the initial discharge of freash concrete . 

Bleeding

• Upward movement of water after concete have been consolidated , but before it has set . 
• Reduce by : 

1. Increasing cement fineness or using pozzolans or other finely divided mineral ad mixtures 
2. Increasing the rate of hydration of cement ( eg. use high - alkalis contents ) 
3. Through air entrainment 
4. Reducing the water content 

Segregation

• A separation of components ( e.g. aggregates ) or fresh concrete , resuklting in a non-uniform mix 
• Contributed by : 

1.  Larger maximum particle size ( over 25mm ) and proportion of large particles 
2. A high specific gravity of the coarse aggregate to compared to that of the fine aggregates 
3. Changes in the particle shape way from smooth , well -rounded particles to odd shaped , rough particles 
4. Mixes that are too wet or dry 
5. Concrete allow to fall from greater high / 

• Can be avoid by 

- Addition of little air entraining agent 

All the operations like handling , placing and consolidation should be conducted carefully. Concrete should not allowed to fall from greater heights . 

- Concrete mix should be properly designed and should not be added with water more than the desired amount . 

Temperature

• High temperature reduces workability and increase slump loss ( refer to time ) 

Time

• Freshly mixed concrete stiffen with time slump loss 
• Water absorbed by aggregates , some lost by evaporation ( due to sun or wind ) and some removed by initial chemical reaction . 

Fineness of cement

• The finer the cement , more water is required 
• THe finer the cement , the lower workability 
•  Much less important in determing workability than are the aggregate properties . 

Admixture

• Such as water - reduces or plasticisers improve workability 
• Used for 3 purposes : 

1.  To achieve higher strength by decreasing w/c ratio at the same worability as an admixture - free mix 
2. To avhieve the same workability the decreasing cement content to reduce heat of hydration in mass concrete . 
3. To increase workability to ease placing in inaccessible location . 

Aggregates types and grading

• A well graded aggregates with the largest particle size which will pass readily between around the reinforcement improves workability . 
• Irregular and angular shape with rough texture require more warter , therefore less workable then rounded aggregate . 
• Workability of concrete is mainly influenced by the total surface area of the aggregates . Workability decreases as the specific surface area increase . 
• 
  

water content

• Water lubricates the content of mix 
•  Higher w/c ratio , workability increase 
• However , too much water may result in high porosity , less strength 

water / cement ratio  = mass of water in a concrete sample / mass of cement in sample  

Factors affecting workability

• Water content 
• Properties of aggregates 
• Concrete mix 
• Properties of cement 
• The presence of admixture 
• Fineness of cement 
• Time 
• Temperature 

Strength and density

• Strength and concrete is affected by voids in compacted concrete . 
• Important to achieve full compaction in order to achieve high strength 
• Sufficient workability is important achieve full compaction ( eliminate air voids , therefore improve density , achieve higher strength ) . 

Compactability

• The ease with which a given mix can be fully compacted , all ( most of ) the trapped air being removed 

Mobility

• The ease which the mix can flow into and completely fill the formwork or mould 

Consistency

• Describe the state of fresh concrete 
• Measure of wetness or fludity 
• Wet concrete are more workable than dry concrete 

What is workability

• The ease with which a concrete mix can be handled from mixer to its compacted shape 
• The amo unt of mechanical work , or energy , required to produce full compaction of concrete without segregation . 
• 3 main characteristics 

1.  Consistency 
2. Mobility 
3. Compactability

Recycled concrete

• When used as a source of aggregfate for concrete , crushed concrete has in general lower strength and high water absorption characteristic than porimary aggregates . 
• This makes mix design more difficult 
• The proportion of cement paste in recycled concrete is much larger than in the original material , shrinkage and creep will be increase . 
• Too many recycled fines can produce a harsh and unworkable mixture 
• In crushing the concrete , it is difficult to control particle size distribution , meaning that the " aggregate " may fail to meet grading requirements . 
• The largest problems for  reuse as concrete is that large variations in quality can be expected . 
• The use of construction waste should focus upon non-structural applications and those without demanding exposure requirements . 

After removal of contaiminants through selective demolition , screening and / or air separation and size reduction in a crusher to aggregates sizes , crushed concrete can be used as : 

- new concrete for pavements , shoulders , median barriers , sidewalks , curbs and gutters and bridge foundations 

- Structural grade concrete ( technology developing and not widely used at the moment ) 

-Soil - cement pavements bases 

-Lean - concrete or econo-crete bases and 

- Bituminous concrete . 

Recycled concrete used as aggregates / crusher run to provide an leveled surface for road pavements . 

Main factor affecting the recycling are

1.  The physical form of concrete can make handling and recycling difficult , especially if reinfoced . 
2. Recycling concrete containing steel involve breaking up in-situ frames and then reducing columns and beams to more manageable size by large scissor action machines which cut through the concrete and steel . 
3. Pure crushed concrete is normally contaiminated by brick and other waste which may not be acceptable for some application 
4. Stock piling facilities are required  , demand for the recyucles must be rouggly matches to supply of concrete waste ( location , time preference , road assess ) . 

Finishing

• Screeding 

- Process involves striking of the excess concrete to bring the top surface to propert grade 

• Flotingh 

- Irregularities left on the surface after screeding operation are removed by floating operation 

-Any spots noticed are filled with extra concrete and work with float 

• Trowelling 

- Final operation of finishing 

-Operation is done after all the excess water from the surface has evaporated
For large works , power trowels may be used 

Vibrating tables

• Mouods are placed on the tables for vibration , widely used in precast concrete . 

Surface vibrators

• Effective only for depth about 20cm 
• Flat horizontal plate suitable for large surface eg, dam , pavements 

External formwork vibrators

• Necessary when reinforcement does not allow space for internal vibrators 
• Must be firmly fixed to formwork to produce shaking motion 
• Formwork must be rigit to transmit vibration without being damaged . 

Types of vibrators

• Internal vibrators or poker vibrators 

1.  High efficiency 
2. Has direct contact with concrete 
3. Should not be placed too close to formwork or reinforcement  in order to obtain uniform appearance and not to spoil the form 
4. To be inserted vertically 
5. Avoid under vibration 
6. Should avoid over vibration to prevent segregation 

Method of compaction

• Hand compaction   

Roding , tamping or spade 

Can be used easily for mix which has sufficient workability 

• Compaction by machine 

By using vibrators 

Needs for compaction

• Consolidation of plastic concrete 
• Remove air voids to achive maximum density 
• Trapped air should not exceed 2 % when concrete is placed 
• 1 % of entraped air cause a loss of about 5% strength 
• To ensure good contact between materials and reinforcing bars in RC 

Placing of concrete 2

Concrete mix 1:2:3

Means the ratio of 1 part cement , 2 parts fine aggregates and 3 parts coarse aggregaes ( 3 commonly measured by weight but during mixing commonly by volume .

Precautions

• Concreting should be continuously to avoid irregular and unsightly 
•  Formwork should be oiled before concreting 
• While placing the concrete , the position of formwork and reinforcement should not be disturbed 
• Concrete should not be dropped from height > 1m
• Avoid raining day 
• Thickness of concrete should not more than 30-45 cm for mass concrete and 15-30 cm for RC stuctures 
• Avoid walking on freshly concrete laid . 
• Concrete should be placed as near to its final position . 

PLACING OF CONCRETE

•   Cooncrete should be placed and compacted before its setting starts 
• Methods used should be prevented from segregation 
• Before concreting , formworks shoulds thoroughly be checked for its stiffeners , required dimension s , and cleanliness 
• Surface of formwork should be soaked with water .