Bps 5205 sustainability construction and maintainability velpandi & maria

1

BPS 5205 :SUSTAINABILITY CONSTRUCTION & MAINTAINABILITY

Lecturer: Prof Michael Chew Yet Lin

CASE STUDY: Construction Defects Analysis on site, Remedial Measure

and Preventable Practices Water way Banks HDB at Punggol East

Submitted by:

MARIA ARCHANA - A0112327U

VELPANDI PARISITHU - A0112331A

2

CONTENTS

1. INTRODUCTION 3

1.1. Abstract

1.2. Objectives

3

3

2. CASE STUDY: WATERWAY BANKS, SINGAPORE 4

2.1. Introduction of the Case Study

2.2. Eco-Friendly Features

4

5

3. CASE STUDY OF SLAB PLANK CRACK IN CONSTRUCTION SITE 5

3.1. Precast Plank Crack Defect Photos

3.2. Suspected causes of Defects

3.2.1. Quality of precast plank in precast plant

3.2.2. Concrete quality and testing methods in precast plant

3.2.3. Form work support design for slab (Bracing) in construction site

3.3. Reason for the precast plank crack

3.4. Remedial Procedure for Plank Rectification

3.4.1. Standard method of statement for Repair of Crack line on Pre stresses

plank

3.4.2. Characteristics Of Stop Ox IH BV

3.5. Preventable Practices for pre stressed Planks

6

7

7

11

15

19

20

21

22

25

4. PRECAST WALL CRACK DEFECTS 26

4.1. Precast Wall Crack Defect Photos

4.2. Reason for the Precast Plank Crack

4.3. Remedial Procedure for Precast Wall Crack Rectification

4.3.1. Characteristics of Stopox SK 21S

4.3.2. Standard Method of Statement for Repair of Crack Line on Precast

Wall Component

4.3.3. Preventable Practice for Precast Wall

4.3.4. Preventable Practice for Precast Wall Storage

5. FAILURE TO LAY WATERPROOFING STRIP DURING ERECTION OF

PRECAST WINDOW FACADE

5.1 .Re-erected Window Façade As Per Standard Drawing

5.2.Usable Material Details For installation Of Precast facade

5.3.Preventable Practice for Precast Window Wall

26

28

29

30

32

34

35

36

37

40

40

6 . CONCLUSION 41

6.1.Reference 42

3

1.INTRODUCTION

1.1. Abstract:

Singapore heavily relies on conventional precast construction involving extensive use of

precast planks, canopy beams, column & facade. The recent prefabrication trend, which is

being increasingly used in the building industry, alleviating some of the environmental

burdens associated with conventional construction. Several case studies were conducted

on residential buildings in Singapore.

The findings revealed that environmental, economic and social benefits of using

prefabrication were significant when compared to conventional construction methods. This

implies that a wider use of prefabrication techniques could contribute to sustainable

construction in a dense urban environment on the other hand using precast components

have adverse effects on the structure. Today, as much as 82% of Singaporeans live in

public housing delivered by the HDB.HDB plans and develops public housing towns that

provide Singaporeans with quality homes and living environments.

In the construction industry, construction defects and failures can occur during the design

and construction phases of a project, or after a structure is substantially complete.

However, while a design professional is responsible to produce complete, accurate and

well-coordinated design and construction documents that are substantially free of defects;

and a contractor is required to adhere to the design and construction documents, nothing

built is ever perfect nor does the law require a perfect design. Furthermore, all buildings

have an expected lifespan and even the structures of the ancient world will erode into a

mound of sand given enough time. The eventual failure of a structure is an expected result

rather than a manifestation of a construction defect. The question becomes what is a

construction defect; how do defects arise; and how can defects be identified and

managed?

A Case Study has been conducted to analyse Construction Defects on site, Remedial

Measures & Preventable Practices at HDB Water Way Banks at Punggol East.

1.2. Objectives:

The objective of this case study aims to mitigate the defects to the future HDB projects.

This project may help to HDB engineers for awareness regarding defects prevention

practice. HDB has objectives, which expanding from time to time, Recently, HDB is not

only functioning as a provider of basic shelter but also creates housing that can comply

with the needs, necessities and aspirations for modern living days and futures. HDB

objective is to provide affordable quality homes and develop vibrant living environment.

This case study has the following objectives of: To investigate and identify the defects that appeared in the precast slab planks.

To identify the defects during construction progress, remedial measures &

preventable practices propose better & quality living standards to the public.

4

2. CASE STUDY: SITE AT WATERWAY BANKS, SINGAPORE

2.1. Introduction of the Case Study:

Waterway banks, located at a gentle bend of the waterway and housing an exciting array

of commercial and recreational facilities in punggol with total site area 35,998sqm

(Residential), 7001sqm (Common Green).9 Blocks of 8/15, 13/18, 16 and 17 storey high

Residential blocks, 1 MSCP with Visual Green Roof, 2 ESS, Commercial, Childcare

Centre, Future Community Facilities, 2 Precinct Pavilions, Common Green.

Total No of Dwelling Units 1016, Contract Award Date 25 November 2011, Contract Period

16 December 2011 to 15 June 2014, Contract Sum: $133,999,000.

Figure 2.1.1. Exterior and interior views of River way banks project

Client

Housing Development Board

Consultants

Architect ADDP Architects LLP

Structural Engineer KTP Consultants Pte Ltd

M&E Engineer United Project Consultants Pte Ltd

Quantity Surveyor Langdon & Seah Singapore Pte Ltd

Landscape Architect Martin Lee Designs

Contractor

Sunhuan Construction Pte Ltd

Figure 2.1.2. Development Data

5

2.2. Eco-Friendly Features:

Use of Sustainable and recycled products

Separate refuse chutes provided for recyclable wastes at each residential block

Motion sensor lights installed at common staircases to reduce energy consumption

Rainwater harvesting system provided at each residential block to store rainwater for washing of common areas

Bios wales designed in the landscape to help maintain the quality of surface run-off from rainwater prior to discharge into drainage system

Bicycle stands provision to encourage use of these environmentally friendly forms of transport

Obtained Green Mark Gold Plus Award

Figure 2.2.1. Location map

Figure 2.2.2. Site layout

3. CASE STUDY OF SLAB PLANK CRACK IN CONSTRUCTION SITE

CASE1:Slab crack has been identified with water seepage during Quality Checking

Procedure followed after identification of defect:

Investigation to identify the reason for the defects

Confirmation of standard HDB construction Procedure deviation for the defect

Concrete Quality Checking at precast plant

Reason identified : Failure to follow the 'Scaffold installation procedure at

construction site'

Remedial procedure for defect rectification

Preventable practices for precast slab crack

6

3.1. Precast Plank Crack Defect Photos:

Figure 3.1.1. water seepage in the plank crack

Figure 3.1.2. Water seepage in the plank crack

Water seepage

Water seepage

7

3.2. Suspected Causes Of Defects:

Quality of precast plank in precast plant.

Concrete quality and testing methods in precast plant.

Form work support for slab (Bracing) in construction site.

3.2.1. Quality of precast plank in precast plant:

a. Formwork:

Figure 3.2.1.1. Initial Process Bay No. : 1 & 2 Components Name: Slab Plank

All the cement debris and concrete chips are removed from the plank sheet and formwork oil should be applied neatly.

8

b. Pre tension cable:

Figure 3.2.1.2. Pre tension Process Bay No. : 1 & 2 Components Name: Slab Plank

The pre tensioned cables are pulled by hydraulic equipment according to the design.

1

2

3 4 5

9

c. Reinforcement:

Figure 3.2.1.3. Reinforcement Process Bay No. : 1 & 2 Components Name: Slab Plank

After the cables are pre tensioned, reinforcement is provided according to the drawing.

1

2

3 4

5

10

d. Delivery progress:

Figure 3.2.1.4. Delivery Process Bay No. : 1 & 2 Components Name: Slab Plank

After casting, the slab planks are transported to the relevant projects.

11

3.2.2. Concrete quality and testing methods in precast plant:

Figure 3.2.2.1. Slump cone test method for concrete quality check

After ending undisturbed period, put down casting date and item name on the top of

concrete specimen with permanent marker. After 8 to 10 hours of casting, wrap the cube

mould with wetted hessian cloth. Cover the mould's top portion with a polythene sheet so

that water doesn't fall on concrete surface.

Uncover and remove the cube specimens from mould after 24±½ hours of casting. For

removing specimen from mould, first loosen all nut-bolts and carefully remove specimen

because concrete is still weak and can be broken.

Immediately after removing, put the specimen into a tank of clean water for curing. Make

sure cube specimen is fully submerged in water. After 28 days of curing take out

specimens from water tank and send to laboratory for testing.

12

Generally three cube specimens are tested separately at laboratory and the average result

is counted as concrete compressive-strength. So we make three specimens on site at a

time.

Standard Procedure of Concrete Compression Test:

Step1 - Preparation: Check all the things you need are ready. Check concrete

compression machine is in working order.

Step2 - Safety: Wear hand gloves and safety goggles.

Step3 - Taking measurement: Take the measurement of concrete specimens (which are

sent to laboratory for testing). Calculate the cross sectional area (unit should be on mm2)

and put down on paper. Do the same for each specimen.

Step4 - Start machine: Turn on the machine. Place one concrete specimen in the centre of

loading area.

Step5 - Lowering piston: Lower the piston against the top of concrete specimen by pushing

the lever. Don't apply load just now. Just place the piston on top of concrete specimen so

that it's touching that.

Step6 - Applying load: Now the piston is on top of specimen. It is the time to apply load.

Pull the lever into holding position. Start the compression test by Pressing the zero button

on the display board.

Step7 - Increasing pressure: By turning pressure increasing valve counter-clockwise,

adjust the pressure on piston so that it matches concrete compression strength value.

Apply the load gradually without shock.

Step8 - Test is complete: Observe the concrete specimen. When it begins to break stop

applying load.

Step9 - recording: Record the ultimate load on paper displaying on machine's display

screen.

Step10 - Clean the machine: When the piston is back into its position, clean the creaked

concrete from the machine.

13

Step11 - Turning off machine: Match your record once again with the result on display

screen. The result should still be on display screen. And then turn off the machine.

Step12 - Calculate concrete compressive strength: The result we got from testing machine

is the ultimate load to break the concrete specimen. The load unit is generally in lb. We

have to convert it in newton (N). Our purpose is, to know the concrete compressive

strength.

We know, compressive strength is equal to ultimate load divided by cross sectional area of

concrete specimen. We took the concrete specimen's measurement before starting the

testing and calculated cross sectional area.

Now we got the ultimate load. So we can now calculate the concrete compressive

strength.

Compressive strength = Ultimate load (N) / cross sectional area (mm2).

The unit of compressive strength will be N/mm2.

Normally 3 sample of concrete specimens are tested and average result is taken into

consideration. If any of the specimen compressive strength result varies by more than 15%

of average result, that result is rejected.

14

Concrete Mix Design Computation and Summary:

15

3.2.3. Form work support design for slab (Bracing) in construction site.

Figure 3.2.3.1 Scaffolding cross section drawings

16

Scaffolding Formwork Design & Calculation by Professional Engineer: <formwk ver2.6> Project: SUNHUAN MON. 27-AUG-2012 <c:\zh\formwk\FORM.DAT> Code of Practice: CP23: Code of Practice of Form Work CP7: Structural Use of Timber BS5950: Structural Use of Steelwork in Building BS6399: Design Loading for Buildings RC concrete density=24 kN/m3 Timber material: Strength Group-B: Standard—Grade to be used <t.1.00> Brief: — — — — — — — — — — — - — — — — — — - — — — — — — — — scaf.layou.type=01 (ref to FRONT VIEW/SIDE VIEW output drawing) one(l) row.scaf(l219 Wx 1700 D) under Beam <t.1.sb.pi> Steel tubes of scaffold under RC Slab (THK=175mm) — — — — — — — — — — — - — — — — — — - — — — — — — — — — — fl_ht=3600mm; slab.X.spc=1200mm; gap(slab->slab)=1200mm gap(slab—>beam)= 900mm; max_gap=l200mm ;max_gap/2= 600mm RC.slab. wt = 1.20m(wid)x l.20m(spc)x 0.l7m(dep)x24 kN/m3 = 6.05kN form.scaf.wt= 1.20m(wid)x l.20m(spc)x0.4kN/m2+3.4m/l.7mxO.16kN = O.90kN sub-total DL = 6.95kN Live.Load= l.20m(wid)x l.2Om(spc)x 1.5kN/m2 = 2.3kN (min. 243kN) service:DL+LL= 9.2kN & U1timate:l.4DL+l.6LL= 13.4kN steel pipe 48mmX2.3mmTHK slender=l700/l6=105,so pc=l1ON/mm2 Fc=36.3kN (BS5950) say 25 kN (manufactures' recommend) ultimate load 113.40 KN < 25 kN O.K. — — — — — — — — — — — - — — — — — — - — — — — — — — — — — <t.l.bm.pi> Tubes of scaffold under RC Beam 250x800mm(WxD) w/ slab.thk=175mm — — — — — — — — — — — - — — — — — — - — — — — — — — — — — fl.ht=3.60m;scaf.wid=l200mm;bm.X.spc= 900mm;gap(bm—>slab)=900mm RC.beam. wt = 0.l3m(wid)x 0.9Om(spc) x 0.80m(dep)x24 kN/m3 = 2.l6kN RC.slab. wt = O.93m(wid)x 0.90m(spc) x 0.17m(dep)x24 kN/m3 = 3.50kN form.scaf.wt= 1.05m(wid)x 0.90m(spc)xO.4kN/m2+2.8m/1.7m x0.16kN = 0.64kN sub—total DL = 6.30kN Live.Load= l.05m(wid)x O.9Om(spc)x l.5kN/m2= 2.3kN (min 243kn) service:DL+LL= B.60kN & Ultimate:1.4DL+l.6LL=12.50kN steel pipe 48mmX2.3mmTHK slender=1700/l6=l05,so pc=l10N/mm2 Fc=36.3kN (BS5950) say 25 kN (manufactures' recommend) ultimate load :l2.50 KN < 25 kN O.K. — — — — — — — — — — — - — — — — — — - — — — — — — — — — —

17

one(1) row.scaf(1219 Wx 1700 D) under Beam <t.1.bm.st> Stringer member under RC Beam 250x800mm(WxD) — — — — — — — — — — — - — — — — — — - — — — — — — — — — — fl.ht=3.60m;bm.X.spc=900mm;slab.thk=175mm;gap(bm—>slab)=900mm RC.beam. wt= 0.13m(wid)x 0.90m(spc) x 0.80m(dep)x24 = 2.16kN RC.slab. wt= O.93m(wid)x O.90m(spC) x 0.l7m(dep)x24 = 3.50kN formwork.wt= 1.05m(wid)x O.90m(spc) x O.4kN/m2 = 0.38kN sub—total DL = 6.03kN Live.Load(min2.3)= 1.05m(wid)x 0.9Om(spc)x 1.SkN/m2= 2.30kN service:DL+LL= 8.33kN Ultimate:P=1.4DL+1.6LL=12.13kN Steel RHS D: 100mm B: 50mm T= 3mm t= 3mm A= 8.6cm2 Ix=112.1cm4 Zx= 22.4cm3 bending moment M=12.1kN*O.9m/B: 1.4kNm bending stress =1.4kNm/ 22.4cm3= 60.8 N/mm2 < 260.0 N/mm2 O.K shear.stres=3/2*12.1kN/2/ 8.6cm2=10.5 N/mm2 < 110.00 N/mm2 0 K def=5/384* B.3kN*( 90cm)*3/21000kN/cm2/112.1cm4= 0.3 mm deflection = 0.3mm ( span/2679 ) < 3.3mm (span/270) O.K — — — — — — — — — — — - — — — — — — - — — — — — — — — — — <t.1.bm.rn> Runner member@c/c300mm @ RC.Beam 250x800mm(WxD) — — — — — — — — — — — - — — — — — — - — — — — — — — — — — f1.ht=3.60m;s1ab.thh=175mm;gap(bm—>slab)=900mm using 1000mm runner spc. to calculate the loading RC.beam. wt= 0.25m(wid)x 1.00m(spc) x O.80m(dep)x24 = 4.80kN RC.slab. wt= 0.95m(wid)x 1.00m(spc) x 0.17m(dep)x24 = 3.99kN formwork.wt= 1.20m(wid)x 1.00m(spc) x 0.4kN/m2 = O.48kN sub-total DL = 9.27kN Live.Load(min2.3)= 1.20m(wid)x l.0Om(spc)X 1.SkN/m2 = 2.3kN for runner spc 300mm of 1000mm (loading taken used spc) service:DL+LL= 3.47kN Ultimate:P=DL+LL= 3.47kN Timber Rectangle D: 100mm B: 50mm A= 50.0cm2 Ix=416.7cm4 Zx= 83.3cm3 bending moment M=3.5kN*1.2m/8: 0.5kNm bending stress =O.5kNm/ 83.3cm3= 6.2 N/mm2 < 10.8 N/mm2 O.K shear.stres=3/2*3.5kN/2/ 50.0cm2= 0.5 N/mm2 < 1.02 N/mm2 O.K def=5/384* 3.5kN*( 120cm)*3/117OkN/cm2/416.7cm4= 1.6 mm deflection = 1.6mm ( span/ 749 ) < 4.4mm (span/270) O.K — — — — — — — — — — — - — — — — — — - — — — — — — — — — — <t.l.sb.st> Stringer member under RC Slab l75mm(THK) — — — — — — — — — — — - — — — — — — - — — — — — — — — — —

18

fl.ht=3.60m;slab.X.spc=l200mm;gap(slab—>slab)=l200mm RC.s1ab. wt= 1.20m(wid)x l.20m(spc) X D.l7m(dep)x24 = 6.0kN formwork.wt= 1.20m(wid)x l.20m(spc) x 0.4kN/m2 = O.6kN sub—total DL = 6.6kN Live.Load(min2.3)= 1.2Om(wid)x 1.2Om(spc)x l.5kN/m2= 2.3kN service:DL+LL= 8.92kN Ultimate:P=1.4DL+1.6LL=l2.95kN Steel RHS D= 100mm B= 50mm T= 3mm t= 3mm A= B.6Cm2 IX=ll2.lCm4 ZX= 22.4Cm3 bending moment M=l3.0kN*1.2m/8= l.9kNm bending stress =l.9kNm/ 22.4cm3= 86.7 N/mm2 < 260.0 N/mm2 O.K shear.stres=3/2*l3.0kN/2/ B.6cm2=1l.2 N/mm2 < 110.00 N/mm2 O.K def=5/384* 8.9kN*( 120cm)A3/2l000kN/Cm2/1l2.lCm4= 0.9 mm deflection = 0.9mm ( span/1407 ) < 4.4mm (span/270) O.K — — — — — — — — — — — - — — — — — — - — — — — — — — — — — <t.1.sb.rn> Runner member @c/c300mm @ RC.slab 175(THK) — — — — — — — — — — — - — — — — — — - — — — — — — — — — — fl.ht=3.60m;gap(slab—>slab)=l200mm;eff.span=max(l200,l200)=l200mm using 1000mm runner spacing to calculate the loading RC.slab. wt= l.20m(wid)x l.00m(spC) X 0.l7m(dep)x24 = 5.0kN formwork.wt= 1.2Om(wid)x 1.00m(spc) x O.4kN/m2 = 0.5kN sub-total DL = 5.5kN Live.Load(min2.3)= l.2Om(wid)x l.00m(spc)x l.5kN/m2= 2.3kN service:DL+LL= 7.BkN & Ultimate:P=1.0DL+l.OLL= 7.8kN ( CPU for actual runner spacing=300mm of 1000mm (loading taken used spc) service:DL+LL= 2.35kN Ultimate:P=DL+LL= 2.35kN Timber Rectangle D= 100mm B= 50mm A: 50.0Cm2 IX=4l6.7Cm4 ZX= 83.3Cm3 bending moment M=2.3kN*1.2m/8= 0.4kNm bending stress =O.4kNm/ 83.3cm3= 4.2 N/mm2 < 10.8 N/mm2 O.K shear.stres=3/2*2.3kN/2/ 50.0cm2= 0.4 N/mm2 < 1.02 N/mm2 O.K def=5/384* 2.3kN*( 120cm)*3/l170kN/cm2/416.7cm4= 1.1 mm deflection = 1.1mm ( span/1108 ) < 4.4mm (span/270) O.K — — — — — — — — — — — - — — — — — — - — — — — — — — — — —

19

3.3. Reason for the Precast Plank Crack: Plank is supported at the localized points on the metal form during casting time. Failure to follow the Scaffolding design.

Figure 3.3.1. Plank is supported at the localized points on the metal form


Incorrect!!!!!!

Plank is supported at

localized points on the

metal form.

20


3.4. Remedial Procedure for Plank Rectification:

Figure 3.4.1, usable chemical for plank rectification

21

3.4.1. Standard method of Statement for Repair of Crack Line on Pre-stresses Plank:

1. Prepare surface by removing laitance, dust, paint, skim coat etc, along the crack

for a width of approximately 50mm.

2. Attach the injection nipple by applying a bead of Sto SK-21 epoxy crack sealer on the

back and then stick it at approximately 300mm c/c along the crack.

3. Seal the remaining parts of the cracks with Sto SK-21 epoxy crack sealer. It should be

applied in strips of approximately 50mm width and 2mm thickness along the length of

the crack.

4. Allow the sealer to cure for one day.

5. Pour both components in mixing ration of part A — 3 : Part B — 1. Mix it

thoroughly and pour into the injector.

6. Begin injection at the lowest nipper upward or from one end of the crack. Once

STOPOX IH BV has fully cured / hardened in 7 days, remove the injectors and

Sealer by grinding.

7. The grinded surface shall then be skimmed coat finish Enclosed.

22

3.4.2. Characteristics of Stopox IH BV:

24

Figure 3.4.2.1. Plank crack rectification photo

Figure 3.4.2.2. Plank crack rectification photo

25

3.5. Preventable Practices for Pre stressed Planks:

1. Production supervisor should ensure that he has the latest drawing by checking with

production engineer.

2. Clean the mould and ensure the surface of the mould must be clean, free from debris

or loose materials.

3. Apply mould oil.

4. Lay PC stand and carry out the initial stressing of 1000psi.

5. Place the fabricated wire mesh with lifting hooks on the mould and place the divider

between two panels.

6. Close the end formers.

7. Carry out final stressing to 3440psi and ensure the actual elongation length is 515mm

+/- within 5% of stressing length.

8. Check concrete slump and take cube samples.

9. Pour concrete into moulds and compact with vibrations.

10. Roughen the exposed top surface of the plank.

11. Concrete cube have to achieve the required strength before dismantling side formers.

12. Place bar code on the plank that indicates the panel marking, production date and

serial number.

13. Demould the plank once cube strength achieved 25N/mm2 and transfer to finishing

area.

14. After Demould, the slab planks are transported to the relevant projects

26

4. PRECAST WALL CRACK DEFECTS : CASE2:Precast Wall crack has been identified during Quality Checking Procedure followed after identification of defect:


Confirmation of standard HDB construction Procedural deviation

Concrete Quality Checking at Precast plant

Reason identified : Failure to follow the 'standard practice of storage methods of

precast walls at plant


Preventable practices for precast wall crack and precast wall storage as per

standard.

4.1. Precast Wall Crack Defect Photos:

Figure 4.1.1. Precast Wall Crack Defect Photos

27



28

4.2. Reason for the Precast Plank Crack: Improper storage of precast wall in precast plant. Poor Workmanship in precast plant.

29

4.3. Remedial Procedure for Precast Wall Crack Rectification:

Figure 4.3.1. Usable Chemical for Precast Wall Crack Rectification

Figure 4.2.1.Improper storage of precast wall in plant Bay No. : 12 Components Name: 1BW1X

Twisting between the two portions of the partitions is observed due to large no of partition walls stacking.

30

4.3.1. Characteristics of Stopox SK 21S:

32

4.3.2. Standard method of Statement for Repair of Crack Line on Precast wall component:

The proposed rectification method is as follow:

1. Prepare surface by removing laitance, dust, paint, skim coat etc.

2. Use a grinder to cut a V-groove along the crack line.

3. Mix ration for Part A: Part B = 2:1

4. Mix both components thoroughly using a scrapper until a fully homogeneous

compound (Mid-grey) is obtained.

5. Mixing time: approximately 5 mins.

6. Apply Sto pox SK21 as a paste with scrapper or trowel along the V-groove line.

7. Let it cure for 7 days.

8. Use a grinder to grind off the epoxy surface until level with concrete surface.

9. The grinded surface shall then be skimmed coat finish.

33

Figure 4.3.2.1, precast wall crack rectification photo


34


4.3.3. Preventable practice for precast wall:

1. Production supervisor should ensure that he has the latest drawing by checking

with production engineer.

2. Clean the mould and ensure the surface of the mould must be clean, free from

debris or loose materials.

3. Apply mould oil.

4. Place the fabricated wall reinforced cage on the mould.

5. Close the end and side formers.

6. Assemble and tighten side forms to position.

7. Install of lifting hooks.

8. Check concrete slump and take cube samples.

9. Pour concrete into moulds and compact with vibrations.

10. Roughen the surface contact with in-situ portion.

11. Concrete cube have to achieve the required strength before dismantling side

formers.

35

12. Place bar code on the panel that indicates the panel marking, production date and

serial number.

13. Demould the precast component once cube strength achieved 10N/mm2 and

transfer to finishing area.

14. Before setting the formwork sheet for beams and slab, the Unwanted Groove line

should be cut.

15. During the striping of formwork sheet, sub-contractor should be aware of the

finished surface. Some damages are caused due to formwork removing.

16. Before concreting, the gap between the formwork sheet in slab and beam should be

properly covered by plastic tape and sealant.

17. Before fixing the formwork sheet, cement stains, chips should be cleaned properly

and shuttering oil should be applied neatly.

4.3.4. Preventable practice for precast wall Storage:

1. All precast component stack at storage area should be placed on the firm ground

and supported at both ends by timber runners

2. Issue delivery checklist to loading foreman.

3. Precast components will be loaded into the trailer.

4. QC Engineer to inspect the components to be delivered for any damages or quality

of the components.

5. Any structural crack or damages should be rectified according to approved method

of statement

. 6. QC Engineer prepares the delivery order.

7. Precast components deliver to site.

36

5.FAILURE TO LAY WATERPROOFING STRIP DURING ERECTION OF PRECAST

WINDOW FAÇADE: CASE3:Defect has been identified without water proofing strips during precast facade erection Procedure followed after identification of defect:


Confirmation of standard HDB construction window facade erection as per standard

Reason identified : Failure to follow the standard procedure of waterproof laying in

precast window facade


Emphasize to follow the standard procedure for erection of window facade .

Figure 5.1, precast façade erected with out waterproofing strip

37

Figure 4.4.2, precast façade erected with out waterproofing strip

5.1. Re-Erected Window Facade As Per Standard drawing:

38

Figure 5.2.precast façade erection photo

Figure 5.3.precast façade erected with waterproofing strip

39

Figure 5.4. Mortar laying precast façade erection

Figure 5.5 .precast façade erection photo

40

5.2. Usable material details For Installation of Precast Facade:

S.NO

MATERIAL

SUPPLIED BY

1

Davco Grout

180 Davco

2

SK2000 membrane

Davco

3

Quicseal 203

Quicseal

B TOOL / EQUIPMENT 1 Mechanical mixer

5.3. Preventable Practice for Precast window Wall:

1. Mark out facade position and use shim plates to set installation level of facade. 2. Install Quicseal 203 compressible waterproofing strip on external side of kerb where

precast façade is to be positioned.

3. Mix Davco Grout 180 to achieve plastic consistency according to manufacturer’s

recommendation. Use mechanical mixer to mix for 3-5 minutes.

4. Lay grout on precast façade sitting position. The height of grout is to be higher than

level set by shim plates. Ensure that the amount of grout is sufficient to prevent hollowness

of horizontal gap.

5. If required, cut SK2000 membrane to correct size and shape and paste the membrane

at the correct Location during installation.

6. Install precast façade and brace it immediately to support the facade. Adjust the

verticality and alignment of the façade.

7 Clean away excess grout that oozes out from the bottom of the façade.

41

6. Conclusion:

Workmanship generally refers to the quality of work evident in a particular object. There

are many dimensions, depending on an object's purpose, that contribute to the general

notion of the "quality of work" of an object.

However there is a six step process for managing construction defects.

Those six steps are as follows: » Awareness » Investigation » Discovery » Evaluation »

Treatment or remedy » Financial Recovery

This process can be termed as the life cycle of the investigation and resolution of a

construction defect issue.

It is evident that all of the parties involved in a design and construction project need to

minimize and prevent the incidence of design errors or omissions and/or defective

construction. In many cases, the practical utility of an object is of the foremost importance,

and workmanship is judged almost entirely based on how well the object serves its

intended function. In other cases, artistry is at least as important as, if not more important

than, practical utility. "Workmanship," then, cannot be considered a completely objective

measure, as it depends heavily on the needs of the individual who is to use the object.

On the other hand, lack of standby supervision also leads to defects in the quality of

precast components.

Workers negligence and failure to follow the working procedure ends up in defects.

Construction defects claims can be minimized, or even eliminated from your life's

experiences, by performing due diligence when we are engaged in the process of

construction.

Due Diligence, or Reasonable Diligence should be given attention to the matter at hand. It

is the diligence which is required by the circumstances, and the rendering of that which

prevents liability for negligence.

42

6.1 References:

1. Sources of information for Standard procedures, design procedures & investigation

places- Confidential

2. General references from BCA & HDB websites.

Bps 5205 sustainability construction and maintainability velpandi & maria

Design

Transcript of Bps 5205 sustainability construction and maintainability velpandi & maria