honeycomb rectification work

PROPOSED DEVELOPMENT OF NEW KLIA2 TERMINAL AND ASSOCIATED WORKS AT KL INTERNATIONAL AIRPORT, SEPANG,SELANGOR

REPORT FOR HONEYCOMB RECTIFICATION WORKS AT

LIFTCORE AREA (INITIAL CASTING)

AUTHORIZATION AND RECORD

Rev Description PreparedBy

ReviewedBy

ApprovedBy

Date

0 Report for Honeycomb Rectification Work at Tower Liftcore Wall (Initial Casting)

CONTENTS

Revision: 0 Page No: 1 of 8




1 Introduction..................................................................................................................32 Area of Rectification.....................................................................................................33 Root Cause and Proposed Rectification Method............................................................34 Method Statement.......................................................................................................35 Material.......................................................................................................................46 Machinery/Equipment..................................................................................................47 Man Power...................................................................................................................48 Safety & Environment...................................................................................................59 Pre and Post Rectification Works..................................................................................6





11 IntroductionIntroduction

Reinforced concrete is a one of the most commonly used construction materials. It is a combination of concrete (cement and aggregates) and reinforcing steel. In order to have a reinforced concrete beam, column, slab or wall function properly, the concrete must be properly consolidated in the forms, i.e. it must completely encapsulate the reinforcement and be free of voids or "honeycombs". Voids are completely empty or hollow spaces in the form in which no concrete exists.

Honeycombs based on a Portland Cement Association definition, are voids left in concrete due to failure of the cement mortar to effectively fill all the spaces between the coarse aggregate particles. Severe honeycombs (sometimes known as rock pockets) occur when an excessive amount of aggregate is found without the presence of cement paste. (See Figure 1)

Figure 1: Honeycomb on an initial casting liftcore wall from excessive lift depth

22 Area of Rectification Area of Rectification

This rectification work covers the honeycombs defect for initial casting of liftcore wall.

33 Root Cause and Proposed Rectification MethodRoot Cause and Proposed Rectification Method





Generally there are some causes that cause of voids or honeycombs in reinforced concrete. For this scenario, three factors were identified;

1. Pouring Lift Depth - When single concrete placements or "lifts" are too deep, proper vibration can become very difficult or impossible. Excessive lift depths can also allow too much free-fall of the concrete that can create a separation of the cement mortar and aggregate as the aggregate impacts the reinforcing steel when falling through the forms.

2. Form Leaks - Leaks in the formwork can allow the cement paste to escape out of the form leaving behind only unbonded aggregate and rock pockets. Generally it’s occur on the joints area between formworks itself and between formwork and newly casted concrete.

3. Rebar Congestion - if rebar is placed too close together or too close to formwork it will trap the larger pieces of aggregate while the mortar in the mixture may or may not pass through. Other causes related to rebar congestion include excessive reinforcement splices that prevent the concrete from properly filling the forms.

4. Inadequate Vibration -. Improper vibration can be related to:o Too small or large a vibrator for the size of the pour and mix designo Too short or long an insertion time of the vibrator in the concrete in a

single locationo Too wide of a spacing between each insertion of the vibratoro Lift depths too deep to actually vibrate the concreteo Congested reinforcing that will not allow a standard vibrator to reach all

areas required

After a joint inspection with Consultant personnel on the honeycomb was obtained, the contractor was proposed a pressure grouting method based on the honeycombs scenario presence.

44 Method StatementMethod Statement

This method statement shall as follow:





1. Identify the loose concrete, voids and honeycombs area of the defective areas. (See appendix A, figure 1)

2. The affected defective areas is cleaned, hammered or chiselled to remove all the loose concrete and small particles such as sand.

3. Hack of all the loose concrete until sound solid concrete is reached (See appendix A, figure 2)

4. All the concrete dust that left over is the washed away with water or blown away using compressed air. This is to ensure a good bonding between the concrete and the repair material.

5. Ensure that the surface is free from oil, grease or any loose materials6. Obtain the inspection and approval from Consultant personnel after the hacking work is

done.7. Re-erect the formwork and seal up all the gaps with cement mortar to avoid any leaking

during the repairing work is carried out. (See appendix A, figure 3)8. Non shrink grout material is then mixed according to the manufacture’s instruction. (See

appendix A, figure 4)9. Pump the non shrink grout material into the defective area using pressure grout method.

(See appendix A, figure 5)10. Striking the formwork and chisel off the redundant grout/concrete11. Obtain the inspection and approval from Consultant personnel of the rectified work prior

to subsequent finishes on the defective areas.(See appendix A, figure 6)

55 MaterialMaterial

The Non shrink grout material use for this rectification work as follow:- Conbextra GP (See figure 2)

Figure 2: Conbextra GP

66 Machinery/EquipmentMachinery/Equipment - Bucket - Conbextra GP





- Electrical Breaker ,- Plain Water- Trowel - Plywood

77 Man PowerMan Power - Supervisor ( 1 person)- Worker ( 2 person)

88 Safety & EnvironmentSafety & Environment

It is our policy to perform all our works with due regard to safety, practise safe working methods and create a risk free, healthy working environment.

The following key areas construction shall be adhered by all site personal, working on-site. There are not an all inclusive set of rules, but a guidance of the level of care and attention on safety matters, that every site personnel shall observed and follow.

Personnel Protective EquipmentThe personnel protective equipment which will be provided to the workers on-site includes the following:- Safety helmets (hard hat)- Safety vest, for workers - Rain coat, when required to work in the rain

In summation, in order to achieve safe, free risk and healthy working environment, including loss prevention, every practicable step must be taken by each and everyone engaged in this project site.

99 Pre and Post Rectification worksPre and Post Rectification works

Refer to Appendix A


APPENDIX AAPPENDIX A

Figure 1: Voids and honeycombs of the defective areas.

Figure 2: All loose concrete were hacked until sound solid concrete reached.

Figure 3: Formwork erected and all the gaps were seal up with cement mortar.

APPENDIX AAPPENDIX A


Figure 4: Non shrink grout material mixed according to the manufacture’s instruction

Figure 5: Non shrink grout material pumped into the defective area using pressure grout method

Figure 6: Rectified defective honeycomb/void


honeycomb rectification work

Documents

honeycomb rectification

area of rectification

initial casting liftcore

proposed rectification

associated works

post rectification

combination of concrete

selangor report