Here is the “Method Statement for Raft Slab Concrete Pouring.’ You as an engineer should study this so that you are able to execute the proper method or procedure when it comes to raft slab concrete pouring or raft slab construction.
Table of Contents
1. Title
2. Scope of Work
2.1 General Description
2.2 Equipment/Tools
2.3 Materials/Reference
2.4 Site Planning and Preparation
2.5 Work Methodology
2.6 Safety
2.7 Organization, Responsibilities, and Supervision
2.8 Workforce
3. Environmental, Safety and Health
3.1 Risk Assessment
4. Quality Assurance
4.1 Quality Requirements Table
5. Appendices and Reference
6. Briefing Sheet
7. Review Checklist
1. Title
Method Statement for Raft Slab Concrete Pouring
2. Scope of Work
2.1 General Description
The purpose of this method statement for raft slab concrete pouring is to describe the measures and ways of completing concrete pour works for raft foundation on this Project. The work shall include working area preparation, precautionary measures, application, finishing, inspection & testing.
2.2 Equipment/Tools
A. Heavy Equipment
Truck Mixers
Concrete Pump
JCB/Bobcat
B. Activity Equipment
Concrete Vibrator
Survey instrument
Power float machine
Metal tape
Wheel borrow
Shovel
Hammer/rubber hammer
2.3 Materials/Reference
2.3.1 Materials
Concrete: Grade 45/20
2.3.2 Reference
Specification
Drawing (See QA/QC table below)
2.4 Site Planning and Preparation
2.4.1 Material Delivery
The fresh concrete shall be delivered to the site via truck mixer. A
concrete pump shall be sent to site ahead of the scheduled time to
start casting concrete due to preparations. Extra concrete pump
shall be provided depending on the volume of concrete required for
the pour.
2.4.2 Site Access
The space between the boundary fence and shoring is very restricted we, therefore, intend to make use of the central area by leaving the ground slab out until removal of cranage. Leaving sufficient time to infill ground slab, construct pools and landscaping. During this time, ramp access will be maintained in the area of J & K building to supply all buildings this ramp will eventually be substituted by the permanent structure.
In the cranage layout, much consideration is made of the ability to pick up from wagons outside the site boundary fence. There “pick up” areas must be kept clear of obstruction and storage during the tower crane period.
Pedestrian access ramp/stair tower will be set up in the corner adjacent to building C – D.
2.4.3 Strategy for the raft slab concrete pouring
It is intended to have 3 management teams looking after different
blocks. Team “A” will be responsible for the raft working in the direction E – W. As they finish at Block J – K, they will continue
vertically on Blocks J and K.
Team “B” will commence on block D as soon as the raft is complete
for that area. They will work progressively to C, B, and A to complete
one half of the complex.
Similarly, Team “C” will commence on Block E as the raft area is released and progress through to Blocks F – H.
At the peak, all blocks will be active which will require considerable
crane hook time.
The majority of structural concrete will be pumped either from outside the site boundary or from the central area of the raft.
2.5 Work methodology for the method statement for raft slab concrete pouring.
2.5.1 Blinding works:
2.5.1.1 After receiving an acceptable formation from (Subcontractor of foundation) i.e. within -20mm + 10mm tolerance, the designated area described on the RFI sheet will be treated and covered with 500 gauge polythene level controls (screeds) will be placed on the surface of the compacted stone.
A 25N mix of high slump concrete blinding will be poured using a pump or direct from the Mixer Truck and spread with rakes and tamps. The surface will be toweled off using “Bull Floats” or Power Floats depending on the setting time of the concrete.
2.5.1.2 In order to minimize shrinkage, cracking the area will be covered over with polythene and welted down or use as a proprietary curing spray.
2.5.1.3 On completion of a zone to be handed over for waterproofing, a joint inspection would be made to identify unacceptable lumps and projections which would be ground off.
2.5.2 Waterproofing application:
2.5.2.1The prepared area would be cordoned off and handed over to
the specialist sub-contractor for application of the 2 layer Bitumen membrane in accordance with the specification. A protection layer will be applied comprising of a 40mm cementitious screed.
2.5.3 Reinforcement installation:
2.5.3.1 It is intended to cut and bend rebar on-site in accordance with prepared bending schedules which accord with the bay layout for the raft slab. The installation of reinforcement will not progress beyond the bay to be concreted in order to allow access to construct
stop ends.
Please note that you should strictly follow the method statement for raft slab concrete pouring.
The splice location will be followed up as per approved bar bending schedule (BBS) shop drawings. The top mat will be supported on chairs from the bottom mat which in turn, will be supported on high-strength concrete blocks of the correct thickness.
2.5.4 Bay Layout:
2.5.4.1 The bay layout and pour sequence shall broadly follow the attached layout. This may vary to suit site conditions. The pour sequence will avoid adjacent bays being cast within 24 hours.
2.5.4.2 The layout also avoids joints through main substructures.
2.5.5 QA/QC Procedure:
2.5.5.1 Inspection Request will be submitted for completed raft slab concrete pouring for the approval of the engineer after Municipality Engineer approval. All related subcontractors’ acceptance will be obtained.
2.5.5.2 Ready-made concrete shall provide from batching plants approved by the consultant. The rate of concrete supply will be 80 – 120 M3 per hour.
2.5.5.3 Quantity of concrete, supervising staff and labor, number of
pump and location and, machinery required, expected duration will be submitted before casting.
2.5.5.4 Number of 2 concrete pumps will be available on-site; the extra pump will be on stand by ready for any incident circumstances.
2.5.5.5 Number of 3 vibrators will be with each concrete pump to improve well compaction for concrete. One vibrator will be on stand-by with each concrete pump. Vibrator should available with diameters 1.5″, 2.0″, 2.5″.
2.5.5.6 Computerized delivery tickets shall be checked for conformity as per the approved mix design.
2.5.5.7 Slump and temperature should be carried from each concrete truck mixer; allowed slump will be 125+\-25 mm. maximum temperature will be 32.
2.5.5.8 All data above (2.5.5.6 & 2.5.5.7) be recorded in the daily concrete schedule sheet (pour card) and to be submitted the next day of pouring. Cube register will be maintained and to be produced along with cube test reports.
2.5.5.9 Required tests (compressive strength and durability) will be directed by the engineer along with the approved inspection request.
2.5.5.10 Concrete at truck mixer shall not exceed more than 90
minutes from adding water to the mix.
2.5.5.11 For each bay, one source of concrete will supply the concrete.
In this case, the bay will be zoned for recording the sources
of supply.
2.5.5.12 On acceptance, mix shall be directly unloaded in the concrete
pumps.
2.5.5.13 Concrete should place on horizontal layers of a maximum 300 mm thick. Each layer shall be placed and compacted by vibrators before receiving the next layer .layers should be placed before the initial set to the previous layer. The vibrator nose should go through layers.
2.5.5.14 When concrete reaches a proposed level, initial hand troweling will be carried out then the finished surface will be power floated. A slope of 1:300 toward the catch basin will be controlled by Screed rails fixed on top of the surface.
2.5.5.15 After the concrete has been set, curing shall be carried out to the horizontal surface for a period of 7 days by means of spreading a Hessian cloth to cover all areas and keeping it moist by
regular spraying of water. For vertical surfaces along with the constriction joint, a curing compound will be applied within 2 hours from removing the side shutter.
2.5.5.16 Construction joints will be scrabbled to prepare a good bonding surface between old and new concrete.
2.5.5.17 Survey report for concrete surface level will be submitted.
2.6 Safety
2.6.1 All operatives shall be given safety induction training by the safety officer before starting work.
2.6.2 Care should be taken in the handling of materials during loading & unloading & shifting to the working area.
2.6.3 Proper lighting to be provided as required on site.
2.6.4 Necessary PPE to be used by all operatives.
2.6.5 Secure & good quality Scaffolding to be provided.
2.6.6 Secure access to be provided for concreting on Site (i.e. ladders & platforms)
2.7 Safety Roles and Responsibility
2.7.1 HSE officer will be involved in all safety measures related to [Company] scope of works. The environmental officer is checking for oil spill
and housekeeping.
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2.8 Organization, Responsibilities, and Supervision
2.8.1 Project Manager
Is overall responsible for the implementation of the approved method statement for raft slab concrete pouring, specifications, drawings, and ensure that his team of Engineers and foremen are aware of it; all resources, humans, materials, and equipment are available to carry out the work as planned without any delay.
2.8.2 QA/QC Manager
Improving quality assurance processes and practices involved in the recruitment and mentoring of QA/QC Engineers.
Developing and driving continuous improvement initiatives.
And overseeing and coordinating the investigation of Customer Complaints and Non-conformities.
Investigating incidences of staff non-compliance of procedures. And Carrying out routine sampling of products
produced. Writing up Quality Assurance manuals.
Preparing for third party and internal audits.
Ensuring that internal and external audits are properly carried out.
Assisting with the training and development of staff.
Dealing with technical issues as they arise.
Maintaining the company’s Standard Operating Procedures
(SOP) system.
Managing the factory internal audit programme.
Ensuring that corrective action is taken to rectify any shortcomings.
Improving relationships with contractors and suppliers.
Supporting the marketing, commercial and business development functions of the company.
Providing input into development protocols.
2.8.3 QA/QC Engineer
Check all the related drawings for mezzanine deck slab ar approved for execution.
Ensure that the storage area is ready to receive materials.
Check the materials delivered to site as per approved drawings and supplier packing lists.
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