Block work-Method statement

CONCRETE BLOCK WORK

1.0 OBJECTIVE

1.1 Is to define the requirements for supply and laying of concrete block work for the buildings and utilities under the contract no GTC.101/ED/01 Engineering, Procurement, Installation and Commissioning (EPIC) of Ras Laffan Utilization Project –Buildings and utilities and support service Phase 1-Utilities.

2.0 SCOPE

2.1 Concrete block work for buildings and utilities in Service Base Area, Service Berth and F.S.O Marine area and Telecom building.

3.0 REFERENCE

3.1 Project Approved Drawings

3.2 Qatar Petroleum Standard Specification for Civil Works Vol. I, Section 4

3.3 British Standards BS 6073, BS 4027, BS 12, Bs 1200 table 1, BS 4887, BS 1243          Table-3, BS 743 type-C, BS 3416-type 1, Class A

4.0 PROCEDURE

4.1 SPECIFICATION FOR MATERIAL

4.1.1 BLOCKS

• Concrete block work shall conform to requirements of BS 6073 . Crushing strength test report shall be submitted to QP engineer for approval before the block are delivered to site.

• Block shall be hollow or solid as per drawings.

• The average compressive strength of 10 sample blocks shall be of
  7N/mm² and no individual bock shall be less than 5.6N/mm².

• The thickness of the webs and walls shall not be less than 50mm and the volume of the cavities in the block shall not exceed 50% of the gross volume of the block.

• All surfaces shall be flat and rectangular and adjacent surfaces shall be at right angles to one another.

• Unless otherwise specified all block faces shall provide a satisfactory bond for motor, plastering or rendering.

• Each block manufactured from sulphate resisting cement shall be color coded with a green identifying mark.

• AGGREGATE :

•  Fine and coarse natural aggregates shall comply generally with BS 882.

•  The chloride content of the fine and coarse aggregates, tested in accordance with BS 812, part 4, shall not exceed 1.0% of the weight of cement used in manufacturer of the block.

•  Sand for motor shall be selected beach or dune sand, washed clean and free from clay, chalk, shells, organic materials and other impurities. The sand shall comply in all respects with BS 1200, table-1.

4.1.3 CEMENT: Cement shall be Portland cement to BS 12, sulphate                           resisting cement shall comply with BS 4027.

    4.1.4 WATER:  It shall be Potable.

     4.1.5 WALL TIES: Wall ties shall be Stainless steel/galvanized steel vertical twist                           type complying with BS 1243 table 3.

     4.1.6 DAMP-PROOF COURSE (DPC):

              DPC shall be asbestos based bitumen to comply with BS 743 type 3 or plastic                  type to the approval of the QPengineer.

     4.1.7  BITUMINOUS PAINT: Shall be cold applied black bitumen coating solution to                    BS 3416 type 1, class A.

     4.1.8  REINFORCEMENT FOR BLOCK WORK: Reinforcement required to be built                     into block work and horizontal joints shall be galvanized steel expanded metal                type, minimum 24 gauge to the widths specified.

     4.1.9  MORTAR MIXES:

• Mortar mixes shall be accurately gauged by volume using approved gauge boxes.
• The ingredients shall first be mixed dry until thoroughly mixed to a uniform color before water is added to the mix.

• All mortar shall be used within 30 minutes of mixing. No mortar, which has achieved its initial set, shall be used in the work, and no water is to be added to the mortar, after the initial mix.

• Mortar samples shall be prepared and tested in accordance with BS 4551 and as instructed by the QPengineer.

• For work below floor slab level and work in contact with the ground: 1 part sulphate-resisting cement: 3parts sand.

• For all other work : 1 part ordinary Portland cement : 6 parts sand.

4.2 BLOCK WORK:

• Block work shall be constructed generally in accordance with BS 5628 part 1.1978.

• The area is to be cleaned, all loose materials to be removed.

• Before starting of block work, the area is to be washed with water.

• All block shall be thoroughly wetted with water before they are laid and tops of walls left from previous day work shall be similarly wetted before the new work commences.

• Block work shall rise at the rate of four courses per 900mm. A maximum of 6 courses being built in a section in any one day.

• Walls shall be built in stretcher bond unless otherwise specified.

• Cutting of blocks shall be kept to a minimum. When cutting of blocks is essential, a bolster shall be used in preference to a trowel.

• All units shall be laid on a full bed of mortar in perfectly horizontal courses. All perpend joints shall be in perfect vertical alignment and well filled by buttering the ends of the unit and then sliding into position against its neighbor. Collar joints shall be filled by buttering the stretcher side.

• All joints shall be solidly filled and the thickness of the joints shall not exceed 10mm. All mortar joints shall be finished flush with the general face of the wall unless otherwise specified.

• Hollow block at jambs, reveals of opening etc shall be filled solid with concrete.

• Curing of block work should be done for at least 7 days.

• MOVEMENT JOINTS:

               4.3.1  The movement joints to be 12mm wide as per position indicated on the                            drawings. The joints shall be straight vertical and formed with uncut faces               of the blocks to each side.

     4.4 EXPANSION JOINTS:

• Expansion joints are to be as per positions indicated on the drawing.

• The expansion joints shall be filled with bitumen impregnated fiberboard to finish 15mm back from each face of the wall.

• All exposed edges of the expansion joints shall be pointed with two part gun-grade poly sulphide sealing compound 15mm deep neatly finished flush with the wall face and colored if specified on the drawings.

     4.5 BLOCK WORK ABUTTING STRUCTURAL CONCRETE:

     4.5.1  Where block work abuts structural concrete columns or walls and the like it            shall be tied to the concrete with bitumen coated steel ties at 225 mm        vertical centers. The ties shall be 50X3X600 mm girth once bent, one end shall be securely short filed to concrete and the other and solidly built into the     block work, unless otherwise specified.

    4.6 REINFORCED BLOCK WORK:

• Where specified on the drawings walls shall be reinforced with horizontal joints reinforcement at the vertical intervals specified.

• The width of joints reinforcement will be that recommended by the manufacturer for each thickness of wall.

• The joints reinforcement shall be completely bedded in the mortar and lapped at least 75 mm at joints in the length. At corners the joints reinforcement shall be cut neatly and butted together but not lapped.

 4.7  DAMP-PROOF COURSES AND TREATMENTS:

• Check for the requirement of DPC as per approved drawings. If DPC is required it shall be laid horizontally in external and internal walls at ground floor level in positions indicated on the drawings.

• Damp-proof courses shall be laid horizontally in external walls at the last roof level and above openings. Vertical damp-proof courses shall be built into external cavity walls at jambs of openings and in the positions indicated on the drawings.

• Horizontal damp- proof courses shall be laid on a continuous bed of cement and sand (1:3) mortar and lapped minimum 150mm at joints in the length and lapped the full width of the wall at corners and passing.

• All concealed wall surfaces below DPC level shall be painted with two coats bitumen paint and enclosed in minimum 1000 gauge polythene sheet membrane, the polythene sheet measure shall be tightly dressed up against the wall face and turned over the top of the block work for a width of alt least 50mm under damp-proof courses internally and on the wall courses immediately below the finished ground level externally. The polythene sheet membrane shall lap a minimum 100mm at all joints.

  5.0  PROTECTION TO BLOCK WORK:

• Block Work shall be protected from damage by wet weather with QP approval coverings extending down both sides of exposed walls.

• All work shall be protected against rapid drying out by an approved method.

• Necessary steps to protect work to prevent damage by the building operations

6.0  RECORDS

• Inspection Reports
• Checklist 
• Mortar test certificate