This method statement to defines the requirements for execution of Autoclaved Aerated Concrete aac block masonry work.
The scope of work includes internal and external block walls of the building as per the approved drawings and other contract requirements and project specifications.
Main contractor will submit AAC blocks supplier details and sample for the consultant’s approval, including the AAC blocks adhesive for the consultant’s approval. This submission shall be via the technical submittal.
Preparations for AAC Block Work
The area/floor proposed to start the block work activity in, should be cleaned from any debris, old mortar, dust etc.
Civil surveyor will set out all the required axes, offset lines and points.
The block work area will be wetted with water.
Surface of AAC blocks to be joined with mortar is to be wetted.
The mortar for AAC block will be blocks adhesive.
Base bed courses must invariably be laid in ordinary mason’s mortar, the Composition of bedding mortar 1:1:6 (1 cement: 1 lime: 6 sand).
The joint adhesive thickness should be approximately 2-3 mm, and the thickness of joint for base course bed should be at least 12.5 mm.
Block Work Connections
Wall to Wall connections: In case of L connection interlocking bond will be used, and the galvanized steel ties will be used every three courses in case of T connection.
Wall to column Connection: Mason’s mortar should be used at all wall to column Interface joints, columns should be brushed dust-free, and if necessary roughened by basting to ensure good bond.
Walls should be mechanically tied to columns with 30 cm steel anchor rods 2T10 mm every two courses.
In case of Wall to beam Connections and wall to floor soffit connections: ordinary mason’s mortar should be used.
Block Laying Procedure
The first course of the block will be laid in a full bed of ordinary mortar.
This will be inspected for internal dimensions, door sizes, distances etc.
Block mason will complete the wall on the approved first course.
The maximum height to be built in one day is 1.6 m (8 courses).
For the walls not having opening for doors and windows the heights more than 3 m a concrete tie beam 200 mm depth will be poured for stiffness purposes.
For the walls have opening for doors and/or windows the overhead lintels should be continue along the wall and in this case no need for concrete tie beams.
In-situ reinforced concrete lintels and beams should be 4T10 and T8/30 cm stirrups.
Cast-in-situ reinforced concrete window sills with 200 mm depth, 4T10 and T8/30 cm stirrups.
Keep AAC unit work free of mortar droppings as work progresses and, at completion of work, rub AAC unit to remove excess mortar.
The block walls will be finally inspected by Engineer for verticality, alignment etc.
Maximum variation from plumb: 0.6mm in 3 m, not exceeding 0.9mm in 6m.
Maximum variation from level: 0.6 mm in 6m, not exceeding 12.5mm in 15 m or more.
Inspection checks for block works
Perform following checks for the quality of aac block wall.
- Cleaning of concrete surface.
- Setting out the first course.
- Inspection of the block wall for alignment, verticality and openings etc.