Composite Columns

Composite Columns

This technique is extensively used in Auroville since 1995. Two types of round hollow CSEB have been designed: the round block 240 and the round block 290. These blocks are reinforced with reinforced with cement concrete. Both types of blocks are laid with a cement sand mortar CSM 1: 3 of 1 cm thickness. Note that stabilised earth mortar cannot be used for this composite technique for the reason that the stabilised earth mortar will shrink and will not adhere on the steel rods. The steel rods do not exceed 1.5 m high, as it is difficult to slide down the blocks if the steel bars are the entire height of the column. Therefore some extension rods are regularly placed with an overlap of 50 time the bar diameter.

Block 240

Block 240 (240 mm diameter) •    Vertical reinforcements should be ø 12 mm for the blocks 240. •    Stirrups must be ø 6 mm and placed every 20 cm c/c. •    The holes where the reinforcement are inserted are cast with concrete 1 cement: 2 sand: 4 (1/2” gravel) •    The columns 240 must be linked on 2 sides of the building       (through a beam or ring beam). It cannot be left free standing (without any link through a beam to the building). •    Note that this block should not be used for seismic zones.

Block 290

Block 290 (290 mm diameter) •    Vertical reinforcements should be ø10 mm for the blocks 290, as the holes are not large enough to accept a bigger diameter. •    Stirrups must be ø 6 mm and placed every 20 cm c/c. Note that for seismic zones, stirrups should be ø8 TS and placed at 10 cm c/c •    The holes, where are inserted the reinforcement, are cast with concrete 1 cement: 2 sand: 4 (chips gravel) •    The columns 290 can be linked only on 1 sides of the building (through a beam or ring beam). It cannot be left free standing (without any link through a beam to the building). •    Note that this block can be used for seismic zones.

Building a composite column 290

Trench foundation for a composite column 290

Steel reinforcement for a composite column 290

Casting concrete in holes and fixing a stirrup

Casting the plinth beam

Checking the level of the first block

Casting concrete in the holes

Fixing a stirrup

Checking the spacing of bars

Steel reinforcement at the head

Casting the head with the beams

Completed head

Composite columns 290 and 240

Section of a composite column 290

Composite columns 290 and 240

Building a composite column 240

Steel mat with ø 12 TS	Sliding down a round block 240	Adjusting the level of the first block
Laying mortar 1 cement: 3 sand	Inserting a stirrup ø 6 MS, 9 cm diameter	Casting concrete 1 cement: 2 sand: 4 gravel ½”

Building a composite staircase 290

Placing a precast concrete step for a staircase	Adjusting a block for a staircase	Casting a stirrup with 1 cement: 3 sand
Inserting a block for a staircase	Laying the landing slab	Completed staircase completed in 3 days
	Composite staircase 290 completed after 3 days

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