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
Composite columns 290 and 240
Building a composite column 240
Building a composite staircase 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 |
