This technique is extensively used in Auroville since 1993. U-shaped CSEB are reinforced with reinforced cement concrete. Reinforcements vary with the span, but the rod diameter cannot exceed ø 12 mm for the Auram blocks 290 & 295 and ø 16 mm for the Auram blocks 240 & 245.

The U blocks are used as lost shuttering, but they also help the compressive strength of the beam. Hence it becomes a composite technique as the reinforced concrete work in tension and the U block works in compression. The concrete cast in the U shape is normally 1 cement: 2 sand: 4 gravel ½’. The vertical mortar in between the U blocks is cement sand mortar CSM 1: 3 of 1 cm thickness. Three types of beams have been developed, elaborated below.