For a long time there have been few new arrivals in concrete technology. Then three of them come along at once.
Thin-joint blockwork. The continental technology of large aerated concrete blocks with thin, 2-3mm, joints is being taken up in the uk. It has mainly been used in industrial and commercial projects. Recently, Celcon constructed a trial bungalow at Prestatyn.
The mortar can set within 30 minutes, making higher lifts and thus faster wall construction possible. Inevitably the blocks must be to tight tolerances, typically +/-2mm in the bed joint. Improved thermal performance is claimed due to reduced joint thickness. Wall ties are fixed into the block rather than into the bed joint.
More technical details are given in bre Digest 432, 'Aircrete: Thin Joint Mortar Systems'. From crc, tel 0171 505 6622. For product details contact: Marketing Dept, Celcon, 01732 886333.
Hollow-block concrete walling. Another approach quite widely used on the continent is building walls of hollow concrete blocks, with reinforcement installed then concrete filling to create a monolithic wall. Both high strength and high speed are claimed.
In Forticrete's Stepoc system the hollow-block wall is built dry around vertical reinforcement rods. Dry sand packing may be needed to ensure verticality. Blocks are either 190 or 256 x 225 x 400mm. Horizontal reinforcement rests in notches in the blocks. A wall can be built up to 2.25m before the first pour, then left 24 hours.
The Stepoc system was recently Agrement tested; certificate 98/ 3450. Contact Forticrete, tel 01298 23333.
Colourful concrete. Keim mineral paints are known for the chemical bond they form with mineral substrates like concrete, giving long life. As well as outdoor use, they have featured in several recent buildings with exposed concrete soffits. They form an effective finish over making good to concrete, an economical alternative to the aim of a defect-free natural concrete finish.
Described as a low pigmentation colour wash, Keim Concretal Lasur is a range of coloured mineral paints available in eight pastel shades. Through dilution it is capable of being adjusted to differing opacities on site. Used over the last 12 months mainly for matching in remedial work, such as at Waterloo International, Keim is now focused on new work too.
Contact Keim Mineral Paints, tel: 01746 714543.