PROOFING AGAINST GAS

Wanganui Chronicle, Volume 85, Issue 189, 13 August 1941, Page 8

PROOFING AGAINST GAS

NEW ROTORUA SANATORIUM danger of corrosion Rotorua. Aug. 4. ' Covering an area of 30,000 square < feet and costing £22,000, the founda- ■ tions for the new sanatorium in the I Government Grounds present several • technical difficulties seldom encount- I ered outside Rotorua, stated a Public : Works Department official yesterday. Although the site itself is sound, the ' presence of a highly corrosive natural I gas over the area makes the proofing ; of concrete, paintwork and coloured i cement highly important. Bitumen has been sprayed on to the ] foundation base at a temperature of 350 degrees, and thus a gas-tight layer I of bitumen has been formed before the first concrete is laid down. Concreting has not yet been started, but it is understood that the first layer will be of 3in., after which a further tar-seal will be applied. Another 12in. of concrete will be laid on top and sealed over both upper surface and sides with bitumen. The necessity fop such elaborate precautions was demonstrated in the Public Works Department experimental hut, built over a natural gas vent. Concrete left in the hut showed signs of crystallisation and breaking down. Green coloured cements lost their colour, and samples of paints and primers almost without exception lost colour, gloss and substance. The only material on which the gas had had no effect was a block of bituminous product. ' Another unusual feature of toe construction is the provision of drains for any gas which might build up ■Mdcr the foundations.