The lightweight insulating concrete shown in this January 1963 photo “was produced with a proprietary preformed foam system which makes it possible to produce cellular concrete of the required weight and strength for each specific job.” According to the article, cellular concrete was developed in Scandinavia 30 years earlier and “four out of every five buildings erected in Sweden are built of cellular concrete.” Although little cellular concrete is in use today, autoclaved, aerated concrete, which takes advantage of the same chemical reaction, is beginning to make some inroads as precast blocks and panels.