These materials are subject to decay or rust and require extensive maintenance, especially in coastal are as where wind-driven rain, high humidity, salt spray and strong sun subject buildings to extremely adverse conditions. In addition, wood is becoming increasingly expensive and its extensive use raises questions of impact on the environment. Investigations of alternative materials in the production of doors, door frames and window frames have not heretofore included concrete, primarily because of its weight. Recent developments in concrete technology, however, suggest its potential.
New cements are capable of giving concrete much greater strength.
Lightweight aggregates and air-entraining agents reduce the weight of the material. Both of these qualities have been explored extensively within the construction industry. Reinforcement technology is also advancing. Engineers in the field of textiles are developing glass and carbon fiber materials with strengths comparable to the mild steel commonly used in reinforced concrete. The use of textile reinforcement could elimina te problems caused by steel corrosion.