MANUFACTURING AND PROPERTIES OF RAPID HAR DENING CEMENT-BONDED PARTICLEBOARDS FABRICATED BY CARBON-DIOXIDE INJECTION - INFLUENCE OF CEMENT STRENGTH CLASS

Cement-bonded particleboards were fabricated from spruce utilizing fou r kinds of portland cements of various strength classes, PKZ 35 F, PZ 35 F, PZ 45 F and PZ 55, by injection with gaseous carbon dioxide duri ng pressing. The bending strengths were determined on not dried specim ens after 7 d, 14 d, and 28 d. The other technological properties were obtained from 28 d old specimens. After 7 d the bending strength of t he fabricated boards amounted to about 90 percent of the ultimate stre ngth properties. A correlation is established between the lime standar d of the cements and carbon dioxide uptake of the boards. With higher cement strength class the weight - carbon dioxide uptake -, the carbon dioxide content, and the bending strength of the boards increase. On the contrary, the modulus of elasticity, the thickness swelling, and l inear movement decrease. Both kinds of cement-bonded particleboards, f abricated according to conventional and carbon dioxide injection proce ss, have comparable bending strengths. On the contrary, the pH of boar ds made by the last mentioned process are lower.