Open access publications in the SLU publication database

Abstract

The incorporation of recycled papers, paperboards and Tetra Pak as filling materials in brittle matrices presents an interesting approach in the utilization of waste materials for building construction. This paper examines the compressive strength and microstructure of gypsum-bonded wastepaper-based composites. Recycled wastepaper of various types (office paper, magazine paper and newspaper), cardboards, paper boxes and Tetra Pak were shredded to short length strips of about 4 x 18 mm. The shredded materials were used as filling materials in natural gypsum in a ratio of 1:3 (v/v), and water was added to the mix. The paste was formed in cylindrical samples measuring 10 cm in length and 5 cm in diameter. Seven different types of composites were produced depending on the material used. The composite products with newspaper and magazine paper had significantly lower density and compressive strength (p < 0.05) than the others. However, the differences were small to have any practical importance. The density values ranged between 1.26 and 1.34 g/cm(3), and compressive strength was the lowest (4.48 N/mm(2)) in the gypsum-magazine paper composites and the highest (6.46 N/mm(2)) in the gypsum-Tetra Pak I composites. Since the samples produced in this study exhibited adequate compressive strength, the products could be suitable for such applications as interior walls in building constructions. Scanning electron microscopy (SEM) examination of the fractured surfaces revealed needle-like structures of gypsite crystals surrounding the fibers, which indicates good adhesion between the hydrophobic matrix and lignocellulosic fibers.