Die Bodenkultur - Journal for Land Management, Food and Environment

R. Pude, C.-H. Treseler, R. Trettin and G. Noga:

Suitability of Miscanthus Genotypes for Lightweight Concrete

Summary

The aim of this experiment was to elucidate the basics of the pressure stability (N mm-2) from not static stressed Miscanthus lightweight concrete from different Miscanthus genotypes. Field experiments with 12 different Miscanthus genotypes (3 M. _ giganteus, 3 M. sacchariflorus, 3 M. sinensis, 3 M. “Robustus”) including studies on morphological, chemical and technical properties were started in the years 2002 and 2003. Morphological parameters like leaf content and bulk density were determined. Chemical analyses were done to measure the content of silicon, lignin and cellulose. Technical aspects were the water binding of the chopped straw, the permanent binding of water in the lightweight concrete and the pressure stability of concrete probes. A SAS-backstep correlation analysis was done on the relationship between the pressure stability and the different morphological, chemical and technical parameters. It was shown, that high cellulose content (34.3–42.9 %) and high content of permanent water binding in concrete (28.6–43.8 %) are responsible for a good pressure stability (0.23–0.61 N mm-2). The highest values were found for M. _ giganteus (Gi1 with 0.61 in 2002 and Gi2 with 0.44 N mm-2 in 2003). In a next step the relationship between cellulose content and water binding was analysed. In morphological studies of Miscanthus cross sections the localisation of cellulose and the uptake of the admixture of water with cement were determined. Most of the fibres were found in the outer ring (sclerenchyma) of Miscanthus stem; here also the cement was located. Additionally, a new method was developed to measure the height, velocity and rate of water uptake in detached stems. The M. _ giganteus genotypes with the thickest outer ring (1.5–1.6 mm), exhibited the highest velocity (16.2 mm min-1) and the maximum height of water movement (2.6 mm). Further Studies should focus on insulating aspects and the shrinkage and creep effect by Miscanthus lightweight concrete. Key words: Miscanthus, genotypes, cellulose, lightweight concrete, pressure stability.