Issue 30

G. Jingran et alii, Frattura ed Integrità Strutturale, 30 (2014) 495-501; DOI: 10.3221/IGF-ESIS.30.60 496 MATERIALS AND METHODS Specimen Source aterlogged wood is collected from test pit AT2001 of Haimenkou site with a diameter of 12.7cm, length of 62cm and weight of 7.9kg. It belongs to the middle period, and the species belongs to Pinus yunnanensis (Pinus yunnanensis). Due to the severe degradation, the waterlogged wood is as soft as sponges, which requires the PEG- embedding before sawing the specifications sample. The preparation method was the following: - soak the ancient wood in PEG2000 at 60°C. After 15 days, when the ancient wood is totally immersed in PEG; - dry it in the air and leave it to harden; - Saw the specimen into needed sizes, and put it in water to draw out PEG for 10 days (each day replace clean water). The contrast sample, Pinus yunnanensis (Pinus yunnanensis) healthy wood, is collected from Puer, Yunnan. Experimental methods: Maximum moisture content and basic density Maximum moisture content is measured according to GB/T1931-2009 Method for Determination of the Moisture Content of Wood. To ensure the maximum moisture content of wood during measurement, the saturation of wood with water is needed: - put the sample into a vessel with distilled water; - immerse it totally into water by a stainless steel wire mesh; - leave the vessel to a vacuum drying oven for 1 hour to vacuumize with the vacuum degree of -0.09 MPa; - release the vacuum and still the sample; - conduct measurement after the sample weight becomes stable. Basic density is tested according to GB/T1933-2009 Method for Determination of the Density of Wood, Chapter 7. Experimental methods: Shrinkage, swelling and water absorption Shrinkage is measured according to GB/T1932-2009 Method for Determination of the Shrinkage of Wood; swelling is determined according to GB/T1934.2-2009 Method for Determination of the Swelling of Wood; water absorption is determined according to GB/T1934.1-2009 Method for Determination of the Water Absorption. Experimental methods: Compressive strength parallel to grain of wood The compressive strength parallel to grain of wood is measured according to GB/T1935-2009 Method of Testing in Compressive Strength Parallel to Grain of Wood. Experimental methods: Chemical composition analysis The content of solvent extractives is measured according to GB/T2677.6-94 Fibrous Raw Material—Determination of Solvent Extractives. The content of acid-insoluble lignin is measured according to Fibrous Raw Material—Determination of Acid-insoluble Lignin. The content of holocellulose is measured according to GB/T2677.10-94 Fibrous Raw Material- Determination of Holocellulose. The content of pentosan is measured according to GB/T2677.9-94 Fibrous Raw Material—Determination of Pentosan. Experimental methods: Scanning electron microscope (SEM) examination The scanning electron microscope is Hitachi S-3000N, whose accelerating voltage is 15.0kV. The sample is cut by hand from horizontal, radial and chordwise sections using Germany Leica specialized microtome blade. R ESULTS AND DISCUSSION Maximum moisture content and basic density s is shown in Tab. 1, maximum moisture content and basic density are two scientific and relatively more easily- operated indicators for the degradation degree of waterlogged wood [1]. Waterlogged wood is usually divided into 3 categories according to its preservation states: - Category I, maximum moisture content ≥400%, severe degradation; W A