Abstract
The paper presents research focused on behaviour of cement-bonded particleboards with modified composition during sudden changes of temperature and humidity. Four types of boards were made—one control and three modified ones. Finely ground limestone was used as a modifying component in binder. Secondary wood particles made from crushing cuttings of cement-bonded particleboards were used as chips substituent. Two sets of test specimens (1 set = 6 test specimens) were manufactured. The first set was stored in laboratory conditions. The second set was subjected to 10 cycles of sudden changes of temperature (− 20 °C to + 70 °C) and humidity in accordance with EN 321 (further in the paper referred to as “wet–frost–dry cycle”.) After each cycle, dimensions and mass of the test specimens as well as ultrasonic pulse velocity were determined. A detailed analysis of structural changes in boards during cycling was carried out by an optical microscope. After 10 wet–frost–dry cycles were completed, bending strength and modulus of elasticity in bending were determined. The analysis of test results implies a very good relation between change of ultrasonic pulse velocity and width of cracks in the area of interfacial zone between cement matrix and wood particles. This finding also corresponds with dimensional and volumetric changes of the boards. Dependence of bending strength and modulus of elasticity in bending on composition of boards is apparent. Positive influence of secondary spruce chips on dimensional changes of cement-bonded particleboards caused by sudden changes of temperature and humidity was proved. Finely ground limestone contributes to more resistant structure of boards which leads to improved bending properties. Adverse conditions had more considerable influence on bending strength (decrease by 21% to 26%) than on modulus of elasticity in bending (decrease by 12% to 19%).
Highlights
Resistance of cement-bonded particleboards to action of sudden changes of temperature and humidity is limited by material composition of the boards
Changes of relative humidity at constant temperature can be characterized as slower compared to wet–frost–dry cycling
Based on the results and findings including comparison with findings of other authors, it can be stated that wet– frost–dry cycling in accordance with EN 321 is reasonable for verification of cement-bonded particleboards durability
Summary
Resistance of cement-bonded particleboards to action of sudden changes of temperature and humidity is limited by material composition of the boards. From this point of view, properties of spruce chips are very important [1]. By adjusting properties of wood in cement-bonded composite materials it is possible to achieve better properties of the final composite material [2,3,4,5,6,7,8]. Composition of cement-bonded particleboards can be modified by both matrix and filler [9,10,11,12,13,14,15]. Possibility of using waste from cement-bonded particleboards is presented only in [16]. The authors analysed the waste as an alternative component for concrete
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