Effect of thermal modification of wood on adhesion and strength properties of wood-cement composition

Introduction. The adhesion properties and factors influencing the formation of the composition of thermally modified timber (TMT) and cement are investigated. The results were focused on the creation of a new material with improved service properties, which is named thermo-wood concrete (TWC).

Materials and methods. Adapted standard methods to assess the adhesion of sand-cement mortar with TMT and compressive strength of sand-cement mortar obtained on waters infused with different types of wood and TMT were applied. The influence of the following factors was considered: the intensity (classes) of wood thermal modification, wood species, mortar formation method, cement binder content, wood surface conditions and moisture content of TMT, the presence of final steam curing of specimens.

Results. The sand-cement mortar with a high content of cement binder had the highest adhesion with TMT. PVA-emulsion solution resulted in additional slight improvement of the sand-cement mortar and TMT adhesion. In general, unmodified (natural) wood had higher adhesion in comparison with TMT under the same conditions. Negative factors included premoistening of thermally modified timber surface, cleaning and leveling of its surface and the use of coniferous species for TMT specimens. The strength of sand-cement mortar was the lowest for specimens with addition of PVA-emulsion. Factor of water purification after infusion with TMT and unmodified wood had insignificant effect on strength of sand-cement mortar.

Conclusions. TMT-cement composition had a lower adhesive force in comparison with unmodified wood. This is due to
the combined effect of low hygroscopicity and wettability of the TMT surface. Water washing of the TMT is inappropriate due to deterioration of adhesion properties of the filler in TWC. To increase the adhesion of the components, it is recommended to use mortars with a high content of cement binder.

1. Gornostaeva E.Yu., Lasman I.A., Fedorenko E.A., Kamoza E.V. Wood-cement compositions with structures modified at macro-, micro-, and nano-levels. Construction Materials. 2015; 11:13-16. (rus.).

2. Nanazashvili I.Kh. The “Quick-to-erect” low-rise monolith buildings from the arbolite. Part 1. Construction materials, equipment, technologies of the XXI century. 2009; 11(130):14-15. EDN WCYJFU. (rus.).

3. Nanazashvili I.Kh., Mardanov M.K. Production of wood concrete from wood waste. Moscow, TsBNTI Minpromstroya SSSR, 1974; 47. (rus.).

4. Al-Akhras N., Abu Alfoul B. Effect of wheat straw ash on mechanical properties of autoclaved mortar. Cement and Concrete Research. 2002; 32(6):859-863. DOI: 10.1016/S0008-8846(02)00716-0

5. Badilla P., Letelier G.V., Aros P., Ca-reau F. Analysis of the mechanical and thermal behaviour of mortars manufactured with combined use of different waste products. IOP Conference Series: Earth and Environmental Science. 2020; 503(1):012017. DOI: 10.1088/1755-1315/503/1/012017

6. Krutov P.I., Sklizkov N.I., Nanazashvili I.Kh., Sirotkina R.B. et al. The use of wood waste to produce efficient building materials : review. Moscow, ONTI TsNIIEPsel’stroya, 1978; 24. (rus.).

7. Sanaev V.G., Zaprudnov V.I., Gorbacheva G., Oblivin A.N. Factors affecting the quality of wood-cement composites. Bulletin of the Transilvania University of Brasov, Series II: Forestry, Wood Industry, Agricultural Food Engineering. 2016; 9(2):63-70. EDN YVARJX.

8. Ramdane R., Kherraf L., Abdelouahed A., Belachia M. Influence of biomass ash on the performance and durability of mortar. Civil and Environmental Engineering Reports. 2022; 32(2):53-71. DOI: 10.2478/ceer-2022-0019

9. Verma Sh., Singh A., Gupta R., Sundriyal S. The effect of wood ash on the workability, water absorption, compressive strength in cement mortar. International Journal for Modern Trends in Science and Technology. 2023; 9(4):368-373. DOI: 10.46501/IJMTST0904054

10. Liu Z., Han Ch., Li Q., Li Xi., Zhou H., Song Xi. et al. Study on wood chips modification and its application in wood-cement composites. Case Studies in Construction Materials. 2022; 17:e01350. DOI: 10.1016/j.cscm.2022.e01350

11. Liu Z., Han Ch., Li Xi., Zhou H., Song Xi., Zu F. Study on Wood chips modification and its effect on the mechanical properties of wood-cement composite material. SSRN Electronic Journal. 2022. DOI: 10.2139/ssrn.4020085

12. Song X., Liu Z., Li X., Zhou H., Han C. Surface modification of wood and its effect on the interfacial bonding properties of cement-based wood composites. European Journal of Wood and Wood Products. 2023; 81(4):897-909. DOI: 10.1007/s00107-023-01926-7

13. Altgen M., Adamopoulos S., Militz H. Wood defects during industrial-scale production of thermally modified Norway spruce and Scots pine. Wood Material Science & Engineering. 2017; 12(1):14-23. DOI: 10.1080/17480272.2014.988750

14. Boonstra M.J., van Acker J., Kegel E.M. Optimisation of a two-stage heat treatment process: durability aspects. Wood Science and Technology. 2007; 41(1):31-57. DOI: 10.1007/s00226-006-0087-4

15. Cai Ch., Heräjärvi H., Haapala A. Effects of environmental conditions on physical and mechanical properties of thermally modified wood. Canadian Journal of Forest Research. 2019; 49(11):1434-1440. DOI: 10.1139/cjfr-2019-0180

16. Hill C. Wood Modification: Chemical, thermal and other processes. John Wiley & Sons, 2006; 239.

17. Hill C., Altgen M., Rautkari L. Thermal modification of wood — a review: chemical changes and hygroscopicity. Journal of Materials Science. 2021; 56(11):6581-6614. DOI: 10.1007/s10853-020-05722-z

18. Militz H. Thermal treatment of wood: European processes and their background. The 33rd annual meeting of The International Research Group on Wood Preservation. Cardiff-Wales, 2002.

19. Hakkou M., Petrissans M., Gerardin P., Zoulalian A. Investigations of the reasons for fungal durability of heat-treated beech wood. Polymer Degradation and Stability. 2006; 91(2):393-397. DOI: 10.1016/j.polymdegradstab.2005.04.042

20. Chernov V.Yu., Gaisin I.G., Palkin A.A., Maltseva E.M. The concrete based on TMW filler: features of the material and prospects of use. Actual problems and prospects for the development of the timber industry : IV International scientific-practical conference. 2021; 103-106. EDN PELBFA. (rus.).

21. Safin R.G., Stepanov V.V., Khairullina E.R., Gainullina A.A., Stepanova T.O. Modern building composite materials based on wood waste. Bulletin of the Kazan Technological University. 2014; 17(20):123-128. EDN SYAHCX. (rus.).

22. Hasanshin R.R. Thermal modification of wood filler in the production of composite materials : doctoral dissertation. Kazan, 2019; 424 . (rus.).

23. Guo A., Aamiri O.B., Satyavolu J., Sun Z. Impact of thermally modified wood on mechanical properties of mortar. Construction and Building Materials. 2019; 208:413-420. DOI: 10.1016/j.conbuildmat.2019.03.016

24. Fu Q., Yan L., Thielker N.A., Kasal B. Effects of concrete type, concrete surface conditions and wood species on interfacial properties of adhesively-bonded timber — Concrete composite joints. International Journal of Adhesion and Adhesives. 2021; 107:102859. DOI: 10.1016/j.ijadhadh.2021.102859

25. Kostic S., Merk V., Berg J., Hass P., Burgert I., Cabane E. Timber-mortar composites: The effect of sol-gel surface modification on the wood-adhesive interface. Composite Structures. 2018; 201:828-833. DOI: 10.1016/j.compstruct.2018.06.108

26. Giv A.N., Fu Q., Yan L., Kasal B. The effect of adhesive amount and type on failure mode and shear strength of glued timber-concrete joints. Construction and Building Materials. 2022; 345:128375. DOI: 10.1016/j.conbuildmat.2022.128375