Application of cellulose fibres in cementitious materials

Transcription

1 Application of cellulose fibres in cementitious materials PhD candidate: Stefan Chaves Figueiredo Prof. Dr. Erik Schlangen Dr. Oğuzhan Çopuroğlu Dr. Branko Šavija Drs. Wolfgang Gard 1

2 Outline Introduction Research motivation Research goal Smart cementitious composites Cellulose fibre reinforcement Conclusions 2

3 Introduction 3

4 Introduction In order to obtain some mechanical strength after crack, steel bars or fibres should be employed. 4

5 Introduction Fibre reinforced cementitious composites These materials are composed by brittle cementitious matrix, reinforced by fibres; They can be cast-in-place, or precast thin sheet composites; The fibres which have usually been applied on these composites are: steel, polypropylene (PP), Polyvinyl alcohol (PVA), asbestos and cellulose pulp; 5

6 Introduction Strain Hardening Cementitious Composites (SHCC): These composites are capable to develop several cracks when loaded on tension; Usually reinforced with 2% by volume of PVA fibres. 6

7 Research motivation Natural fibres can be a fibre solution for the construction market, developing partial or full replacement of steel or synthetic polymers fibres; The use of sensors in order to monitor the conditions of certain infrastructure building in real time would be useful for their maintenance. 7

8 Research motivation Matrix: The employment of cellulose pulp will demand the addition of pozzolanic materials, which are mainly composed of by-products; Fibre reinforcement: Nowadays, besides the PVA fibres, it is often found the employment of wollostonite (mineral fibre); 8

9 Research motivation Multiscale fibre reinforcem ent [1]. 9

10 Research goal Development of a smart cementitious composite strain or damage sensitive. 10

11 Smart cementitious composites Self-sensing cementitious composites are materials which in the composition conductive fillers are added, like carbon nanotubes; This class of cementitious composite are sensible to strain variations; 11

12 Smart cementitious composites Electrical resistivity variation during tensile or compressive test [2]. 12

13 Smart cementitious composites These composites have a complex multiscale conductive filler network; This is a opportunity to develop a high performance cementitious composite with multiscale fibre reinforcement. 13

14 Cellulose fibre reinforcement Fibre cement industry: In 1900 Ludwing Hatschek starts the production of cementitious composites, reinforced by asbestos fibres. The industrial process created by him is still running nowadays [3]. 14

15 Cellulose fibre reinforcement Fibre cement production, using Hatschek industrial process [4] 15

16 Cellulose fibre reinforcement In 1940 some fibres were studied, in order to find a potential material to replace asbestos fibres. At this time, cellulose pulp was pointed as one of the solutions [3]; In beginning of 1980 s starts the industrial production of fibre composite sheets reinforced by cellulose pulp [3]; On the final of 1980 s some countries start to prohibit the use of asbestos [3]. 16

17 Cellulose fibre reinforcement Nowadays, the main issue of this composite is the knowledge of the aging process: Accelerated aging test: Heat-rain cycles; Hot water soaking; Saturation-drying cycles; Freeze-thaw cycles; Deterioration mechanisms and durability tests: based on the moisture transport within the composites 17

18 Water absorption (%) Cellulose fibre reinforcement Wet dry cycles [5]: water absorption water desorption Time (min) 18

19 Cellulose fibre reinforcement Aging mechanism of cellulose fibre cementitious composite [6]: Initial fibre-cement debonding (due to fibre shrinkage during drying); Reprecipitation of hydration products within this new void; Fibre mineralization by the reprecipitation of calcium hydroxide, within the fibre cell wall structure. 19

20 Cellulose fibre reinforcement Unbleached Kraft fibre after 25 wet / dry cycles [6]. 20

21 Cellulose fibre reinforcement FL-EQ s (MPa) cycles cycles 5 cycles 0,0 0,5 1,0 1,5 2,0 2,5 3,0 d (mm) Typical flexural load curve for cellulose fibre reinforced cementitious composites submitted to wet - dry cycles [5]. 21

22 Cellulose fibre reinforcement Alternatives to improve the service life: Fibre coating. Low Ca(OH) 2 matrix: Autoclave cure; Partial Portland cement replacement to pozzolanic materials; 22

23 Cellulose fibre reinforcement One of the most researched field is the employment of different pozzolanic materials that could partially replace Portland cement, in order to decrease the concentration of Ca(OH) 2 on the matrix. Several mineral admixtures have been studied, like: Blast furnace slag; Fly ash; Silica fume; Rice husk ash; Sugar cane bagasse ash 23

24 Cellulose fibre reinforcement 7 days 104 days Calcium hydroxide consumption [7]. 24

25 sb (MPa) Energy Abs. (N/mm) Cellulose fibre reinforcement REF composites RHA composites Cycles 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0, Cycles Mechanical parameters after wet dry cycles [7]. 25

26 Conclusions The development of a new class of smart cementitious composites with a multiscale fibre reinforcement can bring the opportunity of use by-products from different industrial sectors; The employment of cellulose fibres might collaborate to decrease the carbon dioxide emissions, on the construction industry; Self-sensing cementitious composite might be a step forward on the infrastructure monitoring. 26

27 Acknowledgments 27

28 References [1] S. Kwon, Development of Ultra-High-Performance Fiber Reinforced Cementitious Composites using Multi-scale Fiber-Reinforcement System, Tohoku University, Japan, 2015 [2] B. Han, X. Yu, and J. Ou, Sensing Properties of Self-Sensing Concrete, in Self-Sensing Concrete in Smart Structures, Elsevier BV, 2014, pp [3] COUTTS, Robert S. P. A review of Australian research into natural fibre cement composites. Cement & Concrete Composites 27 pp [4] SWAMY, R. N. Concrete Technology and Design. Natural Fibre Reinforced Cement and Concrete. Volume 5. Blackie. Departement of Mechanical Engineering. University of Sheffield. UK [5] ZILLE, Hugo Resende Baêta. Influência de ciclos de saturação e secagem no comportamento de saturação e secagem no comportamento de compósitos de cimento reforçados por polpas celulósicas f. Tese de Mestrado. Departamento de Engenharia Civil. CEFET-MG. Belo Horizonte MG. (In portuguese). [6] B. J. Mohr, Durability of pulp fiber-cement composites, Georgia Institute of Technology. USA [7] C. S. Rodrigues, M. A. Pereira, S. C. Figueiredo, K. Ghavami, P. Stroeven. Durability of cellulosecement composites assessed by accelerated testing under temperature and moisture variations effects of blending by rice husk ash. Proc. Int. Symp. Brittle matrix Composites 10. Warsaw, October