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
Outline Introduction Research motivation Research goal Smart cementitious composites Cellulose fibre reinforcement Conclusions 2
Introduction 3
Introduction In order to obtain some mechanical strength after crack, steel bars or fibres should be employed. 4
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
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
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
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
Research motivation Multiscale fibre reinforcem ent [1]. 9
Research goal Development of a smart cementitious composite strain or damage sensitive. 10
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
Smart cementitious composites Electrical resistivity variation during tensile or compressive test [2]. 12
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
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
Cellulose fibre reinforcement Fibre cement production, using Hatschek industrial process [4] 15
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
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
Water absorption (%) Cellulose fibre reinforcement Wet dry cycles [5]: 100 80 60 water absorption 40 20 0 water desorption 0 250 500 750 1000 1250 1500 Time (min) 18
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
Cellulose fibre reinforcement Unbleached Kraft fibre after 25 wet / dry cycles [6]. 20
Cellulose fibre reinforcement FL-EQ 18 16 s (MPa) 14 12 10 0 cycles 8 6 4 2 0 40 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
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
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
Cellulose fibre reinforcement 7 days 104 days Calcium hydroxide consumption [7]. 24
sb (MPa) Energy Abs. (N/mm) 30 25 20 15 10 5 0 Cellulose fibre reinforcement REF composites RHA composites 0 5 20 50 Cycles 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0 0 5 20 50 Cycles Mechanical parameters after wet dry cycles [7]. 25
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
Acknowledgments 27
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. 95 162 [3] COUTTS, Robert S. P. A review of Australian research into natural fibre cement composites. Cement & Concrete Composites 27 pp 518-526. 2005. [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. 1988. [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. 2009. 111f. 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. 2005. [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. 2012. 28