River Rapids Conference Proceedings of the Society for Experimental Mechanics Series Mechanics of Composite and Multi-functional Materials, Volume 7 W. Carter Ralph Raman Singh Gyaneshwar Tandon Piyush R. Thakre Pablo Zavattieri Yong Zhu Proceedings of the 2016 Annual Conference on Experimental and Applied Mechanics River Publishers
Conference Proceedings of the Society for Experimental Mechanics Series Series Editor Kristin B. Zimmerman, Ph.D. Society for Experimental Mechanics, Inc. Bethel, CT, USA
River Publishers W. Carter Ralph • Raman Singh • Gyaneshwar Tandon • Piyush R. Thakre • Pablo Zavattieri • Yong Zhu Editors Mechanics of Composite and Multi-functional Materials, Volume 7 Proceedings of the 2016 Annual Conference on Experimental and Applied Mechanics
Published, sold and distributed by: River Publishers Broagervej 10 9260 Gistrup Denmark www.riverpublishers.com ISBN 978-87-7004-941-2 (eBook) Conference Proceedings of the Society for Experimental Mechanics An imprint of River Publishers © The Society for Experimental Mechanics, Inc. 2017 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, or reproduction in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Preface Mechanics of Composite and Multifunctional Materials represents one of ten volumes of technical papers presented at the 2016 SEM Annual Conference & Exposition on Experimental and Applied Mechanics organized by the Society for Experimental Mechanics and held in Orlando, FL, June 6–9, 2016. The complete Proceedings also includes volumes on Dynamic Behavior of Materials; Challenges In Mechanics of Time-Dependent Materials; Advancement of Optical Methods in Experimental Mechanics; Experimental and Applied Mechanics; Micro and Nanomechanics; Mechanics of Biological Systems and Materials; Fracture, Fatigue, Failure and Damage Evolution; Residual Stress, Thermomechanics & Infrared Imaging, Hybrid Techniques and Inverse Problems; and Joining Technologies for Composites and Dissimilar Materials. This volume presents early findings from experimental and computational investigations in an important area within Composite, Hybrid, and Multifunctional Materials. Composites are increasingly the material of choice for a wide range of applications from sporting equipment to aerospace vehicles. This increase has been fueled by increases in material options, greater understanding of material behaviors, novel design solutions, and improved manufacturing techniques. The broad range of uses and challenges requires a multidisciplinary approach between mechanical, chemical, and physical researchers to continue the rapid rate of advancement. New materials are being developed from recycled source materials, leading to composites with unique properties and more sustainable sources. Existing materials are being used in new and critical applications, requiring deeper understanding of their behaviors and failure mechanisms on multiple scales. In addition, the unique properties of composites present many challenges in manufacturing and in joining them with other materials. Testing needs to be performed on these materials to characterize their properties and new test methods, and technologies must be developed in order to perform these studies and to evaluate parts during manufacture and use. Birmingham, AL W. Carter Ralph Tulsa, OK Raman Singh Dayton, OH Gyaneshwar Tandon Midland, MI Piyush R. Thakre West Lafayette, IN Pablo Zavattieri Raleigh, NC Yong Zhu v
Contents 1 Mechanical and Tribological Properties of Scrap Rubber Based Composites Reinforced with Glass Fiber, Al and TiO2 ............................................... 1 L.M.P. Ferreira, I. Miskioglu, E. Bayraktar, and D. Katundi 2 Investigating Hemp Concrete Mechanical Properties Variability Due to Hemp Particles ........... 9 Ce´sar Niyigena, Sofiane Amziane, and Alaa Chateauneuf 3 Recycling of Scrap Aluminium (AA7075) Chips for Low Cost Composites ...................... 19 L.F.P. Ferreira, E. Bayraktar, M.H. Robert, and I. Miskioglu 4 Scrap Rubber Based Composites Reinforced with Ceramic Oxides and Silica................... 27 D. Zaimova, L.-M.P. Ferreira, E. Bayraktar, and I. Miskioglu 5 Mechanical and Tribological Properties of Scrap Rubber Reinforced with Al2O3 Fiber, Aluminium and TiO2 ............................................................... 37 L.M.P. Ferreira, I. Miskioglu, E. Bayraktar, and D. Katundi 6 Thermo-mechanical Investigation of Fused Deposition Modeling by Computational and Experimental Methods .......................................................... 45 Koohyar Pooladvand and Cosme Furlong 7 Non-Linear Contact Analysis of Self-Supporting Lattice.................................... 55 A. Aremu, I. Ashcroft, R. Wildman, and R. Hague 8 Process Parameter Effects on Interlaminar Fracture Toughness of FDM Printed Coupons . . . . . . . . . 63 G.P. Tandon, T.J. Whitney, R. Gerzeski, H. Koerner, and J. Baur 9 Constitutive Equations for Severe Plastic Deformation Processes ............................. 73 Robert Goldstein, Sergei Alexandrov, and Marko Vilotic 10 Merging Experimental Evidence and Molecular Dynamics Theory to Develop Efficient Models of Solids Fracture........................................................... 81 C.A. Sciammarella, F.M. Sciammarella, and L. Lamberti 11 Comparison of Patch and Fully Encircled Bonded Composite Repair.......................... 101 Stephen A. Theisen and Michael W. Keller 12 Comparison of Composite Repair Performance on Drilled and Simulated Defects ................ 107 O. Ramirez and M.W. Keller 13 Measuring How Overlap Affects the Strength of Composite Tubes in Bending-Torsion............ 115 Sean Rohde and Peter Ifju vii
14 Thermal Cycling and Environmental Effect on Tensile Impact Behavior of Adhesive Single Lap Joints for Fiber Metal Laminate................................... 123 N. Mehrsefat, S.M.R. Khalili, and M. Sharafi 15 Design of Hybrid Composites from Scrap Aluminum Bronze Chips ........................... 131 L.F.P. Ferreira, E. Bayraktar, I. Miskioglu, and D. Katundi 16 Impact Response of Waste Poly Ethylene Terephthalate (PET) Composite Plate................. 139 Ibrahim Bilici, Ali Kurs¸un, and Merve Deniz 17 Particles Reinforced Scrap Aluminum Based Composites by Combined Processing Sintering þThixoforging........................................................... 145 L.F.P. Ferreira, E. Bayraktar, M.H. Robert, and I. Miskioglu 18 Recycle of Aluminium (A356) for Processing of New Composites Reinforced with Magnetic Nano Iron Oxide and Molybdenum........................................ 153 L.F.P. Ferreira, E. Bayraktar, I. Miskioglu, and M.H. Robert 19 A New Multiscale Bioinspired Compliant Sensor......................................... 163 Hugh A. Bruck, Elisabeth Smela, Miao Yu, Ying Chen, and Joshua Spokes 20 Effect of Microstructure on Mechanical Response of MAX Phases ............................ 171 Prathmesh Naik Parrikar, Rogelio Benitez, Miladin Radovic, and Arun Shukla 21 Controlled Placement of Microcapsules in Polymeric Materials .............................. 177 Matthew D. Crall and Michael W. Keller 22 Converse Magneto-Electric Coefficient of Composite Multiferroic Rings ....................... 185 Mario Lopez and George Youssef 23 In-Situ Sensing of Deformation and Damage in Nanocomposite Bonded Surrogate Energetic Materials ................................................................ 193 Engin C. Sengezer and Gary D. Seidel 24 Quasi-Static Characterization of Self-Healing Dental Composites ............................. 203 Dhyaa Kafagy, Kevin Adams, Sharukh Khajotia, and Michael Keller 25 Load Monitoring Using Surface Response to Excitation Method.............................. 209 S. Tashakori, A. Baghalian, M. Unal, V.Y. Senyurek, H. Fekrmandi, D. McDaniel, and I.N. Tansel 26 Elevated Temperature Digital Image Correlation Using High Magnification Optical Microscopy................................................................ 215 W. Carter Ralph, Kevin B. Connolly, and Cheri B. Moss 27 Design of Hybrid Composites from Scrap Aluminum Reinforced with (SiC+TiO2+Gr+Ti+B) . . . . . . . 225 A. Kursun, L.F.P. Ferreira, E. Bayraktar, and I. Miskioglu 28 Manufacturing of Low Cost Composites with Porous Structures from Scrap Aluminium (AA2014) Chips ......................................................... 233 L.F.P. Ferreira, F. Gatamorta, E. Bayraktar, and M.H. Robert 29 Development of Functionally Graded Nodular Cast Iron Reinforced with Recycled WC Particles ......................................................... 241 Rodolfo Leibholz, Maria Helena Robert, Henrique Leibholz, and Emin Bayraktar 30 Aluminium Matrix Composites Reinforced by Nano Fe3O4 Doped withTiO2 by Thermomechanical Process ............................................... 251 L.F.P. Ferreira, I. Miskioglu, E. Bayraktar, and M.H. Robert 31 Implementation of the Surface Response to Excitation Method for Pipes ....................... 261 A. Baghalian, S. Tahakori, H. Fekrmandi, M. Unal, V.Y. Senyurek, D. McDaniel, and I.N. Tansel viii Contents
32 Thermal Methods for Evaluating Flaws in Composite Materials: A New Approach to Data Analysis ................................................................... 267 Davide Palumbo and Umberto Galietti 33 Characterising the Infrared Signature of Damaged Composites for Test Control ................. 277 J.E. Thatcher, D.A. Crump, P.B.S. Bailey, and J.M. Dulieu-Barton 34 Thermoelastic Stress Analysis and Digital Image Correlation to Assess Composites ............... 283 J.M. Dulieu-Barton and G.P. Battams 35 A Study on Mechanical Properties of Raw Sisal Polyester Composites ......................... 287 G.L. Easwara Prasad, B.S. Keerthi Gowda, and R. Velmurugan 36 HPHT In-Situ Strain Measurement of Polymer Composites for Oilfield Applications .............. 295 Daniel Sequera, Yusheng Yuan, and John Wakefield 37 Evaluation of Viscoelastic Characteristics of Polymer by Using Indentation Method.............. 303 Kenichi Sakaue Contents ix
Chapter 1 Mechanical and Tribological Properties of Scrap Rubber Based Composites Reinforced with Glass Fiber, Al and TiO2 L.M.P. Ferreira, I. Miskioglu, E. Bayraktar, and D. Katundi Abstract Scrap rubber/Epoxy composites reinforced with Aluminium, Glass Fibre (GF) and TiO2 particles were prepared and mechanical and tribological properties of these composites were investigated. Basically, these composites are aimed to use in automotive and aeronautics applications. A detail microstructure and matrix/reinforcement interface analyze was made by means of Scanning Electron Microscope (SEM) The wear performance of hard particles reinforced composites were evaluated. Quasi static and dynamic compression tests were carried out and damaged specimens were studied by SEM. The hardness (short test) values of the composites were reviewed related to the reinforcement elements, Glass Fibre-fiber and TiO2 added in the matrix. Keywords Recycling materials • Rubber/epoxy composites • Low-cost engineering • Wear resistance 1.1 Introduction In engineering applications, there are many possibilities for usage of recycling of scrap rubber and most of them are used in automotive industry and domestic area, etc. Other main areas such as the aerospace and microelectronics industries have enourmous demand for high performance (ductile and high toughness) structural adhesive systems like epoxy and/or elastomers reinforced composites [1–9]. Today, additionally, the main component of these waste rubbers is styrene– butadiene rubber (SBR) and, in spite of the different uses for recycling it, the research for new applications is still a need because of the extremely high amount of waste rubber produced every year [5–8, 10–16]. Additionally, these materials are commonly used for long term applications at ambient or at moderately elevated temperature conditions. Conforming to these needs, elastomers (rubbers) should be used by simple processing with various materials in different conditions by addition of new alloying elements [7–11]. The present work reviews manufacturing facilities of scrap elastomers (SBR-rubbers) + epoxy resin composites with different proportions of particulate reinforcements. Main objective of this research was to determine the ductility and toughness of scrap elastomer (SBR rubber) matrix composites containing GF, TiO2, B, etc. as basic reinforcements. Basically, these composites are aimed to use in automotive and aeronautics applications as bumpers and as internal furniture as ductile and tough and sound materials. Scanning electron microscopy (SEM) was used to study the microstructure and fracture surfaces of these composites. L.M.P. Ferreira Materials Science Department, UNICAMP—University of Campinas, Campinas, Sa˜o Paulo, Brazil School of Mechanical and Manufacturing Engineering, Supmeca-Paris, Paris, France I. Miskioglu Department of ME-EM, Michigan Technological University, Houghton, MI, USA E. Bayraktar (*) School of Mechanical and Manufacturing Engineering, Supmeca-Paris, Paris, France e-mail: bayraktar@supmeca.fr D. Katundi Materials Science Department, UNICAMP—University of Campinas, Campinas, Sa˜o Paulo, Brazil #The Society for Experimental Mechanics, Inc. 2017 W.C. Ralph et al. (eds.), Mechanics of Composite and Multi-functional Materials, Volume 7, Conference Proceedings of the Society for Experimental Mechanics Series, DOI 10.1007/978-3-319-41766-0_1 1
1.2 Experimental Conditions At the beginning of the composite design, scrap rubber powders were chemically treated by toluene, acrylic acid and vinyltriethoxysilane (2 %) then dried in an oven to eliminate trace of the chemicals. After chemical treatment, 60 % of scrap rubber and 40 % of epoxy were mixed used as matrix. TiO2 was chosen as main reinforcing element together; with aluminum, glass-fiber, as minor reinforcement elements, boron and Cu were also added in the matrix (Table 1.1). Four basic compositions were prepared after here will be called RETIG-1, 2, 3 and 4. After preliminary blending of the basic elements (scrap rubber + epoxy) of the composites, reinforcement elements were added in the structure and entire of the mixture have been milled for 2 h to obtain a homogenous compound. At the final stage, the specimens were manufactured by hot compacting (double uniaxial action) under a pressure of 70 MPa at the temperature of 180 C. The dwell time for the compacting process was 15 min. All of the specimens (30 mm diameter, 6 mm thick) were cooled down slowly. The post curing was concluded under isothermal conditions at 80 C for 48 h. Shore D hardness test was performed on the polished flat surfaces of the specimens according to ASTM D 2240 using durometer Shore test device, (type HBD-100-0). Shore D was also performed for the samples exposed to Ultra Violet (UV) conditions during exposing time: 2 months (every week during months) to evaluate resistance of these composites against degradation byUV. Macroindentation test was carried out at room temperature using a stainless steel ball with 3 mm diameter. For this test, ten specimens for each composition were prepared with diameter of 40 mm. Thickness of the specimens was variable from 6 up to 10 mm. Maximum force (Fmax) at failure and fracture surface were evaluated by SEM analysis. Again, dynamic compression (drop weight tests) was carried out using a universal drop weight test device, Dynatup Model 8200 machine, with a total weight of 1.9 kg, punch height of 600 mm and with an impact velocity of around 3 m/s. Wear resistance were evaluated by nanoindentation tests under two different normal loads (20 and 50 mN) applied over a linear track of 500μm for 50 cycles. Wear is performed with a conical tip that has 90 degree apex angle. One cycle is defined as a pass and return of the tip over the track; the total distance for one test was 0.050 m. The speed of the tip during wear tests was 50 μm/s. A total of 10 wear test was performed for each sample. 1.3 Results and Discussion General microstructure of the specimens was presented in the Fig. 1.1 for four compositions. All of the microstructures of the composites presented here are more and less homogenous. Chemical fusion bonding of rubber with epoxy powders were made perfectly thanks to the initial chemical treatment of the scrap rubber. Certain area in the structure shows weakly agglomeration of the reinforcements. This type of agglomeration can be improved by milling in longer time. Comparison of hardness (Shore D) results were compared in the Fig. 1.2 for four different compositions after exposing to ultraviolet (UV) during 7, 14, 21, 28 and 45 days. As seen from this graphics, there is no change significantly on the measured values for each period. In reality, all of the specimens have kept their original structure any decohesion between chemical bindings (not chemical deterioration). Addition of boron is always a positive effect on the hardness behaviour of these composites even if its percentage is very low. However, some small cracks appeared on the thin specimens at the end of long exposing time (around 2 months). This behaviour is worthy for the pieces aimed on the production of external parts used for example in the car industry (i.e. bumpers) [7–13]. All of the four composites gave the same level of hardness. Table 1.1 General compositions of the rubber based composites (RETIG) Compositions Matrix Al Glass-fiber TiO2 B Cu Rubber 60% Epoxy 40 % RETIG-1 B 7 7 0 1 1 RETIG-2 B 7 7 7 1 1 RETIG-3 B 7 7 10 1 1 RETIG-4 B 7 7 15 1 1 2 L.M.P. Ferreira et al.
Macroindentation test results were presented in the Fig. 1.3 presented with maximum forces at the failure. A considerable scattering on the values was found for each composite. This type of the damage analysis is very well-meaning related the structure of this type of composites. Damaged surfaces obtained from this test were evaluated by SEM (Fig. 1.4). Fracture surfaces for all of the composites have shown very tough structure without internal defects (porosity, decohesion of the particulate reinforcements, etc.). Ductility is observed in many parts of the surfaces and increasing from the first composite (RETIG-1, TiO2 value is 0 %) up to the fourth composite (RETIG-4, TiO2 value is 15 %) these observations are justified with the results observed from Fig. 1.3. Another damage analysis has been performed by dynamic compression and/or drop weight test as given the entire test conditions in the former section (experimental conditions) and absorbed energy were calculated for each composite via “Mat lab” from the data base (Fig. 1.5). Fig. 1.1 General microstructures of the compositions in transversal section Fig. 1.2 Comparison of Shore D results for four different compositions after exposing to ultraviolet (UV) during 7, 14, 21, 28 and 45 days 1 Mechanical and Tribological Properties of Scrap Rubber Based Composites Reinforced with Glass Fiber, Al and TiO2 3
Fracture surfaces of this test were evaluated in the Fig. 1.6. Again, the glass fibers added in the structure play a role like a bridge between the matrix and reinforcements. In fact, ductile behaviour of these composites is a combined effect of the main reinforcement of TiO2 and glass fibers. Even if the slope is weakly incremental, addition of glass fibre together with TiO2 improves ductility agreement with former papers published in [4, 14, 16]. All of these results obtained by dynamic compression tests confirmed well former results discussed in the Figs. 1.3 and 1.4. Wear track deformation by using nanoindentation tests gave much more information on the micromechanical properties of the composites proposed in this work. Wear resistance were evaluated by nanoindentation tests under two different Fig. 1.3 Maximum values (Fmax) obtained for each composition obtained by macroindentation test Fig. 1.4 Fracture surfaces of the samples for the compositions after macroindentation test presented in this work 4 L.M.P. Ferreira et al.
normal loads (20 and 50 mN) applied over a linear track of 500μm for 50 cycles. Wear damage was performed with a conical tip that has 90 degree apex angle. Figure 1.7 presents total results of this evaluation. Each column in the figure gives mean value of 10 wear tests. One may observed that the wear tracks are not perfectly straight, apparently the conical tip is not fracturing the hard particles (i.e. boron), and just going around them. Another reason can be attributed to the well adhesion of the particles that they are not pulled out of the matrix (without debonding, they keep their positions in the matrix). It means that very good adhesion related to very good interface passage between the particles and the matrix was observed on all of the compositions. Fig. 1.5 Energy and liner tendency as a function of the particulate reinforcements found for four compositions obtained by dynamic compression test Fig. 1.6 Fracture surface of the samples taken from four compositions obtained by dynamic compression tests 1 Mechanical and Tribological Properties of Scrap Rubber Based Composites Reinforced with Glass Fiber, Al and TiO2 5
1.4 Conclusions In the frame of the common research project going on, four new composites were designed from scrap elastomers (SBR) matrix powders essentially reinforced with GF, Al, TiO2, B, B, and pretreated with fine epoxy resin. Chemical treatment of rubber powders with vinyltriethoxysilane gave very successful mixture with epoxy resin resulted by well adhesion bonding with particulate reinforcements. Experimental results obtained from the four different compositions were discussed in the present work. Mechanical and tribological properties of these composites were evaluated under different test conditions. Degradation of the specimens was too low after a long exposure 2 months against UV. Combined effect of TiO2 and glass fibres gives a ductile behaviour in case of impact (drop weight) damage tests. Homogeneous distribution of the reinforcements in the matrix can be improved by longer milling time at the beginning of the process. References 1. Zaimova, D., Bayraktar, E., Katundi, D., Dishovsky, N.: Elastomeric matrix composites: effect of processing conditions on the physical, mechanical and viscoelastic properties. J. Achiev. Mater. Manuf. Eng. 50(2), 81–91 (2012) 2. Papadopoulos, A.M.: State of the art in thermal insulation materials and aims for future developments. Energy Build. 37, 77–86 (2005) 3. Zaimova, D., Bayraktar, E., Miskioglu, I.: Manufacturing and damage analysis of epoxy resin-reinforced scrap rubber composites for aeronautical applications. In: Tandon, G.P., Tekalur, S.A., Ralph, C., Sottos, N.R., Blaiszik, B. (eds.) Experimental Mechanics of Composite, Hybrid, and Multifunctional Materials, vol. 6, pp. 65–76. Springer, New York (2014) 4. Zaimova, D., Bayraktar, E., Miskioglu, I., Katundi, D.: Manufacturing of new elastomeric composites: mechanical properties, chemical and physical analysis. In: Tandon, G. (ed.) Composite, Hybrid, and Multifunctional Materials, vol. 4, pp. 139–150. Springer, New York (2015) 5. Kaynak, C., Sipahi-Saglam, E., Akovali, G.: A fractographic study on toughening of epoxy resin using ground tyre rubber. Polymer 42, 4393–4399 (2001) 6. Yesilata, B., Turgut, P.: A simple dynamic measurement technique for comparing thermal insulation performances of anisotropic building materials. Energy Build. 39, 1027–1034 (2007) 7. Bessri, K., Montembault, F., Bayraktar, E., Bathias, C.: Understanding of mechanical behaviour and damage mechanism in elastomers using X-ray computed tomography at several scales. Int. J. Tomogr. Stat. 14, 29–40 (2010) 8. Bayraktar, E., Antholovich, S., Bathias, C.: Multiscale observation of fatigue behaviour of elastomeric matrix and metal matrix composites by X-ray tomography. Int. J. Fatigue 28, 1322–1333 (2006) 9. Bayraktar, E., Miskioglu, I., Zaimova, D.: Low-cost production of epoxy matrix composites reinforced with scarp rubber, boron, glass bubbles and alumina. In: Ralph, C., Silberstein, M., Thakre, P.R., Singh, R. (eds.) Mechanics of Composite and Multifunctional Materials, vol. 7, pp. 163–172. Springer, New York (2015) Fig. 1.7 Comparison of wear track deformation results tested on the four compositions under the loads of 20 and 50 mN 6 L.M.P. Ferreira et al.
10. Bayraktar, E., Isac, N., Bessri, K., Bathias, C.: Damage mechanisms in natural (NR) and synthetic rubber (SBR): nucleation, growth and instability of the cavitations. Int. J. Fatigue Fract. Struct. Mater. 31(1), 1–13 (2008) 11. Pacheco-Torgal, F., Ding, Y., Jalali, S.: Properties and durability of concrete containing polymeric wastes (tyre rubber and polyethylene terephthalate bottles): an overview. Construct. Build Mater. 30, 714–724 (2012) 12. Luong, R., Isac, N., Bayraktar, E.: Damage initiation mechanisms of rubber. J. Arch. Mater. Sci. Eng. 28(1), 19–26 (2007) 13. Zaimova, D., Bayraktar, E., Miskioglu, I., Dishovsky, N.: Optimization and service life prediction of elastomeric based composites used in manufacturing engineering. In: Tandon, G.P., Tekalur, S.A., Ralph, C., Sottos, N.R., Blaiszik, B. (eds.) Experimental Mechanics of Composite, Hybrid, and Multifunctional Materials, vol. 6, pp. 157–166. Springer, New York (2014) 14. Zaimova, D., Bayraktar, E., Miskioglu, I.: Characteristics of elastomeric composites reinforced with carbon black and epoxy. In: Ralph, C., Silberstein, M., Thakre, P.R., Singh, R. (eds.) Mechanics of Composite and Multifunctional Materials, vol. 7, pp. 191–202. Springer, New York (2015) 15. Nacif, G.L., Panzera, T.H., Strecker, K., Christoforo, A.L., Paine, K.A.: Investigations on cementitious composites based on rubber particle waste additions. Mater. Res. 16(2), 259–268 (2013) 16. Zaimova, D., Bayraktar, E., Miskioglu, I., Katundi, D.: Study of influence of SiC and Al2O3 as reinforcement elements in elastomeric matrix composites. In: Tandon, G. (ed.) Composite, Hybrid, and Multifunctional Materials, vol. 4, pp. 129–138. Springer, New York (2015) 1 Mechanical and Tribological Properties of Scrap Rubber Based Composites Reinforced with Glass Fiber, Al and TiO2 7
Chapter 2 Investigating Hemp Concrete Mechanical Properties Variability Due to Hemp Particles Ce´sar Niyigena, Sofiane Amziane, and Alaa Chateauneuf Abstract Nowadays, the use of bio-source and recyclable materials are experiencing considerable success. They include among others, the wood, the bamboos and the innovative concrete in which vegetable origin aggregates are used. In this latter case, several types of aggregates are used like sunflower, hemp particles, etc. Hemp particles are increasingly used thanks to its environmental asset, such as the positive CO2 balance and its easiness lifecycle management. In construction applications, they have also other advantages like good thermal and acoustic insulation properties. However, its major drawback is related to low mechanical performance. The present work investigates the impact of hemp aggregates on the mechanical properties of hemp concrete. Nine different hemp particles from different origins (country, region, etc.) with varied properties (size, water absorption, etc.) are used in the same conditions (binder, specimen fabrication, etc.). Fabricated specimens were submitted to mechanical compression test, then compressive strength and moduli are analysed. The obtained results show high variability. Hemp particles impact results in a mechanical response with low, medium and high levels of deformation. A factor close to 10 is observed between the minimum and maximum compressive strengths. The performed analyses show that the interaction between the hemp particles and the binder is likely to contribute to the mechanical response. Hence, further investigations taking into account their chemical composition may allow to better understand this interaction impact. Keywords Hemp particles • Mechanical properties • Variability • Hemp concrete 2.1 Introduction The impact of hemp particles on hemp concrete have been treated in some differents studies [1–3]. In those studies, the used hemp are of limited varibility. Morever, the considered properties in those studies are mainly based on particle size and hemp origin [1, 2]. Within those studies, since many parametres are taken into account at the same time, such as the humidity, the binder type, the curing conditions [1], the specimen size [3], etc. then it comes difficult to assess the real impact of hemp particles due to parameter interferences. This study focuses on the variability of hemp concrete due to hemp particles. The selection procedure for nine hemp particles has been developped in a previous study [4] in which many different characteristics are taken into account such as: the water absorption capacity, the hemp particles size including the specific area, the width and length of particles, its mass and also the density. Beyond the selection, the main aim is to predict the imapct of selected hemp particles on hemp concrete mechanical performance. The outcome of this research revealed three categories of hemp particles: category 1 is supposed to result in high mechanical performance, the category 2 in medium performance and the category 3 in low mechanical performance. In this study, it is recommended to conduct laboratory testing in order to validate the predicted results. The main aim of the herein study is to analyse the obtained results. As it will be presented so far, the obtained results are characterized by three main mechanical response behaviors with compressive strengths ranging from 0.11 to 1.10 MPa. C. Niyigena (*) • S. Amziane • A. Chateauneuf Clermont Universite´, Institut Pascal, Polytech’ Clermont-Ferrand, 63174 Aubie`re Ce´dex, France e-mail: cesar.niyigena@polytech.univ-bpclermont.fr; cesar.niyigena@univ-bpclermont.fr; sofiane.amziane@univ-bpclermont.fr; alaa.chateauneuf@gmail.com #The Society for Experimental Mechanics, Inc. 2017 W.C. Ralph et al. (eds.), Mechanics of Composite and Multi-functional Materials, Volume 7, Conference Proceedings of the Society for Experimental Mechanics Series, DOI 10.1007/978-3-319-41766-0_2 9
2.2 Materials and Method Cylindrical specimens of 11 cm in diameter and 22 cm of height were used with nine hemp particles and the same commercial hydraulic binder. The characterization results for bulk density, water absorption and particle size distribution, are detailed in the previous study [4]. The protocols and methods related to manufacturing, mixing process are given in Sect. 2.2. The compressive strength tests have been made using Zwick machine under the same protocol detailed in [3], and the experimental results were collected for variability analysis. The considered mechanical properties are compressive strength and moduli (apparent and elastic); in this later case, the protocol for calculation is detailed in [3]. 2.2.1 Hemp Shiv Characterization The used hemp particles have been characterized in [4], where the main properties considered for their characterization are mainly: the bulk density, the particle size and the water absorption capacity. The main results are given in Table 2.1. Among these 13 characterized hemp particles, based on the recommandations in [4], only 9 have been selected to fabricate specimens of the herein study. They are underlined in the Table 2.1. 2.2.2 Preparation of Compression Specimen 2.2.2.1 Mix Proportioning In construction, hemp concrete has several applications, such as: filling wooden frame walls, roofing insulation, etc. To each application, corresponds a given number of specifications such as minimum compressive strength and Young’s modulus [5], which can be met by specific formulations. For the purpose of the herein study, it has been decided to use a unique formulation corresponding to wall application [5], as the objective is to analyze the effect of hemp particles rather than formulation itself, any other one may have been used. The quantities in kilograms per batch of 100 L are detailed in Table 2.2; these quantities are calculated by taking into account a mean bulk density for hemp particles equal to 120 kg/m3. Table 2.1 Characterization results of differents used hemp particles [4] Nomenclature Bulk density (kg/m3) Initial water absorption (%) Final water absorption (%) Particle mean area (mm2) Particle mass (mg) Particle mean length (mm) Particle meanwidth (mm) Particle elongation Particle equivalent diameter (mm) C1 70.83 159.83 293.05 0.91 0.18 0.64 0.19 2.62 0.32 C2 89.74 194.15 379.22 4.89 0.84 3.4 1.04 3.47 1.79 C3 118.03 242.59 432.49 1.57 0.28 1.11 0.32 2.63 0.58 C4 118.27 233.79 358.33 1.94 0.35 1.45 0.44 2.6 0.76 C5 125.66 153.99 351.28 8.1 1.77 5.88 1.4 4.97 2.78 C6 128.2 181.39 358.53 5.31 1.14 4.2 1.27 3.95 2.23 C7 129.91 163.59 321.94 3.25 0.79 1.93 0.42 3.19 0.84 C8 143.55 152.73 328.04 6.96 1.51 5.59 1.23 5.52 2.53 C9 147.5 211.77 381.47 6.95 1.5 5.11 1.38 4.47 2.58 C10 130.65 112.23 307.31 0.82 0.15 0.77 0.25 2.28 0.41 C11 95.4 165.85 344.58 1.72 0.23 1.46 0.34 3.32 0.66 C12 103.93 162.89 338.7 1.18 0.18 1.02 0.28 2.77 0.5 C13 158.85 226.16 375.06 1.36 0.22 1.11 0.52 2.27 0.8 Minimum 70.83 112.23 293.05 0.82 0.15 0.64 0.19 2.27 0.32 Maximum 158.85 242.59 432.49 8.1 1.77 5.88 1.4 5.52 2.78 Mean 120.04 181.61 351.54 3.46 0.7 2.59 0.7 3.39 1.29 Standard deviation 24.72 37.97 36.38 2.64 0.6 1.96 0.48 1.05 0.94 10 C. Niyigena et al.
2.2.2.2 Mixing of Hemp Concrete The hemp aggregates are put in the mixer with prewetting water equal to a quarter of total amount of necessary water. After few minutes of mixing, the second quarter of water is added with the binder. The mixing is maintained, then depending on the homogeneity of the mixture the third and last quarter of water are added and keep mixing until the perfect mixture homogeneity is obtained. For a good homogeneity, it is better to use a suitable mixer; a specific one for hemp concrete is shown in Fig. 2.1b below. In fact, on one hand, the conventional mixer has primary and secondary blades both fixed on vertical rotating axes (Fig. 2.1a). Only the axis for primary blades is motorised and allow the mixing. During the mixing process the secondary blades are then entrained by the concrete mixture in opposite direction to primary blades. This rotation in both direction allows a good homogeneity for the mixture. In the case of hemp concrete, as it is lightweight, it becomes difficult to induce secondary blades rotation. In opposite, the hemp concrete is stuck inside the blades thus forming a kind of bloc which rotates in the mixer without mixing the constituants properly, which makes this conventinal mixer unsuitable for hemp concrete. On the other hand, a mixer with horizonal rotating axis with blades ramified to it, is well adapted for hemp concrete (Fig. 2.1b). As all blades are connected to the horizontal motorized axis and their possibile rotation in both directions, it becomes more easier and practical to properly mix the hemp concrete. 2.2.2.3 Numbering of Fabricated Specimens According to the recommmendations in [4] for a given hemp particles type, 3 or 9 specimens are fabricated for each type of the 9 selected hemp particles. To identify hemp particles: 9 specimens are considered for “primary test” (C2, C4, C5 and C12), and 3 specimens are considered for “secondary test” (C3, C6, C10, C11 and C13). Therefore the numbering of specimens is as following: P and S for primary and secondary tests, respectively, 11 stands for the size of specimen 11 22 cm, Ci repersents a given hemp particles type and n is the number of the specimen. For example, “P-C2-11-3” stands for primary test from hemp particles C2, size 11 22 cm specimen number 3. Table 2.2 Tested formula for wall application per batch Shiv (kg) Binder (kg) Water (kg) Ratio water/binder Ratio shiv/binder 11.4 23.75 28.5 1.2 0.48 Fig. 2.1 Different mixer type, (a) for classic concrete and (b) specific for hemp concrete 2 Investigating Hemp Concrete Mechanical Properties Variability Due to Hemp Particles 11
2.3 Results and Discussion 2.3.1 Mechanical Response Three main hemp concrete mechanical behaviors have been observed, they differ in their level of strain. On one hand, a law strain around 3 % has been observed (Fig. 2.2); in this case, the maximum compressive stress is observed during the third loading phase before the end of test. On the other hand, a high level deformation is observed and may reach in some cases values beyond 20 % (Fig. 2.5), this last value correponds to the maximum level choosen for the compressive test protocol [3]. Another intermediate behavior is also observed and is characterized by moderate levels with maximum strength values around 5 % of strain (Fig. 2.3). The low level of strain is observed in the case of hemp concrete with small particle size with 1.36 mm2 for particle mean area and a high mean specific area equal to 18,822 mm2/3 g, C13. In fact, for this hemp type, the particules prevent the good a b c 0 0,02 0,04 0,06 0,08 0,1 0,12 0 1 2 3 4 5 6 7 Strength (MPa) Strain (%) S-C13-11-3 Fig. 2.2 Mechanical response: low deformation, specimen before (a) and after (b) test with strength-strain curve (c) a b c 0 0,2 0,4 0,6 0,8 1 1,2 0 1 2 3 4 5 6 7 8 Strain (%) S-C6-11-1 Strength (MPa) Fig. 2.3 Mechanical response with medium deformation, specimen before (a) and after (b) test with strength-strain curve (c) 12 C. Niyigena et al.
connection in bonding matrix, thus weakening the whole material (specimen) and finally resulting in low strength. The failure mode is characterized by the total squashing of the specimen in vertical direction as shown in Fig. 2.2b. In the case of high strain, due to compressive loading, hemp particles rearranged themselves as a stack of layers. In fact, this rearrangement is facilitated by the particle shape, thanks to its high elongation (3.32), resulting is a good overlapping of the particles against each others. Furthermore, it is possible that the high water absorption capacity for this type of hemp (340 % after 48 h) amplifies the level of deformation. As it has been proved [6], there is a competition of water absorption between the binder and the hemp particles. Since this hemp shiv has a high water absorption capacity, the water required for the setting and the hardening process of the binder is absorbed by hemp particles; probably the false setting phenomenon occurs. Then the binder does no longer fulfill its mechanical role, and load is transmitted to hemp particles. As a result, the observed mechanical behavior is similar to that of hemp particles under compression as illustrated in Figs. 2.4b and 2.5b for hemp particles and concrete, respectively. It should be noted that these findings are not necessarily generalizable for all the analysed nine hemp particles types. This let us assume that the chemical interaction between the binder and the hemp Fig. 2.4 Hemp particles mechanical response, before (a) and after (b) compression test [8] a b c 0 0,05 0,1 0,15 0,2 0,25 0,3 0,35 0,4 0,45 0,5 0 5 10 15 20 25 Strain (%) S-C11-11-1 Strength (MPa) Fig. 2.5 Mechanical response with low deformation, specimen before (a) and after (b) test with strength-strain curve (c) 2 Investigating Hemp Concrete Mechanical Properties Variability Due to Hemp Particles 13
particles used can also contribute to the observed mechanical response. The study of the chemical composition and molecules in plant cell surface may help to better understand the impact of the chemical interaction hemp particles/binder on the setting and hardening process of hemp concrete material. In previous studies [6, 7], it was shown that these chemical compounds “extracts” may affect significantly the setting process for hydraulic binders. 2.3.2 Hemp Particles Impact on the Mechanical Performance The previous section illustrates how the mechanical response differs depending on hemp particles. At this stage, only the main behaviors have been discussed. This section, focus on the obtained results for all the nine hemp particles. The main considered properties are the compressive strength and the modulus. 2.3.2.1 Compression Strength The compressive strength results show considerable dispersion at two levels. On one hand, we observe the variability related to used hemp particles with a factor equal to 10 between the minimum and maximum strengths, particularly between hemp particles C13 and C6, respectively (Fig. 2.6). On the other hand, we also observed the significant dispersion within a given type of hemp particle. For example, we have a minimum of 0.47 MPa and 0.65 MPa with a maximum of 0.65 MPa and 0.99 MPa for hemp C2 and C5, respectively (Fig. 2.6). This intrinsic variability of the material shows to what extend the number of samples considered may impact the result, hence it is necessary to take enough samples for statistical significance of results. To our knowledge, there is no specific study for this issue in the case of hemp concrete. In the herein study 9 and 3 samples were used for primary and secondary tests, respectively. The obtained results are presented in the current section, the analysis is proposed later in Sect. 3.3. 2.3.2.2 Elastic Modulus The observed dispersions for compressive strength are also confirmed in the case of the elastic modulus, although we observe low dispersion for C2 hemp concrete. These results highlight also the sensitivity of the variability with respect to the relevant property and of course its measurement method. In [3], the low variability were observed for density, while compressive strength and elastic modulus had high variabilities. 0,12 0,15 0,11 0,20 0,15 0,18 0,42 0,45 0,44 0,42 0,49 0,40 0,41 0,43 0,47 0,55 0,56 0,59 0,48 0,50 0,65 0,47 0,50 0,62 0,63 0,62 0,57 0,45 0,38 0,41 0,38 0,49 0,41 0,39 0,36 0,36 0,47 0,46 0,40 0,77 0,83 0,98 0,85 0,82 0,81 0,89 0,99 0,65 1,02 1,10 1,08 0 0,2 0,4 0,6 0,8 1 1,2 S-C13-11-1 S-C13-11-2 S-C13-11-3 S-C10-11-1 S-C10-11-2 S-C10-11-3 P-C12-11-1 P-C12-11-2 P-C12-11-3 P-C12-11-4 P-C12-11-5 P-C12-11-6 P-C12-11-7 P-C12-11-8 P-C12-11-9 P-C2-11-1 P-C2-11-2 P-C2-11-3 P-C2-11-4 P-C2-11-5 P-C2-11-6 P-C2-11-7 P-C2-11-8 P-C2-11-9 S-C3-11-1 S-C3-11-2 S-C3-11-3 P-C4-11-1 P-C4-11-2 P-C4-11-3 P-C4-11-4 P-C4-11-5 P-C4-11-6 P-C4-11-7 P-C4-11-8 P-C4-11-9 S-C11-11-1 S-C11-11-2 S-C11-11-3 P-C5-11-1 P-C5-11-2 P-C5-11-3 P-C5-11-4 P-C5-11-5 P-C5-11-6 P-C5-11-7 P-C5-11-8 P-C5-11-9 S-C6-11-1 S-C6-11-2 S-C6-11-3 Compressive strength (MPa) Specimen number Maximum compressive strength at 30 days Compression strength Fig. 2.6 Compressive strength results for differents hemp concrete 14 C. Niyigena et al.
The detailed results for all samples (3 for secondary test and 9 for primary test) allowed us to show the variability within a given hemp particles type as illustrated in Figs. 2.6 and 2.7 for both compressive strength and moduli, respectively. For a detailed analysis, the Tables 2.3 and 2.4 give the mean values of all specimens for each hemp particles, the standard deviation and the coefficient of variation. These results are given at 30 days and 180 days, respectively. 17,21 22,45 17,31 17,48 11,87 17,41 34,27 37,39 37,54 35,25 39,19 34,76 38,28 39,66 42,61 52,63 55,78 54,31 55,57 55,81 56,02 52,59 53,96 51,27 56,46 55,94 58,02 30,91 28,30 27,61 31,56 42,76 24,72 26,23 24,73 28,25 18,08 17,98 19,30 84,21 93,69 85,08 82,96 83,77 78,73 108,74 89,46 80,02 100,52 127,84 114,16 0 20 40 60 80 100 120 140 S-C13-11-1 S-C13-11-2 S-C13-11-3 S-C10-11-1 S-C10-11-2 S-C10-11-3 P-C12-11-1 P-C12-11-2 P-C12-11-3 P-C12-11-4 P-C12-11-5 P-C12-11-6 P-C12-11-7 P-C12-11-8 P-C12-11-9 P-C2-11-2 P-C2-11-8 P-C2-11-7 P-C2-11-6 P-C2-11-5 P-C2-11-4 P-C2-11-3 P-C2-11-1 P-C2-11-9 S-C3-11-1 S-C3-11-2 S-C3-11-3 P-C4-11-1 P-C4-11-9 P-C4-11-8 P-C4-11-7 P-C4-11-6 P-C4-11-5 P-C4-11-4 P-C4-11-3 P-C4-11-2 S-C11-11-1 S-C11-11-2 S-C11-11-3 P-C5-11-1 P-C5-11-2 P-C5-11-9 P-C5-11-8 P-C5-11-7 P-C5-11-6 P-C5-11-5 P-C5-11-4 P-C5-11-3 S-C6-11-1 S-C6-11-2 S-C6-11-3 Young's modulus (MPa) Specimen number Elastic modulus at 30 days Elastic modulus Fig. 2.7 Elastic modulus results for different hemp particles Table 2.3 Summary of results at 30 days Specimen number Maximum strength Strength at 5 % of strain Apparent modulus Elastic modulus Mean value P-C2-11 0.55 0.51 29.49 54.22 P-C4-11 0.40 0.34 15.00 29.45 P-C5-11 0.84 0.79 46.77 87.41 P-C12-11 0.44 0.40 16.39 37.66 S-C3-11 0.61 0.60 33.49 56.81 S-C6-11 1.07 1.05 61.00 114.17 S-C10-11 0.18 0.16 4.89 15.59 S-C11-11 0.44 0.22 6.17 18.45 S-C13-11 0.13 0.05 5.68 18.99 Standard deviation P-C2-11 0.06 0.03 6.06 1.73 P-C4-11 0.04 0.04 4.74 5.53 P-C5-11 0.11 0.08 13.17 9.20 P-C12-11 0.03 0.02 1.43 2.67 S-C3-11 0.03 0.03 3.38 1.08 S-C6-11 0.04 0.03 15.53 13.66 S-C10-11 0.03 0.02 1.72 3.22 S-C11-11 0.04 0.01 0.15 0.74 S-C13-11 0.02 0.04 1.42 3.00 Coefficient of variation P-C2-11 11.59 6.15 20.56 3.19 P-C4-11 10.53 12.19 31.63 18.78 P-C5-11 12.48 10.47 28.17 10.53 P-C12-11 6.90 4.92 8.75 7.09 S-C3-11 5.62 4.66 10.10 1.91 S-C6-11 3.82 2.59 25.46 11.96 S-C10-11 14.18 11.77 35.26 20.64 S-C11-11 9.21 2.80 2.42 3.99 S-C13-11 19.05 86.62 24.92 15.79 2 Investigating Hemp Concrete Mechanical Properties Variability Due to Hemp Particles 15
2.3.3 Variability of Result with Respect to Used Hemp Particles 2.3.3.1 Compression Strength Due to the different levels of deformability, especially in the case of high deformation, it is not relevant to assess the compression strength by considering only its maximum value. Because, as discussed early, some types of hemp may be compressed up to high level of deformation, almost infinitely, without breaking (Fig. 2.5c). Therefore, the deformation level reached does not necessarily correspond to the allowable deformation in practice. For this matter, it is important to analyse the compressive strength by considering the associated strain. As result, in the herein study we discuss not only the maximum compressive strength but also the compressive strength at 5 % of strain. According to the obtained results, significant differences are observed with respect to hemp particles type used with a factor equal to 8.2 between the lowest mean value of maximum strength and the highest one, this is the case for hemp C13 and C6, respectively. The obtained coefficient of variation in the case of maximum compressive strength and at 5 % of deformation varies from 1 to 25 % for all criteria (type of hemp, date of test, etc.). This shows to what extend hemp particles induce variability in results. However, in some cases, we observe a relatively high coefficient of variation as for C13 with 86.62 % at 30 days, or 50.71 % at 180 days for the same hemp particles. Note that these dispersions are observed for the compressive strength at 5 % of strain. Indeed, since C13 has low levels of deformation as shown in Fig. 2.2, it follows that the compressive strength values obtained at 5 % are too dispersed. Table 2.4 Summary of results at 180 days Specimen number Maximum strength Strength at 5 % of strain Apparent modulus Elastic modulus Mean value P-C2-11 0.57 0.55 29.09 58.84 P-C4-11 0.42 0.31 15.09 33.12 P-C5-11 0.87 0.82 40.42 88.97 P-C12-11 0.42 0.36 14.12 35.22 S-C3-11 0.66 0.61 30.99 55.98 S-C6-11 1.07 1.02 42.79 103.44 S-C10-11 0.25 0.18 7.68 20.94 S-C11-11 0.40 0.21 10.91 20.08 S-C13-11 0.13 0.10 12.27 20.72 Standard deviation P-C2-11 0.04 0.03 4.36 6.72 P-C4-11 0.07 0.08 2.95 5.95 P-C5-11 0.06 0.06 12.09 11.90 P-C12-11 0.07 0.05 1.21 4.84 S-C3-11 0.05 0.04 3.42 4.54 S-C6-11 0.14 0.15 14.94 22.93 S-C10-11 0.00 0.00 1.15 0.78 S-C11-11 0.05 0.01 2.15 1.78 S-C13-11 0.02 0.05 4.76 4.70 Coefficient of variation P-C2-11 7.68 5.08 14.99 11.42 P-C4-11 17.16 24.32 19.52 17.97 P-C5-11 6.72 7.90 29.90 13.38 P-C12-11 15.68 13.82 8.58 13.75 S-C3-11 7.15 6.69 11.05 8.11 S-C6-11 13.45 14.18 34.92 22.17 S-C10-11 1.96 0.91 15.00 3.72 S-C11-11 13.40 3.92 19.67 8.85 S-C13-11 15.41 50.71 38.77 22.67 16 C. Niyigena et al.
2.3.3.2 Modulus Since it is known that there is a relationship between compressive strength and modulus, one can expected to have the same variability for modulus results as for compressive strength ones. However, the analysis in the case of modulus indicates that these dispersions are not necessarily the same. The mean values obtained vary from 4.89 MPa to 61.00 MPa and 15.59 MPa to 114.17 MPa for the apparent and elastic modulus, respectively. Such dispersions are obtained by considering different types of hemp particles and both testing dates. Furthermore, in the same configurations, the observed coefficient of variation varies from 2.4 % to 38.8 % and 1.9 % to 22.7 % for the apparent and elastic modulus, respectively. 2.4 Conclusion In this study, the problem for suitable hemp concrete mixer has been discussed and it has been highlighted that the use of classic mixer result in non-homogeneous mixture. The results of the study show that hemp particles may impact considerably the hemp concrete mechanical properties. By changing only hemp particles, a factor of 10 has been observed between minimum and maximum values for compressive strength. It has also been highlighted the three main mechanical response behaviors for hemp concrete material characterized by the low, medium and high level of strain. These observed behaviors are related to hemp particles shape and their water absorption capacity. It has also been highlighted that probably the hemp particles/binder chemical interaction may also impact the observed behavior, thus, it is necessary to undertake more investigations, which may focus on the chemical composition and molecules in plant cell surface as they may affect significantly the setting and hardening process for the binder. Acknowledgments The authors would like to thank the Auvergne Region Council for their financial support of this work. References 1. Arnaud, L., Gourlay, E.: Experimental study of parameters influencing mechanical properties of hemp concretes. Constr. Build. Mater. 28(1), 50–56 (2012) 2. Stevulova, N., Kidalova, L., Cigasova, J., Junak, J., Sicakova, A., Terpakova, E.: Lightweight composites containing hemp hurds. Procedia Eng. 65, 69–74 (2013) 3. Niyigena, C., Amziane, S., Chateauneuf, A., Arnaud, L., Laetitia, B., Collet, F., Escadeillas, G., Lanos, C., Lawrence, M., Magniont, C.: RRT3: statistical analysis of hemp concrete mechanical properties variability. In: First International Conference on Bio-Based Building Materials, Clermont-Ferrand, France (2015) 4. Niyigena, C., Amziane, S., Chateauneuf, A.: Etude de la variabilite´ des caracte´ristiques de granulats de chanvre. Rencontres Universitaires de Ge´nie Civil, Bayonne, France (2015) 5. FFB: Construire en chanvre: Re`gles professionnelles d’exe´cution. Fe´de´ration Franc¸aise du Baˆtiment. Collection recherche de´veloppement me´tier (2009) 6. Dique´lou, Y., Gourlay, E., Arnaud, L., Kurek, B.: The impact of hemp shiv on cement setting and hardening: the influence of extracts and study of the interface. In: Proceeding of the International Inorganic-Bonded Fiber Composites Conference, Acton, Australia. pp. 41–50 (2012) 7. Diquelou, Y.: Interactions entre les granulats de chanvre et les liants a` base de ciment et de chaux: Me´canismes de la prise et proprie´te´s des interfaces forme´es dans les agrobe´tons. Reims (2013) 8. Gourlay, E.: Caracte´risation expe´rimentale des proprie´te´s me´caniques et hygrothermiques du be´ton de chanvre. De´termination de l’impact des matie`res premie`res et de la me´thode de mise en oeuvre. ENTPE (2014) 2 Investigating Hemp Concrete Mechanical Properties Variability Due to Hemp Particles 17
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