Comparative Study on the Behaviour of Geopolymer Concrete with Hybrid Fibers under Static Cyclic Loading Procedia Engineering 173 ( 2017 ) 417 – 423 Available online at www sciencedirect com 1877 7058[.]
Available online at www.sciencedirect.com ScienceDirect Procedia Engineering 173 (2017) 417 – 423 11th International Symposium on Plasticity and Impact Mechanics, Implast 2016 Comparative Study on the Behaviour of Geopolymer Concrete with Hybrid Fibers under Static Cyclic Loading A Joshua Daniela,*, S Sivakamasundaria, D Abhilasha a Department of Civil Engineering, SRM University, Kattankulathur 603 203, India Abstract Geo-polymer is a latest advancement in which the cement is substituted by an eco-friendly Pozzolanic material It is activated by a highly alkaline solution to produce aluminosilicate gel which acts as a binder in concrete In this study cement is fully replaced by Ground Granulated Blast Furnace Slag (GGBFS) Since concrete is fragile steel and glass fibres are supplemented to improve the performance of the concrete These hybrid fibres are optimised by compression test and split tensile test The flexural behaviour of the conventional concrete and a geo-polymer concrete is tested under static cyclic loading for the corresponding optimised percentage of hybrid fibres The experimental test shows significant improvement in the flexural strength, stiffness degradation, cumulative energy dissipation capacity, displacement ductility and the ultimate load with its corresponding deflection © Published by Elsevier Ltd This 2016The TheAuthors Authors Published by Elsevier Ltd.is an open access article under the CC BY-NC-ND license © 2017 (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the organizing committee of Implast 2016 Peer-review under responsibility of the organizing committee of Implast 2016 Keywords: Geo-polymer Concrete; Ground Granulated Blast Furnace Slag; Steel Fibres; Glass Fibres; Static Cyclic Load Introduction Ordinary Portland Cement (OPC) being a significant material in the production of concrete form an indigenous substance to bind aggregates The manufacturing of OPC necessitates firing a large quantity of fuel for the decomposition of limestone, resulting in the emission of carbon dioxide [1] The production of cement causes pollution to the environment and subsequently leads to the depletion of raw material (limestone) Kong., [1] suggested the activation process for a pozzolanic material that is rich in silica and alumina (fly ash) with an alkaline * Corresponding author Tel.:+91-9940087634 E-mail address: ajoshdani@gmail.com 1877-7058 © 2017 The Authors Published by Elsevier Ltd This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the organizing committee of Implast 2016 doi:10.1016/j.proeng.2016.12.041 418 A Joshua Daniel et al / Procedia Engineering 173 (2017) 417 – 423 element at a certain elevated temperature Fly ash when comes in contact with a highly alkaline solutions forming an inorganic alumino–silicate polymer product yielding polymeric Si–O–Al–O bonds known as Geopolymer [2] Silica and alumina atoms react to form molecules that are chemically and structurally equivalent to a natural rock [3] It shows an enhanced bonding property, better abrasion and high impact resistance with less susceptible to chemical attack [4] The use of geopolymer reduces CO2 emission there by helps in minimizing the ecological impact caused by the construction industry Investigation on the properties of the geopolymer concrete (GPC) was carried with a combination of flyash and ground granulated blast-furnace slag and it is observed that such concrete has strength similar to that of the Portland Cement Concrete with a better durability [5] Geopolymer concrete can also be used at elevated temperatures without significant loss in the mechanical properties of the concrete [6] The conventional method of increasing the shear capacity in a beam is to provide a closely spaced transverse reinforcement Which can increase the shear capacity to a certain extent and it will create congestion in reinforcement An alternative technique to overcome this difficulty is to use the randomly distributed steel fiber in reinforced concrete This steel fiber (SF) helps as a bridging element to arrest the propagation of the crack [7-9] To reduce the chemical attack and to increase thermal insulation [10] in concrete glass fibers (GF) were added The brittle catastrophic failure in concrete under cyclic loading is of immense importance in seismic design To reduce the ecological impact on environment nowadays cement is replaced by Pozzolanic material Hence, this study explores the possibility of using the steel fiber and glass fiber in geopolymer concrete and testing it under static cyclic loading to obtain the load-deflection graph The comparisons were made in terms of load deflection behavior, displacement ductility, stiffness degradation and energy dissipation capacity These investigations will provide additional information for the usage of reinforced GPC with hybrid fiber (HF) in a structure subjected to cyclic load Experimental Investigation 2.1 Overview The project deals with the comparative study on the behaviour of an eco-friendly geopolymer concrete and a conventional concrete (CC) with hybrid fibres (HF) under static cyclic loading The HF used in this study is a combination of steel fibre and glass fibres The beam specimens were casted for an optimum value of hybrid fibres (HF) obtained from compression test on cube and split tensile test on cylinder The specimens were fabricated with optimum value of hybrid fibre and tested under static cyclic loading The study comprise the comparative behaviour of conventional and geopolymer specimen with hybrid fibre under static cyclic loading in terms of load deflection behaviour, ductility, degradation in stiffness and energy absorption capacity Table Mix proportion of conventional and geopolymer concrete Materials (kg/m3) Conventional concrete Geopolymer concrete Cement 438 - GGBS - 394 Fine aggregate 651 600 Coarse aggregate 1129.46 1248 Solution 197 97 2.2 Material specification To find the optimum replacement of hybrid fiber a conventional concrete grade of M30 mix designed as per Indian standards and a Ground Granulated Blast Furnace Slag (GGBS) based geopolymer concrete mix designed for a characteristics strength of 30 N/mm2 with constant value of Na2SiO3/NaOH=0.5 and SF⁄AL=0.25 [11] is used in this study The details of the mix proportion are shown in Table The mechanical properties of fibres used in this study were sorted in Table and is shown in Fig 419 A Joshua Daniel et al / Procedia Engineering 173 (2017) 417 – 423 (a) (b) Fig Materials used (a) Steel fibre; (b) Glass fibre Table Properties of steel fibre and glass fibre Fibre L/D Young’s modules (GPa) Tensile strength (MPa) Steel(S) 45 200 1100 Glass(G) 461 600 2.3 Compression and split tensile test To find the optimum replacement of hybrid fibre the compression strength on cubes and split tensile strength on cylinders were performed after 28 days of curing The test was conducted in a Compresion Testing Machine (CTM) with a capacity of 2000 kN The detail of the test result is tabulated in Table Table Hybrid fibre content with compression strength on cube and split tensile strength on cylinder Fibre content (%) Designation Compression strength N/mm2 Split tensile strength N/mm2 10 S90G10 50.09 8.98 80 20 S80G20 47.97 7.98 70 30 S70G30 46.35 7.5 GPC 60 40 S60G40 40.01 6.92 CC 90 10 S90G10 38.21 4.35 Mix Steel(S) Glass(G) GPC 90 GPC GPC 2.4 Detailing of beam specimen The cross sectional dimension of the beam is taken as 150 × 150 mm and the length of the beam is taken as 1200 mm for both conventional and geopolymer concrete specimen Diameter and number of bars provided in the longitudinal and transverse direction of the specimen is shown in Table Table Detailing of the beam along with reinforcement detail Description Mix Type A CC (Conventional) Type A1 GPC (Geopolymer) Fibre content (%) Steel Glass 90 10 Longitudinal Reinforcement 2–10 mm Ø at top 2–12 mm Ø at bottom Transverse Reinforcement legged – mm Ø Fig shows the schematic diagram of the front view and the detailing diagram of the cross section of the specimen The beams were placed on a loading frame with simply supported end condition has a capacity for testing 1000 kN The orientation of the beam was checked using a plumb bob from the centre at the top of the frame to the 420 A Joshua Daniel et al / Procedia Engineering 173 (2017) 417 – 423 centre of the beam The load was applied at a constant rate of increment and the corresponding mid span deflection is measured using dial gauge till it reaches the ultimate load (Fig 3.) Fig Schematic diagram of the front view and cross sectional view of the specimen Fig Typical experimental test setup Results and Discussion To evaluate the flexural behaviour of conventional specimen and a geopolymer specimen with an optimum content of hybrid fibre, these specimens were casted and tested for a three point non-monotonic loading to obtain the load-deflection curve The details of the test results were discussed in the following sections 3.1 Load-deflection behaviour The load deflection response of the specimens was shown in Fig and a comparative envelope of the curve is shown in Fig Type A yields at load higher than the Type A1 whereas the ultimate load of the specimen remains the same The yield stage deflection of the specimens remains the same whereas the ultimate deflection of A1 specimen is higher than Type A specimen Type A1 shows a significant increase in post yield The results are summarization in Table (a) (b) Fig Cyclic load – deflection graph for (a) Type A; (b) Type A1 A Joshua Daniel et al / Procedia Engineering 173 (2017) 417 – 423 421 Fig Comparative envelope of curves Table Summarization of test result Specimen Yield Stage Ultimate Stage Load (kN) Deflection (mm) Load (kN) Deflection (mm) Type A 79.8 4.25 80 4.26 Type A1 77.9 4.25 80 4.41 3.2 Ductility Ductility is the ability of deformation beyond the initial yield deformation without significant loss in strength The realistic method as stated in [12] is used to calculate the displacement ductility With reference to Fig (a) the yield displacement of an equivalent elasto-plastic system with reduced stiffness is found as secant stiffness at 0.75 times of the Ultimate Load (Pu) [12] The yield displacement is directly calculated from the curves shown in Fig and the corresponding values were tabulated in Table From the Table it is observed that the ductility of Type A1 specimen is 4% more than that of the Type A specimen (b) (a) Fig (a) Equivalent elasto – plastic system; (b) Simplified model for stiffness degradation Table Comparision on displacement ductility Specimen Displacement (mm) Ductility Yield Ultimate Type A 4.25 4.26 1.00 Type A1 4.25 4.41 1.04 3.3 Degradation in Stiffness The stiffness degradation of structural elements is defined by the rate of reduction in the stiffness after the occurrence of the yield stiffness Mathematically it is expressed as the ratio of the secant modulus at any particular 422 A Joshua Daniel et al / Procedia Engineering 173 (2017) 417 – 423 load stage to the secant modulus at the yield load with reference to Fig (b) Fig shows the variation in stiffness degradation by plotting a graph between load ratio and corresponding stiffness The stiffness degradation values are shown in Table Fig Stiffness degradation curve Table Comparison on degradation in stiffness Specimen Stiffness (N/mm) Variation in Stiffness degradation Yield Ultimate Type A 18779 18780 1.00 Type A1 18338 18140 0.99 The stiffness degradation for Type A1 specimen is lesser than the Type A specimen These degradation in stiffness is authenticated from the non-dimensional graph (Fig.8) from which it is evident that stiffness degradation and initial slope are proportional to each other Fig Non dimensional graph 3.4 Energy Dissipation Capacity The energy dissipation capacity of a component is also a significant parameter for the evaluation of the post yield response of the specimen The energy dissipation is calculated on the basis of area enclosed by the load deflection curve The measured cumulative energy dissipation capacity of the specimen is presented in Table The stacked value of energy dissipation capacity of the individual cycle is shown in Fig From cycle to cycle the energy dissipation capacity of Type A specimen is higher than Type A1 specimen Whereas in cycle the energy dissipation capacity of Type A1 specimen is higher than Type A specimen The overall energy dissipation capacity of Type A1 specimen is 11 percent more than Type A specimen A Joshua Daniel et al / Procedia Engineering 173 (2017) 417 – 423 Table Comparison on cumulative energy dissipation capacity Specimen Cumulative energy dissipation capacity (kN-mm) Type A 283 Type A1 302 Fig Stacked value of cumulative energy dissipation capacity Conclusion The ultimate load of the specimen remains the same whereas the post yield behavior of geopolymer with hybrid fibre is more than the corresponding control specimen It is observed that the rate of stiffness degradation in geopolymer concrete with hybrid fiber is comparable with the corresponding specimen The displacement ductility and energy dissipation capacity of the geopolymer specimen is better than the conventional, which is evident from the post yield behavior of geoploymer with hybrid fiber specimen References [1] D.L.Y Kong, J.G Sanjayan, Damage behavior of geopolymer composites exposed to elevated temperature, Cement Concrete Composites, 2008, pp 986-991 [2] J Davidovits, Properties of geopolymer cements, International Journal of Alkaline Cements and Concretes, 1994, pp 131–149 [3] D Khale, R Chaudhary, Mechanism of geopolymerization and factors influencing its development: a review, Journal of Material Science, 2007, pp 729–746 [4] N.A Lloyd, B.V Rangan, Geopolymer concrete: a review of development and opportunities, In the Proceedings of 35th conference on our world in concrete and structures, Singapore Concrete Institute, Singapore, 2010, pp 25–27 [5] G Li, X Zhao, Properties of concrete incorporating fly ash and ground granulated blast furnace slag, Cement Concrete Research, 2003, pp 293–299 [6] R Siddique, D Kaur, Properties of concrete containing ground granulated blast furnace slag (GGBFS) at elevated temperatures, Journal of Advanced Research, 2012, pp 45–51 [7] R.N Swamy, H.M Bahia, The effectiveness of steel fibers as shear reinforcement, Concrete Institute., 1985, pp 35–40 [8] P Adebar, S Mindess, D St.-Pierre, B Olund, Shear tests of fiber concrete beams without stirrups, ACI Structural Journal., 1997, pp 68–76 [9] Y.K Kwak, M.O Eberhard, W.S Kim, J Kim, Shear strength of steel fiber-reinforced concrete beams without stirrups, ACI Structural Journal., 2002, pp 530–8 [10] S.A Bhalachandra, A.Y Bhosle, Properties of Glass fiber reinforced Geopolymer Concrete, International Journal of Modern Engineering Research, 2013, pp 2007-2010 [11] A Rajerajeswari, G Dhinakaran Mohamed Ershad, Compressive Strength of Silica Fume Based Geopolymer Concrete, Asian Journal of Applied Science, 2013 [12] R Park, Evaluation of ductility of structure and structural assemblages from laboratory testing, Bulletin of the New Zealand national society for earthquake engineering, 1989, pp 155-166 423 ... to cyclic load Experimental Investigation 2.1 Overview The project deals with the comparative study on the behaviour of an eco-friendly geopolymer concrete and a conventional concrete (CC) with. .. compression test on cube and split tensile test on cylinder The specimens were fabricated with optimum value of hybrid fibre and tested under static cyclic loading The study comprise the comparative behaviour. .. behavior of geopolymer with hybrid fibre is more than the corresponding control specimen It is observed that the rate of stiffness degradation in geopolymer concrete with hybrid fiber is comparable with