CRACK BEHAVIOR STUDY OF BAMBOO REINFORCED CONCRETE BEAM WITH ADDITIONAL PEGS IN REINFORCING

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1 International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 7, July 2018, pp , Article ID: IJCIET_09_07_175 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed CRACK BEHAVIOR STUDY OF BAMBOO REINFORCED CONCRETE BEAM WITH ADDITIONAL PEGS IN REINFORCING Sri Murni Dewi Civil Engineering Department, Brawijaya University, MT. Haryono street 167 Malang East Java, Indonesia Devi Nuralinah Civil Engineering Department, Brawijaya University, MT. Haryono street 167 Malang East Java, Indonesia As ad Munawir Civil Engineering Department, Brawijaya University, MT. Haryono street 167 Malang East Java, Indonesia Ming Narto Wijaya Civil Engineering Department, Brawijaya University, MT. Haryono street 167 Malang East Java, Indonesia ABSTRACT This research concerned about the effect of additional pegs along the bamboo reinforcement in order to increase the bond strength of reinforcement in bamboo reinforced concrete beam. A new technique was developed in this research to improve the mechanical properties of bamboo reinforcement and improve composite strength between bamboo and concrete. Wooden pegs and hose clamps ring pegs are used as adders bonding strength between concrete and reinforcement. The level of flexural performance after concrete cracking occurs, is an important factor that can be used to assess the effect of the pegs on the flexural performance of the bamboo reinforced concrete beam. The results of this study indicate that bamboo reinforcement with additional pegs develops adequate bonding with the concrete matrix, but a smaller interval of pegs reduces the bonding strength. Installation of hose clamp pegs increase the bond slip parameter from 1 MPa to 1,6 MPa. Key words: Bamboo, pegs, bond strength, flexural performance. Cite this Article: Sri Murni Dewi, Devi Nuralinah, As ad Munawir and Ming Narto Wijaya, Crack Behavior Study of Bamboo Reinforced Concrete Beam with Additional Pegs in Reinforcing. International Journal of Civil Engineering and Technology, 9(7), 2018, pp editor@iaeme.com

2 Sri Murni Dewi, Devi Nuralinah, As ad Munawir and Ming Narto Wijaya 1. INTRODUCTION The failure of Bamboo Reinforced Concrete (BRC) members have been observed mainly due to weak bond between bamboo and concrete [1,2]. Compared to Steel Reinforced Concrete (SRC) there is some difference of cracks behavior between bamboo reinforcing concrete beam and steel reinforce concrete beam. Cracks in the steel reinforced concrete beam causing yielding of the reinforcement. Cracks in the bamboo reinforced beam causing slip between bamboo and concrete. There is also difference friction strength between bamboo and steel bar. Bond comprises three components: (a) Adhesion (b) Friction (c) Mechanical interaction between concrete and reinforcement. A plain bar embedded in concrete develops bond by adhesion between itself and the concrete, and by a small amount of friction [3, 4]. Both of these effects are quickly lost when the bar is loaded in tension, particularly as the diameter of the bar decreases slightly due to Poisson s ratio or some corrosion [5]. For this reason, plain bars are not generally used as main longitudinal reinforcement, but where they must be embedded in concrete, mechanical anchorage in the form of hooks, nuts washers or similar devices are used to provide adequate anchorage. The adhesion between reinforcement bars and concrete matrix is developed principally through development of residual compressive stress due to concrete shrinkage at the interface of reinforcement and concrete. Friction is developed due to surface roughness of reinforcement bars. Bonding establishes a shear resistance at the concrete matrix interface with reinforcement. The reinforcement and concrete matrix together resist external loads before concrete cracking occurs. If the tension strength of concrete exceeded, tensile cracks growth in the concrete. Cracking in reinforced concrete structures is generally influenced to the stress distribution along the interface between steel and concrete. When the first crack appears in the weakest point of the structure, the concrete stress in the cracked zone drops to zero while the load is totally supported by the reinforcement. The stresses are then progressively transferred from reinforcement to concrete. This transition zone has an impact on the crack properties and is directly influenced by the reinforcement and concrete interface. At the cracked section all the tension force is carried by the steel reinforcement. The yields of steel produce crack mouth opening displacement (CMOD). The interfacial-failure in bond strength starts gradually through interfacial debonding, which develops forward until covering whole embedment length of the reinforcement in the concrete. Then the reinforcement starts in resisting the further forces by friction stresses which are generated through frictional sliding process. These friction stresses work as an interfacial-shear forces and aim to satisfy the balance with that further forces. Figure 1 shows the bond stress and tensile force distribution between two cracks. At bamboo reinforcement, the shrinkage of concrete is smaller than bamboo shrinkage. This causes less adhesion between bamboo and concrete. With some coating process, the shrinkage of the bamboo is reduced and then the friction is increased. The use of pegs along reinforcement also increases the mechanical interaction or bonding force and increase the beam capacity editor@iaeme.com

3 Crack Behavior Study of Bamboo Reinforced Concrete Beam with Additional Pegs in Reinforcing (a) (b) (c) (a) position of cracks, (b)bond force, (c) concrete stress (a) position of cracks, (b) bond force, (c) concrete stress Figure 1 Bamboo concrete slip There is no yield in bamboo reinforcement, but there is an elastic elongation of bamboo and slips or bond fracture between bamboo and concrete. Failure is accompanied by growing of cracks and spalling of concrete as shown in Figure 2 and Figure 3. (a) slip slip (b) (a) position of cracks, (b) bond force, (c) concrete stress Figure 2 Bamboo concrete slip (c) Figure 3 Spalling of concrete The failure of BRC members occurs due to weak bond between bamboo and concrete. Coatings such as water-based paints or bitumen were used to prevent the water ingress to bamboo reinforcement in concrete. Dewi [1,7], Javadian [8], and Muhtar [9] combined coating with surface treatment with coarse aggregate. Agarwal [10] made comparison among several adhesives available to measure their performance in improving the interfacial strength between the bamboo and concrete, the research suggests Sikadur 32 Gel as the best adhesive coatings. Terai [11] state that the behavior of pull-out test with bamboo is almost the same as editor@iaeme.com

4 Sri Murni Dewi, Devi Nuralinah, As ad Munawir and Ming Narto Wijaya the plain steel bar; however, the bond strength with bamboo was higher than the one with plain steel bar. It can be expected that the bond strength covering with full treatment shows the high value MPa. Slips or bond fracture of concrete depends on the concrete strength and a confined or unconfined of concrete along reinforcement. The CEB-FIP Model Code 1990 gives parameters for the extreme cases confined (i.e. ductile pull-out failure) and unconfined (i.e. brittle failure due to cover cracking induced by the radial tensile stress); see Table 1 and Figure 4. г Г max 1 Г f 2 3 s Figure 4 Bond slip diagram Table 1 Bond-slip model parameters Unconfined concrete Good bond conditions All other bond conditions Unconfined concrete Good bond conditions All other bond conditions S 1 [mm] S 2 [mm] S 3 [mm] Clear rib spacing Clear rib spacing max [Mpa] 2.0 f 1.0 f 0.45 f f f [Mpa] 0.15 max 0.15 max 0.40 max 0.40 max The use of pegs along reinforcement as slip stopper or slip connector benefit to increase the mechanical interaction or bonding force and decrease the slip displacement [9]. The fiber addition also benefits to reduce the crack width [12]. The mechanical interaction of pegs and concrete can be shown in Figure 5. (a) slip slip (b) (c) (a) position of cracks, (b)bond force, (c) concrete stress (a) position of cracks, (b) bond force, (c) concrete stress Figure 5 Pegs and reinforcement slip editor@iaeme.com

5 Crack Behavior Study of Bamboo Reinforced Concrete Beam with Additional Pegs in Reinforcing 2. MATERIALS AND METHODS The experiment program was designed to determine the effect of installing pegs on reinforcement to the capacity and crack behavior of bamboo reinforced concrete beam. Two types of pegs were use, wood pegs, and hose-clamp pegs. The variation of pegs distance was 6o mm and 120 mm. The specimen beam dimension was 180 mm x 280 mm x 1600 mm for beam with wood peg and 180 mm x 250 mm x 1600 mm for beam with hose clamp peg. The pegs mounted at a distance of mm as shown in Figure 6. The pegs of the hose clamps were attached to the bamboo reinforcement after the reinforcement is painted and covered in sand. The cap of hose clamp will hold and stop the slip movement between bamboo and concrete. Figure 6 Hose clamps pegs Another peg is a wooden peg sized 10 mm x 20 mm x 5 mm also mounted at a distance of mm as shown in Figure 7. To strengthen the pegs attachment, a wooden peg mounted on the bamboo reinforcement using wood glue before the bamboo reinforcement is covered with sand. Figure7 Wooden Pegs Figure 8 Experimental Test Setup The beam specimens comprised six type of beam, i.e. BHP (beam with hose clamps pegs only at the ends), BHP6 (beam with 60 mm distance of hose clamp pegs along reinforcement), BHP12 (beam with 120 mm distance hose clamp peg along bamboo reinforcement), BWP (beam with wooden peg only at the ends), BWP6 (beam with 60 mm editor@iaeme.com

6 Sri Murni Dewi, Devi Nuralinah, As ad Munawir and Ming Narto Wijaya distance wooden pegs along bamboo reinforcement) and BWP12 (beam with 120 mm distance wooden pegs along bamboo reinforcement). There is only one specimen for each BWP and available three specimens for each BHP. Four-point-bending system was applied using point load at mid span of beam under loadcontrol mechanism at increment of 500 kn until reaching failure. The experiment setup is shown in Figure RESULTS AND DISCUSSION The load deflection curve of beam 180 mm x 250 mm x1600 mm without peg, 120 mm pegs distance and 60 mm pegs distance shown in Figure 9, Figure 10, and Figure 11. Figure 9 Load deflection curve of BHP beam Figure 10 Load deflection curve of BHP6 beam Figure 11 Load deflection curve of BHP12 beam editor@iaeme.com

7 Crack Behavior Study of Bamboo Reinforced Concrete Beam with Additional Pegs in Reinforcing The load deflection curve of 180 mm x 280 mm x 1600 mm 180 mm x 280 mm x 1600 mm with wood pegs 120 mm and 160 mm pegs distance shown in Figure 12. Figure 12 Load deflection Curve of BWP beam The pattern of BHP beam crack is shown in Figure 13, Figure 14, and Figure 15. Figure 13 The crack pattern of BHP beam Figure 14 The crack pattern of BHP6 beam editor@iaeme.com

8 Sri Murni Dewi, Devi Nuralinah, As ad Munawir and Ming Narto Wijaya Figure 15 The crack pattern of BHP12 beam Installation of hose clamp pegs should increase the beam cracks strength from 25 kn to 30 kn. The 120 mm pegs distances increase the average ultimate strength from 50 kn to 70 kn, but the 6cm pegs distance decrease the ultimate strength. For wooden pegs, the pegs installations successfully, increase the ultimate strength but does not influence to the cracks strength. It is like hood that wooden pegs more flexible than hose clamp pegs. The average distance between 1 st crack and 2 nd crack was 250 mm, and the additional load was 5 kn. The average beam deflection at first crack was 2 mm. From moment-curvature analysis to the load deflection of beam with pegs, the crack load corresponding to 16 kn tensile loads or 120 MPa tensile stresses for each bar. With 250 mm crack distance, the maximum shear stress was 1.6 MPa. For beam without pegs, the crack load corresponding to 10.8 kn tensile loads or 90 MPa tensile stresses for each bar and 1 MPa shear stress. Then installation of hose clamp pegs increases the bond slip parameter from 1 MPa to 1.6 MPa. The actual tensile strength of bamboo is MPa. According to the previous research [7], without coating, the effective strength of bamboo reinforcement is MPa, and should increase until MPa after surface coating, with pegs adding the strength increase to MPa. 4. CONCLUSIONS The use of bamboo for environmentally friendly construction materials, more quickly implemented and added value in terms of cost and environmental sustainability is very interesting to further studied. The use of pegs along the beam is increase cracking and ultimate load capacity of the beam. For hose clamp pegs the 120 mm pegs distance reveals more ultimate load than 60 mm pegs distance. For wood pegs, the 6 cm pegs distance reveal maximum ultimate load. Coating surface and adds extra pegs increase effective bamboo reinforcement tensile stress from 45 MPa to 90 MPa. Installation of hose clamp pegs increase the bond slip parameter from 1 MPa to 1,6 MPa. The use of pegs on reinforcement like hooks on the steel reinforcement will be an opportunity to create a rigid beam-column connection. Another type of pegs was interesting for the next research editor@iaeme.com

9 Crack Behavior Study of Bamboo Reinforced Concrete Beam with Additional Pegs in Reinforcing REFERENCES [1] Watanabe A, Hitomi Y, Saeki E, Wada A and Fujimoto M, Properties of brace encased buckling-restraining concrete and steel tube. The 9th World Conference on Earthquake Engineering. Proceedings of, IV, 1989, [2] Dewi S. M and Wonlele T, Roof frame from bamboo concrete composite. Journal of Material Science and Engineering, B (1), no 1, Juni 2011, p [3] Dewi S.M, Bamboo use for earthquake resistance housing, The 2nd International Conference on Earthquake and Disaster Mitigation, Surabaya, [4] Nejadi S, Time-Dependent Cracking and Crack Control in Reinforced Concrete Structures, Thesis, School of Civil and Environmental Engineering the University of New South Wales, [5] Casanova L, Jason L and Davenne, Bond slip model for the simulation of reinforced concrete structures. Engineering Structures 39, 2012, [6] Pease B.J, Impudence of concrete cracking on ingress and reinforcement corrosion, Ph.D. Thesis Department of Civil Engineering, Technical University of Denmark, [7] Baky H. A, Ebead U.A and Neale K.W, Nonlinear micromechanics-based bond slip model for FRP/concrete interfaces. Engineering Structures, 39, 2012, [8] Dewi S.M and Nuralinah D, The recent research on bamboo reinforced concrete. MATEC Web of Conferences ISCEE, 103, 02001, [9] Javadian A, Wielopozki M, Smith I.F and Hebel D.E, Bond-behavior study of newly developed bamboo-composite reinforcement in concrete. Construction and Building Materials, 122, 2016, [10] Muhtar and Dewi S.M, Bond slip improvement of bamboo reinforcement in concrete beam using hose clamp. The 2 nd International Multidisciplinary Conference 2016, Indonesia. [11] Agarwal A, Nanda B and Maity D, Experimental investigation on chemically treated bamboo reinforced concrete beams and columns. Construction and Building Materials, 71, 2014, [12] Terai M and Minami K., Fracture behavior and mechanical properties of bamboo reinforced concrete members Japan Procedia Engineering 10, 2011, [13] Dewi S.M, Wijaya M.N and Naingolan C.R, The use of bamboo fiber in reinforced concrete beam to reduce crack. AIP Conference Proceedings 1887,020012, 2017, doi: / editor@iaeme.com