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Frontiers of Structural and Civil Engineering

Front. Struct. Civ. Eng.    2018, Vol. 12 Issue (4) : 454-460     https://doi.org/10.1007/s11709-017-0454-2
Research Article |
Effect of embedment length of untreated natural fibres on the bond behaviour in cement mortar
Gudimella RAMAKRISHNA(), Sriraman PRIYADHARSHINI
Department of Civil Engineering, Pondicherry Engineering College, Puducherry 605014, India
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Abstract

The present investigation is focused on studying the effects of various matrices with 1:3, 1:4 and 1:5 mortars and fibre types of sisal and coir on the bond behavior at various ages of curing, i.e., 24 h, 3 d, 7 d and 28 d. The other parameters included in the investigation are water/cement (w/c) ratio, sand gradation and embedment length of fibres. In addition, the type of failure of sisal and coir fibres for different mixes of mortars at various curing ages is also reported. From the results, it is seen that the bond strength is improving with respect to age of curing in case of sisal fibres, but decreases in case of coir fibres. The failure of fibres due to fibre fracture is observed in sisal fibres and fibre pullout is observed in coir fibres. The other varying parameters such as mortar mixes, sand gradation, w/c ratio and embedded length also showed significant effect on bond behaviour of sisal and coir fibre with the cement mortar mixes.

Keywords bond strength      cement mortar      natural fibre      pullout test      type of failure     
Corresponding Authors: Gudimella RAMAKRISHNA   
Online First Date: 09 January 2018    Issue Date: 20 November 2018
 Cite this article:   
Gudimella RAMAKRISHNA,Sriraman PRIYADHARSHINI. Effect of embedment length of untreated natural fibres on the bond behaviour in cement mortar[J]. Front. Struct. Civ. Eng., 2018, 12(4): 454-460.
 URL:  
http://journal.hep.com.cn/fsce/EN/10.1007/s11709-017-0454-2
http://journal.hep.com.cn/fsce/EN/Y2018/V12/I4/454
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Gudimella RAMAKRISHNA
Sriraman PRIYADHARSHINI
Sl.No. property value IS 12269-1987 requirements
1 standard consistency (%) 29 -
2 initial setting time (min) 55 30 (min)
3 final setting time (min) 175 600 (max)
4 soundness (mm) 1 10 (max)
5 specific gravity 3.14 -
6 compressive strength (MPa)
i.3 d
ii.7 d
iii.28 d
28
38.5
56.7
27 (min)
37 (min)
53 (min)
Tab.1  Physical properties of OPC-53 grade cement
Sl.No. property value
1 specific gravity (no unit) 2.48
2 water absorption (%) 1.4
3 bulk density (gm/cc) 1.74
4 fineness modulus 2.5
Tab.2  Physical properties of fine aggregate
Fig.1  Graphical reprasentation of pull-out test setup
Sl.No. 1 2 3 4 5 6
gauge length (mm) 30 40 50 60 70 80
diameter (mm) 0.15 0.13 0.12 0.13 0.15 0.13
failure load (N) 27.4 16.9 13.8 10.1 10 6.1
tensile strength (N/mm2) 1550.52 1273.23 1054.55 760.13 565.88 459.81
elongation (%) 7.33 7.25 4.4 3.33 3.15 2.25
Tab.3  Tensile strength and percentage elongation of untreated sisal fibre for various gauge lengths
Sl.No. 1 2 3 4 5 6
gauge length (mm) 30 40 50 60 70 80
diameter (mm) 0.52 0.37 0.39 0.33 0.37 0.44
failure load (N) 7.4 7 16.2 13.2 18.1 31.5
tensile strength (N/mm2) 34.84 55.1 107.61 144.33 168.33 207.16
elongation (%) 11.3 16.25 28 29.2 32.8 35
Tab.4  Tensile strength and percentage elongation of untreated coir fibre for various gauge lengths
Fig.2  Bond strength vs. age of curing for various mortar mixes and EL for sisal fibres at water/cement (w/c) ratio of 0.5
Sl.No. EL (mm) age of curing (d) type of fibre failure for various mortar mixes
1:3 1:4 1:5
1 25 1 pullout pullout pullout
3 pullout pullout pullout
7 fracture pullout pullout
28 fracture fracture fracture
2 40 1 fracture fracture pullout
3 fracture fracture pullout
7 fracture fracture fracture
28 fracture fracture fracture
3 50 1 fracture fracture fracture
3 fracture fracture fracture
7 fracture fracture fracture
28 fracture fracture fracture
Tab.5  Type of failure of sisal fibres embedded in various cement mortar mixes at w/c ratio of 0.5
Fig.3  Bond strength vs. age of curing for various mortar mixes and EL for coir fibres at w/c ratio of 0.5
Sl.No. EL (mm) age of curing (d) type of fibre failure for various mortar mixes
1:3 1:4 1:5
?1 ?25 1 pullout pullout pullout
3 pullout pullout pullout
7 fracture pullout pullout
28 fracture pullout pullout
2 40 1 fracture pullout pullout
3 fracture pullout pullout
7 fracture pullout pullout
28 fracture pullout pullout
?3 50 1 pullout fracture pullout
3 pullout fracture pullout
7 fracture fracture fracture
28 fracture fracture fracture
Tab.6  Type of failure of coir fibres embedded in various cement mortar mixes at w/c ratio of 0.5
Fig.4  Gradation curve for different zones of sand
Fig.5  Bond strength vs. age of curing for different gradation of sand (1:3 mix; w/c ratio= 0.5; EL = 50 mm)
Fig.6  Bond strength vs. w/c ratio at various ages of curing (1:3 mix; EL = 50 mm)
type of mortar mix bond strength (MPa) at 28 d
sisal fibre coir fibre
1:3 0.37 0.12
1:4 0.19 0.09
1:5 0.18 0.11
Tab.7  The bond strengths obtained at 28 d
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