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Long term strength and durability evaluation of sisal fibre composites
Long term strength and durability evaluation of sisal fibre composites
Long term strength and durability evaluation of sisal fibre composites
Long term strength and durability evaluation of sisal fibre composites
Long term strength and durability evaluation of sisal fibre composites
Long term strength and durability evaluation of sisal fibre composites
Long term strength and durability evaluation of sisal fibre composites
Long term strength and durability evaluation of sisal fibre composites
Long term strength and durability evaluation of sisal fibre composites
Long term strength and durability evaluation of sisal fibre composites
Long term strength and durability evaluation of sisal fibre composites
Long term strength and durability evaluation of sisal fibre composites
Long term strength and durability evaluation of sisal fibre composites
Long term strength and durability evaluation of sisal fibre composites
Long term strength and durability evaluation of sisal fibre composites
Long term strength and durability evaluation of sisal fibre composites
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Long term strength and durability evaluation of sisal fibre composites

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  • 1. International Journal of Civil JOURNAL OF CIVIL ENGINEERING (Print), INTERNATIONAL Engineering and Technology (IJCIET), ISSN 0976 – 6308 AND ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME TECHNOLOGY (IJCIET)ISSN 0976 – 6308 (Print)ISSN 0976 – 6316(Online)Volume 4, Issue 1, January- February (2013), pp. 71-86 IJCIET© IAEME: www.iaeme.com/ijciet.aspJournal Impact Factor (2012): 3.1861 (Calculated by GISI)www.jifactor.com © IAEME LONG-TERM STRENGTH AND DURABILITY EVALUATION OF SISAL FIBRE COMPOSITES Part-I: CEMENT MORTAR COMPOSITES G.Ramakrishna*, T.Sundararajan Department of Civil Engineering Pondicherry Engineering College Pondicherry – 605 014 INDIA *Corresponding author; E-mail: ramakrishna_grk@rediffmail.com ABSTRACT In the first part of a two –part paper, the long-term strength and durability evaluation of sisal fibre cement mortar composites have been investigated. Strength characteristics of cement mortar composite (compressive, flexural, split-tensile strength) and that of composite slabs (flexural and impact strength) were determined at various ages (28-120 days) for 1:3 mix, at a constant flow value (110%) for various fibre contents (0.25%-2.0%, by wt. of cement). The durability of the composites was evaluated by two methods. It is found that the strength behaviour of the composites (i.e. compressive, flexural and split- tensile) are similar over the range of parameters and ages and that there is considerable improvement in the long- term strength. The two methods of evaluation of durability of the composites can be used to understand the interaction of the matrix and an alkaline medium considered. The above results are to serve as a reference to understand the role of a pozzolana used in cementitious mortar composites, being reported in a companion paper. Key words: Cement mortar Composite Strength, Durability, Impact Strength, Long-term studies, Sisal Fibres, I. INTRODUCTION Studies on natural fibre reinforced cement/cementitious composites and development of products for various applications in Civil Engineering, have the twin advantages of ensuring sustainable development and making available materials/ products at affordable 71
  • 2. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEMEcost. If the above advantages have to be actually realized, then, two inherent drawbacks(‘balling effect’ and ‘embrittlement’ of fibres) have to be addressed scientifically andcomprehensively. Gram [1] was the first to recognize the ‘embrittlement of fibres’ in analkaline medium and to identify the mechanisms and investigate various measures to improvethe durability of cement composites with sisal and coir fibres. Subsequently severalapproaches have been suggested and investigated [2-16]. From a comprehensive review ofliterature on the strength characteristics of natural fibre cement composites it is found thatlong-term studies on the strength behaviour of the above composites are rare [17]. Further,studies on the use of flyash in natural fibre composites and its influence on variouscharacteristics of composites is also rather rare [17] Hence, a, comprehensive and exhaustive investigations on the long-term strength,evaluation of durability and durability of sisal fibre cement/ cementitious composites wereundertaken. The first part of the investigation covering the long-term strength characteristicsand evaluation of durability of cement mortar composites is covered in this paper. The resultsfrom the first part of the investigations is expected to serve as a reference to understand therole of fly ash in influencing the various characteristics of sisal fibre cementitious mortarcomposites, which are reported in a companion paper (i.e. part-II of the paper)II. EXPERIMENTAL INVESTIGATION2.1 MATERIALS USED Ordinary Portland cement (OPC – 53 grade) conforming to IS: 12269 - 1987 [25];good quality river sand, whose gradation corresponds to Zone – II, as stipulated in IS: 383 –1997 [26], were used. Good quality potable water available in the campus was used both formixing and curing the mortar specimens. Sisal fibres are available abundantly in ‘fullyprocessed form’ in this part of the region. The salient properties of above materials are givenin Tables 1 to 3. Table 1: Physical Properties of Cement (OPC-53 grade) Sl. No. Property Value 1 Standard consistency (%) 29% 2 Initial setting time (min.) 55 min 3 Final setting time (min.) 175 min 4 Soundness 1mm 5 Specific gravity 3.14 6 Compressive strength @ i) 3 days 28 MPa ii) 7 days 38 MPa iii) 28 days 56.7 MPaNote: (i)Sand conforming to the gradation stipulated in I.S. specification for ‘standard sand’ was prepared inthe laboratory and used for determining the compressive strength of cement. (ii)The sample conforms to the requirements of 53 grade as stipulated in IS: 12269-1987 72
  • 3. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME Table 2: Physical Properties of Fine Aggregate Sl. Property Value/ No. description 1 Specific gravity 2.48 2 Water absorption 1.4% 3 Rodded bulk density 1.737 gm/cc 4 Fineness modulus 2.5 Note: Procedure is based on IS: 383 – 1997 [26] Table 3: Physical Properties of Sisal Fibres Sl. Fibre- Fibre Fibre Tensile Elongation Specific Elastic - No. type length diameter strength (%) gravity modulus (mm) (mm) (N/mm2) GPa 1. Sisal 180 -600 0.10– 0.50 31 – 221 14.8 1.4 7.832.2 PREPARATION AND TESTING OF MORTAR COMPOSITE Compressive strength, flexural strength and split-tensile strength of cement mortarspecimens and impact and flexural strength of cement mortar composite slabs of 1:3 mixwere determined at four ages (i.e.28, 56, 90 and 120 days of normal curing) and at six fibrecontents (i.e. ranging from 0% to 2.0%) and at a constant flow value (i.e.112.5%). Details ofthe workability studies on the various composites are reported elsewhere [18-20]. From the‘flow curves’ developed by the workability studies, the required water-binder (W/B) ratiowas selected for preparing the mortar, based on the constant flow value (i.e.112.5). Noadjustment was made for the water absorption-capacity of sisal fibres, as the fibres were pre-soaked (at least for 5 minutes) in fresh water and then used in the mortar for casting varioustest specimens. W/B ratio for each combination of mix for a constant flow value of 112.5% issummarized in Table 4. Altogether there were 7 combinations (1 combination with OPC; 6combinations with OPC + sisal fibre). Details of elements cast like size of specimen, numberof specimens, total number of specimens cast for each combination of mix etc. is given inTable 5, for evaluating the flexural strength of beam specimens of the mortar composites.After casting the mortar beam specimens, they were cured in water for the specified ages andat the end of the respective curing period, the specimens were first tested for their flexuralstrength as per IS 4031 (Part-8) [21]. Compressive strength of the specimens were determinedby using one of the fractured (broken) pieces of the beam specimens (after determining theirflexural strength) and testing them as per IS 4031-Part-8 [21]. Split- tensile strength ofspecimens were determined by using another fractured (broken) piece of the beam specimenand tested by a ‘novel method’ suggested by Hannant [22]. The slab specimens were testedby the projectile impact test for evaluating the impact strength characteristics [23]. Theusefulness of the above method has been established based on earlier investigations carriedout on a few natural fibre reinforced cement mortar composites and reported elsewhere [23].To evaluate quantitatively the improvement in the impact resistance characteristics ofcomposites, a simple parameter called, ‘residual impact strength (Irs )’ has been defined as 73
  • 4. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEMEgiven in eqn.(1), which can also be taken as a ‘measure of ductility’ of the compositeimparted by the fibres incorporated in to the matrix. Using the approach the performance of afew natural fibre composites has been evaluated and reported elsewhere [23]. Energy absorbed upto ultimate failureResidual impact strength ratio (Irs) = …(1) Energy absorbed at initiation of first crack Table 4: W/B Ratio of Mixes Considered for Strength Studies of Sisal Fibre Reinforced Mortar (1:3; flow value= 112.5%) Fibre Content 0 0.25% 0.5% 0.75% 1.0% 1.5% 2.0% Water/Cement 0.64 0.64 0.65 0.68 0.70 0.74 0.76 ratio Table 5: Details of Elements Cast for Strength and Durability Studies (1:3; @ 28, 56, 90, and 120 days)Sl. Type of No. of specimens for No. of Total no. Total no. ofNo. element strength studies specimens of specimens for the specimens cast durability for the for the study durability total A B C D study no. of Mixes (ie.-7)1. Flexural Beam (40x40x160mm) 3 3 3 3 - 12 842. Slab 2 2 2 2 2 10 70 (300x300x18mm) Note: (i) ‘A, B, C, D and E’ indicated in the column below ‘strength’ and ‘durability’ studies indicate the curing ages i.e. 28, 56 , 90 and 120 days, respectively . (ii) The slab specimens of durability studies were immersed in NaOH solution (0.1N; pH: 12.5) for 28 days, after 120 days of normal curing in water. Flexural strength of mortar slab specimens were determined by a four-point loadingsystem and using the 5kN capacity universal tensile testing machine available in the Dept. ofCivil Engineering. The usefulness of the above method has been established and reportedelsewhere [17, 24]. A computerized data-logging system was interfaced to the above test set-up for acquiring data and processing them, through a software exclusively developed for theabove purpose. For the above test, slab specimens of size 120x90x20 mm were cut andremoved from the fractured slab specimens obtained from the impact test of slab specimensof size 300x300x18 mm. The load versus deflection values were obtained through LVDT andlogged on to a computer and a plot of load vs. deflection obtained using the speciallydeveloped software, wherein, the load was measured at the loading position of the specimen 74
  • 5. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEMEused in the test. Along with the above plot, the maximum load and deflection at failure asdisplayed in the system were logged on to the computer. From the load –deflection curve,‘flexural toughness’ (FT) of the specimens were evaluated. The various strength testsconducted on the various specimens are shown in Fig.1 and 2. (a) A View of Flexural Testing Machine for Prism Specimens(b) Test Set –Up for Compressive (c) Test Set –Up for Split- Tensile Strength of Mortar Strength of Mortar Fig. 1 : Prism Specimens for Determining the Various Strength Characteristics 75
  • 6. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME Shown in (b) (a) Data Acquisition System (b)Experimental Set-Up Fig. 2: A View of Experimental Set-up for Flexure Test of Mortar Slab (broken)2.3 DURABILITY STUDIES ON SISAL FIBRE CEMENT COMPOSITES (with Data Acquisition system) Slab specimens of size 300 x 300 x 18 mm (1:3) were cast under identical conditionsas that of specimens for strength studies. After the specified period of normal curing, the slabspecimens were kept immersed in NaOH solution (prepared at 0.1N) for (another) 28 days.During the period of exposure in the above alkaline medium, pH of the medium wasmaintained constant at (about) 12.0. After 28 days of immersion in the above alkalinemedium, the slab specimens were tested for their impact and flexural strength. To evaluatethe durability of composites identical procedure and experimental set-up used for the case ofnormal-cured specimens were used. ‘Irs’ and ‘IT’ of composites before and after exposure in NaOH along with deviation inthe above values computed and expressed as a percentage of relative change in values withrespect to values obtained before exposure, were used to evaluate the durability of thecomposites. 76
  • 7. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEMEIII. RESULTS AND DISCUSSION3.1 COMPRESSIVE STRENGTH Compressive strength of cement mortar composites (1:3; Vf = 0.25% - 2.0%; @ 28,56, 90 and 120 days of normal curing) are given in Table 6. Based on the above results,following inferences are drawn: (i) Compressive strength of cement mortar composites increases, with increase in fibre content upto 0.5%, beyond which the strength decreases. The above phenomenon is found to be independent of age of the composite (i.e. from 28 to 120 days). (ii) Maximum strength is attained when the fibre content in the composite is 0.5%, for all the ages considered and that the above strength is 25 – 61% higher than the plain cement mortar strength (at the corresponding ages). (iii) Moreover, the maximum strength attained increases with increase in age and that there is about 44%, 104% and 112% increase in the maximum strength, at the ages of 56 days, 90 days and 120 days, respectively, over the 28 days strength of the cement mortar composite at 0.5% ( i.e.26 MPa). (iv) The maximum long – term strength - gain ratio of the composite is about 2.1 i.e. ratio of the compressive strength @ 120 days (i.e. long-term) to that @ 28 days (i.e. at ‘normal age’). Table 6: Compressive Strength of Sisal Fibre Cement Mortar Composites (1:3; constant flow value=112%; @ 28, 56, 90 & 120 days) Sl. Compressive Compressive strength (N/mm2) at fibre contents of No. Strength at the Age of 0% 0.25% 0.5% 0.75% 1.00% 1.5% 2.00% 1 28 days 19.5 23.0 26.0 22.5 20.0 12.0 9.0 2 56 days 30.0 32.5 37.5 33.0 28.0 22.5 19.0 3 90 days 33.0 49.0 53.0 44.5 36.0 30.5 25.0 4 120 days 44.0 52.0 55.0 50.0 41.0 35.0 31.03.2 FLEXURAL STRENGTH Flexural strength of cement mortar composites (1:3; Vf = 0.25% - 2.0%; at variousages 28 -120 days), are presented in Tables 7. Based on the analysis of the above resultsand comparing the compressive and flexural strength behaviour of the composites, followinginferences are drawn: (i) Flexural strength behaviour of cement mortar composites is similar to that of the compressive strength, within the range of fibre contents and ages considered. (ii) Flexural strength of cement mortar composites is also maximum when the fibre content is 0.5%, for all the ages considered and that the maximum strength is about 34-53% higher than the corresponding plain mortar strength, over the range of ages considered. 77
  • 8. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME (iii) The maximum flexural strength attained (i.e. @ Vf =0.5%) increases with increase in age and that there is about 16%, 91% and 120% increase in the strength, at the ages of 56 days, 90 days and 120 days, respectively, over the maximum strength of the composite (i.e. 4.5 MPa) at 28 days. (iv) The maximum long-term flexural strength ratio of the cement mortar composite is 2.2, which is nearly the same as that of the compressive strength - ratio of cement mortar composites under identical conditions. Table 7: Flexural Tensile Strength of Sisal Fibre Cement Mortar Composites (1:3; constant flow value=112%; @ 28, 56, 90 & 120 days) Sl. Flexural Tensile Flexural Tensile strength (N/mm2) at fibre contents of No. Strength at the Age of 0% 0.25% 0.5% 0.75% 1.00% 1.5% 2.00% 1 28 days 3.0 3.5 4.5 3.8 3.0 2.7 2.4 2 56 days 3.4 4.4 5.2 4.6 4.1 3.8 3.3 3 90 days 6.1 7.5 8.6 7.1 6.1 5.6 5.3 4 120 days 7.4 8.8 9.9 9.5 8.6 7.6 6.43.3 SPLIT –TENSILE STRENGTH Split - tensile strength of sisal fibre cement mortar composites (1:3; 28-120 days) arepresented in Tables 8. From the analysis of the above results and on comparing the abovestrength behaviour with that of compressive and flexural strengths, following salientinferences are drawn: (i) Split - tensile strength behaviour of cement mortar composites is similar to that of the compressive and flexural strengths, within the range of fibre contents and ages considered. (ii) Split-tensile strength of cement mortar composites is also maximum when the fibre content is 0.5%, for all the ages considered and that the maximum strength is generally about 20 - 30% higher than the corresponding plain mortar strength, over the range of ages considered. (iii) The maximum split – tensile strength increases, with age and that the increase is about 28%,40% and 54%, over the maximum strength of the composite (i.e.5.0 MPa), at 28 days. (iv) The maximum long – term split – tensile strength - ratio of cement mortar composite is 1.6, which is slightly less than that of cement mortar composites in compression and flexure, under identical conditions. (v) Ratio of the maximum split-tensile strength to the maximum compressive strength of the composite under identical conditions, and for various ages, is in the range of 13 to 19%, with an average value of 15.8%. The above (average) ratio indicates good performance of the composite, under direct tension. 78
  • 9. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME Table 8: Split –Tensile Strength of Sisal Fibre Cement Mortar Composites (1:3; constant flow value=112%; @ 28, 56, 90 & 120 days) Sl. Split- Tensile Strength Split - Tensile strength (N/mm2) at fibre contents of No. at the Age of 0% 0.25% 0.5% 0.75% 1.00% 1.5% 2.00% 1 28 days 3.8 4.8 5.0 4.1 3.5 3.0 2.5 2 56 days 5.7 6.1 6.4 5.5 4.8 4.0 3.9 3 90 days 5.7 6.6 7.0 6.5 5.9 4.9 3.8 4 120 days 6.3 7.2 7.7 7.4 6.6 5.7 4.93.4 IMPACT STRENGTH OF CEMENT MORTAR COMPOSITE SLABS3.4.1 NORMAL –AGE BEHAVIOUR (@28 DAYS) Impact strength characteristics of cement mortar slabs and cement-mortar compositeslabs (@ 28 days) are presented in Table 9. It can be seen from the above results, that theenergy absorbed after initiation of first crack and upto failure is only nominal (i.e. from 9.25to 10.0 Joules only). Hence, the inherent ductility of the cement mortar slab, which isreflected in ‘Irs’ value is very less and is equal to 1.08. The ‘above value is taken as thereference’, to obtain the relative performance of various mortar slabs / composite slabs. As the fibre content in the cement mortar slab increases, energy required to cause‘initiation of crack’ and ‘final failure’ goes on gently increasing and that energy absorbed ismaximum @ 2% fibre content, i.e.18.9 and 35.5 Joules, respectively. This shows the ductilityimposed by the fibres on the composite. In terms of energy absorbed there is an improvementof 2.04 and 3.56 times than the corresponding energy required for the ‘reference mortar slab’. Residual impact strength ratio (Irs) which is a measure of ductility inherent in thematerial, increases gently with increase in fibre content for the cement mortar composites andis in the range of 1.27 to 1.88 for the above composite, within the range of fibre contentsconsidered. However, Irs of cement mortar composites, relative to that of the cement mortarslab (i.e. reference, with Vf = 0%), denoted by ‘Irs’ , ranges from 1.18 to 1.74. This gives therange of ductility improvement that could be achieved due to incorporation of sisal fibres(i.e.0.25% to 2.0% in this study), in cement mortar slabs.3.4.2 LATER - AGE BEHAVIOUR (i.e.. 56 - 120 DAYS) Impact strength characteristics of cement-mortar slabs at later-ages (i.e. 56-120 days)are given in Table 9. Based on critical analysis of the above results and on comparing themwith the early-age behaviour, following inferences are presented: (i) Later-age behaviour of cement mortar slabs are similar to that of early-age behaviour, with respect to the energy absorbed. However, increase in energy absorbed is substantial upto 90 days and that the maximum value is reached @ 120 days, within the range of ages considered. 79
  • 10. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME (ii) Maximum energy absorbed for initiation of crack and at failure @ 120 days are,13.8 and 18.0 Joules respectively, @ 120 days, which is about 1.5 and 1.8 times over the corresponding values of the reference mortar slab. (iii) In terms of Irs, there is only a gentle variation over the various ages considered and lies with in a narrow range of 1.20 to 1.30. However, ‘Irs’ of the composites is in the range of 1.11 to 1.20, (i.e.about 20%) indicating only a marginal improvement in the ductility of the composite slabs, over the early-age behavoiur, within the range of later-ages considered. Table 9: Impact Strength of Sisal Fibre Cement Mortar Composites (1:3; constant flow value=112%; @ 28, 56, 90 & 120 days)Sl. Fibre Impact Strength/ Residual Impact strength Ratio atNo. content (%) @28 days 56 days 90 days @120 days A B C A B C A B C A B C 1 0 9.25 10 1.08 12.5 15 1.20 13.49 17.0 1.26 13.84 18.0 1.22 2 0.25 11.02 14 1.27 15.4 18.8 1.22 16.01 20.5 1.28 16.91 22.5 1.70 3 0.50 13.43 18 1.34 16.01 24.5 1.53 17.18 27.5 1.60 17.35 29.5 2.0 4 0.75 16.19 23 1.42 16.38 29.0 1.77 17.37 32.5 1.87 17.76 35 2.25 5 1.00 17.41 27 1.55 16.66 33.50 2.01 17.61 37 2.10 18.18 40.0 2.53 6 1.50 18.00 31.5 1.75 17.51 38.0 2.17 18.69 41.5 2.22 19.39 45.0 2.68 7 2.00 18.88 35.5 1.88 18.55 42.5 2.29 19.23 45.2 2.35 21.34 54.0 2.883.5 FLEXURAL STRENGTH OF CEMENT MORTAR COMPOSITES SLABS Results of flexural strength evaluated by the four - point loading method using thebroken pieces after conducting the impact test , are given in Table 10, for various ages andother parameters considered. Based on the above and also comparing the flexural strength ofthe composites (i.e. standard specimens), following inferences are drawn: (i) Behaviour of composite mortar slabs are generally similar to that of flexural strength of standard specimens of mortar and composites, within the range of parameters and ages considered. (ii) Flexural strength of reference mortar slabs (CM 1:3, fibre content = fly ash, content= 0%) is found to be 3.93 MPa, (at 28 days), which is comparable to the strength of reference mortar specimens under flexure. However, the strengths are always lower, at all later-ages. Moreover, the later-age strength of slabs (@120 days) are about 30% lower than the strength of flexural specimens. 80
  • 11. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME (iii) Flexural strength of cement mortar composite slabs are maximum at the fibre content of 0.5% and at all ages, which is also similar to the flexural behaviour of composite specimens (evaluated by the standard procedure). However, the maximum strength obtained by the composite slabs are always less than the maximum strength attained by the specimens (in flexure) at all ages considered. The above phenomenon may be due to the ‘residual stress’ present in the slab specimens due to the impact test, conducted earlier.The primary objective of the above test is to obtain the ‘reference data’ for determining the‘flexural toughness factor’ (IT) of the composite slabs after exposing them in NaOH and,hence, to evaluate the ‘durability of the composite’. Table 10: Flexural Strength of Sisal Fibre Cement Mortar Composite SlabsSl. Flexural Strength at Flexural strength (N/mm2) at fibre contents ofNo. the Age of 0% 0.25% 0.5% 0.75% 1.00% 1.5% 2.00% 1 28 days 3.93 4.11 3.98 3.41 3.08 2.93 2.29 2 56 days 4.55 4.67 4.77 4.47 4.10 3.57 2.40 3 90 days 4.80 5.10 5.76 5.55 5.25 4.32 3.97 4 120 days 5.26 5.40 5.41 5.34 5.00 4.73 4.403.6 DURABILITY OF SISAL FIBRE CEMENT MORTAR COMPOSITE SLABS3.6.1 EVALUATION OF DURABILITY BASED ON ‘IRS’ Impact strength of cement mortar slabs, cement mortar composite slabs, before andafter exposing them in NaOH medium, are given in Table 11, for various fibre contents.From a critical evaluation of the above experimental data, following observations areobtained:(i) ‘Irs’ values of cement mortar composite slabs increases with increase in fibre content, after exposure in the alkaline medium, when compared to the Irs value before exposure and it is found to be independent of the fibre content. ‘Irs’ values of the above composite slabs after exposure have the same trend as that of slabs before exposure in the alkaline medium and that it is maximum when the fibre content is maximum i.e. 2.0% in the cement mortar composite slabs.(ii) A closer look at the deviation in Irs values above results presents an interesting scenario, i.e. (i) The deviation in Irs values of all plain mortar slabs, are all negative, indicating nearly failure of matrix, due to exposure in the alkaline medium; (ii) the deviation in ‘Irs’ values of all composite mortar slabs are all positive as ‘Irs’ values of composite slabs after exposure are higher than the corresponding values before exposure. 81
  • 12. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEMETable 11 : Impact Strength of Sisal Fibre Cement Mortar Composite Slabs Before and After Exposure in NaOH (1:3; Constant flow value =112%; r=200) Sl. Fibre Impact Strength/ Residual Impact strength Ratio Deviation in No. content Before Exposure After Exposure Irs (%) A B C A B C 1 0 13.84 18.0 1.30 8.91 10.89 1.22 -6.15 2 0.25 16.91 22.5 1.33 9.9 16.83 1.70 +27.81 3 0.50 17.35 29.5 1.7 10.89 21.78 2.0 +22.35 4 0.75 17.76 35 1.97 11.88 26.73 2.25 +14.21 5 1.00 18.18 40.0 2.20 12.87 32.67 2.53 +20.00 6 1.50 19.39 45.0 2.32 15.84 42.57 2.68 +18.96 7 2.00 21.34 54.0 2.53 16.83 48.51 2.88 +13.83 Note: (i) Energy for one blow = 0.99J (Height of fall = 21cm) (ii) A- Impact strength at initiation of crack (in Joules) B – Impact strength at final crack (in Joules) C- Residual impact strength (Irs)3.6.2 EVALUATION OF DURABILITY BASED IN FLEXURAL TOUGHNESS INDEX (IT) Flexural toughness of cement mortar slabs, cement mortar composite slabs, beforeand after exposure in NaOH medium are presented in Tables 12, for various fibre contents.From a closer look of the above, it is seen that IT values of various mortars / compositesexhibit the same trend as that of ‘Irs’ values, with respect to the range of parametersconsidered. Table 12 : Flexural Toughness Index of Sisal Fibre Cement Mortar Composite Slabs (1:3; Constant flow value = 112% ; r = 200 ; @ 120 days) Sl. Fibre Toughness Energy/Toughness index = {A2/(A1+A2)} Deviation in No. content IT (%) Before Exposure After Exposure A B C A B C 1 0 1322 700 0.346 1006.5 368.5 0.268 -22.54 2 0.25 1557 432.5 0.217 790.8 701.2 0.470 +116.58 3 0.50 998.5 434 0.302 198.6 846.7 0.810 +168.21 4 0.75 1361 2388.4 0.637 629.5 1887.5 0.750 +17.73 5 1.00 1319.5 471.2 0.263 848.1 498.1 0.370 +40.68 6 1.50 2413.8 1788 0.425 885.4 2392.0 0.730 +71.76 7 2.00 1347 1846 0.578 325.0 1084.0 0.770 +33.21Note: (i (A) – Area of the load-displacement diagram upto the pre-cracking stage- (A1) (B)- Area of the load-displacement diagram after the post-cracking stage-(A2) (C)- Flexural toughness index –( IT )= {A2/ (A1+A2)} 82
  • 13. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEMEIV. CONCLUSIONS4.1 STRENGTH BEHAVIOUR OF CEMENT MORTAR COMPOSITES (i) Compressive, flexural and split-tensile strength behaviour of sisal fibre cement mortar composites (1:3) are similar over the range of parameters and ages (normal age i.e. at 28 days, and at later – ages upto 120 days), considered. All the above strengths attain the maximum at identical fibre content in the mortar composite (i.e. sisal fibre content = 0.50%). (ii) Maximum compressive strength attained by the cement mortar composite is about 26 MPa [@ sisal fibre content (Vf) = 0.5%), at the normal – age], which is about 25 – 61%, higher than the plain cement mortar strength, for the range of ages considered. The maximum long-term strength-gain ratio of the cement mortar composite (i.e. ratio of compressive strength @ 120 days to that at normal age) is about 2.1. (iii)Maximum flexural strength attained by the cement mortar composite is 4.5 MPa (at Vf = 0.5), at the normal – age, which is about 30 – 50% higher than the reference mortar strength and for the range of ages considered. It is found that the long – term (maximum) flexural strength - ratio is nearly the same as that of the compressive strength - ratio. (iv) Maximum split – tensile strength attained by the cement mortar composite is 5.0 MPa (@ Vf =0.5, at the normal – age), which is about 20 – 30% higher than the reference mortar strength and for the range of ages, considered. It is found that the long- term (maximum) split- tensile strength ratio is about 1.6, which is slightly less than the other two strengths considered.4.2 IMPACT STRENGTH OF CEMENT MORTAR COMPOSITES (i) Residual impact strength ratio (Irs) which is measure of ductility inherent in the material ranges from 1.18 to 1.74, for the cement mortar composite slabs relative to that of the reference cement mortar slab, at normal-age and the range of sisal fibre contents considered. (ii) There is only a marginal improvement in the ductility (as measured by Irs) of the cement mortar composite slabs, over the early – age behaviour, within the range of later – ages considered.4.3 FLEXURAL STRENGTH OF CEMENT MORTAR COMPOSITES 1. Flexural strength behaviour of composite mortar slabs are generally similar to that of standard specimens (of mortar and composites), within the range of parameters and ages considered. 2. However, the maximum strength obtained by the composite slabs are always less ( by 30% - average) than that attained by the specimens (under flexure), at all ages considered, which may be attributed to the ‘residual stress’ present in the slab specimens by virtue of the earlier impact load subjected on them. 83
  • 14. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME4.4 DURABILITY OF SISAL FIBRE CEMENT MORTAR COMPOSITES (i) Irs and IT values could reflect the changes in the strength due to the interaction between the matrix and the medium considered (i.e. NaOH) and hence can be used with confidence to evaluate the durability of the mortar composites.V. ACKNOWLEDGEMENT This work reported herein forms a part of comprehensive investigations on therheology, strength and durability characteristics of sisal fibre cement and cementitiouscomposites, carried out by the authors in the Dept. of Civil Engg., Pondicherry EngineeringCollege, Pondicherry , India. The kind support and co-operation extended by the Principal,and the Head of Civil Engg. Dept., PEC , in all the endeavors of the authors is recorded witha deep sense of gratitude. The financial assistance received from Dept. of Science andTechnology, (DST), Govt. of India, has greatly helped to carry out the experimentalinvestigations reported in this paper, which is gratefully acknowledgedREFERENCES(1) Gram, H - E., ‘Durability of Natural Fibres in Concrete’, Report No 1, 1983, Swedish Cement And Concrete Research Institute, Stockholm, ISSN 0346-6906, 255pp.(2) Castro, J. Naaman, A.E., ‘Cement Mortar Reinforced With Natural Fibres,’ Jl. of Ferrocement, Vol,11, No.4, Oct. 1981, pp. 285-301.(3) Ramaswamy, H.S., Ahuja, B.M., Krishnamoorthy, S., ‘Behaviour of Concrete Reinforced With Jute, Coir And Bamboo Fibres,’ The Intl. Jl. of Cement Compotes and Light Weight Concrte, 1983. pp.3-12.(4) Toledo Filho, R.D., Ghavami, K., England, G.L., Scrivener, K., ‘Development of Vegetable Fibre-Mortar Composites of Improved Workability’, Cement & Concrete Composites, Vol.25, 2003, pp.185-196.(5) Berhance, Z., ‘Performance of Natural Fibre Reinforced Mortar Roofing Tiles’, Materials and Structures, Vol.27, 1994, pp.347-352.(6) Canovas, M.R., Selva, N.H., Kawiche, G.M. ‘New Economical Solutions For Improvement of Durability of Portland Cement Mortar Reinforced With Sisal Fibres’, Materials and Structures, Vol.25, 1992, pp. 417-422.(7) Gram.H.E. and Nimityoungskul.P, Durability of natural fibres in cement-based roofing sheets, Proc. of the Symp. on Building Materials for Low-income Housing: Asia and Pacific Region, Bangkok, Thailand, Jan.20-26,1987, Oxford & IBH Publ.Co.(P) Ltd., NewDelhi,pp.328-334.(8) John.V.M, Agopyan.V. and Derolle.A., Durability of blast furnace slag-based cement mortar reinforced with coir fibres, Proc. of the Second Intl. Symp. on Vegetable Plants and their Fibres as Building Materials, Salvador, Brazil, Sep.17-21 , 1990, Sobral.H.S (Ed.).,Chapman & Hall, London, pp.87-97.(9) Canovas, M.E., Kawiche, G.M., Selva, N.H., ‘Possible Ways of Preventing Deterioration of Vegetable Fibres In Cement Mortars’ Proc. of Second Intl. Symp. of RILEM on Vegetable Plants and their Fibres As Building Materials Sobral, H.S. (Ed.), Salvador, Brazil , Sep. 17-21, 1990, Chapman & Hall, London, pp. 120-129 84
  • 15. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME(10) Oliveria, M.J., Agopyan, V., ‘Effect of Simple Treatments of Malva Fibres for the Reinforcement of Portland Cement Mortar, Proc. of Fourth Intl. Symp. on RILEM Fibre Reinforced Cement and Concrete, Jul. 20-23, 1992, Swamy R.N. (Ed.), E & FN SPON, London, pp 1073 – 1079.(11) Gram, H.E., ‘Durability Studies of Natural Organic Fibres in Concrete Mortar or Cement,’ RILEM Symposium – FRC 86: Development In Fibre Reinforced Cement And Concrete, Swamy, R.N. And Others (Eds.) Sheffield, England, Jul. 13-17, 1986, Vol. II, Paper No. 7.1.(12) DelvastoS., Botache,C.A., Alban, F., Gutierrez, R.M., Perdomo,F., Segovia, F., Amigo,V’., ‘Effect of Fique Fiber Surface Chemical Treatments on the Physical and Mechanical Properties of the Fiber Subjected to Aggressive Mediums’, Brazil NOCMAT 2004, Pirassununga,SP,Brazil, Oct.29 – Nov 3, 2004, pp. 54-163.(13) Singh, S.M., ‘Studies on the Durability of Plant Fibres Reinforced Concrete Products’, Joint Symposium RILEM / CIB/ NCCL., on Use of Vegetable Plants and Fibres as Building Materials, Baghdad, Oct.1986, pp. C- 127 to C- 138.(14) Ramakrishna, G., Sundararajan , T., ‘Effect of a Few Pozzolanic Materials on The Strength of Treated/Untreated Sisal Fibre Reinforced Concrete’, Natl. Sem. on Concrete Technology For 21st Century, Feb. 9 -10, 2001, Annamalainagar, India, pp.79 -85.(15) Ramakrishna, G., Sundararajan,T., ‘Effect of Yeast – Blended Water on The Workability and Strength Characteristics of Sisal Fibre Reinforced Concrete’, Natl. Sem. on Advances in Construction Materials, Feb. 14 – 15, 2003, Ahmedabad, India, pp.201-208.(16) Ramskrishna, G. Sundararajan, T., ‘Effect of Yeast – Blended Water on Some Physical and Strength Characteristics of San Fibre Reinforced Concrete’, Natl. Conf. on Advances in Concrete Technology, Sep. 21 – 22 , 2000, Patiala, India, pp.28 – 39.(17) Ramskrishna, G. Sundararajan, T., ‘Rheological, Strength and Durability Characteristics of Sisal Fibre Reinforced Cementitious Composites’, Ph.D Thesis Submitted to the Pondicherry University, Pondicherry, India, Apr.2005 (Degree awarded in Aug.2005), 389pp.(18) Ramakrishna, G., Sundararajan , T., ‘Influence of Water-Binder Ratio and Fibre Content on the Workability and Rheological Characteristics of Sisal Fibre Cement Mortar Composites’, (unpublished).(19) Ramakrishna, G., Sundararajan , T., ‘Influence of Water-Binder Ratio and Fibre Content on the Workability and Rheological Characteristics of Sisal Fibre Cementitious Mortar Composites’, (unpublished).(20) Ramakrishna, G., Sundararajan , T., ‘Influence of Fibre Content and Aspect Ratio of Sisal fibres on the Workability and Rheological Characteristics of Cement Mortar Composites’, Journal of Structural Engineering,(accepted for publication).(21) IS: 4031 (Part 8) – 2000, ‘Method of Tests for Hydraulic Cement & Part 8: Determination of Transverse and, Compressive Strength of Plastic Mortar Using Prism’, BIS , India(22) Hannant, D.J. ‘The Tensile Strength of Concrete: A Review Paper’, The Structural Engineer, Vol. 50, No.7, July 1972, pp. 253 – 258.(23) Ramakrishna, G., Sundararajan , T., ‘Impact Strength of a Few Natural Fibre Reinforced Cement Mortar Slabs: A Comparative Study’, Cement & Concrete Composites, Vol.27, No.5.2005, pp.554-564. 85
  • 16. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME(24) Ramakrishna, G., Sundararajan , T., ‘New methods of testing for studying the rheology and strength of low modulus fibre reinforced cement/cementitious mortar composites’, (unpublished).(25) IS: 12269 – 199, ‘Specification for 53 Grade Ordinary Portland Cement’, BIS, India(26) IS: 383- 1997, ‘Specification for Coarse and Fine Aggragates from Natural Sources for Concrete’, BIS, India.(27)M. Vijaya Sekhar Reddy, Dr.I.V. Ramana Reddy and N.Krishna Murthy, “Durability Of Standard Concrete Incorporating Supplementary Cementing Materials Using Rapid Chloride Permeability Test” International Journal of Civil Engineering & Technology (IJCIET), Volume 3, Issue 2, 2012, pp. 373 - 379, Published by IAEME.(28)Dr. Prahallada. M.C., Dr. Shanthappa B.C. and Dr. Prakash. K.B., “Effect Of Redmud On The Properties Of Waste Plastic Fibre Reinforced Concrete An Experimental Investigation” International Journal of Civil Engineering & Technology (IJCIET), Volume 2, Issue 1, 2011, pp. 25 - 34, Published by IAEME.(29)N.Ganesan, Bharati Raj, A.P.Shashikala and Nandini S.Nair, “Effect Of Steel Fibres On The Strength And Behaviour Of Self Compacting Rubberised Concrete” International Journal of Civil Engineering & Technology (IJCIET), Volume 3, Issue 2, 2012, pp. 94 - 107, Published by IAEME. 86

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