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Study on the reinforced manhole cover slab using coconut shell aggregate concrete
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 14 (2019) 386–394
www.materialstoday.com/proceedings
ICRAMC_2018
Study on the reinforced manhole cover slab using coconut shell aggregate concrete S. Soumyaa*, G. Pennarasia and K. Gunasekarana a
Department of Civil Engineering, Faculty of Engineering and Technology SRM University, Kattankulathur-603 203, Tamil Nadu, India.
Abstract In this study, two sets of manhole cover slabs were cast; one set with conventional concrete and the other set with coconut shell aggregate concrete. In both the cases, in one set 10 mm steel reinforcements were used and in the other sets 12 mm steel reinforcements were used. These manhole covers were produced and tested as per IS 12592: 2002. In both the concrete, along with conventional materials and coconut shell, steel fibers and micro silica were used to reach the specification required for the manhole cover slab. As per IS 12592:2002, a size of 600 × 600 × 100 mm and light duty grade of manhole cover slab were selected and studied. Test parameters such as workability of mixes, density of mixes, settlement limits at test load, crack formation, ultimate load and settlements at ultimate load results were discussed and presented. It is observed that the settlement at the time of test load on both conventional and coconut shell aggregate concrete manhole cover slabs were well within the limit specified by IS 12592: 2002. In both the cases, there was no formation of cracks at the time of sustaining test load as per IS 12592:2002. Load factors against ultimate failure were more than 4 in all the cases and hence, coconut shell aggregate concrete can be used for the production of manhole cover slabs. Test results and performance of coconut shell aggregate concrete manhole cover slabs encourage the use of coconut shell as an aggregate as the replacement of conventional aggregate in the production of manhole covers. © 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of 2nd International Conference On Recent Advances In Material Chemistry. Keywords: Coconut shell; Aggregate; Manhole cover; Application.
* Corresponding author. Tel.: +91-8220894366; fax: +91-44-27453903. E-mail address: [email protected]; [email protected] 2214-7853 © 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of 2nd International Conference On Recent Advances In Material Chemistry.
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1. Introduction manufacture the concrete simply exist at any place and at any instance; only least time is required for groundwork; it is achievable to make both customary and unbalanced shapes; it is an exceptional material which can admit mostly any material substitution for its customary materials. Consequently there are numerous researches all over the world taking place to substitute its major ingredients by the wastes produced from various sources such as domestic, industrials, agricultural etc., [1-10]. Coconut shell (CS) is one of the agricultural wastes which is used as a coarse aggregate and made usual in the production of coconut shell aggregate concrete (CSAC) by a researcher almost 10 years back [11] and chased by many researchers in the most recent years as well [12-26]. Most of the research results on CS based concrete have not only given confidence to use in the field applications, but its behavior was also equivalent to the customary concrete as well. Previously a study was made and manufactured a kind of CSAC pipe as a field application [27]. Thus, authors attempted a different application of CSAC in to the study on the reinforced manhole cover slab. 2. Coconut shell as an aggregate Adequate debate concerning the availability of CS around the earth and also in and around the local region was prepared and available elsewhere [20-26]. Similarly, how to practice the CS as an aggregate since its raw state and more or less all the essential properties of CS such as physical, chemical and mechanical, how to use the CS for the manufacture of CSAC etc, were published elsewhere [20-26]. Thus, the remarkable properties such as water absorption and specific gravity are revived at this juncture for the benefit of the community who are referring to this article. The CS used in this study had 4.40 % moisture content and absorbed 24.25 % water. Also the specific gravity ranged from 1.10 to 1.25 and the apparent specific gravity ranged from 1.40 to 1.55. Because of its less value of specific gravity while compared to customary aggregates, the concrete made using CS in CSAC possibly will get in to the group of a special concrete called lightweight concrete (LWC). Fig.1 illustrates the crushed CS after saturated surface dry (SSD) condition before it is used in the production of CSAC mixes.
Fig. 1 Ready to use CS for the production of CSAC mix
3. Manhole cover slab The manhole shall be rectangular, circular or square in plan. Manhole of other shapes such as hexagonal or octagonal shapes may also be recommended. The dimensions of these special shapes shall be such that a square or circle drawn circumscribing the extreme outer edges of the manhole cover slab confirming to the dimensions specified for square manhole and dimensions frame for cover slab as given in Table 1 and Table 2 are respectively as per IS 12592: 2002 [28].
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Soumya et al. / Materials Today: Proceedings 14 (2019) 386–394 Table 1 Grades and types Grade
Grade
Type / Shape of cover
designation Light Duty
LD-2.5
Rectangular, Square, Circular
Medium Duty
MD-10
Rectangular, Circular
Heavy Duty
HD-20
Extra Duty
EHD-35
Rectangular,(Scrapper Manhole), Square, Circular and Lamp hole Rectangular,(Scrapper Manhole), Square, Circular
Table 2 Dimensions of frame Grade Designation LD-2.5 LD-2.5 LD-2.5 MD-10 MD-10 HD-20 HD-20 HD-20 EHD-35 EHD-35 EHD-35
Description Light duty Rectangular Light duty Square Light duty Circular Medium duty Rectangular Medium duty Circular Heavy duty Square Heavy duty Circular Heavy duty lamp hole Extra heavy duty Rectangular Extra Heavy duty Square Extra Heavy duty Circular
Clear opening in frame in (mm) 450 × 600 450 × 450 450 450 × 600 450 560 × 560 600 350 900 ×560 560 × 560 600
As per IS 12592-2002 [28], LD-2.5 grade square manhole and the size of the manhole cover slab was selected as 600 × 600 × 100 mm. Two sets of manhole cover slabs were considered, one sets with conventional concrete (CC) mix and the other sets with CSAC mix. In each sets, one manhole cover slab provided with 10 mm diameter bar and in the other manhole cover slab provided with 12 mm diameter bar Fe 415 grade of steel at 150 mm centre to centre in both the directions. All manhole cover slabs shall be sound and free from cracks and other defects which interfere with the proper placing of the unit or impair the strength or performance of the units. The dimensions of the covers and the breaking load of individual units when tested in accordance with IS 12592-2002 [28]. 3.1 Materials used Ordinary Portland cement (OPC) 53 grade cement conforming to IS 12269: 1987 [29] was used in the production of covers. Crushed stone of 12.5 mm size having fineness modulus of 6.21 and specific gravity of 2.74 was used as coarse aggregate. Locally available river sand (Palar river) having fineness modulus of 6.43 and specific gravity of 2.63 was used as fine aggregate. For mixing concrete constituents and curing purposes, potable water was used. Micro silica was also used as an additive along with concrete constituents and its chemical properties are presented in Table 3. Table 3 Chemical composition of micro silica Chemical Composition Silicon dioxide (SiO2) (%)
% 99.5
Alumina oxide (Al2O3) (%)
0.08
Titanium dioxide (TiO2) (%)
0.04
Calcium oxide (CaO) (%)
0.01
Magnesium oxide (MgO) (%)
0.01
Alkalies (%)
0.29
In addition to the above mentioned materials, steel fibers of diameter 0.35 mm (IS 12592: 2002 specifies, not greater than 0.75 mm), aspect ratio 71 (IS 12592: 2002 specifies 50 to 80) and volume fraction 1 % (IS 12592: 2002 specifies, minimum of 0.5 %) were also used in the concrete mixes.
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3.2 Mix proportions used For the production of manhole cover slab, the mix proportions were selected as 1:2.22:3.66:0.55 and 1:1.47:0.65:0.42 for conventional concrete (CC) and CSAC respectively which were taken from the previously published literature [22, 23 and 25]. Cement content of 320 kg/m3 and 510 kg/m3 were used for CC and for CSAC respectively. The batching of materials used in this study for both CC and CSAC including micro silica and steel fibers which are given in Table 4. Table 4 Batching of materials used for CC and CSAC Constituents Cement (kg/m3) Sand (kg/m3)
For CC 320 710
For CSAC 510 750
Crushed stone (kg/m3)
1171
332
Water - cement ratio
0.55
0.42
Steel fiber (%)
1
1
Micro silica (%)
12
16
3.3 Manhole covers production Manhole covers were cast using both CC as well as CSAC mixes. The reinforcements were prepared as per the sizes and the spacings prescribed in IS: 12592-2002 [28] as shown in Fig.2. Moulds were prepared using ply wood for the required size and shape and the reinforcement was placed inside the mould as shown in Fig.3. The manhole cover slabs were cast (Fig.4 – CC cover slabs and Fig.5 – CSAC cover slabs) and tested after 28 days of curing.
Fig. 2 Reinforcement fabrications
\ Fig. 3 Cover slab mould and reinforcement
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Fig.4 Casting of CC mixes manhole cover slab
Fig.5 Casting of CSAC mixes manhole cover slab
4. Method of testing As per IS: 12592-2002 [28] as shown in Fig.6, for LD-2.5 manhole slab, the specified load 25 kN (test load) shall be applied without shock, through the medium of a bearing block faced with hard rubber. Firstly, 2/3rd of the specified load should be applied and released, like wise this method should be adopted for five times. During this time, the difference of settlement of the specimen should be measured. This settlement should not be more than 1/100th of maximum diameter inscribed on the specimen. After the settlement, the total test load should be applied on the specimen and should be maintained for 30 ± 2s. At this point of time, manhole cover slab shall not show cracks. A schematic arrangement for testing manhole cover slab as per IS: 12592-2002 is shown in Fig.7 and the testing of manhole cover slab actually in the laboratory is shown in Fig.8. Tested manhole cover slabs are shown in Fig.9.
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Fig. 6 Arrangement for load test of manhole cover slab as per IS: 12592-2002
Fig.7 Schematic diagram of load testing in the laboratory
Fig.8 Testing of the manhole cover slab
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Fig.9 Tested manhole cover slabs
5. Results and discussion From the experimental tests conducted on both CC and CSAC manhole covers, parameters such as workability of mixes, density of mixes, compressive strength, settlement and formation of cracks during tests are discussed and presented in this section. 5.1 Workability and density of mixes Slump tests and compaction factor tests were conducted on both CC and CSAC mixes. It was found that the slump value was of 7 mm and 6 mm for CC and CSAC mixes and the compaction factor value was of 0.92 for CC and 0.89 for CSAC mix respectively. Though the degree of workability of both the mixes was very low, it did not experience any workable problem during the casting of concrete cubes as well as manhole cover slab. Fresh concrete density of both CC and CSAC mixes were found to be approximately 2475 kg/m3 and 2020 kg/m3 respectively. Likewise, hardened concrete density of both CC and CSAC mixes at 28 days were found to be approximately 2525 kg/m3 and 2065 kg/m3 respectively. This shows that CSAC mixes are light in weight as compared to CC mixes. 5.2 Compressive strength, settlement and formation of cracks The average compressive strength of CC manhole cover slab was 40.33N/mm2 and the average compressive strength of CSAC manhole cover slab was 35.16 N/mm2 at 28 days respectively. Hardened concrete properties of both CC and CSAC mixes at different age of curing are given in Table 5. Settlements, formation of cracks and ultimate loads during the tests on cover slabs were observed and reported in Table 6. Table 5 Hardened concrete properties Type of concrete CC CSAC
Density (kg/m3) 2475 2020
At 3 Days Compressive strength (N/mm2) 22.00 20.66
Density (kg/m3) 2490 2035
At 7 Days Compressive strength (N/mm2) 30.60 26.60
Density (kg/m3) 2525 2065
At 28 Days Compressive strength (N/mm2) 40.33 35.16
Table 6 Settlement, crack formation and ultimate loads Cover slab produced with 10 mm bar Parameters Settlement limit (6 mm) No crack formation at test load (25 kN) Ultimate load (kN) Settlement at ultimate load (mm)
Cover slab produced with 12 mm bar
CC
CSAC
CC
CSAC
0.06 No cracks formation
0.11 No cracks formation
0.05 No cracks formation
0.09 No cracks formation
107.90
103.00
118.85
106.10
0.14
0.16
0.10
0.12
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As per IS: 12592-2002 minimum compressive strength required for the production of manhole cover slab is 30.0 N/mm2. In this study the selected mixes gives 40.33 N/mm2 and 35.16 N/mm2 for CC mix and CSAC mix respectively. Similarly as per IS:12592-2002, the minimum settlement limit specified is 6 mm and the test results of settlement of CC is found to be 0.06 mm and of CSAC is 0.11 mm which are within the limits specified in IS:125922002 [28]. As per the standard IS: 12592-2002, 25 kN test load was taken and sustained by both CC and CSAC cover slabs and also there was no formation of cracks at this test load on the cover slabs. In this study it was observed that there was no formation of cracks in both CC and CSAC mixes manhole cover slabs. The ultimate load for CC and CSAC were found to be is 107.90 kN and 103.00 kN in case of cover slabs produced with 10 mm bars and 118.85 kN and 106.10 kN in case of cover slabs produced with 12 mm bars respectively. 6. Conclusions Recently, there is an established type of concrete in which coconut shell is used as coarse aggregate in place of conventional coarse aggregate. Starting from the physical, chemical and mechanical properties of coconut shell, production of coconut shell concrete, fresh and hardened mechanical and bond properties, beam elements behavior under flexure, shear and torsion, plastic shrinkage characteristics and durability properties of coconut shell concrete were reported in the past publications [20-27]. Since this concrete is the recent establishment in concrete technology and have ample scope for more research, taken effort and done research on coconut shell concrete. Therefore to form another track for research on coconut shell concrete, already a study was taken and produces a kind of coconut shell concrete pipe [27] and hence in this study, an attempt is made to produce manhole cover slabs using coconut shell as a coarse aggregate and studied the essential properties and reported. Both conventional and coconut shell aggregate concrete manhole cover slabs were tested for their strength test, settlement and formation of cracks in accordance with IS: 12592-2002. Based on the results obtained, the following conclusions were made. Mix ratio selected and used in this study for the production of cover slabs can be recommended for manhole cover slabs. Coconut shell aggregate concrete cover slabs have shown good correlations compared with conventional concrete cover slabs in slump (7 mm for CC and 6 mm for CSAC) and compaction factor (0.92 for CC and 0.89 for CSAC). Hardened density of CSAC mix is 18.22 % less compared to the hardened density of CC mix at 28 days. Compressive strength of the CC and CSAC mixes are 40.33 N/mm2 and 35.16 N/mm2 which satisfied the minimum requirement of 30 N/mm2 as per IS: 12592-2002. Settlement at the time of test load on both CC (0.05 & 0.06 mm) and CSAC (0.09 & 0.11 mm), at ultimate load, the settlement of CC (0.10 & 0.14 mm) and CSAC (0.12 & 0.16 mm), manhole cover slabs are well within the limit of 6 mm and also on both CC and CSAC the specimen, no cracks are formed at the time of sustaining test load as specified by IS: 12592 –2002. Load factor against ultimate failure is more than 4 in all the cases, hence it can be concluded that the coconut shell aggregate concrete can be used for the production of manhole cover slab. By doing this the coconut shell can be considered as an alternate material for conventional coarse aggregate and the coconut shell waste landfill can be minimized and will result in resource conservation/environment protection. References [1] H. Weigler, K. Sieghart. Structural lightweight aggregate concrete with reduced density lightweight aggregate foamed concrete. Int J Lightweight Concr 2(2), (1980) 101-104. [2] RN. Swamy, AH. Jojagha. Impact resistance of steel fibre reinforced lightweight concrete. Cem Compo Lightweight Concr 4(4), (1982) 209-220. [3] A. Elinwa. Y.A. Mahmood. Ash from timber waste as cement replacement material. Cem Concr Compo, 24 (2002) 219-222. [4] MA. Mannan, C. Ganapathy. Engineering properties of concrete with oil palm shell as coarse aggregate. Const Build Mater 16 (2002) 29-34. [5] KG. Babu, SD. Babu. Behaviour of lightweight expanded polystyrene concrete containing silicafume. Cem Concr Res 33(5), (2003) 755-762. [6] MA. Mannan, C. Ganapathy. Concrete from an agricultural waste-oil palm shell (OPS). Build Environ, 39 (2004) 441- 448. [7] L. Cavaleri, N. Miraglia, M. Papia. Pumice concrete for structural wall panels. Engg Struct, 25 (2003) 115-125. [8] CK. Kankam. Bond strength of reinforcing steel bars milled from scrap metal. Mat Design 25(3), (2004) 231238.
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[9] K. Ganesan., K. Rajagopal, K. Thangavel. Evaluation of bagasse ash as supplementary cementitious material. Cem Concr Compo 29(2007) 515-524. [10] PS Kumar, MA Mannan, VJ Kurian, H. Achuytha. Investigation on the flexural behavior high-performance reinforced concrete beams using sand stone aggregates. Build Environ 42 (2007) 2622-2629. [11] EA Olanipekum, KO. Olusola, O. Ata. A comparative study of concrete properties using coconut shell and palm kernel shell as coarse aggregates. Build Environ 41 (2006) 297-301. [12] Amarnath Yerramala and C. Ramachandrudu. Properties of Concrete with Coconut Shells as Aggregate Replacement. Int J Eng Inven 1(6), (2012) 21-31. [13] Maninder Kaur, Manpreet Kaur. A review on utilization of coconut shell as coarse aggregate in mass concrete. Int J App Eng Res 7(11), (2012) 5-8. [14] U. Tomas. Jr. Ganiron. Sustainable Management of Waste Coconut Shells as Aggregates in Concrete Mixture. J Eng Sci Tec Rev 6 (5), (2013) 7-14. [15] P. Vishwas. Kukarni, B. Sanjay kumar, Gaikwad. Comparative Study on Coconut Shell Aggregate with Conventional Concrete. Int J Eng Inno Tec (IJEIT) 2(12), (2013) 67-70. [16] S. Parag. Kambli, R. Sandhya. Mathapati. Compressive Strength of Concrete by Using Coconut Shell. IOSR J Engg (IOSRJEN) 4(4), (2014) 1-7. [17] Dewanshu Ahlawat, L.G. Kalurkar. Coconut Shell as Partial Replacement of Coarse Aggregate in Concrete. IOSR J Mech Civil Engg (IOSR-JMCE) (2014) 61-64. [18] Apeksha Kanojia. S.K. Jain. Performance of Coconut Shell as Coarse Aggregate in Concrete: A Review. Int Res J Engg Tech (IRJET) 2 (4), (2015) 1096-1100. [19] Chandraul Kirti, Singh Manindra Kumar, Saxena Anil Kumar, T.R. Arora. Experimental Study of Coconut Shell Concrete. Int J Res App Sci Engg Tech (IJRASET) 3 (II), (2015) 49-53. [20] K. Gunasekaran, P.S Kumar, M. Lakshmipathy. Mechanical and bond properties of coconut shell concrete. Const Build Mater. 25 (1), (2011) 92-98. [21] K. Gunasekaran, R. Annadurai, P.S. Kumar. Long term study on compressive and bond strength of coconut shell aggregate concrete. Const Build Mater 28 (2012) 208-215. [22] K. Gunasekaran, R. Annadurai, P.S. Kumar. Study on reinforced lightweight coconut shell concrete beam behavior under flexure, Mater Des 46 (2013) 157-167. [23] K. Gunasekaran, R. Annadurai, P.S. Kumar. Study on reinforced lightweight coconut shell concrete beam behavior under shear, Mater Des 50 (2013) 293-301. [24] K. Gunasekaran, R. Annadurai, P.S. Kumar. Plastic shrinkage and deflection characteristics of coconut shell concrete slab. Const Build Mater 43 (2013) 203-207. [25] K. Gunasekaran, R. Annadurai, P.S. Kumar. Study on reinforced lightweight coconut shell concrete beam behavior under torsion. Mater Des 57 (2014) 374-382. [26] K. Gunasekaran, R. Annadurai, P.S. Kumar. A study on some durability properties coconut shell aggregate concrete. Mater Struct 48 (2015) 1253-1264. [27] K. Gunasekaran , R. Annadurai, S. Prakash Chandar, S. Anandh, Study for the relevance of coconut shell aggregate concrete non-pressure pipe, Ain Shams Eng J 8 (2017) 523-530. [28] IS 12592: 2002. Indian Standard, Precast concrete manhole cover and frame – specification, First reprint June 2007. [29] IS 12269: 1987. Indian Standard for Specification for 53 grade OPC, reaffirmed January 1999.
ScienceDirect Materials Today: Proceedings 14 (2019) 386–394
www.materialstoday.com/proceedings
ICRAMC_2018
Study on the reinforced manhole cover slab using coconut shell aggregate concrete S. Soumyaa*, G. Pennarasia and K. Gunasekarana a
Department of Civil Engineering, Faculty of Engineering and Technology SRM University, Kattankulathur-603 203, Tamil Nadu, India.
Abstract In this study, two sets of manhole cover slabs were cast; one set with conventional concrete and the other set with coconut shell aggregate concrete. In both the cases, in one set 10 mm steel reinforcements were used and in the other sets 12 mm steel reinforcements were used. These manhole covers were produced and tested as per IS 12592: 2002. In both the concrete, along with conventional materials and coconut shell, steel fibers and micro silica were used to reach the specification required for the manhole cover slab. As per IS 12592:2002, a size of 600 × 600 × 100 mm and light duty grade of manhole cover slab were selected and studied. Test parameters such as workability of mixes, density of mixes, settlement limits at test load, crack formation, ultimate load and settlements at ultimate load results were discussed and presented. It is observed that the settlement at the time of test load on both conventional and coconut shell aggregate concrete manhole cover slabs were well within the limit specified by IS 12592: 2002. In both the cases, there was no formation of cracks at the time of sustaining test load as per IS 12592:2002. Load factors against ultimate failure were more than 4 in all the cases and hence, coconut shell aggregate concrete can be used for the production of manhole cover slabs. Test results and performance of coconut shell aggregate concrete manhole cover slabs encourage the use of coconut shell as an aggregate as the replacement of conventional aggregate in the production of manhole covers. © 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of 2nd International Conference On Recent Advances In Material Chemistry. Keywords: Coconut shell; Aggregate; Manhole cover; Application.
* Corresponding author. Tel.: +91-8220894366; fax: +91-44-27453903. E-mail address: [email protected]; [email protected] 2214-7853 © 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of 2nd International Conference On Recent Advances In Material Chemistry.
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1. Introduction manufacture the concrete simply exist at any place and at any instance; only least time is required for groundwork; it is achievable to make both customary and unbalanced shapes; it is an exceptional material which can admit mostly any material substitution for its customary materials. Consequently there are numerous researches all over the world taking place to substitute its major ingredients by the wastes produced from various sources such as domestic, industrials, agricultural etc., [1-10]. Coconut shell (CS) is one of the agricultural wastes which is used as a coarse aggregate and made usual in the production of coconut shell aggregate concrete (CSAC) by a researcher almost 10 years back [11] and chased by many researchers in the most recent years as well [12-26]. Most of the research results on CS based concrete have not only given confidence to use in the field applications, but its behavior was also equivalent to the customary concrete as well. Previously a study was made and manufactured a kind of CSAC pipe as a field application [27]. Thus, authors attempted a different application of CSAC in to the study on the reinforced manhole cover slab. 2. Coconut shell as an aggregate Adequate debate concerning the availability of CS around the earth and also in and around the local region was prepared and available elsewhere [20-26]. Similarly, how to practice the CS as an aggregate since its raw state and more or less all the essential properties of CS such as physical, chemical and mechanical, how to use the CS for the manufacture of CSAC etc, were published elsewhere [20-26]. Thus, the remarkable properties such as water absorption and specific gravity are revived at this juncture for the benefit of the community who are referring to this article. The CS used in this study had 4.40 % moisture content and absorbed 24.25 % water. Also the specific gravity ranged from 1.10 to 1.25 and the apparent specific gravity ranged from 1.40 to 1.55. Because of its less value of specific gravity while compared to customary aggregates, the concrete made using CS in CSAC possibly will get in to the group of a special concrete called lightweight concrete (LWC). Fig.1 illustrates the crushed CS after saturated surface dry (SSD) condition before it is used in the production of CSAC mixes.
Fig. 1 Ready to use CS for the production of CSAC mix
3. Manhole cover slab The manhole shall be rectangular, circular or square in plan. Manhole of other shapes such as hexagonal or octagonal shapes may also be recommended. The dimensions of these special shapes shall be such that a square or circle drawn circumscribing the extreme outer edges of the manhole cover slab confirming to the dimensions specified for square manhole and dimensions frame for cover slab as given in Table 1 and Table 2 are respectively as per IS 12592: 2002 [28].
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Soumya et al. / Materials Today: Proceedings 14 (2019) 386–394 Table 1 Grades and types Grade
Grade
Type / Shape of cover
designation Light Duty
LD-2.5
Rectangular, Square, Circular
Medium Duty
MD-10
Rectangular, Circular
Heavy Duty
HD-20
Extra Duty
EHD-35
Rectangular,(Scrapper Manhole), Square, Circular and Lamp hole Rectangular,(Scrapper Manhole), Square, Circular
Table 2 Dimensions of frame Grade Designation LD-2.5 LD-2.5 LD-2.5 MD-10 MD-10 HD-20 HD-20 HD-20 EHD-35 EHD-35 EHD-35
Description Light duty Rectangular Light duty Square Light duty Circular Medium duty Rectangular Medium duty Circular Heavy duty Square Heavy duty Circular Heavy duty lamp hole Extra heavy duty Rectangular Extra Heavy duty Square Extra Heavy duty Circular
Clear opening in frame in (mm) 450 × 600 450 × 450 450 450 × 600 450 560 × 560 600 350 900 ×560 560 × 560 600
As per IS 12592-2002 [28], LD-2.5 grade square manhole and the size of the manhole cover slab was selected as 600 × 600 × 100 mm. Two sets of manhole cover slabs were considered, one sets with conventional concrete (CC) mix and the other sets with CSAC mix. In each sets, one manhole cover slab provided with 10 mm diameter bar and in the other manhole cover slab provided with 12 mm diameter bar Fe 415 grade of steel at 150 mm centre to centre in both the directions. All manhole cover slabs shall be sound and free from cracks and other defects which interfere with the proper placing of the unit or impair the strength or performance of the units. The dimensions of the covers and the breaking load of individual units when tested in accordance with IS 12592-2002 [28]. 3.1 Materials used Ordinary Portland cement (OPC) 53 grade cement conforming to IS 12269: 1987 [29] was used in the production of covers. Crushed stone of 12.5 mm size having fineness modulus of 6.21 and specific gravity of 2.74 was used as coarse aggregate. Locally available river sand (Palar river) having fineness modulus of 6.43 and specific gravity of 2.63 was used as fine aggregate. For mixing concrete constituents and curing purposes, potable water was used. Micro silica was also used as an additive along with concrete constituents and its chemical properties are presented in Table 3. Table 3 Chemical composition of micro silica Chemical Composition Silicon dioxide (SiO2) (%)
% 99.5
Alumina oxide (Al2O3) (%)
0.08
Titanium dioxide (TiO2) (%)
0.04
Calcium oxide (CaO) (%)
0.01
Magnesium oxide (MgO) (%)
0.01
Alkalies (%)
0.29
In addition to the above mentioned materials, steel fibers of diameter 0.35 mm (IS 12592: 2002 specifies, not greater than 0.75 mm), aspect ratio 71 (IS 12592: 2002 specifies 50 to 80) and volume fraction 1 % (IS 12592: 2002 specifies, minimum of 0.5 %) were also used in the concrete mixes.
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3.2 Mix proportions used For the production of manhole cover slab, the mix proportions were selected as 1:2.22:3.66:0.55 and 1:1.47:0.65:0.42 for conventional concrete (CC) and CSAC respectively which were taken from the previously published literature [22, 23 and 25]. Cement content of 320 kg/m3 and 510 kg/m3 were used for CC and for CSAC respectively. The batching of materials used in this study for both CC and CSAC including micro silica and steel fibers which are given in Table 4. Table 4 Batching of materials used for CC and CSAC Constituents Cement (kg/m3) Sand (kg/m3)
For CC 320 710
For CSAC 510 750
Crushed stone (kg/m3)
1171
332
Water - cement ratio
0.55
0.42
Steel fiber (%)
1
1
Micro silica (%)
12
16
3.3 Manhole covers production Manhole covers were cast using both CC as well as CSAC mixes. The reinforcements were prepared as per the sizes and the spacings prescribed in IS: 12592-2002 [28] as shown in Fig.2. Moulds were prepared using ply wood for the required size and shape and the reinforcement was placed inside the mould as shown in Fig.3. The manhole cover slabs were cast (Fig.4 – CC cover slabs and Fig.5 – CSAC cover slabs) and tested after 28 days of curing.
Fig. 2 Reinforcement fabrications
\ Fig. 3 Cover slab mould and reinforcement
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Fig.4 Casting of CC mixes manhole cover slab
Fig.5 Casting of CSAC mixes manhole cover slab
4. Method of testing As per IS: 12592-2002 [28] as shown in Fig.6, for LD-2.5 manhole slab, the specified load 25 kN (test load) shall be applied without shock, through the medium of a bearing block faced with hard rubber. Firstly, 2/3rd of the specified load should be applied and released, like wise this method should be adopted for five times. During this time, the difference of settlement of the specimen should be measured. This settlement should not be more than 1/100th of maximum diameter inscribed on the specimen. After the settlement, the total test load should be applied on the specimen and should be maintained for 30 ± 2s. At this point of time, manhole cover slab shall not show cracks. A schematic arrangement for testing manhole cover slab as per IS: 12592-2002 is shown in Fig.7 and the testing of manhole cover slab actually in the laboratory is shown in Fig.8. Tested manhole cover slabs are shown in Fig.9.
Soumya et al. / Materials Today: Proceedings 14 (2019) 386–394
Fig. 6 Arrangement for load test of manhole cover slab as per IS: 12592-2002
Fig.7 Schematic diagram of load testing in the laboratory
Fig.8 Testing of the manhole cover slab
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Fig.9 Tested manhole cover slabs
5. Results and discussion From the experimental tests conducted on both CC and CSAC manhole covers, parameters such as workability of mixes, density of mixes, compressive strength, settlement and formation of cracks during tests are discussed and presented in this section. 5.1 Workability and density of mixes Slump tests and compaction factor tests were conducted on both CC and CSAC mixes. It was found that the slump value was of 7 mm and 6 mm for CC and CSAC mixes and the compaction factor value was of 0.92 for CC and 0.89 for CSAC mix respectively. Though the degree of workability of both the mixes was very low, it did not experience any workable problem during the casting of concrete cubes as well as manhole cover slab. Fresh concrete density of both CC and CSAC mixes were found to be approximately 2475 kg/m3 and 2020 kg/m3 respectively. Likewise, hardened concrete density of both CC and CSAC mixes at 28 days were found to be approximately 2525 kg/m3 and 2065 kg/m3 respectively. This shows that CSAC mixes are light in weight as compared to CC mixes. 5.2 Compressive strength, settlement and formation of cracks The average compressive strength of CC manhole cover slab was 40.33N/mm2 and the average compressive strength of CSAC manhole cover slab was 35.16 N/mm2 at 28 days respectively. Hardened concrete properties of both CC and CSAC mixes at different age of curing are given in Table 5. Settlements, formation of cracks and ultimate loads during the tests on cover slabs were observed and reported in Table 6. Table 5 Hardened concrete properties Type of concrete CC CSAC
Density (kg/m3) 2475 2020
At 3 Days Compressive strength (N/mm2) 22.00 20.66
Density (kg/m3) 2490 2035
At 7 Days Compressive strength (N/mm2) 30.60 26.60
Density (kg/m3) 2525 2065
At 28 Days Compressive strength (N/mm2) 40.33 35.16
Table 6 Settlement, crack formation and ultimate loads Cover slab produced with 10 mm bar Parameters Settlement limit (6 mm) No crack formation at test load (25 kN) Ultimate load (kN) Settlement at ultimate load (mm)
Cover slab produced with 12 mm bar
CC
CSAC
CC
CSAC
0.06 No cracks formation
0.11 No cracks formation
0.05 No cracks formation
0.09 No cracks formation
107.90
103.00
118.85
106.10
0.14
0.16
0.10
0.12
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As per IS: 12592-2002 minimum compressive strength required for the production of manhole cover slab is 30.0 N/mm2. In this study the selected mixes gives 40.33 N/mm2 and 35.16 N/mm2 for CC mix and CSAC mix respectively. Similarly as per IS:12592-2002, the minimum settlement limit specified is 6 mm and the test results of settlement of CC is found to be 0.06 mm and of CSAC is 0.11 mm which are within the limits specified in IS:125922002 [28]. As per the standard IS: 12592-2002, 25 kN test load was taken and sustained by both CC and CSAC cover slabs and also there was no formation of cracks at this test load on the cover slabs. In this study it was observed that there was no formation of cracks in both CC and CSAC mixes manhole cover slabs. The ultimate load for CC and CSAC were found to be is 107.90 kN and 103.00 kN in case of cover slabs produced with 10 mm bars and 118.85 kN and 106.10 kN in case of cover slabs produced with 12 mm bars respectively. 6. Conclusions Recently, there is an established type of concrete in which coconut shell is used as coarse aggregate in place of conventional coarse aggregate. Starting from the physical, chemical and mechanical properties of coconut shell, production of coconut shell concrete, fresh and hardened mechanical and bond properties, beam elements behavior under flexure, shear and torsion, plastic shrinkage characteristics and durability properties of coconut shell concrete were reported in the past publications [20-27]. Since this concrete is the recent establishment in concrete technology and have ample scope for more research, taken effort and done research on coconut shell concrete. Therefore to form another track for research on coconut shell concrete, already a study was taken and produces a kind of coconut shell concrete pipe [27] and hence in this study, an attempt is made to produce manhole cover slabs using coconut shell as a coarse aggregate and studied the essential properties and reported. Both conventional and coconut shell aggregate concrete manhole cover slabs were tested for their strength test, settlement and formation of cracks in accordance with IS: 12592-2002. Based on the results obtained, the following conclusions were made. Mix ratio selected and used in this study for the production of cover slabs can be recommended for manhole cover slabs. Coconut shell aggregate concrete cover slabs have shown good correlations compared with conventional concrete cover slabs in slump (7 mm for CC and 6 mm for CSAC) and compaction factor (0.92 for CC and 0.89 for CSAC). Hardened density of CSAC mix is 18.22 % less compared to the hardened density of CC mix at 28 days. Compressive strength of the CC and CSAC mixes are 40.33 N/mm2 and 35.16 N/mm2 which satisfied the minimum requirement of 30 N/mm2 as per IS: 12592-2002. Settlement at the time of test load on both CC (0.05 & 0.06 mm) and CSAC (0.09 & 0.11 mm), at ultimate load, the settlement of CC (0.10 & 0.14 mm) and CSAC (0.12 & 0.16 mm), manhole cover slabs are well within the limit of 6 mm and also on both CC and CSAC the specimen, no cracks are formed at the time of sustaining test load as specified by IS: 12592 –2002. Load factor against ultimate failure is more than 4 in all the cases, hence it can be concluded that the coconut shell aggregate concrete can be used for the production of manhole cover slab. By doing this the coconut shell can be considered as an alternate material for conventional coarse aggregate and the coconut shell waste landfill can be minimized and will result in resource conservation/environment protection. References [1] H. Weigler, K. Sieghart. Structural lightweight aggregate concrete with reduced density lightweight aggregate foamed concrete. Int J Lightweight Concr 2(2), (1980) 101-104. [2] RN. Swamy, AH. Jojagha. Impact resistance of steel fibre reinforced lightweight concrete. Cem Compo Lightweight Concr 4(4), (1982) 209-220. [3] A. Elinwa. Y.A. Mahmood. Ash from timber waste as cement replacement material. Cem Concr Compo, 24 (2002) 219-222. [4] MA. Mannan, C. Ganapathy. Engineering properties of concrete with oil palm shell as coarse aggregate. Const Build Mater 16 (2002) 29-34. [5] KG. Babu, SD. Babu. Behaviour of lightweight expanded polystyrene concrete containing silicafume. Cem Concr Res 33(5), (2003) 755-762. [6] MA. Mannan, C. Ganapathy. Concrete from an agricultural waste-oil palm shell (OPS). Build Environ, 39 (2004) 441- 448. [7] L. Cavaleri, N. Miraglia, M. Papia. Pumice concrete for structural wall panels. Engg Struct, 25 (2003) 115-125. [8] CK. Kankam. Bond strength of reinforcing steel bars milled from scrap metal. Mat Design 25(3), (2004) 231238.
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