International Journal of Civil Engineering and Technology (IJCIET) Volume 8, Issue 10, October 2017, pp. 498–506, Article ID: IJCIET_08_10_051 Available online at http://http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=8&IType=10 ISSN Print: 0976-6308 and ISSN Online: 0976-6316 © IAEME Publication Scopus Indexed CONTROLLED LOW STRENGTH MATERIAL (CLSM) AS ROBUST BACKFILL MATERIAL Anil Jadhav Nexus Techno Consultants Pramod Bongirwar Indian Road Congress R. R. Raut Pune Municipal Corporation D. P. Patil Pimpri Chinchwad Municipal Corporation ABSTRACT: soil or improved soil/ aggregates with predefined gradation (GSB, WMM) are primitively used for backfill, (both structural / non-structural back fill), pavement bases, void filling etc., with its inherent limitations of air voids, stiffness, need for compaction, susceptibility to water penetration, susceptibility of settlement etc. Controlled low strength material (CLSM) eliminates the drawbacks of soil backfill providing durability to the supporting structure. CLSM is compulsorily a back fill material and not a low strength concrete, rather it can be well defined as material which is designed as concrete with flow ability and strength as per the requirement and used as backfill to avoid the drawbacks of the soil or murum backfill. Contrary to the soil, the strength and thus the bearing strength of the fill can be controlled allowing with scope for future changes. ACI 116R defines CLSM as per the strength criteria, “CLSM as material that results in a compressive strength of less than 8.3 Mpa” CLSM can be designed with varying strength and density, considering the cost and future needs, low strength CLSM shall be necessary to allow future excavation, whereas if the there is no scope for future excavation the strength can be at higher side, further the density of CLSM can be modified as per the cost and material needs. Properties of CLSM can be enhanced as per the requirement to compensate particular need like corrosion resistance, Exacavatability, strength flow ability etc. Material properties such as shrinkage, subsidence and settlement are not considered as specification performance or requirement properties. These properties http://www.iaeme.com/IJCIET/index.asp 498 editor@iaeme.com Anil Jadhav, Pramod Bongirwar, R.R Raut and D.P.Patil are considered as inherent to CLSM and as such; do not require the establishment of specification requirement. Keywords: Clsm, Robust Backfill Material Cite this Article: Anil Jadhav, Pramod Bongirwar, R. R. Raut and D. P. Patil, Controlled Low Strength Material (Clsm) As Robust Backfill Material, International Journal of Civil Engineering and Technology, 8(10), 2017, pp. 498–506 http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=10 1. INTRODUCTION: Laying of new utility services is a continuous operation in all urban areas. The road side land being public land is used for laying the services after taking permission from competent authority. The depth of services could range from 30 centimeters to few meters in case of sewer drains or water mains .Normally after making the trench the same material is backfilled or even if new materials brought the strict control on quality is not maintained for being a small quantity .Proper compaction in such narrow width also poses serious practical problem. Sometimes trench width is increased to accommodate available compaction equipment .Due to inadequate compaction the trench portion get settled, and lead to pot hole formations leading to public criticism. Besides it requires continuous maintenance. CLSM therefore proves an ideal material which addresses all these problems .The highly flow able material fill all voids and uneven side, this gives additional support to moving vehicles and settlement of trench does not take place hence the damage to road surface. In all urban areas there is tendency to construct concrete roads .Edge strip of 1 to 1.5 m is left and either flexible pavement is adopted or paver block is laid .This facilitates convenient laying of services While laying the new services the entire top surface get disturbed. Improper compaction leads to distortion to surface and hence car owners do not have tendency to use this strip and thus there is permanent loss to road width .Solution to this, is a base of CLSM and also restoration of trench by CLSM only. CLSM therefore can prove an ideal solution for this typical urban problem 2. LITERATURE REVIEW – APPLICATIONS AND ADVANTAGES: Flow ability without compaction makes it suitable for tight and restricted areas, compared to traditional soil or modified soil backfill in various 2.1. Backfills: The Ease of placing CLSM in restricted places without compaction facilitates the reduction in trench width or excavation. Traditional methodology of backfilling in layers and compacting will never provide with the uniformity of density as facilitated by CLSM. CLSM can be placed in layers, allowing each layer to harden prior to placing the next layer. 2.2. Structural Fills: CLSM with higher strength can be produced to act as structural fills, in case of BC soil it can distribute structures load on greater area. CLSM can provide a uniform and level surface for uneven sub-grades under foundation footings and slabs. 2.3. Utilities Bedding: CLSM provides an excellent bedding material for pipe, electrical, telephone, and other types of conduits. The flow able characteristic of the material allows the CLSM to fill voids beneath the conduit and provide a uniform support. http://www.iaeme.com/IJCIET/index.asp 499 editor@iaeme.com Controlled Low Strength Material (Clsm) As Robust Backfill Material Encasing the entire conduit in CLSM also serves to protect the conduit from future damage. If the area around the conduit is being excavated at a later date, the obvious material change in CLSM versus the surrounding soil or conventional granular backfill would be recognized by the excavating crew, alerting them to the existence of the conduit. Coloring agents have also been used in mixtures to help identify the presence of CLSM. 2.4. Erosion Control: Laboratory studies, as well as field performance, have shown that CLSM resists erosion better than many other fill materials. CLSM can be used in riprap for embankment protection and in spilling basins below dam spillways, to hold rock pieces in place and resist erosion. CLSM is used to fill flexible fabric mattresses placed along embankments for erosion protection, thereby increasing their strength and weight. In addition to providing an erosion resistance under culverts, CLSM isused to fill voids under pavements, sidewalks, bridges and other structures where natural soil or non-cohesive granular fill has eroded away. 2.5. Void filling: Tunnel shafts and sewers—filling abandoned tunnels and sewers, it is important to use a flow able mixture. A constant supply of CLSM will help keep the material flowing and make it flow greater distances. Basements and underground structures—abandoned basements are often filled in with CLSM by pumping or conveying the mixture through an open window or doorway. 2.6. CLSM has also been used to fill abandoned underground storage tanks (USTs). Nuclear Facilities: CLSM can also be used in unique applications at nuclear facilities, such as waste stabilization, encapsulation of Decommissioned pipelines and tanks, encapsulation of waste-disposal sites, and new landfill construction. 3. RESEARCH SIGNIFICANCE: With the exponential increase in rehabilitation of utilities and development of new utilities like, fibre optical line, natural gas lines the linear and cross excavation along road have also increased, the tradition practice of filling the trench with the same material usually resulted into summit of loose soil along road or depression along road. Further there was no proper control of procedure to handle this issue. The present study is taken up to resolve the above problems by developing a robust material and construction procedure or technology which would add aesthetic up gradation to city look up avoiding shabby patchwork. The main focus of the study was to develop concrete with flow ability which will be used as backfill facilitating its property control competing with the rates of local backfill soil. CLSM developed had essentially all the materials locally available with which the local contractors are well versed further the preparation techniques were bit modified for intended use. The mix design procedure was as per IS10262:2009 using fly ash as main component and cement as secondary also specially formulated admixture were developed for activating fly ash to exhibit hydraulic characteristics as adding fly ash may result into increase in initial setting time. The primary focus was to exhibit early setting with flow ability because of old city layout which was unfavorable for diversions and proper excavation. http://www.iaeme.com/IJCIET/index.asp 500 editor@iaeme.com Anil Jadhav, Pramod Bongirwar, R.R Raut and D.P.Patil 4. MATERIAL USED: Conventional CLSM mixtures usually consist of same ingredients as that of normal concrete Water, Portland cement, fly ash or other similar products, and finer or coarse aggregates or both. The use of standardized materials is not always necessary provided the new materials added are inactive in nature , Selection of materials should be based on availability, cost, specific application, and the necessary characteristics of the mixture, including flowability, strength, Exacavatability, and density. Cement: Ordinary Portland Cement (OPC) of grade 53 confirming to IS 11269:2013 with a specific gravity of 3.12 was used. Fine Aggregates: Basalt rock chrused to confirm zone II of IS 383:1970 with specific gravity ranging from 2.8-3.01 was used. Silt Content was not considered since the strength aspect was not significant. Further it is suggested to use locally available non-reactive aggregates like over burnt bricks in CLSM as it would be a wise decision to reduce the final cost of CLSM. Coarse Aggregates: Locally available, basalt stone aggregates with maximum nominal size 20mm confirming to IS 383:1970 was used. Water: Portable water was used to mixing and curing of CLSM Admixture: Specially formulated admixture was used, the admixture was developed in two components. The first component was Naphtha based retarder cum workability chemical used for increasing the initial setting time and exhibiting flow ability like Self Compacting concrete. The second component consists of accelerator cum activator to start the setting and strength gain. 4.1. MIX DESIGN: The proportioning of the ingredients was as per IS10262:2009, with fly ash as the main ingredient and cement as supplementary material, further the focus of the mix design was to develop substitute for backfill which matches its rate but consist the advantages of CLSM. So the density was lowered to 1750 kg per cubic metre which can be advocated to match with the density of traditional backfill material like murum, GSB etc. The design was formulated for fine contents to match up with the requirements of Self compacting concrete to yield flow ability without segregation. The typical all in aggregate gradation was as below: http://www.iaeme.com/IJCIET/index.asp 501 editor@iaeme.com Controlled Low Strength Material (Clsm) As Robust Backfill Material 4.2. CONCRETE MIX DESIGN: Materials Unit Weight Cement Fly Ash Micro silica 20 mm 10 mm R.Sand C.Sand Water Admixture Kg Kg Kg Kg Kg Kg Kg Kg Kg 50 200 0 313 364 0 567 195 1.50 % M.C. 0.60 0.85 0.05 1.21 W.A 1.28 1.31 1.47 3.65 Correct 0.68 0.46 1.43 2.44 T.Correct 2.13 1.68 0.00 13.85 17.65 1.00cum 50 200 0 311 363 0 554 213 1.50 4.3. RATE ANALYSIS OF CLSM: Sr.NO. Description of Material 1 2 3 4 5 6 7 8 9 10 10 MM Crush Sand River Sand 20 MM Cement Fly Ash Admixture Water Transportation Operating Cost TOTAL GRAND TOTAL Average Rate / kg 0.41 0.55 0 0.41 5 1.5 60 0.05 150 300 Design 1 Amount RS. 363 554 0 311 50 200 3 213 1694 148.83 304.7 0 127.51 250 300 180 10.65 150 300 1772 RS 1772 5. LABORATORY TRIAL: Laboratory trials were conducted to study workability and strength behaviour of CLSM. Observations of CLSM workability was noted in laboratory for intial flow which was intentionally kept at 600mm considering the lead time of 30 min. The sole purpose of 1st component of admixture added was to retard the setting or dropping of slump of CLSM. Figure 1 Flow observed after 30 min around 580mm average http://www.iaeme.com/IJCIET/index.asp 502 editor@iaeme.com Anil Jadhav, Pramod Bongirwar, R.R Raut and D.P.Patil After adding second component which necessarily consists of accelerator and fly ash activator, the slump of 170 mm was noted after 60 min Figure 2 Slump: 170 mm after 60 min Final settings of CLSM in casted cubes were around 4 hours in laboratory. Compressive strength of cubes was noted after 28 days curing as per IS 516: Sr.no 1 2 3 Cube Size 150x150x150 150x150x150 150x150x150 Strength 3.25 3.10 2.98 Average 3.11 Mpa 5.1. PILOT FIELD TESTS: CLSM field trails were conducted with the help of Pune Municipal Corporation at Ideal Colony, Kotrud Pune. The trail was intended for backfill the conduit excavation along the road. The Second field trail was conducted with the aid of Pimpri Chinchwad Municipal Corporation at Dapodi for backfilling the MNGL conduit excavation across the busy PuneMumbai Expressway. 5.2. Kotrud-Pune Trial: (Along the Road) Dated: 06-09-2016 CLSM was produced with mechanized plant (Ready Mix Concrete Plant) of 0.5 cubic metre per batch capacity and transported through transit mixer with a lead time of about 30 min The first component was primarily used at mixing point i.e. RMC plant which gave a flow of about 400-600 mm till 1 hour, again since strength didn’t play a major role in CLSM the water content can be at higher side to retain the flow ability depending upon the lead time or distance of point of discharge. The second components which consist of accelerator with activators were mixed in transit mixer/miller with measured quantity at the point of discharge 10 min before discharge of CLSM with proper mixing. This component enable the CLSM set early for facilitating human movement, but vehicular movement both light and heavy were not advised. Addition of second component reduces the flow ability after 30 minutes, so considering the distance of discharge point it should be accordingly added. CLSM was placed in trenches of about 600mm deep, initial flow was good enough to make the CLSM to flow in all corners and notches on the trench; the trench was filled once till the surface. The surface was roughed after two hours on initial setting. http://www.iaeme.com/IJCIET/index.asp 503 editor@iaeme.com Controlled Low Strength Material (Clsm) As Robust Backfill Material Figure 3 Actual Site Photo after 4 hour. CLSM was hardened enough to bear the load of human which satisfied the design considerations of setting within 6 hours and avoided the practical problems of citizen interference. 6. RESULTS: The 28-day compressive strength of the CLSM was determined using cube specimen of 150mmX150mmX150mm as per IS 516.The compressive strength developed was 3.43Mpa in 28 days. Sr.no Cube Size Strength Average 1 2 3 150x150x150 150x150x150 150x150x150 3.25 3.60 3.45 3.43 Mpa 6.1. Dapodi-MNGL line Trail –Pimpri Chinchwad Dated: 15-08-2017 CLSM was produced with mechanized plant (Ready Mix Concrete Plant) of 1.25 cubic metre per batch capacity and transported through transit mixer with a lead time of about 60 min Going with the experience, the first component was primarily used at mixing point i.e. RMC plant which gave a flow of about 550-700 mm, the second component was mixed in transit mixer/miller with measured quantity at the point of discharge 10 min before discharge of CLSM with proper mixing. CLSM was placed in trenches of about 750mm deep, initial flow was good enough to make the CLSM to flow in all corners and notches on the trench, the trench was filled in layers to prevent the excess pressure transfer on sides bracing. The surface was roughed after two hours on initial setting. A compressive strength result for 28 days using cube moulds of specimen 150x150x150 as per IS 516 was 4.25 Mpa Average. http://www.iaeme.com/IJCIET/index.asp 504 editor@iaeme.com Anil Jadhav, Pramod Bongirwar, R.R Raut and D.P.Patil 7. CONCLUSION: Based on the lab studies and pilot projects Conducted, the following conclusion can be drawn. In the view of problems faced due to disadvantages of convention backfill material results are in favour of CLSM. The desired engineering properties of CLSM in fresh and hardened state can be altered or modified depending upon the project requirement gives CLSM upper hand over the convention soil back fill. The rate analysis of CLSM further advocates its use compared to the convention backfill material which will never give the uniformity in density of back fill and involvement of labour dependency. REFERENCES: [1] [2] [3] [4] [5] [6] [7] ACI Committee 229 (Reapproved 2005) Controlled Low Strength Materials American Concrete Institute Journal AASHTO Guide for Design of Pavement Structures, American Association of State Highway and Transportation Officials, Washington, D.C., 1986. Ramme, B. W., Progress in CLSM: Continuing Innovation, Concrete International, V. 19, No. 5, May 1997, pp. 32-33. Adaska, W. S., Controlled Low-Strength Materials, Concrete International. 19, No. 4, Apr. 1997, pp. 41-43. IS 12269-2013 Indian Standard Specification for Ordinary Portland Cement-53 Grade (First Revision) Bureau of Indian Standards, New Delhi IS 383-1970 (Reaffirmed 1997) Indian Standard Specification for coarse and fine Aggregates from Natural Source for Concrete Bureau of Indian Standards, New Delhi. IS 9103-1999 Indian Standard Specification for Concrete Admixtures, Bureau of Indian Standards, New Delhi. http://www.iaeme.com/IJCIET/index.asp 505 editor@iaeme.com Controlled Low Strength Material (Clsm) As Robust Backfill Material [8] [9] [10] [11] [12] IS 10262-2009 Indian Standard Concrete Mix Proportioning Guidelines (First Revision) Bureau of Indian Standards, New Delhi. IS 516-1959 Method of test for Strength of Concrete Bureau of Indian Standards, New Delhi. India K. V. Ramesh, R. Goutham and I. Siva Kishore An Experimental Study on Partial Replacement of Bagasse Ash in Basalt Concrete Mix, International Journal of Civil Engineering and Technology, 8(5), 2017, pp. 335–341. K. Kiran and I. Siva Kishore, An Experimental Study On Partial Replacement of Cement with Bagasse Ash In Concrete Mix. International Journal of Civil Engineering and Technology, 8(1), 2017, pp. 452–455. Salman A. Al-Duheisat and Amjad Saleh El-Amoush, Bend Cracking Behavior of Hydrogenated Low Strength Structural Steel Under Different Heat Treatment Conditions, International Journal of Advanced Research In Engineering and Technology (IJARET), Volume 5, Issue 4, April (2014), pp. 111-118 AUTHORS BIOGRAPY: Anil Jadhav: is certified Concrete Technologist, holds Diploma, Bachelors, Degree in Civil Engineering and PGPCM (Construction Management) from AICTE, PUNE UNIVERSITY and NICMAR respectively. Presently working as Chief Consultant with NEXUS TECHNO CONSULTANTS and visiting Industrial faculty for Advanced Concrete Technology with MIT Academy of Engineering, Alandi, Pune. He has 10 years of experience with Transportation Engineering and Concrete Technology. His Prime area of focus is to research and develop Innovative Construction Materials and Technology. Pramod Bongirwar, Retired in March 2003 in the capacity of Principal Secretary, PWD.Was involved in executing several prestigious projects as Mumbai, Pune expressway, 50 Flyover in Mumbai, 25 ROB, Planning for 20000 tenements for project affected persons etc. Introduced several cost effective and innovative designs of bridges After retirement served as part time Advisor with IDFC for 11 years and now with Larsen and Toubro for last 12 years Has experience of 20 years on BOT projects and major highway projects Served as members of several IRC Committees and Government advisory committees. Written several articles in National and International conferences Recipient of Distinguished Alumnus Award of IIT, Mumbai. Rajendra Raut, Chief Engineer (Roads) Pune Municipal Corporation, is Graduate Civil Engineer from Pune University having 28 years’ experience with almost 20 years in Road department of PMC was involved in much technological innovative initiative undertaken by PMC. Deepak Patil: Deputy Engineer (BRTS) Pimpri Chinchwad Municipal Corporation is Graduate Civil Engineer from Pune University having 15 years’ of experience. Currently involved with BRTS Division of PCMC. http://www.iaeme.com/IJCIET/index.asp 506 editor@iaeme.com