Mitigation of rutting in bituminous roads by use of waste polymeric packaging materials

Transcription

1 Indian Journal of Engineering & Materials Sciences Vol. 18, June 2011, pp Mitigation of rutting in bituminous roads by use of waste polymeric packaging materials P K Jain*, Shanta Kumar & J B Sengupta Central Road Research Institute, CSIR, New Delhi , India Received 23 December 2009; accepted 5 May 2011 Rutting is caused by accumulation of permanent deformations caused by repeated applications of traffic loads and it is a stress controlled cyclic loading phenomenon. The process of deformation of bituminous surfacing is accelerated by increase of pavement temperature, reduction in stiffness of mix and increase in traffic loads. The aim of this paper is to report findings of study on increase in stiffness modulus of bituminous mixes by incorporation of waste polymeric packaging material (WPPM) to enhance pavement performance as well as to protect environment. This work presents studies on use of WPPM in road construction. Polymeric poly packs are used for packaging of milk for distribution to consumers and such bags after consumption of milk are thrown away. These used milk bags and other high density polyethylene (HDPE) based carry bags are used as additives in bituminous mixes. The optimum dose of these two types of WPPM for modification of bitumen and bitumen mix is investigated. Results reveal that optimum dose of WPPM is 0.3 to 0.4% by weight of bituminous mix. Higher dose lead to undesirably higher stiffness of mix. Rutting of bituminous mix can be reduced to 3.6 mm from a value of 16.2 mm after application of 20,000 cycles, by adding optimum quantity of WPPM in bituminous mix for road construction. Indirect tensile strength ratio further confirm potential of these mixes in prevention of moisture damage also, ultimately improvement of pavement performance, besides alleviating disposal problems of WPPM for clean and safe environment. Keywords: Bituminous roads, Waste polymeric packaging material, Pavement, High density polyethylene, Rutting Integration of global markets and promising outlook for world economy offered immense opportunities in various sectors for plastic industry in the last two decades. The present boom in industrial growth of plastic industry is as a result of new developments in usage of plastics in various sectors, viz, packaging, agriculture, automobiles, buildings, water management, processed foods and health welfare as key material for these sectors and these have changed people s life style in developing countries like India. Though, plastic is said to be environment friendly in various sectors, disposal of WPPM generated from domestic waste is a matter of concern for environmentalists. Disposal of WPPM causes health hazard. WPPM is a source of fire near disposal sites and also clogs drainage system in urban areas. Also, WPPM is a potential source of fire in forest areas. Plastic 1 constitutes significant part of municipal waste. It is in the range of 6-8% by volume of municipal waste. Hence, there is an urgent need to look for a sustainable approach for use of WPPM in *For correspondence ( pk_crri@rediffmail.com, pramodj.crri@nic.in) construction industry. Use of disposed plastic bags in road construction appears to be the sustainable option in urban areas to protect environment and alleviate problem of clogging drainage system. A number of laboratory and field studies 1-6 were conducted by researchers in the recent past for the quest of development of improved bituminous materials using WPPM. The process developed by Pinoma et al. 2 make the use of thermoplastic materials from domestic and industrial waste such as containers and films comprising polyethylene, polypropylene and other non-biodegradable polymers. The major sources of HDPE based WPPM are high quality carry bags and milk bags in urban area. The key constituents of these materials are different grades of thermoplastic polyethylene. Larry 3 reported reduction in permanent deformation and low temperature cracking of bituminous surfacing using recycled grocery bags in bituminous mixes. Recently, laboratory performance characteristics of bituminous mixes modified by recycled low density polyethylene from waste plastic bags has been reported by a number of investigators 4,5. Kajal and coworkers 6 investigated use of waste plastic and copper slag for low cost road

2 234 INDIAN J ENG. MATER. SCI., JUNE 2011 construction. Data of these pilot studies have indicated favorable results. Studies on bitumen modification 7 by HDPE (pure) favored lower concentrations of HDPE. Hence, a comprehensive laboratory study was felt essential for development of optimum composition of modified bituminous mixes using HDPE found in WPPM. This paper deals with findings of a study undertaken to optimize quantity and quantity of WPPM obtained from high density polyethylene bags used for packaging milk and other materials used in cities, for modification of bituminous mixes. Paper mainly focuses on control of deformation and rutting at high pavement temperature, WPPM being a thermoplastic material, as additive in bituminous mixes used for road construction. This study presents the use of waste polymeric packaging material (WPPM) and its potential in improvement in performance of bituminous roads and its cost effectiveness. Materials and Methods Materials 60/70 grade bitumen from a local refinery is used in the present study and its properties are given in Table 1. Aggregate from local quarry (Quartzite type) is used for preparation of bituminous mixes. Results of physical properties of mineral aggregates are given in Table 2. Grading of aggregates as per Ministry of Road Transport and Highways Specification (MoRTHS 8 ) for 50 mm thick bituminous concrete are given in Table 3. For the present study, WPPM from used milk bags as well as other carry bags are used. These are Table 1 Physical properties of 60/70 bitumen characterized by infrared spectra (Fig. 1) and thermo gravimetric analysis (Fig. 2). IR spectra were recorded on neat specimen films directly by Spectrum 1 FTIR (Perkin Elmer). The TGA is recorded by Perkin Elmer TGA system in air. The peaks in infrared spectrum and their assignments are given in Table 4. Methods Preparation of mixes Bituminous mixes for this study were prepared in a mixing pan. For preparation of mixes, aggregate was heated to 175 C and bitumen to 160 C. Aggregate was taken in a pan and requisite quantity of bitumen was then added to heated aggregate and both the ingredients were mixed vigorously using a spatula. In case of WPPM modified mixes, requisite amount of WPPM was added to aggregate before adding bitumen at 175 C and mixed for one minute followed by addition of melted bitumen. The temperature of bitumen was 165 C and mixing time was enhanced to Table 3 Gradation of bituminous concrete mixes Sieve size, mm Adopted grading Specified grading Properties Test method Value Penetration, 0.1 mm, at 25ºC, 5 s, 100 g IS Softening point, ºC, R&B IS Ductility at 27ºC, 5 cm/min IS Viscosity at 60ºC, Pa IS Viscosity at 135ºC, cst IS Table 2 Properties of aggregates Properties Test method Value Impact value, % IS 2386(Part-4) 16 Water absorption, % IS 2386(Part-4) 0.8 Specific gravity, g/cm 3 IS 2386(Part-4) 2.66 Combined index (FI+EI),% IS 2386(Part-4) 36 Stripping,% IS Fig. 1 Infrared spectra of typical WPPM sample

3 JAIN et al. : MITIGATION OF RUTTING IN BITUMINOUS ROADS min. For modification of bituminous mixes, different dosage of WPPM in 5-10 mm 3-6 mm size are added to heated aggregate at 175ºC just before addition of bitumen (at optimum bitumen content of 5.3% by weight of aggregates). The quantity of WPPM varied from 0.1 to 0.6 % by weight of total bituminous mix. Testing of mixes For testing of stability, flow, indirect tensile strength (ITS) and stiffness modulus, Marshall specimen of 101 mm diameter and 63 mm height using 75 blows on both sides were prepared by standard rammer at 155 C as per procedure described in ASTM D The results of stability, flow, Marshall quotient (stability/flow), indirect tensile strength (ITS) and stiffness modulus at 35ºC along with methods of test adopted are given in Table 5. Volumetric and engineering properties of mixes at varying WPPM content are given in Table 5. ITS test was conducted on Marshall samples of conventional bituminous mix as well as modified mixes at 25ºC. Tensile strength The ITS test was performed by loading a Marshall specimen with single compressive load, which act parallel to and along vertical diametrical plane. This loading configuration develops a relatively uniform tensile stress perpendicular to the direction of the applied load along the vertical diametrical plane, which ultimately causes the specimen to fail by splitting along the vertical diameter. The load at Table 4 Peaks in FTIR spectra and their interpretations for WPPM sample Peaks Interpretation Peaks Interpretation C-H Stretching of CH C-H Bending of CH C-H Bending of CH CH 2 Rocking failure was recorded and the indirect tensile strength was calculated using following equation: S t = 2p/πdt where, p is load (kg), d is diameter of the specimen (cm) and t is thickness of the specimen (cm). Tensile strength ratio (TSR) test The tensile strength ratio of asphalt mixes is an indicator of their resistance to moisture susceptibility. The test was carried out by loading a Marshall specimen with compressive load acting parallel to and along the vertical diametric-loading plane. The test was conducted at 25 C temperature and the load at which the specimen fails is taken as the dry tensile strength of the asphalt mix. The specimens were then placed in a water bath maintained at 60 C for 24 h and then immediately placed in an environmental chamber maintained at 25 C for two hours. These conditioned specimens were then tested for their tensile strength. The ratio of the tensile strength of the water-conditioned specimens to that of dry specimens is the tensile strength ratio. Fig. 2 TGA trace of WPPM sample Table 5 Volumetric and mechanical properties of mixes at varying WPPM content Properties Method WPPM % Bulk density, g/cm 3 ASTMD Air voids, % ASTMD Voids filled by bitumen, % ASTMD Bitumen content, % ASTMD Marshall stability Kg, 60ºC ASTM D Marshall flow, mm at 60ºC ASTMD Marshall quotient, kg/mm Stab/Flow Indirect tensile strength, kg/cm 2, at 25 C ASTM D Tensile strength Ratio ASTM D Stiffness modulus MPa, 35ºC ASTM D

4 236 INDIAN J ENG. MATER. SCI., JUNE 2011 Tensile strength ratio (TSR) is calculated as given below : T2 TSR = T * where, T 1 is average tensile strength of dry specimen and T 2 is average tensile strength of wet specimen. Test for density (ASTM D 2726) Determine the mass by weighing the specimen after it has been standing in air at room temperature for at least 1 h. Designate this mass as A. To get the mass of the specimen in water, completely submerge the specimen in water bath at 25 C for 3 to 5 min, and then determine the mass by weighing in water. Designate this mass as C. Then, surface dry the specimen by blotting quickly with a damp cloth towel and then determine the mass by weighing in air. Designate this mass as B. The specific gravity can be calculated as: Bulk specific gravity = A / (B C) Percent air voids (ASTM D 3203) The percent air voids in a compacted bituminous paving mixture are calculated as: Percent air voids = 100 (1 (bulk specific gravity/theoretical maximum specific gravity)) The theoretical maximum specific gravity may be calculated as per ASTM D Stiffness modulus test was conducted by the method described in ASTM D 4123 at different temperatures for a mix containing 0.3% WPPM content. Rut depth studies were carried out on rectangular specimen of 305 mm 305 mm 50 mm size at 46ºC, 52 C and 58ºC, test temperatures are adopted for compliance of SHRP binder testing temperature. Samples were prepared at minimum 95% compaction of the designed density and 6% air voids in bituminous mix. In the present study, slabs were compacted in standard moulds by a static compression machine at 155ºC. This procedure utilizes compression machine calibrated to compact the weighed amount of bituminous mix in a standard mould for required density and thickness. The slabs were cured at room temperature for 24 h and then placed in the computer controlled wheel-tracking machine for conditioning at selected test temperature (46ºC, 52 C and 58 C) for 4 h. Test was started, when sensor embedded in the mix displayed stable test temperature. Each sample was subjected to reciprocate load repetition for 20,000 passes or until 20 mm rut depth on the slab surface. Method described in BS was adopted for rut depth studies using Wheel Tracking System procured from M/s. Proeti, SA, and Madrid. The rate of tracking was kept 42 passes per minute. Binder from modified mixes was extracted by Abson Method (ASTM D 1856) and recovered binders were tested for penetration, softening point and elastic recovery. Data presented in Table 6. Results and Discussion Characterization of WPPM A typical infrared spectrum of WPPM is shown in Fig. 1. The interpretation of various peaks is presented in Table 4. Data confirmed that the products used in present study are mainly HDPE based waste plastic materials. Thermal techniques are used for characterization of polymers, performance evaluation and determination of processing parameters of polymer based composites. In the present study, degradation behavior of WPPM is investigated by thermo gravimetric analysis. The relative thermal stability is assessed by comparing the initial decomposition temperature (IDT), and percent weight loss. In this case, IDT is very high and value is close to 425 C. A typical TG trace (Fig. 2) indicates negligible loss up to 400 C in TGA Curve. The melting temperature of WPPM is around 110 C, as reported elsewhere 6. Characterization of mixes Marshall mix design was conducted on conventional mixes to arrive optimum bitumen content using 60/70 bitumen. Varying quantity of WPPM was added and volumetric properties such as bulk density, voids and voids filled by bitumen were measured. Effect of temperature on stiffness modulus of bituminous mix with and without WPPM is plotted in Fig. 3. Progressions of rutting at different temperatures and at different WPPM content are plotted in Figs 4 and 5. Table 6 Properties of binder after extraction and recovery Properties of recovered binder Method WPPM % of Test Penetration, 0.1m, 25 C, 5s,100g IS Softening point, ºC IS Elastic recovery at 15ºC, % IS

5 JAIN et al. : MITIGATION OF RUTTING IN BITUMINOUS ROADS 237 Data given in Table 5 indicate reduction in bulk density of compacted mixes modified by WPPM with its incremental addition. This behavior is attributed to lower specific gravity value of WPPM. There is about 30% increases in stability values by incorporation of 0.2 to 0.3% WPPM. The increase in Marshall quotient value is about 11.5% by incorporation of 0.3% WPPM. Further addition of WPPM to bituminous mixes lead to decrease in Marshall quotient due to Fig. 3 Effect of temperature on stiffness modulus of bituminous concrete mix with and without WPPM Fig. 4 Progression of rutting in different mixes at 46 C for bituminous concrete mix Fig. 5 Progression of rutting in different mixes at 58 C for bituminous concrete mix increase in flow values. Hence, incorporation of excessive WPPM was not found beneficial for performance of road surfacing. There is significant increase in stiffness modulus at 25-35ºC (Fig. 3) by addition of 0.3% WPPM. In the present case, 0.3% WPPM was found optimum for modification of bituminous mixes. Data given in Table 5, indicate that values of Marshall quotient are in conformity to IRC: SP: ( kg/mm). Addition of excessive WPPM led to increased flow value of mixes, eventually stiffness modulus decreases as evident by lower values of Marshall quotient at 0.6% WPPM context in mix. Indirect tensile strength data given in Table 5 show 20-25% increase in strength by adding 0.2 to 0.4% WPPM. Higher values of indirect tensile strength are indicative of better resistance to cracking at moderate pavement temperature. Results of retained tensile strength (Table 5) indicate resistance to retention of adhesion of bitumen with aggregate in presence of water. Samples were conditioned at 60ºC for a period of 24 hours. Then the samples were removed from the water bath and kept at a temperature of 25 ºC for a period of 2 hours before testing. The increase in retained ITS value is marginal, indicating negligible improvement in control of moisture damage of bituminous surfacing modified by WPPM. The stiffness modulus values of mixes at various temperatures are plotted in Fig. 3. It can be seen from the test data given in Table 5 and results plotted in Fig. 3, that stiffness modulus of mixes increases by incorporation of 0.2 to 0.3% WPPM. Hence, reduced thickness of bituminous concrete using modified mixes may be equivalent to higher thickness using conventional bitumen. Resistance to rutting of bituminous mixes depends upon several factors such as volumetric composition, shape of aggregate and characteristics of binders. Wheel tracking test is one of the most direct means of assessing this effect on performance of mixes. Rutting test was conducted at 46ºC, 52 ºC and 58ºC for 20,000 cycles and typical test results are plotted in Fig. 4. The data of rutting test for different mixes modified by WPPM is given in Table 7. Table 7 Summary of rut depth Test temperature Rutting, mm for various WPPM % 0.0 % 0.1 % 0.2 % 0.3 % 46 C C C

6 238 INDIAN J ENG. MATER. SCI., JUNE 2011 It can be seen from data plotted in Fig. 4 that incorporation of 0.3% WPPM reduced rutting from 6.1 mm and 16.2 mm to 3.6 mm and 3.9 mm at 46ºC and 58 o C temperature respectively after 20,000 passes. Hence, incorporation of 0.3% WPPM reduces rutting of bituminous surfacing specifically at high temperature, indicating beneficial use of WPPM modified mixes in hot climate areas. It can be inferred that besides sustainable usage of WPPM, improvement in performance of bituminous road surfacing is also observed using WPPM modified mixes at high pavement temperature. Binder from modified mixes was extracted by Abson recovery (ASTM D1864) method and the results are presented in Table 6. The elastic recovery values of extracted binder are in the range of 16 to 29%, indicating presence of sufficient elastic properties in binder due to WPPM. These values are close to a value given in BIS specification IS However, measurement of elastic recovery is not mandatory of plastomer modified bitumen. Conclusions High density polyethylene and low density polyethylene are key constituents of WPPM from used milk bags and grocery bags, which constitute major portion of non biodegradable plastic waste in urban areas. It can be concluded from this study that WPPM can be conveniently used as modifier in bituminous mixes for sustainable management of plastic waste. The use of 0.3 to 0.4 percent WPPM by weight of mix is optimum and safe besides substantially improving performance properties of bituminous mixes. Therefore, use of WPPM in bituminous mixes can lead to improvement in life of bituminous surfacing and quality of life of urban people. Results indicate that incorporation of WPPM in excess of 0.4% may be harmful to engineering properties of the bituminous mixes as excessive rutting is observed in laboratory samples. Hence, WPPM can be used for beneficiation of bituminous mixes, provided waste comprises HDPE or LDPE. The estimated consumption of WPPM is 2 tone/ km (40 mm BC, 7000 m 2 ). Modification of bituminous mixes with WPPM is more beneficial for high temperature areas. WPPM Modified Mixes are found to be very useful in mitigating deformation and rutting of bituminous surfacing in hot climate areas. Use of WPPM in road construction is the best sustainable option for disposal of non-biodegradable plastic waste. Acknowledgements Authors wish to express sincere thanks to Director, Central Road Research Institute for his encouragement during this study. References 1 Jain P K & Sengupta J B, Indian J Eng Mater Sci, 14 (2007) Pinomaa O, Korhonen M & Kellomaki A, Proc Congr Eurasphalt and Eurabitume, Strasbourg, Larry F, Road Bridges, USA, (1993) V S Punith & A Veeraraghvan, Highway Res Bull, 70 (2004) Sridhar R, Bose S, Kumar G & Sharma G, Highway Res Bull, 71 (2004) Kajal, Pundhir N K S, Sangita and Chandra A, J Sci Ind Res, 66 (2007) Zoorrob S E, Proc Conf Technol Watch and Innovation in Construction Industry, Belgium, Specifications for Road and Bridge Works, Ministry of Road Transport and Highways, New Delhi, Fourth revision, Test Method for Resistance to Plastic Flow of Bituminous Mixtures Using Marshall Apparatus, ASTM D-1559, vol Road and Paving Materials.