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Full Paper Proc. of Int. Conf. on Advances in Design and Construction of Structures 2012

Effect of Use of Recycled Concrete Aggregates in Bituminous Concrete Surface Course Gurukanth S1, Donal Nixon D’souza2, Avinash Babu S3, Vivek A K4 and Dr.Srikanth M Naik5 1

UG Student, Department of Civil Engineering, MSRIT, Bangalore, India. Email: guru_kanth@hotmail.com 2 UG Student, Department of Civil Engineering, MSRIT, Bangalore, India. Email: donalnixon@gmail.com 3 UG Student, Department of Civil Engineering, MSRIT, Bangalore, India. Email: avinashbabu123@gmail.com 4 UG Student, Department of Civil Engineering, MSRIT, Bangalore, India. Email: vivekakannan15@gmail.com 5 Professor, Department of Civil Engineering, MSRIT, Bangalore, India. Email: srikanth_naik@yahoo.com I. INTRODUCTION

Abstract—India has a road network of over 4.32 million kilometres as of 2011, the third largest road network in the world. However, qualitatively Indian road network are a mix of modern highways, narrow paved roads & unpaved roads. As of 2008, 49% i.e. 2.1 million kilometres of Indian roads are paved. India plans to spend approximately 70 billion USD by 2013to modernize its road network. Several projects like Pradhan Mantri Grama Sadak Yojana (PMGSY) have been initiated by Government of India to upgrade rural roads to black top surface roads. Aggregates form a bulk of the material required for bituminous concrete pavements. Aggregate being a natural material is being fast consumed and is causing a shortage of resources required for rapid infrastructure development. Also on the other side with the new trends in construction industry there is a generation of solid waste in the form of demolished structures. Cement concrete being a non biodegradable element is a challenge to dispose.Generally demolished concrete ends up in landfills. However with new environmental regulations and limited space available, concrete disposal has been a major environmental challenge.Today, science and technology has a responsibility of innovating new trends which are both economical and ecofriendly. Old demolished concrete structures can be recycled to obtain recycled aggregate (RA). This can be used along with the natural aggregates effectively in various infrastructure need so that we attain a balance between demand and supply of construction material thereby reducing the impact on nature. The present investigation aims in the strength variation of bituminous concrete surface course in which recycled aggregates are used in partial or full replacement of natural aggregates. Marshall’s method is used to study the strength variations in bituminous concrete surface course with replacement of natural aggregates with recycled aggregates. It was found that replacement of natural aggregates by recycled aggregates upto 20% is possible in bituminous concrete surface course without significant impact on the strength characteristics. However there is an increase in the binder content for which there is a need to study the economic value of the replacement.

Aggregate form a major portion of the pavement structure and they form the prime material used in pavement construction. Aggregates have to bear stresses occurring due to the wheel loads on the pavement and on the surface course they have to resist wear due to abrasive action of traffic. These are used in pavement construction in cement concrete, bituminous concrete and other bituminous construction and also as granular base course underlying the superior pavement layers. Most of the road aggregates are prepared by crushing natural rock. Natural materials are of limited availability and its quantities are declining rapidly creating an acute shortage. It is estimated that 750 million cum of aggregate would be required for achieving the targets of the road sector [1]. Researchers are looking for alternative materials for highway construction which are economical and ecofriendly. Concrete recycling is becomining an increasingly popular way to utilize the aggregate left behind when structures and roadways are demolished [2]. In the past, this rubble was disposed off in landfills, but with more attention being paid to environmental concerns, with existing woes of solid waste management system and an aim towards sustainable development. Re-utilization or recycling seems to be an attractive alternative and an important strategy for management of such waste which could flourish as a good business, if done in a proper manner. For further utilization of recycled aggregates, a proper study needs to be done for its use in the construction and infrastructure projects. Recycling of concrete not only allows the reuse of the rubble, but also helps in conserving the natural resources, reducing the construction costs. Recycled aggregates (RA) can be obtained from crushed concrete rubble (from C & D wastes) comprising of crushed and uncrushed parent aggregate coated with mortar and small pieces of hardened mortar.

Keywords— Bituminous concrete surface course, Recycled aggregate, Marshall’s method.

Full Paper Proc. of Int. Conf. on Advances in Design and Construction of Structures 2012 II. RECYCLING OF CONSTRUCTION AND DEMOLITION WASTES

mortar adhering to the recycled aggregate lead to higher reduction in specific gravity of the recycled aggregate which in turn results in reduced quantity of coarse aggregate to be used in recycled aggregate concrete (RAC) [6][7][8][9]. Also it was observed that the water absorbtion value was significantly high [5][7] for recycled aggregate which may be due to the type and maximum size of the parent aggregate used in parent concrete, strength of the parent concrete [7] and due to mortar phase having higher porosity than that of the aggregate phase in recycled aggregate [7][9]. In the pavement sector, recycled aggregates have used from Reclaimed Asphaltic Pavements (RAP) in hot mix asphalt (HMA) since 1980 [10]. This has generally been used by various state transport agencies in the United States. The use of RAP also decreases the amount of waste produced and helps to resolve the disposal problems of highway construction. In 1996, it was estimated that about 33% of all asphaltic pavements in the United States was recycled into HMA [11]. In 2001, the Illinois department of Transportation (IDOT) used 623,000 tons of RAP in highway construction and anticipates increasing its use in the near future [12]. After more than 30 years since its first trial in Nevada and Texas, it appears that the use of RAP will not only be a beneficial alternative in the future but will also become a necessity to ensure economic competitiveness of flexible pavement construction. Recycled aggregates obtained from demolished building waste material can be effectively utilized for base and sub base construction of road projects [13]. Use of recycled aggregates in sub base can reduce the construction cost by 40% [14]. However no work has been done on the use of recycled aggregates in bituminous concrete surface course.

Wastes arising from construction and demolition (C & D) constitutes one of the largest streams in many countries. It has been estimated that approximately 180 million tons of construction and demolition wastes are produced every year in the European Union. Germany is the leading producer of C & D waste with 77 million tons followed by United Kingdom with 30 million tons. It is estimated that the construction industry in India generates about 10-12 million tons of waste annually [3]. Demolished building waste contains cement concrete, bricks, cement plaster, steel, stone, timber, piping, electrical fixtures, panels and glass. Minor components like steel, piping and electrical components goes to the scrap yard where as bulk material like concrete ends up in landfills and land reclamation sites. Concrete and masonry waste can be recycled by sorting, crushing and sieving into recycled aggregates. These recycled aggregates can be used to make concrete for road construction and building material. Recycling of concrete and masonry waste is very well done in developed countries like U.K., USA, France, Denmark, Germany and Japan. According to a study commissioned by Technology, Information, Forecasting and Assessment Council (TIFAC), 70% of the construction industry in India is not aware of recycling techniques. However work on recycling of aggregates has been done at Central Building Research Institute (CBRI) Roorkee. Aggregates from concrete can be easily recycled by crushing the concrete in a rock crusher after removing all the reinforcement. The crushed concrete is sieved in a mechanical sieve and sorted out. The recycled aggregates are then washed to remove all dust and fine particles.

IV. MATERIAL USED

III. LITERATURE REVIEW

A. Aggregate Natural aggregates used in the study were obtained from local quarry in Yelahanka, Bangalore North. Aggregate passing 20mm sieve was used and its physical properties are given in table (I). Rock dust available in the quarry was used as filler material. Recycled aggregate was obtained from the demolished waste concrete from the demolished old medical block of M.S.Ramaiah Medical College, Bangalore, which was around 30 years old at the time of demolition. Only concrete was used and no brick masonry was used. Concrete beams and slabs of the demolished material were broken down with the help of a jackhammer drill to remove reinforcements.The concrete was then crushed in the crusher to obtain recycled aggregates. The aggregates were washed in running water to remove impurities and later soaked for 24hours before drying at room temperature. Powdered mortar obtained from demolished material is used as filler material. Material passing 20mm is used and its physical properties are given in table (I).

Rapid industrialization and urbanization in the late 80â&#x20AC;&#x2122;s created a great boom in the construction industry of India, this caused a rapid decline of natural aggregates causing a serious shortage of raw materials. This initiated research in the field of recycling and reusing of waste materials in the construction industry. However research was more focused on using recycled aggregates in cement concrete mixes [2][4][5][6]. The findings from the recent experimental investigation showed that for recycled aggregates (RA), physical properties namely the specific gravity and bulk density are relatively low and water absorbtion is high in comparison with that of the natural aggregates (NA). The quality of old adhered mortar in governing the increase or decrease in value specific gravity and water absorbtion. The size and quantity of old adhered mortar enveloping the recycling aggregate increases with the increase in the strength of parent concrete due to relatively higher bond between the aggregate and low density mortar phase. Therefore, results show that the higher quantity of

ÂŠ 2012 ACEE DOI: 02.ADCS.2012.1. 506

Full Paper Proc. of Int. Conf. on Advances in Design and Construction of Structures 2012 Bituminous mixes with varying dosages of binder bitumen are prepared. For different dosages of bitumen content 3 specimens are prepared and average values are taken. Marshall Test is conducted as per IRC specification and the stability of the mix is assumed. The optimum amount of binder is arrived at considering i) maximum stability ii) maximum density iii) median of designed limits of percent air voids in total mixture (4%).

TABLE I. PHYSICAL PROPERTIES OF THE AGGREGATES USED

B. Bitumen The type of bitumen plays a very important role in the performance of bituminous concrete mixes. For all studies conducted paving grade bitumen [VG-10] is used. Physical & engineering properties of bitumen are given in table (II).

Figure 1. Marshall Mould

Graphs of Marshall stability v/s percentage bitumen, flow value v/s percentage bitumen, unit weight v/s percentage bitumen, percentage air voids in the mixture v/s percentage bitumen and percentage air voids filled with bitumen v/s percentage bitumen are plotted for different mixes to understand the effect of replacement of natural aggregate with recycled aggregate in bituminous concrete surface course.

TABLE II. PHYSICAL PROPERTIES OF BITUMEN

TABLE III. IRC SPECIFIED GRADATION OF AGGREGATE FOR BITUMINOUS CONCRETE SURFACE COURSE [15][16][17]

TABLE IV. D ETAILS O F T HE MIXES TRIED

V. TESTING PROGRAM All materials used for the investigation are subjected to basic material testing to evaluate engineering and physical properties. Marshall Test is used to evaluate the effect of recycled aggregate in bituminous concrete surface course. The gradation used for testing is given in table (III) which is specified by IRC. Rothfutchâ&#x20AC;&#x2122;s method is used to obtain aggregates of desired gradation. Seven different mixes were tried C, M1, M2, M3, M4, M5, M6. The amount of natural aggregate was replaced by recycled aggregate in different proportions. The table (IV) gives in detail the quantity of natural and recycled aggregates in the mixture. ÂŠ 2012 ACEE DOI: 02.ADCS.2012.1. 506

Full Paper Proc. of Int. Conf. on Advances in Design and Construction of Structures 2012 VI. ANALYSIS OF TEST RESULTS

TABLE VIII. MARSHALL’S TEST RESULT FOR MIX M3

TABLE V. MARSHALL’S T EST RESULT FOR MIX C

TABLE IX. MARSHALL’S TEST RESULT FOR MIX M4 TABLE VI. MARSHALL’S TEST RESULT FOR MIX M1

TABLE X. MARSHALL’S TEST RESULT FOR MIX M5

TABLE VII. MARSHALL’ S TEST RESULT FOR MIX M2

Full Paper Proc. of Int. Conf. on Advances in Design and Construction of Structures 2012 TABLE XI. MARSHALLâ&#x20AC;&#x2122;S TEST RESULT FOR MIX M6

Figure 4. Unit weight v/s percentage bitumen

Figure 5. % voids in total mix v/s percentage bitumen

Figure 2. Marshall Stability v/s percentage bitumen

Figure 6. %voids filled by bitumen v/s percentage bitumen

Figure 3. Flow v/s percentage bitumen

ÂŠ 2012 ACEE DOI: 02.ADCS.2012.1. 506

Full Paper Proc. of Int. Conf. on Advances in Design and Construction of Structures 2012 TableXII. Marshall Properties Of Different Mixes At Optimum Bitu men Content

TABLE XIII. DESIRED MARSHALL MIX DESIGN CRITERIA FOR BITUMINOUS CONCRETE [IRC]

DISCUSSION & CONCLUSION  By implementing this technology, the amount of waste materials finding their way into landfills will be reduced through usage of recycled aggregate. This will therefore reduce the amount of quarrying thereby extending the life of natural resources thereby preventing the environmental degradation. Using recycled aggregates in the construction of bituminous concrete surface course is economically feasible. From table (I) containing the test results of the properties of the aggregates, it is apparent that all values are within the permissible limits prescribed for each test with the exception of water absorption, which appears to be higher than the limits. This is mainly due to the residual mortar coating to be found on the recycled aggregates which enhances water absorption. From table (II) containing the test results of the bitumen (VG-10) used, it is apparent that all values are within the permissible limits prescribed for each test. Recycled aggregates are found to be inferior to the natural aggregates With increase in recycled aggregate content, the Marshall Stability decreases. With increase in recycled aggregate content, optimum binder content increases. With increase in recycled aggregate content, dry density of bituminous concrete decreases. Air voids in mix is found higher in mixes containing more recycled aggregates. The efficiency of voids getting filled with bitumen decreases with increase in recycled aggregate content. From figure (2) to figure (6), it can be observed that the behaviour of the materials by varying percentage increase in bitumen content and replacement of natural aggregates, shows uniform curve characteristics regardless of the mix. As per table(XIII) recycled aggregates can be effectively replace natural aggregates by 20% as there is no significant reduction in Marshall stability & no large increase in binder content. Flow value at OBC reduces with higher replacement of natural aggregates by recycled aggregates. However, fatigue behaviour & durability studies need to be conducted before implementation.

Figure 7. Percentage loss in Marshall Stability with increase in replacement of natural aggregates

Figure 8. Percentage increase in bitumen content with increase in replacement of natural aggregates

Full Paper Proc. of Int. Conf. on Advances in Design and Construction of Structures 2012 REFERENCES

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