Full Text - rs publication

International Journal of Emerging trends in Engineering and Development Issue 2, Vol.4 (May 2012) ISSN 2249-6149

Study on Structural Characteristics of Bituminous Mix with Added Hydrated Lime and Phosphogypsum Savitha T Sudhakaran#1, R Satheesh Chandran#2, Dr M Satyakumar#3 #1

Traffic and Transportation Engineering, Kerala University Post Graduate Student in Civil Engineering Department, College of Engineering Trivandrum, India, 09961564302. #2 Traffic and Transportation Engineering, Kerala University Associate Professor In Department of Civil Engineering, College of Engineering Trivandrum, India, 09496172587. #3 Traffic and Transportation Engineering, Kerala University Professor In Department of Civil Engineering, College of Engineering Trivandrum, India, 09847223294.

___________________________________________________________________________

Abstract This paper describes investigation on study of structural characteristics of bituminous mix with added hydrated lime and phosphogvypsum. The objective of the experiment is to develop a mix design for bituminous mix with added hydrated lime and phosphogypsum and to evaluate structural characteristics of the bituminous mixes such as Marshall stability value, creep characteristics and Indirect tensile stiffness modulus value, a simplified mix design procedure was used for producing the bituminous mixes. Keywords - Marshall test, optimum bitumen content, fatigue test, static creep test ___________________________________________________________________________ Corresponding Author: Savitha T Sudhakaran

1.1 Introduction Flexible pavements are the most common pavement structure. The surface course of the structure is bituminous mixture, i.e. a mixture of graded aggregates (either well graded or gap graded) and bitumen (asphalt cement). Asphalt pavements are a crucial part of our nation’s strategy for building a high performance transportation network for the future. Asphalt construction is fast and relatively simple; it is economical, and the materials to make it are widely available. Hot mix asphalt can be optimized in many ways to create high performance pavement. Fillers are finely divided substances which are insoluble in bitumen but can’t be dispersed the mixtures in it and use as a means of modifying consistency and mechanical properties of bitumen. Typical mineral fillers are limestone dust, cement, hydrated lime, slate dust, pulverized fuel ash, talc, silica and asbestos. The general effect of adding filler to bitumen is to make it harder and stiffer. There is a reduction in the deformation produced by a given load, an increase in softening point, reduction in penetration and an increase in stiffness. The extent of this hardening or stiffening effect depends on the amount of filler added, its particle shape, size and grading.

1.1.1 Need For The Study In flexible pavement construction, bitumen is extensively used because of its, inherent cohesive nature, weathering resistance and ease of processing in the molten state as Page 73


waterproof coatings, sealant and as well as binders. Bitumen is exposed to a wide range of temperature and loading conditions. Pure bitumen is a viscous fluid at a temperature at about 30°C. It undergoes considerable deformation due to applied load over a period of time. This problem restricts its applications under conditions that warrant its use of extended period of time. Pure bitumen has very poor creep resistance and this is exacerbated at high temperatures and under sustained loads. Not only does the addition of lime provide anti stripping benefits, but it also acts as mineral filler to stiffen the asphalt binder and HMA, improves resistance to fracture growth at low temperatures, interacts with the products of oxidation to reduce their deleterious effects and improves moisture stability and durability. The objectives of the study are listed below 1. To develop a mix design for bituminous mix with added lime and phosphogypsum 2. To optimize binder content ,lime content and phosphogypsum content in the mix 3. To study the structural characteristics of the bituminous mixes such as Marshall Stability Value, Creep Characteristics and Stiffness Modulus.

1.1.2 Literature Review This presents research on the multifunctional benefits of hydrated lime and phosphogyosum in more detail. Research has been conducted throughout the world. The results of laboratory wheel tracking test conducted in Colorado and Georgia indicate that hydrated lime increases resistance to rutting and permanent deformation. [Aschenbrener and Far, (1994) and Collins et al., (1997)]. Creep tests in Texas show that hydrated lime promotes high temperature stability, thereby increasing resistance to rutting [Little (1994)]. Research studies conducted in the 1990s evaluated the impact of lime on the improvements in high temperature performance (rutting resistance), fatigue cracking resistance, and low temperature fracture [Little (1996), Lesueur et al. (1998), and Lesueur and Little (1999)]. Tayibi, et al., (2009), this paper reviews the different environmental impacts associated with phosphogypsum storage and disposal. The methods is to minimise the negative effects of this waste are classified by treatment type, i.e. physical, chemical, thermal, etc., and different suggested applications for phosphogypsum are given in detail.

2.1 Materials and method 2.1.1 General Materials used for study are phosphogypsum and lime. The materials used in the preparation of BC grade II include bitumen, coarse aggregate and fine aggregate. 2.1.2 Phosphogypsum Phosphogypsum collected from English Indian Clay at Veli region of Trivandrum district, Kerala state. The production of phosphoric acid from natural phosphate rock by the wet process gives rise to an industrial by-product called phosphogypsum. 2.1.3 Hydrated lime Hydrated lime used is free from organic impurities and have a plasticity index not greater than 4. The plasticity index requirement shall not apply if filler is cement or lime. Page 74


2.1.4 Bitumen The bitumen PG 60-70 collected from Hindustan Coals Limited, Mangalore Karnataka state was used in this study. The bitumen was tested in the laboratory. The physical characteristics such as penetration, softening point, ductility and specific gravity were evaluated as per IS: 1203-1987, IS: 1205-1978, IS: 1208-1978 and IS: 1202. 2.1.5 Aggregate Aggregate which possess sufficient strength, hardness, toughness, specific gravity and shape are chosen, which was collected from a quarry at Veliyam Panchayath in Kollam District, Kerala state. 2.1.6 Design of Bituminous Mix 2.1.6.1 Proportioning Of Aggregates Four samples including coarse aggregate, fine aggregate, quarry dust and filler are mixed in such a proportion which would produce a mix with highest density. In order to obtain the desired gradation the aggregate and filler should be mixed in certain definite proportion. IRC has recommended a specific gradation of aggregate for bituminous concrete mix. The aggregate gradation for bituminous concrete as per MORTH (Ministry of Road Transport and Highways) specification. 2.1.6.2 Aggregate Gradation For The Mixes The aggregate gradation of all the design mixes used in this investigation is based on MORTH Specifications for Roads and Bridge Works, 4th Revision. Table 1 Desired Aggregate gradation for bituminous concrete grade (MORTH Specification) IS Sieve Designation(mm) 19 13.2 9.5 4.75 2.36 1.18 0.6 0.3 0.15 0.075

Percentage Passing the Sieve by Weight 100 79 – 100 70 – 88 53 – 71 42 – 58 34 – 48 26 – 38 18 – 28 12 – 20 4-10

2.1.7 Optimum Binder Content The optimum asphalt binder content is finally selected based on the combined results of Marshall Stability, flow, Void and Density Analysis. Page 75


2.1.8 Determination of Optimum Lime Content The optimum lime content is determined by Marshall mix design method 2.1.9 Determination of Optimum Phosphogypsum Content The optimum phosphogypsum content is determined by Marshall mix design method 2.1.10 Static Creep Test In this test the compacted cylindrical specimen is subjected to uniaxial repeated load creep test and the permanent deformation is recorded using LVDT. The test conditions are summarized as follows: Loading Axial loading Test Stress 100KPa Conditioning stress 0.01MPa Conditioning period 600 s Test Period 1800 pulses (3600 Sec) Test temperature Room temperature, 300C Specimen diameter 100mm The data obtained from this test are initial strain, permanent strain, and creep rate in the final 1200 loading seconds, Stiffness Modulus. Stiffness Modulus is the ratio of vertical stress to the maximum strain. 3.1 Test Results This section deals with the results of various tests carried out to study the physical properties of aggregates and binder and the results of Marshall Stability test. 3.1.1 Properties of Materials 3.1.1.2 Aggregates The results obtained from various test are shown in the following tables 2 and 3. Table 2 Properties of Aggregate used for the study Properties

Coarse Aggregate

Aggregate Abrasion value (%)

3.68

Aggregate Impact value (%)

19.11

Aggregate Crushing value (%)

36

Water Absorption (%)

1.15

Specific gravity of aggregate

2.73

Angularity number

9

Page 76


Table 3 Properties of Bitumen used for the study Test Description Penetration value at 250C,1/10th of a millimetre Softening Point,0C Ductility ,cm Specific Gravity Flash Point,0C Fire Point,0C

Results 25 48 76 1.00 162 185

3.1.1.3 Physical properties of additive phosphogypsum The physical properties of additive phosphogypsum were determined and are shown in Table 4. Table 4 Physical properties of phosphogypsum Property Specific Gravity Maximum Dry Density Optimum Moisture

Values 2.62 1.533 – 1.733 g/cc 15-20%

3.1.1.4 Determination of Particle Size Distribution Dry sieve analysis tests were conducted for determining the particle size distribution of phosphogypsum and depicted in fig 1and it can be seen that % of sand and silt are 95.5% and 4.5 % respectively.

Fig 1 Grain size distribution curve for phosphogypsum

Page 77


3.1.1.5 Chemical properties of additive phosphogypsum The chemical properties of additive phosphogypsum were determined and are shown in Table 5. Table 5 Chemical properties of phosphogypsum (Source: English India clay,kerala state) Constituents Calcium Oxide (CaO) Sulphate (SO4-) Silica (SiO2) Aluminium Oxide (Al2O3) Iron Oxide (Fe2O3) Phosphorous Pentoxide (P2O5) Fluorine (F) pH

Amount (%) 32.5 53.1 2.5 0.1 0.1 0.65 1.2 2.6 - 5.2

3.1.1.6 Engineering Properties of additive phosphogypsum The engineering properties of additive phosphogypsum were determined and are shown in Table 6. Table 6 Engineering properties of additive phosphogypsum (Source: English Indian Clay) Property Friction Angle Cohesion Value

Value 32o 125

3.1.1.7 Optimum Binder Content The optimum asphalt binder content is finally selected based on the combined results of Marshall Stability and flow, density analysis and void.

Fig 2 Unit weight with percentage of bitumen Page 78


Fig 3 Marshall stability value with percentage of bitumen

Fig 4 Flow value with percentage of bitumen

Fig 5 Percentage airvoids with percentage of bitumen

Page 79


Fig 6 VFB (%) with percentage of bitumen Optimum Binder Content can be calculated as the average of the bitumen percentage corresponding to conditions given in the following Table 7. Table 7 Optimum bitumen content Property Marshal Stability (Kg) Maximum Unit Weight (gm/cc) 4 % Air Voids

OBC 5.5 6

Average OBC (%) 5.4

4.75

3.1.1.8 Optimum Lime Content Optimum Lime Content can be calculated as corresponding to conditions given in the following Table 8. Table 8 Optimum lime content Property Marshal Stability (Kg) Maximum Unit Weight

Lime Content at maximum value 3 3

Optimum Lime Content 3

3.1.1.9 Optimum Lime Content Optimum phosphogypsum Content can be calculated corresponding to condition given in the following Table 9.

Page 80


Table 9 Optimum phosphogypsum content

Property

phosphogypsum content at max value

Marshal Stability (Kg) Maximum Unit Weight (gm/cc)

3 3

Optimum phosphogypsum Content 3

3.1.1.10 Static Creep Test Results Static creep tests were performed on Hot Mix Asphalt which was added with hydrated lime & phosphogypsum as filler materials. The results obtained are as shown in the figures 7 to 9.

Fig 7 Axial strain with time (sec) (HMA without lime)

Fig 8 Axial strain with time (sec) (HMA with lime) Page 81


Fig 9 Axial strain with time (sec) (HMA with phosphogypsum) Table 10 Results of static creep Test Properties

Sample without Lime

Sample with Lime

Sample with phosphogypsum

Initial micro Strain Maximum micro Strain Permanent micro Strain Stiffness Creep Mpa

0.401573

0.347074

0.375650

1.035889

0.814815

0.932032

0.888680

0.682832

0.745896

9.65

12.27

10.73

Table 11 Results of fatigue and stiffness modulus of the mix Control

Sample with

Sample

mix

lime

phosohogypsum

Stability(KN)

9.87

13.20

11.75

Load repetition

750

985

828

Deformation

8.00

9.75

12.58

Stiffness modulus (MPa)

985.0

1175

1061.6

Properties

4.1 Conclusions  Optimum Binder Content(OBC) is 5.4% by weight of aggregate blend  Optimum Lime Content is 3% Page 82


 Optimum phosphogypsum Content is 3%  The stiffness modulus value is increased by 27% by the addition of 3% hydrated lime to the mix  The stiffness modulus value is increased by 11% by the addition of 3% phosphogypsum to the mix The main conclusion drawn from the investigation is;  Structural characteristics and stiffness modulus of the bituminous mixes can be enhanced by adding hydrated lime and phosphogypsum as filler materials The use of phosphogypsum in pavement construction reduces  Environmental problems related with the large stockpiles of phosphogypsum and their negative impact on surrounding land, water and air due to the radioactive elements in the phosphogypsum

References [1] Dallas N. Little., and Jon A. Epps. (2001), “The Benefits of Hydrated Lime in Mot Mix Asphalt” National Lime Association. [2] Degirmenci Nurhayat, (2008) “The Using of Waste Phosphogypsum and Natural Gypsum in Adobe Stabilization”, Construction and Building Materials, pp. 1220– 1224. [3] Degirmenci Nurhayat, Okucu Arzu, Turabi Ayse, (2007) “Application Of Phosphogypsum in Soil Stabilization”, Building and Environment Journal, pp.3393– 3398 [4] IRC 37-2001 “Guidelines for the Design of Flexible Pavements”, Indian Roads Congress, New Delhi. [5] Kadiyali, L.R., and Lal, N. B., (2003), “Principles and Practices of Highway Engineering (Including Expressways and Airport Engineering”, Khanna Publishers, Delhi, India [6] Khanna, S.K and Justo, C.E.G., (1990), “Highway Engineering”, New Chand & Brose, Roorkee, Edition No.6 [7] Lesueur, D., and Little, D.N. (1999), “Effect of Hydrated Lime on Rheology, Fracture and Aging of Bitumen,” Transportation Research Record No. 1661, pp. 93-105. [8] MORTH Specifications for Roads and Bridge Works, 4th Revision, (2001). Ministry of Surface Road Transport and Highways, Government of India, published by IRC

Page 83