Asphalt Pavement Evaluation Using Conventional and Ground Penetrating Radar Survey

A ThesisSubmitted for the practical fulfilment degree ofMaster of TechnologyInCivil Engineering(Transportation and Infrastructure Engineering)

Submitted byAnwar HussainM.Tech Transportation&Infrastructural ENGINEERINGSR NO: 05-05-06-10-41-13-1-10342

June-2015Department of Civil EngineeringIndian Institute of ScienceBangalore -560012

Acknowledgement

I would like to take this golden opportunity to express my deep sense of gratitude to Dr. P. Anbazhagan Assist. Professor, Department of Civil Engineering, Indian Institute ofScience, for his excellent supervision, illuminating guidance, constant encouragement, Immense support and active involvement in all phase of my work.

I am thankful to Mr. Nagesh. V, Mr. Sundar Raj, M.Tech scholars, Department of Civil Engineering, for their unconditional help, encouragement and support during my project work.

I express my deepest sense of gratitude and love towards my parents for their love, blessing, constant encouragement and extreme support in all my decisions.

I am grateful to the research student Mr. Deepu Chandran of the Geotechnical Engineering Department. He made a wonderful, friendly learning and working environment. I am alsothankful to the office and technical staff of Department of Civil Engineering, for theirco-operation.I am thankful to my batch mates Mr M.Deepak Kumar,Mr. Kiran Kumar for their helpand companionship.

Anwar Hussain

ABSTRACT

TABLE OF CONTENT

CHAPTER1: INTRODUCTION1.1 Background71.2 Problem of study81.3 Objective of study..91.4 Location of study...91.5 Scope of study...9CHAPTER2: LITERATURE REVIEW2.1 Flexible Pavement102.1.1 Flexible pavement structure..102.1.2 Cause of failure..112.1.3 Collapse of Flexible pavement...122.2 Deterioration of Flexible pavements..132.3 Pavement Distress..132.3.1 Cracks..132.3.2 Pavement defects.162.3.3 Pavement deformation.172.4 Ground Penetrating Radar(GPR)22CHAPTER3: METHODOLOGY3.1 PCI method263.2 Data requirement & Collection..263.2.1 Methodology of research.....273.3 Applications of GPR in pavements.613.5 GPR For Pavement Investigations..643.6 Future work.72CHAPTER4: PCI SURVEYCHAPTER5:GPR SURVEYCHAPTER6: DISCUSSION AND CONCLUSION

REFERENCES.72

APPENDIX A(List Of Figures)....73

APPENDIX B(List Of Tables)...

CHAPTER 1 INTRODUCTION

1.1 Background

Roads play a major role in the development of all countries and societies by providing the essential links between different parts of the country to facilitate the movement of people and transport of goods. The importance of roads increases as the area of the country increases, especially in the absence of other means of transport such as railways and waterways, which is often occurred in developing countries. The highway network is classified into four main roadway types 1- Expressways: Roads arteries outside municipal borders link the cities and regions with two carriage ways and at least four lanes (two lanes or more in each direction). 2- Main roads: Roadways linking cities and regions or serving cities within municipal boundaries, there are single carriageway roads for good paved standard or dual carriage ways with 2 lanes in each direction. 3- Secondary roads: These link district centres and villages.

4- Agricultural roads: Roads linking agricultural land and farms with markets. The weakness and lack of periodic maintenance programs and delayed repairs of the damage suffered by paving the roads in that there have contributed on functional and structural damage. It is difficult to maintain the road on the same specification that was owned at the opening and problems start to appear represented in the pavement cracks, holes and undulations and so on (Bashir, 2006). Many exposed pavements have problems lead to a reduction of the quality of the road and reduce the degree of safety and comfort to road users. Some of these problems occur in asphalt layers, such as cracks and bleeding, and some of the lower classes occur, such as crawl and swell. Studies and researches have been shown that most of the problems faced by asphalt roads in India linked mainly with hot, dry climate prevail in most areas. Most of the problems are various types of cracks, hardening, ravelling and weathering asphalt materials which are mainly due to a number of environment factors, namely: - High temperatures, especially in the summer. - The daily temperature range. - The intensity of solar radiation. Damage appears slowly at first, and then gradually accelerates, accumulating to become visible as structural distress and tangible as ride quality reduced. If distress is observed and corrected in a timely manner, low cost strategies will restore the road to nearly its original condition. However, if early treatment is neglected or postponed, the accumulated damage will require a more costly repair treatment. Recognizing that damage accumulation and acceleration is a key to understanding the need for early, low-level, low-cost preventive maintenance treatments.It is easy to see why pavements deteriorate at various rates and why we find them in various stages of disrepair. Recognizing defects and understanding their causes help us of evaluate pavement condition and select cost-effective repairs. The pavement defects shown on the following pages provide a background for this process. Periodic inspection is necessary to provide current and useful evaluation data. It is recommended that ratings be updated every year. Obviously, most pavement deterioration results from both environmental and structural causes. However, it is important to try to distinguish between the two in order to select the most effective rehabilitation techniques.

1.2 Problem of Study: Pavement deterioration is a result of complex distress as pavement cracking through fatigue under repeated loadings and environmental cycles; deformation of the pavement structure through shearing; and disintegration of materials when mechanical or chemical bonds are broken through weathering, infiltration, or loading. Underground conditions, structures, traffic characteristics, and environmental contexts all have a tremendous impact on the performance of highway pavements (Gary et al., 2009). Due to variations in construction and material quality, the age of a pavement structure may not accurately indicate the condition or the performance of the pavement. However, the age of the pavement may be used to further categorize pavement sections and may provide a relative condition of those sections (ADO, 1999). At the opening of the road, usually with high quality and specifications. But the passage of time and with the use of the road because of traffic loads applied on the road on a daily basis and continuous in addition air factors such as daily and seasonal rains and changes in temperatures, it is difficult to maintain the road on the same specification that was owned at the opening and problems start to appear represented in the pavement cracks, holes and undulations and so on (RLTA, 2010). Generally, good design does not prevent the occurrence of such defects in case of default in the construction or in the case of non-construction according to engineering specifications (cases of non-compliance with specifications) .The cost of maintenance expense exceeds the cost of construction itself because it was disrupting traffic generated by the delay in the establishment of these roads. Preventive maintenance is an essential tool for extending the life of a pavement. Used early in a pavement's life, preventive maintenance corrects small problems before they become big problems, saves money, reduces delays and improves safety and ride ability. Therefore profession engineer maintained until the roads are always safety ways and the movement for passengers or goods are a comfortable and economical at all times (Bashir, 2006). Not all pavement structures are constructed alike, nor do all pavement structures perform identically. Therefore, it is necessary to monitor the maintenance requirements of each general type of pavement. By monitoring the performance of pavement sections of similar construction and usage, sufficient information can be developed to forecast maintenance requirements (ADO, 1999).

1.3 Objective of Study: The key element to surface evaluation management programs is to identify the different types of pavement distresses and determine their causes. Knowing what caused the pavement distress allows the appropriate maintenance treatment to be applied (Lavin, 2003). Basic objective of this study is to i. Condition assessment of selected pavements in IISc campus using conventional approach by calculating Pavement Condition Rating (PCR) based manual survey.ii. Condition assessment of selected pavements in IISc campus using modern geophysical survey of Ground Penetration Radar(GPR)method.iii. Correlate pavement qualities with non-distractive tests results and evaluate limitation and advantage of modern GPR survey for pavement quality assessment.

1-4 Location of Study: The field work carried out in IISc campus road network for the pavement condition survey and GPR survey, Frequently using roads in the campus which have chosen and selected 7 major roads have selected for the study area which are Badam Marg, Madhuka Marg, Mahogany Marg, Bank Road, Near R-Block Road, Near SERC RoadThe survey was carried out on above roads and tries to find possible number of distress and analysis of those distresses for our objectives.1-5 Scope of Study:

Improving and maintenance of transportation infrastructures is a major task in any urban city in India. These transportation facilities are playing a major role in infrastructure development, economical growth and people/industrial agglomerations. Most of the urban centres are improving transportation infrastructures, in particular, roads by better maintenance and augmentation, rather than new construction. In general, maintenance of road network in city/urban centre consumes almost 80% of cost in total transportation infrastructure expenditures. This may be due to the lack of scientific/technical knowledge for road condition assessment, maintenance and repairs. Road maintenanceis a major issue in Indian cities.In this study, an attempt has been made to evaluating the existing pavement section by field and GPR experiment and there by assessing the condition for better maintenance and repair work. 7 different road conditions are selected in the IISc campus, these locations are inspected visually and PCR is evaluated as per conventional ASTM D6433 pavement condition assessment. In these 7 locations non-destructive field experiment of GPR survey has been carried out.

CHAPTER 2

Literature review

Pavement Condition assessment is mandatory step before overlay and reconstruction in the developed countries. But condition assessment is rarely practice for Indian roads before overlay and reconstruction. Very popular road condition assessment methods are Pavement Condition Rating (PCR) and result using non-destructive tests. This chapter review pavement condition assessment method by ASTM D6433 standard procedure for pavements and parking lots and non-destructive testes. PCR is a conventional pavement evaluation system by considering distress of pavement section by carrying out visual survey. Pavement sections will be rated based PCI(Pavement Condition Index) ranging from 0 to 100 scale.The survey was carried out on flexible pavements in the campus, Flexible pavements are so named because the total pavement structure deflects, or flexes, under loading. A flexible pavement structure is typically composed of several layers of material each of which receives the loads from the above layer, spreads them out and then passes them on to the layer below.A typical flexible pavement structure (Figure 2.1) consists of the surface course and the underlying base and subbase courses. Each of these layers contributes to structural support and drainage. The surface course (typically an HMA layer) is the stiffest (as measured by resilient modulus) and contributes the most to pavement strength. The underlying layers are less stiff but are still important to pavement strength as well as drainage and frost protection.

Figure 2.1 Basic flexible pavement structure (Haffman, 2008)

Many non-destructive tests are used for condition assessment of pavements. In this study GPR will be used, hence these two methods with case study is discussed in this chapter. Ground penetrating radar is a non-destructive electromagnetic method that produces a continuous cross-sectional profile or record of subsurface features, without drilling, probing, or digging. GPR profiles are used for evaluating the pavement and location and depth of buried objects and to investigate the presence and continuity of natural subsurface conditions and features.

2.3 Pavement Condition Rating (PCR):Pavement Condition Rating (PCR) identifies various types of pavement distress for the pavement types and provides each distress overview and rating for pavement condition. The rating method used is based upon visual inspection of pavement. The rating method provides a procedure for uniformly identifying and describing, in terms of severity of the distress. The PCR is a numerical rating on a scale of 0 to 100 that is determined based on measured distress types, quantities and severities.The PCI provides a measure of the present condition of the pavement based on the distress observed on the surface of the pavement, which also indicates the structural integrity and surface operational condition (localized roughness and safety). The PCI cannot measure structural capacity nor does it provide direct measurement of skid resistance or roughness. It provides an objective and rational basis for determining maintenance and repair needs and priorities. Continuous monitoring of the PCI is used to establish the rate of pavement deterioration, which permits early identification of major rehabilitation needs. The PCI provides feedback on pavement performance for validation or improvement of current pavement design and maintenance procedures.pavement condition ratinga verbal description of pavement condition as a function of the PCI value that varies from failed to Very Goodpavement distressexternal indicators of pavement deterioration caused by loading, environmental factors, construction deficiencies, or a combination thereof. Typical distressesare cracks, rutting, and weathering of the pavement surface. Distress types and severity levels detailed in Chapter4.

2.4 Non-Destructive Tests for Pavement Evaluation:Numbers of non-destructive tests are used to test functional and structural properties of the pavement. This section presents review of non-destructive testing to evaluate pavement functional properties and structural properties. Pavements non-destructive tests can be broadly divided into several categories: Nuclear Equipment Deflection based Equipment Electromagnetic equipments and Seismic Equipments Infrared thermography (IRT)Selection of particular non-destructive testing method is based on cost, time and availability of equipment.Nuclear Equipment - A nuclear density gauge measures in-place HMA density using gamma radiation. Gauges usually contain a small gamma source (about 10 mCi) such as Cesium-137 on the end of a retractable rod. Gamma rays are emitted from the source and interact with electrons in the pavement through absorption, Compton scattering and photoelectric effect. A Geiger-Mueller detector (situated in the gauge opposite from the handle) counts gamma rays that reach it from the source. Pavement density is then correlated to the number of gamma rays received by the detector. Nuclear density gauges are typically operated in one of two modes, each of which uses a different correlation to determine pavement densityDeflection Based Equipment- Pavement surface deflections have been used in the past as an indicator of the pavement life. Pavement surface deflection measurements are the primary means of evaluating a flexible pavement structure and rigid pavement load transfer. Although other measurements can be made that reflect (to some degree) a pavement's structural condition, surface deflection is an important pavement evaluation method because the magnitude and shape of pavement deflection is a function of traffic (type and volume), pavement structural section, temperature affecting the pavement structure and moisture affecting the pavement structure. Deflection measurements can be used in back calculation methods to determine pavement structural layer stiffness and the subgrade resilient modulus. Widely used deflection instruments are Benkelman beam and Falling, Weight Deflectometer (FWD) or dynaflect and Multi Depth Deflectometer(MDD).Benkelman Beam TestThe Benkelman beam test procedure involves the measurement of pavement surface rebound with a cantilevered beam when a truck loaded to 8180 kg on its rear axle moves from rest. Measurements are made between the dual tires on the rear axle at specified intervals in the outer wheel path and are then corrected for temperature and seasonal variation. The corrected rebound values are used in a statistical manner to determine a most probable spring rebound (MPSR). The MPSR value, a specified design rebound and traffic number are used to enter a design chart (based on an accumulated experience on similar roads) to determine the overlay required to extend pavement life to 20 years. This test is fast, simple and inexpensive. However, it does not provide thickness information and must be accompanied by other tests that provide this information. In general, Benkelman beam tests are performed on an overlay is the preferred rehabilitation strategy.Multi-depth Deflectometer (MDD)The multi-depth deflectometer (MDD) is used to measure depth deflection profiles of pavement; effective elastic moduli of multi-layered pavement structures can be back calculated from these measurements. The MDD consists of a series of up to six linear voltage differential transducers (LVDTs) installed vertically into the pavement at preselected depths in a relatively small-diameter hole. Resilient depth deflections are measured with the MDD used in association with a moving load. A major limitation of this method is that it requires a trench immediately adjacent to the pavement section of interest to ensure the effective placement of modules.Falling Weight Deflectometer (FWD) or dynaflect.The dynaflect and Falling Weight Deflectometer are tools that measure surface deflection. In this technique, a number of geophones are used to determine the static deflection basin resulting from a vertical impact. A back-calculation procedure is then used to infer the thickness and resilient modulus of the constituent layers of the pavement structure. Due to the nature of the back-calculation algorithm, reliable layer thickness information is required to control the inversion process. Thus supplemental coring or road radar tests are required.In this study, modern geophysical non-destructive tests of electromagnetic method is used. Literature of the method is given below:Infrared thermography (IRT)Infrared thermography (IRT) employs an infrared scanner to capture the thermal image fromthe top of the pavement, capturing temperature differentials. Typically, scanners can detect differences as small as 0.1C. The subsurface defects affect the heat flow within the pavement, and this in turn affects the temperature distribution of the concerned area. In most cases, this method can capture the location and extent of sub-surface distresses in the form of cracking, segregation, ageing, and construction non-homogeneity The delaminated or debonded sections are thinner than the surrounding sound area. With the same input of solar energy, these sections heat and cool faster than the adjacent pavement.The IRT is able to detect this temperature difference, and the flawed sections can be identified. The various field conditions represent the major drawback of this method. Certainenvironmental, such as time of testing, cloud cover, wind flow, pavement surface texture, solar radiation, and sub-surface conditions (moisture, frost penetration), conditions can affectthe test results.

2.5 Ground Penetrating Radar (GPR)Ground-penetrating radar(GPR) is ageophysicalmethod that usesradarpulses toimagethe subsurface. This non-destructivemethod useselectromagnetic radiationin themicrowaveband(UHF/VHFfrequencies) of theradio spectrum, and detects the reflected signals from subsurface structures. GPR can have applications in a variety of media, including rock, soil, ice, fresh water, pavements and structures.Basic principle of GPRA GPR system consists of a few components, as shown in Fig.2.21,that emit an electromagnetic wave into the ground and receive the response. If there is a change in electric properties in the ground or if there is an anomaly that has different electric properties than the surrounding media, a part of the electromagnetic wave is reflected back to the receiver. The system scans the ground to collect the data at various locations. Then a GPR profile can be constructed by plotting the amplitude of the received signals as a function of time and position, representing a vertical slice of the subsurface, as shown in Fig. 2. The time axis can be converted to depth by assuming a velocity for the electromagnetic wave in the subsurface soil.

Fig.2.2 Block diagram of a GPR system

Components of Typical GPR EquipmentThe first step in choosing a GPR system is to understand the main components the system. The typical GPR system is comprised of five main components that interface and communicate with each other depending on their respective functions. The physical location of each of these components is dependent on the system and application, and in some cases two or more components may be combining in the same physical unit. The anatomy of typical GPR equipment is shown in Figure 2.3.Encoder: The Encoder is generally a mechanical device, such as a wheel, that is used to measure distance along the target area and initiates a triggering pulse for the radar signal at predetermined distances. In some cases, a GPS is used in the Encoder to determine location and distance for triggering.A/D Converter: The A/D Converter forms the interface between the Antennas and theControl Unit converting signals from analog to digit and visa-versa depend on the direction. A/D Converter also connects to the Encoder from where it receives information about when to trigger a pulse. The A/D converter is referred to as Electronic Unit(s).Monitor/PC: The monitor or PC is used to visualize the GPR information in real time and to operate the system. Depending on the type of monitor, or if a PC is used, GPR data can be storage for later processing.Control Unit: The Control unit is the brain center for the GPR system and is responsible for coordinating the operation of the subordinate components.Antennas: While the Control Unit is performing the functionality of the brain and Antennas are the legs, doing the work of transmitting radar signals and receiving the reflected waves. As a general rule, the frequency of the antenna determines the depth of penetration and the resolution the higher the frequency the better the resolution but at the expense of the depth of penetration.

GPR Antennas Used for Study:The study has been carried out with MALA 800 MHz Shielded Antenna. The shielded 800MHz antenna delivers very good resolution for shallow investigations. Commonly used for road mapping and concrete investigations. The interchangeable electronics make the 800MHz antenna an economically good alternative than high resolution 100MHz antenna. The antenna Specifications are given below:Dimensions: 0.38*0.20*0.12mWeight: 2.6KgCentre frequency: 800MHzDepth Range: 0-2.4mWavelength /mm : 142Resolution /mm: 71

Fig.2.6. 800MHz Shielded Antenna

GPR Hardware:GPRs techniques are based on travel time and amplitude measures of the reflected wave of a short electromagnetic impulse transmitted through the pavement structure and successively reflected at the interfaces between layers. These interfaces are detected when the GPR wave match different materials, water content or density variation, etc. The GPR system has generally three components: A generator that creates a single impulse of a given frequency and power. Antenna(s) for emit the impulse through the media and capture the reflected signal. A computer that digitalizes the received signal (sampling) and convert it into a format that can be processed.Common radar antennas are divided into two categories: air-launched and ground-coupledAntenna.Ground-coupled antenna:This type works at a centre frequency that is in the 80-1500MHz range. Its main advantage is the greater depth penetration, in comparison with the another category. The scan speed is also low, between 5 and 15 km/h. So we can acquire data at very good quality. The current study has been carried out with 800MHz ground coupled antenna.

Typical GPR Equipment with Ground Coupled AntennaGPR SoftwareThe software available for road scan can be classified in four groups: Data acquisition unit Data elaboration unit (signal processing) Data visualization and interpretation unit Project and integrated analysis for the road unitGPR data was analysed in the RADEXPLORAR software which is developed by MALA Group and the routines will be applied to the GPR radar gram image for better visualization of the image.

Typical GPR image from a road survey

2.6 GPR Applications In Pavements:GPR has been used successfully in a variety of roadway applications, including: (1) measuring layer thickness of asphalt pavements and granular base layers; (2) estimating asphalt densities; (3) determining moisture content of base materials; (4) identifying stripping zones in asphalt layers; (5) detecting buried objects such as metal pipes and near-surface bedrock.Layer Thickness CalculationUsing the amplitudes (volts) and time delays (ns) from pulse figure it is possible toCalculate layer dielectrics and layer thickness. The equations used are summarized below:h=wherea = the dielectric of the surfacing layerc = speed of EM wave in airh=thickness of the layer t1 = the time delay between peaks, A1 and A2

where A1 = the amplitude of surface reflection; and Am = the amplitude of reflection from a large metal plate in volts

Material

Dielectric ConstantPropagation Velocity (m/ns)

Air10.3

Ice (Frozen soil) 40.15

Granite 90.1

Limestone 60.12

Dry sand 4 to 60.12 to 0.15

Wet sand 300.055

Asphalt 3 to 60.12 to 0.17

Concrete 9 to 120.087 to 0.10

Water 810.033

Dielectric Constants and Propagation Velocities of Pavement Materials

Soil moisture and frost susceptibility:

CHAPTER 3

METHODOLOGY3.1 PCI Method

The PCI is a numerical indicator that rates the surface condition of the pavement. The PCI provides a measure of the present condition of the pavement based on the distress observed on the surface of the pavement. It provides an objective and rational basis for determining maintenance and repair needs and priorities. Continuous monitoring of the PCI is used to establish the rate of pavement deterioration, which permits early identification of major rehabilitation needs. The PCI provides feedback on pavement performance for validation or improvement of current pavement design and maintenance procedures (ASTM D6433, 2007). PCI values range from 100 for a pavement with no defects to 0 for a pavement with no remaining functional life. The index is useful in describing distress and comparing pavements on an equal basis. ASTM standard contains information on PCI surveys. The FAA recommends that roads follow ASTM D 6433, Standard Test Method for road Pavement Condition Index Surveys (ASTM D6433, 1999). ASTMs manual is prepared to assist user of the Pavement Management System (PMS) in identifying surface distress in a uniform and repeatable manner. The distresses included in this manual are used to calculate the Pavement Condition Index (PCI) for pavements surfaced with asphalt concrete and surface treatments.This practice covers the determination of roads and parking lots pavement condition through visual survey using the Pavement Condition Index (PCI) method of quantifying pavement condition. The PCI for roads and parking lots was developed by the U.S Army Corps Engineers (ASTM D6433, 1999). 3.1.1 Data requirement The type of data collection is primary data from the field, as known the part was taken by a length of road. Recorded data for each type, calculated the area affected and recorded in special tables. And took a picture of each distress and level of severity. The data collected using survey method by minimum 2 persons. The data requirement for this study is Type and severity levels of distress. Data collection equipment:1. Data Sheets: for recording the following information: Date, location, section, distress types, severity levels, quantities, and names of surveyors. 2. Digital Camera: for take some photos. 3. Layout Plan, for network to be inspected. 4. Safety equipment.

3.1.2 Pavement Condition Survey A manual survey is performed following ASTM D 6433. The pavement was divided into sections. Each section was divided into sections. The type and severity of sample distress was assessed by visual inspection of the pavement sample units and the quantity of each distress was measured. Typically, this procedure requires a team of at least two engineers.Calculation of PCI for Asphalt Concrete (AC) Pavement ( ASTM standard D 6433): 1. Inspect sample section, determine distress types, severity levels and measure density:

Add up the total quantity of each distress type at each severity level, and record them in the "Total Severities" section. The sections for the quantities may be either in square feet (square meters) or number of occurrences, depending on the distress type

2. Divide the total quantity of each distress type at each severity level by the total area of the sample section and multiply by 100 to obtain the present density of each distress type and severity. 3. Determine the deduct value (DV) for each distress type and severity level combination from the distress deduct value curves in ASTM standard D 6433, as show in figure 3.01 deduct value curves for asphalt for Alligator Cracking.

Fig.3.01 Deduct values for Alligator cracking (ASTM standard D 6433)

4. Determine the maximum Corrected Deduct Value (CDV). The procedure for determining maximum CDV from individual DV is identical for both AC. 5. The following procedure must be used to determine the maximum CDV: a. If none or only one individual deduct value is greater than two, the total value is used in place of the maximum CDV in determining the PCI; otherwise, maximum CDV must be determined using the procedure described in ASTM standard D 6433. b. List the individual deduct values in descending order. c. Determine the allowable number of deducts, m, from Figure 3.02. or using the following formula in ASTM standard D 6433: m=1+(9/98)(100-HDV)