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From page 6... ... 6This chapter presents the results of the survey conducted to determine the density of asphalt pavements. Each question in the survey is highlighted followed by the background information, survey results, and an analysis of the results. Read the entire page →
From page 7... ... Survey to Determine the Density of asphalt pavements 7 flow chart illustrating how these factors affect the desirable properties of the asphalt concrete mixture in-place. The Guide to Asphalt Paving (2016) Read the entire page →
From page 8... ... 8 Specifying and Measuring asphalt pavement Density to ensure pavement performance Background With the list of factors in Table 1, it is easy to understand the complexity of the process for achieving density. With so many elements required for success in achieving density, it is easy to understand how things can and do, at times, go wrong. Read the entire page →
From page 9... ... Survey to Determine the Density of asphalt pavements 9 Survey Question 3 Is not achieving density a routine problem for your organization? Background Concerns are often expressed by agencies about achieving proper density in asphalt pavements and, commonly, the concern is with the density being too low. Read the entire page →
From page 10... ... 10 Specifying and Measuring asphalt pavement Density to ensure pavement performance Survey Question 5 Do you think that under-compaction of an asphalt mixture (high in-place voids) creates pavement performance problems? Read the entire page →
From page 11... ... Survey to Determine the Density of asphalt pavements 11 The Asphalt Pavement Alliance has defined these long-lasting pavements as perpetual pavements. The definition is "an asphalt pavement designed and built to last longer than 50 years without requiring major structural rehabilitation or reconstruction, and needing only periodic surface renewal in response to distresses confined to the top of the pavement" (Newcomb, 2002) Read the entire page →
From page 12... ... 12 Specifying and Measuring asphalt pavement Density to ensure pavement performance Table 5. Types of specifications for pavement construction. Read the entire page →
From page 13... ... Survey to Determine the Density of asphalt pavements 13 The current definitions for quality assurance elements from TRB are as follows (Transportation Research Circular E-C173) : Quality assurance (QA) Read the entire page →
From page 14... ... 14 Specifying and Measuring asphalt pavement Density to ensure pavement performance Survey Analysis Not surprisingly, all 100 respondents indicated that their agency had a density specification requirement. Approximately 60 percent of the respondents waive the density requirement for thin-lift applications. Read the entire page →
From page 15... ... Survey to Determine the Density of asphalt pavements 15 Composite Pay Factor. A factor obtained from two or more quality characteristics, to be multiplied by the bid price to determine the contractor's final payment for a unit of work. Read the entire page →
From page 16... ... 16 Specifying and Measuring asphalt pavement Density to ensure pavement performance and acceptance databases. The study was based on 5,598 data points (from 2004 and 2005) Read the entire page →
From page 17... ... Survey to Determine the Density of asphalt pavements 17 • Percentage of the JMF Gmm can change from mix design to production due to, among other factors, variations in specific gravity or gradation of the aggregates and absorption of the aggregate that may result in higher air voids. • Lab-compacted plant mix can be variable as mix properties change, thereby changing the target density. Read the entire page →
From page 18... ... 18 Specifying and Measuring asphalt pavement Density to ensure pavement performance lab density from the gyratory mix design, and the density of the lab-compacted plant mix from the gyratory mix design. Survey Question 7 Where is the reference density sample obtained? Read the entire page →
From page 19... ... Survey to Determine the Density of asphalt pavements 19 12 percent of respondents indicated the sample was taken at the plant discharge location while 6 percent reported sampling from a truck at the paver. Two respondents indicated taking a sample either in front of the screed or from the paver/material transfer vehicle hopper. Read the entire page →
From page 20... ... 20 Specifying and Measuring asphalt pavement Density to ensure pavement performance may have been done months or even years in advance of the project. Read the entire page →
From page 21... ... Survey to Determine the Density of asphalt pavements 21 Survey Question 11 Do your percent density specification requirements vary for different material products? Background Participants were asked if percent density requirements varied by mix type, neat versus polymer-modified binder, large stone versus small stone mixes, and mix design procedure. Read the entire page →
From page 22... ... 22 Specifying and Measuring asphalt pavement Density to ensure pavement performance As shown in Table 9, 89 percent of respondents had a lower specification limit between 91 and 93 percent density, with 57 percent of the respondents indicating a lower specification limit of 92 percent. The overall average of responses was a lower limit of 91.3 percent density. Read the entire page →
From page 23... ... Survey to Determine the Density of asphalt pavements 23 engineering material property of the in-situ mixture. However, as with any procedure, there can be variations in the coring operation that can lead to erroneous density results, such as mishandling of the sample, poor sample locations, or mislabeling of samples. Read the entire page →
From page 24... ... 24 Specifying and Measuring asphalt pavement Density to ensure pavement performance commonly used, 13 indicated that the thin-lift gauge was commonly used, and 5 indicated that the electromagnetic gauge was commonly used for acceptance testing. Survey Question 2 How does your organization ensure the core is dry before testing? Read the entire page →
From page 25... ... Survey to Determine the Density of asphalt pavements 25 process needs to be implemented. Historically, this value has been a limiting value of 2 percent (ASTM D2726, AASHTO T166) Read the entire page →
From page 26... ... 26 Specifying and Measuring asphalt pavement Density to ensure pavement performance strong consensus on potential other exceptions. Comments included a concern about core locations over known underlying pavement defects such as milling scabs, PCC (Portland cement concrete) Read the entire page →
From page 27... ... Survey to Determine the Density of asphalt pavements 27 Survey Analysis As shown in Table 14, the survey indicated that only 84 percent of respondents perform the critical step of correlation to a core density. About 54 percent and 40 percent perform calibration and standardization procedures, respectively. Read the entire page →
From page 28... ... 28 Specifying and Measuring asphalt pavement Density to ensure pavement performance • Minimum 3 cores per day, • 4, 5, or 6 sublots per lot, • Daily/one shift lot, • 500, 600, or 750 ton sublots, and • No coring except to correlate gauge. Survey Question 8 What is the frequency for NDT for determination of in-place density? Read the entire page →
From page 29... ... Survey to Determine the Density of asphalt pavements 29 Background A larger sample inherently produces a more representative test result. The volume of mix for a 6 in. Read the entire page →
From page 30... ... 30 Specifying and Measuring asphalt pavement Density to ensure pavement performance Quality measures are any one of several mathematical tools that are used to quantify the level of quality of an individual characteristic. Typical quality measures used in the asphalt industry are average, standard deviation and PWL or percent defective (PD) Read the entire page →
From page 31... ... Survey to Determine the Density of asphalt pavements 31 Survey Analysis As shown in Table 17, 54 percent of respondents indicated that PWL (or PD) quality measures were employed for acceptance. Read the entire page →
From page 32... ... 32 Specifying and Measuring asphalt pavement Density to ensure pavement performance the first sieve that had 100 percent of the material passing. The definition of NMAS was changed with the implementation of Superpave and now includes aggregate particles at the NMAS. Read the entire page →
From page 33... ... Survey to Determine the Density of asphalt pavements 33 is essentially standing on a vibrating platform. The operator often finds this situation to be uncomfortable and may even turn the vibrator off. Read the entire page →
From page 34... ... 34 Specifying and Measuring asphalt pavement Density to ensure pavement performance Survey Analysis According to the survey, 84 percent of the respondents indicated that the roller pattern is established by using one of the NDT technologies. Many respondents used the "comment" box to say that the roller pattern establishment was the choice of the contractor, which would likely increase that percentage. Read the entire page →
From page 35... ... Survey to Determine the Density of asphalt pavements 35 inspector was present to ensure that the roller pattern was followed. Typically, the inspector did not direct the process but verified and reported the process. Read the entire page →
From page 36... ... 36 Specifying and Measuring asphalt pavement Density to ensure pavement performance Survey Question 7 How many rollers are in your typical operation? What type of rollers are typically used? Read the entire page →
From page 37... ... Survey to Determine the Density of asphalt pavements 37 performing the same function as the DDS roller. A few respondents indicated the use of a combination roller with front drum and rear pneumatic either as an intermediate or finish roller. Read the entire page →
From page 38... ... 38 Specifying and Measuring asphalt pavement Density to ensure pavement performance Survey Analysis As high as 92 percent of the respondents indicated that the contractor made the decision about the roller type, although many agencies have a list of approved equipment that is acceptable for use, generally based on past experience. One exception noted by several respondents is that the type of roller used on a bridge deck was often specified by the agency (not a DDV roller) Read the entire page →
From page 39... ... Survey to Determine the Density of asphalt pavements 39 Survey Analysis Of the 97 respondents, 76 percent do not verify the weight of the roller. A total of 11 agencies (18 percent) Read the entire page →
From page 40... ... 40 Specifying and Measuring asphalt pavement Density to ensure pavement performance Since its relatively recent beginning in 2002, WMA has grown to occupy approximately onethird of the total U.S. market. Read the entire page →
From page 41... ... Survey to Determine the Density of asphalt pavements 41 all mix properties. The major difficulty in producing asphalt concrete is that it must be accomplished under extremely variable conditions (Warren, 1996) Read the entire page →
From page 42... ... 42 Specifying and Measuring asphalt pavement Density to ensure pavement performance requirements are a relatively new type of specification but are seen to be increasing in usage throughout the country. Despite extensive research and training activities, Buncher and Rosenberger (2012) Read the entire page →
From page 43... ... Survey to Determine the Density of asphalt pavements 43 to the cold side and not "bumped back" as is often done. When rolled, there is a white stripe of crushed aggregate that occurs on the cold side. Read the entire page →
From page 44... ... 44 Specifying and Measuring asphalt pavement Density to ensure pavement performance In the survey, 81 percent of the respondents (i.e., 89 percent of agency respondents) indicated that their joint density requirement was the same for all projects. Read the entire page →
From page 45... ... Survey to Determine the Density of asphalt pavements 45 for the agency. For agency respondents only, 58 percent responded that joint density specifications were in the standard specifications of their organization. Read the entire page →
From page 46... ... 46 Specifying and Measuring asphalt pavement Density to ensure pavement performance Survey Question 1 Is Intelligent Compaction (IC) being used in your jurisdiction? Read the entire page →
From page 47... ... Survey to Determine the Density of asphalt pavements 47 Background Reports by Gallivan et al. Read the entire page →
From page 48... ... 48 Specifying and Measuring asphalt pavement Density to ensure pavement performance process" (Guide to Asphalt Paving, 2016) Read the entire page →

From page 6...

... 6This chapter presents the results of the survey conducted to determine the density of asphalt pavements. Each question in the survey is highlighted followed by the background information, survey results, and an analysis of the results.