|Quick Links: Feature Article Pavement Guide Asphalt Video Asphalt Fact HAPI Calendar Previous Issues|
|A word from Jon M. Young, Executive Director|
In this month’s issue we feature guest columnist Danny Gierhart’s article titled Lead by Your Sample. Gierhart is the Asphalt Institute’s Senior Regional Engineer serving AL, AR, FL, LA, MS, OK, and TX. In 2018, HAPI was contracted by the Hawaii Department of Transportation to conduct their asphalt sampling refresher course and certification exam. Click here to go to our feature article and learn about representative sampling of asphalt binder, aggregate, and plant mix.
|(back to top)|
Featured Article - Lead by Your Sample
A critical part of any Quality Control (QC) or Quality Assurance (QA) program is the sampling procedure. Unfortunately, if a sample is obtained that is not representative of the material used on the project, the subsequent testing and analysis becomes irrelevant at best and costly at worst. It is a good idea to periodically review the fundamentals of correct sampling procedures to ensure that the materials used can be properly characterized.
Several pieces of information need to be collected before sampling in the field:
• What documented method is required to obtain the sample?
• Where are the approved locations for sampling?
• What equipment will I need to obtain and transport a proper material sample?
• How should I document the sample?
This article will first discuss random sampling, then cover more specifics regarding sampling of three material types: asphalt binder, aggregate, and plant mix.
A key component of obtaining a representative sample of any construction material is the concept of random sampling. Random means that all parts of the lot of material have an equal chance of being included in the sample. Over time, this method will statistically provide the clearest picture of the material. It will avoid bias due to, for example, repetitive patterns such as shift changes in production. Other sources of bias can include things like equipment operator bias and changes incurred due to equipment cycling on and off at regular intervals.
Two nationally-recognized standards for sampling asphalt binder are AASHTO R 66 and ASTM D 140. The basic procedure is the same for both standards with minor differences in wording and allowable sample sizes.
Asphalt binder can be sampled at several different places. In Hawaii, the sample is typically taken from line between storage tank and mixing drum when plant is running. At refineries, a combined sample is typically taken from sampling valves located at the top, middle, and lower locations of the storage tank.
Safety should always be kept in mind when sampling asphalt binder. Appropriate personal protective equipment such as face shields, sleeves, and gloves must be worn when obtaining samples. Although binder can be sampled quite safely, a lapse of attention or judgment can result in serious burns.
Two nationally-recognized standards for sampling aggregates are AASHTO T 2 and ASTM D 75. These standards are virtually the same.
A viable option is to sample the aggregate from a conveyor belt. In this case, templates conforming to the shape of the conveyor are required. Space the templates so that the material between them equals the desired size (1/3 of the total sample size if obtaining 3 increments). It is important to use a whisk or similar tool to obtain 100% of the material between the templates. A common drawback to sampling from the conveyor belt is that production must be halted to obtain the sample. However, several manufacturers now produce devices that will obtain a belt cut from moving, loaded conveyor belts.
If samples must be obtained from a stockpile, there are ways to increase the probability of obtaining a representative sample. The best option is to make a smaller sampling pile, often called a “power pile.” This is done by scooping aggregate from the main pile in various locations and elevations around the pile using a front-end loader and creating the sampling pile. The sample can then be blended from several samples taken at various increments from the sampling pile.
The two nationally-recognized standards for sampling aggregates are AASHTO T 168 and ASTM D 979. These standards are virtually the same, with the AASHTO standard have a few extra provisions. The three most common acceptable sampling points are:
• Sampling from a truck transport (uncompacted)
• Sampling from the roadway prior to compaction (uncompacted)
• Sampling from the roadway after compaction (cores)
Samples from a truck transport are more representative of the material as produced by the plant. QC personnel may prefer this location because the data allows for more reliable adjustments to the plant. However, samples from the roadway are more representative of the final product and may be preferred by QA personnel.
The most common method of obtaining a sample from the roadway after compaction is through a coring operation. It is critical to minimize disturbance to the material. This is usually accomplished by wet-cutting with diamond-studded core barrels. The removed cores must be handled carefully because they are susceptible to damage from heat and point loads.
In summary, a good sampling program obtains material that is representative of what is being used. Using an accepted sampling method builds confidence in the quality of the sample, and proper documentation ensures the integrity of the program.
|(back to top)|
|Asphalt Pavement Guide Highlight|
What is quality? In its broadest sense, quality is a degree of excellence: the extent to which something is fit for its purpose. In the narrow sense, product or service quality is defined as conformance with requirement, freedom from defects or contamination, or simply a degree of customer satisfaction. Click here to learn more about the quality assurance for asphalt pavements.
|(back to top)|
|Asphalt Video of the Month|
This video about asphalt quality control looks at the technology and testing that lies behind the scene of producing a quality road surface. Ensuring that the asphalt mix continually meets specifications really is an exact science! Click here for a brief introduction to the job of a quality control (QC) technician.
|(back to top)|
Visit www.asphaltfacts.com for interesting facts about asphalt. This monthly feature will no longer be included in our newsletter, but we encourage everyone to keep exploring the FACTS on the economic benefits of choosing asphalt pavements, finding the FACTS on the benefits of Perpetual Pavements through engineering and sustainability; reviewing the FACTS as to why smoothness really does matter; and getting the FACTS on how Asphalt is sustainable.
✤ HAPI Lunch Meeting, January 11, 2019; Honolulu, HI
Other events and training opportunities!
✤ TRB 98th Annual Meeting, January 13-17, 2019; Washington, D.C.
✤ 2019 NAPA Annual Meeting, January 20-23, 2019; Marco Island, Florida
✤ World of Asphalt, 2019 Show and Conference, February 12-14, 2019; Indianapolis, Indiana
✤ 2019 AEMA-ARRA-ISSA Annual Meeting, February 18-21, 2019; Cancun, Mexico
✤ AAPT Annual Business Meeting and Technical Sessions, March 3-6, 2019; Fort Worth, Texas
NAPA FREE Webinars - click here for additional information and to sign-up:
Asphalt Institute (all FREE):
✤ Asphalt Emulsion FREE Webinar Series Recordings
✤ Pavement Preservation Treatments FREE Webinar Series Recordings
✤ Advanced Pavement Preservation FREE Webinar Series Recordings
✤ Tack Coat Best Practices FREE Webinar
✤ Thin Lift Asphalt Overlays FREE Webinar
National Highways Institute: Full Depth Reclamation, or FDR, is a rehabilitation technique in which the full thickness of the asphalt pavement and a predetermined portion of the underlying materials (that is, the base, the subbase, and/or subgrade) is uniformly pulverized and blended to provide an upgraded, homogeneous material.
|(back to top)|
Click to view this email in a browser
If you no longer wish to receive these emails, please reply to this message with "Unsubscribe" in the subject line or simply click on the following link: Unsubscribe
Hawaii Asphalt Paving Industry
1287 Kalani Street, Suite 202
Honolulu, Hawaii 96817
Read the VerticalResponse marketing policy.