What happens on top of Arizona’s highways is for everyone to see and use. What happens within the pavement is Kelly Baum’s business.

Baum is among the ADOT employees charged with the crucial job of testing, component by component, what makes up every mile of Arizona highways.

Before a car can drive on a highway surface, the highway has to pass a battery of tests performed at ADOT’s materials laboratories.

“What we do here is very important,” said Baum, supervisor of ADOT's Phoenix Materials Lab. “Engineers focus on the building and the plans. We are the ones who run the tests that show if they are on the right track.”

For Baum, an ADOT employee of 21 years, ensuring safe roads motivates her.

“It’s taxpayer dollars we are dealing with,” Baum said. “Taxpayers are trusting us to say it’s safe to drive on, that it’s safe for our families to drive on.”

Using sophisticated equipment and an array of tests, ADOT’s labs evaluate a range of materials, from rocks in cement to bolts on bridges.

“We have specifications that each project has to follow, whether for concrete, asphalt, soil or aggregate,” Baum said. “It’s like a recipe they have to follow.”

One test is like panning for gold. It uses sieves to determine if there’s a consistent percentage of sand or rock. The correct ratio results in a road surface that is smooth but still has traction when it rains.

Another test measures voids, or air pockets, in asphalt. You want some voids so water can drain into it during storms, but you don’t want too many or the road may not hold up as needed.

Lab employees are always under deadline, Baum said. They have four days upon delivery of samples to administer evaluations.

“Projects depend on and wait for this,” Baum said.

When Baum first entered the workforce, she never imagined she’d spend her days with rocks and dirt. She handled puppies and kittens for her first job as a veterinarian’s assistant in Kingman.

Prompted by circumstances to seek another job, she spotted an advertisement for an ADOT field inspector and landed it. Next, she was working in the soils department. One promotion led to another, and now she supervisors the Phoenix Materials Lab.

As supervisor, Baum knows every test and performs them often, as she did one recent day when a technician called in sick.

Trays of rocks, boxes of concrete cores, tubes of sand and a variety of other materials were heaped on tables at the Phoenix lab.

Anthony Avalos, the lead technician, was testing the breaking point of core samples to determine their strength.

Matthew Turner was running a plasticity test to evaluate plastic and liquid limits in a soil sample, Joe Allison was evaluating the ratio of sand to liquid in another sample and Corrie Romo was evaluating gradation samples.

Talking about her career, Baum said, “When I started working the lab, it just clicked. I really enjoyed the variety of things you can encounter with materials. I’m fascinated by that still.

“It’s the best job in the world. It’s playing in dirt.”

By Lori Baker / ADOT Communications

Touring an ADOT Materials Lab, students from Copper King Elementary School in Phoenix learned how math and science skills taught in the classroom are used to build roads and other infrastructure.

More than 50 seventh- and eighth-graders from Copper King’s Science, Technology, Engineering, Arts and Mathematics (STEAM) Academy took turns touring different sections of the Phoenix lab and participating in hands-on activities. They viewed pavement management, mix design, binder and asphalt, structures and the annex where testing equipment is calibrated. They touched materials and learned about engineering overall. They also got a close-up look of the equipment trucks that pavement management uses.

“This was a unique experience to show students how important the skills and knowledge they learn in school through their math, science and technology work are in many professions,” said Allan DeOrnellas, Copper King Elementary STEAM Academy teacher.

“The tour helped demonstrate the importance of being precise with their work and that improvements are being made every day in many aspects of our lives that we do not see,” he added.

Copper King eighth-grader Sebastien Peterson, son of an ADOT employee, helped organize the tour as part of his Chief Science Officer program.

One of his favorite activities was feeling the vibrations from “Thumper,” a falling weight deflectometer that engineers use to test the strength of the soil where roads are constructed.

Also popular was performing science experiments like creating gooey asphalt, and breaking concrete cylinders and steel rebar.

“The kids were really engaged and inquisitive,’’ said ADOT Assistant State Materials Engineer Paul Burch.

The material labs tour was a follow-up activity after Deputy Director for Transportation/State Engineer Dallas Hammit met last fall with STEAM Academy students to explain how ADOT builds and maintains Arizona’s transportation system.

Burch and ADOT Assistant State Construction Engineer Jesús A. Sandoval-Gil said the materials lab welcomes other school tours.

EDITOR'S NOTE: During National Engineers Week, which calls attention to the importance of engineering and career opportunities in engineering, blog posts are featuring different aspects of engineering at ADOT.

By Steve Elliott / ADOT Communications

To explain her role as an ADOT materials engineer, Julie Kliewer suggests thinking about the parts and pieces that go into anything.

“Your house, the sidewalk, the road you drive on every day – it’s all engineered, and it’s all made up of materials,” she says.

As ADOT’s State Construction and Materials Engineer, Kliewer leads a group whose duties include ensuring that quality materials go into roadways, bridges and other parts of Arizona’s highway system. The materials laboratories she directs evaluate everything from the rocks (also known as aggregate) used in asphaltic concrete to the reflective beads used in paints that stripe roadways to the bolts that help hold bridges together to the metal in sign posts.

The photo at right shows a Universal Hydraulic Testing Machine, which the Structural Materials Team uses to evaluate rebar.

While some ADOT engineers focus on design, others on construction and others on maintenance, materials engineers are involved in each of those phases, Kliewer notes.

In the design phase for a new highway, for example, that includes understanding the makeup of the earth beneath the roadway and the pavement that should be put on top of it. During construction, materials engineers make sure the mix of raw materials used in pavement is designed and delivered properly for that area’s conditions, including the temperatures. Later, materials engineers test how the pavement is performing and make sure materials used to maintain it meet specifications.

Kliewer, shown in the photo at top leading aspiring engineers on a project tour, has a Ph.D. from Oregon State University in civil engineering with a specialty in materials, along with minors in geotechnical engineering and numerical methods. The title of her dissertation explains why she’s often referred to around ADOT as having a “Ph.D. in pavement”: Development of Performance-based Test Procedures for Asphalt Mixtures.

While working with pavement is just one of the duties handled by ADOT materials engineers, it's among the most visible to the public, as ADOT's main asset is the thousands of miles of road surface in the state highway system.

If you want a challenge as an engineer with an interest in materials and pavement, try working in a state with many highways exposed to relentless heat and sun and others at high altitudes seeing dozens of freezes and thaws throughout the winter, along with snow and snowplowing.

For materials engineers dealing with pavement, one challenge is writing specifications that get the right pavement mix and good quality for a given area.

“It’s not a matter of just throwing some aggregate and asphalt together,” she says. “It’s a balancing act.”

In asphaltic concrete, asphalt holds together the aggregate that supports the load. One of the things materials engineers look for in a mix is voids, or airspace. If there are too many voids, the pavement won’t last as long as it should. If there aren’t enough voids, it won’t be as stable as it could be. The photo at right shows a Hamburg Wheel Tracker, which ADOT's Pavement Materials Testing group uses it to evaluate asphalt mixes.

In addition to designing the best pavement mix for a given location, ADOT materials engineers test how the road surface will oxidize and growing stiffer over time. That stiffening, accentuated by Arizona’s dry climate and abundant sunshine, contributes to cracks that are addressed with substances evaluated by ADOT’s materials engineers.

Kliewer’s path to materials engineering began in high school, when she couldn’t decide whether to be an engineer or a forester. She was able to do both at Oregon State University, earning bachelor’s degrees in forest engineering and civil engineering but finding that materials classes struck her fancy.

“It just fit me,” she says.

After two years with the Oregon Department of Transportation, working mostly in materials research, she returned to Oregon State University to teach surveying and geotechnical engineering in the College of Forestry. While teaching, she earned a master’s in forest engineering and her doctorate in civil engineering.

The reward of materials engineering, Kliewer says, is figuring out how things fit together, whether it’s in pavement, bridge girders, concrete culverts or anything else making up the highway system.

“If you like solving those kinds of puzzles, it’s a really rewarding career,” she says.

You might think that highway construction is all about big machinery, heavy-duty vehicles, massive structures and materials by the ton – but it’s not.

Sure, those are important, but when it comes to building a road, science plays a strong role too. In fact, the work ADOT does off the project site and inside a lab is so significant that we are highlighting it here on the blog with a new series we’re calling, The Science of Transportation.

We’ll start today with a look into one of the methods used by ADOT to analyze soil samples.

The sieve analysis test, as you can see in the video above, is a way for technicians to create a profile of the sample’s size properties. That profile, in conjunction with other test results, is used to classify the soil – something that is useful for geotechnical engineers, road designers and construction crews.

This test is fairly straightforward.

First, the technician must prepare the sample by drying it and making sure there aren’t any clumps in the material. They weigh it at this point, too.

Next, the sample is screened through a series of sieves. The test starts with a very coarse sieve, and continues with sieves that get finer and finer. The ADOT technician records the weight of the material retained by each sieve.

You can see in the video that a (loud) mechanical shaker is used to move the material through the sieves.

When it gets down to the very, very fine material, technicians will need to split the sample, dry it, weigh it, wash and dry it again before continuing on to the next set of sieves. The screens on these sieves have very small openings that let only the smallest particles through.

Once all the material from the sample has been sieved, the sum of the individual weight of the material from each sieve is compared to the weight of the entire sample that was taken prior to sieving. If the difference between the two weights is more than 1 percent, the sample must be recombined and the sieving process would start all over again.

All of the information is recorded to provide a profile of the material’s size properties.

So, why does ADOT (and other transportation agencies) go to such lengths just to determine the size of the soil particles?

Transportation Tech John Miller sums it up best in the video above…

“You need to know what type of material you’re building on,” says Miller adding that it could be a heavy clay or sand – two soils that behave differently from each other. “It’s very important to run this test.”

For more on the Soils and Aggregate group, visit the ADOT website. Be sure to stay tuned to the blog ... in the coming months, we'll be featuring more of the tests this group performs.

Hard to believe, but after more than 200 blog posts we’re still surprised by some of the things we find out here at ADOT.

For example, did you know there’s a small yard adjacent to an ADOT field office parking lot filled with dozens of sign samples?

We didn’t either … at least not until just recently.

Turns out they are there to soak in some sun. No joke – ADOT field tests sign sheeting material to see how well it holds up against the heat. Arizona’s the perfect place for a test like that, don’t you think?

The sign sheeting material (which you can think of as a big sticker – it’s the reflective, colorful material adhered to metal signs) is tested by ADOT as part of the National Transportation Product Evaluation Program (NTPEP). Arizona, along with a few other states, evaluates the sign test panels for three-year periods. The other states test for different weather- and location-related concerns … in Minnesota they check the signs reaction to freezing/thawing and in Florida it’s the ocean’s salt spray.

Before we go any further, let us tell you a little bit about NTPEP.

It’s a program that operates under AASHTO (a nonprofit association that represents this country’s highway and transportation departments) and besides sign sheeting, tests a number of items related to transportation, including concrete admixtures, PVC pipe and even temporary traffic control devices.

The results gathered by the DOTs doing the field testing is entered into a database. That information is then reported by NTPEP and, according to its website, is widely used by AASHTO member departments for decisions on which products to approve for their QPL (Qualified Product Listing).

OK, back to the signs…

ADOT Chemist Jeff Faulkner explains that the sign sheeting samples sit in the sun for three years. He and his crew take readings once a year ... they’re looking to see how the signs keep their color and reflectivity (important for night driving).

A hand-held instrument called a retroreflectometer reads for reflectivity and measures the way light bounces off the material.

An easy digital readout tells Faulkner and his team what they need to know.

Another instrument – a color measurement spectrophotometer – is used to measure color year to year in order to detect fading.

Of course, Faulkner and his colleagues use their own senses to report on how the sheeting is holding up. They look at the signs each year and note whether there are changes to the material – blistering, cracking and fading.

All the data they gather is entered into the NTPEP site and a report is prepared every three years. Because there are always new products coming onto the market and because manufacturers often update their older products, testing continues year after year.

For more on NTPEP, visit the program website.

Yesterday we told you about ADOT’s Pavement Materials Testing group and how it is responsible for testing aggregate and creating asphalt friction course mix designs.

Today, we’ll fill you in on everything else they do … starting with preliminary engineering evaluations.

These evaluations start long before construction begins on a project. A good, solid foundation is important when you’re building a road so soil samples get tested by ADOT for a number of things…

In the PI lab material is tested for clay (not a great foundation to build upon).

Then there’s the soil mechanics lab. Here they measure the strength of the soil by putting a vertical load on a sample and measuring the displacement.

There’s also the proctor test, which basically beats the soil with a kind of hammer to test how much construction crews will need to compact the soil for maximum strength.

Binder lab

Finally, there’s the binder lab. This is where asphalt is tested.

Samples come in from projects and the lab makes sure the asphalt will work the way it’s supposed to.

Temperature is very important when it comes to asphalt – this lab tests the asphalt properties at a range of different temperatures. They’ll also test for stress and strain and try to determine how the asphalt will stand up over the years.

More testing

This isn’t all the testing that ADOT does …

Under the umbrella of ADOT’s Materials Group there are several teams responsible for structural materials testing, quality assurance, pavement design and management, and geotechnical design and operations. There are also several regional and area labs that do different types of tests.

We’ll be blogging about these groups soon … so stay tuned!

Placing asphalt friction course on a newly constructed road is sort of like icing a cake (stay with us here).

Not only does it represent the final step of a process, but icing and asphalt concrete can both help make the completed product look just a little more finished.

However it’s all for nothing if you don’t have a good recipe … and unlike icing, the directions for mixing up asphalt friction course can’t be found in a cookbook.

Still with us? Good, because this is where ADOT’s Pavement Materials Testing group comes in. They work to develop and continuously improve the asphalt “recipe” for various projects around the state.

When creating an asphalt friction course mix design for a particular job, the goal is to design it so the finished product is strong and holds up to weather extremes. You also want a road that doesn’t crumble and isn’t too slick.

To get a good recipe some testing has to take place in the kitchen … um, we mean lab.

The Mix Design lab is where ADOT technicians test out the asphalt mixes and develop a friction course design (the recipe) based on materials and the location and conditions of the planned road.

This lab also does some research into innovative methods…

“We’re always trying to take advantage of new technology,” said Manager Janet Doerstling.

Aggregate Testing
The Pavement Materials Testing group is also responsible for evaluating samples from different projects just to make sure everything is meeting specifications.

Here’s how it works … a contractor will provide samples of the aggregate (rock) they plan to use. (By the way, aggregate is what gets mixed with asphalt -- a sticky, black substance that acts as a binder -- to create asphalt concrete.)

Next, the rock sample undergoes a series of tests, including…

The sieve shaker -- a coarse screen that takes the rocks and breaks them down by size because it’s important to make sure you’ve the right percentage of rock to sand.

Several tests are done in the Sand Equivalent lab. Here technicians examine different aggregate properties. One of the tests looks at how many straight, flat edges (aka faces) the rocks have. This is important because fresh faces soak up oil better in the asphalt mix.

This lab also tests the aggregate for resistivity to electric current because some rocks can actually corrode corrugated drain pipes!

Wait … there’s more
This is far from all the group does … but we’ll save the rest for tomorrow. Until then, check out their webpage and go have a piece of cake!