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By Tom Herrmann / ADOT Communications

The next time you’re riding in the passenger seat or back seat down the Loop 202 South Mountain Freeway, or perhaps another freeway closer to you, take a few minutes to gaze out of the window. But don’t look at the mountains or a beautiful sunset. Instead, look at the colorful designs on the bridges, ramps and sound walls. Look at the plants too.

An ADOT team creates designs for a freeway based on either the history or the current use of the land. If you drive over the Salt River on the South Mountain Freeway, you can see images that look like waves of water passing over desert rocks. In the West Valley, the South Mountain Freeway designs are inspired by the area’s agricultural past. In Ahwatukee, the freeway's designs are inspired by Frank Lloyd Wright, one of the greatest architects in American history. He once worked in that area.

ADOT also decides which plants and other landscaping accents will help make a highway beautiful. 

The video at right shows you designs and the landscaping along the 22-mile South Mountain Freeway.

But what if those walls, bridges and ramps were blank? What would you draw on them? Would they be animals or saguaros? What plants and colored rock would be in the landscaping? This ADOT Kids activity asks you to make those choices and create your own freeway designs.

It isn't just the South Mountain Freeway with neat designs. The new State Route 87 interchange with Interstate 10 between Phoenix and Tucson has designs inspired by cotton grown in that area. In Tucson, sound walls at the new Ajo Way interchange with Interstate 19 have images of mountains and saguaros that speak to that area's landscape. If you need more inspiration, the slideshow at right has images of highway designs around the state. 

Not everyone is fortunate to have beautiful designs on walls and bridges. The first time my dad came to Arizona, he was surprised by images of desert plants on the sound walls that separate the freeway from buildings. Near his home in Ohio, freeway walls are just that: a gray concrete wall with no decoration.

Fortunately, in Arizona we use freeway designs to help tell the story of an area.

For a different perspective on the South Mountain Freeway's design, check out the video at right shot using our drone.

Print out the coloring sheet and draw your own freeway design!

Make a freeway beautiful using the coloring sheet linked here and posted at bottom right. Or draw your own from scratch. Add your own designs and colors. Pick and locate plants. Will you use decorative rock? All of the choices are up to you.

Here some interesting freeway fun facts ...

• The freeway looks like it’s all concrete, but it includes enough steel rebar weighing 40 million pounds. That's about the same as 3,100 elephants!
• To build the freeway, we moved enough dirt to fill State Farm Stadium, where the Arizona Cardinals play, six times!
• We moved more than 1,000 desert plants – saguaros, palo verde trees and more – out of the freeway route and replanted them when the work was finished. Here's a video of how we did that for a project along Loop 101 in Scottsdale. 
• Ever heard of a chuckwalla? They’re small lizards that lived on South Mountain. We moved about 120 of them to keep them safe during construction. Here's a video of the relocation.
• How did the jackrabbit cross the road? There are five crossings under the freeway where people and animals can get safety from one side of the road to the other.

Work on the Hell Canyon Bridge replacement project is really moving along…

As you can see in the video above, crews are placing girders for the new, wider bridge set to replace the 1950s-era bridge that drivers use today.

The work is all part of a $14.4 million improvement project that includes the construction of the new bridge (it’ll be a four-span steel-plate girder bridge), the eventual removal of the old bridge and some additional road construction/realignment work to the north and south of the new bridge.

The new 665-foot-long two-lane bridge will feature wider travel lanes and will be approximately 47 feet wide, more than 17 feet wider than the current bridge. The bridge will also accommodate heavier loads, making it more convenient for commercial trucks to carry goods and produce to their final destinations.

This project animation gives a good look at what to expect as the work progresses. See some recent photos of the project on our Flickr page.

Ever wonder what it takes to move one million cubic yards of rock and dirt?

Turns out you need plenty of heavy-duty equipment, a fleet of enormous trucks and a lot of explosives (detonated by trained professionals, of course).

Oh yeah, you also need some time...

Those big trucks you see in the video above have been working since the summer on the landslide-damaged section of US 89, about 25 miles south of Page. By April 2015, ADOT contractors (and their trucks) will have moved the million cubic yards of material from above US 89 to build a stabilizing buttress below.

You can check out our previous blog post to learn more about that buttress, along with additional repair details. The landslide occurred back in February 2013. Since that time, ADOT conducted a major geotechnical investigation and worked diligently to restore mobility to the area by paving Navajo Route 20/US 89T, a 44-mile route that is serving as a detour for motorists heading to and from Page and the Lake Powell area.

Watch today’s video and you may never look at pavement markings in the same way ever again…

Who knew there was so much to understand about these stripes?

A little bit about what you’re seeing

Thermoplastic striping is a different than a painted stripe. It’s also unlike this striping tape we showed you back in 2011 when a portion of the Loop 303 opened.

Thermoplastic striping is a highly reflective, long-lasting pavement marking material that is resistant to cracking (from freeze and thaw cycles).

You can see in the video above, that the thermoplastic compound must be heated to 400-440 degrees so that it will bond to the road properly.

To make the stripes reflective (so they're visible at night), glass beads are dropped immediately into the thermoplastic material – you might remember reading about how ADOT tests glass beads for reflectivity in this blog post on the agency’s structural materials testing lab.

ADOT uses thermoplastic striping for its many benefits, including the fact that it doesn’t crack, chip or impact shatter, it’s environmentally safe and the process allows for quicker striping.

Here we are, blogging about pavement … again! When we told you there’s a lot to learn on the subject, we weren’t joking.

Today’s topic has to do with how concrete pavement is made – it all starts at the batch plant.

A batch plant is where concrete pavement is mixed before it’s trucked to where it is needed. On some ADOT projects, contractors will utilize a portable plant (which is what you see in the video above).

These portable batch plants are a huge time and money saver, allowing contractors to mix concrete on a project site instead of purchasing and hauling it from an outside source. According to one estimate, mixing on site saves about 20 percent over what it would cost to purchase from a commercial plant.

But, how does the concrete actually get made? We’ll borrow an explanation from this blog post to tell you:

If you can imagine mixing a giant cake, you can visualize how concrete is made.

First the contractor has the components – cement, fly ash, aggregate (rocks) and water – delivered and placed in stockpiles around the plant. The material is then loaded onto a conveyor belt and weighed by a computer before being placed in the mixer.

In just a minute and a half the concrete is ready to be loaded onto a transport vehicle and then placed on the roadway.

But, wait … there’s more.

Want to learn some additional facts about pavement? Check out our previous posts. We’ve blogged about quiet pavement, pavement at airports, materials testing, pavement markers, the impact climate can have on pavement and how crews make sure pavement is as smooth as possible.

We were perusing the ADOT Construction Manual just recently (because, really, who doesn’t enjoy reading a good manual every now and then?) and we came across a passage that terrifically sums up ADOT’s Project Development Process.

We’ve blogged before about many of the steps in the process – planning, prioritizing, funding, building and maintenance – but we think the text below gives an excellent overview that we’d like to share with you today…

The project development process or highway development process (as it is sometimes called) begins with a traffic, safety, or environmental problem that needs to be solved.

For example, a passing lane may be needed on a rural highway to relieve congestion and reduce accidents. The problem is usually identified locally by ADOT's Regional Traffic Engineer, a maintenance foreperson, the District Engineer, a city or county Engineer, or an elected official. Some projects are initiated by the Department’s Transportation Planning Division who look at traffic patterns and highway safety on a statewide basis. Most projects are initiated at the district level.

Since there are usually more projects identified than money to build them, a process of prioritizing each project, determining its overall scope, and estimating its costs is initiated during what we call the planning phase.

During the planning phase, a study is initiated where several engineering and environmental elements are reviewed in detail and results of the study are often shared at a public hearing. After public hearings and an environmental clearance is granted, the project advances to the design and pre-construction phases. Here the project is turned from an abstract idea into engineering drawings, additional right-of-way is purchased, as needed, and construction contract specifications are written.

But, before a project can move into the implementation phase, the project must be included in the Five-Year Highway Construction Program and have funding set aside. The Five-Year Highway Construction Program is reviewed and ultimately approved each year by the State Transportation Board. In addition to approving the Five-Year Highway Construction Program, the State Transportation Board officially awards a contract to the contractor who was successful in the bid process or in some cases is most qualified to complete the project.

The next step is to build the project. The contractor moves on to the project site and an ADOT Construction Field Office oversees the construction work. Their job is to inspect the work, pay the contractor, and ensure the project serves the public as intended.

The final steps are to open the project to the public and to maintain the project or facility so it performs as needed.

Stay tuned to the ADOT Blog – we have some posts planned for the coming weeks and months that will further explore each of the steps listed above!

Editor's note: The text above is quoted from the ADOT Construction manual, but we clarified a few sentences and added the links.

As you can see in the video above, girders are the concrete and steel beams that enable the bridge to support the roadway and the vehicles on top of it.

They’re vital to the design of a bridge, but not all girders are the same…

Just like each bridge in Arizona is individually designed to hold up in the conditions unique to its surroundings, girders differ in size, shape and type, depending on the situation in which they’re being used.

This is a topic that can get complex real fast, so we’re going to keep it simple today by just focusing on two types of concrete box girders: prestressed concrete box girders (these are featured in the above video) and post tension concrete box girders.

But first, we’re going to need to look inside the girder itself…

The girders we’re referring to are made up of very strong steel strands or rods that are surrounded by concrete. The difference between the two types of girders hinges on when the tensioning (or stretching) of the steel takes place – it’s either before or after the concrete is poured.

Tensioning, by the way, is done to give the concrete some additional strength. This explanation from the ADOT Construction Manual might help better explain the need for tensioning/stretching:

Concrete is strong in compression and weak in tension. Reinforcing steel is generally used to carry the tensile loads placed on a concrete structure … Reinforcing steel is used to help concrete carry compressive loads and shear stresses that develop when loads move through a structure.

If a girder is prestressed or pretensioned, the steel strands are stretched to a predetermined stress and then concrete is poured around the strands.

“Once the concrete has hardened and gained sufficient strength, the ends of the strands are cut. The strands inside the concrete try to relax and shorten. However, there is now concrete bonded to the strands. As the strand shorten, they push the concrete together and induces a compressive stress into the concrete,” according to the ADOT Construction Manual.

More from the manual regarding post-tensioning…

Post-tensioning involves running steel ducts through the concrete (girders). Special anchors are placed at each end of the (girder). Then concrete is poured around the ducts and the anchors. Steel strands are run through the ducts. Once the concrete is strong enough, the strands are pulled at one end while anchored at the other.

Pulling (or jacking) of the strands causes the ends of the concrete (girder) to push toward each other. This induces compressive stresses along the entire length of the concrete member. After jacking, grout is injected into the ducts then concrete is poured around the ends of the anchors. Once the grout gains strength, the strand is now bonded to the concrete member in a way similar to pretensioning.

When to use prestressed vs. post-tensioned girders

State Bridge Engineer Jean Nehme says that using prestressed box girders is sometimes more convenient because they’re constructed off the project site.

“Because you build them off-site, you cut down on the time of construction,” said Nehme, adding that using prestressed girders can cut down on the need for traffic closures.

But, whether the girder is prestressed or post-tensioned, Nehme says by tensioning the reinforcing in the concrete, engineers can design stronger bridges that span longer distances.

“It provides better durability in the long term,” he said.

You probably don’t think much about drainage when you’re driving, but a well-designed drainage system can increase the lifespan of a highway and help keep the public safe.

We’ll blog about how these systems are designed and maintained soon, but today we just want to give you a quick glimpse of the types of drainage solutions used on a project like the Loop 303/I-10 interchange.

You can see in the video above that a lot is required to collect and remove water from the roadway …

On this particular project the drainage system consists of storm drain pipes, concrete channels, box culverts and drainage basins. Because so much excavation work is required (more than 1 million cubic yards of dirt had to be moved on this project!), most of the storm drain work is completed early on in the project.

For more on how ADOT builds a freeway, check out some of our other videos and blog posts on the subject.

Placing Portland Cement Concrete Pavement (PCCP) is one of the final steps involved when building a road, but it’s far from an afterthought…

Type of pavement is a consideration very early in the planning phase when designers look into various factors, including pavement design life, traffic volume and type, soil conditions and maintainability. Based on these factors the designers determine everything from the pavement's thickness to how strong it needs to be.

Let’s take a look at how it’s made

Portland Cement Concrete Pavement (PCCP) consists of cement, sand, aggregate (rocks) and water. There are also admixtures – materials often added to the concrete mix to alter its properties. These admixtures can do a number of things to the concrete mix. Depending on the need, they may be added to reduce water, slow the setting rate, accelerate the setting time or add color to concrete, among other things.

A few facts about PCCP

• When it’s this hot outside (100 degrees and up), crews have to mix and place the PCCP at night when temperatures are cooler. There are a few reasons for this, one having to do with water evaporation. In higher temperatures, the water in the concrete evaporates faster (more water could be added to maintain the consistency, but that has the unwanted effect of reducing concrete's strength). Conversely, if the weather gets too cold in the winter months, crews can’t place PCCP because the water will freeze and inhibit the PCCP from curing properly.
• Portland Cement Concrete can be purchased or mixed on site.
• PCCP has a long life-span. In Arizona it’s used mostly on freeways within the Valley and Tucson metro area. Because of its durability, PCCP is great for these high-traffic areas.
• A curing compound is sprayed onto the PCCP after it is placed. It creates a kind of membrane that prevents moisture from evaporating from concrete (again, water is a key component to PCCP’s strength).
• Crews aren’t done once the PCCP is placed. The PCCP is not ready for traffic unless it meets certain criteria. ADOT tests for strength, thickness and smoothness before vehicles are allowed on the road.

When you’re building bridges, there’s more than one way to get the job done...

We told you a few months ago about a method that utilizes false work and sand jacks. Today, we’re going to fill you in on a different approach … the key terms to remember are soffit fills and waste slabs.

If you recall, false work is what secures the bridge structure as it is being built and until it can stand on its own.

A soffit fill (basically a big pile of dirt) acts much in the same way.

After the bridge piers and abutments are cast, the area in between is filled with dirt. That dirt is piled right up to the height of where the bridge deck eventually will sit … this soffit fill will act as the false work, providing a strong foundation to build the bridge on top of.

With the dirt in place, a thin concrete slab – the waste slab – is poured on top (see video above). The flat, smooth surface is what crews will build upon, but the waste slab won’t be a part of the finished bridge. No, the job of a waste slab is to simply give crews a form on which to pour more concrete.

Maybe a little analogy right about now might help you get the picture. Take a second and think about making a pie (trust us!).

Your counter top is acting as the soffit fill – giving you a surface to work on. Now imagine your pie pan as the waste slab – it’s giving you a form to shape your crust, but after the pie comes out of the oven, you’re not going to need the pan … your piece of pie will stand on its own!

OK, with us still? You’ve got your counter top (soffit fill) and your pie pan (waste slab), but before you place the pie crust you want to make sure it won’t stick to the pan … maybe you’ll use some non-stick cooking spray?

That’s kind of what crews use out in the field. They spray a thin wax coating over the waste slab so when they pour the concrete for the actual bridge structure on top, it won’t stick. Because remember the waste slab is just that – waste. It’s only there to temporarily provide a surface for the building of the bridge, but eventually it will be removed along with the soffit fill.

From there, crews complete a number of additional steps...

Keeping with our pie analogy – there’s “filling” involved with some bridges. In the case of the bridge being built at the Loop 303 and Waddell Road, the crews are actually building “lost decks,” so named because the materials ADOT uses in the framework will remain inside the bridge structure for the lifespan of the bridge.

These “lost decks” are inside the bridge and give it strength, but also allow for some open space, because a bridge of this size made entirely of concrete would be too heavy.

After the filling is inside, all that’s left to do is place the top crust, a.k.a. the top deck, which is what motorists will eventually drive on.

Crews will then bring in heavy-duty equipment to remove the soffit fill and the waste slab, but we’re going to save that for another blog post … so stay tuned!