 Did you ever have one of those days, you know a Murphy's Law type of day where everything that could go wrong does go wrong? Well, in this third part of asphalt paving inspection, it will sure seem like one of those days. We'll have all kinds of problems with mixed design, paving, and compaction. But don't blame it on the crew. You know, usually it seems like every time we take out a camera to videotape an operation. A good operation might be, something goes wrong. It's not planned, it's not even typical, it just seems like the camera is a curse. To make matters worse, this poor paving crew had two cameras on them. Well, actually this is one of the best crews we've seen. They were so good we had to ask them to be bad, to do things wrong on purpose so we could show you what to look for. In doing so, we may talk about the causes of problems and show them being repaired. However, that's not the real purpose here. Identification is. So be aware that there may be other causes of problems and possible solutions besides those listed here. With that in mind, let's get started with the mixed design. You'll remember from part two, you should always inspect the mix as it's delivered. There are several mixed defects that can occur at the plant, especially a plant as schizophrenic as we ask this one to be. Blue smoke indicates that the mix is too hot, way too hot. If a haul truck delivers mix to the job that's still smoking blue, just imagine how hot it was at the plant. Check the temperature immediately and reject it if it's out of spec. Asphalt this hot is probably burned, so its chemical properties are altered, meaning its binding ability is lost. On the other hand, if the mix is too cold, the air or surface temperatures are too low, where the haul is too long, the results aren't too pretty. Lumps in the mix are a good sign that the mix is too cold. Lumps can also be caused by improper mixing. In either case, the lumps themselves present a problem. They aren't shaped by the screed and they can't be rolled out, so they remain separate from the surrounding mix, causing weak spots in the mat. Try to catch them before they get to the mat, otherwise they must be dug out and replaced by hand. Another clue that the mix might be too cold is a stiff appearance. This can also be evidence, though, that there's not enough asphalt in the mix, especially if the mix looks dull. No, I don't mean boring, I mean lacking the normal shininess of fresh mix. A stiff, dull mix is a sure bet you'll have binding and compaction problems. Now quite the opposite. Too much asphalt. Now this may be as obvious as asphalt soup, a few aggregate floating in a pool of oil. Usually, though, you can tell by the flow of the mix. If it's more fluid than normal, chances are good the asphalt content is too high. This can cause compaction problems and bleeding on the surface. Segregation is also a common mix defect and can be caused by problems anywhere from building stockpiles at the plant to loading the hopper. Here it's caused during truck loading at the plant. The larger aggregate roll to the bottom of the cone-shaped pile. Pockets of fines and pockets of course aggregate are easy to spot, unfortunately it's not easy to do anything about them if they're already compacted in the mat. Reject a segregated load before it's placed. Otherwise, without the necessary interlocking of different sized aggregates, the surface will soon begin raveling. You might think that excessive steam is also an indication that the mix is too hot. Actually, the temperature is okay. It's just there's too much water in the mix, which is usually caused by too much water in the aggregate and or a dryer problem. This excess water can weaken the bond between aggregates and the asphalt. Another thing to look for in the mix is debris or perhaps an oversized piece of aggregate. Here a large rock got caught under the screed causing this long gouge in the surface. Improper screed extension mounts or an unheated screed at the beginning of the day can cause similar streaking and other mat problems. You never know what might get into the mix or what might get thrown in the hopper with it. You may be aware that some parts of the country use recycled asphalt material. As of yet though, no one recommends paving with recycled aluminum. And those are some common mixed effects. Again, the key is to spot them early. Ideally at the plant, but if not then, at least before they reach the screed. But even the best mix can't overcome faulty paving practices. Let's start with haul trucks. Can there ever be too many? Sure. And if they wait too long, the mix will get too cold. However, that's so rare, it's hardly worth mentioning. A more common problem, of course, is not enough trucks, especially when you have a long haul distance. True, long pauses provide great breaks for the paving crew. Unfortunately, the weight of the screed resting on the mix will create an indentation in the mat when paving resumes. This can put a lot of pressure on drivers to speed things up, which often leads to another consequence. The result, besides an upset whiplash victim, is that the truck knocks the screed back into the mat, creating a crease. A problem that's hard to fix, but simple to avoid, with a little effort on the driver's part. Something that might take a little more skill for the truck driver is working on hills. Remember, in most cases, the truck backs up within a meter or so of the paver and stops. The paver moves ahead and pushes the truck while the truck loads the hopper. That's simple enough on flat ground. But when going down a hill, the truck driver needs to apply the brakes, or the truck will pull ahead of the paver and spill the mix. So the driver may hold the brakes too hard, which will cause the paver to spin it first because of built-up momentum. Then, when the driver releases the brakes, the paver will frog or suddenly lurch forward, leaving a dip in the mat. If you're working on hilly terrain, consider using a hitch, or a device like this, which is inserted in the truck's wheel wells to hold the truck in place. Now, sometimes, mix may spill ahead of the paver when the truck is finished loading. Some crews shovel this mix to the middle, others remove it. What no one wants, though, is a pile of mix that the paver's wheels or tracks will run over. Even though most screeds respond to the sensing device, they are still attached to the paver. If the paver suddenly rises, it brings the screed with it, before the screed can adjust, leaving a corresponding bump in the pavement. Here, for our dramatization, our pile of spilled mix created a virtual speed bump. While we're behind the paver, let me introduce Win-Mill Johnny. It's easy to see how he got his name. He's constantly whirling and twirling the mat depth controls. Depending on the machine and the intervals between adjustments, he's either accomplishing nothing, or these abrupt changes will show up in the mat. Rumor has it that the roller operators on Johnny's job often get seasick. But those roller operators aren't without blame themselves. Let's leave the paving operation and look at some compaction problems. Some people call this hot mix. Some people call it hot asphalt. You can call it hot for short, because it sure is, especially in the middle of summer. A nice cool drink is not just a luxury, it's a requirement. But never park the roller on the fresh mat, especially right behind the paver. The weight of the roller depresses the mat, causing a birdbath. And fortunately for the crows, and unfortunately for you, it can't be rolled out. But the fact that you shouldn't park on the mat doesn't mean you can enter and exit the mat at will. You can see what happens going from the traveled surface to the fresh mat. There's no way to properly repair this. We asked this operator to do it for the video, and his supervisor still almost fired him. Rolling these edges can be tricky. Because of the lack of lateral confinement, the mix tends to shift or roll out under the roller. Sometimes a minimal amount is unavoidable. But if there's excessive roll out, the mat temperature may still be too high, or there may be some type of mixed effect. Rolling while the mat is still tender will cause pushing or shoving anywhere in the mat, not just the edges. The same problem can also be caused by sudden roller stops and reverses. For steel wheel rollers anywhere. For pneumatic tired rollers, sudden stops and quick gear changes will scuff the mat. And if the mix is cooled too much, almost any change in roller direction may leave marks on the mat. And for either type of roller, the scraper and water nozzles must be working properly. Otherwise, they'll pick up mix, a surface defect in itself, which ends up leaving impressions each time the clot of stuck mix impacts the surface. To add insult to injury, you'll end up trying to scrape hard and mix off the roller. A difficult task. And don't even think about using diesel fuel to make it easier. Remember, if it dissolves the mix on the roller, it will dissolve the mix in the mat. And that was the last problem that Compassion will cover, which certainly makes the paving crew a lot happier that they can return to normal. It also means we've come to the end of this program on asphalt paving problems. You'll notice we didn't spend much time discussing how to fix these problems. That's because the key to proper paving and inspection is learning how to recognize potential problems and prevent them. Hopefully, this program will help you do that on your projects, not just help you spot those major goof-ups by that crew from the next county over.