Saturday, April 30, 2011

Sand Equivalents

According to Caltrans' test method 217-Sand Equivalent, "The sand equivalent test provides a measure of the relative proportions of detrimental fine dust or clay-like material in soil or fine aggregates."  Fine dust (#200s and smaller) and clay material in aggregates can be detrimental to the performance of hot mix asphalt for a variety of reasons.  The clay-like material can absorb water, making it expand and giving the pavement mixture the potential for cracking and moisture damage.  Fine materials can lead to stripping and stability issues such as rutting and shoving because it may make the mix too fluid.  Think about when you're at the beach walking through the sand.  Sand is all small particles, usually #50-#200 size and the particles move to the side as you walk through it.  This is the same as shoving and rutting, although an extreme example.  The more smaller particles there are in the mix, the less stable the mix will be. 

Basically the test separates these detrimental fines from the non-detrimental (sand) particles.  The test results are a number but it is a percentage of good material in your sample.  So if your sample has a 90 sand equivalent that means that 90% of the sample was good material and 10% was detrimental.  If you have a 40 sand equivalent that means that 40% of the sample was good material and 60% was detrimental.  Many materials such as concrete sands will have high SEs, in the 80s or 90s but it is very rare to see a 100 SE.  On the flip side it is not uncommon to see a 1/4" x Dust product have an SE in the 40s or 50s because they usually have a considerable percentage of the sample passing the #200 sieve.  But overall it really depends on your aggregate source and what minerals of rock you are processing into your finished product.  Commonly you will see sand and gravel deposits with lower SEs because sedentary rocks can be cemented and formed with clay as bonds.  Hard rock deposits on the other hand are often formed metomorphically from volcanic activity and rarely have clay seams.  As such, their SEs are usually higher than sand and gravel deposits but don't take that as a fact that covers all deposit.  Every rock deposit is different from another and that rule of thumb may not hold true for all locations.  The best way for you to really know what is normal for your deposit is to test, and test often so that you have hundreds of tests to show what is normal across various areas of your deposit.

Like all test methods, the Sand Equivalent method has it's flaws.  Clay particles float so it is easy to know that this portion of the results is correct but the test also measures the content of "fine dust" in combination with the clays and this is the part of the test that I sometimes question.  The test flushes the clay and fine particles out of the rest of the sample by pushing a tube to the bottom of the sample and having liquid float these particles to the top.  It is true that these small particles will float up to the top and separate from the rest of the sample but what if you have particles that are flat and elongated?  If you have a parachute all wadded up, the chances are that it won't be lifted into the air.  That is like a standard round or cube shaped particle.  If you spread that parachute out, it still weighs the same but now the wind can lift it into the air.  This is like the flat and elongate particles.  So if you have lightweight, flat and elongated particles, say maybe your #100s or even #50s, these particles will rise to the top with the -#200 and clay particles giving you an abnormally low SE, even though those #50 and #100 particles won't act detrimentally to your product.  So be aware of your deposit and how your rock breaks down in the crushing process.  The specifications won't change for you if you have these special types of deposits but if you are aware of the problem you can combat it with either making your products with less #200s than other companies or by changing your crushing process to break the products in a different way. 

For instance, I've read multiple studies that say that if you use an impactor crusher instead of a cone crusher you will be able to force your products into a more cubical shape instead of a flat and elongated shape.  There are other possible negative impacts from this process though such as higher #200s and lower stabilities but like I said, every deposit is different and you won't really know what will work for your plant until you try it.    

Friday, April 29, 2011


Up until now I've resisted the twitter trend, thinking that it was stalkerish, boring, or just plain dumb.  Today I finally started an account and I have to say that I think there is some major potential for it being a useful tool for me as well as all of you.  As I was adding accounts to follow I realized that this isn't just a way for celebrities to tell us what type of hamburger they are eating for lunch today but also a way for people to broadcast breaking news and new products as well as being an immediate source for help if you had a question.  Imagine you're having a problem with the oil contents at your hot plant always being high... why not tweet about it?  If you have the type of followers that I'm hoping to collect from this website you might get a response from someone asking if you've tried running a moisture test.  Plus all of the Caltrans districts have twitter accounts and you can elect to follow them as well as a variety of other construction and paving groups. 

Really the opportunities are endless and I would completely recommend that you sign up and follow me at QualityinCali so we can build a community of resources for each other.

Asphalt Re-Lay

I found this company and I knew right away that I had to share it.  Asphalt Re-Lay is a company in Ireland that has found a new way to recycle asphalt pavement and repair potholes in less than 15 minutes.  They use an infrared heater to, for all means, re-melt the aged asphalt binder in the pavement, making the asphalt workable just like it was when it was first made. 

This is something that I could really see taking off, and not just for pothole repair.  If they can figure out a way to re-engineer this technology to turn entire highways into workable material in hours... our tax payers will be saving a ton of money and to be honest... some of us might be out of a job.  Yes, we already recycle a large amount of our highways in California by grinding them up and making them into base rock and putting some of it into new asphalt products but this type of technology will eliminate the cost of grinding the pavement up, loading it into trucks, shipping it to a plant where it is reprocessed and shipped back out onto a job. 

Think about the savings!  Their website is

I wonder how the compaction is on the reworked pavement when they are through with it.  They are using a relatively small roller which can lead to poor compaction.  Normally, roads should be compacted to around 95% and the bigger the roller the easier it is before the asphalt gets hard again.  Sometimes it's difficult to get compaction even if you have ample time just because you don't have enough weight on the roller.  However, since they are heating the asphalt there on site I bet that they have a lot longer to work on it than a highway crew who gets the asphalt delivered to them considerably cooler than when it was made. 

If you know anything about this product I'm extremely interested in learning more about it and whether they are planning to expand to the United States any time soon.

Thursday, April 28, 2011

Rubberized Asphalt

Currently in California the main type of Rubber Asphalt paving material is RHMA-G which means Rubber Hot Mix Asphalt-Gap Graded.  It is gap graded so that the small chunks of rubber can fit into the mix.  Yes you read correctly, small chunks of rubber. 

It is a common misconception that rubber paving mixes have a smooth liquid asphalt just like a traditional hot mix asphalt (HMA) however if you take a look at the asphalt binder for a rubber paving mix you will find a very different type of mixture.  Imagine that normal asphalt has the consistency of pancake batter.  A traditional rubber asphalt has the consistency of pancake batter with mini chocolate chips.  I think that all of you could figure out that rubber goes into rubber asphalt but most people, myself included, figure that they melt down the rubber before it is shipped to us or that the rubber bits melt down in the batching process at the hot mix asphalt plant.  For traditional asphalt rubber binder, both of these scenarios are false. 

The reason that RHMA is gap graded is so that these small pieces of rubber, called crumb rubber, can fit into the mix without leaving undesired gaps in the pavement which can lead to raveling or a variety of other pavement failures.  To be honest I'm not sure what the initial reasoning behind leaving the chunks of rubber in the mix was, but for me it seems like a chicken and the egg scenario.  You see, one of the biggest benefits to rubber asphalt pavements is that it reduces road noise.  You know when you are driving on the highway and you can barely hear yourself think and then all of a sudden its 10x quieter?  Chances are you just transitioned from traditional asphalt pavement or concrete to rubber asphalt pavement.  So I feel that it is definitely possible that some smart engineer out there figured out that we could reduce road noise from leaving in the chunks and designed what we now call RHMA for just that purpose.  Of course, it could also be that the rubber requires a special, expensive process to reduce it down to a liquid form...and no one wanted to pay for it at the time.  If any of you know the truth I would be extremely interested in what the real reason is. 

The crumb rubber in the asphalt is able to reduce noise because it is flexible.  If you're having trouble imagining this just remember that most of the rubber chunks in rubberized asphalt actually come from old car tires.  It is one of the biggest sources of recycling in the United States and an amazing way to recycle tires since, lets face it, aside from being good weights for tent poles, they are relatively useless after they wear out and just take up space in our landfills.  The flexibility of the crumb also helps the pavement's resistance to cracking.  It's like if you compared an uncooked piece of spaghetti to a cooked one.   Traditional asphalt pavements are generally made of two ingredients, traditional asphalt and rock.  Since rock is not flexible it cracks when too much pressure is applied to it.  Rubber asphalt pavements generally consist of traditional asphalt, rock, and crumb rubber which gives it flexibility, making it slightly malleable and resistant to more pressure than a traditional asphalt. 

Another theory for why asphalt rubber pavements are more flexible and quiet is because of their higher asphalt binder content.  The crumb rubber has the ability to absorb more asphalt binder than rock and as such called for a higher content of asphalt.  Unfortunately, that brings me to what a lot of people would consider the biggest downfall to rubberized asphalt pavement, it's much more expensive than traditional asphalt pavement, almost double the price.  This additional cost is partially due to the crumb rubber pieces and higher asphalt binder content but a large portion of the additional cost is due to the process in which the crumb has to be mixed with the traditional asphalt binder.  Because you want to keep the crumb rubber evenly distributed in the traditional asphalt binder it is not a good idea to ship the asphalt rubber binder in a traditional oil tanker where the crumb rubber will sink to the bottom of the tank.  Instead, all of the components in the asphalt rubber binder are shipped to the asphalt plant separately and mixed on site before being fed into the asphalt plant and mixed with the rock.  The process includes an additional piece of equipment (called a rubber plant) to heat and mix the rubber asphalt binder components together as well as at least 1-2 additional employees.  Many companies do not own their own asphalt rubber plant and rent the services as they need to produce asphalt rubber mixes, usually only a few weeks per year.  However, with asphalt rubber pavement becoming more and more prevalent in California due to its longer life span, I would not be surprised if it finally becomes financially feasible for companies to purchase their own rubber plant.

If you'd like to learn more about asphalt rubber pavements you might want to visit  I'll also try to break down the topic a little more over the next couple of weeks to give you a more detailed look into what I think is one of the best investments California is making right now.

Wednesday, April 27, 2011


Today I'd like to talk about Caltrans certifications.

If you are unaware, Caltrans is the Department of Transportation entity in California and is our indirect customer in the aggregate and asphalt industry. We sell our materials to construction contractors and they use those materials to build the state's roads, bridges, parking lots, etc. It's a multi billion dollar industry.

One of the ways that Caltrans ensures that it is getting the best products for their tax payers' money is by writing specifications and requiring the products used in their projects to abide by these specifications. Now I could spend weeks talking about specifications, and most likely I will in the future, but today I'm going to focus on one part of their specifications which is the testing and certification requirements. Caltrans' standard specifications is a pretty thick book that has the rules on anything from how the contractor will be paid, to the gradation of rock used, to how the materials will be installed. A pdf version of these specifications can be downloaded for free or the bound book can be ordered at Section 6-3 talks about the general testing requirements for the materials used in their projects, and it is here that you will find the requirement that all tests must "be performed in accordance with the methods used by the Department of Transportation."

Although, as I mentioned yesterday, ASTM is a greatly respected source of test methods, Caltrans has devised and/or revised new test methods that they feel suit their state's needs better. These test methods are often extremely similar to the ASTM methods with slight changes. However, the biggest difference to me as a person who spends most of the day trying to reduce costs is that the Caltrans test methods are FREE. Stocking a laboratory with a full set of relevant ASTM test methods can cost hundreds of dollars and every time there is a change to a test method you have to pay more money to get the new version. Caltrans, on the other hand offers all of their test methods and revisions at for no charge. In addition, the state will certify your laboratory at close to no charge as well, which is also different from ASTM.

Which finally brings me to certifications, specifically Caltrans certifications. You may wonder why a laboratory needs certifications at all. I mean, we've trained our people, they run the tests every day, and frankly the majority of the test results are only used in house anyways. The answer is simple. Credibility. Sure you could forgo getting your lab certified, I've worked at several locations whose lab was not certified, but it's basically free, so for the small cost of training and a couple of days with a state employee you could have a laboratory whose test results will be taken serious if you ever have a dispute with a contractor over the quality of your product or god forbid you had to go to court over it.

So you might be convinced that we should certify the lab but why should you have to re-certify every year? Think of it this way, every year your hot plant's scales get re-calibrated. They do this because over time things happen that can change the accuracy of the scale and make it less reliable. You calibrate every year whether you have seen warning signs or not just to be sure that you can be confident in your plant's weights. The same thing goes for technicians. For one, there are several test methods that the technician may only run once every couple of months. How long has it been since that technician read the test method? Does the technician review the revisions for each test method as it comes out and does he adjust his testing to meet the new rules? On the other hand, yes, the technician may run the same test ten times a day every day but is he doing it by the book every time? I strongly believe that it is natural human nature to find ways to make things easier and more efficient. Unfortunately that usually means cutting corners and skipping steps. The technician may skip a step here or there to save himself some time. Over the next few months he might end up skipping that step every time he does the test and after awhile might forget the correct way to do it, or worse yet, teach another technician the wrong way to do it. Re-certifying your technicians is a great double check for your laboratory. It reminds your technician to reread the test method, to run through it with their lab supervisor before being tested by the state, and overall to do it right. It's insurance for you so that you know that your technicians know how to do the test method correctly and that is extremely important in having credibility with your contractors and the state.
There are two major types of certifications with Caltrans, a laboratory certification and individual technician certifications on the test methods. Both of these certifications are controlled by the Caltrans Independent Assurance (IA) Program. Information for the Caltrans IA program can be found at the Caltrans IA Program Website although as I am posting this I acknowledge that a lot of the links do not work, sorry about that, but as you'll find, that seems to be a common theme with Caltrans. Sometimes finding the information you need is unnecessarily difficult but hopefully this blog can help lead you to the right places. The link on that website leading to the IA manual doesn't work but here is a link to the pdf file. Caltrans IA Manual. This manual is basically the bible for getting your laboratory and technicians certified by Caltrans. If you have a laboratory, whether you are already certified or not, I would recommend that you read through this as it gives you a lot of insight into what to expect from the state and how to prepare for their visit. Also, I should note that the manual I have linked to is the 2005 version which replaced the 2001 version. Take a look at the version you've been using and make sure that you have the most up to date version.

Some basic things to note with the IA program:
1. Testers have to take both a written and practical exam for test method certifications
2. Testers must take the practical exam within 3 months of the written exam
3. Lab certifications are based on the equipment required for each test method performed in the lab. You can certify a lab in only one certification or as many others as you want
4. You must put together and submit a laboratory accreditation manual
5. Having a safe work environment is part of your lab accreditation
6. You must calibrate and submit records for your laboratory equipment on an annual basis. A sticker must be affixed to the equipment stating the last date calibrated and additional other information
7. Your lab must participate in the Caltrans Reference Sample Program (RSP) which is where Caltrans sends your lab a duplicated sample for one of the tests your lab performs and your lab is to test the sample and send the results to Caltrans to confirm that your lab is capable of obtaining accurate test results.
8. Both technician certifications and laboratory certifications expire after 1 year. You must re-certify annually if you want to maintain your certification

These points do not even begin to summarize what can be found in the ninety page IA Manual so once again I would recommend reading the manual in its entirety but you get the point for now. What I would like to add to all of this is that you will most likely struggle with keeping your certifications up to date if you do not track them and stay on top of them. Generally you will need to give your IA inspector 30 days notice of when your certifications will expire and you need to be re-certified. Yes, you read that correctly. It is YOUR responsibility to let the state know when you need an inspector and to schedule the visit. It is not their responsibility and you will find your self in a very sticky situation if you wait for them to call you. So be sure to look to the future and schedule your inspections early so that you can be sure to keep your certifications up to date. Some inspectors seem to get overbooked and busy and they may let you know that they will not penalize you for being overdue on the certification and will re-certify you weeks after your certifications expire. If you can help it at all you should stand strong against this and insist (in a polite and positive way) that your certifications be renewed before your expiration date. Although the IA inspector may not penalize you, if your certifications are not current for the week that you pull and test samples of a material, that data could be thrown out in court because your credibility (your certifications) was non-existent at the time. If you give your inspector enough notice there should be no reason that they cannot keep your certifications up to date without a gap. This is just another example of how your communication skills in the quality sector need to be top notch. Not only do you need to make sure you let the inspector know enough in advance but you also need to maintain a good relationship with this person because, lets face it, they control whether your lab gets certified or not. So play nice but stand your ground on the important issues like maintaining the credibility of your laboratory.

Credibility is one of the most important factors in Quality Control and should be monitored with care.

Tuesday, April 26, 2011

Testing Discrepencies

As any quality technician will tell you, there are discrepancies between test results on a daily basis.  It is nearly impossible for two test results to have identical results, even if it is a split of the exact same sample.  Just like anything else in life, there are hundreds of variables that play into testing a sample.  Going back to my high school science classes I know that the three main types of error are human, mechanical, and environmental, all of which can significantly change test results in an aggregate and asphalt testing laboratory. 

On the human side of things your technician could read the results wrong, calculate an equation wrong, miss a step in the test method... any number of problems can results from human error and it is usually the largest source of error in the laboratory.  These types of errors are often very difficult to find after the test has been completed and as such, it is extremely important to keep a safe environment for your technicians in which they can admit when they have made a mistake and not be punished for it.  Without this type of open communication your technicians will not tell you of errors they made and may pass a bad test result off to you under the guise of a correct test result. 

Mechanical errors are usually much more obvious.  This could be anything wrong with the equipment used in the test method such as a worn screen, a broken fan, a dead heating element, etc.  Although you will not be able to eliminate these errors completely, the most important thing to do is to keep up with your preventative maintenance and be sure to calibrate your equipment on the required intervals.  Up to date calibrations are there to let you know that your equipment is operating correctly and can be the difference between doing a test correctly the first time and having to repeat it, costing the laboratory both time and money.

Environmental errors are the rarest of the three sources but should not be ignored by any means.  Small changes in temperature, airflow, air quality, etc. can all make significant swings in test results.  These sources of error are easy to forget about and are hard to quantify but the most effective solution is to be aware of them.  Know what environmental factors can affect your test and be aware of their status before and during your test. 

Even with all of the information available to us from test methods and training, we still have differences in test results.  Yesterday we had a technician that alerted us that we were getting very different test results for a Sand Equivalent test at two different labs.  Neither of the labs' results were very close to each other, showing that there was at least one sort of error occurring at possibly both of the laboratories.  Before diving in and starting a war between labs, the first thing to determine was whether or not the difference between results was enough to raise concern over.  Test Methods are commonly tested for and adjusted to control a variety of variables before they are completed and distributed to the public.  The most respected organization for standards in the United States is the American Society of Testing and Materials (ASTM).  ASTM takes extreme care in writing test methods and will go through many revisions until they determine that the test is repeatable within a specific deviation.  They test this by collecting samples from various locations across the United States and testing them at multiple laboratories with multiple technicians.  They determine a standard range within which your test results should remain for a single sample.  In their test methods they refer to this as "Precision" and there is also a section called "Bias".  The bias section is intended to state possible deviations due to human error of the test.  The sections of the ASTM methods have been invaluable to me in determining if we have problems in our laboratories.  Not only can it help to show if we should redo a test or not but it can also help in dispute resolution with outside laboratories like Caltrans.  Knowing how much a test result varies can not only make you look more knowledgeable but gives credibility to your laboratory's test results. 

Which brings me to my next point.  Knowing the precision range of a test result can help you in conversations with your plant operators.  When reporting an out-of-spec test result to a plant operator you often get a lot of finger pointing.  No one likes hearing that something they made was of poor quality and often times, instead of looking for a solution, you will see people try to place blame for who's fault it is.  I can't count how many times I've been told that our test result is wrong and that our material was in spec.  By showing a plant operator a small range of deviation between your test results vs. the allowed range by the test you have a higher chance of convincing them that there is truly a problem with the material and not the laboratory and can start looking for a solution that much faster.  However, on the reverse side of things, knowing the precision range of a test can also let you know when your laboratory is having problems so make sure that you are using this tool fairly and make sure to look at the laboratory if you see an out-of-precision set of test results. 

But back to my original problem, the differing test results between labs.  Our differing test results were indeed outside of the ASTM recommended precision range.  The first step in dispute resolution is ALWAYS look at yourself first.  Not only can this eliminate a lot of headache and embarrassment if you were wrong, but it can save your relationship with other people, people you may need someday in the future.  Our technician did just that and retested his sample and found that his test result was repeatable in his lab.  His next step was to alert everyone involved of the discrepancy.  This is what I would call the second step of dispute resolution, communication.  He asked that all of the parties involved re-examine their testing procedure and determine if there had been an error.  After examining the equipment at the other lab it was found that their solution bottle was expired and this had been the source of discrepancy in their test results.  Which brings me to the third step of dispute resolution, resolution.  Our technician did not decide that his job was done when he proved that his test result was the correct one.  Instead, he took the next step and asked himself how they would avoid this problem in the future.  He asked that all parties involved get together to review the test procedure together to be sure that both labs were performing the test the same and with the right equipment.  You see, the trick about quality control is that it is all about doing things consistently.  Even if you follow the test method to the tee there is still a lot of grey area where a technician can take a liberty that can change the entire test result.  The secret to assuring that your test results match those of another technician, laboratory, or government entity is communication and making sure that you are all doing the test exactly the same.  If our technician would have immediately accused the other lab of doing the test wrong they would have most likely gotten defensive and even if they HAD found something wrong with their testing they may have kept it to themselves out of spite.  With a bit of prep work and good communication, we are able to all sit down together with a solution for the future. 

Welcome to Quality Control, the epicenter of communication.      



As an engineer in the Aggregate and Asphalt industry of California I've seen a lot of changes over the last five years.  One of the biggest changes has been the culture change from making and selling whatever we want to a quality based culture where we can't sell a product if it doesn't meet the right specifications and if we ship poor quality material to a job it is ripped out and returned with a huge reimbursement price tag attached.

It has been a pretty spectacular thing to watch but even now companies across the state are really struggling with the idea of "Quality" and what it means to their bottom line.  What I can tell you for sure is that it means higher costs and higher prices but overall it means better products.  With better products comes fewer returns and longer life out of our roads and structures.  The problem is that we're not all on the same page with quality and it creates a sense of chaos at many companies where they have been doing things in the same way for fifty to one hundred years.  The construction industry is not one to easily change but with new regulations and specifications...those companies will have to shape up or close up because quality is here to stay.

This blog is my attempt to help in educating the construction industry of California to what a quality product really is and how to make their products into something they can sell.  Feel free to comment or add your own expertise, quality control is still changing every day and I'd love to hear from you too!