One question I am frequently asked is, “What is the best way to name my concrete mix designs?” The simple answer is “the way that works best for you.” Unfortunately most people don’t find that to be a satisfying response. I have my own ideas about the best way to name mix designs, but I decided to turn to the real experts – you. I crowdsourced the question (doesn’t that sound more modern than “put out a survey”) and got 62 responses back from people around the world. What you are about to read is a summary of the results, with some of my own commentary thrown in. I need to warn you in advance, this blog post is much longer than my usually post, but I didn’t want to split it into two posts, so here it is in all its glory. Continue reading
One question I get asked frequently is, “What is the best way to name my concrete mix designs?” While some people use sequential mix codes for new mix designs, most people think the mix code should describe the mix design in some fashion. Usually each digit in the mix code will reflect a different aspect of the mix design. For example, 35F6765N would mean:
35 – 3500 psi
F – Fly Ash
67 – #67 (3/4” or 19mm) maximum aggregate size
6 – 6% air entrainment
5 – 5” slump (125mm)
N – Normal water reducing admixture
Of course everyone has a different naming convention depending on their needs. Also, different people have different numbers of characters available depending on the batching system they use.
To try and get a better idea of what people think is important for naming their mix designs, I have created a survey that you can find at https://www.surveymonkey.com/s/NW6W3HF.
If you are a concrete producer I would appreciate it if you would take the survey. If you do and you provide me with your email address at the end of the survey I will send you a copy of the complete results after I compile them (probably around the middle of July, 2015). I will also publish a summary of the results in this blog then.
I greatly appreciate your willingness to share your mix naming philosophy with the readers of this blog.
Here we are, only a week after my 3rd anniversary with my blog and I have another milestone to announce. My blog has just hit 50,000 pageviews. FYI, it took 22 months to get 20,000 views, but only 14 months to increase to 50,000. I owe it all to my readers, so thank you very much. If you want a summary of my recent posts check out my previous entry about my 3rd anniversary.
I begin this post the same way I began my first post, three years ago today. Who would have believed I would have lasted this long writing a blog. My father was always the one who enjoyed writing magazine articles, while I preferred to play with computers. It seems that I found a way to do both, so the apple didn’t fall too far from the tree. I thought today I would give you a view of the results of this blog. Continue reading
When I first started this blog almost 3 years ago I posted an article entitled “If I Ruled the Concrete Industry”. The article presented 5 changes that I felt needed to be made to the concrete industry. Responses that I received to my most recent post on the fact that concrete producers are not being sent concrete tests as required by the Building Code have pushed me to recognize that the 5 changes I suggested are really symptoms of the same thing, at least here in the U.S. That conclusion is that in the U.S. we are operating under an inappropriate paradigm when it comes to designing, specifying, manufacturing, constructing and testing with concrete. We need to change the paradigm so that the entire design and construction industry takes a more professional approach to the design and use of concrete. Continue reading
If you were to walk into an Engineer’s office and tell him to reduce the reinforcing steel in a structure or to cut back on the design strength he would probably think your were crazy (or part of the Mafia). However, many Engineers, Owners, Contractors and Laboratories routinely violate the Building Code and possibly endanger workers and the public. It is time to put an end to this unsafe practice and comply with the Code. What heinous crime am I referring to that endangers the public? It is the practice of not providing concrete test results to the concrete producer.
I had really planned on stopping the section with my last entry on “Statistical Overdesign by EN-206” but quickly realized there are still a bunch of bits and pieces about this topic still floating around that need to be pinned down. Since the series started there have been updates on ACI 318 and EN-206. Also, there are considerations for other documents, including ACI 301, “Specifications for Structural Concrete” and ASTM C94, “Specification for Ready Mixed Concrete”. Continue reading
At the American Concrete Institute Fall 2015 Convention in Washington D.C. I delivered a presentation entitled “Particle Packing from a Rock’s Perspective”. ACI has just posted the presentation on YouTube at http://youtu.be/JamUGG3-DSg. If you are looking for a stuffy presentation filled with facts and figures, this presentation isn’t for you. If you want to find out what rocks think about particle packing, drop by and meet Rocky. Hey, its only 12 minutes long. What can you lose?
My past couple of posts have been about statistical overdesign using ACI 318, so I thought this time I would discuss the overdesign technique used in EN-206. After all, EN-206 uses a similar statistical method to ACI 318, right? Wrong! What started out as a simple 2 hour exercise in paraphrasing EN-206 has turned into a major effort involving about 20 people on 3 different LinkedIn groups. One of my favorite sayings has come to be, “If you want to make God laugh, tell him your plans.” My only consolation from this blog post is that God must have gotten a real belly laugh. Continue reading
When determining the required average compressive strength, f’cr, by ACI 318, the Structural Concrete Building Code, the Code cites the preferred option of using 30 consecutive tests to determine the sample standard deviation, then to use that standard deviation to calculate the overdesign above specified strength, f’c. Fortunately the Code recognizes that not every concrete producer will have 30 consecutive tests for every combination of materials and provides options for other alternatives. In my last blog post we looked at determining required average compressive strength using 30 tests. In this post I would like to examine the other options. (NOTE: There are many details in ACI 318 that are not covered in this post. This post just covers one aspect of ACI 318. If you must develop a concrete mix in compliance with ACI 318 it is strongly suggested that you first obtain a copy of that document. Copies are available from ACI at http://www.concrete.org .) Continue reading