Duff Abrams announced his water-cement ratio theory (or as he called it, the “water ratio”) in Lewis Institute Bulletin 1, “Design of Concrete Mixtures”. While it was the water-cement ratio relationship that gained Abrams historical acclaim, another of his innovations that is used every day in the concrete industry was also introduced in that publication – the fineness modulus (FM). While we primarily use it today to describe the fineness of sand, Abrams used it as a mix design method and addressed the combined fineness modulus of both coarse and fine aggregate. This article won’t attempt to repeat all of Abrams article, but just give you the high points. If you want to use the combined FM to develop your own mix designs, I suggest you read the entire publication. Continue reading Concrete Mix Design: Art and Science – Combined Fineness Modulus
Now that we have finished discussing particle packing techniques (although there is still a lot more to say about the subject) we can turn our attention to the more common combined aggregate grading techniques used in designing concrete mixes. As has been previously discussed, even though particle packing and voids techniques are more directly associated with concrete performance, combined aggregate grading techniques are easier to calculate with minimal testing and they approximate the results of the particle packing technique. For the next couple of months I want to talk about some different combined grading approaches and the strengths and limitations of each. However, before we talk about the combined grading techniques, I think it would be helpful to review how to calculate a combined aggregate grading. Continue reading Concrete Mix Design: Art and Science – Calculating a Combined Aggregate Grading
I am now back in my office after 4 weeks of travel. Since the last week of September I have been to Las Vegas twice, Birmingham (the home office) and Phoenix. It is good to be home. Now, like a good blogger, I want to fill you in on my findings at the NRMCA ConcreteWorks, Command Alkon’s Customer Conference and ACI’s Fall Convention. Continue reading 2013 Fall Industry Meetings
Just when I was getting ready to produce my final entry on particle packing I realized that so far we haven’t discussed the second most important concept in particle packing – the “wall effect”. First, though, I would like to thank Joe and Mike for their recent guest blogs. I hope to have more guest columns soon.
The wall effect describes what happens when aggregate reaches the concrete form. Since aggregate can’t penetrate the form, only a small portion of the aggregate will be in contact with the form, reducing the density of aggregate adjacent to the formwork. This means that, particularly for a concrete member with a high surface area to volume ratio, the amount of coarse aggregate you can put into concrete is more limited than in mass concrete. Continue reading Concrete Mix Design: Art and Science – Particle Packing Hits the Wall
I’d like to thank Michael Whisonant for being a guest blogger this month. Mike is Director of Technical Services for GCC America. In this capacity, he oversees multiple plants across the U.S. If it has to do with concrete QC, Mike has done it. Since it is football season here in the U.S., I think you will enjoy his perspective on concrete QC. For the benefit of our non-U.S. readers, I have added a few comments in [brackets] to explain some of the terms. – Jay Shilstone
The X’s and O’s of Concrete Quality
– Michael A Whisonant PE FACI
Historically our industry, in terms of quality, has put its efforts into making cylinders and testing air. This is what I call “playing defense” when it comes to quality. When you play defense your goal is to prevent people from scoring against you, or preventing the other team from moving downfield. Sure you can score playing defense, and as the saying goes, “defense wins championships”. Though to follow the same saying, how many teams have won championships when their offense never even took the field? Continue reading The X’s and O’s of Concrete Quality – Michael A Whisonant PE FACI
It seems that particle packing has become the “darling” of the mix design intelligentsia. If you want to sound cool you have to talk about particle packing. However, not everyone means the same thing when they talk about particle packing. Some people want maximum packing and minimum voids. Some people refer to “optimized packing”, but what are they optimizing? Before we can successfully talk about particle packing, we need to make certain we are all talking about the same thing. Continue reading Concrete Mix Design: Art and Science – Ternary Packing Diagrams
Hello, everyone. Welcome back to my series on Concrete Mix Design. I have decided that people might be tired of hearing from just me, so I have invited some of my friends who are knowledeable about concrete to do some guest posts. The first of these is Joe Dewar, whose book and software I have mentioned in the past. Joe is an expert in determining concrete mixes based on voids content, which fits right in with our topic. Without further ado, I give you Joe Dewar.
I have been posting the series “Concrete Mix Design: Art and Science” for several months now and I have realized that it is a bit of a pain to try to find the articles to read the series from start to finish. Here is a Table of Contents that will take you through the series. Happy reading! (updated 3/11/14)
- Introduction – http://www.commandalkonconnect.com/2013/06/03/concrete-mix-design-art-and-science-introduction/
- Specifications –
- Aggregates –
- Paste –
- Aggregate Packing vs. Combined Grading – http://www.commandalkonconnect.com/2013/07/30/concrete-mix-design-art-and-science-aggregate-packing-vs-combined-grading/
- Introduction to Particle Packing – http://www.commandalkonconnect.com/2013/08/12/concrete-mix-design-art-and-science-introduction-to-particle-packing/
- ACI 211 and Particle Packing – http://www.commandalkonconnect.com/2013/08/26/concrete-mix-design-art-and-science-aci-211-and-particle-packing/
- Joe Dewar on MixSim – http://www.commandalkonconnect.com/2013/09/09/concrete-mix-design-art-and-science-joe-dewar-on-mixsim/
- Ternary Packing Diagams – http://www.commandalkonconnect.com/2013/09/23/concrete-mix-design-art-and-science-ternary-packing-diagrams/
- Particle Packing Hits the Wall – http://www.commandalkonconnect.com/2013/10/21/concrete-mix-design-art-and-science-particle-packing-hits-the-wall/
- Calculating a Combined Aggregate Grading – http://www.commandalkonconnect.com/2013/11/04/concrete-mix-design-art-and-science-calculating-a-combined-aggregate-grading/
- Combined Fineness Modulus – http://www.commandalkonconnect.com/2013/11/18/concrete-mix-design-art-and-science-combined-fineness-modulus/
- Coarseness/Workability Factor – http://www.commandalkonconnect.com/2013/12/02/concrete-mix-design-art-and-science-coarsenessworkability-factor/
- Mortar Factor – http://www.commandalkonconnect.com/2013/12/16/concrete-mix-design-art-and-science-mortar-factor/
- The 0.45 Power Chart – http://www.commandalkonconnect.com/2014/01/13/concrete-mix-design-art-and-science-the-0-45-power-chart/
- Mix Suitability Factor – http://www.commandalkonconnect.com/2014/03/10/concrete-mix-desgin-art-and-science-mix-suitability-factor/
I plan on continuing the series with more articles on proportioning aggregates, then a series on proportioning paste. After that I will probably do a series on materials, testing and special conditions.
To wrap the whole thing up, I will probably compile everything into an e-book.
Of course, as they say, “If you want to make God laugh, tell him your plans.”
I hope you enjoy this series.
For as long as I have been around concrete the two primary methods of proportioning concrete mixtures have been ACI 211 and British Road Note 4. Of course it seems that every country, government office and consultant has their own favorite mix design method, but as far as I know, those are still the only two internationally recognized methods for “concrete mix design”. Of course, growing up on the west side of the “pond”, I learned ACI 211. So why am I lumping ACI 211 in with particle packing procedures? It doesn’t use the ternary packing diagram so common in contemporary particle packing discussions. Instead ACI 211 simplifies particle packing by starting with the maximum packing of the largest particles (coarse aggregate), then provides a guide to reducing the coarse aggregate to produce a workable mix. Continue reading Concrete Mix Design: Art and Science – ACI 211 and Particle Packing
The next few articles in this series will discuss particle packing techniques for proportioning aggregate. The concept behind particle packing is that the more coarse and fine aggregate that can be placed into a container, like one cubic yard or one cubic meter, the less room will be available for paste, meaning that both water and cement can be reduced. The part that is usually unspoken when discussing particle packing is that the resulting concrete mix must still be workable. Continue reading Concrete Mix Design: Art and Science – Introduction to Particle Packing