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
The first question most people ask about concrete is, “How strong is it?” Yes, there are other important characteristics about the concrete, but strength is usually the most important one. In fact, most “hidden concrete”, such as footings, columns, beams and slabs, really is not affected by durability concerns. The primary function of the concrete is to provide support. If we don’t need to worry about maximum water/cementitious ratios for durability concerns, there are other ways to design mixtures just for strength. When concrete has a prior performance history the primary way we determine the cementitious content of concrete is through the use of statistical overdesign techniques, such as are in ACI documents. Continue reading
It sounds so easy to say, “Design a concrete mix using a water/cement ratio curve”, but it isn’t. Finally in this mix design series we are talking about concrete and not just components. However, there are a number of steps we have to go through before we cast our first trial batch. Continue reading
Have you ever started a project, then realized that the only way you can begin your project is to do 3 other projects first? Sitting down for the third time to write an article on water/cement ratio curves, I am reminded once again how concrete imitates life. Another thing I have discovered is that when I have trouble writing an article, it is usually because I don’t understand what I am writing about, even if I think I do. I have been having a problem writing about water/cement ratio curves because they aren’t just about paste and water and cement, as I have previously implied, but about an entire concrete mix. Continue reading
As we continue on our discussion of “Concrete Mix Design: Art and Science” I would like to move on to a discussion of “paste”. We have already discussed paste near the beginning of this series (http://www.commandalkonconnect.com/2013/07/15/concrete-mix-design-art-and-science-paste/) and, after rereading it, it is a pretty good start, but I would like to add a few things to the discussion. Continue reading
Both Concrete Construction and The Concrete Producer magazines have started discussions about batch delivery tickets.
I guess the title says it all. I have been blogging for 2 years! What started out as dabbling in social media has become a habit (nearly). There have been a total of 63 posts, with a cumulative readership of almost 28,000 page views. Typically I get about 200 visitors a week looking at over 400 pages. Your interest and support totally astounds me. Thank you from the bottom of my heart. Continue reading
So far all the combined aggregate grading techniques we have discussed have been determined almost solely based on the combined grading. The Total Fineness Modulus method and the Coarseness/ Workability chart have adjustments for cement factor, but the cement content isn’t the driving force. The Mix Suitability Factor (MSF) technique, developed by Ken Day in Australia, directly incorporates both the cementitious content of a mix and the air content. This technique is very easy to use as a mix analysis tool, but a little harder to use as a mix design tool. Continue reading
Hello, readers. I know I am way behind in posting my next blog entry for the “Concrete Mix Design: Art and Science” series, but a lot has been happening in the concrete world lately. I hope to have the next post in the series tomorrow.
One of the biggest happenings has been the World of Concrete, in Las Vegas. http://www.worldofconcrete.com. This year attendance was low again (I’ve heard it said that there were about 40,000 people, down from an all-time high of about 120,000) but this year we attribute it to the fact that ConExpo/ConAgg will be held in Las Vegas this March (about 3 weeks away). The number and size of exhibits was down as well. I would say the show was at about 70% of capacity. I didn’t really get a chance to walk around the show because I was in the Command Alkon booth most of the time. Even though attendance was low, we had a lot of qualified customers come through and the word is that sales resulting from the show will probably be better than projected. The people who came by were ready to buy. We also got a chance to present our new Precision Temperature System, for tighter control of concrete temperatures during summer and winter, and our new Mobile Connect mobile products. There is a tremendous amount of interest in both products.
Another of the high points of the show for me was when ACI revealed its new logo. http://www.concrete.org/News/NewsDetail.aspx?f=51686562 There were so many of my ACI buddies there that it looked like an ACI convention. President Anne Ellis did the honors, presenting the new logo to a group of about 40 people standing in the aisle next to the ACI booth at WOC. In addition, a group of concrete contractors created a decorative pervious concrete pavement with the new logo. Hopefully it will be on display at ConExpo as well.
Speaking of ConExpo/ConAgg, I will be there in the Command Alkon booth in the South Hall, booth S-61229. Drop by if you get a chance and I will show you the latest, greatest stuff in COMMANDqc, including Incident Tracking and ACI 318 Performance Reporting. www.conexpoconagg.com
Another thing that has taken up a lot of my time lately is the Command Alkon Regional Conference that was just held in Columbus, OH. The Regional Conference is a smaller version of our annual Customer Conference, which will be held in New Orleans, LA this year. http://www.commandalkonconference.com/ At the regional conference we conducted hands-on training of many CA products, including COMMANDqc. In addition, I conducted a 1-day seminar on “Developing your QC Department”, which was designed to provide concrete producer QC departments with a structure for developing and enhancing their QC departments. This is the same seminar I did at the last Customer Conference and it has been very well received both times. We plan to hold another Regional Conference in San Francisco April 23-24. http://www.commandalkon.com/rps/sf/index.html
In addition, the beginning of February I conducted 2 days of classes for the Concrete Industry Management Operations class at Texas State University. My host was highly impressed that none of the students fell asleep during my presentations. Considering my recollections of college days, that is high praise, indeed!
A lot more is coming up in the next few months. I expect to be at most of these functions:
- NRMCA Convention, Las Vegas, NV, Mar 1-3, www.nrmca.org
- ACI Convention, Reno, NV, Mar. 23-26, www.concrete.org
- ACI Strategic Development Council, Atlanta, GA,Feb. 20-12 (I won’t be at this one, but the break-out meeting on Nuclear Concrete ought to be interesting.)
- NRMCA Sustainability Forum, Boston, MA, May 12-15, www.nrmca.org (to be held in conjunction with MIT Concrete Sustainability Hub meeting)
- ASTM C09 Committee, Toronto, ON, Canada, June 22-25, www.astm.org
On top of this I will have various meetings at customers’ sites. I guess I just need to figure out how to put more hours in a day.
Hopefully I will see you at one of the industry events. If not, if you get to Dallas let me know and maybe we can get together.
Again, I hope to have the next installment on my Mix Design series out within the next couple of days. I look forward to hearing from you.