Concrete Mix Design: Art and Science – Introduction to 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

Concrete Mix Design: Art and Science – Aggregate Packing vs. Combined Grading

It is now time to start discussing the “how to” of selecting aggregates for a concrete mix design. You will find there is no single “best method” for proportioning aggregates. Aggregate design methods basically fall into 2 different categories: particle packing methods and combined grading methods. Each method has multiple variations and each variation has its own strengths and weaknesses. Continue reading Concrete Mix Design: Art and Science – Aggregate Packing vs. Combined Grading

Koncrete at the Kimbell – New Architectural Concrete Addition

A couple of weeks ago Dan Simoneau, a Project Manager at Capform, invited me to drop by and see the cast-in-place architectural concrete work they have been doing at the Kimbell Art Museum in Ft. Worth, Texas. https://www.kimbellart.org/ For those of you that aren’t familiar with the Kimbell, it was designed by Louis Kahn and is widely recognized as a prime example of CIP architectural concrete. Now the Kimbell is adding the Piano Pavillion, named for renowned architect Renzo Piano and not for the musical instrument. With BECK as the General Contractor, Capform provided the forming and placing services for the project. If you understand architectural concrete and know what you are looking at, the results this group have achieved are nothing short of amazing! Continue reading Koncrete at the Kimbell – New Architectural Concrete Addition

Concrete Mix Design: Art and Science – Paste

It is now time to talk about the most interesting part of concrete – the paste. Paste is the weakest, least durable and most expensive part of concrete, but concrete wouldn’t work without it. Unfortunately, paste is also the most complicated part of concrete to discuss. If you really want to understand it, you have to talk to a cement geek, and I am not a cement geek. In fact, I only know the bare basics about cement and paste. If you want to know a little more, check out the Integrated Materials and Construction Practices document from FHWA at http://www.cptechcenter.org/publications/imcp/. If you really want to go down the rabbit hole, talk to the good folks at the Portland Cement Association, http://www.cement.org. If you just want to know enough to get by in the concrete world, keep on reading. Continue reading Concrete Mix Design: Art and Science – Paste

Concrete Mix Design: Art and Science – Aggregates

Hello, concrete aficionados! (I assume only those who are really interested in concrete will be taking to time to read about something as boring as rocks and sand.) Today’s post will discuss the role aggregates play in concrete. We aren’t going to get into how to calculate rock and sand quantities – that come later. Instead we are going to discuss why aggregates are important in concrete and what role they play. Once you understand that you will understand how to proportion aggregates for a concrete mix. Continue reading Concrete Mix Design: Art and Science – Aggregates

ASTM 2013 C09 Summer meeting in Indianapolis

My normally scheduled blog date is not until next Monday, but I wanted to do an entry on the ASTM meeting in Indianapolis 2 weeks ago and didn’t want to interrupt my Mix Design series, so you get an extra entry this week.  This ASTM meeting is the one about concrete and concrete aggregates. The C01 meeting on cement was held immediately afterward, but I didn’t get to hang around for that. There were meetings going on in 5 rooms simultaneously, so it was impossible to attend everything. My major emphasis was on the C09.40 meeting on concrete production and the C09.20 meeting on aggregates. Following is a summary of some of the major items being discussed in those meetings. Continue reading ASTM 2013 C09 Summer meeting in Indianapolis

Concrete Mix Design: Art and Science – Introduction

DSCF0006We are rapidly approaching the 100th anniversary of the 1918 publication of Lewis Institute Bulletin No. 1, which contains Duff Abrams’ theory about the water/cement ratio. You would think that in 100 years the concrete industry would have performed enough research that the concrete mix design process would be standard.  After all, there are only so many ways you can combine rock, sand, cement and water. The trouble is, there are so many ways you can combine rock, sand, cement and water – basically an infinite number. Not only are we unable to determine the best way to blend these 4 materials, but we are also unable to quantify some materials’ characteristics, such as particle shape and texture, as well as unable to characterize concrete performance, such as workability and segregation potential. For these reasons, and many others, concrete mix design is almost as much art as it is science. Continue reading Concrete Mix Design: Art and Science – Introduction

NRMCA 2013 Concrete Sustainability Conference in review

Two weeks ago I was just south of beautiful San Francisco to attend the NRMCA’s Concrete Sustainability Conference (along with the Research, Engineering and Standards Committee meeting). In the past, it seemed that most of the presentations at the CSC revolved around people saying, “My concrete has more fly ash (or slag, or magic pixie dust) than yours.” This year was different! While the materials people still led the way with “better concrete through modern chemistry”, there were other voices added to the choir. Continue reading NRMCA 2013 Concrete Sustainability Conference in review