INSTRUCTIONS: View the recorded webinar. Complete 10-question quiz with a score of 80% or higher to receive a certificate for 0.1 CEU (equivalent to 1.0 PDH).
Continuing Education Credit: 0.1 CEU (1.0 PDH)
Approved AIA and ICC
Access Period: 30 days
This is a recorded webinar from March 6, 2019.
“Mix Design” is an interesting, challenging, and fundamental task. The objective is to predict the relative quantities of ingredients that will reliably and economically meet specifications and satisfy the needs of the concrete producer and contractor. A wide variety of “mix design” methods are used, varying from simple volumetric batching (by hand) of a 1:2:3 mix, to sophisticated, computer-based techniques, all of which are intended to produce a good-first-guess called a “trial mix.”
Then the trial mix has to be evaluated at lab- and field-scale, with the expectation of making adjustments based on continued monitoring of performance. In this test-and-adjust process, actual concrete performance matters more than the mix design method because there are no guarantees in mix-design, and each mixture must account for the characteristics and variability of local materials. Even though most concrete is batched by weight, a lot can be learned by looking at the relative volumes of paste, air, and aggregates. And regardless of the method, three key parameters that define concrete performance, i.e., water-content (defining workability), water-cement ratio (dictating strength and durability), and total cementitious materials (dictating cost, heat, chemical reactivity, and shrinkage-tendency) cannot be independently selected. At best the mix designer can independently select any two of the three, and accept the dependency of the third…or turn to admixtures and specialized aggregate grading.
Author: Ken Hover
Categories: Concrete Fundamentals, Design, Mixture Proportioning
Formats: Online Learning
Table of Contents
1. Recognize that efficient mixture design results in a trial mix that can be readily adjusted to efficiently meet required concrete performance, and that performance is more important than the mix design method.
2. Explain why the word “design” in the phrase “Mix Design” may not carry the same implications as use of the same word in the phrase “Structural Design.”
3. Discuss valuable insight to concrete performance by examining volumetric proportions, even though concrete is typically batched by weight.
4. Summarize the trade-offs in concrete properties in a conventional mixture, workability, w/c, and total cementitious materials content are not independent.
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