LESSON 2
PROPORTIONING CONCRETE MIXTURES
OVERVIEW
LESSON DESCRIPTION:
In this lesson you will identify the use of the trail batch and absolute volume methods for proportioning concrete
mixtures.
TERMINAL LEARNING OBJECTIVE:
ACTION: Identify, plan, and use the trial batch and absolute volume methods for proportioning concrete
mixtures.
CONDITION: You are given the materials contained in this lesson.
STANDARD: Correctly answer all the practice exercise questions at the end of the lesson.
REFERENCE: The material contained in this lesson was derived from the following publication: FM 5-742, with
change 1.
INTRODUCTION
In Lesson 1, "Concrete Components," you learned the desirable characteristics that we seek in portland cement
concrete. This lesson discusses how these characteristics are obtained. In designing a concrete mix, you must
answer the following questions concerning your particular job.
1.
What structural qualities do I want my hardened concrete to provide?
2.
How do I want the plastic concrete to act?
3.
Are my aggregates suitable? How do they affect the workability of the mix?
4.
What is the proper mix of ingredients?
Consider how you would answer each of these questions then continue on and see how your concrete instructors
answered them.
1.
What structural qualities do I want my hardened concrete to provide?
You want your concrete to display strength, durability, and watertightness.
Since the w/c ratio
affects each of these, you will select a w/c ratio to meet each of these requirements. Also, since
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