Red Seal Concrete Finisher Practice Exam

How is the slump of concrete measured?

1. Using a thermometer

2. Using a slump cone test

3. Using a weight measurement

4. Using a water displacement method

The correct answer is: Using a slump cone test

The slump of concrete is measured using the slump cone test, which is a standardized method that assesses the consistency and workability of fresh concrete. This test involves filling a conical mold, known as a slump cone, with freshly mixed concrete and then carefully lifting the cone vertically. The distance that the concrete slumps or settles can then be measured, indicating its fluidity or rigidity. The significance of measuring slump lies in its relationship with the concrete's water-to-cement ratio, which directly influences the strength and durability of the cured product. A higher slump indicates a wetter mix, which might be more workable but could also lead to lower strength if excessive water is present. Conversely, a lower slump indicates a stiffer mix, possibly making it harder to work with but potentially yielding higher strength once cured. Other methods, such as using a thermometer or weight measurement, do not accurately assess the flow properties of concrete, as these techniques measure temperature and weight, respectively, which are not related to the workability or consistency of the mix. The water displacement method also does not provide the necessary information regarding the flowability and handling characteristics that the slump test specifically addresses. Hence, the slump cone test is the most appropriate and widely used method for evaluating concrete slump.