Understanding Concrete Slump: What It Means for Your Project

What Is Concrete Slump?

Concrete Slump is a measurement of concrete’s workability. Workability is simply a way of saying how easy it is to pour and shape the fresh concrete. The term “slump” is a measurement of how far a fresh sample of concrete will settle once the container that holds it has been lifted away.

How To Measure Slump

Measuring Slump is quite simple:

• Fill a cone-shaped mold with fresh, mixed concrete.
• Carefully lift the mold off the concrete sample.
• Measure the distance that the concrete settled after the mold was lifted.

The measurement of slump is usually expressed in inches. If the concrete has very little slump, then it is stiff; if there is a lot of slump, it is too thin.

Ideal Slump For Different Applications

Many types of applications have different preferred slumps:

• Foundations & Footings: 3–4 inches
• Sidewalks & Driveways: 4 inches
• Columns & Walls: 4–6 inches
• Floors & Slabs: 4–5 inches
• Decorative or Stamped Concrete: 4–6 inches

For McAllen’s climate, we might adjust those numbers because of the heat and humidity.

Factors That Can Influence Slump

Several things can affect the slump of the fresh concrete:

• Water Content: Adding more water will increase the slump.
• Aggregates: Larger aggregate sizes tend to produce less slump than smaller sizes.
• Temperature: High temperatures can cause the slump to decrease over time.
• Admixtures: Some additives can increase or decrease the slump.
• Time: As the concrete starts to set, the slump tends to decrease.

Problems Caused By Incorrect Slump

If you do not get the correct slump of concrete, you can run into problems:

• Too high: Can cause segregation, bleeding, and lower strength of the concrete.
• Too low: Difficult to put and compact, which results in voids and honeycomb.

Ways That Professional Companies Control Slump:

McAllen Concrete Contractors takes the following steps to make sure that we have the correct slump:

• Testing the concrete at regular intervals during both mixing and placing.
• Making adjustments to the mix design as needed for the project specifications.
• Taking into consideration the environmental factors such as temperature and humidity.
• Adding admixtures as needed to help manage the slump.
• Delivering and placing the concrete at the correct time.

Why Homeowners Should Care About Slump

You don’t have to know everything about concrete; however, knowing something about slump will allow you to:

• Recognize the science involved in creating quality concrete work.
• Realize why hiring a professional company with experience is so important.
• Know why precautions are being taken when laying concrete.
• Allow you to communicate with your contractor about your project and what is going on.

Slump And Your McAllen Project

Because of the hot weather in McAllen, controlling slump becomes even more important:

• We try to do our best to plan our concrete pours for cooler parts of the day.
• We sometimes add ice to the concrete mix to slow down the setting of the concrete and manage the slump.
• We carefully watch the water content in order to achieve the right slump for strength without losing strength.

Common Misconceptions About Slump

There are some common misconceptions about slump:

• Just because a batch of concrete has a higher slump does not mean that it is weak.
• You cannot judge the quality of the concrete solely by the slump value.
• What is the right slump for one project is not necessarily the right slump for another project.

When To Discuss Slump With Us

Here are some times to discuss slump with us:

• When planning a large concrete project.
• When working on a project that has special strength requirements.
• When dealing with difficult placement conditions (such as narrow molds or heavily reinforced areas).

At McAllen Concrete Contractors, we are committed to providing the right concrete for every job. Because we understand the variables involved in producing concrete (such as slump), your driveway, patio, or foundation will not only look good but also last long and perform well.

Although it is nice to understand the concept of slump, it is just one of the many things involved in the process of creating a great concrete job. Trust in the knowledge of experts who consider all the elements of the production process (from mix design to the curing of the concrete) to provide the highest quality concrete job possible.

Want to learn more about the technical aspects of your concrete project? Want to start a new project with a team of experts who understand the science behind great concrete? Contact McAllen Concrete Contractors today. We will be happy to answer your questions and provide you with a superior level of service in every single pour.