Does Pumping Concrete Change Slump?

Pouring concrete is a bit of an art. It's not just about getting the mix of water, cement, and aggregates right; you also need to use the correct tools and techniques when pouring it onsite. Add in a pump to the equation, and you have a whole new layer of complexity to deal with.

If you're thinking about renting a concrete pump for your next project, you might be worried about how pumping could affect your concrete's slump. It's a valid concern: slump level can be the difference between a strong, quick-drying foundation and a total disaster.

Not to worry. The concrete experts at 2 Brothers Concrete Pumping are here to explain everything you need to know about how pumping affects slump, including what you can do to minimise any negative impacts. Let's dive in!

What Is Slump?

Firstly, what does 'slump' actually mean?

Slump is a measure of concrete's workability, which is essentially how easily it flows. A higher slump (wetter mix) flows better but might be weaker, while a lower slump (drier mix) holds its shape but takes more effort to pour or pump.

Neither a higher nor lower slump is 'better' by definition, as the ideal slump really depends on the specific project. For instance, a higher slump tends to be better when dealing with dense reinforcement in a structure, such as heavily reinforced slabs, beams, or columns. This is because it allows for better flow and easier consolidation around the steel. On the flip side, going for a lower slump is usually the better option when constructing walls, columns, or other vertical elements, as it reduces the risk of concrete flowing downward due to gravity.

How Does Pumping Affect Slump?

Simply put, it depends.

Pumping can affect the slump of concrete in several ways, both increasing and decreasing its flowability. It's more common for it to lead to slump loss, due to a few reasons:

• The pressure from pumping can force water into the pores of dry aggregates, reducing the amount available for flow and leading to a stiffer concrete. This is especially a risk for porous materials like pumice or limestone.
• Pumping can also squeeze out entrained air bubbles, which help concrete flow and resist cracking. This loss results in a denser, less workable mix.
• The friction of concrete moving through the pump hose can cause some internal breakdown of the mix, impacting its consistency and potentially reducing slump.

On the flipside, pumping can lead to slump increase. The shearing action can break down clumps within the concrete, making it slightly more fluid and increasing slump. However, this effect is usually minor and outweighed by the factors mentioned above.

Can You Prevent Slump Loss From Pumping?

Thankfully, there are a few steps you can take to mitigate the effect pumping has on slump. Here are the most important ones:

• Design your mix carefully, making sure you use the right proportions of water, cement, and admixtures. Concrete mixtures used for pumping typically have higher slump values so they can flow easily through the pumping system without clogging or blockages.
• Use the right pump pressure. Make it strong enough for the concrete to move through the pipes, but not so strong that it reduces the water and air in the mix.
• Consider adding admixtures such as water reducers or superplasticisers to the concrete mixture to maintain or control slump during pumping. These admixtures help improve the workability and flow of the concrete without significantly increasing the water content.

While pumping can affect slump, it's not an automatic death sentence. Careful planning, mix design, and pumping practices can make sure your concrete arrives with the right consistency to get the job done.

Talk to the South's Go-To Experts in Pumping Concrete

Of course, this is just a general overview. How pumping affects slump depends a lot on the materials and conditions involved, so it's always best to consult with concrete professionals like the team at 2 Brothers Concrete - they'll help you make sure the mix design and pumping procedures you use are right for your needs.

With over 25 years of combined experience, we know more about concrete and pumping than anyone. No matter the scale or complexity of your project, we can provide a solution that effectively addresses all your concrete requirements.

Our concrete services include concrete pump hire, ready mix concrete supply, and liquid screed supply. We're also here to assist you throughout your project and answer any further questions you may have about concrete slump and pumping.

Ready to get started? Book our concrete services online or give us a call on 01489 552737 today!