To make concrete flow, you add admixtures to it, typically after the concrete has arrived at the job site. This process temporarily increases the concrete's workability and slump.
Understanding Flowing Concrete
Flowing concrete, also known as self-consolidating concrete (SCC) or highly flowable concrete, is designed to spread easily and fill formwork without requiring significant vibration. This characteristic is achieved by modifying the concrete mix, primarily through the use of chemical admixtures.
The Key Method: Adding Admixtures
Based on the provided reference, the primary way to make concrete flow is by:
- Starting with a concrete mix that has a normal slump (e.g., 2 inches).
- Transporting the concrete to the job site.
- Adding the proper amount of admixtures to the concrete after its arrival.
- Ensuring the admixture is thoroughly mixed in.
This process results in a mix with a temporarily higher slump, making it flowable.
Types of Admixtures Used
The admixtures most commonly used to make concrete flow are superplasticizers (also called high-range water reducers). These chemicals significantly improve the workability of concrete without adding extra water, which would weaken the final product.
Why Use Flowing Concrete?
Using flowing concrete offers several benefits:
- Faster Placement: It fills forms quickly and efficiently.
- Reduced Labor: Less vibrating is needed to consolidate the concrete.
- Improved Finish: Can result in smoother surfaces and better-filled corners.
- Easier Placement in Complex Forms: Ideal for intricate shapes or areas with dense reinforcement.
Practical Application
Making concrete flow is a controlled process. The amount and type of admixture must be carefully measured and mixed to achieve the desired slump and performance without negatively impacting the concrete's strength or durability. It's crucial that the admixture is uniformly distributed throughout the mix.
Steps summarized:
- Mix standard slump concrete.
- Deliver to site.
- Add superplasticizer or similar admixture.
- Mix thoroughly on-site.
- Place the now-flowing concrete.
This method allows concrete suppliers to deliver standard mixes, and adjustments for flowability can be made precisely where and when needed, accounting for transport time and site conditions.
