Concrete workability is a critical factor in various construction scenarios, such as deep beams, thin water-holding structures, column-beam connections, and concrete pouring in hot weather. Achieving the right level of workability is essential for successful construction outcomes.
In many cases, practical considerations may lead to the temptation of adding extra water to concrete on-site, but this can have negative consequences. While water makes concrete more flexible, it doesn’t necessarily improve its overall consistency. Excessive water can lead to workability, but it won’t result in a more uniform mixture. Unfortunately, this practice can compromise the structural integrity of the concrete and, in extreme cases, pose safety risks.
To address workability challenges without compromising strength, plasticizers come into play. These chemical admixtures serve to improve concrete’s workability without resorting to excessive water addition. Plasticizers, water reducers, superplasticizers, or dispersants can be employed to make the concrete mix more manageable and less time-consuming.
Plasticizers are substances added to concrete to enhance its workability. They are often used alongside pozzolanic ash when creating high-strength or fiber-reinforced concrete. The addition of 1 to 2 percent by weight of plasticizer to cement is typically sufficient. However, caution is advised to prevent issues like concrete separation.
Plasticizers contain polymer molecules that, when added to concrete, adhere to the surface of cement grains, forming ionic groups. This process results in cement particles acquiring a negative charge, causing them to repel each other. As a result, the concrete paste becomes smoother and more user-friendly.
Plasticizers come in various forms, such as polyglycerol esters and lingo sulfates, with dosage ranging from 0.1% to 0.4% by weight of cement.
Types of Plasticizers in Concrete
Hydrophilic Plasticizer : Improves concrete’s plastic and flow properties by increasing wet ability.
Hydrophobizing Plasticizer : Increases air content in the mix, making the concrete more flexible.
Plasticizers serve multiple purposes, including making concrete more flexible, reducing film cracking, enhancing workability, and lowering water content.
Advantages of Plasticizers
In conclusion, plasticizers play a crucial role in improving concrete workability, performance, and durability. They offer advantages such as increased strength, ease of shaping, and improved resistance to cracking. However, it’s essential to use plasticizers responsibly, considering their potential environmental impact. Choosing safe and effective materials is paramount for responsible concrete construction.
