Admixtures are chemical additives that are mixed in to a batch of concrete to change its properties in either the plastic (unhardened) or hardened state. We stock a range of admixtures that can be added at a customer’s discretion to adjust the concrete to best suit the customer needs based on the application or the climate at the project. Admixtures that we carry include hardeners, colorants, and water proofers. Please contact us to inquire about admixtures available.
What does “placing” concrete mean?
Placing is the process of distributing and consolidating the concrete from the mixer truck into the forms, moulds, or excavations as required at the job site. Concrete is typically poured into forms using a concrete pumper unit, a conveyor unit, or wheelbarrows, or can be poured directly from the mixer chute depending on the job. Placers will use rakes and screeds (long, straight boards) to move the concrete around within the form to create the correct elevations and profiles for the final product.
What does “finishing” concrete mean?
Finishing is the process of working the exposed surfaces of the concrete after placement to create the desired final appearance. This may include trowelling to create a flat and smooth surface, trowelling in joints to control cracking, brushing for skid resistance, edging, coloring, and stamping for an attractive architectural appearance, wash-off for an exposed aggregate finish, or other techniques.
Placement and finishing have a very significant impact on the final quality of the concrete. In particular, proper finishing can make or break any job, so you should take care to ensure that your placer/finisher is qualified for the work to be done.
Why is it important to place concrete in a certain timeframe?
According to IS Code complete discharge of a batch of concrete must be completed within 2 Hrs after initial mixing unless otherwise agreed by the owner and supplier. In practice, the workability period of a load is impacted by both type of cement used and by ambient climate, and can be modified by set-retarding or accelerating admixtures.
We stock both accelerator and retardant admixtures to enable delivery to remote locations and in both hot- and cool-weather conditions without any loss in final product strength or durability.
Can I add water to the mix at the jobsite?
In past times, water was commonly added to batches of concrete at the jobsite to increase its slump for greater workability and/or ease in finishing. However, adding water also negatively impacts both the strength and durability of the hardened concrete.
As per IS Code there are strict limits on the addition of water to a batch of concrete at the jobsite. We batch our concrete with the correct amount of water at the plant to meet the water/cement ratio required for the mix design in order to meet 28-day strength. We do not recommend adding any water to the mix at the jobsite to improve workability unless directed by an appropriately trained expert. We will require acknowledgement and sign-off by the owner or general contractor that any warranty is voided before water is added at their direction.
If you want greater slump or workability, all our mixers carry plasticizer admixture that can be added at the job to improve workability without any loss in final properties in the hardened state.