IN winter, the colder ambient temperatures can cause delays in concrete strength development as well as finishing aspects. This is a real headache for contractors and precast production plants, but the challenge can be easily overcome using specially designed admixtures, or accelerators.
Accelerators are normally categorised as chloride and non-chloride based. A popular chloride-based accelerator commonly used by many dry precast operations is CHRYSO Xel C205.
According to CHRYSO, this product, based on calcium chloride, is an accelerating admixture which enhances the early stages of cement hydration which in turn enhances rapid stiffening and hardening of the concrete mix.
“The result is that final finishing or mould stripping can begin at an earlier age without damaging the concrete surface increasing productivity,” the company said in a statement.
It added that in the winter months, CHRYSO Xel C205 assists in overcoming delays in concrete finishing caused by cold weather. Supplied as a clear solution, it instantly disperses in water. It can be used in applications that do not contain embedded metal, and in foamed mortar systems.
It is compatible with other CHRYSO admixtures used in the same concrete mix. It can also be used with all types of ordinary Portland cements and cement replacement materials such as pulverised fly ash (PFA), ground granulated blast-furnace slag (GGBFS) and silica fume. CHRYSO Xel C205 is available in drum or bulk supply.
For steel-reinforced concrete, the company advises its non-chloride-based accelerating admixture CHRYSO Xel 650. This can be used in all types of cement, and applications include shuttered concrete, pre-stressed concrete, precast elements and readymix concrete.
“The CHRYSO Xel 650 product helps the first reactions of cement hydration, especially at low temperatures. This significantly reduces setting time and improves early compressive strength.”
Packaging options include 25 litre jerry cans, 200 litre drums, 1000 litre flow bins and bulk delivery.
CHRYSO Xel 680 EMx is specifically used in highly extended cements. “It allows for productivity gains through pouring/stripping cycle time reduction. Moreover, it allows the time required and temperature of steam curing to be optimised.”
Customers have access to CHRYSO’s technical advisory service for on-site assistance and advice on admixture selection, evaluation trials and dispensing equipment. Technical data and guidance can also be provided for admixtures and other products for use with fresh and hardened concrete.