CX FASTSET AC is supplied as a light yellow to white liquid. When added to cementitious mixes it accelerates hydration and enables the water content to perform more efficiently by dispersing agglomerated cement particles. Where there is embedded or prestressed steel or where sulphate resistant cement is used or when steam curing is employed, CX FASTSET AC should be replaced by CX FASTSET AN chloride free accelerating concrete admixture.

Uses: As an accelerator for use in concrete and cement mortar to give rapid strength development for early stripping of formwork and to help resist the effects of frost. Ideal for winter working.

Download Technical Data Sheet


placing of concrete

Allows continued placing of concrete at low temperatures.


Reduces the water

Reduces the water content of concrete or mortar without loss of workability


Reduces segregation

Reduces segregation and increases density and compressive strength



Accelerates the hardening of floors and screeds.


Enables earlier

Enables earlier release from precast moulds thus speeding production


additional frost protection

Gives additional frost protection by reducing the low water content and accelerating hydration of cement

Mechanical Properties
Specific gravity : 1.30 – 1.31 at 300C
Chloride content : Suitable for use with steam cured concrete.
Formwork surfaces At the maximum recommended rate of addition, 3.4 liters/100 kg of cement, the Chloride ion concentration is 0.9% by weight of cement. In unreinforced concrete containing no embedded metal, CX FASTSET AC, at the recommended dosage rates may be used. 
Non-staining Does not stain concrete and can also be used safely with white cement.
Air entrainment: General less than 1% additional air
Compatibility with other admixtures: CX FASTSET AC is compatible with other CHEMAX admixture but should be added separately to the mix. Reduced air content may result when CX FASTSET AC is used in conjunction with some air entraining agents. Consult CHEMAX if other admixtures are to be used.
Compatibility with other cements: CX FASTSET AC is compatible with ordinary and rapid hardening Portland cement but not high alumina or sulphate resisting cements.

Workability :

The addition of CB FASTSET AC without reduction of the water content increases the slump and significantly improves concrete flow characteristics without decrease in concrete strength. 

Setting times:

Typical results using CX FASTSET AC are given in Table 1. 

Compressive strengths:

Typical performance with CX FASTSET AC is given in Table 2 . 

Table: 1

CONTROL 0.59 4 HR 45 MINS 6 HR 30 MINS

Table: 2

Temp. Admixture Dosage/liter
100 kg OPC
W/C Ratio Compressive strength N/mm2
200C NONE 0.59 10.00 34.7 42.0
FASTSET AC 3.4 0.55 22.2 49.7 57.6
190C NONE 0.65 5.6 15.2 28.1 38.6
FASTSET AC 1.7 0.60 7.9 19.2 32.9 41.6
50C NONE 0.65 5.4 16.7 30.9
FASTSET AC 1.7 0.60 8.0 21.0 35.9
20C NONE 0.65 3.6 12.8 26.1
FASTSET AC 2.6 0.60 7.2 19.3 32.0
  • Overdosing :Overdosing will give increased acceleration and workability. Entrained air may increase slightly.
  • Dispensing :The correct quantity of CX FASTSET AC should be measured by means of a recommended dispenser. Consult CHEMAX office or representative for advice regarding suitable equipment and its installation. The measured quantity of CX FASTSET AC should be added directly to the mixer, preferably at the same time as the mixing water.
  • Dosage:
    Above 40C
    ->Concrete & mortar: 1.0 liter (Additional rate per 100 kg cement)
    ->Granolithic floor toppings: 1.7 liter (Additional rate per 100 kg cement)
    ->Blocks: 1.7 - 3.4 liter, Depending on conditions (Additional rate per 100 kg cement)
    From 40C to - 20C: 2.6 liter(Additional rate per 100 kg cement)
    Below - 20C: 3.4 liter, at which rate concrete or mortar will be protected to -50C
  • Curing: Normal good curing practice should be adopted.
  • Cleaning: Spillages of CX FASTSET AC can be removed with water.
  • Packaging : CX FASTSET AC is supplied in 20 & 250 Kg drums.
  • Storage : Minimum of 12 months shelf life provided the temperature range has not exceeded 20C to 500C.
  • Health & Safety instructions : Skin contact should be avoided as the material is slightly acidic. Any splashes should be washed well with water. If contact with eyes occurs irrigate immediately with water and medical advice sought.
  • Fire : CX FASTSET AC is water based and non - flammable.