Fly ash for concrete

Fly ash from hard coal combustion is a renowned addition for production of ordinary concrete, which has been confirmed by numerous research and implementations worldwide for over 60 years.


The most important arguments confirming suitability of ash include:

  • improvement of concrete workability properties
  • improvement of tightness of a structure
  • reduction of hydration heat 
  • increase of resistance to chemical aggression
  • participation of ash in cement binding reactions 
  • higher resistance of concrete over long period of time
  • reduction of production costs of the concrete mixture.

According to PN-EN 206-1 fly ash is treated as type II mineral addition, i.e. fine-grained non-organic material with pozzolanic properties.
Detailed conditions, which have to be fulfilled by ash for concrete as specified in PN-EN 450 “Fly ash for concrete”, where categories of fly ash are distinguished depending on loss on ignition:

Fly ash of class A no more than 5.0% of weight
Fly ash of class B no more than 7% of weight

and depending on fineness (amount retained on 0,045 mm sieve):

Fly ash of class N no more than 40.0 % of weight
Fly ash of class  S no more than 12 % of weight

Requirements of chemical properties::

chemical properties requirements of the standard
Contents of Cl- ≤ 0,10 % of weight
SO3 ≤ 3,0 % of weight
Contents of free reactivated calcium CaO ≤ 1,5 % of weight
Contents of reactivated silica SiO2 ≥ 25 % of weight
Contents of the total of oxides (SiO2, Al2O3, Fe2O3) ≥ 70 % of weight

Requirements of physical properties

physical properties requirements of the standard
Activity index po 28 dniach ≥ 75 %
  po 90 dniach ≥ 85 %
Volume stability   ≤ 10 mm
Volumetric density +/- 200 Kg % 

 Influence of fly ash on properties of fresh concrete

Basic changes occurring due to use of fly ash include demand for water and workability. For stable workability, the demand for water usually decreases by 5 - 15 % as compared with a mixture of the same binding material containing Portland cement only. The concrete mixture including fly ash is cohesive and shows reduced tendencies for draining. The mixture may be pumped and moulded with the use of a sliding method and concrete finishing operations using fly ash are simpler. Influence of fly ash on properties of fresh concrete is connected with the shape of fly ash. Most of its grains are spherical and this property has been assigned with an effect of “bearing balls”, which improves workability. Fly ash delays the mixture binding.

Influence of fly ash on concrete durability

Fly ash added leads to limitation of alkali-silica reaction. Based on the current experience in application of fly ash for concrete, fly ash has been known to reduce durability of concrete cutting for 28 days. Following the period of three months, durability of concrete with fly ash added becomes usually similar to durability of the same concrete, which, however, was made with the use of cement. Later, following a longer period of curing, durability of concrete with fly ash added is usually higher than that of comparable concrete. This results from pozzolanic reactions, which are long-term processes and they also found that during the period of one year, approx. 50 % has not reacted yet. The delay in binding and slowing down of concrete hardening contributed, on the other hand, to decrease of thermal effects of hydration of the mixture components.

The company’s documents permitting use:


Technical advisor and sale:                       

Region West:
Waldemar Żelazowski - tel. +48 605 434 370, e-mail: l

Region South:
Sebastian Bochenek - tel: + 48 516 781 770, e-mail:

Region East:
Sebastian Kotyczka - tel. +48 661 925 651, e-mail:

Region North:
Michał Kutyłowski - tel: +48 722 030 025, e-mail:

Customer Service (sales: invoices, payments) - tel. +48 32 4294 768, -769

Logistics (notification on collections and supplies):
Region West (Wrocław, Siechnice, Kamień) - tel. +48 515 197 505
Region South (Rybnik) - tel. +48 502 292 380
Region North (Gdańsk, Gdynia i Toruń) - tel. +48 721 211 105
Region East (Kraków) - +48 887 071 190