pozzolan and cement clinker material

Pozzolan

A Pozzolan can be explained as a siliceous material that's non-hydraulic, but which can be able to combine with lime and water at normal (ambient) temperatures to make hydrates with cementing properties Due to the microporous structure of several pozzolans they can be an easy task to grind to products of high specific surface. Although amining equipment mining equipment machinery manufacturer gold pdfn easy task to grind pozzolans tend to be quite abrasive plus they may frequently have a moisture content that needs provisions for drying within the grinding circuit.

Pozzolans generally contribute less quickly to strength than GBS. Because of this, and quite often also as a result of difficulties with water demand, the fraction of natural pozzolans in pozzolan cements is normally kept below 35%.

In the merchandise from combined grinding of pozzolan and cement clinker the pozzolan is going to be expected to be very fine and also the clinker part to be very coarse because of the large difference in grindability of these two materials. This will in general terms result in a strength development with low early strengths and high late strengths. Further, Portland- Puzzolan cement from combined grinding will tend to have an increased water demand - as a result of very fine pozzolan - when compared to a product mixed of separately ground components with individually optimized particle size distributions.

Fly Ash (PFA)

Fly ash (or Pulverized Fuel Ash = PFA) is an artificial pozzolanic material with a reactivity similar to the reactivity of natural pozzolans. Hence, practical clinker replacements are normally below 40% with 20-30% as a typical range.

The particles of PFA are mainly spherical, having a portion being hollow. The fineness of PFA usually varies between 200 and 500 m2/kg (Blaine), (or 45 µm residues of 10-40%), meaning that it features a fineness similar to those of Portland cement. Therefore PFA is often introduced into blended cement with little or no grinding at all. If grinding is performed it's going to first result in crushing from the hollow and porous particles. A subsequent further grinding of the dense glassy material are usually rather energy consuming.

PFA is normally available like a dry powder ideal for pneumatic transportation.

A comparison from the three methods of making fly ash cement - combined grinding, separate grinding and direct intermixing from the PFA since it is received - established that one of the most favourable ratio between cement strength achieved and also the corresponding grinding energy is obtained with combined grinding. The direct intermixing of the PFA supplies the poorest solution with the three.

In many plant partial combined grinding is implemented in how the PFA is brought to the separator - no matter the kind of grinding circuit - and just the coarse particles are returned for the mill for more grinding. Those particles and agglomerates are then reduced in size as well as the reactivity is improved.