Cement

Cement is an ingredient of which raw materials are limestone and clay and which is used in sticking mineral particles(sand, gravel, brick, briquette etc.). Cement definitely needs water for fulling this sticking task. Cement is a binder that hardens by reacting with water. Crushed limestone is ground and powdered with the addition of clay and if necessary, iron ore and/or sand. This ingredient kilned in rotary furnaces at 1400-1500°C.  The arising product is called “clinker”.Then, an amount of gypsum(around 4-5%) is added to clinker and Portland Cement is obtained by powderizing it. In admixture cement production, apart from clinker and gypsum;  one or more of trass, blast furnace slag, fly ash, silica fume etc. are added according to the cement type. Cement is the component that has the lowest volume in many concrete mixtures, however, it is the most important one among concrete ingredients.

The most commonly used cement types are Portland Composite Cement, Admixture Cement, Slag Cement, and Sulphate-Resistant Cement. Apart from these, White Portland Cement and some other cement types are also used with specific purposes.

Becayse aggregate oartşckes are the strongest agents in normal concrete, other two agents(cement paste and adherence) determines the strength. Strength of the cement paste is determined by water/cement ratio to a large extent.

Cement types used in concrete and their conformity evaluation have been standardized in TS EN 197 series.

Cement :

Part 1: Cements in general, composition, features and conformity criteria ;

Part 2: Uygunluk değerlendirmesi.

After TS EN 197-1 standard was established, all of old standards were abolished apart from there cement standard with specific purposes.  These three standards are the standards for TS 21 White Portland Cement, TS 22 Mortar Cement and TS 10157 Sulphate-Resistant Cement. The new standard includes the eqyşvakebts ıf general purpose cements that were abolished(Table 1).

New TS EN 197-1 standard ensures that more cement types than the cement types currently used in concrete production in our coutry can be used.

CEMENT TYPES

Marking of cements:

TS EN 197-1 marks cements in five main types from CEM I (Portland Cement) to CEM V(composite cement). Marking include main cement type, Portland cement clinker ratio; secon main component; standard(e.g. 28 days) strength class and early strength attainment rate.

For example; a Portland Slag Cement type is shown as follows:

CEM II/A-S 42,5 N

Subclass  “N” indicates normal early strength, “R” indicates high early strength.

Standard strength classes

Subtype shows the second main component(blast furnace slag in this example).

Portland cement clinker ratio is shows as (A) high, (B) medium and (C) low.

Main cement type

Cement Components

According to the different cement types stated in both Table 1 and TS EN 197-1, cement components are as follows:

– Main component, e.g. Portland cement clinker;

– Second main component, e.g. fly ash, blast furnace slag, limestone, silica fume;

– Minor admixture component, e.g. fly ash, blast furnace slag, limestone, natural puzzolan;

– Setting regulator, e.g. calcium sulphate;

– Chemical admixtures, e.g. pigments, air entraining admixtures.

Letters indicating second main components are as follows :

S – blast furnace slag;

D – silica fume;

P – natural puzzolan;

Q – natural calcined puzzolan;

V – siliceous fly ash;

W – calcerous fly ash;

T – kilned schist;

M- two or more of the above-mentioned.

Table 1: Cement Types According to TS EN 197-1 :