Granulated blastfurnace slag cement

Madrid, J. et al. (1997) Durability of ordinary Portland cement and ground granulated blastfurnace slag cement in acid medium, ia Proceedings 10th ICCC, Gdteborg, paper 4iv040. 

Major Portland cement clinker Granulated blastfurnace slag Natural pozzolanas Thermally activated clays and shales Siliceous fly ash Calcareous fly ash Unslaked calcareous fly ash Burnt shale Limestone Limes... 

First of all the C/S molar ratio changes depending on the saturation of the liquid phase in concrete, in relation to Ca(OH)2 (Fig. 3.17). Especially in the case of cements with mineral additions, particularly siliceous fly ash or ground granulated blastfurnace slag, this ratio decreases and the sections of chains composed of [SiO ] " tetrahedra become longer [32]. 

The shrinkage of mortars produced from different cements increases with then-strength class (higher fineness) but decreases in the case of cements with mineral additions, particularly at high granulated blastfurnace slag and siliceous fly ash content. 

The granulated blastfurnace slag and siliceous fly ash addition will have a similar effect on the ability of chloride ions binding in cement pastes, because they will also decrease the C/S ratio in C-S-H gel. Uchikawa and Okamura [210] report the following C/S ratio 1.7 for Portland cement, 1.6 in case of 40% slag addition and 1.2 at 40% of sihceous fly ash addition. Simultaneously, these additions will cause the aluminates content decrease in favor of calcium silicate hydrates. 

As aforementioned, the efflorescence is not harmful for the durability of concrete. When the mechanism involved in efflorescence formation is known, the remedies of effective preventing its occurrence are also possible. For example cements with mineral additions can be used in the production of concrete elements. Silica fume has particularly beneficial effect, which prevents efflorescence already from 5 % addition. The groimd granulated blastfurnace slag or siliceous fly ash are good additives too. The latter one should be groimd when added to concrete or taken from the last section of electrical precipitator, where the finest fractions are collected. 

The importance of supersulphated cements decrease during the last fifty years and their production on a large scale was abandoned. In some countries, for example in France, a significant amount of granulated blastfurnace slag with low lime addition is used in road construction [89]. For example in 1974 almost a half of annual blastfurnace slag output was used for this purpose [90]. 

The three component cements with fly ash addition, apart from granulated blastfurnace slag CEM II/B-(S-V), have the advantageous properties first of all fairly good strength development. 

The other fine powder components, added to control the workability of concrete mixture are fly ash, limestone flour and ground granulated blastfurnace slag. The content of these mineral additions can be substantially high when cement type CEM 1 is used they substitute up to 50% cement, particularly that of class 42.5. One can conclude that the Portland cements with mineral additions can be also applied. The effect of limestone flour on the properties of concrete mixture was studied, among the others, by Gizeszczyk [32],... 

Partial replacement of Portland cement by natural or artificial pozzolans reduces the heat of hydration and also the unit price of concrete it slows down the process of hardening and the early strength is lower. Nevertheless, the majority of the volume of structural concrete used in technically advanced regions of the world are based on rational compositions of Portland cement and so called secondary binding materials fly ash, ground granulated blastfurnace slag, metakaolin, SF, and others. 

Slag Cement. A mixture of granulated blast-furnace slag and lime, together with an accelerator (q.v.) very little is now made (cf. Portland blastfurnace cement). 

---