Mineral Additions for Cement Production

The following classification of cement mineral additions is commonly accepted  

This classification is based upon the chemistry of hardening process, however, some reservations, as it will be fiuther mentioned, shonld be pointed ont. 

Granulated blastfurnace slag can hydrate without activation too [2]. The calcinm hydroxide necessary to activate the reaction of slag glass is probably formed as a result of calcium sulphide hydrolysis  

Finally, the so-called fillers constitute the last group of additives, which are, as a rule, inert and do not react in cement paste. The hmestone, added on a laige scale in Italy and in France was classified to this group a time ago [3]. As it is commonly known, the hmestone cannot be considered as an inert concrete component however, as compared with mineral additions from the former two groups, degree of CaCOj reaction in cement paste is rather poor. Nowadays, however, hmestones are recommended in the EN 197-1 standard as mineral additions, together with pozzolanic additives (see types of cements. Table 1.3). In 2007 the ratio of limestone cements produced in Europe and Turkey was 21.4 % (members of Cembureau) this corresponded to the annual output on the level of 56.2 million tons, in majority class 42.5. The ground quartz sand can be considered as typical filler, which does not react practically with calcium ions in cement paste, at ambient temperature. 

The pyroclastic rocks, in the form of loosen deposits or consolidated formations, produced as a result of diagenetic cementations belong to the first group. They originate from the emption of magma and include sands, volcanic ash and fragments of rocks, carried away from the crater of volcano. The loosen deposit rocks from Naples and Rome, the Santorin earth from the Santorin Island, as well as the corrsolidated rocks the Rhine, Naples and Bavarian tuffs, so-called trass, are among the most commonly known. 

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Red mud is a very complex material. It is a mixture of several oxides and minerals such as hematite, sodium aluminum silicates, and rutile. These make the mud a potential raw material for the production of additives for cements. 

V. B. Kvashenkin. Plugging solution for cementing low pressure oil and gas wells—contains plugging Portland cement, waste of silicon production as the lightening additive and calcium chloride as mineral salt, and water. Patent SU 1832149-A, 1993. 

Preparation for X-ray diffraction studies requires micronising with minimal (preferably zero) introduction of stress to the mineral structures. For soil samples, pre-treatment to remove organic matter, soluble salts or mineral cements may be required (Buhrke etal. 1998). Productivity is typically lower than that of other milling procedures because these mills are designed to comminute only one or two samples per cycle. In addition, considerable amount of cleaning time between samples is needed to prevent cross-contamination in these small capacity mills. 

From Eq. (1) it is clear that the penetration depth x for a certain content Q depends on the product D pp t. Consequently, other factors being constant, reducing the apparent diffusion coefficient by a factor of 10 increases the initiation time by a factor of 10. Advantages of using mineral additives to obtain so-called blended cements in the design of durable structure will be illustrated in Section 12.6.1. 

In the European standards, above all inEN 197-1, another principle was adopted, dividing cement on kinds according to the quantity and kind of mineral additions. However, the division on class is common, independently of cement kind. These rules of division facilitate the classification of cements for concrete production, designated for constractions exploiting in different expositions. 

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. 

Soils and clays, in general, when calcined give off adsorbed, interlayer, and hydrated types of water. These effects produce endothermal peaks or loss of weight in DTA and TG, respectively. The endothermal peaks are followed by exothermal peaks that are caused by re-crystalliza-tion. Although many types of clay minerals such as montmorillonite, illite, and some shales show these effects, they are not suitable as pozzolans in concrete. Metakaolin, formed by heating kaolinite, seems to be the most suitable additive material for cement. Heating of kaolinite involves removal of adsorbed water at about 100°C and dehydroxylation at above 600°C, followed by the formation of metakaolinite, an almost amorphous product. The sequence of reactions is as follows ... 

EINECS is a closed list containing 100,106 entries and counts for about 99% of the chemicals volume on the market. EINECS include chemical substances produced from natural products by chemical modifications or purification, such as metals, minerals, cement, refined oil, and gas substances produced from animals and plants active substances of pesticides, medicaments, fertilizers, and cosmetic products food additives a few natural polymers and some waste and by-products. They can be mixtures of different chemicals occurring namrally or as an unintentional result of the production process. 

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