Portland blast furnace cement

The most commonly produced cement is Portland cement to British Standard BS 12, which represents 90% of the market, which includes products such as rapid hardening and coarse ground cements, and white Portland cement (WPC). Other cements covered by other British Standards include sulfate resisting Portland cement (SRPC), Portland blast furnace cement, high slag blast furnace cement, and Portland PFA cement. 

Blast furnace slag is a by-product of steel manufacture and is formed when molten blastfurnace slag is rapidly cooled [4]. Blast furnace slag s major use is in the production of slag cement, primarily high slag blast furnace cement and Portland blast furnace cement. 

Calcium chloride increases compressive strength of cement pastes especially at earlier times. The most significant effect on compressive strength occurs with portland blast furnace cement and marginally with portland-pozzolan cement. The compressive strength of cement pastes in the presence of 2% CaCl2 improves by about 50,41,11,9, and 8% overthe reference at 6 hours, 1, 3, 7, and 28 days, respectively.P" ]... 

Portland cement is an accelerator for CAC and vice versa. The effect of proportions of each component on setting time is illustrated in Fig. 4. Ternary blends of portland blast-furnace cement and CAC also have an acceleratory effect. 

Cathodic protection can be used to protect steel in concrete (see Chapter 19). There is no fear of damage by H2 evolution due to porosity of the mortar. Local corrosion attack can be observed under extreme conditions due to porosity (water/ cement ratio = 1) and polarization (f/jq = -0.98 V) with portland cement but not with blast furnace cement, corresponding to field IV in Fig. 2-2 [53]. However, such conditions do not occur in practice. 

Pozzolanic and blast furnace cements (or, alternatively, addition of fly ash or GGBS to Portland cement at the mixing plant) may be the most suitable choice for many stmctures that are critical from the durability point of view. In fact, they reduce the rate of development of heat of hydration, they lead to a lower content of alkalis and Ume in the cement paste, and they can produce a denser cement paste. They should be preferred, for instance, for massive structures (to reduce the rate of development of heat of hydration), or in sulfate-contaminated environments (Section 3.3), when there is risk of ASR (Section 3.4), or in chloride-contaminated environments (Section 12.5.1). 

Generally, concrete used for water treatment plant pipes, water tanks, and filters is made using (ordinary) Portland cement, whereas cement-mortar linings can be made of diflerent types of cements, such as Portland cements, blast furnace cement or the non-Portland calcium aluminate cement. Each type of cement has a typical composition. Table 4.14 gives the typical composition of the primary cements used for manufacturing pipe. 

The full experimental procedure is summarized below. This full procedure has been applied only for the first mortar tested (ordinary Portland cement). Results from this first set of experiments have allowed some experimental conditions for further tests with blast furnace cement (BFC) and high alumina cement (HAC) mortars to be deleted (see page 165). 

Portland cements are calcium-silicate based materials, with less than 2 %free lime Blast furnace cements are mixes of about 30 % OPC and 70 % slag. 

Marciano, E. Jr., and Battagin, A.F. (1997) The influence of alkah activator on the early hydration and performance of Portland blast furnace slag cement, in Proceedings 10th ICCC, Goteborg, paper 3iil03. 

Salem, Th.M., El-Didamony, H., and Mohamed, T.A. (1995) Studies on Portland blast furnace slag cement with limestone as a retarder. Indian Journal of Engineering Materials Science 21,32-135. 

Figure 4-10. Two concrete specimens of different resistance from the test chamber after exposure to two test cycles of biogenic sulfuric acid corrosion, where PC is Portland cement (left) and HC is blast furnace cement (right).

The specific electrical resistance of concrete can be measured by the method described in Section 3.5. Its value depends on the water/cement value, the type of cement (blast furnace, portland cement), the cement content, additives (flue ash), additional materials (polymers), the moisture content, salt content (chloride), the temperature and the age of the concrete. Comparisons are only meaningful for the... 

The manufacture of Portland concrete consists of three basic steps—crushing, burning, and finish grinding. As noted earlier, Portland cement contains about 60% lime, 25% silicates, and 5% alumina with the remainder being iron oxides and gypsum. Most cement plants are located near limestone (CaCOs) quarries since this is the major source of lime. Lime may also come from oyster shells, chalk, and a type of clay called marl. The silicates and alumina are derived from clay, silicon sand, shale, and blast-furnace slag. 

Previous work on superplasticized Portland cement concrete containing fly ash or blast furnace slag has shown that such mixes require 10% less admixture than reference Portland cement concrete to attain the same workability. Therefore, a given dosage may produce higher water reduction. The reason for the reduced admixture requirement has not been determined. It is probably due to the lowering (dilution) of the C3A content... 

Many cements used today are composites of Portland cement and industrial waste materials that can enter into the hydration reactions and contribute to the strength of the hardened product. These substances include pulverized fuel ash (PFA) from burning of pulverized coal in thermal power stations, crushed blast-furnace slag (Section 17.7), and natural or artificial pozzolanas—that is, volcanic ash and similar finely particulate siliceous or aluminosilicate materials that can react with the Ca(OH)2 in Portland cement to form hydrated calcium silicates and aluminates. As noted earlier, the solubility of Ca(OH)2 is such that the pH of pore water in Portland cements will be about 12.7, at which the Si-O-Si or Si-O-Al links in the solid pozzolanas will be attacked slowly by OH- to form discrete silicate and aluminate ions and thence hydrated calcium silicate or aluminate gels. 

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