Portland blast furnace slag cement

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. 

Blast-furnace slag cements with high slag contents have lower heats of hydration than pure Portland cement, which is advantageous for large scale concrete structures (e.g. dams). The lower calcium hydroxide content results in their being somewhat more chemically stable than Portland cement. Blast-furnace slag cements are used in similar applications to Portland cement. 

The rate of reaction of blast furnace slag and fly ash differs strongly To show this. Figure 1.8 compares electrical resistivity measurements of wet cured concrete with a water/cement ratio of 0.45 made with Portland, Portland fly ash and blast furnace slag cements. The development of resistivity of concrete at an early age... 

Table 2.3 Resistivity [Cl m) of concrete made with Portland cement (OPC), blast furnace slag cement (GGBS), and Portland cement with addition of 5% silica fume (SF) iv/c = 0.45. lues were determined after 1.5—2.5 y exposure in a fog room or 20°C 80% R.H. climate [37]...

CO2 (molecular weight 44) that can react with a concrete produced with 300 kg/m Portland cement that we can suppose is composed by 64% of CaO (molecular weight 56) is 300 X 0.64 X 44/56 150 kg/m. In the case of blast furnace slag cement with 70 % of GGBS, the percentage of CaO is only 44%. For other blended cements, the quantity of CaO is somewhere between these two values [3]. For blended cement, hydration of pozzolanic materials or GGBS also leads to a lower Ca(OH)2 content in the hardened cement paste which may increase the carbonation... 

Table 12.5 Initiation time for chloride-induced corrosion estimated for different concrete cover thicknesses, utilising apparent diffusion coefficients of chlorides (D,pp) evaluated on specimens submerged in the North Sea for 16 y (concrete of 420 kg/m of Portland cement, OPC, or blast furnace slag cement with 70% GGBS and identical curing procedures) [18]...

With a few of the products that complied with all requirements described above, further investigations were carried out [23,24]. The conclusions apply to concrete of reasonable quality (wjc = 0.50) made with Portland or blast furnace slag cement, which was thought to be representative for the upper parts of bridge decks. They can be summarised as follows ... 

Dining manufacturing of cement-based pipeline products, the silicates and alumi-nates present in the cement react with water to form products of hydration and, in time, these set to a hard mass. The various solid phases formed come into thermodynamic equilibrium with the interstitial water (pore water), which is rich in calcium, sodium, and potassium hydroxide phases. The presence of these hydroxides raises the pH of the pore water solution to about 13 or 13.5. Table 4.15 gives typical compositions of pore solution for two types of cement Portland and blast furnace slag cement. 

As to the phase transformations, in blast furnace slag cement pastes increasing amounts of melilite [a sohd solution of gehlenite (C2AS) and akermanite (C2MS2)] are formed as the amount of slag in the original cement increases, at the expense of yff-dicalcium silicate, which is formed in Portland cement pastes under similar conditions. In pastes made from cements that contain distinct amoimts of fly ash, yff-dicalcium silicate is also the main final decomposition product. In parallel, quartz, which is a common constituent of fly... 

Figure 23.2 Content of bound water in cement pastes made with different cements and exposed to different temperatures. OPC, ordinary Portland cement BFSC, blast furnace slag cement with 50% of granulated blast furnace slag PFA, fly ash cement with 25% of pulverised fly ash Trass=trass cement with 25% of trass SF=Portland cement with 10% of added sihca fume.

Portland cement blast-furnace slag cement 500 500 349 400 382 382... 

The European Standard ENV 197/1 distinguishes five types of cements Portland cement (t3qje I), Portland cement with additives (type II), blast furnace slag cement... 

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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