Ciment fondue

API Class G cement API Class H cement Chem Comp cement Ciment Fondu Lumnile cement HLC... 

An alternative to silicate-based Portland cement is the calcium aluminate cement, ciment fondu, which originated with the Lafarge company in France in 1908. Ciment fondu is typically made by heating limestone with bauxite, which is mainly AIO(OH) but contains much iron oxide (see Section 17.2). As noted above, calcium aluminate hydrates and hardens much more rapidly than alite, and so ciment fondu, either as such or mixed with Portland cement, can be used whenever a rapidly setting cement is required, for example, for construction at low temperatures. Concretes made from aluminate cements remain serviceable at higher temperatures than Portland cements and so are used to make cast refractories for pyrometal-lurgical applications. 

Ciment Fondu is normally made by complete fusion of limestone and bauxite at 1450-1600 C. In order to produce a cement with the desired rapid-hardening properties, both raw materials must be low in SiO,. The molten clinker is tapped off continuously from the furnace, solidifies and is typically crushed and ground to a fineness of about. 00 m- kg . Some iron is reduced to Fe . The colour of cements produced from bauxite can vary from yellow brown to black, but is commonly greyish black. White calcium aluminate cements are usually made by sintering calcined alumina with quicklime (calcium oxide) or high-purity limestone. 

In Ciment Fondu, the ferrite phase seems to play no significant part in early hydration at 20 C, but at 30-38 C over 80% was found to have reacted by 2 months (C47). The melilite and pleochroite seem to be unreactive. When belite is present, silicate ions can be detected in the solution within a few minutes, but then disappear it seems that precipitation occurs and further dissolution is inhibited. Among the minor oxide components. TiO, and MgO mainly occur in the unreactive phases. Na,0 and K,0 scarcely affect the solution equilibria at early ages, as their concentrations are very low (M88). 

Fig. 10.1 Major hydration products and typical setting limes for neat pastes and concretes of Ciment Fondu cured at various temperatures. George (G73).

Fig. 10.2 shows the changes in the solution composition that occur when a typical Ciment Fondu reacts with water at 20°C, together with the metastable solubility curves for phases in the CaO-Al20,-H20 system. The CaO and AI2O3 concentrations increase, at an approximately constant CaO/ AI2O3 ratio somewhat greater than 1 in the experiment shown, C -ao reached 15 mmol 1 in 3 min and its maximum value of 21 mmol 1 in 1 h. 

Fig. 10.2 The CaO-AljOj-HjO system at 20°C, showing calculated solubility curves and typieal path (broken and dotted lines) followed by the composition of the solution obtained on reaction of Ciment Fondu with water in a suspension with w/s = 10. AHj = poorly crystalline hydrous alumina CA, = superficially hydroxy-latcd CA (see text). Capmas (C51) and Menetrier-Sorrentino (M88).

Fig. 10.3 SEM secondary electron image of Ciment Fondu hydrated for a few minutes in a suspension of w/c = 10 at room temperature, showing foils, probably of C,AH j. and amorphous material. Mcnctricr-Sorrentino (M88).

Fig. 10.5 shows portions of fracture surfaces of some pastes of Ciment Fondu examined by secondary electron imaging in the SEM. At 22 h. in pastes hydrated at 20 C, fibrous material is abundant, together with plates of CjAHg. The fibrous material is probably partially dehydrated CAH,(,. 

Cottin (C50) earlier studied pastes of Ciment Fondu, largely by the TEM replica method. The microstructures of pastes of low w/c ratios hydrated for 7 days at 12°C were too compact to show more than occasional detail, but with pastes of w/c = 0,7 much detail could be observed in cavities exposed by fracture, which were lined with small crystals of CAH,o and sometimes contained plates of C,AHg. The crystals of CAH[q, which were hexagonal prisms up to 1 pm long and 0.2 pm wide, were present in rounded aggregates. Hydrous alumina was seen in a paste of w/c = 1.0 hydrated at 30"C it occurred in the lining of a cavity, mainly as rounded masses of randomly oriented platelets. 

Fig. 10.5 SEM secondary electron images of the fracture surface of a paste of Ciment Fondu (w/c = 0.4), hydrated for 22 h at room temperature, showing (A) CAH,o, and (B) plates of CjAHg. Menetrier-Sorrentino (M88).

Fig. 10.6 Compressive strengths and observed and calculated porosities for pastes of Ciment Fondu of varying w/c ratios. The unconverted paste, which contained CAH o, was cured for 7 days at 10 C. The converted paste, which contained CjAH and AHj, was cured for 7 days at 70°C. After George (G73).

Other types of admixtures used with calcium aluminate cements include water reducers and superplasticizers (Section 11.4), which also act as retarders, and thickening agents, such as carboxymethylcellulose. Complex formulations may be used for special purposes for example, a ready-mix mortar for high-performance road repair might contain 55% Ciment Fondu and 45% sand, with glass fibre, aluminium powder, Li2C03, sodium gluconate and methyl ethyl cellulose (M93). 

Fig. 10.8 Setting times of neat pastes of mixtures of Ciment Fondu and Portland cement. These are only general indications, as the times depend on Portland cement composition, mixing time, temperature and other factors. After Robson (R47).

This classification has a long tradition and reflects rather the problems to be resolved by the specialists in the field of cement chemistry, with aim to improve the durability of concrete in the more fiequently occurring aggressive enviromnents. The sulphate corrosion is here a typical, common example, which led to the invention of calcium aluminate cement by Bied (ciment fondu). The deterioration of concrete by de-icers, used in millions tons (for example in the USA in winter 1966/1967 6.3 milliont [62]), became a serious problem. The cost of bridges repairs in USA in 1975 was 200 million [63]. 

The development of calcium aluminate cement was spurred by efforts to overcome the problems associated with sulfate attack on Portland cement based concrete used in the construction of railway tunnels in gypsiferous grounds. The first patent relating to this type of binder was filed in 1908 by Bied in France. The cement was introdueed into production in 1913, and became known as Ciment Fondu. After it was recognized that calcium aluminate cement gains strength much faster than Portland cement, the binder was used in World War I by the French military in the constraction of gun emplacements and shelters, where this property was of paramount importance. After the war, the cement became widely used in other structural applications however, its use in this area became limited, after failures of structures built with this cement were reported from different countries. Nowadays calcium aluminate cement is being used in a variety of special applications. 

Trade name Ciment Fondu Secar 50 Secar 70 Secar 80... 

Banfill, P.F.G., and Gill, S.M. (1993) Superplasticizers for ciment fondu effect on rheological properties of fresh paste and mortar. Advances in Cement Research 5,131-138. 

Majumdar, A.J., Singh, B., and Edmonds, R.N. (1990) Hydration of mixtures of ciment fondue aluminous cement and granulated blast furnace slag. Cement and Concrete... 

Of the non-Portland cements used in building, the most important is high-alumina cement (Ciment Fondu). 

Alumino-silicate Refractory. A general term that includes all refractories of the fireclay, sillimanite, mullite, diaspore and bauxite types. BS 1902 Pt 2 defines it as a refractory containing 8 to 45% AI2O3, the balance being predominantly silica. Aluminous Cement. See ciment fondu. Aluminous Fireclay Refractory. This type of refractory material is defined in B.S. 1902 Pt 2 as a refractory containing in the fired state, > 45% AI2O3, the balance being predominantly silica. Alundum. Trade-name Fused alumina made by Norton Co. 

CIMENT FONDU HIGH EARLY-STRENGTH cement HYDRAULIC CEMENT KEENE S cement PORTLAND CEMENT RAPIDHARDENING PORTLAND cement REFRACTORY CEMENT, SILICATE... 

Cinpres. Gas assisted injection moulding, a plastics manufacturing technique. Ciment Fondu. Trade-name aluminous hydraulic cement. (Lafarge Aluminous Cement Co. Ltd, 73 Brook St., London, Wl) For general properties of this type of cement see high-alumina cement. See also gorkal cement. 

---