Concrete Strength

Water-Reducing Agents and Superplasticizers. Common admixtures that improve fluidity of concrete mixes are often used in high strength concrete. These admixtures make possible the incorporation of siUca fume while maintaining necessary workabiUty. Three principal types of... 

A considerable range of different toppings is available for heavy-duty service. The correct selection of the most appropriate topping on a cost/performance basis can only be made if service conditions are very clearly defined. In general, heavy-duty toppings require a sound (preferably 35N/mm strength) concrete substrate. 

Silica powder has been studied as a stabilizer for oil well cement at high temperatures [1895]. Tests indicated that silica powder can improve the stability and pressure resistance strength of cement. The manufacture of very-high-strength concrete (after 28 days the compressive strength is greater than... 

F. De Larrard. Ultrafine particles for the making of very high strength concretes. Cement Concrete Res, 19(2) 161-172, March 1989. 

Fig. 7.9 High-strength concrete through the use of silica fume and a high-range water-reducing admixture...

Table 7.7 High-strength concrete produced by a hydoxycarboxylic acid water-reducing agent...

The Hibernia offshore concrete platform on the Grand Banks off the coast of Newfoundland, Canada, is a 111 m structure and required about 165 000 m of superplaticized high-strength concrete. The typical mixture proportions and the properties of the concrete used for the skirt elements of the structure are shown in Table 7.18 [70]. The precast skirts are a series of reinforced concrete elements which were joined together to form continuous walls to support the base slab of the structure [69]. 

Concretes containing VEAs have consistencies that are structured while static but become highly flowable, with self-leveling characteristics, when work is imparted to it. Data presented in Fig. 7.28 show that medium-strength concretes with equal slumps perform very differently in the washout test. This indicates that the slump test does not correlate to washout... 

Fig. 7.28 Medium-strength concretes with equal slump perform differently in washout tests (Rakitsky [78]).

For normal-strength concrete, a larger maximum-size aggregate (MSA) reduces cement consumption. 

Gawin, D., Pesavento, F. and Schrefler, B.A. Modelling of deformations of high strength concrete at elevated temperatures, submitted for publication... 

Concretes that were previously (late 1970s) known as high-strength concretes are now referred to as high-performance concretes. This is because high-strength concrete embodies enhanced performance in other areas such as durability and abrasion resistance. Superplasticizers are essential ingredients in such concretes... 

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