The experimental program presented in this paper was a technical evaluation of an alternative cement and high-density (HD) concrete mixture design for HD concrete at mid-range temperature to meet specific target properties. The cement industry has moved away from manufacturing ‘special use’ portland cements, which were approved for some applications of mass HD concrete, for which temperature rise in the concrete is of importance. Potential replacement of these ‘special use’ portland cements by blending varying amounts of supplementary cementitious materials (SCMs) with ‘general use’ portland cement to provide ‘blended cements’ was investigated. The paper focuses on experimental results obtained in the laboratory showing the effect of the addition of high volume slag blended cement for HD concrete on temperature rise, as well as on mechanical properties and microstructure after aging and mid-range temperature exposure. Slag-blended cement was evaluated and determined to have acceptable properties in HD concrete, meeting or exceeding performance requirements.

This CD-ROM contains eight papers that provide insight on recent slag cement concrete developments in academia, the concrete industry, and in real life applications of slag cement concrete. Topics include materials aspects related to the benefits of adding slag in concrete to prevent alkali-silica reactions, reducing drying shrinkage, and reducing the potential for thermal cracking during the curing period. Also covered are high-volume applications of slag cement in: concrete for transportation structures, high-performance concrete pavements, mass concrete, and high-density concrete. Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-263

To investigate the relationship between the alkali content of concrete and the expansion caused by alkali-silica reaction, several hundred concrete prisms containing reactive natural aggregate, were regularly measured over a period of ten years. These prisms contained between 0 and 70% slag cement in combination with portland cements, and had concrete alkali contents between 4.5 and 11 kg/m3 (0.3 and 0.7 lb/ft3). The alkali content of the Portland cements ranged from 0.54 to 1.15% and that of the slag cements from 0.58 to 0.83%. Prisms were moist-stored at 20°C (68 °F) and at 38°C (100°F). Storage at the higher temperature accelerated the rate of expansion, and slightly increased the ultimate expansion. The correlation between the two temperatures was very good in terms of classifying mixtures as either ‘expanding’ or ‘non-expanding’. It is concluded that storage at 38°C (100°F) is an accelerated test that can be used to reliably predict what would happen at ‘normal’ temperature. The mixtures containing slag cement, tolerated much greater alkali contents in the concrete, without expansion. This effect was more pronounced for higher proportions of slag cement.

Slag cement was introduced to Virginia Department of Transportation (VDOT) in the early 1980s. Laboratory investigations showed that slag cements can be used as an alternative to conventional portland cement concretes in replacement rates up to 50% for pavements and bridge structures. Concrete containing slag cement had lower permeability than the conventional portland cement concrete. Since the mid 1980s, slag cement has been successfully used by VDOT in bridge structures and pavements to reduce permeability and improve the durability of concrete. In large footings, slag cement has been used at a replacement rate of 75% to control the temperature rise and to reduce permeability. Currently, slag cement is used in high-performance concretes to obtain high compressive strength and low permeability. Slag cement is also used in ternary blends with portland cement and fly ash or silica fume to lower permeability, improve durability, and obtain the desired early strengths.

Synopsis: Economic and environmental considerations have promoted the use of supplementary cementing materials (SCMs) such as slag cement (SC) and fly ash (FA). Ternary mixtures containing both slag cement and fly ash have gained popularity due to environmental issues and shortages in the supply of cement. However, in the 2003 Arkansas State Highway and Transportation Department (AHTD) Standard Specifications, ternary mixtures were prohibited for use in Portland Cement Concrete Pavement (PCCP). Previous research conducted by the University of Arkansas examined ternary mixtures containing SC and FA and cured at 70°F (21°C). This research program examined the strength gain and time of setting characteristics of ternary mixtures cured at lower temperatures. In the study, SC contents ranged from 0 to 40%, and the FA contents ranged from 0 to 60%. Six different mixtures containing Class C FA and Grade 100 SC were batched and tested at temperatures of 70°F (21°C) and below. The curing temperatures for the study were 40, 50, 60, and 70°F (4, 10, 16, and 21°C). The concrete properties measured were concrete temperature, slump, unit weight, air content, time of setting, and compressive strength.