International Concrete Abstracts Portal

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.

The Federal Highway Administration (FHWA) under its Testing and Evaluation program (TE-30) on High-Performance Concrete (HPC) pavements had initiated several field demonstration projects to evaluate the use of new technology to improve the long-term performance of the pavements. Under this program, the Minnesota Department of Transportation (Mn/DOT) has successfully completed the construction of the first 60-year design life HPC pavement in the state along Interstate I-35W. Significant changes to materials-related specifications that affect the long-term performance of the concrete pavement were implemented in this project. This paper will provide a brief description of the Mn/DOT’s first HPC pavement project along with key design features of the pavement, including use of slag cement in high-performance concrete mixtures, higher level of entrained air content than that is conventionally used, and stainless steel dowel bars. Also, the results of quality control tests conducted on field concrete during construction are presented.

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.

This paper is a collection of over 30 brief case studies about mass-concrete projects using ASTM C989 (AASHTO M302), or similar, slag cement (formerly called ground granulated blast-furnace slag) - undertaken to learn more about concrete mixtures and considerations as they are applied in the field. With the exception of some ternary mixes, generally, the slag cement amounts equaled or exceeded the amounts of Portland cement employed in the mixtures. The information showed that a broad spectrum of proportions featuring slag cement of all grades have been used to achieve desired mass-concrete properties and outcome, including staying under a maximum core temperature, holding within a maximum differential temperature, and achieving specified strength.

This report details the results of a critical review of the literature on the effect of ground, granulated, blast-furnace slag (slag cement) and slag-blended cements on the drying shrinkage of concrete. Drying shrinkage values from the literature were collected, and concretes containing slag were compared to otherwise identical concretes that did not contain slag. Overall, while individual data may indicate a higher drying shrinkage, on average, the drying shrinkage for concretes containing slag cement was the same as concretes without slag. From examination of the data it was determined that the only parameter of the mixture design that had a significant influence on the drying shrinkage was the total aggregate volume. Any increase in drying shrinkage of the slag cement concrete was typically reduced with increasing aggregate content. The level of slag replacement and the w/cm of the concrete mixture were not found to affect the relative drying shrinkage, at least over the typical range used for concrete mix designs. The relative values of the drying shrinkage were also unaffected by whether slag cement was added as a separate ingredient or if a blended hydraulic cement containing slag was used. The aggregate content of concretes made with slag was often lower than a comparable concrete made without slag due to the lower density of the slag relative to portland cement when slag cement was used as a replacement on an equal mass basis, rather than on an equal volume basis. A correction for this would reduce any additional shrinkage attributable to the use of slag cement. In addition, the increase in relative shrinkage of some slag-containing concretes may, in several cases, also be partially due to the reduced gypsum content of the cementitious mixture, although this is unclear and needs further investigation. Although the data are limited, the restrained shrinkage cracking of concrete containing slag appears to be less than that of concrete without slag. Cracking was delayed to later ages and resulted in smaller total crack widths. The effect of the inclusion of slag on restrained cracking needs to be further investigated.