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.

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.

The early age strength development of concretes containing slag cement (ggbs) at levels of up to 70% of the total binder have been investigated to give guidance for their use in fast track construction. 28-day target mean strength for all concrete specimens was 70 MPa (10,150 psi). Although supplementary cementitious materials such as slag cement (ggbs) are economical, their use has not gained popularity in fast track construction because of their slower strength development at early ages and at standard cube curing temperatures. There are however indications that supplementary cementitious materials are heavily penalised by the standard cube curing regimes. Measurements of temperature rise under adiabatic conditions have shown that high levels of cement replacement by ggbs, e.g. 70% are required to obtain a significant reduction in the peak temperature rise. Even though the temperature rise using slag cement is lower than from using portland cement, it is still sufficient to provide the activation energy needed for a significant reaction acceleration. Maturity measurements are needed to take advantage of the enhanced in-situ early age strength development of ggbs concrete. The contractor should confirm that the actual compressive strength of the concrete in the structure at the time of formwork removal exceeds the required strength. Maturity functions like the one proposed by Freiesleben Hansen and Pedersen (FHP), which is based on the Arrhenius equation, have been examined for their applicability to ggbs concrete. Activation energies, required as input for the FHP equation, have been determined according to ASTM C1074-98.

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.

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.