Recently the SCA attended the American Society of Civil Engineer’s conference on Airfield and Highway Pavement Technology as an exhibitor. The conference featured sessions on pavement innovation in materials and sustainability as well as airfield pavement technology and safety. To help prepare for the conference, the SCA pulled together information on how slag cement has been used in past highway and airport projects and how the sustainable material impacts concrete durability, strength and overall performance.
In highway, airport and paving projects, slag cement can help mitigate thermal stress in mass concrete, Alkali-Silica Reaction (ASR), and help reduce concrete permeability. Due to its more consistent chemical and physical structure from source to source, slag cement also helps produce concrete with more consistent results than other supplementary cementitious materials.
The case studies below highlight the various ways slag cement can positively impact concrete performance in pavements and airports. The documents prepared for the conference are also available below for download.
Download Highway Document Here
Oakland Bay Bridge:
San Francisco, CA
The Eastern span of the bridge was completed in 2014 to provide an earthquake-resistant replacement. Slag cement was used in the concrete mix to help reduce the overall carbon footprint, increase the concrete strength, increase durability, reduce shrinkage, reduce heat of hydration, and to increase ease of placement of the concrete.
Wayne and Oakland County, MI
MDOT specified 30% slag cement for its exceptional characteristics including increased durability, ASR mitigating properties, and its ability to stabilize cement paste to create a more robust environment for the development of air entrainment. The slag cement was utilized as a component in an ASTM C 595 blended cement to best meet the logistics of this very fast tracked project.
The pavement portion of the project used 42,000 tons of portland cement and 20,000 tons of slag cement. Over 30% slag cement was needed to provide mitigation of potential alkali-silica reaction (ASR) as required by the Michigan Department of Transportation (MDOT) concrete specifications.
I-79/I70 South Junction
Washington County, PA
The 50% slag cement mass concrete mixture aided in meeting the thermal control plan for mass concrete placements and allowed discontinuing temperature monitoring of mass concrete elements earlier than expected. The mixture provided and met the specified flow, penetration, segregation resistance, strength, permeability and freeze-thaw durability performance requirements.
The 267 million dollar project consisted of rehabilitating an existing asphalt runway with a concrete overlay. Specifications required a minimum flexural strength of 700psi at 28 days and a concrete mix with low chloride permeability. The Port Authority Materials Division recommended using slag cement because it increases flexural strengths, reduces concrete permeability, and makes the concrete more resistant to alkali-silica reaction (ASR).
St. Pete/Clearwater International Airport
Slag Cement was used in 16,000 cubic yards of apron pavement and contributed to superior strength gain where time was critical to maintain airport operations without service outages. The lighter color of the concrete with slag cement created higher reflectivity which increases viability at the tarmac.
Download Airport Document Here