Verification that Type V Cement is required for CLSM with high sulfate native soils
Project ID: 2840
Principal Investigator: Janet White
Research Topic: Improving Geotechnical Infrastructure Reliability
Funded Fiscal Years: 2013, 2014 and 2015
Keywords: clsm, flow fill, soil slurry, native soils, type v cement, sulfates
Is there a benefit to using Type V cement with Controlled Low-Strength Material (CLSM) made with high sulfate native soils? Will the sulfates in the native soils deteriorate the CLSM over time?
Need and Benefit
CLSM, also known as cement slurry or flow fill, is used under hundreds of thousands of miles of Reclamation pipelines and also used as backfill material along structures. Current specifications require that CLSM made with soils high in sulfate use a Type V (sulfate resistant) cement to mitigate against sulfate attack. Sulfate attack is known to deteriorate concrete when the sulfates in the soil react with the hydrated cement. There is a little or no research on whether or not sulfate attack can occur in low strength CLSM type mixtures and if Type V cement is an appropriate means to mitigate this deterioration. Type V cement is more costly than regular Type II cement, because, Type V cement requires a more expensive raw material mix and more energy to create the <5% C3A clinker.
CLSM is used extensively throughout Reclamation and will be again used on over 100 of miles of pipeline for the upcoming Navajo Gallup Water Supply Project. There is an economic and environmental benefit of using native soils in CLSM rather than the traditional ASTM C33 aggregates. Aggregates make up approximately 75% of the volume of CLSM and using the native soils from the excavation instead of manufacturing and transporting aggregates can be not only a tremendous cost savings but a reduction in carbon production in the environment as well. The TSC would like to perform this research project in order to verify that CLSM produced with native soils will not break down overtime due to sulfate content.
Typically, when concrete needs high sulfate resistance Type V cement is specified along with a minimum water/cementitious ratio. Since CLSM is mixed with the high sulfate soils and placed at a much higher water to cementitious ratio there may not be a benefit in using Type V cement and the extra expense of the specialty cement may not be needed.
The results of this study would not only benefit the Navajo- Gallup project but also have a Reclamation wide benefit as well. Navajo-Gallup would be a partner in this project with supplying native soils from different portions of the project.
The final product will be a complete report including, project summary, scope of work, materials used, mixture proportions used, test methods used, data, and conclusions. The report will be checked, and peer reviewed. A copy of the report will go to all partners on the project including Navajo-Gallup. A white paper may be submitted to a professional publication if the results are conclusive.