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Field investigation of pumping air entrained concrete and validation of the SAM test on lightweight aggregate concrete mixtures

Staffileno, Chad Jordan
The use of a pump to transport concrete is one of the most common and widely accepted methods to distribute and place concrete. An air-entraining admixture can be added to fresh concrete to prevent freeze-thaw durability issues from occurring. Unfortunately, the air volume and bubble quality of air-entrained concrete is problematic when pumped. In some situations, concrete can lose up to half of its air volume after being pumped in comparison to the concrete discharged out of the mixing truck. This work focuses on investigating the air volume and SAM Number with pumped concrete mixtures and on non-pumped mixtures with fine LWA's. The key findings show that after pumping the fresh properties of air entrained concrete yield decreased air contents and increased SAM Numbers however, when compared to the hardened properties, the samples show that air volume recovered and the spacing factor of the bubbles were not impacted. In addition, air entrained concrete with fine LWA shows a small impact on air content and SAM Number when certain LWA' s prewetted prior to mixing. However, not all aggregates were applicable to the SAM Test. A test method is presented to determine if a LWA is applicable.