Improving PCC Mix Consistency and Production by Mixing Improvements (TR-505, Proj. 11)
Researcher(s)
Principal investigator: Vern Schaefer, 515-294-9540, vern@iastate.edu (project list)
Co-principal investigators:
- Scott Schlorholtz, 515-294-8761, sschlor@iastate.edu (project list)
- Kejin Wang, 515-294-2152, kejinw@iastate.edu (project list)
Other authors: Tyson D. Rupnow, Vernon R. Schaefer, Kejin Wang, Benjamin L Hermanson
Student researcher: Benjamin Hermanson
Project status
Completed
Start date: 10/01/03
End date: 09/30/05
Publications
Report: September 2007, Improving Portland Cement Concrete Mix Consistency and Production Rate through Two-Stage Mixing 4.5 mb (*pdf)
Related publications: Two-Stage Mixing 156 kb *pdf (Tech transfer summary) February 2008
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Sponsor(s)/partner(s)
Sponsor(s):Federal Highway Administration
Iowa Highway Research Board
PCC Center Sponsored Research Fund
About the research
Abstract: A two-stage mixing process for concrete involves mixing a slurry of cementitious materials and water, then adding the slurry to coarse and fine aggregate to form concrete. Some research has indicated that this process might facilitate dispersion of cementitious materials and improve cement hydration, the characteristics of the interfacial transition zone (ITZ) between aggregate and paste, and concrete homogeneity.
The goal of the study was to find optimal mixing procedures for production of a homogeneous and workable mixture and quality concrete using a two-stage mixing operation. The specific objectives of the study are as follows: (1) To achieve optimal mixing energy and time for a homogeneous cementitious material, (2) To characterize the homogeneity and flow property of the pastes, (3) To investigate effective methods for coating aggregate particles with cement slurry, (4) To study the effect of the two-stage mixing procedure on concrete properties, (5) To obtain the improved production rates. Parameters measured for Phase I included: heat of hydration, maturity, and rheology tests were performed on the fresh paste samples, and compressive strength, degree of hydration, and scanning electron microscope (SEM) imaging tests were conducted on the cured specimens. For Phases II and III tests included slump and air content on fresh concrete and compressive and tensile strengths, rapid air void analysis, and rapid chloride permeability on hardened concrete.