INSIDE THE DOT
South Dakota Department of Transportation
Identification & Elimination of Alkali Carbonate Damage
Dave Huft, SDDOT
A recently completed research project SD92-04 "Alkali-Silica Reactivity of Fine Aggregates in South Dakota" addressed the problem of Alkali-Silica Reactive (ASR) fine aggregates for use in Portland Cement Concrete. This research involved physical and chemical testing of selected sand sources and attempted to correlate test results with actual field performance but did not examine potential ASR of coarse aggregates in detail. In addition the research did not investigate the possibility of another mechanism-Alkali-Carbonate Reaction (ACR)-causing concrete deterioration in pavements and structures in eastern South Dakota. Additional physical testing of both fine and coarse aggregates to screen for ACR and ASR reactivity is necessary but the Department lacks the expertise to characterize the mineralogical properties of these aggregates and substantiate whether ACR is actually occurring in South Dakota. There is a need to delineate the extent of potential concrete durability problems and to understand the composition of concrete aggregates in relation to the ultimate durability of the concretes they are used in. In addition the economic impact of using reactive aggregates as well as the potential for minimizing reactivity using fly ash or other admixtures must be evaluated.
1 To determine the extent of alkali-carbonate reactivity occurring in South Dakota.
2 To characterize the mineralogy of coarse and fine concrete aggregates in South Dakota.
3 To evaluate the alkali-aggregate reactivity potential of concrete aggregates in South Dakota.
4 To relate mineralogy and geological history of various aggregate sources to potential for alkali-aggregate reactions.
5 To analyze the costs and benefits of using reactive aggregates in concrete structures and pavements.
6 To develop recommendations for policies and procedures regarding coarse and fine aggregate sources in the state.
1 Meet with the technical panel to review the work plan for the research.
2 Review available literature on mineralogy of alkali-aggregate reactive aggregates and their characterization.
3 Conduct field evaluations of pavements and structures with potential alkali-carbonate reactivity.
4 Perform X-ray diffraction and petrographic analyses of concrete cores and laboratory samples to determine the extent and severity of alkali-carbonate reactivity.
5 Determine the mineralogical composition of coarse and fine aggregates being used in concrete.
6 Perform physical tests (ASTM C1105, Canadian Prism test) on concrete specimens to determine the potential or expansion due to alkali-carbonate reactivity.
7 Screen coarse aggregates for potential ASR using ASTM P214.
8 Correlate geological sources and history with mineralogical data and potential alkali-aggregate reactivity to categorize aggregates.
9 To conduct appropriate tests of alkali-carbonate reactive aggregates with fly ash or other admixtures to determine the feasibility of reducing potential ACR.
10 Provide an analysis of the costs involved in using reactive aggregates in concrete.
11 Develop recommendations and propose specifications based on the research results.
12 Submit a final report summarizing relevant literature research methodology, findings and conclusions.
13 Make an executive presentation to the SDDOT Research Review Board at the conclusion of the project.
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