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Transcript of kp_2009_PCA_v2.ppt
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5/19/2018 kp_2009_PCA_v2.ppt
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Update on PCA R&D 07-10a
Investigating the Effect ofPotassium Acetate on Concrete
Durability
Larry Sutter
Director, Michigan Tech
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5/19/2018 kp_2009_PCA_v2.ppt
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Overview
Work has been performed in the areas:
Literature review
Repeating previous tests
Exploring effects of KAc on silica solubility
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Silica Dissolution Literature Review
Geology/Geochemical
Dissolution of different silicates in the presence of organicacids (carboxylates) were covered
In all cases, dissolution rates and/or solubility increased
with the addition of small amounts of OA (0.10.5 M)
Conditions did not match those found in pore solns but
effect of carboxylate addition were reproducible
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Silica Dissolution Literature Review
Industrial water treatment
Colloidal silica (analogous to reactive aggregate) deposits
commonly foul process cooling water circuits
Several treatment methods for the removal of silica use
carboxylates (formates and acetates) to dissolve silica
Polycarboxylates having one to five acetate groups are very
effective
Increased pH serves to increase solubility even more
Carboxylates increase the solubility limit of silica and also
increases the dissolution rate
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Silica Dissolution Literature Review
Steel slag dissolution
One paper described a novel approach dissolving steelmaking slags in acetic acid to sequestor CO2w/ Ca
dissolved from slag forming CaCO3
Reported complete dissolution in a solution of 33% acetic
acid and 50Cboth Si and Ca dissolved completely
Silica gel stability greater at >70C allowing researchers to
filter silica out thereby making higher grade CaCO3
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Progress to Date
Completed modified ASTM C1260 procedure utilizing
glass beads for reactive aggregate at 4C, 20Cand 38C with similar results to previous work
Although ASTM C1260 tests were reproducible
they do not align with observed distress
Upon review of ASR chemistry, performed literaturereview of silica dissolution which resulted in
modification of experimental approach.
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New Experimental Approach
Focusing on silica dissolution as a primary driver since
the deicing regime appears to provide conditions forgreatly enhanced silica solubility
Performing solubility tests based upon ASTM C289 - 07
Standard Test Method for Potential Alkali-Silica
Reactivity of Aggregates (Chemical Method)
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Modified ASTM C289
ASTM C289 is a chemical method of evaluating
potential reactive aggregates based upon theamount of silica dissolved during a 24 hour digestion
at 80C in 1N NaOH
Modification of method consists of replacing NaOHwith reactant of interest; 1N KOH, saturated Ca(OH)2,
as-received KAc deicer and KAc deicer + Ca(OH)2as
well as 1N NaOH
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Modified ASTM C289
Both solids and solutions are being characterized
full solution chemistries via XRF
solids by optical and SEM analyses with elemental
mapping.
Using local reactive chert for aggregate tests
Potential paste alteration is being evaluated with
tests conducted on neat cement paste
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C289 Test Progress
Three test have been performed with reactive chert
Solutions are at lab for analysis
Solids are being analyzed, preliminary results follow
One neat cement paste run has been completed.
Solutions are awaiting shipment to lab. Solids are
being analyzed
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Control NaOH KOH
Ca(OH)2 K-Ac K-Ac & Ca(OH)2
Polished thin section of carbonate chert, crossed polars.
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Control NaOH KOH
Ca(OH)2 K-Ac K-Ac & Ca(OH)2
Polished thin section of carbonate chert, SEM EDXelemental map for silicon.
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Control NaOH KOH
Ca(OH)2 K-Ac K-Ac & Ca(OH)2
Polished thin section of carbonate chert, SEM EDXelemental map for calcium.
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Control NaOH KOH
Ca(OH)2 K-Ac K-Ac & Ca(OH)2
Polished thin section of carbonate chert, SEM EDXelemental map for potassium.
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Control NaOH KOH
Ca(OH)2 K-Ac K-Ac & Ca(OH)2
Polished thin section of carbonate chert, SEM EDXelemental map for sodium.
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Future work
Continue studies on KAc effects on silica solubility anddissolution rates
Spratt aggregate is on-site and being prepared for testing
Additional aggregates are being identified with particular
interest in moderately reactive aggregates (SiouxQuartzite)
Cement paste alteration studies will continue. A matrixof cements having different properties (alkali content)
will be developed and procured for testing
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What happens to sand if you put it in 12 molal NaOH soln at 200 C?
JENDOUBI F., MGAIDI A., EL MAAOUF M., The Dissolution Kinetics of Sand as Function of Particle Size,
THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, VOLUME 76, p. 233-238, 1998.
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5 minutes later.
JENDOUBI F., MGAIDI A., EL MAAOUF M., The Dissolution Kinetics of Sand as Function of Particle Size,
THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, VOLUME 76, p. 233-238, 1998.
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50 minutes later.
JENDOUBI F., MGAIDI A., EL MAAOUF M., The Dissolution Kinetics of Sand as Function of Particle Size,
THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, VOLUME 76, p. 233-238, 1998.