Objective 2 - Rapid Test Methods for Assessing Asr in The ...
Evaluating the ASR Potential of Aggregates and Effectiveness of ASR Mitigation Measures in Miniature Concrete Prism Test Enamur R Latifee, Graduate Student Glenn Department of Civil Engineering Clemson University Concrete Materials Seminar February 17, 2012 Acknowledgement
Dr. Prasad Rangaraju, Associate Professor, Glenn Department of Civil Engineering Clemson University Dr. Paul Virmani, FHWA Presentation Outline 1. ASR review 2. Introduction to Miniature Concrete Prism Test (MCPT) 3. Evaluation of Effectiveness of SCMs for ASR Mitigation in the MCPT 4. Effect of Prolonged Curing of Test
Specimens on the Performance of Fly Ashes in MCPT Test Method Beginning of ASR Research Alkali-Silica Reaction Distresses in the field Field symptoms of ASR in concrete structures More ASR Distress Some Case Histories
Buck Hydroelectric plant on New River (Virginia, US) Arch dam in California crown deflection of 127 mm in 9 years Railroad Canyon Dam Morrow Point Dam, Colorado, USA Stewart Mountain Dam, Arizona
Parker Dam (Arizona) expansion in excess of 0.1 percent Case Study: Parker Dam, California Alkali-Aggregate Reactions in Hydroelectric Plants and Dams: http://www.acres.com/aar/ Hydroelectric dam built in 1938 180 mm of arch deflection due to alkali silica gel expansion Cracking and gel flow in concrete Case Study: I-85 - Atlanta, Georgia
Possible ASR damage on concrete retaining wall Typical Distress Observed in Concrete Pavement Exposed to Airfield Deicing Chemicals Typical Distress Observed in Concrete Pavement Exposed to Airfield Deicing Chemicals Example: Shek Wu Hui Treatment plant, Hong Kong Example: Daqing Railway Bridge, China
Countries reported ASR problems 1 AUSTRALIA 2 CANADA 3 CHINA 4 DENMARK 5 FRANCE 6 HONG KONG 7 ICELAND 8 ITALY 9 JAPAN 10 KOREA 11 NETHERLANDS 12 NEW ZEALAND
13 NORWAY 14 ROMANIA 15 RUSSIA 16 PORTUGAL 17 SOUTH AFRICA 18 SWITZERLAND 19 TAIWAN 20 UNITED KINGDOM 21 UNITED STATES OF AMERICA ASR reported locations around the globe ASR
ASR is the most common form of alkali-aggregate reaction (AAR) in concrete; the other, much less common, form is alkali-carbonate reaction (ACR). For damaging reaction to take place the following need to be present in sufficient quantities. High alkali cement Reactive aggregate Moisture [above 75%RH within the concrete]
ASR Aggregate reactivity depends directly on the alkalinity (typically expressed as pH) of the solution in the concrete pores. This alkalinity generally primarily reflects the level of water-soluble alkalis (sodium and potassium) in the concrete. These alkalis are typically derived from the Portland cement. Chemistry of Alkali Silica Reaction Cement production involves raw materials that contain alkalis in the range of 0.2 to 1.5 percent of Na2O
This generates a pore fluid with high pH (12.5 to 13.5) Strong alkalinity causes the acidic siliceous material to react ASTM specification ASTM C150 designates cements with more than 0.6 percent of Na2O as high-alkali cements Even with low alkali content, but sufficient amount of cement, alkali-silica reactions can occur Investigations show that if total alkali content is
less than 3 kg/m3, alkali-silica reactions will not occur (ASTM 1293, 1.25% alkali of 420kg/m3 =5.25kg/m3) Other sources of alkali Even if alkali content is small, there is a chance of alkali-silica reaction due to alkaline admixtures aggregates that are contaminated penetration of seawater deicing solutions Creation of alkali-silica gel
Reactive Silica Silica tetrahedron: Amorphous Silica Crystalline Silica Creation of alkali-silica gel Reactive Silica Amorphous or disordered silica = most chemically reactive Common reactive minerals:
strained quartz opal obsidian cristobalite tridymite chelcedony cherts cryptocrystalline volcanic rocks Creation of alkali-silica gel 1. Siliceous aggregate in solution Creation of alkali-silica gel
2. Surface of aggregate is attacked by OH- H20 + Si-O-Si Si-OHOH-Si Creation of alkali-silica gel 3. Silanol groups (Si-OH) on surface are broken down by OH- into SiO- molecules Si-OH + OH- SiO- + H20
Creation of alkali-silica gel 4. Released SiO- molecules attract alkali cations in pore solution, forming an alkali-silica gel around the aggregate. Si-OH + Na+ + OH- Si-O-Na + H20 Creation of alkali-silica gel 5. Alkali-silica gel takes in water, expanding and exerting an osmotic pressure against the surrounding paste or aggregate. Creation of alkali-silica gel
6. When the expansionary pressure exceeds the tensile strength of the concrete, the concrete cracks. Creation of alkali-silica gel 7. When cracks reach the surface of a structure, map cracking results. Other symptoms of ASR damage includes the presence of gel and staining. Creation of alkali-silica gel 8. Once ASR damage has begun: Expansion and cracking of concrete Increased permeability
More water and external alkalis penetrate concrete Increased ASR damage Images of ASR damage SILICA MINERALS IN ORDER OF DECREASING REACTIVITY 1. # Amorphous silica: sedimentary or volcanic glass (a volcanic glass that is devitrified and/or mostly recrystallized may still be reactive) 2. # Opal 3. # Unstable crystalline silica (tridymite and cristobalite)
4. # Chert 5. # Chalcedony 6. # Other cryptocrystalline forms of silica 7. # Metamorphically granulated and distorted quartz 8. # Stressed quartz 9. # Imperfectly crystallized quartz 10. # Pure quartz occurring in perfect crystals ROCKS IN ORDER OF DECREASING REACTIVITY 1. # Volcanic glasses, including tuffs (especially highly siliceous ones) 2. # Metaquartzites metamorphosed sandstones)
3. # Highly granulated granite gneisses 4. # Highly stressed granite gneisses 5. # Other silica-bearing metamorphic rocks 6. # Siliceous and micaceous schists and phyllites 7. # Well-crystallized igneous rock 8. # Pegmatitic (coarsely crystallized) igneous rock 9. # Nonsiliceous rock ASR Research Time Line 1940-1960 1. Stanton, 1940, California Division of Highway 2. Mather, 1941, Concrete Laboratory of the Corps of Engineers
3. ASTM C 227-10, 1950, Standard Test Method for Potential Alkali Reactivity of Cement-Aggregate Combinations 4. ASTM C 289, Quick chemical method, 1952 5. The Conrow test, 1952, ASTM C 342, 1954- withdrawn -2001 6. ASTM C 295, Petrographic Examination of Aggregates, 1954 7. ASTM C1293, Concrete Prism Test, 1950s, Swenson and Gillott, 8. Gel pat test, Jones and Tarleton, 1958 1960 -1990 9. ROCK CYLINDER METHOD, 1966 10. Nordtest accelerated alkali-silica reactivity test, Saturated NaCl bath method Chatterji , 1978 11. JIS A1146, Mortar bar test method, Japanese Industrial Standard (JIS)
12. Accelerated Danish mortar bar test, Jensen 1982 13. Evaluation of the state of alkali-silica reactivity in hardened concrete, Stark, 1985 14. ASTM C 1260, Accelerated mortar bar test (AMBT); South African mortarbar test- Oberholster and Davies, 1986, 15. Uranyl acetate gel fluorescence test, Natesaiyer and Hover, 1988 April 14, 2009 39/38 1991 -2010 16. Autoclave mortar bar test, Fournier et al. (1991) 17. Accelerated concrete prism test, Ranc and Debray, 1992 18. Modified gel pat test, Fournier, 1993
19. Chinese concrete microbar test (RILEM AAR-5) 20. Chinese autoclave test (CES 48:93), Japanese autoclave test, JIS A 1804 21. Chinese accelerated mortar bar methodCAMBT, 1998 22. Chinese concrete microbar test (RILEM AAR-5), 1999 23. Modified versions of ASTM C 1260 and ASTM C 1293,Gress, 2001 24. Universal accelerated test for alkali-silica and alkali-carbonate reactivity of concrete aggregates, modified CAMBT, Duyou et al., 2008 April 14, 2009 40/38 Common Test Methods to assess ASR
RILEM SURVEY (Nixon And Sims 1996) Reunion Internationale des Laboratoires et Experts des Materiaux, Systemes de Construction et Ouvrages (French: International Union of Laboratories and Experts in Construction Materials, Systems, and Structures) All countries, reported that no one test is capable of providing a comprehensive assessment of aggregates for their alkali-aggregate reactivity. Part 2: Introduction to MCPT
Introduction to MCPT MCPT has been developed to determine aggregate reactivity, with: - Similar reliability as ASTM C 1293 test but shorter test duration (56 days vs. 1 year) - Less aggressive exposure conditions than ASTM C 1260 test but better reliability Variables Variable test conditions Storage environment Exposure condition
1N NaOH 100% RH 100% RH (Towel Wrapped) Temperature 38 C 60 C 80 C Sample Shape Prism (2 x 2 x 11.25) Cylinder (2 dia x 11.25 long)
Soak Solution Alkalinity (0.5N, 1.0N, and 1.5N NaOH solutions) Aggregates used in the Variables Four known different reactive aggregates were used for these variables. These are as follows: Spratt Limestone of Ontario, Canada, New Mexico, Las Placitas-Rhyolite, North Carolina, Gold Hill -Argillite, South Dakota, Dell Rapids Quartzite Effect of Storage Condition 100% RH, Free standing
1N NaOH Soak Solution 100% RH, Towel Wrapped % Expansion Effect of Storage Condition on Expansion in MCPT SP- MCPT Expansion with Different Curing Conditions 0.24 0.22 0.2 0.18
Specimen size = 2 in. x 2 in. x 11.25 in. Max. Size of Aggregate = in. (12.5 mm) Volume Fraction of = 0.65 Dry Rodded Coarse Aggregate in Unit Volume of Concrete Coarse Aggregate Grading Requirement: Sieve Size, mm Passing Retained
= 0.9% 0.1% Na2Oeq. Alkali Boost, (Total Alkali Content) = 1.25% Na2Oeq. by mass of cement Water-to-cement ratio = 0.45 Storage Environment = 1N NaOH Solution Storage Temperature = 60CC Initial Pass/Fail Criteria = Exp. limit of 0.04% at 56 days Use non-reactive fine aggregate, when evaluating coarse aggregate Use non-reactive coarse aggregate, when evaluating fine aggregate
Specimens are cured in 60CC water for 1 day after demolding before the specimens are immersed in 1N NaOH solution. Expansion Data of Test Specimens Containing Selected Aggregates in Different Test Methods (Note: red:- reactive, green:- non-reactive) Aggregate Identity % Expansion MCPT, 56 Days ASTM C 1293, 365 days
ASTM C 1260, 14 days L4-SP 0.149 0.181 0.350 L11-SD
0.150 0.460 Proposed criteria for characterizing aggregate reactivity in MCPT protocol Degree Reactivity of % Expansion at
56 Days Rate of Expansion from 8 to 10 weeks Non-reactive < 0.040 % < 0.010% per two weeks Low
0.035% 0.060% > 0.010% per two weeks Moderate 0.060% 0.120% N/A High > 0.120%
N/A Comparison of MCPT-56 with CPT-365 ASTM C 1293, CPT vs. MCPT 56 Days Expansion 0.48 f(x) = 1.37 x 0.02 MCPT R = 0.990.04% limit at 56 days 0.4
0.32 0.24 Fine Aggregate % Expansion at 56 Days, MCPT 0.6 0.56 0.52
0.48 Coarse Aggregate 0.44 0.36 0.32 0.28 0.24
0.16 0.12 0.08 0 0.04 0.08
0.2 CPT 0.04% limit at 365 days 0.4 0.16 0 % Expansion at 365 Days, CPT
0.56 Part 3: Evaluation of Effectiveness of SCMs for ASR Mitigation in the MCPT Supplementary Cementing Materials (SCMs) Fly Ashes for ASR Mitigation in the MCPT Three fly ashes 1. Low-lime fly ash 2. intermediate-lime fly ash, and
3. high-lime fly ash All were used at a dosage of 25% by mass replacement of cement Effectiveness of low-lime, intermediate-lime and high-lime fly ashes in mitigating ASR in MCPT method using Spratt limestone as reactive aggregate Later nine different fly ashes (3 high-lime -HL, 3 low-limeLL and 3 intermediate-lime- IL fly ashes) at 25% cement replacement levels were investigated Nine different fly ashes (3 high-lime, 3 low-lime and 3 intermediate-lime fly ashes) at 25% cement replacement
levels Effectiveness of Slag, Meta-kaolin, Silica fume and LiNO3 in mitigating ASR Spratt limestone as reactive aggregate Mass replacement of cement Slag was used at a dosage of 40% Metakaolin was used at a dosage of 10% Silica Fume was used at a dosage of 10% Additionally LiNO3 was used at a dosage of 100% Effectiveness of Slag, Meta-kaolin, Silica fume and LiNO3 in mitigating ASR in MCPT method using Spratt limestone as
reactive aggregate Part 3: Effect of Prolonged Curing of Test Specimens on the Performance of Fly Ashes in MCPT Test Method Effect of Prolonged Curing of Test Specimens on the Performance of Fly Ashes in MCPT Test Method MCPT test specimens cured for varying lengths of time Days: 1 day, 7 days, 14 days and 28 days ; before they were exposed to 1N NaOH solution Three fly ashes of significantly different chemical composition (Lowlime fly ash, intermediate-lime fly ash and high-lime fly ash) were
selected. Low Lime-Class F fly ash at 25% cement replacement Intermediate Lime fly ash at 25% cement replacement High Lime-Class C fly ash at 25% cement replacement Conclusions The findings from the extended initial curing of test specimens in MCPT showed that there is no added benefit in increasing the duration of initial curing in assessing the effectiveness of ASR mitigation measures such as supplementary cementitious materials.
Based on the results, MCPT appears to be a viable test method that can potentially replace both AMBT (ASTM C 1260) and CPT (ASTM C 1293) for routine ASR-related testing. Future Steps Develop a protocol for evaluation of Job Mixtures for Potential ASR Questions? [email protected]
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