courtney collins. jason ideker. gayle willis. jessica hurst research in alkali silica reaction at...
TRANSCRIPT
Courtney Collins . Jason Ideker . Gayle Willis . Jessica Hurst
Research in Alkali Silica Reaction at Georgia Tech
What ASR research is going on at the Georgia Institute of Technology?
• Which lithium compounds work best to stop ASR?
• How much of the lithium additives is needed to prevent ASR, relative to alkali-content of concrete?
• How much of the lithium additive will be lost to the environment?
• What is the most effective way to add lithium compounds to concrete experiencing ASR?
Research Questions
Mortar bars• Measure expansion over time• Examine at microscopic level to look for gel growth and microcracking
Slurry samples• Use to imitate pore solution in concrete• Looking for changing concentrations
of free Na, Li, Si, Ca due to reactions with silica and water
• Silica gel particles imaged over time.
Methods
Mortar Bar Experiments
1. Mortar bars are made using various lithium additives and expansion is measured over time
2. Confocal and stereo microscopy are used to look at any microcracking and gel formation in smaller mortar bar samples
Mortar Bar Experiments
• Artesia Type I cement• Crushed graded glass aggregate (expansion)• Glass beads (1, 2 and 3 mm) (imaging)• 0.7M NaOH Solution (H2O and partial Na source)
• Various lithium salts (LiOH, LiNO3, LiCl)
Mortar Bar Constituents
Mortar Bars- Expansion Testing
sample preparation
expansion testing
Mortar Bar - Expansion Testing Results
Expansion of mortar bars with and without LiOH over time
0.00
0.05
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0.15
0.20
0.25
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0.35
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0 10 20 30 40 50 60
Time (days)
Ex
pa
ns
ion
(%
)
Na:Li=1:0 Na:Li=1:0.5 Na:Li=1:1 Na:Li=1:1.5
Expansion of mortar bars with and without LiNO3 over time
0.00
0.10
0.20
0.30
0.40
0.50
0 10 20 30 40 50 60
Time (days)
Ex
pa
ns
ion
(%
)
Na:Li=1:0 Na:Li=1:0.01 Na:Li=1:0.25
Na:Li=1:0.5 Na:Li=1:1 Na:Li=1:1.5
Mortar Bar - Expansion Testing Results
Expansion of mortar bars with and without LiCl over time
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0.10
0.20
0.30
0.40
0.50
0 10 20 30 40 50 60
Time (days)
Ex
pa
ns
ion
(%
)
Na:Li=1:0 Na:Li=1:0.5 Na:Li=1:1 Na:Li=1:1.5
Expansion of mortar bars with LiOH, LiNO3, and LiCl over time
0.000.010.010.020.020.030.030.040.040.05
0 10 20 30 40 50 60
Time (days)
Ex
pa
ns
ion
(%
)
LiOH LiNO3 LiCl
Mortar Bar - Microscopy Preparation
• Mortar bar specimen cut to approximately 1.0” • Sample is polished with sandpaper, final polishing
with cerium oxide powder and deionized water• Sample is epoxied to aluminum plate• Viewed using laser scanning confocal microscopy
(LSCM) and stereo microscopy
Mortar Bar - Microscopy Testing
Laser scanningconfocal microscopy
Stereo microscopy
• Images were taken over time and progressive damage was witnessed
• Reference samples (no lithium additives) showed most damage
• Crystals seen at paste and aggregate interface
Results - Stereo Microscopy
Stereo Microscopy Images
Stereo Microscopy Images
Stereo Microscopy Images
Stereo Microscopy Images
Results - Confocal Microscopy
• Images taken at progressive depths into aggregate, some gel formation seen
• Video of aggregate rotation created, progressive-depth imaging allowing the aggregate to be seen in 3D
Results - Confocal Microscopy
0
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60
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0 50 100 150 200 250 300 350 400
X (m)
Re
lati
ve I
nte
nsi
ty
Intensity Map Created Through LCSM Image
Video Clip of the LSCM Concrete Image
Slurry Sample Experiments
• 0.7 M NaOH Solution
• Silica gel
• Calcium additive (Ca(OH)2 or Ca(NO3)2 .4H2O)
• Lithium additive (LiOH, LiNO3, LiCl)
Slurry Sample Constituents
Slurry Sample Preparation
Measuring out materials
Finished samples
Slurry Sample Testing
Sample concentrations will be measuredover time, tracking the creation of alkali-silicagel and the exchange of ions in solution
Testing still in progress
Mortar Bar/Slurry Sample Comparison
Na:Li is same for mortar bars and slurries-1:0.25, 1:0.5, 1:1, or 1:1.5
Slurry samples are more ideal tools because they are made at the pessimum proportion
- (Glasser and Kataoka, 1981)
Questions?