Research in Alkali Silica Reaction at Georgia Tech

1. Research in Alkali Silica Reaction at Georgia Tech Courtney Collins . Jason Ideker . Gayle Willis . Jessica Hurst

2. What ASR research is going on at the Georgia Institute of Technology?

3. Research Questions • 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?

4. Methods 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.

5. Mortar Bar Experiments

6. 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

7. Mortar Bar Constituents • 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)

8. Mortar Bars- Expansion Testing sample preparation expansion testing

9. Mortar Bar - Expansion Testing Results

10. Mortar Bar - Expansion Testing Results

11. 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

12. Mortar Bar - Microscopy Testing Stereo microscopy Laser scanning confocal microscopy

13. Results - 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

14. Stereo Microscopy Images

15. Stereo Microscopy Images

16. Stereo Microscopy Images

17. Stereo Microscopy Images

18. 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

19. Results - Confocal Microscopy

20. Intensity Map Created Through LCSM Image

21. Video Clip of the LSCM Concrete Image

22. Slurry Sample Experiments

23. Slurry Sample Constituents • 0.7 M NaOH Solution • Silica gel • Calcium additive (Ca(OH)2 or Ca(NO3)2 .4H2O) • Lithium additive (LiOH, LiNO3, LiCl)

24. Slurry Sample Preparation Measuring out materials Finished samples

25. Slurry Sample Testing Sample concentrations will be measured over time, tracking the creation of alkali-silica gel and the exchange of ions in solution Testing still in progress

26. 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)

27. Questions?