1 / 28

PSI-Purdue-Clemson Team

PSI-Purdue-Clemson Team. Federal Highway Administration Solicitation No. DTFH61-08-C-00016. Update on Objectives 1 – Tasks 1- 4. T. Kim , J. Olek , Y. C. Chiu, N . Whiting and T. West Purdue University. FHWA ASR Technical Working Group Meeting May 23, 2012 Austin, Texas.

meris
Download Presentation

PSI-Purdue-Clemson Team

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. PSI-Purdue-Clemson Team Federal Highway Administration Solicitation No. DTFH61-08-C-00016 Update on Objectives 1 – Tasks 1- 4 T. Kim, J. Olek, Y. C. Chiu, N. Whiting and T. West Purdue University FHWA ASR Technical Working Group Meeting May 23, 2012 Austin, Texas

  2. Objective 1- List of Tasks • Task 1: Role of lithium (and other ions) in preventing or reducing the effects of ASR • Task 2: Role of Calcium ions in ASR • Task 3: Role of deicers, hydroxyl and alkali ions • Task 4: Role of aggregate • Task 5: Role of Moisture and Crack • Task 6: Monitoring Crack formation

  3. Objectives for Tasks 1, 2 and 4 • Tasks 1 and 2 (Role of lithium and role of calcium) • Determination of changes in composition of the pore solution and the content of Ca(OH)2 in mortars undergoing ASR • Correlation of changes in chemical composition in pore solution with mechanical expansion • Task 4 (Role of aggregates) • Examination of the role of chemical composition, structure and mineralogy of aggregates in the overall mechanism of ASR • Establishment of database of kinetic parameters for reactions involving silica minerals in concrete-like (high pH) environment • Development of the kinetic model for prediction of the extent of ASR

  4. Potential deliverables for Tasks 1, 2 and 4 • Establishment of the database of kinetic parameters for reactions involving silica minerals • Having this data will help with • quantitative analysis of ASR and with • screening of potentially reactive aggregates • Establishment of the framework for predicting potential reactivity of certain types of aggregates based on the fundamental principles

  5. Progress update Tasks1 and 2 Task 4 • Silica minerals undergoing ASR • Changes in pore solutions (30%) • Changes in alkali concentration (40%) • Changes in the content of Ca(OH)2 (40%) • Quantitative information about formation of ASR gel (40%) • Effects of temperatures (40%) • Model linking mineralogy of aggregates with the extent of ASR • Establishment of kinetic parameters (40%) • Verification through the experiments (0%) • Expected completion date: Dec, 2012 • Specimens undergoing ASR • Changes in composition of pore solution (100%) • Changes in alkali concentration (100%) • Changes in the content of Ca(OH)2 (100%) • Effects of temperatures (100%) • SEM analysis (60%) • Expansion (95%) • Expected completion date: July., 2012 Need to Correlate Chemo-mechanical study Suggested additional Task • Mechanical properties of ASR gel using the nanoindentaion • Expected completion date: Dec., 2012

  6. Progress update: Tasks 1&2 Changes in chemical composition of pore solution undergoing ASR Experimental Program: Mortar specimens undergoing ASR • Analysis of pore solutions from mortars (IC and AA) completed • Quantification of the Ca(OH)2 content (TGA) completed • SEM investigation of ASR gels- ongoing

  7. Progress update: Tasks 1&2 Changes in chemical composition of pore solution undergoing ASR Effects of type of aggregate (NR and R) on alkali ions (Na+ and K+) Effects of Temperatures (55°C and 38°C) Concentrations normalized w.r.t the one day concentration values K+ ions Na+ ions Remain constant Remain constant Decrease due to ASR Decrease due to ASR • The reduction in alkali ion concentration in R mortars only, (due to formation of ASR gels)

  8. Progress update: Tasks 1&2 Changes in chemical composition of pore solution undergoing ASR Effects of type of aggregate (NR and R) on OH- ions Effects of Temperatures (55°C and 38°C) Concentrations normalized w.r.t the one day concentration OH- ions • In NR mortars, slightly decreasing concentration of OH- ions at 55°C • Clearly decreasing trends in OH- concentration in R mortars (reaction with silica) Remain constant Slightly decreasing Decrease due to ASR

  9. Progress update: Tasks 1&2 Changes in chemical composition of pore solution undergoing ASR Effects of addition of LiNO3 on concentrations of alkali ions in pore solution Effects of Temperatures (55°C and 38°C) Concentrations normalized w.r.t the one day concentration values Na+ ions K+ ions • Addition of LiNO3 significantly reduces the loss of alkali ions (0%Li > 35%Li > 100%Li) • Alkali ions do not combine with silica ions and remain in the solution

  10. Progress update: Tasks 1&2 Changes in chemical composition of pore solution undergoing ASR Effects of addition of LiNO3 in mortar on OH- and Li+ ions Effects of Temperatures (55°C and 38°C) Concentrations normalized w.r.t the one day concentration values OH- ions Li+ ions Remain constant or slightly decrease Decrease due to ASR • No effects of addition of LiNO3 on levels of OH- ions, implying that Li+ ions do not have effect on the dissolution of silica (due to OH- ions attack on the silica surface) • In reactive mortars, the concentration of Li+ ions decreases continually

  11. Progress update: Tasks 1&2 Changes in chemical composition of pore solution undergoing ASR Use of kinetic law to explain the observed changes in alkali levels Threshold of [Na++K+]: 0.22 M R0.55+0%Li R0.55+0%Li • Linear correlation was observed between ln[Na++K+-0.22] and time. This can be interpreted as representing ASR as the first order reaction with respect to alkali ions. • Slopes of the line represent the rate constants (kexp, s-1)for each temperatures

  12. Progress update: Tasks 1&2 Changes in chemical composition of pore solution undergoing ASR Use of kinetic law to explain the observed changes in alkali levels 55°C 38°C 23°C R0.55+0%Li R0.55+0%Li • Constant value of kexp (at specific temperature) and the good fit for Arrhenius equation indicate that for a specific system (having given composition and aggregate type) the rate and the extent of ASR depend mainly on the sum of the concentration of alkali ions ([Na++K+]).

  13. Progress update: Tasks 1&2 Changes in chemical composition of pore solution undergoing ASR Use of kinetic law to explain the observed changes in alkali levels 55°C 38°C 23°C R0.55+0%Li R0.55+0%Li • This results strongly indicate that the ASR extent can be directly associated with a simple first order reaction in terms of [Na++K+]

  14. Progress update: Tasks 1&2 Changes in chemical composition of pore solution undergoing ASR Correlation between expansion and the change in alkali levels • Overall trends of expansion are very similar to the trend of the normalized consumption of available alkali ions [Na++K+-0.22] • In low temperatures, the expansion is delayed with respect to the observed consumption of alkali ions • The results strongly indicate that extent of expansion can be correlated to the extent of alkali consumption • Normalized consumption of [Na++K+-0.22] were computed using the rate equation

  15. Progress update: Tasks 1&2 Changes in chemical composition of pore solution undergoing ASR Correlation between expansion and the change of Li+ levels • The use of kinetic law to explain the observed change of Na+ and K+ ions more complicated in the presence of Li+ ions (ongoing effort). • Clear change in the expansion rate observed at the point of depletion of available Li+ ions. • These results seem to indicate that the Li+ ions available in the pore solution are preferentially consumed in the ASR and thus suppress the expansion. • Note: Normalized consumption of [Li+-0.015] were computed using the rate equation similar to sodium rate equation

  16. Progress update: Tasks 1&2 Changes in chemical composition of pore solution undergoing ASR Change of Ca(OH)2 content in mortars undergoing ASR • The content of Ca(OH)2 in the reactive mortars (with or without LiNO3) remained more or less identical over time regardless of the temperature.

  17. Progress update: Task 4 Silica minerals undergoing ASR (Reactor method) Role of the aggregates • To advance the previous relation between ASR extent and [Na++K+] ions, the investigation of the rate constant (kexp) is required since this constant is dependent on the nature of reactive aggregates. • One of the main factor to influence of their reactivity is the type of reactive silica minerals in the reactive aggregate. • Thus, constructing the kinetic parameters for reactive silica minerals involving ASR process will help with quantitative analysis of ASR.

  18. Progress update: Task 4 Silica minerals undergoing ASR (Reactor method) Reactor Method • Developed by Bulteel et al. (2002) • Chemical method for quantitative measurement of extent of ASR Sample Preparation • Placed in the oven at one of the designated temperatures (38°C, 50°C and 80°C) Polypropylene Copolymer container 20 ml of alkaline solution (0.8 M) (NaOH, KOH or NaOH+KOH) • Stored in the oven for the period from 1 to 50 days 5 grams of silica mineral (cristobalite) +0.5g of Ca(OH)2

  19. Progress update: Task 4 Silica minerals undergoing ASR (Reactor method) Treatment during Reactor Method Experiment Stage I Stage 2 Stage 3 Stage 4 Solutions Na+, OH-, Ca2+, H2SiO42- , H3SiO4- Sound silica • Filtration of solution Ca(OH)2 • Acid treatment • - 250ml of 0.5 M HCl • Thermo treatment • - 1000°C Degraded silica C-S-H, C-Na-S-H

  20. Progress update: Task 4 Silica minerals undergoing ASR (Reactor method) Test Matrix • Experiments in progress

  21. Objectives of related studies (Tasks 1 and 3) Task 1 (Role of lithium) • To provide better understanding of the role of lithium ions • Establishment of model to predict the extent of Li+ ions loss from the pore solution • Development of Li+ ion delivery method which can potentially minimize early age losses Task 3 (Role of deicers) • Strengthening the understanding of the effects of deicers on ASR Potential deliverables • The model to predict the extent of Li+ ions loss from the pore solution • The technique to reduce the required LiNO3 dosage for effective mitigation of ASR • Advanced understanding the role of deicers in ASR

  22. Progress Update: Tasks 1 and 3 Task 1 • Assessment of the interaction between lithium and other ions (100%) • Establishment of model to predict the extent of Li+ ions loss from the pore solution (100%) • Providing better understanding the role of lithium (90%) • Development of Li+ ions delivery method which can potentially minimize early age losses of the admixture (40%) Expected completion date: Dec., 2012

  23. Progress Update: Tasks 1 and 3 • Task 3 • Study of the formation of potassium sulfate phases in the presence of potassium acetate (100%) • Evaluation of morphology and composition of ASR gels formed in the presence of different deicers (70%) • Evaluation of the level of hydroxyl ions in systems exposed to different deicers (50%) • Mortar bar expansion tests (80%) Expected completion date: Dec., 2012

  24. Progress update - Model for determining the loss of lithium ions due to cement hydration- Plot of measured vs. predicted concentration of Li+ ions (3 different sets of data, 5 different cements, 4 different w/c and 8 different lithium dosages Verification of the model equation (data from Kim and Olek (2012), Bérubé et al., CCR, Vol. 34 (2004), pp. 1645-1660 and Diamond, CCR, Vol. 29 (1999), pp. 1271-1275)

  25. Progress update - Role of deicers - Mortar bar expansion test (Modified ASTM 1260) • Three types deicers • 23% NaCl, 25% MgCl2, 28% CaCl2 • Type Ihigh alkali cement (Na2Oeq = 1.04%) • Two types fine aggregates • Non-reactive:Ottawa sand • Reactive:Jobe sand • W/C=0.47

  26. Progress update - Mortar bar expansion tests (1/3)- • Specimens immersed in DI water, NaOH and NaCl exhibit more or less same expansion (less than 0.02% at 14 days) • Specimens in CaCl2 show some expansions even in non-reactive aggregate • Specimens in MgCl2 show some shrinkage up to 2 days and then slightly expand • Overall, all specimens exhibited less than 0.1% of expansion at 14 days

  27. Progress update - Mortar bar expansion tests (2/3)- • Specimens immersed in NaCl and NaOH exhibit significant expansion caused by ASR • Specimens in CaCl2 also expand but the level of expansion is much lower than those in NaCl and NaOH • Specimens in MgCl2 also show some shrinkage

  28. Progress update - Mortar bar expansion tests (3/3)- • NaCl clearly affects the expansion of reactive mortar specimens, which indicate the acceleration of ASR • Reactive mortar specimens in CaCl2 and DI water show higher expansion than non-reactive mortar specimens in CaCl2 • Up to 6 days, expansions of specimens immersed in MaCl2 does not show clear difference between reactive and non-reactive mortar specimens

More Related