Prepared by T.H. Kim, J. Olek, Y. C. Chiu, N. Whiting and T. West for the FHWA ASR TWG meeting,...

Prepared by T.H. Kim, J. Olek, Y. C. Chiu, N. Whiting and T. West for the FHWA ASR TWG meeting, Austin, TX, May 23, 2012 Slide 1/28

PSI-Purdue-Clemson Team

Federal Highway Administration Solicitation No.

DTFH61-08-C-00016Update on Objectives 1 – Tasks 1- 4

FHWA ASR Technical Working Group Meeting

May 23, 2012

Austin, Texas

T. Kim, J. Olek, Y. C. Chiu, N. Whiting and T. West

Purdue University


• 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

Objective 1- List of Tasks


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


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

Potential deliverables for Tasks 1, 2 and 4


Progress update

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

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

Need to Correlate

Chemo-mechanical

study

Tasks1 and 2 Task 4

- Mechanical properties of ASR gel using the nanoindentaion

Expected completion date: Dec., 2012

Suggested additional Task


Progress update: Tasks 1&2

Experimental Program: Mortar specimens undergoing ASR

Mortar specimens W/C[Li]

/[Na+K]Initial Li+ concentration

in mix water (m)*Aggregate type and

content(%) by volumeTemp.

(°C)

NR0.55+0% Li 0.55 0 0 Ottawa (50%) 23, 38, 55NR0.55+35% Li 0.55 0.26 0.159 Ottawa (50%) 23, 38, 55NR0.55+100% Li 0.55 0.74 0.452 Ottawa (50%) 23, 38, 55R0.55+0% Li 0.55 0 0 Jobe (50%) 23, 38, 55R0.55+35% Li 0.55 0.26 0.153 Jobe (50%) 23, 38, 55R0.55+100% Li 0.55 0.74 0.434 Jobe (50%) 23, 38, 55NR: Nonreactive aggregate (Ottawa sand) * corrected for absorption of aggregateR: Reactive aggregate (Jobe sand)100% Li : [Li]/[Na+K] = 0.7435% Li : [Li]/[Na+K] = 0.26

• 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

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

• The reduction in alkali ion concentration in R mortars only, (due to formation of ASR gels)

Decrease due to ASR

Remain constant

Decrease due to ASR

Remain constant

Na+ ions K+ ions

Progress update: Tasks 1&2Changes 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

Remain constant

Slightly decreasing

• In NR mortars, slightly decreasing concentration of OH- ions at 55°C

• Clearly decreasing trends in OH- concentration in R mortars (reaction with silica)

OH- ions

Decrease due to ASR



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con

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of

K+

ion

s

Time (days)

R0.55+0%Li at 38C R0.55+100%Li at 38C

R0.55+0%Li at 55C R0.55+100%Li at 55C

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cen

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of

Na+

ion

s

Time (days)

R0.55+0%Li at 38C R0.55+100%Li at 38C

R0.55+0%Li at 55C R0.55+100%Li at 55C

• 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

• 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

Na+ ions K+ ions



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Time (days)

R0.55+0%Li at 38C R0.55+100%Li at 38C

R0.55+0%Li at 55C R0.55+100%Li at 55C0.00

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trat

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of

Li+

ion

s

Time (days)

NR0.55+100%Li at 38C R0.55+100%Li at 38C

NR0.55+100%Li at 55C R0.55+100%Li at 55C

• 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+ ionsRemain 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



Use of kinetic law to explain the observed changes in alkali levels

Threshold of [Na++K+]: 0.22 M

• 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

R0.55+0%Li R0.55+0%Li



exp

1

Arrhenius equation

exp

64.6kJ mol

a

a

Ek A

RT

E

55°C

38°C

23°CR0.55+0%Li R0.55+0%Li

+ ++ +

exp

Rate Equation

[Na +K 0.22][Na +K 0.22]

dk

dt

• 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+]).




exp

1

Arrhenius equation

exp

64.6kJ mol

a

a

Ek A

RT

E

55°C

38°C

23°CR0.55+0%Li R0.55+0%Li

+ ++ +

exp

Rate Equation

[Na +K 0.22][Na +K 0.22]

dk

dt

• This results strongly indicate that the ASR extent can be directly associated with a simple first order reaction in terms of [Na++K+]




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



Correlation between expansion and the change of Li+ levels


Note: Normalized consumption of [Li+-0.015] were computed using the rate equation similar to sodium rate equation

• 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.



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.


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0 20 40 60 80 100 120g

of C

a(O

H) 2

/ g o

f ce

men

tTime (days)

R0.55-110%Li at 23C

R0.55-100%Li at 38C

R0.55-100%Li at 55C

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g of

Ca(

OH

) 2/ g

of

cem

ent

Time (days)

R0.55-0%Li at 23C

R0.55-0%Li at 38C

R0.55-0%Li at 55C


Progress update: Task 4Silica 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.



Reactor Method• Developed by Bulteel et al. (2002)• Chemical method for quantitative measurement of extent of ASR

Sample Preparation

Polypropylene Copolymer container

20 ml of alkaline solution (0.8 M)

(NaOH, KOH or NaOH+KOH)

5 grams of silica mineral (cristobalite)

+0.5g of Ca(OH)2

• Placed in the oven at one of the designated temperatures (38°C, 50°C and 80°C)

• Stored in the oven for the period from 1 to 50 days



Treatment during Reactor Method Experiment

Sound silica

Degraded silicaSi OH, Si ONa,

Si O Ca O Si

Si O Si

SolutionsNa+, OH-, Ca2+, H2SiO4

2- , H3SiO4-

Ca(OH)2

C-S-H, C-Na-S-H

• Filtration of solution

• Acid treatment

- 250ml of 0.5 M HCl

Stage I Stage 2 Stage 3

• Thermo treatment

- 1000°C

Stage 4

Si OH



Sample

No.Material Temperatrue Sizes (mm) Solutions

Conc. (M)

KOH NaOH LiNO3

1

Silica mineral* 80°C 0.297 to 0.595

KOH 0.8

2 NaOH 0.8

3 KOH+NaOH 0.4 0.4

4 KOH+LiNO3 0.8 0.8

5Silica mineral* 55°C 0.297 to 0.595

KOH 0.8

6 NaOH 0.8

7Silica mineral* 38°C 0.297 to 0.595

KOH 0.8

8 NaOH 0.8

9 Silica mineral* 80°C 0.075 to 0.149 KOH 0.8

Silica mineral* : cristobalite, opal, chalcedony, combination of minerals, reactive aggregate (Jobe sand)

Test Matrix

• Experiments in progress


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


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

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

Progress Update: Tasks 1 and 3


Progress update - Model for determining the loss of lithium ions due to cement hydration-

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)

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


Progress update - Role of deicers -

Mortar bar expansion test (Modified ASTM 1260)• Three types deicers

• 23% NaCl, 25% MgCl2, 28% CaCl2

• Type I high alkali cement (Na2Oeq = 1.04%)• Two types fine aggregates

• Non-reactive: Ottawa sand• Reactive: Jobe sand

• W/C=0.47


Progress update - Mortar bar expansion tests (1/3)-

-0.04%

-0.02%

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0.04%

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0.12%

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Expa

nsio

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Age, days

High Alkali Cement with Non-reactive Aggregate (Ottawa Sand)

DI WaterNaOHNaClMgCl2CaCl2

• 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



-0.08%

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0.16%

0.24%

0.32%

0.40%

0.48%

0.56%

0.64%

0 1 2 3 4 5 6 7 8 9 10

Expa

nsio

n, %

Age, days

High Alkali Cement with Reactive Aggregate (Jobe Sand)

Jobe-DI WaterJobe-NaOHJobe-NaClJobe-MgCl2Jobe-CaCl2

0.2%

0.1%

• 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



-0.08%

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0.16%

0.24%

0.32%

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0.48%

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0 2 4 6 8 10 12 14 16 18 20 22

Expa

nsio

n, %

Age, days

Comparision of High Alkali Cement with Non-reactive and Reactive Aggregate

Ottawa-DI Water Jobe-DI WaterOttawa-NaOH Jobe-NaOHOttawa-NaCl Jobe-NaClOttawa-MgCl2 Jobe-MgCl2Ottawa-CaCl2 Jobe-CaCl2

0.2%

0.1%

• 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

Prepared by T.H. Kim, J. Olek, Y. C. Chiu, N. Whiting and T. West for the FHWA ASR TWG meeting,...

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Transcript of Prepared by T.H. Kim, J. Olek, Y. C. Chiu, N. Whiting and T. West for the FHWA ASR TWG meeting,...