New ASR in concrete Control Strategies

New ASR Control Strategies –
Metakaolin and Other Alternatives
Adjusting ASR Control
Strategies In light of
changes with Fly Ash
and Lithium
ACI Carolina Chapter
September 28, 2016
by Claudio Manissero
President – ChemCognition LLC

Agenda
 Introduction to Alkali Silica Reactivity (ASR)
 ASR Control Options
 Lithium Nitrate new Developments
 Status of Fly Ash
– Availability
– Control of new chemistries involved
 New Alternatives – Metakaolin, VCas
 Economic Considerations

Introduction to ASR
 Alkali Silica Reaction (ASR) occurs between the reactive silica in aggregates
used to make concrete, and the hydroxide and alkalis (sodium or potassium)
present in the concrete pore solution.
 The products of these reactions are alkali silica gels, which may cause
expansion and cracking of concrete in service.
 ASR an issue only if deleterious (e.g. causes damage)
 Development of ASR takes a long time to develop depending on conditions
and reactivity of aggregates
 ASR issues identified in most of the ACI region
 ASR can significantly impact lifecycle as it prevents concrete from meeting
design life.

Identification - Recognize Signs of
Potential ASR

Identification of ASR - References
 Field Inspection - See AC 150/5380-8 – Handbook for Identification of ASR in Airfield
Pavements – 2/2/04
http://www.faa.gov/airports_airtraffic/airports/resources/advisory_circulars/media/150-5380-8/15
 SHRP C-315 – AASHTO Guide
http://leadstates.transportation.org/asr/library/C315/
 Obtain cores - Petrographic analysis
 Laboratory investigations (EM, etc.)
 Review construction records
 Aggregate history
 Mix design
 Testing records
 Review maintenance records
 Obtain deicer usage records (if applicable)

What causes ASR induced cracking?

Solubility of Si+
as Function of pH

ASR Control Options - SHRP Findings
 Use low alkali cement - 0.6% as Na2O equivalent
(Na2O + 0.658 K2O)
 Use nonreactive aggregates
• Petrographic analysis (ASTM C-295)
• Mortar bar test (ASTM C-1260)
• Field history
 Use pozzolans or GGBFS to reduce mobility of alkali. Fly
ash most commonly used, but in many cases only F
allowed (really based on CaO content)
 Use Lithium compounds
 Issue is how to predict efficacy of option

Composition of Tested Fly Ashes

Composition of Tested Fly Ashes
Also note that with the ashes shown here, the calcium contents are very different

ASTM C 1260
 Designed for aggregates only
 Mortar Bar Test (MBT) – soak bar in solution of 1 N
NaOH for 14 days.
 If it passes at ≤ 0.10% expansion @ 14 days, OK
 If not, then test with the Concrete Prism Test (CPT) for 1
year
 Don’t use 28 days unless you already know that this is
appropriate for the aggregate

ASTM C 1567
 Modification of C1260 to test mixes/maeterials –
including fly ash.
 Don’t use unless you have compared the C 1260
result with the CPT
 If it falls into the correct range, then proceed
 If not, then do the 2-yr CPT

All stresses combine to cause cracking

Table of Results from
the CANMET Program

Comparing the 14 day
and the 2 yr CPT
False Positives % of Total
1 3.6
False Negatives % of Total
4 14.3
14 day AMBT vs. 2 yr CPT

and the 2 yr CPT
8 28.6
0 0.0
28 day AMBT vs. 2 yr CPT

and the slab
0 0.0
12 42.9
14 day AMBT vs. Slab

Comparing the 2 yr
CPT and the slab
0 0.0
9 32.1
2 yr CPT vs. Slab

and the slab
1 3.6
2 7.1
28 day AMBT vs. Slab

Precision of Tests
 The CPT, like all tests, gives at best an approximate value – for two main
reasons
– The precision of the test
– The wide range of situations it is supposed to apply to, although it only
uses a single ‘mix design’ and a single alkali loading
 From ASTM C 1293 ---- The multi-laboratory coefficient of variation of a
single test result (mean of measurements of three prisms) for average
expansion greater than 0.014 % has been found to be 23 % (CSA A23.2-
14A-00). Therefore, results of two properly conducted tests in different
laboratories on the same aggregate should not differ from each other by
more than 65 % of their average, nineteen times out of twenty.
 For ASTM C1567 – 43%

Does the C1547 Work in Real Life?

USACE CRD-C 662
 Based on ASTM C1567
 The soak solution storage time is increased to 28 days
 Add the lithium admixture to the mortar in the mixture at the
dosage level to be evaluated
– Details of calculation given in the procedure
 Add the lithium admix to the soak solution at half the molar
ratio evaluated in the mortar
– Details of calculation given in the procedure
 Dosage passes if the expansion at 28 days is < 0.08%

Design / New Construction
 The potential for ASR should always be considered when using silica
containing aggregates.
 History of ASR is a red flag for new construction.
 Lack of ASR, e.g. mix and aggregate history is not a reliable
indicator.
 Traditional test methods not always reliable. Stricter testing
requirements being adopted.
 Potential for ASR derives from both the coarse aggregate and the
fine (e.g. sand). Both should be tested.
 Raw material changes
 Provide industry with alternatives to prevent ASR. Economics will
dictate the best option for the specific case.

ASR Control Options - Considerations
Low alkali cements
Most states require 0.6% - At times too high - ASR occurs even with
low alkali cement. Not effective if using deicing salts.
Sources of low alkali cements diminishing
Issues with total alkali vs. soluble alkali
New plants very expensive, environmental barriers
Not available in many key regions.
Cement companies reacting to ASR issues by developing IP cements
Effect of higher levels of limestone (increases Ca content)
Does not compensate for external alkalies, concentration of alkalies
New trend is to look at total alkali content

Nonreactive Aggregates
Not available in many regions
Transportation costs make it unlikely that nonreactive aggregates will
be shipped very far
Many states require ASR Testing
Tests being adopted are severe (C1260), not good predictors of
performance in-filed or take a long time
Various categories of reactivity
Unreliable and incomplete field histories.
Sources of nonreactive aggregate diminishing.
Expensive option! (more later)

Lithium admixtures
Lithium admixtures have proven in the field to be the most reliable
effective solution for prevention of ASR
Their use is being specified in a number of new projects
Recent issue is that lithium market is short due to increasing demand
in batteries – raw material cost has increased 2-3 X over last six
months.
Result is that pricing of lithium admixtures has more than doubled.
Material is available at higher price but not worthwhile if lower price.
Only way to make it more economically viable is to decrease amount
used by combining with low alkali cement and with pozzolans.
Still best option for critical uses (e.g. nuclear, critical infrastructure)

ASR Control Options – Pozzolans
Considerations
Choice of alternative pozzolans dependent on desired properties,
availability and cost – options:
Fly ash
GGBFS (slag)
Silica Fume
Metakaolin
Low alkali finely ground glass (VCas)
Natural pozzolans
New approach that is yielding promising results is ternary mixtures or
combination of multiple options

Fly Ash - Considerations
 WHEN available, fly ash is the preferred option due to cost and
historical experience
 Issues that are affecting fly ash
– Availability post Duke spills
– War on coal issues
– Economics of coal vs. natural gas
– Changing chemistries driven by new restrictive environmental controls at power
plants
– F ash is useful at correct dosages, but not C. Issue is lime content.
– Dosage may need to be increased if subject to deicers, due to changes in cement
(higher lime content), longer design life, adoption of new more stringent testing
requirements.

Fly Ash - Availability
 Availability in our area has definitely decreased driven by a number of factors.
 Overall availability on East coast is sufficient to meet demand but often not
available at the time it is needed and or right location.
 Industry is implementing a number of strategies to improve it:
– Building significant storage capacity to store during low demand
– Previously unutilized locations being brought on stream
– Reclamation for fly ash ponds (material has to be moved in any case)
– Improvements in infrastructure and logistics for shipping material further
 There are some imports popping up but logistics make it impractical. Beware of
quality and consistency!
 Pricing of fly ash is inevitably increasing at time substantially (expect $ 40-
60/ton increases)

Fly Ash – Control of Changing
Chemistries
 Important parameters to be considered in fly ash for concrete use
– LOI – affects air
– Presence of activated carbon (PAC use for Hg removal)
– Alkali – e.g. Na2O equivalent, soluble vs. total – Use of trona for scrubbing
– Ratio of oxides – particularly relative amounts of silica oxides vs. alumina oxides
– MgO content (hardburned) – Increased use of MgO for scrubbing
– Free sulfate content
– Other components (e.g. amines, ammonia, bromide, mercury etc.)
 Traditional Classification no longer important or valid (F vs. C)
 Industry implementing fly ash treatment processes at power plants to
remove/neutralize activated carbon and other undesirable components
 No good solution yet to prevent delayed expansion if MgO content is
increased by adoption of this scrubbing method.

Fly Ash – Addressing PAC issues with AEA
Work conducted by
Headwaters

Work conducted
by Headwaters

Work conducted by
Headwaters.
Implementation of
RestoreAIR
technologies.

ASR Control Options - Metakaolin
 Limited work has been done with metakaolin to establish control
levels for ASR using new tests
 Data according to standard tests indicate that levels of metakaolin
needed are 8-12% cement replacement
 Limited work has been done on tests similar to C1567 in Brazil and
material has performed well in a number od dam projects there.
 Properties vary depending on source of metakaolin – some material
can have high water absorption and requires high levels of HRWR
 Material readily available from various sources and interest in its use
for ASR is increasing.
 Testing program being devised and seeking sponsors.

ASR Control Options - Metakaolin

ASR Control Options - VCas
 VCas is a recycled ground glass that is produced from e-glass, low alkali type
glass. Two grades available VCas1 and VCas2
 Other type glass not good for ASR due to high alkali levels
 Material is a pozzolan as it will react with lime to make CSH
 Testing of both conducted on highly reactive rhyolite from NM using a
modified ASTM C1567 (AMBT) and USACE CRD-C 662
 Comparisons with F fly ash and lithium nitrate admixture were evaluated
 Combinations with lithium nitrate were also evaluated
CONCLUSIONS
 VCAS1 and VCAS2 materials were more effective in ASR control with the
highly reactive rhyolite than equivalent amounts of Class F fly ash
 VCAS1 and VCAS2 materials were very effective in combination with lithium
nitrate admixture

How Does ASR Impact The Industry?
 The design engineer needs to be aware of ASR potential with
currently available local materials
 Warranty and liability issues are likely to increase
 New technologies are now available to produce ASR-resistant
concrete
 The engineer has a fiduciary duty towards the owner to utilize the
latest knowledge and new technologies when applicable.
 Owner concerns are durability and design life – ASR affects both
 Owners have to understand that in the new reality ASR control
strategies will result in higher costs
 Does lowest initial cost provide a prudent approach to durability?

Recommendations to address ASR
 Require testing of both coarse and fine aggregates
– Modified ASTM C1260 with expansion less than 0.1 % at 28 days
– If field history shows ASR, then require ASR abatement
 Require low alkali cement (below 0.6% Na2O eq.) – but provide allowance based on test
performance
 Allow the following mitigation options
– Use of unreactive aggregates
– Use of appropriate pozzolans – No definition of Class but implement restrictions on
chemistry.
– Broaden allowed pozzolans to include metakaolin, low alkali glass (Vcas), natural
pozzolans
– Use of lithium admixtures for critical infrastructure – follow manufacturer
recommendations
– Allow combinations of low alkali cements, multiple pozzolans pozzolans and lithium
 Require testing of mix
– Modified ASTM C1567 with expansion less than 0.1 % at 28 days

Economics
 Cost of the various options is reasonable and are in general comparable. Best
option varies dependent on specific locations.
 Mitigation options are usually less costly than obtaining nonreactive aggregates if
those must be shipped >100 miles or more depending on mix design and local
economics.
 Cost of options is minimized by using it in combination with suitable pozzolans.
 There may be problems with availability of traditional/good Fly Ash in area, but
overall availability is being addressed.
 Costs to beneficiate Fly Ash as well as supply/demand will affect price of fly ash.
 For critical infrastructure lithium is a prudent choice and is available.
 Overall expect the following:
– Fly ash will continue to be available but cost will probably increase
– Need to revise mixes to look at alternative options (lithium, mixed pozzolans etc.)
– Lithium increasing costs will limit its economic viability but effectiveness is proven
– Expect that overall cost of durable concrete will increase.

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