Upload
nguyenhuong
View
242
Download
0
Embed Size (px)
Citation preview
Industry experience with ASRIndustry experience with ASR requirements in project specifications
Colin Lobo, Sr. VP Engineering
ASTM Workshop, St. Louis, MOJune, 2010June, 2010
Ideal ASR Specification
Determine reactivity of aggregatesS i d l l hi tService record or local historyTest results of aggregates (a reliable test)
preferably by aggregate supplier (ASTM C33)preferably by aggregate supplier (ASTM C33)
Determine if service conditions need mitigationMoistureCritical nature of structure
Establish mitigative measuresgService record or local historyTest to “accepted” criteria
WWW. NRMCA.ORG
Prescription based on best current understanding
Problems
Number of ASR testsNumber of ASR testsContradicting indications
No “standard” national guide specificationNo standard national guide specificationProject Specifications:
Old provisions proven not to workOld provisions proven not to workAdd on “new” provisionsExtend the recommended criteriaExtend the recommended criteriaInclude all potential protective measuresIncompatible with other performance requirements
WWW. NRMCA.ORG
Incompatible with other performance requirements
Typical clauses
Use non reactive aggregatesUse non reactive aggregatesDiffering tests and criteria
Use a low alkali cementUse a low alkali cement0.6%; 0.4% Na2Oe
Limits on supplementary cementing materialsLimits on supplementary cementing materialsMin and maxCompositional limitsCompositional limits
Document mitigating methodsDiffering tests and criteria
WWW. NRMCA.ORG
Differing tests and criteria
Implications to performance/sustainability
Fast track workRate of strength gainSetting characteristics
Inherent specification / performance conflictsSustainability
Minimize wasteRecycled contentRegional materials
Transportation
WWW. NRMCA.ORG
ASR test methods
Science based – difficult to perform (C289)p ( )Historical precedent (C227)Standard reactive aggregate (C441)Standard reactive aggregate (C441)Presumed to represent service conditions (C342 - withdrawn))Severe conditions to accelerate (C1260)Long period – “more reliable” (C1293)Long period more reliable (C1293)Quacks like a duck… so it must be… (C1567)
WWW. NRMCA.ORG
NRMCA Research – ASTM C1260
80%
90%
100%
50%
60%
70%
80%
nt L
ess
Tha
n
10%
20%
30%
40%
Per
cen
All (152)
CA (71)
0%
10%
0.00 0.10 0.20 0.30 0.40 0.50 0.60
Mortar Bar Expansion, %
FA (81)
154 U.S. aggregates tested by ASTM C 1260:73% expanded more than 0.1% (85% of sands)52% expanded more than 0.2% (65% of sands)
WWW. NRMCA.ORG
p ( )80% have been used in concrete for 10 years or longer
NRMCA - C1260 vs. C1293
0.180.20
ion,
0 120.140.16
te)
expa
nsi
0.080.100.12
93 (c
oncr
et
0 020.040.06
STM
C 1
29
0.000.02
0.0 0.2 0.4 0.6 0.8 1.0 1.2ASTM C 1260 (mortar) expansion %
AS
WWW. NRMCA.ORG
ASTM C 1260 (mortar) expansion, %
Project SpecPC alkali >0.6% can be used when
With slag cement effective alkali of blend does not exceed 0.6%M il bl lk li f t fl h bl d t t d 0 6%Max available alkali for cement-fly ash blend not to exceed 0.6%
Alkalinity measurements on fly ash or cement or combinationAggregates C295
When constituents are exceeded, aggregates are unacceptableAggregates C1260
Expansion > 0.08% at 16 days are unacceptableCoarse aggregate – C289Aggregates failing evaluation criteria can be used with prior field service recordsFly ash not permitted in concrete exposed to public view
Washington Metro Authority
WWW. NRMCA.ORG
g yParking garages
Washington Metro Spec ModifiedIf cement alkalis > 0.6%, test aggregates with proposed PCproposed PC
C1260 Expansion < 0.08 at 16 days
Test aggregate with proposed cementitiousmaterials
C1567 Expansion < 0.08 at 16 days
Washington Metro Authority Dulles Metrorail
WWW. NRMCA.ORG
Dulles Metrorail
FAA Spec
Modify C1260/C1567Modify C1260/C1567Aggregates in proportions proposed for useCementitious materials in proportionsp pSoak in potassium acetate for 28 days
Expansion < 0.10 at 28 days immersionExpansion 0.10 at 28 days immersion
WWW. NRMCA.ORG
Evaluation for FAA
ASTM C1567 - Mortar-Bar immersed in KA solution
0.15
0.20
CA1; 16% f ly ash
CA1; 22% f ly ash Aggregate blend:Coarse:Fine = 63:37
0.10
Cha
nge,
%
CA2; 16% f ly ash
CA2; 22% f ly ash
Coarse:Fine = 63:37
0.05Leng
th C
0.000 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
Days in Solution
WWW. NRMCA.ORG
Days in Solution
Actual SpecContractor shall pre-qualify aggregate supplierNon ASR aggregate shall be used for all concretegg gContractor shall test aggregate and concrete mixture frequently while building stockpiles and during pavingTesting at Contractor expenseIncrease time for C1260 to 28 daysProposed aggregate blend tested by C1567Proposed aggregate blend tested by C1567
Andrews Air Force Base
WWW. NRMCA.ORG
Andrews Air Force Base
Guidance on ASR Specifications
ACI 318 is silentN t dd d i ACI 301Not addressed in ACI 301
AIA MasterSpec marginally addresses ASRGenerally not addressed in private constructionGenerally not addressed in private construction
DOT requirements vary considerablyFederal specs vary considerablyFederal specs vary considerably
YES G id i d dYES – Guidance is neededFHWA/AASHTO ASTM C09 50 / C01 50
WWW. NRMCA.ORG
ASTM C09.50 / C01.50
Ideal ASR Specification
Determine reactivity of aggregatesS i d l l hi tService record or local historyTest results of aggregates (a reliable test)
preferably by aggregate supplier (ASTM C33)preferably by aggregate supplier (ASTM C33)
Determine if service conditions need mitigationMoistureCritical nature of structure
Establish mitigative measuresgService record or local historyTest to “accepted” criteria
WWW. NRMCA.ORG
Prescription based on best current understanding
AASHTO FHWA Standard
Evaluation of aggregateEvaluation of aggregateService RecordPetrographyPetrographyTest
ASTM C1260ASTM C1260ASTM C1293
Alkali carbonate addressed separately
WWW. NRMCA.ORG
AASHTO FHWA Standard
PerformancePerformanceC1293 - <0.04% at 2 yearsC1567 <0 10% at 14 days immersionC1567 - <0.10% at 14 days immersion
Complications if lithium is evaluated
WWW. NRMCA.ORG
AASHTO FHWA Standard
PrescriptivePrescriptiveDegree of reactivity – R0, R1, R2, R3Risk of ASR exposureRisk of ASR – exposure
Level 1 – Level 6Classification of structure riskClassification of structure – risk
S1, S2, S3, S4P ti L lPrevention Level
V, W, X, Y, Z, ZZC li ti if lithi i l t d
WWW. NRMCA.ORG
Complications if lithium is evaluated
AASHTO FHWA StandardPrescriptive – based on Prevention Level
Maximum alkali in concreteMaximum alkali in concrete5.0, 4.0, 3.0 lb/yd3
Quantities of SCMs varyQ yFly ash (CaO <18%, Na2Oe)Slag (Na2Oe < 1.0%)Silica Fume (Na Oe < 1 0%; varies based on PC alkali in concrete)Silica Fume (Na2Oe < 1.0%; varies based on PC alkali in concrete)
Adjust quantity of SCM based on PC alkalisLevel ZZLevel ZZ
SCM and concrete alkalis
WWW. NRMCA.ORG
AASHTO FHWA Standard
It’s a great startIt s a great start
Approving ASTM standard will be hardApproving ASTM standard will be hard
S ifi ti i kSpecification risksElevating prevention levelI ti ll ( li i t ti )Incorporating all (eliminate options)Tightening recommended limits
WWW. NRMCA.ORG