Forensics, forensic evidence, and continuing development of specifications and test methods

June 6, 2010D. Stephen LaneResearch Scientist

A partnership of the Virginia Department of Transportationand the University of Virginia since 1948

FORENSIC - DEFINED

• ASTM E30 – computer forensics: science of identifying, collecting, preserving, documenting, and analyzing evidence from computer systems networks and other electronic devices the results ofsystems, networks, and other electronic devices, the results of which may be relied upon in court.

• E30 – digital forensics: science of identifying, collecting, preserving, documenting, examining, and analyzing evidence from computer

t th lt f hi h b li d i tsystems, the results of which may be relied upon in court.

• Webster’s NC • forensic, adj: 1) belongs to, used in, or suitable to

courts of judicature or to public discussion and debate; 2) argumentative, rhetorical

forensic, n: 1) an argumentative exercise; 2) the art or study of argumentative discourse

6/10/2010 2

or study of argumentative discourse

ASTM PROCESS

Open discussion and debate which (hopefully) leads to agreement (perhaps grudging) and:agreement (perhaps grudging) and:

CONSENSUSCONSENSUSASTM: Subcommittee 2/3 affirmative

Main Committee 9/10 affirmative

Both cases – all negatives resolved:Withdrawn or found non-persuasive or not-related

supported by valid reasoning

6/10/2010 3

EVIDENCEEVIDENCE

Petrographic – field and test specimensOptical – reflected, transmitted light microscopySEM-EDSChemical – wet, XRF, spot/staining tests

Research Testing and Evaluations

Construction recordsConstruction recordsDatesCement source – compositionSCM? – nature, compositionpCement (cementitious) Content of concreteAggregate sources – petrographic reports, test records?

6/10/2010 4

I-64 CHARLOTTESVILLEMETABASALT COARSE AGGREGATEMETABASALT COARSE AGGREGATE

Built ca. 1972

Cem alk ~ 0.6% (?)

C t 335 k / 3Cem cont 335 kg/m3

alk load – 2 kg/m3

6/10/2010 5

I-64 METABASALT (GREENSTONE)

6/10/2010 6

I-95 RICHMONDNATURAL SAND & GRAVELNATURAL SAND & GRAVEL

6/10/2010 7

I-295 METARHYOLITE

6/10/2010 8

I 64 - GRANITE GNEISSI 64 VTRC B ilt 1974I 64 VTRC Built 1974

`1991

2010

6/10/2010 9

US 58 DANVILLE – GRANITIC GNEISS

Built 1957

Photo 2003Photo 2003

6/10/2010 10

TEST RESULTS (EARLY 1990’s)

Aggregate C1260* (14d) C1260 (28d)Aggregate C1260 (14d) C1260 (28d)Granitic gneiss (Charlottesville)

0.07 0.14( )Metabasalt 0.09 0.15Granitic gneiss (NC) 0 17 0 28Granitic gneiss (NC) 0.17 0.28Quartz sand 0.19 0.37Quartz gravel 0.32 0.49Metarhyolite 0.39 0.596/10/2010 11

y 0.39 0.59

* Then P 214

VDOT SPECIFICATION CHANGE 1991

• Difficulty distinguishing deleteriously reactive from non-deleterious aggregates even with AMBT

• Economic downturn, department downsizing – did not want to embark on a massive program of aggregate testing

• Solution: Focus on cementitious materials - if cement alkali content exceeds 0.40% Na2O-eq require (1.3-1.5 kg/m3)– Class F fly ash (15%), y ( ),– slag cement (35-50%) – or silica fume (7%)

• Research to refine developed sliding scale of SCM based on• Research to refine – developed sliding scale of SCM based on cement alkali content using borosilicate glass testing

• Modified recently with focus on limiting permeability

6/10/2010 12

C 1260 ACCELERATED MORTAR BAR TEST CRITERIACRITERIA

Oberholster & Davies (1986): 12d NaOH immersion lower limit for deleterious aggregate (hornfels) 0 11%lower limit for deleterious aggregate (hornfels) 0.11%

Davies & Oberholster (1987): 12d NaOH immersion l li it f d l t i t SCMlower limit for deleterious aggregate-SCM combinations (graywacke-hornfels) 0.10%(?)

Hooton & Rogers (1989, 1992)

H t (1991)Hooton (1991)

Fournier & Berube (1991)

6/10/2010 13

Fournier & Berube (1991)

AMBT CRITERIAAMBT CRITERIAC 1260-94

< 0.10% 14d NaOH immersion – innocuous** some granitic gneisses and metabasalts expand less – field performance of these should be examined. Absent field performance data – use mitigative measures(C 33 - …innocuous in most cases)

> 0.20% - indicative of potentially deleterious expansion> 0.20% indicative of potentially deleterious expansion

Between 0.10 and 0.20% - both innocuous and potentially deleteriousdeleteriousDevelop supplemental information: petrographic examination of aggregate and bars; examine field performance. Continue test through 28 days

6/10/2010 14

through 28 days

AMBT CRITERIA

CSA A23.2-27A (2004)( )<0.150% 14d immersion – innocuous*

*except 0.100% for siliceous limestones>0.150% 14d immersion – “highly reactive”

S OAASHTO<= 0.10% 14d immersion – non-reactive>0 10% <=0 30% moderately reactive>0.10%, <=0.30% moderately reactive>0.30%, <=0.45% highly reactive>0.45% - very highly reactive

6/10/2010 15

0.45% very highly reactive

AMBT CRITERIA

SHRP (Stark et al., 1993): 14d NaOH immersion ( , )expansion limit of 0.080%

Lenke & Malvar (2009)>0.06% 14d or 0.13% 28d

6/10/2010 16

AMBT CRITERIAAMBT CRITERIA

False Negatives versus False PositivesFalse Negatives versus False Positives – what is the risk, to whom does it fall, and how do we manage it?

Stark et al and Lenke & Malvar adopted the approach of setting the limit to include all with known field reactivity.

Strang (2000) reports that New Brunswick DOT decided not to use AMBT because of high number of false positives coupled with a decision not to use reactive aggregates

If in a specification compromise is reached setting the limit higher how are known exceptions addressed?

6/10/2010 17

limit higher, how are known exceptions addressed?

C 1293 –CONCRETE PRISM TESTCriteriaCriteria

C 1293 X1 2 “Work has been reported from which it may beX1.2 - Work has been reported from which it may be inferred that an aggregate might reasonably be classified as potentially deleteriously reactive…” if 1y expansion => 0.04%(Grattan-Bellew, 1983; CSA A23.2-27A-00)

“Generally considered to be ‘Most Reliable’ ”(repeated often enough it becomes gospel)(repeated often enough it becomes gospel)

VA reactive metabasalt & granitic gneiss that expand

6/10/2010 18<0.10% in C 1260 did exceed 0.04% at 1y in C 1293

C 1293 –CONCRETE PRISM TEST CriteriaCriteria

However:

N. Whiting (1999) reported reactive sands containing opaline shale particles from Minnesota that did not

d th 0 04% li itexceed the 0.04% limit.

Strang (2000) reports that New Brunswick DOT definesStrang (2000) reports that New Brunswick DOT defines reactive aggregates as those with CPT (CSA 23.2-14A) results > 0.035% at 2y

False Negatives versus False Positives – what is the risk, to whom does it fall, and how do we

6/10/2010 19

manage it?

CPT (C 1293)FOR EVALUATING MITIGATION WITH SCMsFOR EVALUATING MITIGATION WITH SCMs

C 1293X1.3 - It is reasonable to conclude that SCM amount is at least the minimum needed when expansion is <0 04% 2Y<0.04% 2Y

6/10/2010 20

AMBT (C 1567)FOR EVALUATING MITIGATION WITH SCMsFOR EVALUATING MITIGATION WITH SCMs

C 1567 X1.1.1 – There is good agreement in the published literature for the following expansion limits:< 0 10% 14d likely to produce acceptable expansion< 0.10% 14d – likely to produce acceptable expansion in CPT and low risk of deleterious expansion in field concrete

X1.1.2 – Combinations that expand >0.10% are indicative of potentially deleterious expansion. yHowever, this potential should be confirmed by testing the combination in concrete (CPT)

6/10/2010 21

AMBT (C 1567)FOR EVALUATING MITIGATION WITH SCMs

Thomas et al. (2007) provide support for the <0.10% 14d among several

i AMBT lt ithways comparing AMBT results with CPT 2y results. Only 7% failure (passed AMBT, failed CPT) (13 of 182)

AMBT 14 results

An alternative way of viewingThe data is 17% of cases which passed the AMBT were incorrect

CPT 2Y <= 0.10% > 0.10%

<=0.04% 62 29passed the AMBT were incorrect (failed CPT) (13 of 75).

Also worth a detailed look at materials

> 0.04% 13 78

involved

Are exceptions to the “accepted” rule

6/10/2010 22

simple aberrations to be ignored or are they trying to tell us something?

AMBT and SCMs

Thomas et al (2007) cite favorable comparisons of AMBT tests with field f t t it ith 14 d i li itperformance to support its use with a 14-day expansion limit

Lower Notch Dam, Ontario (Stirrup et al, 1983)Experimental Pavement Picton OntarioExperimental Pavement, Picton, OntarioLackawanna Valley Industrial Highway (Thomson, 2000)

AMBT is touted because it permits the testing of the SCM with the p gaggregate. However, the SCM doesn’t react with the aggregate, it interacts with the cement and the chemistries of the SCM and cement dictate the pore solution alkalinity which reacts with the aggregate

The AMBT washes this away – Perhaps there is still some untility in borosilicate glass teting

6/10/2010 23

Borosilicate Glass TestsLower Notch Dam L (1999)

0.50%

0.60%

0.70%

ge

1.030

Lower Notch Dam

Stirrup et al (1983)Lane (1999)

PC

0.10%

0.20%

0.30%

0.40%

Leng

th c

han 0.

920.750.6

0 25%

0.30%

0.00%

0 14 28 56 90 180 365

Age (days)

0.10%

0.15%

0.20%

0.25%

Leng

th c

hang

e

15% FA115% FA520% FA525% FA125% FA225% FA325% FA435%

0.00%

0.05%

0 14 28 56 90 180 365

Age (days)

35% FA1

6/10/2010 24

PC 0.75+FA

AMBT, CPT, SCMs and LIMITS

Stokes et al. (2008) looking at much the same data as ( ) gThomas et al. (2007) concluded that the 2y CPT “fails to predict expansion of companion specimens in outdoor exposure to a considerable degree the 2youtdoor exposure to a considerable degree…the 2y CPT is simply not worth the wait”.

They suggest a 28d AMBT limit of 0.10%

Lenke & Malvar (2009) again suggest 0.06% 14d or 0.13% 28d. Recommend against using CPT

6/10/2010 25

PREVENTIVE MEASURES – ALKALI LOADING

Danville granitic gneiss AMBT 0.17%AAHSTO RP– “Moderately Reactive”

For S3 (40-75Y) Prevention LevelsX 2 4 kg/m3 Na Oeq PCCX – 2.4 kg/m3 Na2Oeq PCCY – 1.8 kg/m3 Na2Oeq PCC (exp to alkali)

Public works structure in service ~ 8Y (1984)Public works structure in service 8Y (1984)Extensive cracking due to ASRLow-alkali cement was specifiedFrom paste & w/c estimates likely 335 kg/m3p y gEstimated alkali load @ 0.60% - 2 kg/m3

How well-grounded are the alkali loading limits?

6/10/2010 26

g g

PREVENTIVE MEASURES– SCM AMOUNTS

VA Metarhyolite AMBT 0.39, CPT 0.15%AASHTO RP “Hi hl R i ”AASHTO RP- “Highly Reactive”

For S3 (40-75Y) Prevention LevelsY 25% LLFA 50% slagY – 25% LLFA, 50% slagZ - 35% LLFA, 65% slag (exp to alkali)

For S4 (> 75Y) Prevention LevelsZ - 35% LLFA 65% slagZ - 35% LLFA, 65% slag

ZZ - 35% LLFA, 65% slag + limit PC load to 1.8 kg/m3 Na2Oeq Testing options:AMBT 20% LLFA, 40% slag; CPT 15% LLFA, 35% slag, g; , g

Dichotomy between test and prescription for materials that we have the most experience and confidence in – how does test relate to service life embedded in prescription?

6/10/2010 27

relate to service life embedded in prescription?

C 1260, C 1567 and C 1293 LIMITATIONS

Written specifically to test a single aggregate at a time p y g gg g(in CPT, the aggregate under test is combined with a non-reactive coarse or fine aggregate)

Some now practice testing combinations of coarse and fine job aggregates in the same AMBT or CPT testand fine job aggregates in the same AMBT or CPT test

Is this practice well-grounded, or simply convenient?

6/10/2010 28

SPECIFICATIONS and TEST METHODS

Should specifications apply test methods outside the bounds of the h d’ d li i i ?method’s stated limitations?

This is bothersome when done by outside agencies prompting requests that ASTM take actionrequests that ASTM take action

Within ASTM, hopefully, those limitations will be considered when crafting specificationscrafting specifications

The AMBTs require re-grading of fine aggregate into a standard grading – a practice that can bias the sample’s composition.grading a practice that can bias the sample s composition. The mmethod goes into great detail to avoid biasing coarse aggregate samples. Either the test method should be changed or the specification written to avoid this problem.

6/10/2010 29

CLOSURE

Open discussion and debate of the issues is a pnecessary step in the process that leads a body to consensus

There are a number of issues to be resolved – many more than were mentioned here

What is the risk, to whom does it fall, and how should we manage it?g

So, with that, CONFRONT AND ENGAGE

6/10/2010 30