Monitoring Stiffening Behavior of Conventional Concrete (CC) and SCC

Using Ultrasonic Pulse Velocityby

X. Wang, P. Taylor, K. Wang, M. Lim

Objectives• Assess ultrasonic pulse velocity applications to

observe concrete stiffening process• Correlate features of ultrasonic compression

wave (P-wave) development to set time and formwork pressure decay

• Provide an insight on surfacing, jointing, and formwork removal of concrete

• Hydration relatedStiffening Process

Stiffening Process• What does it affect?

– Workability:• Hydration• Thixotropy• Loss effectiveness of admixtures

– Formwork pressure• Filling rate

– Jointing• Saw cutting window

Materials• Aggregates

Aggregates in the Research TypeNominal

Maximum Agg. Size, in.

Absorption, % Fineness Modulus

Specific Gravity

Coarse Aggregate

CC-a Limestone 1 0.63 - 2.68CC-b Limestone ¾ 0.77 - 2.67SCC-a Limestone ¾ 1.3 - 2.66SCC-b Limestone ½ 1.3 - 2.66SCC-c Limestone 3/8 1.3 - 2.66

Fine Aggregate

CC-a & CC-b River sand - 1.74 2.84 2.65

CC-b LWA Expanded shale - 16@72hrs 3.55 0.93SCC River sand - 0.5 2.62 2.62

Mixture Proportions• CC

– CC-a: Seven mixtures with two slag types (grade 100 and 120) at 20%, 35%, and 50% replacement level of cement by weight

– CC-b: Eight mixtures with a Class F fly ash at 20% replacement level, which also contain lightweight fine aggregate, integral waterproofer (IWP), shrinkage reducing admixture (SRA), water reducer (WR), and air entraining admixture (AEA).

Mixture Proportions

Mixture Proportions• SCC: based on ACI and ICAR proportioning

methods– Three control mixes (CC): one for each size– 12 mixes designed for cast-in-place bridge

construction applications, made with different aggregate sizes (¾”, ½”, and 3/8”) and different cementitious materials including ground limestone

Mix ProportionsC I,II SCM LD CA FA Water HRWR VMA AEA

Ib/cy Ib/cy Ib/cy Ib/cy Ib/cy Ib/cy oz/cwt oz/cwt oz/cwt T50 (s) Tf inal (s) D (in.) VSI ∆D (in.) ∆H (in.)

CC Control 1 3/4" Limestone 497 166 0 1674 1177 285 0.0 0 0.6 N/A N/A N/A N/A N/A N/A

CC Control 2 1/2" Limestone 591 197 0 1485 1173 315 0.0 0 0.8 N/A N/A N/A N/A N/A N/A

CC Control 3 3/8" Limestone 572 191 0 1350 1356 305 0.0 0 1.5 N/A N/A N/A N/A N/A N/A

SCC-a-C 3/4" Limestone 568 189 0 1518 1242 280 8.0 0 0.8 <2 6.8 27.75 0 0.63 0.56

SCC-a-F 3/4" Limestone 568 189 0 1518 1242 280 8.0 2 0.8 <2 7.8 28.75 1 1.00 0.44

SCC-a-S 3/4" Limestone 539 231 0 1530 1252 280 8.0 2 0.8 2 6.2 29.13 0.5 0.13 0.38

SCC-a-FLD 3/4" Limestone 488 150 106 1518 1242 280 12.0 0 1.5 1.3 7 27.50 0.5 1.75 0.44

SCC-c-C 3/8" Limestone 587 196 0 1334 1334 305 11.0 0 1.3 <2 6.8 23.63 0 1.00 0.25

SCC-c-F 3/8" Limestone 587 196 0 1334 1334 305 10.5 3 1.5 <2 7.6 27.50 0 0.75 0.31

SCC-c-S 3/8" Limestone 558 239 0 1345 1345 305 12.0 0 1.5 2.7 9.5 27.00 0 0.50 0.25

SCC-c-FLD 3/8" Limestone 504 155 116 1334 1334 305 11.0 0 1.5 1.7 8.9 27.25 0 0.75 0.50

SCC-b-C 1/2" Limestone 535 178 0 1462 1297 295 8.0 0 1.0 <2 6.8 23.63 0 0.88 0.31

SCC-b-F 1/2" Limestone 535 178 0 1462 1297 295 6.0 2 1.5 <2 7.1 24.25 0 1.00 0.25

SCC-b-S 1/2" Limestone 525 217 0 1474 1307 295 8.0 0 1.5 <2 6.8 23.50 0 1.00 0.69

SCC-b-FLD 1/2" Limestone 460 141 106 1462 1297 295 6.0 0 1.5 <2 8.3 24.75 0 0.25 0.25

C: Class C fly ash a: 3/4" NMSA FLD: Class F fly ash and limestone dust VSI: visual stability indexF: Class F fly ash b: 1/2" NMSA VMA: vicosity modified admixture AEA: Air entraining admixtureS: slag cement c: 3/8" NMSA HRWR: High range water reducer

Mixture Identification Fresh SCC PropertiesMixture Design

ID

NM

AS Slump Flow J-Ring

Test Methods• ASTM C403 – penetration resistance • Formwork Pressure-ISU sacrificial formwork

– Flush diaphragm pressure sensor– Loading rate of 6 in/min (9 m/h)– Constant room temperature (72˚F)– Applied pressure up to 30 psi to simulate

30 feet concrete

Test Methods• Ultrasonic P-wave velocity measurement

– Testing on 4 by 8 in. cylinder up to 1000 mins– Transducer central frequency: 54 kHz– Constant room temperature (72˚F)– Wave path length: 0.65 feet (7.8 inches)

Ultrasonic Wave Propagation• Ultrasonic Pulse Velocity:

– A stress wave propagation method that involves measurement of the travel time of compression wave pulse over a known path length

• Biot’s theory– The propagation of elastic waves in a porous elastic

solid saturated with a compressive viscous fluid• Longitudinal (compression) waves: related to dynamic

modulus of elasticity, Poisson’s ratio, and density• Transverse (shear) waves• Surface (Rayleigh) waves

P-Wave (Vp) Transmission• Ultrasonic pulse velocity (UPV) device

– Commercial device: Proceq Pundit Lab plus– Vp = L/tp (length of the straight-wave-path through

the specimen/travel time of the ultrasonic pulse)

P-Wave (Vp) Transmission• Ultrasonic pulse velocity (UPV) device

– Commercial device: Proceq Pundit Lab plus– Vp = L/tp (length of the straight-wave-path through

the specimen/travel time of the ultrasonic pulse)

• mixes

DiscussionInitial Set Time

Results Summary

C Ash mixes

Conclusion• P-wave test can be used to monitor the

stiffening process of various concrete mixtures• Set time and formwork pressure decay of

concrete are clearly related to P-wave development

• Potential to provide an insight on surfacing, jointing, and formwork removal of concrete– Planning to correlate with saw-cutting window of

pavements in a forthcoming study