.SC1r American SocietyiiFII .. of Civil Engineers180I ALEXANDER BELL DRIVERESTON, VIRGINIA 20191-4400

EDITEDBYAtorod Azizinamini

David DarwinCatherine French

July 13-18, 1997Kona, Hawaii

SPONSOREDBYUnited Engineering Foundation, Inc.

PROCEEDINGS

First International Conference

HIGH STRENGTH CONCRETE

Copyright @ 1999 by the American Society of Civil Engineers, All Rights Reserved.Library of Congress Catalog Card No: 99-17899 ISBN 0-7844-0419-4Manufactured in the United States of America.

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Engineering Foundation Conference on High Strength Concrete (1S!: 1997: Kona, Hawaii)High strength concrete: first international conference: proceedings, July 13-18, 1997,

Kona, Hawaii / sponsored by United Engineering Foundation, Inc.; edited by AtorodAzizinamini, David Darwin, Catherine French.

p. cm.Includes bibliographical references.ISBN 0-7844-0419-41. High strength concrete-Congresses. 2. Concrete construction-Congresses.

I.Azizinamini, Atorod. II. Darwin, David. III. French, Catherine (Catherine E.)IV. United Engineering Foundation (U.S.) V. Title.TA439.E474 1997624.1'834-dc21 99-17899

CIP

Library of Congress Cataloging-in-Publication Data

Abstract: This proceedings, High Strength Concrete, consists of papers presented at thefirst Engineering Foundation Conference on High Strength Concrete, held July 13-18, 1997,in Kona, Hawaii. The conference brought together a group of individuals known for theircontributions to high strength concrete (HSC); from material aspects to applications in thefield. Since the 1980s, intense research activities have been conducted to resolve designissues related to the use of HSC. These papers explore such issues as the behavior ofinterior beam-and column subassemblages in a reinforced concrete frame, ductility andstrength of HSC columns, shear strength of HSC beams, seismic behavior of prestressedconcrete beam-column joints, crack growth and cyclic loads, and thermal performance ofHSC.

High Strength Concrete: Design Issues in the Canadian Code 582Dents Mitchell

CodesOn Extending ACI318 to High Strength Concrete 5S4

Mohamed A. At. and Richard N. White

Provisions in U.S. Codes Related to nigh Strength Concrete 568S.K.Ghosh

VII

Use of CFRP Composites with High Strength Concrete in Bridges .......•........................ 391Nabil F Grace. GCO'1lCAbdel-Sayed, and Michael S. Ledesma

Cracking in High Strength Concrete at Early Ages ...........•......•.••.................................... 401TorArne Hammer. Erik J. Sellevold, and 0yvind Bjontegaard

Studying Initiation and Growth of Shear Cracks in Reinforced ConcreteBeams lsing Full-Field Digital Imaging.. _ .4 12

Daniel C Jansen. Sokhwan Choi, and Surendra P. Shah

Penetration Resistance Tests on High Strength Concrete ........•...............•....•..........•....•.. ·U5Sergio \.1 R Lopes and Miguel C.S. Ncpomuccno

High Strength Concrete from Low Water Demand Cemenl. ....•.......•............................ .434J Moreno. Sh r Babaev, N.F Bashlykov, C. Eberhardt. B.E. Yudovich. andV.R Falikrnan

Crack Gro» tb in Four Concretes under Monotonic or Cyclic Splitting Load .444Kal Duan and Jan G.M. van Mier

Fundamental Aspects of Mechanical Behavior of HS/HPC: The EuropeanApproach 457

Jan G.M van Mier

Comparative 'tudy of High Strength Concrete Fracture Uniaxial andTriaxial Loading _ 470

Kamran M Nemati and Paulo J.M. Monteiro

Fiber Reinforced Higb Strength Concrete Beams in Shear .480Kelvan xoghabai, Thomas 010fs50n, and Jonas Gustafsson

High Performance :\Ju!timodal Fiber Reinforced Cement Composites(HP;\fFRCC) 494

P ROSSI

~1aterial Aspects of High Performance Concrete 50..Surendra P Shah

The L e of High Reactiv it) Mctakaolin in Higb Performance Concrete .517\1 D.A Thomas. K.A Gruber. and R.D. Hooton

Thermal Performance of Concretes Including High Strength Concrete S31J.A. Tinker

Higb Strengtb Phosphate Cement Using Industrial By-Product Ashes S42Arun S Wagh. Seung- Young Jeong, and Dileep Singh

·us

As a way of estimating the "in situ" strength for high strength concrete, sometechniques, previously used in normal strength concrete, have been adapted and

The interest of high strength concrete has increased considerably in the last lewyears. Several research works on this subject have contributed to a betterunderstanding of the material properties and mechanical behavior in structuralelements of high strength concrete.

One subject, which needs some investigation as far as the use of high strengthconcrete In building construction is concerned, is the prediction of "in situ' concretestrength. It is known that the strength measured on standard specimens, at 28 daysand cured in standard conditions, only gives the potential value of the concretestrength, which is useful for quality control purposes and for checking theacceptability of the concrete as it is produced (1. 2). However, this referencestrength is normally achieved by the real structure at ages much higher than 28days, depending on various parameters, mostly associated with curing conditions.On the other hand it is often necessary to know the strength of concrete before 28days to determine when the forms can be disassembled or to know the structurepeliormance at certain age.

INTRODUCTION

The aim of the investigation described here is to verify the applicability ofpenetration resistance tests on high strength concrete as a way of estimating itscompressive strength "in situ". A relationship between compressive strength of agiven concrete and its resistance to penetration by a steel probe fired into theconcrete surface is presented to a compressive strength range varying from 50 MPato 90 MPa using an alternative firing apparatus to the standard apparatus WindsorProbe Test System.

ABSTRACT

Miguel C. S. NepomucenoLecturerUniversity of Beira InteriorDep. of Civil Eng.6200 Covilha - Portugal

Sergio M. R. LopesAssistant ProfessorUniversity of CoimbraDep. of Civil Eng. - FCTUC3049 Coimbra Codex - Portugal

PENETRATION RESISTANCE TESTS ONHIGH STRENGTH CONCRETE

The way of delivering the energy to the probe by the Altemative Firing Apparatushas little difference from the WPT Systempreviously mentioned. Both systems usea powder cartridge and probes, but while in the first apparatus I;NPT System)detonation resultant energy of the powder cartridge is transmitted directly to theprobe, which Is accelerated and projected into the concrete surface, In theAltemative FIringApparatus this energy Is transmittedto a piston, which is projectedin high velocity againstlhe probe, like a hammer, thrust In the probe by the Impact.

Alternative Firing Apparatus

A test apparatus, designed for penetration resistance measurements, using aspecial probe and standardized powder charge, was developed In the USA duringthe 1960s' and is knownas Windsor ProbeTest System and covered by the ASTMStandards (ASTM-C803-90) <a). In Europe, similar standards are the BritishStandards (BS 1881:Part 207: 1992) (i). This system allows the use of two kinds ofprobes: the silver colored probe, to use In concrete wllh natural aggregate; and thegold colored probe, to use with lightweight concrete. Two different power levels arealso posslole, using the same power load, by an adjustment In the instrument: thestandard power and low power. For the purposeof this study, It was decided to usethe silver colored probe (of hardened steel alloy with 6.35 mm diameter, 79.5 mmlength, a blunt conical end and a plastic guide) associatedwith the standard power.

Probes were fired into concrete, using the driver unit, and the exposed length wasmeasured Individually, by using a rectangular plate, placed over probe andpressured against the concrete by a knurted spring-nut, and a measuring capthreaded on top of probe. The distancewas measured from top of cap to plate withthe micrometer depth gauge.

Windsor Probe Test System

TEST EQUIPMENT

In an attempt to use Windsor Probe Test System in high strength concrete,pertormed by the authors, it was found that the available probes and/or the powerlevel are unsuitable; probes didn't penetrate the concrete surtace. It means thatprobably a new probe and/or a new power level has to be provided by manufacturerin order to be possible its use in highstrength concrete.

On the present investigationthe possibilityof usingan altemative firing apparatus tothe traditionalWindsor Probe Test Systemwas evaluated for the range of concretecompressive strength varying from 50 MPa to 90 MPa. A previous study, comparingthe reliability of both apparatus, Is also presented for the range of concretecompressive strength up to 50 MPa.

used. One of those techniques consists on calibrating a relationship between thecompressive strength of a given concreteand its resistanceto penetration by a steelprobe fired into the concrete surtace. This test, generally known as Windsor ProbeTest System, has only shown its applicability in concretes in which strengths are nomore than 50 MPa (measuredIn cubes of 150mm).

HIGH STRENGTH CONCRETE426

The specimens were cured togetherat approximately 1~C and relative humidity of65%.All the tests were performedat 28 days age lor each group of specimens and,at the time of testing, the specimencondition was dry.

Fivedifferentmix proportions, correspondingto five different classes of compressionstrength, were produced in order to obtain five sets of specimens, each onecomprisinga 750x550x170mm slab and 4 cubes of 150 mm, all obtained by usingmetallic moulds. Each slab was constructed to withstand S tests of WPT Systemand, at least, 12 tests by the Altemative Firing Apparatus. The dimensions weredetermined in order to obtain, lor standard power, the recommended edgedistances, member thickness and minimum distances between tests, given byASTM standards (a), to prevent splitting of the member under test, structuralcrackingand also to avoid overlapping01 zones 01 inlluence.

The mix proportions were established In order to fix the maximum number ofparameters. Therefore, the Faury modules of fineness remained exactly the sameand the workability of fresh concrete, measured by slump test, was fixed between80 mm and 120 mm. Also the operations of mixing and compacting (type andfrequency)were kept constant In all the cast specimens.

The coarse aggregates were crushed rock from granite with the maximumdimensionof 25.4 mm and a Mohs' hardness scale level 7. The fine aggregate wasa natural sand from the river.

In a previous study on normal strength concrete, performed by the authors ~), thepossibility of using an altemative firing apparatus to the traditional Windsor ProbeTest Systemwas evaluated.

Previous Studies on Normal Strength Concrete

PROCEDURE

In both cases the exposed length was directly measured, by using a depth gauge,relativelyto the original surface of the concrete.

For high strength concrete, the probe was madeof steel alloy with 4.5 mm diameterand 42.0 mm length, a conical end and a plastic guide. The powder charge waslevel7.

The probe used for normal strength concrete was made of steel alloy wiltl 4.5 mmdiameterand 52.0 mm length,a conicalend and a plastic guide. The powder chargewas levelS.

TheAltemative FiringApparatusenables the control of the energy level, delivered tothe probe by the driver, as well as different dimensions and geometries for theprobe.

427HIGH STRENGTH CONCRETE

I g h i iSand (ko) 802 755 660 549 422

Coarse agg.l (kg) 241 306 399 401 503Coarse aoo.2(ko) 730 708 670 732 716

Cement (kg) 400 425 485 535 600Admixture (I) 10.0 10.6 12.1 13.4 15.0Water!l) 142 140 145 145 157WIC 0.36 0.33 0.30 0.27 0.26

Table 1 - Basicmix proportionsper cubic meier

For concrete mix proportions a water/cement relationship based on weight varyingfrom 0.36 to 0.26 was considered in order to obtain the compresstve strengthbetween 50 MPa and 90 MPa. The cement quantity varied from 400 kg to 600 kgper cubic meter and the workability,measuredby slump lest, remained between 60and 100mm. The live basic mix proportionsare presentedon Table 1.

The fine aggregate is nalural sand from the river with a fineness modulus about 3.5and the coarse aggregates is a crushed rock from granite supplied with twogradations, classified as coarse aggregate 1 and coarse aggregate 2, with amaximum dimensionof 25.4 mmand a Mohs' hardnessscale level 7.

As for normal strength concrete, mix proportions were determined in order to keepconstant the maximum number of parameters,such as, Faury modules of fineness,workability and the operationsof mixing and compacting.

Among the types of cement available in Portugal, a normal portland cement, type I,class 42.5R, classified accordingto the PortugueseNormsNP2064, was chosen.

Considering the desirable level of strength and concrete producing conditions, asuperplasticizer was selected which was highly concentrated and based onsynthetic resins without air-enlraining agents. This superplastiCizerenabled a waterreduction of about 22%, keeping the same workability.

Five different mix proportionswere producedwith constituent materials of the samecharacteristics, which allows five different classes of compression strength between50 MPa and 90 MPa. From each batch 3 standardcubes of 150mm were producedas well as one prismaticslab with dimensions550x50Ox170mm.

Studies on High Strength Concrete

The Altemative Firing Apparatus was studied in order to find out its suitability andreliability for normal strength concretes and good results were obtained. Thereforethe same study was applied to high strength concrete which is explained in thispaper.

HIGH STRENGTH CONCRETE428

The results presented on the above Table 2 were analyzed and plotted individuallyfor both apparatus used, as shown in Fig. 1 and Fig. 2.

a b c d eCubes of 150 mm fem[MPa] 17.70 23.80 37.43 42.33 53.18cured at 1211C, (4) (3) (4) (4) (4)R.H. 65%, tested SOX [MPa) 0.47 2.62 0.87 1.74 1.94drv, at 28 days CVI%] 2.66 11.00 2.32 4.11 3.65Penetration Test E (mm] 39.14 43.59 51.52 52.97 54.70Resistance by (6) (6) (6) (6) (5)WPT System SOX [mmJ 3.34 1.54 1.65 1.64 2.34

CV 1%1 8.53 3.53 3.20 3.10 4.27Penetration Test E [mm] 16.40 19.82 24.53 25.08 26.92Resistance by (17) (13) (12) (13) (17)the Altemative SOX [mmJ 1.40 0.85 1.65 0.80 1.13Firina Apparatus CVI%l 8.54 4.29 6.73 3.19 4.20

Table 2 - Results obtained for normal strength concrete(Number in parenthesis shows the number of measurements).

E ts the mean value of the exposure length.femis the mean value of compressive strength on standard cubes.

Both apparatus were simultaneously used on the same concrete and the obtainedexperimental results are shown In Table 2.

Previous Studies on Normal Strength Concrete

ANALYSIS OF RESULTS

All specimens (slab and cubes) were cured in water at controlled temperature of2()!!C ± 2!!C and ali the tests were performed at 28 days. For each batch, 3 cubeswere tested for compression strength and penetration resistance tests applied onconcrete slab surface by using the "Altematlve Firing Apparatus". All specimenswere wet at the time of testing.

429HIGH STRENGTH CONCRETE

Fig. 2 - Results obtained from the Altemative Firing Apparatus lor normal strengthconcrete.

60~LTERN~ TIVE FIRINQ AEP~BAI!.!S:;

0)c(Il.... ~

50- asVIa.~~.2j E (iii) tem=·37.5 + 3.2101 • E!!! 0 .co ,a. -_ \,/<;E VI8~- a 300(Il"e ,,'.:2~ """as c> as 20 (Iv) fem= 3.1772 • EXP(0.1 02926 • E)c-as VI(Il C~ 0

1016 18 20 22 24 26 28

Mean value of exposure length E [mm)

Fig. 1- Results obtained from the Windsor Probe Test for normal strength concrete.

Mean value of exposure length E [mm)

45 555040104----.----~---r----~--,_--~----,_--~

(if) fem = 1.31038 • EXP (0.06627S·E)

(i) tern = - 64.929 + 2.06301 • E

\_,,///~/'

•WINDSOR PROBE TEST SYSTEM

HIGH STRENGTH CONCRETE430

Fig. 3 - Results obtained Irom the Altemative Firing Apparatus for high strengthConcrete.

2117 18 19 20Mean value 01exposure length E [mm)

16

£;OJa5 ALTERNATIVE FIRING APPARATUS.:::(i 80"'a.~~._ ~'"~ 5a. - 70E <Ii8~00Q)'O.2 (ij 60CIl '0 (v) 'em:: - 81.5344 + 8.02508 • E> c::~~Q) c~ 0 50

The obtained results (Table 3) were analyzed and plotted as shown in Fig. 3.

f g h I ICubes of 150 rnm '0m [MPa) 49.12 58.27 67.77 78.35 81.94cured in water (3) (3) (3) (3) (3)at 20 !lC. tested SOX [MPal 1.02 0.82 1.56 2.17 1.12wet at 28 days CV(%) 2.08 1.41 2.30 2.77 1.37Penetration Test E [mm) 16.32 17.48 18.49 20.31 20.00Resistance by (10) (9) (10) (7) (8)the Altemative SOX (mm} 0.92 0.97 1.64 0.56 0.87Flrinq Apparatus CV (%1 5.64 5.50 8.87 2.76 4.35

Table 3 - Resulls obtained for high strenglh concrete.(Number In parenthesis shows the number of measurements).

E is the mean value 01the exposure length.lem Is the mean value of compressive strength on standard cubes.

The experimental study on high strength concrete lead to the tolowing resultspresented on Table 3.

Studies on High Strength Concrete

411IIiGII SIRE~(jTIICO:\CRETE

(1) - Yuan, Robert L.; Ragab, Mostala; Hill, Robert E.; Cook, James E. - Evaluationof Core Strength in High-StrengthConcrete, Concrete International, Vol. 13. pp 30to 34, May 1991.(2) - Price, W. F.; Hynes. J. P. - In-situ Strength Testing of High Strength Concrete.Magazine of Concrete Research,48, N!l176, pp 189 to 197,Sept 1996.

REFERENCES

E - is themean value of the exposure length.fem - Is the mean valueof compressivestrength on standard cubes.SDX - is the Standarddeviation.CV - is the Coefficient of variation.R.H. - is the relativehumidity.

NOTATION

The authors would like to thank the University of Beira Interior for providing thelaboratory conditions and to Mr. Armando M. C. Trindade for his preciouscollaboration in the laboratoryworks.

They would like to extend their thanks to the University of Coimbra and JNICTresearch project ref. PBIC/C/CEG/2384/95.

ACKNOWLEDGMENTS

Other aspect that cannot be ignored is the higher cost of WPT System equipmentand probes in Europewhencomparedwith the Altemative FiringApparatus.

It is clear and mentioned by different authors (Q. n that. as most other non­destructive tests. aggregate characteristics and other factors may have aconsiderable influenceon the results and, therefore, the validity of calibration tableshas to be carefully analyzed for each Situation.So. the results presented on Fig. 1.Fig. 2 and Fig.3 are valid for the establishedconditionsof this investigation.

The main physical limitation of penetration resistance tests is the surface damageand the danger of splitting of members,which limits the zones of testing. However. itwas found that the Altemative Firing Apparatus causes less damage than WPTSystem. Consequently,minor distancesbetweenprobes are possible.

Penetration resistance tests applied to high strength concrete, using the AltemativeFiring Apparatus has shown a linear correlation, Fig. 3. which probably can beimpute to more closenessbetween cementpaste and aggregate strength.

The results obtained for the range of normal strength concrete, Fig. 1 and Fig. 2,showed that the Altemative Firing Apparatus could be a suitable mean for theassessment of "in-situ· strength, and gives a good agreement when compared toWindsor Probe Test System @. When testing high strength concrete (Fig. 3), theAltemative Firing Apparatus appears to be particularly useful since the resultsobtained so far are very consistent.

CONCLUSIONS

HIGH STRENGTH CONCRETE432

(3) - ASTM Ca03-90. StandardTest Methodfor PenetrationResistanceof HardenedConcrete.American Society for Testing and Materials.(4) - BS 1881: Part 207: 1992 - Recommendationsfor the assessment of concretestrength by near-to-surfacetests. BritishStandards Institution, London.(5) - Lopes, Sergio; Nepomuceno, Miguel - A Comparative Study of PenetrationResistanceApparatus on Concrete, ICCEJ4,Hawaii,Ju11997.(6) - Bungey, J. H. - Testing by Penetration Resistance - Concrete, Vol. 15, Nil 1,Jan. 1981, pp 30 to 32.(7) - Bungey, J. H.; Millard, S. G. - Testing of Concrete in Structures, 3 ed.,Chapman& Hall, London - UK., 1996.

433HIGH STRENGTH CONCRETE

ISBN 0-7844-0419-4