t4
DIRTOIS
UNIVERSITE
Eric WRQUIN - Professorin Civil Engineering
Artois UniverciQ:- Bdthune- France
(LGCgE)
LABOMTOIRE GENIE CIWL et GEO-ENVIRONNEMENT
..Influence of Mix Design and Technology on
Report on the PhD thesis entitled
Mechanical Properties of ultra High Performance concrete (UHPC)", prepared
by Ms Emanuela Emanuilova Manolova, MSc. Civ. Eng., in order to obtain the
scientific and educational grade "Doctor"
1. Generalissues
hasbeenpreparedaccordingto a decisionof the Scientificjury, appointedby
The presentstatement
relatedto the defenceprocedure
No 135dated18.02.2014,
the Rectorof UACEGby his Ordinance
of a PhD thesisentitled"Influenceof Mix Designand Technologyon MechanicalPropertiesof
concrete(UHPC)",preparedby Ms EmanuelaEmanuilovaManolova.
Ulha High Performance
Ms Manolovahas completeda masterdegreein civil engineeringin 2009 from the Universityof
Architecture,Civil EngineeringandGeodesyin Sofia- UASEG(Bulgaria).In 2010,shewasgiven
a Statescholarshipfor 3 yearsto prepareher PhD thesisin the departmentof "Building Materials
and Insulations"-UAcBc,whereher scientificsupervisorwas assoc.prof. RoumianaZahateva'
PhD, MSc Civ. Eng. In 2071, basedon a bilateral agreementbetweenUACEG and Artois
University, B6thune(France),Ms Manolovawasinscribedasa PhD studentin Laboratoryof Civil
- Artois University,underthe supervisionof both Professor
Engineeringand geo-Environnement
Eric Wirquin,andAssoc.prof. RoumianaZaharieva.
2. AnalyseofPhD thesis
The work of Ms Manolova aims to study the influenceof Mix Design and Techlology on
Concrete(UHPC)'
of Ultra High Performance
MechanicalProperties
providesa body text of 308 pagesstructuredaroundeight chapterswith a large
The dissertation
numberof referencesgiven at the endof eachchapter.
The first chapterreviewsthe studieson UHPC. Ms Manolovaanalysesthe peculiaritiesin their
properties.
andtheir mechanical
features,macro-andmicrostructure
manifacturing
composition,
The secondchapter,quite short,highlightsthe purposesof the PhD thesis.The aim is to studythe
main factorshaving impact on composition,structureand propertiesof UHPC. The thesis is
organizedaroundfive mainpurposes.
Ms Manolovadefinesthe appliedapproaches
The third chapterpresentsthe adoptedmethodology.
of studies,describesusedmaterialsand testingmethodsof freshand hardenedconcrete.Special
investigationand
theoryof plaruredexperiment,microstructure's
attentionis paid on mathematical
tests,particularlyinterestingfor this typeof concrete.
mechanical
i,(N'y
The fourth chapteraimsto optimizethe compositionof UHPC by achievinga maximumcompact
suchastypeof superplasticizer
to reduce
matrixwith fiber reinforcement
inside.Severalparameters
the WC ratio, mix designof a compactmatrix by using two methodsand varioustypes and
with differentlengths)havebeenstudied.
combinations
offibers (steelandpolypropylene
The fifth chapter examines tlre structure of UHPC. Ms Manolova has tried to characterize
fundamentalrheologicalparameters
of UHPC using a Universityof Artois' device.The special
workability of this type of concretepreventsthe using of existing concreterheometersand she
should come back to basic tests. The kinetics of hydration has been studied at different
temperatures,
usingan isothermalcalorimeter.Peculiaritiesof UHPC compositionimply that the
processof hydrationwill be differentthan in ordinaryconcrete.The usingof differentmethodsto
analyze the microstructure in time highlights the effects of curing and thermal treatment as
autoclaving.
The sixth chapteris very interestingas it's focusedon the mechanicalproperties.The influenceof
ratio,maximum
importantparameters
of the mix designandof the curingconditions(water-cement
size of aggregate,fibers, time, curing, thermal treatment..)on compressivestrengthis well
evaluated,as well as on the modulusof elasticity and the flexural strength.A particularregardhas
beengiven to bendingdiagramsin order to chancterizeUHPC' fracturetoughness,different zones
ofmechanicalbehaviorandto assess
the influenceof thetlpe offiber reinforcement.
The dissertationconcludeswith a summaryof the main resultsof the work on PhD thesisand with
research
applicationperspectives.
3. Assessment/Evaluation
of scientificcontributionsof the thesis.
Basedon a detailedstudyof the thesis,scientificand appliedresults,the following scientific
contributions
ofthe thesiscanbeoutlined:
while optimizingthe UHPC matrix - optimumgrain size
1. Combinationof two approaches
theoryof plannedexperiment,
which
distributionaccordingto a referencecurve,with mathematical
of the
allowsthe assessment
of individualand complexeffect of the most importantparameters
and quantityof superplasticizer),
on
mix design(water-cement
ratio, maximumsizeof aggregate
propertiesof thematrix.
the mechanical
2. It has beenpointed out that, by applying different methodsof mixing, curing and thermal
treatrnentof UHPC, its microsturucture
can be intentionallymodified,in orderto achievedesired
propertiesofboth freshandhardened
concrete.
3. Themethodof isothermiccalorimetry,which hasbeenappliedfor the first time to measure
of hydrationprocessofUHPC - a longer
the heatreleaseofUHPC, canbeusedfor characterization
'dormantperiod'has beenidentified,while the heatreleaseand ambienttemperatuedependence
are similar,or evenlower, comparedto that of ordinaryconcrete,despiteof muchhighercement
contentin UHPC.
4. Calculationof relevantparameters,
relatedto fracturetoughless,seemsto be a reliable
peculiarities
of UHPC mechanicalbehavior,as well as for
method for characterization
of
distinguishingthe effect of different types of fibers and for choosingof appropriatefiber
reinforcement
of UHPC.
for variousapplications
5. The detailedstudy of main physicaland mechanicalpropertiesof UHPC gives to the
engineersthe requireddatafor calculationsand dimensioningof UHPC-based
structuresand thus
createsgoodpre-conditions
for its usein construction.
+,//!'u-
--t'
work implemented
duringthis thesis.
In conclusion,I wantto welcomethe quantityof experimental
techniques
undera comprehensive
this studyby usingmanyexperimental
Ms Manolovaconducted
approach.Shehashelpedto improvethe researchon this tlpe of concreteandhasprovidedbases
for the formulationof UHPC in a futureusein Bulsaria.
4. Personalimpressions
Ms Manolovahas showna greatmotivation during her PhD and the ability to work independently.
Shedid not hesitateto be involvedin a rigorouslydesignedresearch,on a difficult and complex
allowedher to performpart of her sudiesin a Frenchlaboratory
subject.The bilatenalagreement
techniques.
andto discoverotherexperimental
5. Conclusion
presentedabove,and consideringart. 6 (3) of Bulgarian
Basedon the analysesand assessments
Law for AcademicStaff Developmentandart.27of Regulationsfor its application,I estimatethat
the PhD thesis,entitled"Influenceof Mix Designand Technologyon MechanicalPropertiesof
Ultra High PerformanceConcrete(UHPC)", meetstheir requirementsand I can suggestto the
ScientificJuryto conferto Ms EmanuelaEmanuilovaManolova,MSc Civ. Eng.,the scientificand
Civil Engineeringand
educationalgrade"Doctor" in the professionaldirection5.7."Architecture,
Geodesy",scientific specialisation"Building materialsand productsand technologiesfor their
(code02.15.05).
manufacturing"
the bilateralagreementstipulatingthat a successful
In additionto that, taking into consideration
by Artois University- France,and
procedureof PhD thesisdefencein Bulgariawill be recognised
I give my positiveopinionthat Ms Manolovais to be allowed
respecting
the Frenchrequirements,
to defendher PhD thesisat UASEG in order to obtain as well the degree"Doctor" of Artois
Universitv"France.
B6thune,
15thMarch2014
pror.
Eric
wirquin
illtl*
-Y