Ci a ion: Bada loo, B.; Lehne , P.
P ac ical Aspec s o Co ela ion
Analysis o Comp essi e S eng h
om Des uc i e and
Non-Des uc i e Me hods in
Di e en Di ec ions. In as uc u es
2023,8, 155. h ps://doi.o g/10.3390/
in as uc u es8110155
Academic Edi o : Ma co Bonope a
Recei ed: 28 Augus 2023
Re ised: 11 Oc obe 2023
Accep ed: 20 Oc obe 2023
Published: 24 Oc obe 2023
Copy igh : © 2023 by he au ho s.
Licensee MDPI, Basel, Swi ze land.
This a icle is an open access a icle
dis ibu ed unde he e ms and
condi ions o he C ea i e Commons
A ibu ion (CC BY) license (h ps://
c ea i ecommons.o g/licenses/by/
4.0/).
in as uc u es
Technical No e
P ac ical Aspec s o Co ela ion Analysis o Comp essi e
S eng h om Des uc i e and Non-Des uc i e Me hods in
Di e en Di ec ions
Bai ollah Bada loo 1and Pe Lehne 2,*
1Depa men o Ci il Enginee ing, Qom Uni e si y o Technology (QUT), Qom 37181-46645, I an
2Depa men o S uc u al Mechanics, Facul y o Ci il Enginee ing, VSB-Technical Uni e si y o Os a a,
Lud íka Podéš ˇe 1875/17, 708 33 Os a a-Po uba, Czech Republic
*Co espondence: pe [email p o ec ed]
Abs ac :
The esea ch p esen ed he e demons a es he p ac ical aspec s o he nume ical co ela ion
o he esul s o he comp essi e s eng h es . The des uc i e es (DT) in a hyd aulic p ess and he
non-des uc i e es (NDT) using a Schmid hamme in se e al p ocess a ia ions we e e alua ed.
The aim was o e alua e he eal di e ences be ween he ool supplie ’s cu e and es ing. The e o e,
150 conc e e cube specimens wi h an edge leng h o 150 mm we e p oduced using a mix u e o
h ee ypes o conc e e classes: C30, C35, and C40. The es was ca ied ou 7 and 28 days o age o
he conc e e. The Schmid hamme es was ca ied ou in ho izon al (
θ
= 0) and e ical (
θ
= 90)
di ec ions and using a se ies o 10 measu emen s. Fu he mo e, he es s we e pe o med in wo se s:
i s , he sample was placed on he g ound, and second, unde a hyd aulic jack wi h a load o 50% o
he maximum bea ing capaci y o speci ic conc e e. Then, eg ession analysis was pe o med on he
da a se s o es ablish linea ma hema ical ela ionships be ween comp essi e s eng h and numbe o
bounces. The esul s showed ha he co ela ion be ween he DT and NDT es s has a high alue o
each g oup, bu he co ela ion equa ions a e di e en and mus be aken in o accoun .
Keywo ds:
comp essi e s eng h; conc e e; des uc i e es ing; non-des uc i e es ing; eg ession;
Schmid hamme
1. In oduc ion
Conc e e is one o he impo an cons uc ion ma e ials ha is widely used in building
s uc u es due o i s a ailabili y, low cos , and wo kabili y [
1
,
2
]. Because conc e e unde
load p essu e can ail, de e mining i s comp essi e s eng h plays a i al ole in judging i s
quali y. Bo h des uc i e and non-des uc i e es ing me hods ha e been applied o es ima e
comp ession s eng h. A conside able amoun o wo k has ocused on he comp essi e
s eng h o conc e e. Rega ding des uc i e es ing (DT) me hods, such as he use o a
hyd aulic jack, i should be men ioned ha he esul s ob ained om his me hod a e
accu a e [
3
–
7
]. Howe e , his me hod su e s om d awbacks such as high cos , ene gy
consump ion, labo , ime, and lack o abili y o measu e in si u conc e e. The e o e, non-
des uc i e es ing (NDT) me hods a e now popula in ha hey a e ca ied ou wi hou
des oying he conc e e specimen, while in DT me hods he specimen should be c ushed o
ail [
8
–
10
]. These NDT me hods a e sui able o in si u measu emen s on exis ing s uc u es
o o long- e m measu emen s, whe e i is necessa y o de e mine he changes in conc e e
s eng h o e ime.
NDT me hods can di ec ly e alua e he quali y o a building e en on-si e by es ima ing
he comp essi e s eng h o he conc e e s uc u e, and he mos commonly used NDT
me hod is he Schmid hamme [
8
,
11
,
12
]. Se e al au ho s ha e used he Schmid hamme
o measu e conc e e s eng h [
8
,
13
–
16
]. A Schmid hamme , also known as a Swiss hamme
o a ebound hamme , is a po able de ice ha measu es he elas ic p ope ies o he
In as uc u es 2023,8, 155. h ps://doi.o g/10.3390/in as uc u es8110155 h ps://www.mdpi.com/jou nal/in as uc u es
In as uc u es 2023,8, 155 2 o 14
s eng h o conc e e. Mo eo e , NDT me hods a e highly bene icial o measu ing di e en
pa ame e s o conc e e, i.e., s eng h, du abili y, and homogenei y [
9
]. P e iously, some
s udies ha e compa ed a des uc i e es ing me hod (co e es ing) wi h an NDT me hod.
NDT me hods a e used o he analysis o conc e es o di e en basic ma e ials and di e en
applica ions [10,17].
Acco ding o hei esea ch, he NDT me hod has he ollowing ad an ages in com-
pa ison o DT me hods: (1) lowe cos , (2) simplici y, (3) educ ion in labo consump ion,
(4) g ea e speed, and (5) e alua ion o conc e e p ope y wi hou damaging i [
18
]. The
amoun o ebound depends on se e al conc e e pa ame e s, i.e., ha dness, coe icien
o elas ici y, o e, wa e con en mo phology o he sample, su ace oughness, ype o
agg ega ion, and conc e e ing edien [
19
,
20
]. Mo eo e , small es a eas, lack o equipmen ,
and es di ec ion should be conside ed as de e mining pa ame e s in NDT me hods [
21
].
Rega dless o he ad an ages associa ed wi h NDT me hods, his me hod is aniso opy
in which di e en di ec ions o measu ing can a ec hei alue. Mo eo e , because he
esul s ob ained om using a Schmid hamme can be a ec ed by se e al pa ame e s such
as he amoun o po osi y, mois u e, ha dness, oughness, e c., he esul s a e mo e o an
app oxima ion han a p ecise alue. Consequen ly, esea che s ha e ied o o e come his
limi a ion by inding a co ela ion be ween DT and NDT alues o inc ease he accu acy o
measu ing comp essi e s eng h.
In ecen yea s, o he au ho s ha e also sea ched o he co ec co ela ion ela ions
be ween NDT me hods and DT me hods, because hese co ela ions we e no de e mined
on non-s anda d conc e es [
22
,
23
]. The e a e also s udies using machine lea ning me hods
o p edic he dynamic comp essi e esponse o composi e ma e ials [24].
In he p esen ed esea ch, bo h DT (hyd aulic p ess machine) and NDT ( ebound
hamme ) me hods we e p oposed o e alua e he comp essi e s eng h o C30, C35, and
C40 o de ine a me hod mo e eliable and p ac ical. I should be no ed ha in o de o
minimize e o s in in es iga ions, wa e con en , p ocessing, and a mosphe e empe a u e
we e kep cons an . Then, a emp s we e made o compa e he esul s ob ained om he
cube samples by eg ession o ind an accu a e ela ionship be ween he DT and he NDT
da a in which he co ela ion coe icien is g ea e han 0.85. The esul s o a la ge numbe
o es s we e used o e alua e he p ac ical use o he Schmid hamme in many aspec s.
The s a is ical and nume ical e alua ion o accu a e measu ed da a in la ge quan i ies is o
g ea impo ance o bo h academia and p ac ice, whe e he Schmid hamme is used and
has signi ican alue. This is no he only eason why he esul s p esen ed and e alua ed
a e placed in he con ex o cu en ends and habi s.
2. Ma e ials and Me hods
2.1. Mix u es and Samples
Th ee ypes o conc e e wi h di e en equi ed s eng hs had o be p epa ed o he
expe imen s. The conc e e composi ion is based on o dina y Po land cemen o he Teh an
b and (OPC), po able wa e (as pe ASTM D1067 [
25
]), ine agg ega e (sand), and coa se
agg ega e (g a el) om a local sou ce (Qom, I an). The design o he mix u es was ca ied
ou in acco dance wi h ACI-211 [26], and he composi ion is shown in Table 1.
Table 1. Mix u e design.
Conc e e Sand
(kg)
G a el
(kg)
Cemen
(kg)
Wa e
(li ) Slump Wa e /Cemen
C30 950 852 400 228 7.5–10 0.57
C35 950 852 450 234 7.5–10 0.52
C40 950 852 500 240 7.5–10 0.48
These h ee ypes o conc e e we e selec ed because hey a e he mos commonly used
in he cons uc ion indus y. The eason o he h ee ypes was o accoun o di e ences
In as uc u es 2023,8, 155 3 o 14
in he case o s eng h. All conc e es had he same ine agg ega e and coa se agg ega e,
bu di e en cemen and wa e con en s. This esul ed in di e en w/c a ios and hus
di e en esul ing s eng hs.
The manu ac u e o he conc e e was ca ied ou in acco dance wi h BS 1881: Pa
108:1983 [
27
]. In he p oduc ion o conc e e, he d y ing edien s we e mixed wi h each
o he a ambien empe a u e, hen hal o he wa e was added, and all he ing edien s
we e mixed o 2 min o o m a homogeneous mix u e. The es o he wa e was hen
added and he ma e ials we e mixed o 2 min. The samples we e hen cas in o cube
molds, compac ed, and le a oom empe a u e o 24 h; hey we e ans e ed o a ank
o wa e and cu ed o 7 and 28 days. A o al o 150 cubic specimens (50 samples o each
class) cubic specimens (150 mm
×
150 mm
×
150 mm) we e p oduced in 3 di e en classes.
The e o e, each es se is based on 25 iden ical es samples. Thus, as shown below, i was
es ed in wo di e en di ec ions, and a la ge s a is ical e alua ion was ob ained due o he
numbe o 25 samples pe condi ion.
2.2. Expe imen al P og am
Th ee es s we e p epa ed in he expe imen al p og am—non-des uc i e e ical
hamme es , non-des uc i e ho izon al hamme es on a loaded specimen, and des uc i e
p essu e es in a hyd aulic p ess machine. A 50% alue o he maximum p edic ed o ce
was used o each ype o conc e e— o conc e e C30, i was 15 MPa, o conc e e C35 i was
17.5 MPa, and o conc e e C40 i was 20 MPa. All es s we e pe o med sequen ially on
he same specimens o main ain a comple e co ela ion o esul s. Figu e 1shows he s eps
o use a Schmid hamme . The i s pic u e is he calib a ion sample, he second pic u e is
he es measu emen in a e ical way, and he hi d pic u e is he es measu emen in a
ho izon al way.
In as uc u es 2023, 8, x FOR PEER REVIEW 3 o 14
These h ee ypes o conc e e we e selec ed because hey a e he mos commonly used
in he cons uc ion indus y. The eason o he h ee ypes was o accoun o diffe ences
in he case o s eng h. All conc e es had he same ine agg ega e and coa se agg ega e,
bu diffe en cemen and wa e con en s. This esul ed in diffe en w/c a ios and hus
diffe en esul ing s eng hs.
The manu ac u e o he conc e e was ca ied ou in acco dance wi h BS 1881: Pa
108:1983 [27]. In he p oduc ion o conc e e, he d y ing edien s we e mixed wi h each
o he a ambien empe a u e, hen hal o he wa e was added, and all he ing edien s
we e mixed o 2 min o o m a homogeneous mix u e. The es o he wa e was hen
added and he ma e ials we e mixed o 2 min. The samples we e hen cas in o cube
molds, compac ed, and le a oom empe a u e o 24 h; hey we e ans e ed o a ank
o wa e and cu ed o 7 and 28 days. A o al o 150 cubic specimens (50 samples o each
class) cubic specimens (150 mm × 150 mm × 150 mm) we e p oduced in 3 diffe en classes.
The e o e, each es se is based on 25 iden ical es samples. Thus, as shown below, i was
es ed in wo diffe en di ec ions, and a la ge s a is ical e alua ion was ob ained due o
he numbe o 25 samples pe condi ion.
2.2. Expe imen al P og am
Th ee es s we e p epa ed in he expe imen al p og am—non-des uc i e e ical
hamme es , non-des uc i e ho izon al hamme es on a loaded specimen, and des uc-
i e p essu e es in a hyd aulic p ess machine. A 50% alue o he maximum p edic ed
o ce was used o each ype o conc e e— o conc e e C30, i was 15 MPa, o conc e e
C35 i was 17.5 MPa, and o conc e e C40 i was 20 MPa. All es s we e pe o med sequen-
ially on he same specimens o main ain a comple e co ela ion o esul s. Figu e 1 shows
he s eps o use a Schmid hamme . The i s pic u e is he calib a ion sample, he second
pic u e is he es measu emen in a e ical way, and he hi d pic u e is he es measu e-
men in a ho izon al way.
(a) (b) (c)
Figu e 1. S eps o use a Schmid hamme : (a) placing he calib a ion elemen , (b) es ing e ically,
(c) es ing ho izon ally.
Be o e s a ing he es , he hamme should be calib a ed; he a e age o en eading
numbe s should be conside ed as calib a ion be o e each es . Fu he mo e, he es su -
ace should be smoo h, e en in he labo a o y o on si e. The specimen should also be held
Figu e 1.
S eps o use a Schmid hamme : (
a
) placing he calib a ion elemen , (
b
) es ing e ically,
(c) es ing ho izon ally.
Be o e s a ing he es , he hamme should be calib a ed; he a e age o en eading
numbe s should be conside ed as calib a ion be o e each es . Fu he mo e, he es su ace
should be smoo h, e en in he labo a o y o on si e. The specimen should also be held
by a igid keepe o a oid shaking. I should be no ed ha he di ec ion o he hamme
can a ec he ha dness alues. Acco ding o ASTM C805-02 [28], he hamme should i s
In as uc u es 2023,8, 155 4 o 14
be kep e ical and hen he specimen placed on a hyd aulic jack o ake he numbe o
opposi e aces o he cube specimen. An a e age o 10 eading numbe s o each su ace was
conside ed as a hamme ebound numbe . I he measu ed alue de ia ed om he a e age
by 20%, i was no included in he inal in es iga ion. Fu he mo e, i hese neglec ed
eading numbe s we e mo e han 2 on each su ace, hen he es was no eliable and was
cancelled. Finally, he specimen was des uc i ely es ed o de e mine he comp essi e
s eng h o he hyd aulic p ess machine. The comp essi e s eng h o conc e e is a es
ca ied ou on a cube, a cylinde , o a sui able piece o b oken beam, some imes on co e
holes. A minimum o h ee bodies a e always es ed. Be o e he ac ual es , he geome y o
he es body is e i ied. Specimens ha ail non-s anda dly a e excluded om he es . A
eco d o each es and i s esul s shall be kep .
2.3. S a is ics
The main aim was o ind a ela ionship be ween he DT and NDT esul s. These
wo g oups we e i s co ela ed o all conc e es using Pea son’s co ela ion coe icien
(PCC) [
29
]. The Pea son co ela ion coe icien is a desc ip i e s a is ic ha sums up he
cha ac e is ics o a da a se . Speci ically, i desc ibes he s eng h and di ec ion o he
linea ela ionship be ween wo quan i a i e a iables. Fo example, a PCC g ea e han
0.5 means s ong s eng h. The same se was hen analyzed using linea eg ession [
30
] and
he de e minan R
2
[
31
,
32
]. R
2
is a s a is ic used in he con ex o s a is ical models whose
main pu pose is o p edic u u e ou comes.
This analysis p o ides a measu e o how well obse ed ou comes a e eplica ed by
he model, based on he p opo ion o o al a ia ion o ou comes explained by he model.
Linea eg ession analysis is used o p edic he alue o a a iable based on he alue
o ano he a iable. The a iable you wan o p edic is called he dependen a iable.
The a iable you use o p edic he alue o ano he a iable is called he independen
a iable. This o m o analysis es ima es he coe icien s o a linea equa ion in ol ing one
o mo e independen a iables ha bes p edic he alue o he dependen a iable. A
linea eg ession co esponds o a line o a ea ha minimizes he di e ences be ween he
p edic ed and ac ual alues o he ou pu .
The e alua ion o co ela ion and linea eg ession indica es whe he wo pa ame e s
ha e a e y high, high, mode a e, low, o no dependence. These nume ically ob ained
linea co ela ion cu es we e aced wi h he no ma i e cu e o he Schmid hamme used.
The cu es ob ained we e also desc ibed using he equa ion and he s a is ical pa ame e s
desc ibed abo e.
3. Resul s and Discussion
DT and NDT in es iga ions we e ca ied ou on h ee di e en g ades o conc e es,
namely, C30, C35, and C40, o es ima e comp essi e s eng h wi h a good app oxima ion.
Tables 2and 3p esen he a e age o 25 comp essi e s eng h measu es in MPa and
25 ebound numbe s in e ical and ho izon al hamme posi ions o conc e e cu ed o
7 and 28 days, espec i ely. Acco ding o he esul s, he comp essi e s eng h inc eased
wi h inc easing conc e e g ade; wi h espec o samples cu ed o 7 days, he comp essi e
s eng h inc eased om 31.7 MPa (C30) o 38.9 MPa (C40). Fu he mo e, o samples cu ed
o 28 days, he comp essi e s eng h inc eased om 42.9 MPa (C30) o 51.1 MPa (C40).
The e o e, by compa ing he esul s, i is ob ious ha inc easing he numbe o days ha
conc e e samples we e cu ed in wa e led o an inc ease in comp essi e s eng h. Mo eo e ,
i can be unde s ood om Tables 2and 3 ha i he hamme posi ion changes om a
ho izon al di ec ion o a e ical di ec ion, he ebound numbe dec eases.
These obse a ions do no de ia e om he expec a ions and in o ma ion a ailable
in he li e a u e [
8
,
11
,
18
]. E alua ion o he s anda d de ia ion shows ha in all cases he
numbe s a e less han 10% o he mean, which co esponds o he es ic ion ha no esul
had o be excluded om he s a is ical se .
In as uc u es 2023,8, 155 5 o 14
Table 2.
A e age comp essi e s eng hs in MPa and ebound numbe o di e en conc e e cu ed o
7 days.
Age Class Tes Mean STD
7 days
C30
Comp essi e S eng h 31.7 MPa 3.19
Rebound numbe (ho izon al) 28.5 2.81
Rebound numbe ( e ical) 23.1 1.22
C35
Comp essi e S eng h 37.5 MPa 2.74
Rebound numbe (ho izon al) 30.1 2.48
Rebound numbe ( e ical) 24.5 2.25
C40
Comp essi e S eng h 38.9 MPa 4.22
Rebound numbe (ho izon al) 33.2 2.14
Rebound numbe ( e ical) 26 1.75
Table 3.
A e age comp essi e s eng h in MPa and ebound numbe o di e en conc e e cu ed o
28 days.
Age Class Tes Mean STD
28 days
C30
Comp essi e S eng h 42.9 MPa 4.82
Rebound numbe (ho izon al) 34.1 2.19
Rebound numbe ( e ical) 25.9 1.73
C35
Comp essi e S eng h 47.1 MPa 4.36
Rebound numbe (ho izon al) 35.5 1.19
Rebound numbe ( e ical) 28.6 2.36
C40
Comp essi e S eng h 51.1 MPa 3.68
Rebound numbe (ho izon al) 36.1 1.55
Rebound numbe ( e ical) 30.7 3.15
A compa ison be ween he s anda d de ia ion o he hyd aulic p ess measu emen
and he s anda d de ia ion o he ebound es shows ha in his applica ion he ebound
esul s ha e less a iance. This was obse ed o all h ee ypes o conc e e.
To ind he co ela ion be ween Schmid ebound numbe and comp essi e s eng h,
he c ushing conc e e s eng h in MPa e sus ebound numbe s is plo ed o 7-day-old
conc e e and in ho izon al hamme posi ion o conc e e C30 (see Figu e 2), C35 (see
Figu e 3), and C40 (Figu e 4). Simila ly, da a om e ical measu emen s a 7 days a e
conc e ing we e analyzed. The esul s a e p esen ed oge he wi h he eg ession cu e in
Figu es 5–7. Fu he mo e, da a a 28 days o all conc e es in he ho izon al di ec ion (see
Figu es 8–10) and he e ical di ec ion o he hamme measu emen (see Figu es 11–13)
a e p esen ed.
Fi s , an e alua ion o he esul s measu ed 7 days a e he conc e e. The co ela ion
be ween he ho izon al ebound hamme measu emen and he hyd aulic comp essi e
s eng h o conc e e C30 shown in Figu e 2shows a PCC o 95%, demons a ing high
ag eemen . E en he g aphical e alua ion o he linea co ela ion has a de e mina ion
alue o o e 0.9. On he o he hand, in Figu e 3, whe e he same pai is co ela ed bu o
C35 conc e e, a sligh ly highe PCC is seen, bu he linea eg ession has a be e i in his
case. The equa ion o he cu e has a di e en basis bu a e y simila slope. Figu e 4 hen
shows he conc e e C40, o which he co ela ion eg ession cu e has a nega i e in e cep
alue on he y-axis, and so i can be seen ha he cu e is signi ican ly di e en . Unlike he
i s wo conc e es (C30 and C35), he C40 conc e e has a no ma i e ins umen cu e wi h
almos he same slope as he esul ing co ela ion cu e om he nume ical e alua ion.
Figu e 5shows he co ela ion o he e ical ebound es expe imen and he com-
p essi e s eng h o he p ess o C30 conc e e. The co ela ion o he esul s is a a e y
high le el and he cu e de e mina ion is also e y high. The slope o he cu e does no
co espond o he no ma i e cu e. Figu e 6 hen shows he same es s, bu o C35 conc e e.
Again, we see high co ela ion coe icien numbe s and high ag eemen . Figu e 7shows

In as uc u es 2023,8, 155 6 o 14
he same o C40 conc e e. Again, o his conc e e, he slope o he eg ession cu e is e y
simila o he no ma i e cu e.
In as uc u es 2023, 8, x FOR PEER REVIEW 6 o 14
Figu e 2. Co ela ion o he ebound index o he ho izon al es and comp essi e s eng h a 7
days o conc e e C30.
Figu e 3. Co ela ion o he ebound index om he ho izon al es and comp essi e s eng h a 7
days o conc e e C35.
Figu e 2.
Co ela ion o he ebound index o he ho izon al es and comp essi e s eng h a 7 days
o conc e e C30.
In as uc u es 2023, 8, x FOR PEER REVIEW 6 o 14
Figu e 2. Co ela ion o he ebound index o he ho izon al es and comp essi e s eng h a 7
days o conc e e C30.
Figu e 3. Co ela ion o he ebound index om he ho izon al es and comp essi e s eng h a 7
days o conc e e C35.
Figu e 3.
Co ela ion o he ebound index om he ho izon al es and comp essi e s eng h a 7
days o conc e e C35.
In as uc u es 2023,8, 155 7 o 14
In as uc u es 2023, 8, x FOR PEER REVIEW 7 o 14
Figu e 4. Co ela ion o he ebound index o he ho izon al es and comp essi e s eng h a 7
days o conc e e C40.
Figu e 5. Co ela ion o he ebound index o he e ical es and comp essi e s eng h a 7 days
o conc e e C30.
Figu e 4.
Co ela ion o he ebound index o he ho izon al es and comp essi e s eng h a 7 days
o conc e e C40.
In as uc u es 2023, 8, x FOR PEER REVIEW 7 o 14
Figu e 4. Co ela ion o he ebound index o he ho izon al es and comp essi e s eng h a 7
days o conc e e C40.
Figu e 5. Co ela ion o he ebound index o he e ical es and comp essi e s eng h a 7 days
o conc e e C30.
Figu e 5.
Co ela ion o he ebound index o he e ical es and comp essi e s eng h a 7 days o
conc e e C30.
In as uc u es 2023,8, 155 8 o 14
In as uc u es 2023, 8, x FOR PEER REVIEW 8 o 14
Figu e 6. Co ela ion o he ebound index o he e ical es and comp essi e s eng h a 7 days o
conc e e C35.
Figu e 7. Co ela ion o he ebound index o he e ical es and comp essi e s eng h a 7 days o
conc e e C40.
PCC = 0.958
y = 2.4942x − 25.191
R² = 0.918
0
10
20
30
40
50
60
70
0 102030405060
Comp essi e S eng h [MPa] (DT)
Schmid Rebound Numbe [-] (NDT)
C35 - day 7 - e ical
Expe imen s
No ma i e Schmid cu e
Linea - expe imen
Figu e 6.
Co ela ion o he ebound index o he e ical es and comp essi e s eng h a 7 days o
conc e e C35.
In as uc u es 2023, 8, x FOR PEER REVIEW 8 o 14
Figu e 6. Co ela ion o he ebound index o he e ical es and comp essi e s eng h a 7 days o
conc e e C35.
Figu e 7. Co ela ion o he ebound index o he e ical es and comp essi e s eng h a 7 days o
conc e e C40.
PCC = 0.958
y = 2.4942x − 25.191
R² = 0.918
0
10
20
30
40
50
60
70
0 102030405060
Comp essi e S eng h [MPa] (DT)
Schmid Rebound Numbe [-] (NDT)
C35 - day 7 - e ical
Expe imen s
No ma i e Schmid cu e
Linea - expe imen
Figu e 7.
Co ela ion o he ebound index o he e ical es and comp essi e s eng h a 7 days o
conc e e C40.
In as uc u es 2023,8, 155 9 o 14
In as uc u es 2023, 8, x FOR PEER REVIEW 9 o 14
Figu e 8. Co ela ion o he ebound index om he ho izon al es and comp essi e s eng h a 28
days o conc e e C30.
Figu e 9. Co ela ion o he ebound index o he ho izon al es and comp essi e s eng h a 28 days
o conc e e C35.
Figu e 8.
Co ela ion o he ebound index om he ho izon al es and comp essi e s eng h a 28
days o conc e e C30.
In as uc u es 2023, 8, x FOR PEER REVIEW 9 o 14
Figu e 8. Co ela ion o he ebound index om he ho izon al es and comp essi e s eng h a 28
days o conc e e C30.
Figu e 9. Co ela ion o he ebound index o he ho izon al es and comp essi e s eng h a 28 days
o conc e e C35.
Figu e 9.
Co ela ion o he ebound index o he ho izon al es and comp essi e s eng h a 28 days
o conc e e C35.