Analysis of temperature degraded concrete at high temperature by applying of non-linear characteristics

IOP Con e ence Se ies: Ma e ials Science and Enginee ing PAPER • OPEN ACCESS Analysis o empe a u e deg aded conc e e a high empe a u e by applying o non-linea cha ac e is ics To ci e his a icle: L Pazde a e al 2018 IOP Con . Se .: Ma e . Sci. Eng. 379 012036 View he a icle online o upda es and enhancemen s. Rela ed con en The E ec o Di e en Shape and Pe o a ed HDPE in Conc e e S uc u es on Flexu al S eng h MY Yuhaz i, KM Ha iz, YZA Myia e al. - Nume ical simula ion o damage e olu ion o duc ile ma e ials and mechanical p ope ies s udy A El Am i, I Hana i, M E Y Haddou e al. - Mechanical Pe o mance o S eel Fibe La ice Rein o ced Conc e e S uc u e Jun ei Shen and Cuixiang Jiang - This con en was downloaded om IP add ess 147.229.6.155 on 22/01/2019 a 05:49 1 Con en om his wo k may be used unde he e ms o heC ea i eCommonsA ibu ion 3.0 licence. Any u he dis ibu ion o his wo k mus main ain a ibu ion o he au ho (s) and he i le o he wo k, jou nal ci a ion and DOI. Published unde licence by IOP Publishing L d 1234567890‘’“” In e na ional Con e ence Building Ma e ials, P oduc and Technologies IOP Publishing IOP Con . Se ies: Ma e ials Science and Enginee ing 379 (2018) 012036 doi:10.1088/1757-899X/379/1/012036 Analysis o empe a u e deg aded conc e e a high empe a u e by applying o non-linea cha ac e is ics L Pazde a1, L Topolář1, M Hoduláko á1, R D ořák1 and K Mikulášek1 1 B no Uni e si y o Technology, Facul y o Ci il Enginee ing, Czech Republic Email: pazde [email p o ec ed] .cz Abs ac . Conc e e s uc u es a e commonly exposed o he mal loads as a esul o he s uc u e, ambien condi ions, he hea o hyd a ion, o exposu e o i e. The e o e, he e has been a g owing in e es in he esea ch o ad anced moni o ing and analysis o conc e e s uc u es subjec ed o he mal load. Non-linea cha ac e is ics ha e been used o iden i y he mal damage e olu ion in conc e e s uc u es. The p esen pape in es iga es he e ec s o a high empe a u e on selec ed physical p ope ies o conc e e. Conc e e p ope ies we e moni o ed and analyzed in se e al he mal s eps up o 1200°C. Conc e e specimens we e hea ed in a p og ammable labo a o y u nace a a hea ing a e o 5°C/min and loaded a six empe a u es, 200°C, 400°C, 600°C, 800°C, 1000°C, and 1200°C, wi h each main ained o 60 minu es. 1. In oduc ion In e es in he beha iou o conc e e unde high empe a u es has ecen ly been uelled by i es o indus ial, go e nmen - o p i a e-owned buildings, unnels, and o he building s uc u es. An in e es ing p inciple o non-des uc i e es ing o hea -deg aded conc e e a high empe a u es is p esen ed [1]. The me hod used in ol es measu ing he wa e p opaga ion h ough ma e ial s uc u es and i s e ec on highe ha monics. The e o e, he equency spec um o each s uc u e was compu ed using as Fou ie ans o m. S uc u al Heal h Moni o ing aims o imp o e he knowledge o he sa e y and main ainabili y o ci il s uc u es and in as uc u es [2, 3]. The e a e changes expec ed i conc e e is hea ed up o [4]: 200°C slow capilla y wa e loss and educ ion in cohesi e o ces as wa e expands, e ingi e dehyd a ion, C-S-H gel dehyd a ion, gypsum decomposi ion (CaSO4 2H2O), physically bound wa e loss, 400°C b eak up o some siliceous agg ega es ( lin ), 600°C po landi e decomposi ion Ca(OH)2→CaO+H2O, qua z phase change β−α in agg ega es and sands, 800°C second phase o he C-S-H decomposi ion, o ma ion o β-C2S, 1000°C dolomi e decomposi ion, calci e decomposi ion CaCO3→CaO+CO2, ca bon dioxide elease, ce amic binding ini ia ion which eplaces hyd aulic bonds, 1200°C basal mel ing, o e 1200°C o al decomposi ion o conc e e, mel ing. Poo ma e ial homogenei y and, in some cases, shape complexi y o some uni s used in he building indus y, a e hea ily es ic ing he applicabili y o “classical” ul asonic me hods [5, 6]. The dynamic ma e ial esponse o samples wi h damaged ma e ial in eg i y was demons a ed by he o ma ion o 2 1234567890‘’“” In e na ional Con e ence Building Ma e ials, P oduc and Technologies IOP Publishing IOP Con . Se ies: Ma e ials Science and Enginee ing 379 (2018) 012036 doi:10.1088/1757-899X/379/1/012036 di e en ha monics in he esponse equency spec a [7]. The pulse echo me hod moni o s changes in he ma e ial s uc u e based on a change in he esponse o a pulse gene a ed. Using a mechanical impac o induce mic os ain is ad an ageous o conc e e es ing because i allows o es ing o la ge conc e e specimens o e ing po en ial ield anspo abili y [8]. 2. Expe imen al se -up This pa desc ibes he expe imen and he e alua ion o he gene a ed ul asound signals when es ing hei passage h ough he ma e ial o conc e e specimens a e a hea load. The es s we e pe o med on beams wi h a c oss sec ion o 100 mm by 100 mm and leng h o 400 mm as shown in Figu e 1. Th ee ypes o beams we e made acco ding o Table 1 wi h he kind o he coa se agg ega e ha ing been hus changed. S a ing a a no mal empe a u e o 22°C, he specimens we e hea ed a a hea ing a e o 5°C/min up o a p e-se empe a u e main ained o 60 minu es and hen placed in a oom wi h a no mal empe a u e o 22°C. Table 1. Mix u e moni o ed. A B C (kg/m3) (kg/m3) (kg/m3) cemen CEM I 42.5R 345 345 345 sand 0/4 813 813 813 coa se agg ega e 4/8 1010 coa se agg ega e 8/16 1010 coa se agg ega e 11/22 1010 wa e 176 176 176 supe plas icize 3 3 3 The p e-se empe a u es we e 200°C, 400°C, 600°C, 800°C, 1000°C, and 1200°C. The beams we e es ed a a no mal empe a u e. Figu e 1. Expe imen al se up . The specimens we e exci ed by a senso placed in he cen e o a squa e side. Impulses we e gene a ed by he ul asound equipmen PUNDIT. The acous ic emission sys em XEDO was applied o de ec he wa es. Th ee piezoelec ic senso s we e placed on di e en sides o he specimen. The i s senso was si ua ed nea he exci e on he pe pendicula side, he second one on he opposi e side o he specimen being 50 mm away om he opposi e side on he side pe pendicula o he i s one and he hi d senso was on he same side as he i s one bu 50 mm away om he opposi e edge. 3 1234567890‘’“” In e na ional Con e ence Building Ma e ials, P oduc and Technologies IOP Publishing IOP Con . Se ies: Ma e ials Science and Enginee ing 379 (2018) 012036 doi:10.1088/1757-899X/379/1/012036 Twen y specimens, made a e he mal deg ada ion by each empe a u e, we e moni o ed by hese es s. The e o s o he measu ed and compu ed alues do no exceed i e pe cen age poin s. 3. Resul s The esul s a e p esen ed as an analysis o he i s eigen equency compu ed om he equency spec a o he specimen esponse cha ac e is ic as shown in he ollowing ables and igu es. Table 2. Cube comp ession s eng hs o h ee di e en mix u es. Tempe a u e A B C (oC) (MPa) (MPa) (MPa) 20 65 75 50 200 63 63 43 400 54 57 48 600 46 41 28 800 31 31 24 1000 14 8 6 1200 16 10 28 Figu e 2. The c ube comp ession s eng h ( c ) on he deg aded empe a u e (T). F om he alues o he comp ession s eng h on cubes (see Table 2 and Figu e 2), i can be concluded ha , o all empe a u es, mix u e B shows he bigges loss o s eng h ela i e o a e e ence empe a u e. In e es ing is he beha iou o mix u e C whe e he e is a dec ease as expec ed i hea ed o 200°C, howe e , wi h an inc ease i hea ed o 400°C, which could be accoun ed o by he ac ions o he agg ega e used being nea . Then, an inc ease in he ela i e comp ession s eng h should also be poin ed ou a a empe a u e o 1200°C; o pa icula mix u es, his inc ease is caused by a new c ys alline o m, Wollas oni e, being buil a a empe a u e o abou 1100°C. This inc ease is he g ea es in mix u e C and, again, his could be accoun ed o by he icini y o he ac ions o he agg ega e used. 0.0 0.2 0.4 0.6 0.8 1.0 1.2 20 200 400 600 800 1000 1200 c / MPa T / o C A B C 4 1234567890‘’“” In e na ional Con e ence Building Ma e ials, P oduc and Technologies IOP Publishing IOP Con . Se ies: Ma e ials Science and Enginee ing 379 (2018) 012036 doi:10.1088/1757-899X/379/1/012036 Fo analysing he beha iou o he samples by he pulse-echo me hod, he i s ha monic equencies we e calcula ed o he signal moni o ed using as Fou ie ans o m. The alues o he eigen equencies ound o each sample a a ious deg ees o deg ada ion a e shown in Table 3. The changes o hese alues ela i e o he basic alue o he sample se a a empe a u e o 20oC can be seen in Figu e 3. Table 3. F equencies o h ee di e en mix u es. Tempe a u e A B C (oC) (kHz) (kHz) (kHz) 20 43.9 90.3 45.4 200 45.4 93.2 44.4 400 41.9 85.0 42.8 600 17.6 28.3 16.1 800 16.6 22.9 14.2 1000 7.3 14.6 14.6 1200 14.6 24.7 25.4 - Figu e 3. The ela i e eigen equency ( ) on he deg aded empe a u e (T). The equency alue inc easing a e empe a u e inc ease o 200°C p obably causes an imp o emen o he s uc u e bonds. This occu ed in mix u es A and whe e he e is mo e space be ween he agg ega e pa icles o sel - epai o he cemen due o he ambien humidi y du ing he es . In mix u e C wi h mo e ine agg ega e pa icles, no such e ec has been obse ed. As he empe a u e inc eases u he , a dec ease is appa en in he equency alues o all mix u es. Only o he las empe a u e o 1200°C, again, a eac ion can be obse ed o he appea ance o Wollas oni e o he mix u e, which is again mos ma ked in mix u e C. A simila sample beha iou pa e n can also be obse ed i he dec ease o he highe ha monics is linea ized o pa icula samples. He e, he expec ed exponen ial dec ease o he ha monic componen 0.0 0.2 0.4 0.6 0.8 1.0 1.2 20 200 400 600 800 1000 1200 T / o C A B C 5 1234567890‘’“” In e na ional Con e ence Building Ma e ials, P oduc and Technologies IOP Publishing IOP Con . Se ies: Ma e ials Science and Enginee ing 379 (2018) 012036 doi:10.1088/1757-899X/379/1/012036 ampli udes is linea ized by he spec um being ans o med in o decibels. The alues can be ound in Table 4 wi h hei ela ionships o he basic- empe a u e sample in Figu e 4. Table 4. Slopes o h ee di e en mix u es. Tempe a u e A B C (oC) (dB/kHz) (dB/kHz) (dB/kHz) 20 -0.494 -0.414 -0.487 200 -0.586 -0.583 -0.415 400 -0.661 -0.448 -0.390 600 -1.122 -0.644 -0.568 800 -1.728 -0.471 -0.774 1000 -2.383 -1.842 -1.647 1200 -1.391 -1.390 -0.763 No e ha Table 4 shows he alues o he a enua ion k o he equa ion 𝑆= 𝑐 ∙ exp (𝑘 ∙ 𝑓 ) (1) whe e Sn is he ampli ude o he equency spec um, n is he equency, n is he numbe o he ha monic and c and k a e cons an s. I is clea ha 𝑓 = 𝑛 ∙ 𝑓  whe e 1 is he i s ha monic [9]. A change in he i s ha monic along wi h he slope o he a enua ion o he ha monics accoun o he changes in he obse ed samples. Figu e 4. The ela i e s lope o linea app oxima ion (k) on he deg aded empe a u e (T). 4. Conclusion The pulse-echo me hod seems o be well-sui ed o de e mining he deg ee o damage o he hea - deg aded conc e es. As shown, he esul s o a non-des uc i e pulse-echo me hod can be well co ela ed wi h he des uc i e p essu e es . This compa ison is mainly e iden in Figu es 4 ( he non- 0.0 1.0 2.0 3.0 4.0 5.0 20 200 400 600 800 1000 1200 k T / o C A B C 6 1234567890‘’“” In e na ional Con e ence Building Ma e ials, P oduc and Technologies IOP Publishing IOP Con . Se ies: Ma e ials Science and Enginee ing 379 (2018) 012036 doi:10.1088/1757-899X/379/1/012036 des uc i e es ing o he pulse-echo me hod) and 3 ( he des uc i e p essu e es ) when he cha ac e s a e simila . In he nea u u e, we expec he me hodology o hese echniques o be de eloped and applied o a ious ma e ials es ing p ocedu es. This me hod may also help c ea e o imp o e a nume ic model o wa e p opaga ion in conc e es o di e en s uc u es. F om he e alua ion o hese samples, i can be assumed ha , wi h he inc easing size o he coa se agg ega es, he he mal esis ance o he conc e e mix u e dec eases. I has been shown ha analyzing high- equency dynamic cha ac e is ics gene a ed by a pulse signal may indi ec ly in luence he na u e o an obse ed s uc u e. The changes in he comp ession s eng h o hea -deg aded samples a e co ela ed wi h he changes in he dynamic p ope ies o a s uc u e. Acknowledgemen This pape has been w i en unde he p ojec GAČR No.16-02261S suppo ed by Czech Science Founda ion and he p ojec No. LO1408 "AdMaS UP - Ad anced Ma e ials, S uc u es and Technologies", suppo ed by Minis y o Educa ion, You h and Spo s unde he „Na ional Sus ainabili y P og amme I". 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