Properties of fly ash and metakaolín based geopolymer panels under fire resistance tests

Ma e iales de Cons uCCión Vol. 65, Issue 319, July–Sep embe 2015, e059 ISSN-L: 0465-2746 h p://dx.doi.o g/10.3989/mc.2015.06114 P ope ies o ly ash and me akaolín based geopolyme panels unde i e esis ance es s Y. Luna-Galiano *, A. Co nejo, C. Lei a, L.F. Vilches, C. Fe nández-Pe ei a Uni e si y o Se ille, (Se illa, Spain) *[email p o ec ed].es Recei ed 9 Sep embe 2014 Accep ed 21 Janua y 2015 A ailable on line 10 June 2015 ABSTRACT: This pape p esen s he esul s o a s udy abou he e ec o i e on geopolyme pas e composed o ly ashes, me akaolin and sodium silica e. 2 cm hick, 28 cm high and 18 cm wide panels we e illed wi h he pas e ob ained. A e 28 days o cu ing a 20°C and 45% o ela i e humidi y, di e en es s we e ca ied ou in he geopolyme s: physico-chemical (densi y, wa e abso p ion, po osi y), mechanical ( lexu al and com- p essi e s eng h), i e esis ance and en i onmen al (leaching and adioac i i y). The panels manu ac u ed ha e been compa ed wi h o he comme cial panels in o de o de e mine he ecycling possibili ies o ly ashes in manu ac u ing new i e-insula ing geopolyme s. The panels ob ained can be u ilized o he p oduc ion o in e io wall ma e ials, wi h a good physical, mechanical, i e esis an p ope ies wi hou any en i onmen al p oblem. KEYWORDS: Fly ash; Me akaolin; Mechanical p ope ies; Po e size dis ibu ion; Tempe a u e Ci a ion/Ci a como: Luna-Galiano, Y.; Co nejo, A.; Lei a, C.; Vilches, L.F.; Fe nández-Pe ei a, C. (2015) P ope ies o ly ash and me akaolín based geopolyme panels unde i e esis ance es s. Ma e . Cons ucc. 65 [319], e059 h p:// dx.doi.o g/10.3989/mc.2015.06114. RESUMEN: P opiedades de paneles geopolimé icos basados en ceniza olan e y me acaolín bajo ensayos de esis- encia al uego. Es e documen o p esen a los esul ados de un es udio sob e el e ec o del uego sob e pas as de geopolíme os compues as de cenizas olan es, me acaolín y silica o sódico. Con la pas a ob enida se han ellenado paneles de dimensiones 2 cm de espeso , 28 cm de al u a y 18 cm de ancho. T as 28 días de cu ado a 20°C y un 45% de humedad ela i a, di e en es ensayos ue on ealizados en los geopolíme os ob enidos: isicoquímicos (densidad, abso ción de agua, po osidad), mecánicos ( esis encia a comp esión y a lexión), de esis encia al uego y medioambien ales (lixi iación y adioac i idad). Los paneles ab icados han sido com- pa ados con paneles come ciales pa a de e mina las posibilidades de eciclaje de las cenizas olan es pa a la ab icación de nue os p oduc os geopolimé icos con p opiedades aislan es al uego. Los paneles ob enidos pueden se u ilizados pa a la p oducción de pa edes in e io es, con buenas p opiedades ísicas, mecánicas y de esis encia al uego sin ningún p oblema medioambien al. PALABRAS CLAVE: Ceniza olan e; Me acaolín; P opiedades mecánicas; Dis ibución de amaño de po o; Tempe a u a. Copy igh : © 2015 CSIC. This is an open-access a icle dis ibu ed unde he e ms o he C ea i e Commons A ibu ion-Non Comme cial (by-nc) Spain 3.0 License. 2 • Y. Luna-Galiano e al. Ma e iales de Cons ucción 65 (319), July–Sep embe 2015, e059. ISSN-L: 0465-2746. doi: h p://dx.doi.o g/10.3989/mc.2015.06114 LIST OF NOTATION mi is he mass WA is he wa e abso ion RC is he comp essi e s eng h RFL is he lexu al s eng h 1. INTRODUCTION Gene a ion o esidual combus ion p oduc s is a wo ldwide p oblem wi h implica ions in he human heal h, he en i onmen and he indus y. Fly ash is he main coal combus ion p oduc wi h applica ion in many ields, mainly in he cons uc- ion indus y (1) due o he good pozzolanic and cemen i ious p ope ies (2, 3). The quan i ies o ecycled ly ash a e e y small, only 44% o he ash p oduced in Eu ope in 2009 was used (see www. ecoba.com), so i is necessa y o explo e new appli- ca ions o medium/high alue, whe e he ly ash can be used. Geopolyme s a e new ma e ials p oduced in he eac ion be ween a solid aluminosilica e and an ac i- a ing solu ion o alkaline silica e o hyd oxide a ambien empe a u e o a sligh ly high empe a- u e (4). Geopolyme s p esen an eno mous po en- ial as a sou ce o p oduc s wi h a wide spec um o applica ions (5), mainly in he cons uc ion ield whe e geopolyme s a e compe i i e wi h he cemen based p oduc (6). Some o hese p ope ies a e high comp essi e esis ance and high s uc u al in eg i y (7),high le el o esis ance o acid and sal s a ack (7, 8), low pe meabili y (7) and good esis ance o haw- eeze cycles (9, 10). Calcined kaolin has an ele a ed speci ic su ace and a less c ys alini y g ade han he non calcined kaolin (11), so his ma e ial is widely used as sou ce ma e ial in geopolyme (12–18). Me akaolin is used wi h o he ma e ials since me akaolin alone p o- duces a weaken s uc u e (16, 19–24). Howe e , me akaolin is usual in he geopolyme p oduc ion o manu ac u e hyd oce amic compounds, adhesi e and coa ing (6). A i e esis an ma e ial is one ha , o a speci- ied ime and unde condi ions o a s anda d hea in ensi y (25), i will no ail s uc u ally and will no pe mi he side away om he i e o become ho e han a speci ied empe a u e (ambien empe a u e plus 160°C). Some o he comme cial p oduc s used o he mal insula ion o passi e i e p o ec ion in buildings and indus ial ins alla ions ha e a chemi- cal composi ion and chemical p ope ies simila o hose ound in some ash-based p oduc s. Fly ash based geopolyme s a e one o hem. Geopolyme s, in gene al, p esen a low he mal conduc i i y a high empe a u es (24–35) and hey do no emi ed oxic ume when i is hea ed (36), bu he e a e no many esul s abou he beha io o he geopolyme panels when a su ace is subjec ed o a s anda d i e. This pape is based in he s udy o i e esis- ance p ope ies o geopolyme s p epa ed wi h ly ashes and me akaolin p epa ing panel and subjec - ing hem o s anda d i e es , con inuing along he lines o o he s udies by his esea ch g oup (37, 38), ying o sea ch new ways o e-using ly ashes in manu ac u ing new insula ing and i e- e a dan p oduc s o use in i ep oo doo s and i ewalls. Since he ma e ial is composed mainly by a was e, i has been necessa y o speci y any chemical o physical condi ion capable o inducing he elease o po en ially oxic compounds in he en i onmen . Fo his eason, some es ha e been included, which ha e been conduc ed o cha ac e ize en i onmen- ally he ma e ial and some e e ence alues a e p esen ed due o he lack in he Spanish legisla ion. 2. MATERIALS AND METHODS 2.1. Ma e ials Fly ashes (FA) om he combus ion o high quali y pul e ized coal in one o he la ges coal powe plan s in he Sou h o Spain, Los Ba ios (550 MWe), we e used as he main aluminosilica e ma e ial. Me akaolin (MK) is p epa ed om kaolin as i is desc ibed by p e ious esea che s (39). In o de o compa e he di e en p ope ies o geo- polyme s wi h o he comme cial ma e ials, samples o O dina y Po land Cemen (OPC) we e p e- pa ed using comme cial Po land Cemen Type II (CEM II/B-L 32.5 N acco ding o EN 197-1 (40)). The wa e /solid a io o sample o OPC is 0.4. The chemical composi ion, he i eous phase, he bulk densi y and he pe cen age o ma e ial wi h a size highe han 45 µm o he FA, MK and OPC a e shown in Table 1. As can be obse ed in Table 1, acco ding o ASTM C618 (41), FA can be classi ied as class F (pozzolanic ashes). The SiO2 con en o ly ash and me akaolin a e o e 65% and he Al2O3 con en is 19% and 32% in ly ash and me akaolin espec i ely. The i eous phase o FA and MK has been calcu- la ed as i is desc ibed in a wo k o A juan (42). The esul o FA is 72.3% and o MK is 50.2%. Some au ho s (43) men ioned ha he highe he amoun o amo phous phase o he ly ash, he as e he ac i- a ion p ocess and he highe he deg ee o eac ion. A comme cial solu ion o sodium silica e (NaSil) was used as ac i a ing solu ion. The cha ac e is ics a e de ailed in Table 2. 2.2. Geopolyme panel p epa a ion Ou goal was o come up wi h a p oduc com- p ised mainly by ly ashes. The composi ion o he di e en panels is shown in Table 3. These compo- si ions we e selec ed a e a p e ious s udy o he op imal composi ions (44). P ope ies o ly ash and me akaolín based geopolyme panels unde i e esis ance es s • 3 Ma e iales de Cons ucción 65 (319), July–Sep embe 2015, e059. ISSN-L: 0465-2746. doi: h p://dx.doi.o g/10.3989/mc.2015.06114 The solid componen s shown in he p e ious able we e placed in a plane a y mixe and we e mixed un il a homogeneous mix u e was achie ed. Then sodium silica e solu ion was added o he solid mix u e and again was mixed un il a wo kable and hixo opic pas e was ob ained. The solu ion and solid we e mixed du ing 4 minu es app oxima ely. Finally, samples we e ib a ed o 5 minu es in o de o elease bubbles. The eade can e e o Luna e al. (45) o u he de ails. The pas e ob ained was placed in 2 cm hick, 28cm high and 18 cm wide panel moulds. The panels we e aken ou o he moulds a e 24 hou s and le o cu e a ambien empe a u e o 28 days (a e age empe a u e: 20°C; a e age ela i e humidi y: 45%). Smalle cylinde es pieces o di e en shapes and sizes we e used in he physicochemical and mechani- cal es s. A e his cu ing ime, geopolyme samples we e subjec ed o di e en empe a u es, 300, 500 and 700°C du ing 3 hou s and di e en p ope ies we e de e mined. 2.3. Me hods 2.3.1. Physical p ope ies The densi y ( ) o he mo a was measu ed by weigh and olume (dimensions) measu emen s. Th ee specimens o each ype we e es ed. Wa e abso p ion (WA) was measu ed acco ding o Eu opean S anda ds EN 12859 (46). A po osime y s udy has been ca ied ou in o de o analyse he e ec o hese pa ame e in he hea ing beha iou o samples. A me cu y in u- sion po osime e (Mic ome i ics Au opo e IV) wi h a measu ing p essu e ange om 1.02×10−2 o 2.04×102 MPa we e used. The con ac angle was 141°, so he measu able po e size anged om 0.007 o 144 µm. Samples used had he o m o pelle s abou 5 mm in size and mus be d ied, so samples mus be s a ed in an o en a 105°C du - ing 24 hou s. All analysis has been ca ied ou wo imes. Me cu y In usion Po osime y (MIP) is a echnique based on he p og essi e in usion o a non-we ing subs ance like me cu y unde inc eas- ing con olled p essu e. I is ex ensi ely used ac oss a numbe o applica ions o which po osi y is a c i ical pa ame e , including cemen i ious ma e i- als de i ed om Po land cemen . The li e a u e on conc e e and mo a s sugges s ha MIP may no always be highly eliable. Some esea che s ound ha he po es measu ed by MIP applied on cemen i ious ma e ials can be smalle han he po es obse ed wi h SEM (47, 48). Despi e hese limi a- ions, he MIP echnique is gene ally conside ed an app op ia e me hod o analysis o po osime y and a use ul ool o examine op imal dosages and cu ing o compa a i e pu poses. 2.3.2. Mechanical p ope ies The comp essi e s eng h (RC) o he pas es was also e alua ed using a comp essing es machine (Suzpeca , MEM-102/50 ) (ASTM E 761-86 (49)). The comp essi e s eng h es s we e pe o med on 40-mm-high, 35-mm-diame e cylinde s. P isma ic mo a specimens we e es ed in h ee-poin bending up o ailu e a he loading a e o 15mm/min, wi h a span leng h o 100 mm, acco ding o ASTM s anda d es me hod o lex- u al s eng h (RFL) o hyd aulic cemen mo a s (ASTM C 348-02(50)). The es machine used o de e mine he lexu al s eng h is he same used o de e mine he comp essi e s eng h (Suzpeca , MEM-102/50 ), wi h he necessa y equipmen o his es . Two samples we e used o measu e he lexu al s eng h and ou o de e mine he comp essi e s eng h. The a ia ion coe icien s o di e en es we e <1%. Table 1. Chemical composi ion, i eous phase, bulk densi y and pe cen age o ma e ial wi h a size highe han 45 µm o ly ash, me akaolin and o dina y Po land cemen Mois u e (%) Bulk Densi y (kg·m−3) % w >45 mm LOI (%) Vi eous phase (%) Chemical composi ion (% w ) Fe2O3 CaO MgO SiO2 Al2O3 Na2O K2O FA 0.76 2.45 50 5.17 72.3 7.04 2.63 2.31 65.12 19.27 1.32 2.41 MK 1.21 2.40 70 –50.2 0.51 <0.03 0.18 65.17 32.02 0.05 1.29 OPC 0.97 3.1 32 7.05 2.36 6.98 2.97 22.81 5.37 0.21 0.23 Table 2. Cha ac e is ics o sodium silica e solu ion SiO2 (% w ) Na2O (% w ) SiO2/Na2O Densi y (20°C, g/cm3) pH NaSil 27 8 3.42 1.346 11.5 Table 3. Panels Composi ion (w %) Composi ion by mass (% w ) G-FA G-FA-MK FA 70 60 MK – 13 NaSil 30 27 Liquid/Solid weigh a io 0.24 0.21 4 • Y. Luna-Galiano e al. Ma e iales de Cons ucción 65 (319), July–Sep embe 2015, e059. ISSN-L: 0465-2746. doi: h p://dx.doi.o g/10.3989/mc.2015.06114 2.3.3. Fi e insula ing p ope ies The s anda d i e- esis ance es desc ibed in Spanish egula ion EN 1363-1 (51), which is simi- la o o he widely-used in e na ional s anda ds, has been used. To simula e he condi ions o exposu e o i e, he egula ion equi es ha one o he sides o he p o ec i e ma e ial be exposed o hea acco d- ing o a s anda d empe a u e cu e de ined by he equa ion [1]: T=20+345·log10(8 +1) [1] whe e T is he o en empe a u e o he es s (°C) and is he ime (minu es) om he beginning o he es . To s udy he insula ing capaci y o he panels, a special o en was used so ha he moulded panels could be subjec ed o he s anda d i e esis ance es men ioned abo e. This u nace allowed us o eco d he su ace empe a u e o he exposed su - ace (ho su ace, Tin) o he panel by means o an S- ype he mocouple inside he o en, which was used o egula e he empe a u e o he o en by means o a p opo ional con olle in o de o p o- duce he s anda d empe a u e cu e. On he unex- posed su ace (cold su ace, Tou ), he empe a u e was egis e ed by means o a P -100 p obe wi h a s ainless s eel con ac su ace (52). In o de o analyse he insula ing capaci y o he panels in a way simila o ha ecommended by he Spanish s anda ds, he ime necessa y o Tou o each 180°C ( 180) has been conside ed as a e e - ence alue o s udying his p ope y in 20 mm- hick panels. Wi h he aim o measu ing he ene gy abso bed by he di e en ma e ials, we used he di e en- ial scanning calo ime y (DSC) echnique. Thus, 5-mm-diame e , 3-mm- hick samples placed in non- he me ic aluminium con aine s, we e subjec ed o a hea ing p og am o 2°C·min−1 in a TA DSC 2920 Ins umen , om 30 °C o 400 °C, using ni ogen as pu ging gas. The ene gy abso bed by he pas es be ween 100–170°C in he DSC es s (in J·g−1) was ob ained by in eg a ing he a ea unde nea h he peaks in DSC es (53). 2.4. En i onmen al s udy Gi en ha ly ash is a esidual ma e ial, an en i- onmen al s udy has been ca ied ou o cha ac e - ize he p oduc mo e comple ely in o de o make a be e e alua ion abou i s possible uses as cons uc- ion ma e ials. The p oduc s de eloped in he p es- en wo k mus gua an ee a low oxici y le el, which is o en assessed h ough leaching and adiological s udies. The leaching s udy in ol ed subjec ing he ma e- ial o one o he mos commonly used es s o monoli h samples in he was e managemen ield in Eu ope, he NEN 7345 di usion es o ank leaching es (54). The leacha es we e measu ed in he Analy ical Se ices o he Uni e si y o Se ille (CITIUS) using ICP-OES equipmen . By-p oduc s o coal combus ion con ain enhanced concen a ion o he na u al adionu- clides 40K, 226Ra and 232Th and hei decay p oduc s. These adionuclides emi alpha pa icles, be a pa - icles, and gamma ays, and he e o e hey a e a sou ce o ionizing adia ion (55). Exposu e o such adia ion is conside ed o pose a haza d o human heal h. Building p oduc s based on coal ashes a e classi ied by he ele an Eu opean Commission Di ec o a e o Radia ion P o ec ion as ma e ials wi h enhanced adioac i i y (56). The adioac i i y o samples was measu ed in he analy ical se ice o he Uni e si y o Se ille (CITIUS). A well- ype HPGe de ec o om Canbe a wi h a ela i e e i- ciency o 30% and a c ys al olume o 160 cm3 was used. The samples ob ained we e collec ed in o a cylind ical holde and sealed wi h pa a in ilm. Each sample was measu ed o a leas 25 days a e he sample was p epa ed, o es ablish secula equi- lib ium be ween 226Ra and 232Th and hei espec i e adioac i e p ogeny. The 226Ra and 232Th con en s we e measu ed h ough he pho opeaks o hei daugh e s, 214Bi (1.760 MeV) and 208Tl (2.614 MeV), espec i ely, while he 40K con en was measu ed di ec ly ia i s 1.460 MeV peak. 3. RESULTS AND DISCUSSION 3.1. Physical and mechanical p ope ies Table 4 shows some o he physical pa ame- e s o hese ma e ials, as well as he mechanical p ope ies. As i can be seen in Table 4, geopolyme G-FA-MK has a highe po osi y han G-FA. Se e al au ho s (29, 57) used a quan i a i e model based on Mic omechanics o s udy open po osi y and ound ha alkali-ac i a ed ly ash is less po ous (30% / ) han alkali ac i a ed me akaolin (40% / ), and hey we e bo h less po ous han cemen i ious ma e ials such as o dina y Po land cemen . Acco ding o Table 1, he pa icle size dis ibu ion o FA is ine han MK. This hicke g anulome y o me aka- olin a ec s o he po e size dis ibu ion, c ea ing mo e po ous zones be ween non-a acked pa icles. Besides, he e mus be aken in o accoun ha a geo- polyme wi h wo aluminosilica e sou ces can o m a mo e he e ogeneous ma e ial, which can in luence he po osi y and he mechanical p ope ies. Figu e 1 ep esen s he po e size dis ibu- ion o G-FA-MK and G-FA. Bo h geopolyme s show a wide po e dis ibu ion, in all ange o sizes (0.03–100 µm), bu he po e olume in G-FA-MK is highe han in G-FA, mainly in he ange o capilla y P ope ies o ly ash and me akaolín based geopolyme panels unde i e esis ance es s • 5 Ma e iales de Cons ucción 65 (319), July–Sep embe 2015, e059. ISSN-L: 0465-2746. doi: h p://dx.doi.o g/10.3989/mc.2015.06114 po es (0.1–10 µm), po es e e o he space le by he wa e ha does no eac du ing he hyd a ion o cemen (58). As can be seen in Table 4, he geopolyme s G-FA and G-FA-MK a e less dense han he OPC ype II, which is due o he lowe bulk den- si y (MK@FA<OPC) and he hicke pa icle size dis ibu ion (MK>FA>OPC). In any case, he geo- polyme s can be classi ied as high densi y panels (>1100 kg·m−3) in acco dance wi h EN 12859 (46). Rega ding he wa e abso p ion, he esul s a e con- sis en wi h he densi y o samples, since he wa e abso p ion is in e sely p opo ional o he densi y. The mechanical p ope ies measu ed a 28 days in geopolyme s and OPC a e oo shown in Table 4. As can be seen, sample wi h OPC shows he high- es comp essi e s eng h (32.5 MPa) and in e medi- a e alue o lexu al s eng h (6.9 MPa). Rega ding he geopolyme s, he G-FA p esen be e comp es- si e (25.4 MPa) and lexu al (8.3 MPa) s eng h han he G-FA-MK geopolyme (comp essi e s eng h o 14.3 MPa). The comp essi e esis ance dec ease almos a 50%, ha is, me akaolin based geopoly- me s ha e a poo esis an s uc u e. This is he ea- son because he me akaolin is used in gepolyme wi h o he aluminium and silicon sou ce ma e ials (16, 19–23). I mus be aken in o accoun ha he amo phous phase o MK (50.2%) is lowe han he FA (72.3%), so he ac i a ion o he ly ash du - ing he geopolyme iza ion eac ion is slowe (43), wi h he consequen lowe comp ession s eng h. Besides, a ma e ial wi h g ea e po osi y p oduces ewe con ac a eas be ween pa icles and inc easing s ess and c ack p opaga ion (38). 3.2. Fi e insula ing p ope ies The i e insula ing capaci y o bo h geopolyme s and OPC a e showed in Figu e 2. When he su ace o a po ous medium wi h wa e con en in i s di e en o ms ( ee, adso bed, c ys al- ized, e c.) is exposed o i e (high empe a u es), pa o he wa e e apo a es, which gene a es o e p essu e in he po es o he ma e ial. Consequen ly, he e apo- a ed wa e is anspo ed om he i e exposed su - ace as a esul o a p essu e g adien o he in e io o he ma e ial, which is coole , and he wa e condenses again. A liquid ilm is hus o med which is p og es- si ely displaced owa d he unexposed pa . Thus, he wa e con en o he ma e ial causes an e apo a ion pla eau in he empe a u e p o ile o he unexposed side ( empe a u e s. ime) since he p essu e g adien s do no signi ican ly in luence he sa u a ion p essu e o he liquid wa e in he in e phase (37). The e o e, a highe e apo a ion pla eau p oduces g ea e insula - ing capaci y (51). The o he ac o ha a ec o he insula ing capaci y is he slope o he cu e (be o e and a e he e apo a ion pla eau), which is p opo - ional o he he mal di usi i y o he ma e ial (37). As i can be obse ed in Figu e 2, he beha iou o he G-FA panel is di e en o he G-FA-MK panel. Fi s ly, he e apo a ion pla eau o he geopolyme wi h MK is sho e and i happened a highe em- pe a u e han he geopolyme wi hou MK. In o de o unde s and his beha iou , he ene gy abso bed by di e en ial scanning calo ime y (DSC) echnique is de e mined o he h ee mix u es (OPC, G-FA and G-FA-MK) and ep esen ed in Figu e 3. The a ea unde he peak o he DSC cu e o he geopolyme G-FA-MK is lowe han he geo- polyme G-FA, be ween 50 and 200°C. This is in acco dance wi h he sho e e apo a ion pla eau shown by G-FA-MK (Figu e 2). The abso p ion o ene gy by he pas es esponds o he con en and he chemical o m in which wa e is p esen in hem ( ee, adso bed, c ys alized, e c.), and he e apo a- ion pla eau is p opo ional o his a ea (53). The G-FA-MK geopolyme has a lowe wa e con en han he G-FA geopolyme , so i s a ea (unde he DSC cu e) is smalle . The peak o DSC cu e o G-FA-MK is sligh ly mo e o high empe a u es Table 4. Physical and mechanical p ope ies *Po osi y (mL·g−1) Densi y (kg·m−3) WA (%) RC (MPa) RFL (MPa) G-FA 0.0264 1541 16.2 25.4 8.3 G-FA-MK 0.0840 1502 16.9 14.3 6.1 OPC 1782 14.0 32.5 6.9 *These alue o po osi y a e calcula ed wi h geopolyme d yed a 105°C Figu e 1. Po e size dis ibu ion o G-FA and G-FA-MK geopolyme . 6 • Y. Luna-Galiano e al. Ma e iales de Cons ucción 65 (319), July–Sep embe 2015, e059. ISSN-L: 0465-2746. doi: h p://dx.doi.o g/10.3989/mc.2015.06114 ega ding he G-FA cu e, possibly due o he di - e en o ms o wa e in he geopolyme s wi h and wi hou MK and i is ela ed wi h he change o he e apo a ion pla eau empe a u e in Figu e 2. The OPC p esen s a g ea e a ea in DSC es and i s e apo a ion pla eau is longe oo. Secondly, o he aspec o ake in o accoun in Figu e2 is he change o slope a e he e apo a- ion pla eau in some ma e ials, as G-FA-MK and OPC. Howe e , he G-FA does no p esen his as inc emen . In his geopolyme he slope o he cu e dec eases along he ime (a e he e apo a ion pla- eau). The he mal di usi i y a e he e apo a ion pla eau o di e en ma e ials can be compa ed in Figu e 3, i he hea low abso bed in DSC es inc ease, he he mal di usi i y o he ma e ial dec eases, and he slope a e he e apo a ion pla- eau will be smalle , inc easing he insula ing capac- i y (53), his is he eason because G-FA p esen a simila i e insula ing capaci y han OPC, al hough G-FA p esen s a lowe e apo a ion pla eau. The he mal di usi i y o he compounds p oduced du ing he hyd a ion in he geopolyme iza ion eac- ion is lowe han OPC compounds (37). Besides, i mus be emphasized he no emission o gas and oxic umes du ing he i e esis ance es . All he composi ions kep he in eg i y o he panel a e he i e es (Figu e 4). 3.3. S udy o he e olu ion o mass, po osi y and comp essi e s eng h wi h he empe a u e This s udy has been ca ied ou in o de o assess he e olu ion o densi y, comp essi e s eng h and po osi y du ing he exposu e a high empe a u es. Samples we e placed in an o en a 105, 300, 500 and 700 °C du ing h ee hou s. A e his ime, samples we e subjec ed o a slow cooling. Weigh and comp essi e s eng h we e measu ed a e he es ( ha is, a a empe a u e T) (mT and RCT), he alues we e compa ed wi h he same pa ame e s o one sample wi hou he mal ea men ( ha is, a 20 °C) (m20 and RC20) and ela i e alue we e calcula ed. Po osi y is de e mined oo a di e en empe a u es. 3.3.1. Mass loss Figu e 5 shows he e olu ion o he ela i e esid- ual mass (mT/m20) wi h he empe a u e o geopoly- me G-FA and G-FA-MK. Figu e 2. Fi e insula ing o he di e en geopolyme s p oduc s. Figu e 3. DSC o o he di e en geopolyme s p oduc s. Figu e 4. Pho og aph o G-FA a e he i e es . P ope ies o ly ash and me akaolín based geopolyme panels unde i e esis ance es s • 7 Ma e iales de Cons ucción 65 (319), July–Sep embe 2015, e059. ISSN-L: 0465-2746. doi: h p://dx.doi.o g/10.3989/mc.2015.06114 The end o bo h geopolyme s (wi h o wi h- ou MK) is iden ical. The e is a con inuous loss o weigh up 700°C. The weigh loss a 105°C is p incipally due o he ee wa e , and i is lowe in G-FA-MK han in G-FA. This is due o he mois- u e con en since mois u e con en in G-FA-MK (1.9%) is less han in G-FA (2.9%). In he ange 105–300°C, he loss o mass is again lowe in geo- polyme G-FA-MK. As i can be seen in he i e esis ance esul s, Figu e 2, he abso bed wa e con- en o G-FA-MK is less han G-FA ( he e apo a- ion pla eau o he geopolyme wi h MK is sho e ) in a empe a u e in he ange o 50–200°C, as i is showed in DSC igu e oo (Figu e3). This is he ea- son because he mass loss a 300°C o G-FA-MK is less han in G-FA. Be ween 300 and 700°C, he mass subsequen ly dec eased due o dehyd a ion o wa e om aluminosilica es gel, bu i is e y simi- la in bo h geopolyme s (27). In any case, sample p epa ed wi h OPC p esen he highes loss o mass o all (20% o loss), which can indica e he high in eg i y o geopolyme s a e he exposu e a high empe a u e. 3.3.2. Po osi y and po e size dis ibu ion Table 5 shows he e olu ion o po osi y wi h he empe a u e. As can be seen in Table 5, an inc emen in he po osi y is occu ed du ing he hea ing o samples be ween 105 and 700°C. This inc emen is deepe in geopolyme G-FA han in geopolyme G-FA-MK. In o de o unde s and his beha iou , he cu e Log-di e encial in usion olume e sus po e size diame e is ep esen ed. Po e size dis ibu ion o geopolyme wi hou me akaolin (G-FA) is showed in Figu e 6. This geopolyme shows a sligh inc emen o he po osi y in he ange 105–300°C, om 0.0264mL·g−1 a 105°C o 0.0688 mL·g−1 a 300°C (Table 5) ha is co ela ed wi h he g aph Figu e 6 since in his igu e geopolyme a 300°C show a sligh inc emen o he in usion olume in he ange o 0.5–4 µm (capilla y po es (0.2–3 µm)) o po e size when i is compa ed wi h he geopolyme a 105°C. The highes inc e- men o po osi y is ob ained in he ange o empe - a u e 300–500°C, om 0.0688 mL·g−1 a 300°C o 0.2324 mL·g−1 a 500°C (an inc emen o 70%). In his in e al, a change in po e s uc u e is obse ed since a high inc emen o po e olume is p esen ed by he geopolyme G-FA, wi h a big peak be ween 0.5 o 4 µm, ha is, wi h an inc emen o numbe o po es du ing hea ing since 300 o 500 °C. The inc emen o po e olume in he ange 300–500°C is possibly due o a subs an ial sh inkage occu ed as he empe a u e inc ease abo e o 300°C, as i is commen ed by Ro nanik (33). This au ho indi- ca ed ha he d as ic sh inkage is ela ed o he he mal damage sus ained by he geopolyme pas e. Du ing hea ing be ween 500 o 700°C, o he sligh inc emen o po osi y is p oduced (0.2324mL·g−1 a 500°C o 0.2672 mL·g−1 a 700°C). As i can be seen in Figu e 6, a sligh change in po e dis ibu ion occu ed be ween 500 and 700 °C since a shi o he highe po e size is obse ed, since 0.5–4 µm o Figu e 5. E olu ion o ela i e esidual mass wi h he empe a u e. Table 5. E olu ion o po osi y wi h he empe a u e Tempe a u e (°C) Po osi y (mL·g−1) 105 300 500 700 G-FA 0.0264 0.0688 0.2324 0.2672 G-FA-MK 0.0840 0.0850 0.3044 0.3055 8 • Y. Luna-Galiano e al. Ma e iales de Cons ucción 65 (319), July–Sep embe 2015, e059. ISSN-L: 0465-2746. doi: h p://dx.doi.o g/10.3989/mc.2015.06114 1–7 µm, owa ds la ge capilla y po es (1–10μm). A 500°C, he capilla y po es domina ed he s uc u e o ma ix bu a 700°C, he s uc u e is domina ed by la ge po es. Po e size dis ibu ion o geopolyme wi h me akaolin (G-FA-MK) is ep esen ed in Figu e 7. This g aph shows a sligh ly di e en beha iou han he geopolyme wi hou me akaolin. Fi s ly, he e no exis di e ences be ween he po os- i y a 105 and 300°C wi h a alue o po osi y o 0.084mL·g−1 a 105°C and 0.085 mL·g−1 a 300°C (Table 5) and in Figu e 7 he cu es o po e size dis ibu ion is simila . In he ange 300–500°C, he po osi y inc ease, om 0.085 mL·g−1 a 300°C o 0.3044 mL·g−1 a 500 °C (an inc emen o 72.1%, simila han he geopolyme G-FA) p oducing an inc emen o he po e olume (Figu e 7), wi h a la ge peak be ween 0.2 o 3 µm, zone o capilla y po es. Again an inc emen o numbe o po es is p oduce du ing hea ing since 300 o 500°C. Du ing hea ing be ween 500 o 700°C, he e a e no di e - ences in he po osi y (0.3044 mL·g−1 a 500 °C o 0,3055mL·g−1 a 700°C), wi h li le di e ences in he po e size dis ibu ion o he s uc u e o ma ix. Figu e 6. Geopolyme G-FA. E olu ion o po es size dis ibu ion wi h he empe a u e. Figu e 7. Geopolyme G-FA-MK. E olu ion o po es size dis ibu ion wi h he empe a u e. P ope ies o ly ash and me akaolín based geopolyme panels unde i e esis ance es s • 9 Ma e iales de Cons ucción 65 (319), July–Sep embe 2015, e059. ISSN-L: 0465-2746. doi: h p://dx.doi.o g/10.3989/mc.2015.06114 Ha ing in o accoun he e olu ion o po osi y wi h he empe a u e o bo h geopolyme s, de ailed in Table 5, geopolyme wi hou me akaolin shows a lowe po osi y han geopolyme wi h me akaolin. As can be seen in Figu es 6 and 7, he geopolyme G-FA shows a shi o po e size dis ibu ion o he la ge po es, al hough he po e size dis ibu ion o geopolyme G-FA-MK p esen high amoun o po e in he ange 0.06–3 µm a 300–500°C, which can explain he highe alues o po osi y o his las geopolyme . 3.3.3. Comp essi e s eng h Figu e 8 shows he e olu ion o he ela i e esid- ual comp essi e s eng h (RCT/RC20) a e he expo- su e o di e en empe a u es. Figu e 8 depic s an inc ease-dec ease end simila o ha shown in p e ious s udies by o he au ho s (27–30). The comp essi e s eng h is inc eased un il 300 °C, hese inc easing is p obably a ibu ed o p omo ion o polycondensa ion be ween chain-like geopolyme gels (32). The geopolyme s a ain hei maximum s eng h a 300 °C (21.8 MPa o G-FA-MK and 33.5 MPa o G-FA). Subsequen ly, he comp essi e s eng h g adually dec eased a highe empe a u es. This phenomenon is ela ed o he la ge inc ease in po osi y be ween 300° and 500°C, as i was shown in Table 5. As can be seen, po osi y o bo h geopolyme s inc eases wi h he empe a u e, om 105 °C o 700 °C. The highes po osi y inc emen is in he ange o 300 o 500°C, ange in which comp es- si e s eng h shows he highes dec emen , mainly in geopolyme G-FA-MK. Howe e , in he ange 500 o 700°C, he inc emen o po osi y is lowe han in he ange 300 o 500°C, p oducing a lowe diminu ion o comp essi e s eng h. This beha - iou is oo obse ed by o he esea che (33), bu in alkaline ac i a ed slags. Figu e 8 shows clea ly ha geopolyme s ha e highe esidual comp essi e s eng hs han OPC specimens (21.1 MPa o G-FA, 14.88 MPa o G-FA-MK a 500 °C and 18.57 MPa o G-FA, 14.05 MPa o G-FA-MK a 700°C), OPC speci- mens d opped conside ably a high empe a u es (29MPa a 105°C, 17 MPa a 300°C, and inally he OPC sample was spalled a 500°C). This s eng h de e io a ion o OPC is a ibu ed o he Ca(OH)2 decomposi ion ha occu s a abou 400°C, which p oduce a spalling p ocess (34). 3.4. En i onmen al s udy 3.4.1. NEN 7345 ank leaching es Gi en he sca ci y o s anda ds exis ing in Spain ega ding he euse o seconda y ma e ials in he cons uc ion sec o , he Du ch egula ions s a ed in he Dec ee on Soil Quali y (DSQ) (59) ha e also been conside ed. The DSQ con ains ules ela ed o he use o di e en ma e ials in cons uc ion aimed a p e en ing pollu ion o he soil and su - ace wa e s. Since he geopolyme s s udied a e used as mono- li hs, i seems easonable o pay mo e a en ion o he leaching o he con o med p oduc . Thus, Table 6 shows he esul s o he leachabili y s udy ca ied ou acco ding o he NEN 7345 di usion es o es pieces aken om he panel. The NEN 7345 ank Figu e 8. E olu ion o ela i e esidual comp essi e s eng h wi h he empe a u e.