Empirical definition of effective water / cement ratio in mortars with recycled aggregate depending on the absorption

P oceedings o he II In e na ional and IV Na ional Cong ess on Sus ainable Cons uc ion and Eco- E icien Solu ions 505 EMPIRICAL DEFINITION OF EFFECTIVE WATER / CEMENT RATIO IN MORTARS WITH RECYCLED AGGREGATE DEPENDING ON THE ABSORPTION 1 *Velay-Lizancos Mª Mi ian; 1 Ma ínez-Lage Isabel; 1 Vázquez-He e o C is ina; 1 Vázquez-Bu go Pablo 1 Uni e sidad de A Co uña. Escuela Técnica Supe io de Caminos, Canales y pue os Campus de El iña S/N 15071. A Co uña - España e-mail: *m. [email protected] ABSTRACT The use o ecycled agg ega es om cons uc ion and demoli ion was es o he manu ac u e o mo a s and conc e es is a subjec o g ea in e es om he poin o iew o sus ainable cons uc ion since i can educe he exploi a ion o qua ies eplacing na u al agg ega e by ecycled agg ega e and i can educe he olume o was es in land ills. In o de o s udy he in luence o ecycled agg ega e on conc e e and mo a s eng h, he e ec i e wa e /cemen a io mus be he same in conc e es o mo a s compa ed. The e ec i e wa e /cemen a io is de ined as he amoun o wa e a ailable o eac wi h he cemen o he mix u e. Disc epancies among au ho s a ise in he de ini ion o how much is he amoun o a ailable wa e , which depends on he abso p ion and mois u e o he agg ega es a he ime o he ba ch. The e o e, in his esea ch, an expe imen al s udy is de eloped empi ically o ind he amoun o wa e which eac s wi h he cemen mo a in a ious mix u es wi h di e en a ios o ecycled agg ega e depending on he abso p ion o he agg ega es. Subsequen ly, he ela ions be ween he amoun o wa e which doesn’ eac wi h he cemen and agg ega e abso p ion o each o he mix u es we e analyzed. Finally, a de ini ion o he e ec i e wa e /cemen a io depending on abso p ion is p oposed, based on he empi ical s udy de eloped. Keywo ds: ecycled agg ega e, e ec i e wa e /cemen a io, CDW, abso p ion, mo a Chap e II – The cons uc ion and demoli ion was e, i s ecycling and euse oppo uni ies 506 1.- In oduc ion The e m “e ec i e wa e /cemen a io” has a clea de ini ion: “To al amoun o wa e ha eac s wi h cemen , di ided by he amoun o cemen “. The p oblem appea s when de ining “ he amoun o wa e ha eac s wi h cemen ”. The p esence o agg ega es, which abso b pa o he wa e , causes ha pa o he wa e canno eac wi h cemen and he e o e, he e ec i e wa e /cemen a io is lowe han he eal wa e /cemen a io. When ecycled agg ega es u iliza ion, his educ ion in he e ec i e wa e /cemen a io is conside able, due o he high abso p ion o he ecycled agg ega es and i has o be aken in o conside a ion. I i we e possible o ind he amoun o wa e no eac ing due o he agg ega es abso p ion, calcula ing he e ec i e wa e /cemen a io would be some hing immedia e. The use o ecycled agg ega es coming om cons uc ion and demoli ion was es o make mo a and conc e e is e y in e es ing om he poin o iew o sus ainable cons uc ion. As well as educing qua ies exploi a ion eplacing na u al agg ega es by ecycled agg ega es, he amoun o was es placed in ips is also educed. One way o s udying de in luence o ecycled agg ega es in mo a s and conc e e is es ing specimens made wi h di e en a ios o ecycled agg ega es and compa e hem wi h he e e ence dosage wi h a eplacemen a io o 0% in mo a and conc e e. In o de o make hese mo a s and conc e es compa able, he only ac o ha can di e among hem mus be he eplacemen a io. I is well known ha he w/c ela ion o mo e speci ically, e ec i e w/c has in luence on he s eng h esul s. In o de o compa e conc e es and mo a s wi h di e en a ios, i is necessa y ha he w/c ela ion will be cons an , no being a new a iable o conside . Consequen ly, i is eally impo an o know he e ec i e w/c acco ding o he agg ega es abso p ion, in o de o make he necessa y adjus men s wi h he aim o ha ing he same w/c ela ion in e e y specimen. Disc epancies a ise in de ining wha amoun o wa e ha ecycled agg ega es abso b and he e o e is no a ailable o eac wi h he cemen . Some au ho s ecommend p esa u a ing he agg ega es [1, 2, 3, 4], o he s ecommend hei imme sion in wa e o 30 minu es [5] and o 10 minu es [6, 7] wi h he aim o non- abso bing mo e wa e . Among he au ho s who ecommend adding mo e wa e du ing de conc e e p oduc ion, he e is no an ag eemen abou his amoun , some o hem say ha he bes idea is adding 100% o abso p ion capaci y [8], o he s 90% [9, 10], 85% [11], 80% [12] and 70% [13]. 2.- Objec i e o he s udy The objec i e o his s udy is o ge a ela ion be ween he abso p ion o he agg ega es and he e ec i e w/c a io based on an expe imen al de elopmen sea ching o ela ions be ween he w/c a io and he mic owa es equencies in mo a s whose agg ega es ha e a di e en abso p ion. Ge ing, in his way, a de ini ion o he e ec i e w/c a io based on he abso p ion o he agg ega es u ilized o make mo a s, since he e a e disc epancies among au ho s abou he in luence o he abso p ion o ecycled agg ega es in he e ec i e w/c a io and he de ini ion o he adjus men o wa e necessa y o ge dosages wi h di e en a ios o ecycled agg ega es bu wi h he same wa e /cemen a io. In o de o compa e he esul s o mo a s eng hs wi h di e en a ios o ecycled agg ega es and measu e he in luence o ecycled agg ega es in s eng h is necessa y ha e e y dosage has he same wa e /cemen a io. O he wise, his ac o would a ec o s eng hs and i could no be said ha he di e ences in s eng hs a e only caused by an inc emen in he ecycled agg ega e. I is impo an o men ion ha P oceedings o he II In e na ional and IV Na ional Cong ess on Sus ainable Cons uc ion and Eco- E icien Solu ions 507 ge ing he same e ec i e w/c a io is no equi alen o ge he same consis ence o he mix u e. 3.- Basis o his s udy and me hodology I is known ha he ela ion o he amoun o wa e ha eac s wi h cemen in a mix u e is delimi ed be ween he amoun o wa e added and he di e ence be ween ha amoun and he amoun o wa e ha he agg ega es can abso b. In o he wo ds: Wa e ha eac s = wa e added – α * abso p ion capaci y o agg ega es (1) Being α a alue be ween ze o and one. I α had a ze o alue, i would be assumed ha he whole wa e added would be a ailable o eac wi h he cemen . I α had he alue 1, i would be assumed ha he supposi ion ha all he wa e ha agg ega es can abso b is abso bed and he e o e, i is no a ailable o eac wi h he cemen . In o he wo ds, i would be equi alen o suppose ha in o de o ha e he same w/c ela ion be ween wo conc e es o mo a s wi h di e en eplacemen a ios, i would be necessa y o do and adjus men inc easing he abso p ion o al amoun o wa e (adjus men o 100% o he abso p ion o he ecycled agg ega es). Due o he amoun o cemen is cons an , di iding by he amoun o cemen , i esul s: e ec i e w/c = eal w/c - α *(abso p ion capaci y / cemen ) (2) On he o he hand, he e is a ela ion be ween he mic owa es equency and he w/c a io. In ac , he e is a de ice called “cemen ome e ” ha es ima es he w/c a io, p e ious calib a ion, h ough he ela ion be ween he w/c a io and he mic owa es equency. This de ice is calib a ed and designed o measu e eal w/c a ios in ce ain kinds o cemen and using na u al agg ega es (whose di e ence in abso p ion is minimum, nea ly negligible, so he eal w/c and he e ec i e w/c ela ions a e iden ical). On he basis o he exis ence o an unknown ela ion be ween he mic owa es equency and he e ec i e w/c a io he i s pa o his s udy is de eloped. I he e was a na u al agg ega e wi h a 0% abso p ion, he whole added wa e would eac wi h he cemen , ha is, he eal w/c a io would be he same han he e ec i e w/c a io. Measu ing he equency ha co esponds o se e al e ec i e w/c a ios o a mo a made wi h ze o abso p ion agg ega es, i could be ound a unc ion o he alue o he e ec i e w/c a io acco ding o he alue o he equency measu ed. Nex s ep would be calcula ing he e ec i e w/c ela ion wi h he p e ious exp ession in mo a s whose abso p ions we e changing; o ins ance, p ese ing he dosage and eplacing only na u al agg ega e by ecycled agg ega e. The e is no a na u al agg ega e wi h ze o abso p ion, so i is no possible o ind an exac cu e ha ela es equency o he e ec i e w/c a io. Howe e , i is possible o ind an uppe and lowe bound whe e i is known ha he co ela ion cu e will be, as i will be explained in he nex pa ag aphs. I is known ha he e ec i e w/c a io is delimi ed be ween he alue o he eal w/c a io (wi hou conside ing he in luence o he agg ega es abso p ion) and a minimum alue o he e ec i e w/c a io. This “minimum alue o w/c” is he esul o assuming ha he o al amoun o wa e ha he agg ega es could abso b does no eac wi h he cemen . In o he wo ds, in o de o calcula e he w/c a io, he amoun o wa e u ilized o calcula e de w/c a io and he abso p ion wa e o he agg ega es a e added o he mix u e. Chap e II – The cons uc ion and demoli ion was e, i s ecycling and euse oppo uni ies 508  ⁄= (!"!#!$ ⁄, eal$ ⁄) Using a na u al agg ega e, wi h a low abso p ion, i is possible o ind an uppe and lowe bound, calcula ing he cu es ha ela e he w/c o he equency; one o he cu es ela es eal w/c o equency and he o he cu e ela es w/c co ec ing abso p ion wa e . The e ec i e w/c a io will be be ween hese cu es. In his way, o each equency, a co esponding e ec i e w/c a io is delimi ed in a small in e al. The nex g aph (Fig. 1) shows he uppe and lowe bound o e ec i e w/c acco ding o he measu ed equency in esh mo a , using d y na u al agg ega es in he mix u e. Fig. 1 “Uppe and lowe bound o e ec i e w/c a io acco ding o he equency”. In o de o ind be ween he e ec i e w/c a io and he abso p ion, mo a s a e s udied wi h he same dosage, a ying only he a e o ecycled agg ega e ha is eplaced by na u al agg ega e. In his way, mo a s whose agg ega es ha e a di e en abso p ion capaci y will be ob ained. The objec i e o his s udy is o ind and exp ession ha es ima es he e ec i e w/c ela ion acco ding o he agg ega es abso p ion, o in o he way, he in luence o he agg ega es abso p ion in he e ec i e w/c. In o de o ob ain i , once he uppe and lowe bounds o he e ec i e w/c a io ha e been calcula ed in a e e ence mo a (Fig. 1), he me hodology will be he ollowing: - Mo a s wi h di e en eplacemen a ios will be es ed. In e e y es , equencies co esponding o se e al w/c ela ions will be measu ed. - Wi h he same exp essions o es ima ing he e ec i e w/c ela ion o he uppe and lowe bound, he minimum and maximum co esponding e ec i e w/c ela ion will be ound o e e y eal w/c ela ion in e e y dosage. In o he wo ds, in each alue o he eal w/c ela ion ( om 0.35 o 0.65 wi h incensemen s o 0.05) in e e y dosage, an in e al o he co esponding e ec i e w/c ela ion is ob ained. Fo each alue o eal w/c, we will ha e a minimum and maximum alue o e ec i e w/c. - O he way o calcula ing he w/c e ec i e a io is wi h he o mula 2: E ec i e w/c = eal w/c – α *(abso p ion capaci y / cemen ) (2) y = -0.0002183x + 0.6119708 y = -0.0002149x + 0.5858513 0.000 0.100 0.200 0.300 0.400 0.500 0.600 0 500 1000 1500 w/c a io F equency (Hz) w/c a io wi hou aking in o accoun he abso p ion w/c a io aking in o accoun he in luence o he 100% o he abso p ion P oceedings o he II In e na ional and IV Na ional Cong ess on Sus ainable Cons uc ion and Eco- E icien Solu ions 509 - Taken o be ue he alue o he lowe bound o w/c o each mix u e (and including in each mix u e i s co esponding abso p ion capaci y), he alue o α ha minimises he oo mean squa ed e o o he es ima ions o e ec i e w/c is calcula ed acco ding o he o mula 2. - This p ocess is epea ed eigh imes, conside ing he alues calcula ed in he p e ious uppe and lowe bound as eal alues. The co esponding alue o α ha minimises he oo mean squa ed e o be ween he alues calcula ed acco ding o he o mula 2 and he expe imen al alues o he equency measu emen s using he uppe bound is calcula ed. 4.-De elopmen o he expe imen al campaign and analysis o esul s Once he uppe and lowe bound ha co ela es he equencies wi h he e ec i e w/c ela ion ha e been ound, mo a s wi h eplacemen a ios o 25%, 50%, 75% and 100% o na u al agg ega es by ecycled agg ega es a e s udied. The cemen /sand dosage is 1:3, because o ha , he quan i ies o cemen , na u al sand and ecycled sand a e: Replacemen a e 0% 25% 50% 75% 100% Cemen (g) 450 450 450 450 450 Na u al sand (g) 1350 1012.5 675 337.5 --- Recycled sand (g) --- 337.5 675 1012.5 1350 Table 1 “Dosages” All he agg ega es will be added d y (wi h ze o mois u e). The na u al agg ega e has an abso p ion o 0.19% and he ecycled agg ega e has an abso p ion o 6.43%. As he eplacemen a e inc eases, he amoun o wa e ha he agg ega es can abso b is highe , since he ecycled agg ega es ha e a highe abso p ion. The maximum amoun o wa e ha he agg ega es can abso b in each mo a s udied is shown in he nex able: Replacemen a e 0% 25% 50% 75% 100% Wa e o sa u a e na u al sand (g) 2.6 1.9 1.3 0.6 0.0 Wa e o sa u a e ecycled agg ega e (g) 0.0 22.7 45.4 68.1 90.9 To al abso p ion capaci y (g) 2.6 24.6 46.7 68.8 90.9 To al abso p ion capaci y / cemen 0.006 0.062 0.117 0.172 0.227 Table 2 “Maximum abso p ion capaci y o he u ilized agg ega es di ided by he cemen added” Fo each eplacemen a e, he nex s eps a e ollowed: - Fo each dosage, a mix u e is made. Tha mix u e s a s wi h a low eal w/c ela ion, a ound 0.35 (in same dosages, he eal w/c has o be highe due o he high abso p ion o he agg ega es p oduces a non-homogeneous mix u e because i does no ha e he minimum amoun o wa e o o m a pas e. - Mo e han 12 measu emen s o equency a e made o he i s eal w/c a io. The mean equency co esponding o each eal w/c a io is ound. Chap e II – The cons uc ion and demoli ion was e, i s ecycling and euse oppo uni ies 510 - The necessa y wa e is added o each he ollowing eal w/c a io, inc easing he w/c a io in 0.05 and he s ep o measu ing he equency and calcula ing he mean 12 imes is epea ed. This p ocess is epea ed e e y possible ime un il he mix u e has an excess o wa e and i is oo liquid. In o he wo ds, he mean equency co esponding o each eal w/c ela ion is measu ed, om he lowes eal w/c o he highes , wi h inc eases o 0.05. (See able 3) - The alue o he e ec i e w/c a io co esponding o ha equency is calcula ed h ough o mulas ha delimi he uppe and lowe bound o he e ec i e w/c a io calcula ed p e iously. In his way, an in e al wi h he e ec i e w/c a io o each equency is ob ained. Values a e shown on able 3. P oceedings o he II In e na ional and IV Na ional Cong ess on Sus ainable Cons uc ion and Eco- E icien Solu ions 511 Real w/c Mean F equency E ec i e w/c lowe bound E ec i e w/c uppe bound MORTAR WITH A 25% REPLACEMENT OF R.A. 0,375 1194,25 0,33 0,35 0,400 1056,00 0,36 0,38 0,425 970,75 0,38 0,40 0,450 898,50 0,39 0,42 0,475 742,88 0,43 0,45 0,500 649,75 0,45 0,47 0,525 594,25 0,46 0,48 MORTAR WITH A 50% REPLACEMENT OF R.A. 0,400 1197 0,33 0,35 0,425 1177 0,33 0,36 0,450 1095 0,35 0,37 0,475 945 0,38 0,41 0,500 913 0,39 0,41 0,525 725 0,43 0,45 0,550 621 0,45 0,48 MORTAR WITH A 75% REPLACEMENT OF R.A. 0,450 1191 0,33 0,35 0,475 1093 0,35 0,37 0,500 1001 0,37 0,39 0,525 911 0,39 0,41 0,550 813 0,41 0,43 0,575 753 0,42 0,45 0,600 639 0,45 0,47 MORTAR WITH A 100% REPLACEMENT OF R.A. 0,475 1211 0,33 0,35 0,500 1162 0,34 0,36 0,525 1071 0,36 0,38 0,550 981 0,38 0,40 0,575 899 0,39 0,42 0,600 771 0,42 0,44 0,625 690 0,44 0,46 Table 3 “Measu ed mean equencies co esponding o each eal w/c a io and i s co esponding e ec i e w/c es ima ed acco ding o limi unc ions o uppe and lowe bound” - In Table 3, alues o eal w/c, mean equency, e ec i e w/c lowe bound, e ec i e w/c uppe bound a e shown. - Da a P ocessing: Fi s ly, da a o he w/c lowe bound will be p ocessed. Cu es co ela ing eal w/c and e ec i e w/c in i s minimum bound a e shown. (Figu e 1) Chap e II – The cons uc ion and demoli ion was e, i s ecycling and euse oppo uni ies 512 Fig. 2 “Cu es o eal w/c a io s e ec i e w/c a io, calcula ed wi h lowe bound o calib a ed cu es” - As can be seen in Figu e 2, a ela ion be ween he w/c e ec i e lowe bound and he eal w/c has been ob ained. Ne e heless, as i has been said p e iously, i is possible o es ima e he e ec i e w/c ela ion wi h he o mula 2, acco ding o he abso p ion capaci y o he agg ega es E ec i e w/c = eal w/c – α *(abso p ion capaci y / cemen ) (2) - Since we know he alue o he lowe bound o he e ec i e w/c a io co esponding o each eal w/c a io and he abso p ion capaci y is a da a oo (See able 2). The only unknown da a is he alue o he pa ame e α, whose alue will be be ween 0 and 1. - The alue o α ha minimises he o al oo mean squa ed e o o he whole alues o e ec i e w/c es ima ed o e e y dosage acco ding o he o mula 2, wi h he minimum squa ed me hod is ound. In o he wo ds, we sea ch o he alue o α ha es ima es he e ec i e w/c ela ion calcula ed acco ding o he agg ega es abso p ion (2) and will be simila o he calcula ed expe imen ally wi h he lowe bound ha ela es equency wi h e ec i e w/c ela ion (Fig. 1); so ha his alue o α minimises he o al oo mean squa ed e o o he es ima ions o e ec i e w/c in acco dance wi h he abso p ion. - In his way, he ela ion be ween he e ec i e w/c a io lowe bound and he agg ega es abso p ion is ound, since he alue o α mul iplied by 100 is he pe cen age o abso p ion wa e necessa y o add in o de o adjus he wa e wi h he aim o ha ing he same e ec i e w/c ela ion. The alue o α ha minimises he oo mean squa ed e o o he e ec i e w/c a io lowe bound is 0.7775; in o he wo ds, i would be necessa y o do an adjus men o he w/c adding a 77.75% o agg ega es abso p ion wa e o he eal wa e . (See able 4) 0.30 0.35 0.40 0.45 0.50 0.55 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 E ec i e w/c a io eal w/c a io 25% 50% 75% 100% P oceedings o he II In e na ional and IV Na ional Cong ess on Sus ainable Cons uc ion and Eco- E icien Solu ions 513 Real w/c Mean equency E ec i e w/c a io (Calcula ed lowe bound, acco ding o he equency) E ec i e w/c es ima ed acco ding he abso p ion (Calcula ed wi h o mula 2) Di e ence be ween es ima ed w/c and e ec i e w/c lowe bound MORTAR WITH A 25% REPLACEMENT OF R.A. 0,375 1194 0,33 0,33 -0,0021 0,400 1056 0,36 0,35 -0,0068 0,425 971 0,38 0,38 -0,0001 0,450 899 0,39 0,40 0,0094 0,475 743 0,43 0,43 0,0009 0,500 650 0,45 0,45 0,0059 0,525 594 0,46 0,48 0,0190 MORTAR WITH A 50% REPLACEMENT OF R.A. 0,400 1197 0,33 0,31 -0,0194 0,425 1177 0,33 0,33 0,0013 0,450 1095 0,35 0,36 0,0087 0,475 945 0,38 0,38 0,0014 0,500 913 0,39 0,41 0,0196 0,525 725 0,43 0,43 0,0042 0,550 621 0,45 0,46 0,0068 MORTAR WITH A 75% REPLACEMENT OF R.A. 0,450 1191 0,33 0,32 -0,0136 0,475 1093 0,35 0,34 -0,0097 0,500 1001 0,37 0,37 -0,0044 0,525 911 0,39 0,39 0,0012 0,550 813 0,41 0,42 0,0052 0,575 753 0,42 0,44 0,0173 0,600 639 0,45 0,47 0,0178 MORTAR WITH A 100% REPLACEMENT OF R.A. 0,475 1211 0,33 0,30 -0,0272 0,500 1162 0,34 0,32 -0,0127 0,525 1071 0,36 0,35 -0,0073 0,550 981 0,38 0,37 -0,0016 0,575 899 0,39 0,40 0,0057 0,600 771 0,42 0,42 0,0032 0,625 690 0,44 0,45 0,0108 α ha minimises el oo mean squa ed e o 0,7775 Roo mean squa ed e o 0,0112 Table 4 “e ec i e w/c ela ion (acco ding o equency and lowe bound) compa ed wi h he w/c a io calcula ed wi h he o mula 2 acco ding o he abso p ion capaci y. Value o he α pa ame e ha minimises he oo mean squa ed e o be ween hese wo alues” - Then, he s eps o da a p ocessing a e epea ed, bu his ime, conside ing as eal alues o e ec i e w/c he alues calcula ed wi h he unc ion ha limi s he uppe bound ha ela es e ec i e w/c ela ion o equencies. (Fig. 1) - Nex , i is calcula ed he pa ame e α ha minimises he oo mean squa ed e o be ween he alues o e ec i e w/c calcula ed wi h he o mula 2 and he