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The mal pe o mance o sawdus and lime-mud conc e e mason y
uni s.
Maggi Mad ida*, Aima O bea, Hélène Ca éb, Yokas a Ga cíaa.
a Cons uc ion Enginee ing A ea, Depa men o Mechanical Enginee ing, Facul y o Enginee ing Bilbao, Uni e si y o Basque
Coun y (UPV/EHU), Alameda U quijo, s/n, 48013 Bilbao, Spain.
b SIAME EA-4581, Labo a oi e des Sciences pou l'Ingénieu Appliquées à la Mécanique e au Génie Élec ique, Uni e si y o Pau,
F-64600 Angle , F ance.
Email add esses: [email p o ec ed] (M. Mad id), [email p o ec ed] (A. O be), [email p o ec ed] (H. Ca é) and
[email p o ec ed] (Y. Ga cia).
* Co esponding au ho .
HIGHLIGHTS
Enhanced conc e e using by-p oduc s om he o es y and pape pulp indus ies.
Sawdus conc e e mason y walls had be e he mal esis ance han o dina y walls.
The use o sawdus as a ine-agg ega e eplacemen educes comp essi e s eng hs.
Lime mud inco po a ed as a cemen subs i u e coun e ac s educ ions in s eng h.
Keywo ds:
Conc e e mason y uni s, Indus ial by-p oduc s, Cemen eplacemen , ine agg ega e eplacemen , The mal p ope ies,
Mechanical p ope ies.
ABSTRACT
O e he las h ee decades, a g owing in e es in he p ope ies o he mal en elopes and hei
enhancemen has led o he de elopmen o new sus ainable ma e ials. Howe e , Conc e e Mason y
Uni s (CMUs), ha con inue o be widely used in he he mal en elopes o buildings, as ye a e
manu ac u ed wi h negligible he mal p ope ies and wi h an unsus ainable app oach. Fo his
eason, his esea ch aims o euse some by-p oduc s o he de elopmen o CMUs wi h be e
he mal p ope ies. In addi ion o he e e ence conc e e, one se o blocks was manu ac u ed wi h
5% sawdus in subs i u ion o ine agg ega e and ano he se o blocks wi h he same ine agg ega es
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This is he Accep ed Manusc ip e sion o a Published Wo k ha appea ed in inal o m in Cons uc ion and
Building Ma e ials 169 : 113-123 (2018). To access he inal edi ed and published wo k see h ps://doi.o g/10.1016/
j.conbuildma .2018.02.193. © 2018. This manusc ip e sion is made a ailable unde he CC-BY-NC-ND 4.0
license h ps://c ea i ecommons.o g/licenses/by-nc-nd/4.0/
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eplacemen oge he wi h 15% lime mud in subs i u ion o cemen . The physical, mechanical, and
he mal pe o mance o he CMUs we e e alua ed. Resul s show ha he addi ion o sawdus in
CMUs imp o e he he mal p ope ies. Whe eas, he addi ion o lime mud pa ially coun e ac s he
dec ease in s eng h caused by inco po a ing he sawdus .
1 In oduc ion
Cu en ly, he e is g owing in e es in de eloping new sus ainable cons uc ion ma e ials wi h be e
he mal p ope ies o he he mal en elopes o building. Howe e , Conc e e Mason y Uni s
(CMUs), ha con inue o be widely used in he he mal en elopes o buildings, ha e no e ol ed,
since hey a e s ill manu ac u ed wi h negligible he mal p ope ies and wi h an unsus ainable
app oach. Fo his eason, his esea ch seeks o euse some was e ma e ials as by-p oduc s om he
imbe and pape mill indus ies o he de elopmen o eco iendly CMUs wi h be e he mal
p ope ies o he cons uc ion sec o .
Was e ma e ials ob ained om manu ac u ing p ocesses ha e become one o he main
en i onmen al conce ns wo ldwide. I is no ewo hy ha du ing 2014, i we conside all economic
and household ac i i ies, o al was e p oduc ion o he EU-28 membe s a es amoun ed o 2500
million ons [1]. Besides, he poo ene gy e iciency o mos buildings is a u he cause o ene gy
po e y. Fo ins ance, he esiden ial sec o ep esen s 27% o he wo ld's ene gy consump ion and
17% o CO2 emissions [2]. In his ega d, he Eu opean Commission (EC) has issued ce ain
Di ec i es [3,4]: on he one hand, es ablishing s ic equi emen s o was e educ ion, managemen ,
and ecycling ha p omo e mo es owa ds a ci cula economy. On he o he hand, he EC seeks o
accele a e he cos -e ec i e eno a ion o exis ing buildings. The e o e, he euse o hose was e
ma e ials as by-p oduc s is enable o he de elopmen o ma e ials wi h be e he mal p ope ies
o he cons uc ion sec o .
Conc e e Mason y Uni s (CMUs) a e widely used, especially in de eloping coun ies, as pa o he
building açade componen s. They p esen many ad an ages such as, economy, du abili y, g ea
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lexibili y o plan o m, and spa ial composi ion. Fu he mo e, he cons uc ion o mason y walls
can ul ill di e se oles including s uc u e, sound insula ion, and i e p o ec ion [5]. The e is a
g owing in e es in inding ways ha will pa ially subs i u e some o hei componen s such as
cemen o agg ega es o o he by-p oduc s. Se e al s udies [6-15] ha e been conduc ed on his
subjec , p oducing an en i onmen ally iendly CMUs while main aining an accep able le el o
comp essi e s eng h. All he abo e esea ch ag ees ha he inco po a ion o by-p oduc s in he mix
educes manu ac u ing cos s and minimizes he en i onmen al impac o he ex ac ion o he aw
ma e ials.
Recen e o s [16-21] ha e been conduc ed along simila lines, bu hey ha e been ocused on one
o CMUs weaknesses, i.e. he mal p ope ies. The minimum alues speci ied in he s anda ds
equi ed o high e iciency buildings a e no usually me by single-wid h CMU walls. They usually
need o be in eg a ed in o he mal insula ion laye s. The aim o hese esea ch is o imp o e he
he mal p ope ies o CMUs h ough he use o by-p oduc s, e.g. c umb ubbe , bo om ash, hemp
ibe s, hu ds, ly ash, sewage sludge ash and ex ile e luen sludge, as pa o hei componen s.
Howe e , he challenge o hese esea ch has been o mee he mechanical s eng h equi emen s,
since in gene al, he op imiza ion in he he mal p ope ies is gi en by an inc ease o po osi y in he
conc e e. Whe eas, a high esis ance equi es ha he conc e e be as solid as possible [22,23].
Annually, la ge amoun s o sawdus and lime mud a e ob ained as by-p oduc s om he o es y and
pape pulp indus ies and a e widely a ailable in se e al coun ies. While he o me esul s om
sawing imbe o he manu ac u e o u ni u e and wooden p oduc s, he la e is ob ained du ing
he con e sion o wood in o pu e cellulose ibe s h ough he k a p ocess. I is a solid was e
gene a ed in a caus iciza ion eac ion in he alkali ecycling p ocess o he pape manu ac u ing
indus y.
Depending la gely on he a e age wid h o he saw, he hickness o he sawn imbe and he
echnology o he sawing p ocess, be ween 10% and 13% o each log is educed o ine sawdus
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pa icles [24]. Thei physical and chemical p ope ies may a y no ably acco ding o he species o
ee, he geog aphical loca ion, he sawing echnique and, e en, he pa icle size [25-27]. Sawdus is
mainly eused o pa icleboa d manu ac u e, bio uel and animal mulching [28-30].
P e ious s udies [26,31,32] ha e assessed he e ec o inco po a ing sawdus in CMUs. Adebakin
[26] e alua ed he densi y o blocks wi h a mix a io o 1:8 (one pa o binde o eigh pa o sand).
P oduc ion o blocks was made by pa ial eplacemen o sand wi h a a ying p opo ion (10, 20, 30
and 40%) o sawdus . The esul s ob ained shows ha he addi ion o sawdus educed he uni
weigh o he block and his e ec was mo e no a y as he p opo ion was highe . Ogundipe [31]
examined he use o his by-p oduc o conc e e blocks in load and non-load bea ing walls. These
we e p oduced om he nominal mixes 1:1:2, 1:1.5:3 and 1:2:4, and he W/C a io was 0.6. The
nominal mixes 1:1:2 and 1:1.5:3 we e ound o ha e a comp essi e s eng h o 18.33 Mpa and 10
Mpa a 28 days, which sa is ied he equi emen s o he ASTM C-39 o load and non-load bea ing
walls, espec i ely. On he con a y, mix 1:2:4 did no sa is y he minimum equi emen o non-
load-bea ing. Tu gu e al. [32] manu ac u ed b ick by eplacing limes one powde was e wi h
sawdus , in p opo ions anging om 10-30% by weigh . Thei esul s showed ha he addi ion o
sawdus inc eases he po osi y, hus dec easing i s he mal conduc i i y. The educ ion in he
he mal conduc i i y alue o b ick sample was lowe a 30% eplacemen , abou 38.9%, as
compa ed wi h con ol sample.
Lime mud is basically composed o calcium ca bona e (CaCO3) and has an es ima ed was e
p oduc ion o 0.5 m3 pe on o pulp [33]. The main pape p oduce wo ldwide, China, p oduced in
excess o 10 million ons in 2011 [34] and p oduc ion had con inued o g ow annually. Like
sawdus , he quali y o his by-p oduc a ies no ably because o he di e en o igins o he
cellulose ibe s and ype o pape [35,36]. In Spain and un il he mos ecen economic c isis, lime
mud was eused in he cons uc ion sec o as an addi i e ma e ial o cemen . As demand o
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cemen has dec eased, pape companies ha e lobbied o dispose o hei was e ma e ials in land ill
si es.
The e is li le esea ch on he addi ion o lime mud o mo a s [37,38] and conc e e mixes [39],
while i s sui abili y o CMUs has no been es ed. E oðlu e al. [37] pa ially eplaced (5-30% by
weigh ) o cemen by lime mud, inding ha he densi y was educed as he lime mud con en
inc eased, excep o he sample wi h he lowes eplacemen (5%), which inc ease was abou 3.5%,
as compa ed wi h con ol sample. Modo o e al. [38] es ed a comp ession mo a s ha eplaced in
di e en amoun s (0, 10, 20 and 30%) o cemen wi h lime mud. The esul showed ha he
comp essi e s eng h o he h ee samples a 28 days inc eased by 8.4% as compa ed wi h con ol
mo a . In a p e ious s udy by he au ho s [39], he he mal conduc i i y o conc e e manu ac u ed
by pa ial eplacemen o cemen wi h a a ying p opo ion (5, 10, and 15%) o lime mud was no
in luenced in a posi i e o nega i e way by he addi ion o his by-p oduc . Conc e e a eplacemen
le els o 15% lime mud showed a he mal conduc i i y o 1.12 W/m.K, he same as he e e ence
sample. O he au ho s [40,41] ha e also e alua ed i s use in cemen p oduc ion as an addi ion o he
clinke . They ound ha he mo a s mixed wi h his ype o cemen de eloped sa is ac o y
mechanical s eng h and did no e eal signs o de e io a ion o du abili y weaknesses [41]. Ano he
lines o esea ch has ocused on i s use as a calcined ma e ial o manu ac u e a new kind o calcium-
ich ma e ial o b icks, as a subs i u e o o dina y lime, o p oduc ion in au ocla es and as a soil
amelio an agen [34,42-45].
This esea ch aims o imp o e he he mal p ope ies o CMUs h ough he inco po a ion o sawdus
as a ine agg ega e eplacemen and lime mud as a cemen eplacemen . Al hough he use o
sawdus in CMUs has been p e iously s udied in combina ion wi h was e pape , limes one dus ,
glass powde , and ice husk ash [24,32,46-48], blending i wi h lime mud has ecei ed li le
a en ion. P e ious s udies o da e ha e ocused on hese by-p oduc s and hei e ec s on physical
and mechanical p ope ies, while he analysis o he mal p ope ies has ha dly p og essed a all. In
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his s udy, ou aim is o compensa e he nega i e in luence o sawdus on comp essi e s eng h by
adding lime mud, while main aining i s posi i e in luence wi h ega d o densi y and he mal
p ope ies. So, h ee ypes o CMUs we e cas o ha pu pose. In addi ion o he ini ial e e ence
conc e e mix, 5% o he ine agg ega e by olume was subs i u ed o sawdus in he second mix
and in he hi d one, in addi ion o he ine agg ega e eplacemen o he second ype, a bina y
combina ion was also adop ed wi h 15% o he cemen by olume subs i u ed o lime mud. The
mechanical p ope ies we e assessed hough comp essi e s eng h es s a 14, 28, and 90 days.
Densi y, wa e abso p ion, and capilla y suc ion es s we e conduc ed o de e mine he physical
p ope ies. The he mal esis ance, he mal conduc i i y, he mal ansmi ance (U- alue), hea lux,
and con ec i e hea - ans e coe icien we e e alua ed wi h he ho box me hod 28 days a e
manu ac u ing he walls. A compa ison be ween he esul s ob ained and he equi emen s o he
cu en s anda ds [49-51] is also discussed. Finally, he expenses in ol ed in he p oduc ion o
CMUs wi h and wi hou by-p oduc s we e s udied by cos analysis.
2 Ma e ials
The cemen ype used in his s udy consis ed o blended Po land cemen CEM II/A-M (V-L) 42.5
R wi h a densi y o 3.05 /m3 and a composi ion o ly ash and limes one o 6-20% as pe he EN
197-1 s anda d [51]. C ushed na u al-limes one sand wi h densi y o 2.71 /m3 and size o 0-4 mm
was used as ine agg ega e, whe eas c ushed na u al-limes one wi h densi y o 2.70 /m3 and size o
2-6 mm was used as a coa se agg ega e. The sawdus used in his esea ch was ob ained om he
sawing o Radia a pine wood in o s anda d sizes o he p oduc ion o packaging. I s densi y is o
0.57 /m3 wi h a size o 0-2 mm. The lime mud was p oduced as a by-p oduc om he ecycling
p ocess in pape p oduc ion using Radia a pine wood as aw pulp. I s densi y was 0.83 /m3 and i s
size was be ween 0.4-50 μm. Table 1 shows he chemical analysis and mine al composi ion o a
sample o lime mud. The Loss O Igni ion (LOI) o lime mud is mainly ca bon dioxide, wi h a
mino p esence o o ganic ma e om cellulosic ibe s. Sawdus was used in pa ial eplacemen o
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he ine ac ion while lime mud, was inco po a ed o educe he cemen amoun . Bo h by-p oduc s
we e added wi hou p e ea men . The g ading pa icle size was ob ained a e sie ing in acco dance
wi h he es in s anda d EN 933-1 [51] o na u al agg ega es and sawdus , and lase di ac ion
echniques o lime mud (see Fig.1). A mo e de ail in o ma ion abou he physical and chemical
p ope ies o he sawdus and lime mud unde s udy can be ound in a p e ious s udy [39].
Table 1
Chemical and mine al composi ion o he lime mud.
Chemical composi ion Pe cen age mass (w .%)
SiO20.03
Al2O30.01
Fe2O30.09
MnO 0.01
MgO 0.19
CaO 50.31
Na2O 2.83
K2O 0.17
TiO20.01
P2O50.04
SO31.48
LOI 46.10
Mine al composi ion Pe cen age mass (w .%)
Calci e >90
Calcium hyd oxide 1-3
O ganic ma e <7
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Fig.1. G ading cu e o ine agg ega e, coa se agg ega e, sawdus , and lime mud.
2.1 Conc e e mix design
Th ee ypes o wo-co e CMUs we e manu ac u ed, all o he same size: 390 mm x 190 mm x 190
mm. These sizes we e chosen and co espond o he mos widely used blocks o açades in Spain.
In one ype o CMU 5% o he ine agg ega e was subs i u ed (by olume) by sawdus ; in ano he
ype, 5% and 15% o he ine agg ega e and cemen we e subs i u ed (by olume) by sawdus and
lime mud, espec i ely. As a e e ence, he se ies o con en ional CMUs in ol ed no subs i u ion.
The designa ions o hese 3 ypes o CMUs we e MS, MSLM and MREF, espec i ely. Fo each
ype, 90 blocks we e manu ac u ed, amoun ing o 270 CMUs. The assumed cemen and sand
subs i u ions we e based on a p e ious s udy o he i s wo au ho s [39]. In bo h cases, he sawdus
and lime mud dosages ha e been adop ed on he comp omise be ween he he mal p ope ies and
he mechanical ones. On he one hand, a low sawdus pe cen age, 5%, was conside ed su icien o
imp o ing he insula ion o he CMUs wi hou educing d as ically i s s eng h. On he o he hand,
he addi ion o lime mud up o a 15% coun e ac s he nega i e e ec o he sawdus on he
mechanical p ope ies.
The mix u es we e designed o ha e no-slump acco ding o he manu ac u ing equi emen s o
CMUs. The w/b a io was se a 0.4 o mixes MREF and MS and 0.38 o MSML. Bo h w/b a ios
we e low o educe he cos o cemen and he amoun o wa e in he mix and hus ob ain be e
esul s o s eng h. A wa e educing admix u e was added du ing he s i ing s age, e en hough a
no-slump mixes is equi ed, o enhance he wo kabili y o all he conc e e mix u es needed in he
molding p ocess, since he mix was design wi h a low w/c a io. The amoun o plas icize was 1%,
by weigh o cemen o binde . Analysis o he mix wa e showed no compounds ha could be
ha m ul o he conc e e (pH o 7.81, sul a e con en <20 mg/L and a ha dness o <14 º ). The mix
design is p esen ed in Table 2.
Table 2
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a) b)
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Mix design pe 1 m3.
Mix
code
CEM
(kg/m3)
FA
(kg/m3)
CA
(kg/m3)
SD
(kg/m3)
SD
ac ion
(Vol. %)
LM
(kg/m3)
LM
ac ion
(Vol. %)
W
(kg/m3)
SP
(kg/m3)
MREF 180 1900 500 - - - - 72 1.80
MS 180 1805 500 19.98 5 - - 72 1.80
MSLM 153 1805 500 19.98 5 7.35 15 72 1.61
CEM = Cemen , FA = Fine agg ega es, CA = Coa se agg ega es, SD = Sawdus , LM= Lime mud, W = Wa e , SP =
Supe plas icize .
The CMUs we e manu ac u ed in a local p ecas company, using a Gi o P-750 conc e e mixe and a
Quad a V conc e e block machine (see Fig. 2). The mixing and placemen p ocedu es we e simila
o he s anda d ones. A e mixing he agg ega es, he cemen and he by-p oduc s we e added in
wo successi e s ages. Then, he wa e and he wa e educe admix u e we e g adually dosed. Once
p epa ed, he mix u e was passed along a con eyo bel o he p e iously selec ed molds whe e i
was ib a ed and compac ed o p oduce 6 CMUs e e y 30 s. The manu ac u ing p ocess o each
se ies was pe o med wi hin a pe iod o app oxima ely 7 min. We CMUs we e inally ai -d ied a
oom empe a u e be ween 20 and 22.5 °C and a a ela i e humidi y in excess o 50%, un il he day
o he es .
Fig.2. a) Conc e e block machine and b) molds.
3Tes p ocedu e
3.1 Densi y and abso p ion
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s eng h [57]. The e o e, his s udy e alua es he posi i e in luence o lime mud addi ions o ensu e
a sui able mechanical beha io .
4.2 Abso p ion
This p ope y can be an indica o o he compac ion le el o he conc e e mix and o he open
po osi y in he block. F om he esul s shown in Table 3, an inc ease in wa e abso p ion on samples
MS and MSLM o 65.9% and 25.9%, espec i ely, was obse ed compa ed o he MREF, due o he
high abso p ion o sawdus [58]. Howe e , he lime mud in he MSLM samples somewha
coun e ac ed he nega i e e ec o he sawdus . Compa ing he alues ob ained o densi y and
abso p ion, hey we e, as expec ed, ound o be in e sely co ela ed. Wi h a dec ease in densi y, he
wa e abso p ion o he CMUs inc eased and ice- e sa.
Al hough no speci ic limi on he abso p ion alue o CMUs is ound in he Spanish s anda d, he
ASTM C90 s anda d [49] speci ies maximum wa e abso p ion alues o CMUs o 208, 240 and
288 kg/m3 o no mal weigh , medium weigh and ligh weigh blocks, espec i ely. Compa ing he
abso p ion esul s ob ained wi h he equi emen s o his s anda d, he abso p ion alues we e
accep able o he h ee ypes o blocks, and wi hin he ange es ablished in he s anda d.
4.3 Capilla y suc ion
Capilla y suc ion plays an impo an ole in he anspo a ion and edis ibu ion o wa e a e i
comes in o con ac wi h he su ace o he block. I depends on he po osi y and he deg ee o
connec ion be ween he in e nal po es o he conc e e.
The esul s e eal ha capilla y abso p ion inc eased by 16.2% o CMUs con aining 5% sawdus ,
MS (see Table 3). This inc ease was expec ed owing o he wa e abso p ion o he sawdus .
Mo eo e , he MSLM specimens also p esen ed an inc ease; howe e , i was no as p onounced, a
a ound 10.8%. Thus, a sligh ly bene icial e ec in capilla y suc ion was no iceable in he lime mud
conc e e. This inc ease could be a ibu ed o ewe connec ions be ween he po es ha also
imp o e he comp essi e s eng h. These esul s con i m he da a on wa e abso p ion p esen ed
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abo e. Mo eo e , he maximum capilla y suc ion alue o load-bea ing CMUs acco ding o he
equi emen s o he Spanish Building Technical Code (CTE) [59] is limi ed o 5 [g/(m2s)]. All he
esul s a e lowe han he pe mi ed maximums in he Spanish s anda d. The h ee ypes o blocks
may he e o e be used ou doo s, wi h exposed aces in humid condi ions. This es is no pa o he
ASTM s anda d o he assessmen o CMU pe o mance, so i is no equi ed.
4.4 Comp essi e s eng h
The esul s o he comp ession es , in e ms o a e ages, a 14, 28, and 90 days o ages a e shown
in Table 3. Based on expe imen al e idence, he comp essi e s eng h o sample MS had dec eased
by 34.3% a 28 days compa ed o sample MREF.
The dec eased s eng h o sample MSLM was lowe , a app oxima ely 13.4%. I is e iden ha he
use o lime mud has a posi i e e ec on comp essi e s eng h [61]. P e ious esea ch has also
p o en ha lime mud in pa ial eplacemen o cemen will imp o e he comp essi e s eng h o
conc e e mixes [62,63]. This inc eased s eng h is due o a chemical eac ion be ween he nano-
CaCO3 and he cemen , which accele a es he eac ion a e o icalcium alumina e (C3A) o o m a
ca boalumina e complex, he eby inc easing he o al hyd a ion p oduc s and he s eng h [64].
Addi ionally, he e is also a eac ion wi h he icalcium silica e (C3S), which educes se ing ime
and inc eases esis ance a ea ly ages [65].
The minimum 28-day s anda dized s eng h equi emen o load-bea ing CMU acco ding o he
Spanish CTE [50] is 5.0 MPa. Howe e , his s anda d also accep s 4.0 MPa o load-bea ing and 3
MPa o non-load-bea ing conc e e, bu he comp essi e s ess will ha e o be limi ed a he
ul ima e limi s a e o 75% o he mason y design s eng h, o he wise speci ic comp essi e s eng h
s udies will ha e o be pe o med. The s anda dized s eng h is equi alen o he comp essi e
s eng h o a 100 mm x 100 mm (Wid h x Heigh ) ai d ied specimen, he pa s con e ed in o
equi alen comp essi e s eng h co esponding o an ai -d ied specimen, acco ding o he CTE [50].
The s eng h was mul iplied by a o m ac o , which in his case is 1.12, due o he size o he
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pieces. The s anda dized s eng hs a 28 days o he h ee ypes o CMUs a e shown in Fig. 6. No e
ha bo h samples MREF and MSLM can be classi ied as load-bea ing conc e e mason y. Howe e ,
addi ional s udies would be necessa y o he MS samples, we e hey e e used in load-bea ing
walls.
Fig. 6. S anda dized comp essi e s eng h o CMUs a 28 days and CTE equi emen s.
While he ASTM C129 and ASTM C90 [49] s anda ds es ablish a mo e es ic i e c i e ion, he 28-
day s eng h equi emen s we e se a 4.1 MPa and 13.1 MPa o non-load-bea ing and o load-
bea ing CMUs, espec i ely. The comp essi e s eng h esul s (see Table 3) o all ypes o CMUs
a 28 days only sa is y he minimum equi emen s o non-load-bea ing s uc u es in hose
s anda ds. As expec ed, he CMUs o lowe densi y we e obse ed o ha e lowe comp essi e
s eng hs.
4.5 The mal p ope ies
The he mal beha io o CMUs is di ec ly ela ed o bo h he p esence o ai oids wi hin he
conc e e and he componen s o he conc e e. The lowe he he mal conduc i i y o inclusions ha
subs i u e he con en ional componen s, he g ea e he insula ion e iciency o he wall [66,67].
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The esul s o he he mal p ope ies o he h ee mason y walls a e shown in Table 4 and he wall
empe a u es and hea lux s abiliza ion o e 24 h a e shown in Fig. 7, Fig. 8 and Fig. 9.
Table 4
The mal p ope ies o he mason y walls.
Designa ion
MREF wall MS wall MSLM wall
A e age Min. Max. A e ag
eMin. Max. A e ag
eMin. Max.
Gua d ai empe a u e: °C 23.7 23.6 23.9 23.9 23.8 24.0 23.7 23.6 23.8
Wa m ai empe a u e: °C 22.8 22.1 22.2 22.5 22.5 22.6 22.3 22.2 22.3
Wa m wall
empe a u e: °C 19.2 17.6 19.3 19.6 18.4 20.7 19.4 19.1 19.9
Cold ai empe a u e: °C 5.0 4.5 5.4 5.0 4.6 5.4 5.0 4.5 5.45
Cold wall empe a u e: °C 8.1 7.8 9.1 8.1 7.8 16.0 8.3 7.9 9.1
Hea low: W 26.1 25.0 32.7 23.3 19.3 24.9 24.2 20.8 26.1
The mal esis ance: m²
K/W 0.27 0.32 0.30
The mal conduc i i y: W/m.K 0.699 0.601 0.643
U- alue: W/
m².K 2.26 2.05 2.10
Hea lux: W/m² 40.73 36.42 37.75
Con ec i e hea
ans e
coe icien (Ho
chambe ):
W/
m².K 13.53 12.50 13.14
Con ec i e hea
ans e
coe icien (Cold
chambe ):
W/
m².K 13.21 11.74 11.51
Fig. 7. Measu emen o hea lux and empe a u es (cold and ho zones) om he MREF wall.
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Fig. 8. Measu emen o hea lux and empe a u es (cold and ho zones) om he MS wall.
Fig. 9. Measu emen o hea lux and empe a u es (cold and ho zones) om he MSLM wall.
Compa ing he esul s o he h ee ypes o mason y walls, i was ound ha he inco po a ion o 5%
sawdus imp o ed he he mal esis ance alues by 18.5% compa ed o he e e ence wall, while he
combina ion o 5% sawdus and 15% lime mud imp o ed he same alues by 11.1%. This inc ease
in he mal esis ance imp o es he alues o he mal conduc i i y and he ans e coe icien . A
dec ease in he hea lux was no ed o 10.6% in he MS wall and o 7.3% in he MSLM wall.
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These imp o emen s in he mal p ope ies a e due o sawdus pa icles ha es ain he he mal
low. The he mal conduc i i y o he (Radia a pine) sawdus is app oxima ely 0.13 W/m.K [68]
ha is less han he he mal conduc i i y o he ine limes one wi hin he ange o 1-3 W/m.K [69].
Ano he ac o o conside in he inc ease o oids is he weake in e ac ion be ween he sawdus
and he ma ix han be ween he ine limes one and he ma ix [54], leading o an inc ease in
occluded ai . The he mal conduc i i y o he ai is less han ha o he conc e e [57]. The e o e, he
ai -gaps oppose he hea ans e h ough he CMUs, which imp o es he he mal esis ance o he
wall [56]. In con as , imp o emen s in he mal p ope ies a e lowe o CMUs wi h a combina ion
o sawdus and lime mud, con i ming he a ia ions in he mal conduc i i y wi h he densi y o he
es ed CMUs [70]. No e ha , e en hough he educ ion in densi y imp o es he he mal
conduc i i y o he blocks, his beha io educes he he mal mass o he ma e ial, which is needed
in clima es whe e summe empe a u es a e high and he e is a la ge he mal ampli ude.
ACI Commi ee 122 [68] sugges s p ac ical he mal conduc i i y design alues o s uc u al
conc e e blocks wi h limes one as one o hei componen s, which ange om 0.95 W/m.K o a
conc e e densi y o 1763 kg/m3 o 1.44 W/m.K o a densi y o 2083 kg/m3. These he mal
conduc i i y alues a e highe han hose ob ained in his esea ch.
Al hough no pa icula he mal esis ance limi alue is speci ied in he cu en s anda ds, CMUs do
ha e o comply wi h he U- alue s ipula ed o açades. In Spain, he mal egula ions impose
maximum U- alues o ex e nal walls ha a e be ween 0.94 and 0.57 W/m2.K, depending on he
clima ic a ea o he loca ion. The esul s o U- alues a e be ween 2.26 and 2.05 W/m2.K.
The e o e, hese walls will equi e ex a insula ion laye s o sa is y he legisla ion. The e o e, hese
walls will equi e ex a insula ion laye s o sa is y he legisla ion. Ne e heless, his imp o emen in
he mal p ope ies could lead o possible educ ions in insula ion hickness and he eby inc ease he
a ailable loo a ea.
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The U- alue o a ypical CMU açade o a house loca ed in he clima ic zone o Bilbao whe e he
CTE equi es a maximum U- alue o 0.730 W/m2.K, was calcula ed by a ying he he mal
conduc i i y o he CMU and he hickness o he insula ion. The açade componen s om he
ex e io o he in e io consis ed o s ucco, CMU, s one wool insula ion, and gypsum wallboa d.
Ma e ial hicknesses and he mal conduc i i y as well as he U- alue esul s o 4 açades a e shown
in Table 5. As obse ed, a educ ion in he insula ion hickness o app oxima ely 10 mm can be
ob ained and complies wi h he equi ed maximum, whe e MS o MSLM blocks a e used.
Table 5
U- alues o h ee ypes o açades wi h he CMUs unde s udy.
Ma e ials
Case 1 MREF Case 2 MS Case 3 MSLM Case 4 MREF
λ
(W/m.K)
e
(m)
λ
(W/m.K)
e
(m)
λ
(W/
m.K)
e
(m)
λ
(W/
m.K)
e
(m)
S ucco 0.570 0.015 0.570 0.015 0.570 0.015 0.570 0.015
CMU 0.699 0.190 0.601 0.190 0.640 0.190 0.699 0.190
S one wool insula ion 0.035 0.030 0.035 0.030 0.035 0.030 0.035 0.040
Gypsum wallboa d 0.400 0.015 0.400 0.015 0.400 0.015 0.400 0.015
U- alue (W/m2.K) 0.734 0.715 0.726 0.610
Non-complian Complian Complian Complian
4.6 Economic bene i s
The expenses in ol ed in he p oduc ion o CMUs wi h and wi hou by-p oduc s we e s udied by
cos analysis. Ma e ials p ices and daily p oduc ion amoun s a e he o e all o da a collec ed om
di e en p o ide s and he s a o di e en p ecas companies, espec i ely, om Spain. Table 6
summa izes he uni p ices o he p ima y componen s o he manu ac u ed o CMUs and Table 7
shows he p opo ion o ma e ials o each mix and he cos o ma e ials o he h ee ypes o
CMUs. The alue o sawdus was se a 35.00 €/Ton, while he lime mud ha would o he wise ha e
been dumped a a land ill si e was cos ee (0.00 €/Ton).
Table 6
Uni p ice o ma e ials used o he manu ac u e o he CMUs.
Ma e ials P ice (€) Ma ke Uni Volume (m3) Uni p ice pe 1 m3(€)
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CEM 95.00 Ton 0.328 289.75
CA 11.00 Ton 0.370 29.70
FA 12.00 Ton 0.369 32.52
SP 0.95 Kg 0.001 995.60
W 1.23 m31.000 1.23
SD 35.00 Ton 1.754 19.95
LM 0.00 Ton 1.000 0.00
CEM = Cemen ; CA = Coa se agg ega es; FA = Fine agg ega es; SP = Supe Plas icize ; W = Wa e ; SD = Sawdus ;
LM= Lime mud.
Table 7
Cos o MREF, MS and MSLM ma e ials pe 1m3.
Ma e ials
MREF MS MSLM
Requi ed
olume
(m3)
Uni
P ice Amoun Requi ed
olume
(m3)
Uni
p ice Amoun Requi ed
olume
(m3)
Uni
p ice Amoun
pe 1 m3(€) pe 1 m3(€) pe 1 m3(€)
CEM 0.059 289.75 17.10 0.059 289.75 17.58 0.050 289.75 14.54
CA 0.185 29.70 5.50 0.185 29.70 6.11 0.185 29.70 5.50
FA 0.701 32.52 22.80 0.666 32.52 23.20 0.666 32.52 21.66
SP 0.002 995.60 1.71 0.002 995.60 1.76 0.002 995.60 1.71
W 0.072 1.23 0.09 0.072 1.23 0.09 0.072 1.23 0.09
SD - - - 0.035 17.85 0.67 0.035 19.95 0.70
LM - - - - - - 0.009 0.00 0.00
To al cos o p oduc ion pe 1m3: 47.20 46.76 44.19
CEM = Cemen ; CA = Coa se agg ega es; FA = Fine agg ega es; SP = Supe Plas icize ; W = Wa e ; SD = Sawdus ;
LM= Lime mud.
Based on hese esul s, we can a i m ha sa ings pe cubic me e o conc e e o € 0.44 may be
achie ed, which is a pe cen age sa ing o app oxima ely 1% o he MS samples. The e again, o
he MSLM samples, he sa ings pe cubic me e o conc e e we e € 3.01, which is a pe cen age
sa ing o 6.4%. In his las case, he economic sa ing is highe , due o he subs i u ion o he cemen
which is he mos expensi e componen o he mix. Al hough hese pe cen ages a e low, he annual
sa ings can be signi ican i one o hese wo ypes o CMUs we e manu ac u ed.
A p ecas company can p oduce on a e age 6,000 CMUs o e an 8 h wo kday, which allows us o
es ima e he sa ings wi h ega d o he annual cos o ma e ials. A o al o 1,482,000 uni s would be
manu ac u ed each yea , equi ing an amoun o 8,233.33 m3 o conc e e. Thus, he ma e ials o he
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manu ac u e o ypical CMUs would cos a ac o y € 388,613, al hough he cos s o manu ac u ing
he MS and he MSLM samples would be € 384,991 and €363,831, espec i ely. A company could
he e o e achie e a educ ion in he cos o ma e ials o app oxima ely ei he € 3,600 o € 24,700
pe yea h ough he p oduc ion o CMUs wi h ei he sawdus o wi h he combina ion o bo h by-
p oduc s, espec i ely.
Likewise, o Eu opean coun ies whe e he e is an impo an p oduc ion o wood and pape , such
as: Sweden, Finland, Ge many and I aly and he e o e, la ge quan i ies o sawdus and lime mud a e
gene a ed, he economic bene i s would be simila o hose ob ained, since he p ices o cons uc ion
ma e ials in Eu opean coun ies a e simila . While o he coun ies such us Uni ed S a es o
Ame ica, B azil, Canada, China, Japan, and Russia which also ha e an signi ican gene a ion o
hose by-p oduc s will ob ain a lowe economic bene i s, since he p ice o cemen and agg ega es is
lowe , excep o Canada and B azil, which would ha e a g ea e economic bene i s since, he
opposi e happens, he p ice o cemen is highe .
A u he economic aspec o conside is he sa ings associa ed wi h he disposal o he lime mud a
land ill si es [71]. The cos o land ill is a ound o € 105.60 pe on. In he case o MSLM, a o al o
60.52 ons o lime mud would be used. Thus, he cos sa ings on land ill would be a leas € 6,300
pe yea . No e ha he highes economic bene i s would ensue om he manu ac u e o MSLM, as
e en hough sawdus is a by-p oduc , i al eady has comme cial ou le s.
On he o he hand, a u he expense would be ound in he cos ela ed o he s o age o he by-
p oduc s in he CMUs p oduc ion acili y, e.g. he e would be necessa y o buy and ins all wo silos,
which nowadays cos app oxima ely 20,000 eu os, being he ini ial in e sion o 40,000 eu os. Thus,
wo yea s would be needed o amo ize he ini ial expenses o acili ies o he s o age o he by-
p oduc s.
5 Conclusions
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The esul s o he physical, mechanical and he mal p ope ies o h ee ypes o Conc e e Mason y
Uni s (CMUs) ha e been p esen ed in his pape : one ype manu ac u ed wi h 5% o he ine
agg ega e by olume subs i u ed o sawdus ; a second ype, wi h 5% o he ine agg ega e by
olume subs i u ed by sawdus and 15% o he cemen by olume subs i u ed o lime mud; and, a
hi d ype wi h no by-p oduc s ha se ed as he e e ence specimen. Based on he expe imen al
esul s ob ained in he s udy, he ollowing conclusions can be d awn:
1. The esul s o he he mal es show ha i is possible o op imize he he mal beha io o he
CMUs, wi h he inco po a ion o sawdus . This imp o emen is a ibu ed o he inc ease o oids in
he CMUs and he low densi y o he sawdus , which in u n dec eased he densi y o he uni s.
The e o e, he p opo ional ela ionship ha exis s be ween he densi y and he he mal p ope ies o
he ma e ials is con i med.
2. As expec ed, he pa ial eplacemen o he limes one by sawdus esul ed in a dec ease in he
comp essi e s eng h o he CMUs, howe e , his dec ease could be pa ially coun e ac , wi h he
addi ion o lime mud and s ill ge an imp o emen in he mal p ope ies, al hough no as
p onounced, as ob ained when only he sawdus was added. This con i med he in e se ela ionship
ha exis s be ween mechanical esis ance and he mal p ope ies.
3. The esul s o comp essi e s eng h and capilla y suc ion o he h ee ypes o CMUs, me he
equi emen s es ablished in he Spanish egula ions o load-bea ing CMUs.
4. The inco po a ion o by-p oduc s could lead o a educ ion in he cos s o he ma e ials o he
manu ac u e o he CMUs and in u n could sligh ly educe he o al budge o he p ojec , due o
he sa ings in he insula ing ma e ial o he açade.
5. Sawdus and lime mud ha e he po en ial o be used in he p oduc ion o g eene and mo e
economical CMUs. Howe e , he es s p esen ed in his pape cons i u e he i s s ep in esea ch on
sawdus conc e es and sawdus and lime-mud combina ions o use as componen s in he
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