Performance and Microstructural Analysis of Lightweight ...Feb 13, 2018 · 325kg/m3 of concrete,...

Research ArticlePerformance and Microstructural Analysis of LightweightConcrete Blended with Nanosilica under Sulfate Attack

Paola Vargas12 Natalia A Marın13 and Jorge I Tobon 1

1Department of Materials and Minerals Cement and Construction Materials Group (CEMATCO)Universidad Nacional de Colombia Medellın Colombia2Department of Engineering Universidad de Medellın Medellın Colombia3Universidad Catolica de Oriente Rionegro Colombia

Correspondence should be addressed to Jorge I Tobon jitobonunaleduco

Received 13 February 2018 Revised 10 April 2018 Accepted 2 May 2018 Published 3 June 2018

Academic Editor Li Li

Copyright copy 2018 Paola Vargas et al is is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

e influence of two lightweight aggregates (LWA) on concrete and the effects of cement substitution for nanosilica (NS) on theinterfacial transition zone (ITZ) and cementitious matrix of concrete in resistance to attacks by magnesium sulfate (MgSO4) areresearched in this work e aggregates evaluated were perlite which is a lightweight aggregate of open porous structure andexpanded clay (aliven) with closed porous structure e variables included in the study were replacement percentage of coarseaggregates by lightweight coarse aggregates (0 and 100 by volume) and replacement percentage of cement by nanosilica (0 and10 by weight) In the dosage of the mixtures watercementitious-material ratio constant of 035 was used e LWA werecharacterized by XRD XRF and SEM techniques Compressive strength water absorption and volume change in magnesiumsulfate solution (according to ASTMC1012 for a period of 15 weeks) of lightweight concretes were evaluated It was found that thenanosilica had effect on refinement in the pore system however the main incidence on the compressive strength and durability oflightweight concrete (LWC) was defined by the characteristics of lightweight aggregate used in its preparation

1 Introduction

e durability of the conventional concretes under thechemical attack by sulfates has been studied according to thesulfate source whether it is external or internal e externalattack occurs when the concrete is exposed to environmentssuch as soil contaminated by sulfates or water with sulfatecontents [1] e internal attack is caused by issues such asexcessive contamination with sulfate in concrete constituentmaterials contaminated aggregates or presence of sulfate inthe cement clinker due to the use of sulfur-rich fuels or thepresence of sulfides or sulfates in their raw materials [2] emain consequence of the attack by sulfates is the disintegrationof the concrete or mortar due to chemical reactions betweenthe hydrated phases of the Portland cement and the sulfateions Depending on the concentration and source of the sulfateions in the water and the cement composition the expansionof the concrete can be produced with the generation of cracks

and increased permeability favoring the penetration of waterwith aggressive agents or the deterioration and loss of cohesionof the products of hydrated cement with progressive loss ofcompressive strength and mass [3]

Also the durability of concrete under attack by sulfatesaccording to the type of sulfate has been studied findingthat in the traditional attack by sodium sulfate as a con-sequence the formation of secondary ettringite occurs Oneof the main causes for this formation is due to the reactionbetween the SO2minus

4 ions and the hydrated calcium mono-sulfoaluminate or to the formation of gypsum and its sub-sequent reaction with calcium aluminate hydrates (C-A-H)While in the case of the magnesium sulfate attack it attacksthe calcium silicate hydrated (C-S-H) causing a loss ofcohesion of the paste with the formation of gypsummagnesium hydroxide and silica gel as well [1]

Magnesium sulfate (MgSO4) is the most aggressive ofsulfates due to the lowering of the pH of the solution of the

HindawiAdvances in Civil EngineeringVolume 2018 Article ID 2715474 11 pageshttpsdoiorg10115520182715474

pores in the cement paste hydrated by the reaction with theportlandite and the formation of brucite [2] MgSO4 reactsmainly with the hydration products of the cement the reactionof the sulfate with calcium hydroxide released during the hy-dration of the cement forms calcium sulfates (gypsumCaSO4 middot H2O) andmagnesium hydroxide (brucite Mg(OH)2)according to the following reaction [3]

MgSO4 + Ca(OH)2 + 2H2OrarrCaSO4 middot 2H2O + Mg(OH)2

(1)

Another possible effect of magnesium sulfate is the re-action with the C-S-H gel where due to the decalcificationproduced by this sulfate a hydrated magnesium silicate isobtained M-S-H which is a poor cohesive gel [4] non-cementitious which leads to softening of the cement matrix[5 6] according to the following reaction In addition asa result of this reaction gypsum and hydrated silica areproduced

C-S-H + MgSO4rarrCaSO4 middot 2H2O + M-S-H (2)

is gypsum produced in (2) could react with C3A toproduce ettringite as shown in the following reaction [1]

CaSO4 middot 2H2O + Al2O3 middot 3CaO + 26H2O

rarrCa6Al2 SO4( 11138573(OH)12 middot 26H2O(3)

In the presence of carbonates and under the appropriateenvironmental conditions the formation of thaumasite(CaSiO3 middot CaSO4 middot CaCO3 middot 15H2O) can be produced asshown in the following reaction [3]

nSiO2 middot H2O + CaOH + CaCO3 + MgSO4

rarrCaSiO3 middot CaSO4 middot CaCO3 middot 15H2O

+ CaSO4 middot 2H2O + Mg(OH)2

(4)

To fully appreciate lightweight concrete it is essential tounderstand the intrinsic nature of lightweight aggregates(LWA) and how they influence the properties of concretemade from them e LWA have an array of vesicles or airvoid within their masse size spacing and interconnectionof the vesicles make these aggregates capable of producingconcrete with lower density close to 1850 kgm3 with ad-vantages such as increased thermal insulation extendedmoistcuring and increased durability [7]

e effect of lightweight aggregates on both the mi-crostructure and durability of mortars and concretes hasbeen studied by several researchers [8ndash12] Finding that lightaggregates affect the microstructure of the interfacial tran-sition zone (ITZ) of porous quality which has been im-proved with the addition of fly ash and silica fume findingthat in order to improve resistance to sulfate attack withthese materials the content of fly ash or natural pozzolanshould be between 25 and 35 by mass while for silica fumebetween 7 and 15 (ACI 201-2) [13ndash15] e addition ofsuch materials significantly reduces the permeability of theconcrete and also when combined with the alkalis and thecalcium hydroxide which are released during the hydrationof the cement the potential for gypsum formation reduces

Nanosilica (NS) has been widely recognized as an activeadditive to cement [16 17] Its activity accelerates the hy-dration reaction by means of the nucleation mechanism(early activity) for the formation of C-S-H and its pozzo-lanic activity increases the production of C-S-H Addi-tionally NS also acts as a filler decreasing the waterabsorption that allows us to improve the durability of thecementitious matrix [9 10]

is work focuses on the study of the morphology andcomposition (chemical and mineralogical) of the LWA thereplacement of cement by nanosilica in the formation of themicrostructure and the thickness of the ITZ and the in-fluence of this on the resistance to attack by magnesiumsulfate in lightweight concretes

2 Materials and Methods

For themanufacture of concretes ordinary Portland cementnanosilica (NS) and two lightweight aggregates thermallyexpanded clay aliven (AL) and perlite (PE) as well wereused

e methodology proposed for the development of thisresearch is divided into three main activities chemicalmineralogical and physical characterization of rawmaterialsthrough X-ray diffraction (XRD) scanning electron mi-croscopy (SEM) optical microscopy (OM) specific surfacearea (BET) and density and water absorption of aggregates(ASTMC 127 [18]) e second stage consisted in the designand preparation of the concretes and finally the study of themechanical properties and durability of the LWC

21 Chemical Characterization of Materials e chemicalcomposition of cement nanosilica perlite and expandedclay was determined by X-ray fluorescence (XRF) using ARL8680 S equipment in boron lithium oxide (B4Li2O7) pills InTable 1 it can be seen that silicon oxide is present in a greaterproportion for both aggregates being higher in perlite(7245) than in aliven (5967) e second componentpresent in greater quantity in both aggregates is aluminumoxide but unlike SiO2 aliven has a higher content of Al2O3in comparison with the perlitee NS used is of high purityemain constituent of the cement is calcium oxide presentin 6069 followed by 20 silicon oxide and lower pres-ence of sulfur of interest in this research e chemical

Table 1 Chemical composition of materials

Chemical compositionWeight ()

Perlite Aliven NS CementSilicon oxide (SiO2) 7245 5967 9356 209Titanium oxide (TiO2) 022 119 002 021Aluminum oxide (Al2O3) 1338 1695 000 472Iron oxide (Fe2O3) 135 979 039 320Magnesium oxide (MgO) 008 413 013 180Calcium oxide (CaO) 120 357 022 6069Sodium oxide (Na2O) 340 207 062 037Potassium oxide (K2O) 457 128 002 061Sulfur oxide (SO3) 009 004 030 013Ignition losses at 1000degC 292 075 446 368

2 Advances in Civil Engineering

composition of the cement indicates that the percentagescorrespond to a Portland cement type I according to ASTMC 150 [19]

22 Mineralogical Characterization e mineralogicalcharacterization for aggregates and nanosilica was per-formed using X-ray diffraction (XRD) in an XRD PAN-alytical XrsquoPert Pro MPD with a copper (Cu) X-ray source(λα1 0154059 nm) in a 2θ interval between 6deg and 70deg witha step of 002deg and an accumulation time of 30 s eidentification of diffractograms was done with the databaseof XrsquoPert High Score Plus software For the perlite it can beseen that in the diffractogram of Figure 1(a) a broad peak isformed between positions 2θ of 20deg and 30deg where thecharacteristic quartz peak is found around 265deg is peakcorresponds to silica of low degree of crystallinity oramorphous characteristic attributed to the fact that thispeak lacks the slenderness that indicates the high crystal-linity of silica Other minor components are aluminosilicates

such as albite is composition corresponds to the pro-cesses of perlite formation which is a volcanic glass

e diffractogram of Figure 1(b) allows us to establishthat the main mineralogical species in the aliven corre-sponding to high-grade crystallinity quartz is in the position2θ of 265deg and this peak has a great slenderness reaching they-axis to approximately 18000 counts Other phases presentcorrespond to alumininosilicates in the form of plagioclaseand hornblende and small traces of iron oxide in hematiteform is mineralogy of aliven corresponds with its originof thermally expanded clay For the nanosilica (Figure 1(c))it is shown that it corresponds to silica nanoparticles of lowdegree of crystallinity

23 Morphological Characterization e morphology ofthe aggregates was studied by micrographs of stereos-copy and SEM in JEOL JSM 5910LV with backscatteringelectrons (BES) detectors and for nanosilica by TEM ina FEI TECNAI 20 Twin microscope Perlite (Figure 2)

Inte

nsity

(cou

nts)

5000

4500

4000

3500

3000

2500

2000

1500

1000

Q

A

0 10 20 30 40 50 60 70Position (2 theta)

Q quartzA albite

(a)

Inte

nsity

(cou

nts)

20000

18000

16000

14000

12000

10000

8000

6000

4000

2000

Q QH A

Q A QA Q A Q

Q

0 10 20 30 40 50 60 70Position (2 theta)

Q quartzH hornblende

A albiteHE hematite

(b)

Inte

nsity

(cou

nts)

700

600

500

400

300

200

100

0

Position (2 theta)0 10 20 30 40 50 60 70

(c)

Figure 1 XRD patterns of (a) LWA perlite (b) LWA aliven and (c) nanosilica

Advances in Civil Engineering 3

corresponding to an aggregate of angular volcanic originwith exposed and interconnected pores is an aggregate ofacidic rocks due to its light color and composition ofSiO2 gt 65 [20] e perlite structure allows it to retainlarge amounts of interstitial water

e aggregate aliven (Figure 3) corresponds to a ther-mally expanded clay spherically shaped and rough surfacemost of which are spheres with their porous interior withsome interconnected pores surrounded by a brownishvitrified layer of varying thickness and smaller porosity(Figure 3(b)) In Figures 2(c) and 3(c) for perlite and alivenrespectively the shape size and distribution of their porescan be appreciated For nanosilica in Figure 4 individualspheres of particle diameters between 20 nm and 70 nm areobserved

24 Physical Characterization e water absorption test wasperformed for each type of aggregate according to the speci-fications of ACI 2112 and density according to ASTM C 127[18] and this process consists of immersing the aggregatesample in water for 24 hours to essentially fill the pores It isthen removed from the water the water dried from the surfaceof the particles and the mass determined Subsequently thevolume of the sample is determined by the displacement ofwater method Finally the sample is oven-dried and the mass

determined Using themass values thus obtained and formulasin this test method it is possible to calculate relative densityand absorption

Surface area was determined through the BET test bychemisorption e water absorption of the LWA (Table 2)shows a higher absorption value for perlite due to its greaterspecific surface area and its open and exposed porosity and

(a) (b) (c)

Figure 2 LWA perlite (a) real scale (b) micrograph to 32x and (c) SEM micrograph to 500x

(a) (b)(c)

Figure 3 LWA aliven (a) real scale (b) micrograph to 32x and (c) SEM micrograph to 500x

Figure 4 TEM micrograph of nanosilica


characteristics that confer low densities of 3055 kgm3 Forthe aggregate aliven its density is 5199 kgm3 because it isa porousmaterial in its interior with the pore sizes of the orderof 10 μm to 500 μm and the water absorption is lower becausein the outer layer of its structure the pore size is smaller thanthe capillary thus inhibiting the migration of water into theaggregate (Figure 3(c)) NS has a large specific surface areaaccording to its size which is an indicator of its reactivity

25 Preparation of Test Samples for Compressive Strength andSulfate Attack In the design of mixtures two lightweightaggregates were used in the coarse state through sieve 38Primeand retained in sieve no 4 perlite and aliven at a rate of325 kgm3 of concrete cement 500 kgm3 of concretewatercementitious-material ratio (amc) of 035 and ad-dition of 10 nanosilica in replacement by weight of thecement content

From previous researches [7] and the literature review[11 21ndash24] a ratio of 035 amc was selected allowing goodworkability so as not to require the use of a superplasticizerin the mixture which could lead to modifications in themicrostructure of the ITZ and cementitious matrix of in-terest in this studye proportion of cement of 500 kgm3 isthe product of the bibliographical revision for which insome studies compressive strength in LWC greater than175MPa [7 21 25ndash27] was achieved e use of 10 ofnanosilica was due to the previous results [16] where it wasobserved that the optimal replacement of cement by sus-pended silica nanoparticles was in this percentage since thecompressive strength increased considerably with respect toa control sample in addition the pore network in thecementitious matrix decreased and its tortuosity increasedas well which decreased the penetration of aggressiveagents [16]

e concrete mixtures were made according to the se-lected parameters and also cubic test samples were fabri-cated with 50mm side for unconfined compressive strengthtest and prismatic test samples of 25mmtimes 25mmtimes 285mmas established by ASTM C157 M [28] to evaluate resistanceto sulfate attacks Once fabricated the cubic test tubes weresubjected to a wet curing process in water saturated withlime at a room temperature of 23plusmn 2degC until the ages of 7and 28 days ages in which the compressive strength thevolume of pores and the absorption of water were de-termined e prisms for the concrete expansion test werecured under the same conditions for 28 days and thensubjected to the attack of magnesium sulfate

26 Immersion in Magnesium Sulfate At the end of thenormal curing time the prisms were submerged for 15

weeks in a 5 mass solution of magnesium sulfate (MgSO4)at pH 7 to evaluate the attack of these sulfates accordingto ASTM C1012 [29] e longitudinal change of theprismatic test samples was measured after being submergedin the MgSO4 solution e solution was changed monthlyand during weekly time intervals the pH was controlled tomaintain it between 6 and 7 units

3 Results and Discussion

31 Compressive Strength of Lightweight Concretes (LWC)e concretes manufactured with perlite and aliven weresubmitted to tests of compressive strength after 7 and 28days of normal curing In Table 3 the results for compressivestrength of LWCwith and without nanosilica are shownesample AL corresponds to the concretes manufactured withLWA aliven and the sample PE to concretes with perlite C5means that all concretes were made with a proportion ofcement of 500 kgm3 Samples with 10 of nanosilica areALC5-10 and PEC5-10 On the contrary the sampleswithout nanosilica are ALC5-0 and PEC5-0

e best results of compressive strength correspond tothe concrete manufactured with aliven with the averagevalues of 263MPa and 221MPa at 28 days of normal curingfor concrete without and with addition of NS respectivelyWhile for perlite concretes only 104MPa without additionand 99MPa with NS were achieved and these values whentaking into account the standard deviation were statisticallyequal For perlite samples the compressive strength resultswere statistically the same for both the ages evaluated and thepercentages of NS used is means that it is the perlite thatlimits the maximum compressive strength that these mix-tures can reach In both concretes the addition of nanosilicais not reflected in an increase in the compressive strengthbecause in LWC the fault is given first by the aggregate andnot by the matrix [21 30] as it happens in the conventionalconcretes e concrete with the aggregate of aliven hasa greater compressive strength because this aggregate ischaracterized by having a vitrified layer on its surface thatgives it greater hardness as well as mechanical resistance

32 Expansion of Concretes Figure 5 shows the results ofchange in the length of all bars under sulfate attack Untilweek 4 all the samples have a very low expansion (002)but from this time there is a clear difference in the behaviorof the samples with perlite compared to the samples withaliven e bars with perlite present an increasing expansion

Table 2 Physical properties of aggregates and NS

Surface area(m2g)

Apparent relativedensity (kgm3)

Waterabsorption ()

PE 210 3055 420AL 113 5199 103NS 5140 112 mdash

Table 3 Compressive strength of LWC manufactured with perlite(PEC) and with aliven (ALC) to 7 and 28 days with and withoutaddition of NS

SampleCompressivestrength at

7 days (MPa)

Compressivestrength at

28 days (MPa)PEC5-0 81plusmn 19 104plusmn 13PEC5-10 124plusmn 34 99plusmn 29ALC5-0 238plusmn 01 263plusmn 15ALC5-10 152plusmn 25 221plusmn 10


with the time of immersion in sulfates reaching values of044 for PEC5-0 and 02 for PEC5-10 in the 15 weekstested However the samples with aliven show practically noexpansion (005) during the whole time evaluated

For concretes made with both perlite and aliven sampleswith a 10 of nanosilica blended exhibit better behavior toattack by magnesium sulfate with the perlite aggregateconcrete being the weakest ese results are in accordancewith the results of Tobon et al [31] who analyzed the be-havior of normal weight Portland cement mortars blendedwith nanosilica when they are subjected to attack of this kindof sulfate ese researchers showed how 5 replacement ofPortland cement by nanosilica in these mortars practicallycontrols the expansion by the attack of sulfates is can beexplained from different points of view First the concreteswith NS undergo a refinement of the pore structure [13]Second the perlite alumina may be more reactive andsusceptible due to its volcanic origin to this attack than theone exhibited in the aliven Because as some authors havesuggested [32 33] the reactivity of the alumina present inthe mineral additions is critical in the durability of thecementitious mixtures manufactured with them ird al-though the alumina content of the perlite is lower comparedto that of the aliven the alumina in the perlite is moreexposed to this attack due to its surface porosity

In accordance with ASTM C 1157 [34] a conventionalconcrete manufactured with a cement of moderate re-sistance to sulfates admits a maximum value of 010 ofexpansion erefore the lightweight concrete manufac-tured with aliven as a coarse aggregate presents a perfor-mance against the attack by sulfates similar to those expectedby a conventional concrete

33 Pore Volume and Water Absorption e pore volumeandwater absorption for the concretes studied were determined

at 28 days of curing and in accordance with ASTM C 642 [35]for which the pore volume corresponds to the water saturablepores of the concrete aggregate porosity and cementitiousmatrix Table 4 shows that for the aliven concrete the porevolume is significantly lower between 234 for ALC5-10 and241 for ALC5-0 For the perlite concretes it is of the order of324 for PEC5-0 and 313 for PEC5-10 is behavior in-dicates that the nanosilica can reduce pore volume in LWC 3in aliven concrete and 33 in perlite However it can beestablished from the results obtained that the volume of pores inthe LWC depends to a large extent on themorphology and typeof porosity of the LWA Concretes manufactured with poroussurface aggregates and interconnected pores in the interior suchas perlite which possess greater water absorption (42 Table 2)result in concretes with the greater volume of permeable poreswhereas concretes with aggregates of lower water absorption asaliven (103 Table 2) have a lower volume of pores

e results of water absorption (Table 4) of concreteswith aliven have a lower percentage of water absorption thanthose manufactured with perlite In both concretes thebehavior for water absorption is decreasing by adding 10 ofnanosilica and the same order of pore volume results

e addition of nanosilica affects the water absorption oflight concrete although the concrete has a considerablevolume of pores mainly attributed to the aggregates thecementitious matrix is densified by the addition of NS thusinhibiting the interconnection of pores that allow the mi-gration of water from the matrix to the aggregate andconsequently decreasing the water absorption in a lowproportion of the order of 43 for the concrete of addedaliven and 52 in the perlite concrete added with NS esamples with the lowest percentage of expansion are thosewith NS in their formulation (ALC5-10 and PEC5-10)

It can be stated that both the pore volume and the waterabsorption of the LWC are reduced with the addition of NSbut they are conditioned mainly by the type of LWA usedus in this case using light aggregates with porosity andinterconnected pores as perlite LWC are obtained withhigher volume of pores and greater water absorption whichis reflected in concrete with less mechanical resistance tocompression and less durability in terms of resistance to theattack of the sulfates

34 Morphology of Concretes Exposed to Attack by SulfatesAfter the 15 weeks of exposure to magnesium sulfate it canbe seen that the perlite concretes are affected to a greaterextent by magnesium sulfate causing a warpage of 325mmin the exposed joints of nonadded concrete (Figure 6(a)) and275mm for joints of added concrete (Figure 6(b)) When

ex

pans

ion

05

04

03

02

01

00

ndash1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16Immersion time (weeks)

ALC5-0ALC5-10

PEC5-0PEC5-10

Figure 5 Length change of LWC ALC5 and PEC5 with andwithout addition of 10 nanosilica

Table 4 Volume of voids and water absorption of concretesmanufactured with perlite (PEC) and with aliven (ALC) with andwithout addition of NS

Sample Volume of voids () Water absorption ()PEC5-0 324 362PEC5-10 313 342ALC5-0 241 229ALC5-10 234 219


looking at aliven concretes only the nonadded samplesexhibit a slight warpage behavior around 08mm (Figure7(a)) while the nanosilica-added concrete remains intact(Figure 7(b))is warpage behavior reflects the longitudinalchange produced by the expansion of the concrete thusvalidating the expansion results of Figure 5

In addition it can be seen that the sample added withnanosilica (Figure 7(b)) presents a greater surface degra-dation than the sample not added (Figure 7(a)) As is knownthe nanosilica reacts with Ca(OH)2 forming a C-S-H gel asthere is more of this gel MgSO4 could eventually react withit forming M-S-H on the surface causing the deteriorationobserved in the image since that this product as mentionedhas a low cohesion [4]

To identify the cause of warping and expansion of con-cretes micrographs were taken at the edge of the beam for

aliven concretes (Figure 8) in the ITZ (Figure 9) and insidethe aggregate (Figure 10)

In Figure 8(a) it can be seen that the edge of the concretesample of aliven without addition of nanosilica shows cracksrough EDX the elemental chemical composition on thesurface was identified with the presence of calcium (30)silica (7) sulfur (11) magnesium (5) and oxygen (45)on the surface (Figure 11) is chemical composition cor-responds mineralogically to the transformation of C-S-H toM-S-H and other mineral phases present (Figure 8) that dueto the chemical composition it can be concluded that gypsumis formed (CaSO4) which for graphic effects will be abbre-viated as CS [10]

When analyzing the ITZ of the concretes attacked byMgSO4 in aliven concretes mainly the presence of CS andC-S-H (Figure 9) is observed Once MgSO4 permeates the

(a) (b)

Figure 6 Concrete exposed to MgSO4 (a) PEC5S-0 and (b) PEC5S-10

(a) (b)

Figure 7 Concrete exposed to MgSO4 (a) ALC5S-0 and (b) AlC5S-10

30 μm EHT = 1500 kVWD = 95 mm

Signal A = SE1Filament age = 7527 hours

Date 17 June 2016Mag = 500x

M-S-H

Crack

(a)

2 μm EHT = 1500 kVWD = 90 mm


Date 17 June 2016Mag = 500Kx

CS

(b)

Figure 8 Border to the specimen of (a) ALC5S-0 and (b) AlC5S-10


interior of the aggregates in the case of aliven it is observedby EDS that the main composition corresponds to oxygen in52 silicon 2125 aluminum 1232 and low values ofcalcium iron and magnesium Such composition corre-sponds to the aggregate that is an aluminosilicate but theamounts of magnesium are due to the deposition of lowamounts ofM-S-H bymigration of sulfate to the interior dueto the porosity of the aggregate (Figure 10) As can be seen inthe micrographs the disappearance of CH causes a drop inpH in the pores which is sufficient to cause the de-composition of C-S-H and thus provide the active silicanecessary for the formation of M-S-H [14]

For the perlite concretes (Figure 12) the same behavioris observed at the edge as for the aliven concretes In the ITZ

(Figure 13) there is a presence of M-S-H by degradation ofC-S-H gypsum and ettringite in the case of concrete withthe addition of nanosilica which is appreciable as prismaticcrystals is ettringite can be produced by the reactionbetween C3A and gypsum formed from the reaction of C-S-H and Mg(OH)2 according to (2)

Inside the aggregates of the perlite concrete can benoticed the presence of gypsum crystals (CS) (Figure 14) ByEDX the elemental composition corresponds mainly tooxygen silicon calcium sulfur and aluminum Minor traceamounts of magnesium were also found to a lesser extentDue to its porous structure magnesium sulfate permeatesthe concrete until the interior of the aggregate

As mentioned above when CH reacts with MgSO4 inthe presence of water according to [36] gypsum andbrucite are formed but the pozzolanic addition in the caseof nanosilica avoids the production of brucite but not thedecalcification of the C-S-H because NS consumes calciumhydroxide which is not available for the production ofmagnesium hydroxide or brucite is can be observed inthe micrographs of Figures 8 12 and 13 where there isno evidence of hexagonal brucite crystals but there areM-S-H

In this study the aggregate of perlite presented higherwater absorption which led to a concrete with greaterpermeability and pore volume Because of this when usingthis type of lightweight aggregate its high porosity content

2 μm EHT = 1500 kVWD = 85 mm



CS

(a)

2 μm EHT = 1500 kVWD = 80 mm



CS

(b)

Figure 9 ITZ of (a) ALC5S-0 and (b) AlC5S-10

2 μm EHT = 1500 kVWD = 85 mm



CS

(a)

2 μm EHT = 1500 kVWD = 85 mm



CS

(b)

Figure 10 Aggregate zone of (a) ALC5S-0 and (b) AlC5S-10

S

S

Si

Ca

O

Fe

Mg

Al

Ca

Ca

Spectrum 3

05 1 15 2 25 3 35 4 45 5Full scale 35674 cts cursor 0154 (802 cts) keV

Figure 11 EDX on the border to the specimen of ALC5S-0


must be taken into account and also that these pores areusually interconnected When subjecting this concrete tothe sulfate attack it was found to have a high degree ofexpansion notorious after eight weeks of immersion dueto its high permeability and most likely to the presence ofreactive alumina e substitution of cement by 10 ofnanosilica allowed us to densify the matrix and reduce theporosity and permeability of the concrete manufacturedwith this aggregate which was reflected in a smaller ex-pansion of this one compared to the concrete without thereplacement of the cement Unlike perlite aliven presented

smaller expansion both with the replacement of the cementby 10 of nanosilica as without this oneis behavior is dueto the lower water absorption of the aggregate and to that itproduces a concrete with a permeability and pore volumeconsiderably lower than that produced with perlite

4 Conclusions

e greatest expansion of lightweight perlite concretes isattributed to the direct migration of magnesium sulfate tothe aggregate because it is an open porous surface aggregate

1 μm EHT = 1500 kVWD = 85 mm



M-S-H

(a)

2 μm EHT = 1500 kVWD = 85 mm



M-S-H

CS

C-S-H

(b)

Figure 12 Border to the specimen of (a) PEC5S-0 and (b) PEC5S-10

1 μm EHT = 1500 kVWD = 80 mm



M-S-H

CS

(a)

2 μm EHT = 1500 kVWD = 80 mm



CS

Ettringite

(b)

Figure 13 ITZ of (a) PEC5S-0 and (b) PEC5S-10

2 μm EHT = 1500 kVWD = 80 mm



CS

(a)

2 μm EHT = 1500 kVWD = 75 mm



CS

(b)

Figure 14 Aggregate zone of (a) PEC5S-0 and (b) PEC5S-10


versus aliven porous structure covered by a vitrified layer oflow permeability porosity and this migration of the sulfateion allows the degradation of the C-S-H transforming it intoM-S-H and in turn allowing the formation of gypsum that isresponsible for expanding the concrete leading to the pointof warping of concrete test tubes without the addition ofnanosilica

e use of nanosilica in the LWC refines the porestructure in the cementitious matrix as well as in the ITZ byincreasing the formation of C-S-H but this densification ofthe cementitious matrix is not high enough to impede themigration of water and sulfate ions from the exterior to theinterior of the concrete until reaching the aggregate as canbe seen in the case of perlite

e use of nanosilica decreased the expansion in theconcretes preventing the formation of brucite because whenthere is a reaction between CH and nanosilica there is littleCH available for the reaction with magnesium sulfate andthe subsequent formation of brucite (MH)

Factors such as aggregate porosity and chemical com-position are more important in the durability of lightweightconcretes despite the refining of the cementitious matrixwith the addition of nanosilica the absorption capacity ofthese aggregates favor the migration of the sulfate solutionfrom the outside to the inside concentrating and achievingthat it affects the whole cementitious matrix and not only theexposed surface of the concrete

e mechanism of reaction against chemical attack bymagnesium sulfate for lightweight concretes is similar to themechanism in conventional concretes where the attack occursmainly on the C-S-H but it has the aggravating circumstancethat this attack can be enhanced by the type of lightweightaggregate that has been used that is to say with exposedporosity as perlite or closed porosity as calcined clay

A concrete manufactured with lightweight aggregates ofclosed porosity as the calcined clay can show a similarperformance to the conventional concrete against the ag-gressive sulfate attack like the magnesium sulfate due to theexhibition of less expansion than 010 this value is suitablein standard for a conventional concrete considering thebehavior of this lightweight concretes to the compressionstrength

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that they have no conflicts of interest

Acknowledgments

is work had been endorsed by the ldquoNational Program ofProjects to Strengthen Research Development and In-novation in Postgraduate Studies at Universidad Nacional deColombiardquo Code 30474

References

[1] M Collepardi ldquoA state-of-the-art review on delayed ettringiteattack on concreterdquo Cement and Concrete Composites vol 25no 4-5 pp 401ndash407 2003

[2] P K Mehta and P J M Monteiro Concrete MicrostructureProperties and Materials McGraw-Hill Education New YorkNY USA 3rd edition 2006

[3] V Rheinheimer Sulphate Attack and the Role of aumasitein Historical Constructions Technical University of CataluntildeaBarcelona Spain 2008

[4] M Santhanam M D Cohen and J Olek ldquoMechanism ofsulfate attack a fresh look part 1 summary of experimentalresultsrdquo Cement and Concrete Research vol 32 no 6pp 915ndash921 2002

[5] E Ganjian and H S Pouya ldquoEffect of magnesium and sulfateions on durability of silica fume blended mixes exposed to theseawater tidal zonerdquo Cement and Concrete Research vol 35no 7 pp 1332ndash1343 2005

[6] M A Bedoya Efecto de los Agregados Reciclados y Cenizas deCarbon en la Durabilidad de un Mortero Ecologico Para suAplicacion en Arrecifes Artificiales Ingenierıa en Materiales yProcesos Departamento deMateriales yMinerales UniversidadNacional de Colombia Bogota Colombia 2015

[7] M Ayhan H Gonul I A Gonul and A Karakus ldquoEffect ofbasic pumice on morphologic properties of interfacial tran-sition zone in load-bearing lightweightsemi-lightweightconcretesrdquo Construction and Building Materials vol 25no 5 pp 2507ndash2518 2011

[8] A Elsharief M D Cohen and J Olek ldquoInfluence of light-weight aggregate on the microstructure and durability ofmortarrdquo Cement and Concrete Research vol 35 no 7pp 1368ndash1376 2005

[9] X Liu H Du and M H Zhang ldquoA model to estimate thedurability performance of both normal and light-weightconcreterdquo Construction and Building Materials vol 80pp 255ndash261 2015

[10] H Tanyildizi ldquoe investigation of microstructure andstrength properties of lightweight mortar containing mineraladmixtures exposed to sulfate attackrdquo Measurement vol 77pp 143ndash154 2016

[11] K M A Hossain S Ahmed and M Lachemi ldquoLightweightconcrete incorporating pumice based blended cement and ag-gregate mechanical and durability characteristicsrdquoConstructionand Building Materials vol 25 no 3 pp 1186ndash1195 2011

[12] P Spiesz Q L Yu and H J H Brouwers ldquoDevelopment ofcement-based lightweight composites-part 2 durability-related propertiesrdquo Cement and Concrete Compositesvol 44 pp 30ndash40 2013

[13] H Du S Du and X Liu ldquoEffect of nano-silica on the me-chanical and transport properties of lightweight concreterdquoConstruction and Building Materials vol 82 pp 114ndash1222015

[14] E F Irassar V L Bonavetti and G Menendez ldquoCementos conmaterial calcareo formacion de thaumasita por ataque de sul-fatosrdquo Revista de la Construccion vol 9 no 1 pp 63ndash73 2010

[15] M Lanzon and P A Garcıa-Ruiz ldquoLightweight cementmortars advantages and inconveniences of expanded perliteand its influence on fresh and hardened state and durabilityrdquoConstruction and Building Materials vol 22 no 8pp 1798ndash1806 2008

[16] J I Tobon O J Restrepo and J Paya ldquoComparative analysisof performance of Portland cement blended with nanosilicaand silica fumerdquo Dyna vol 163 pp 37ndash46 2010


[17] O Mendoza G Sierra and J I Tobon ldquoEffect of the reag-glomeration process of multi-walled carbon nanotubes dis-persions on the early activity of nanosilica in cementcompositesrdquo Construction and Building Materials vol 54pp 550ndash557 2014

[18] ASTM C127-15 Standard Test Method for Relative Density(Specific Gravity) and Absorption of Coarse Aggregate AST-MInternational West Conshohocken PA USA 2015 httpwwwastmorg

[19] ASTM C150C150M-16e1 Standard Specification for Port-land Cement ASTM International West Conshohocken PAUSA 2016

[20] J-C Melgarejo Atlas de Asociaciones Minerales en LaminaDelgada Universidad de Barcelona Barcelona Spain 2004

[21] P Vargas O Restrepo-Baena and J I Tobon ldquoMicro-structural analysis of interfacial transition zone (ITZ) and itsimpact on the compressive strength of lightweight concretesrdquoConstruction and Building Materials vol 137 pp 381ndash3892017

[22] Y Ke S Ortola A L Beaucour and H Dumontet ldquoIden-tification of microstructural characteristics in lightweightaggregate concretes by micromechanical modelling includingthe interfacial transition zone (ITZ)rdquo Cement and ConcreteResearch vol 40 no 11 pp 1590ndash1600 2010

[23] D P Bentz ldquoInfluence of internal curing using lightweightaggregates on interfacial transition zone percolation andchloride ingress in mortarsrdquo Cement and Concrete Com-posites vol 31 no 5 pp 285ndash289 2009

[24] Q L Yu P Spiesz and H J H Brouwers ldquoDevelopment ofcement-based lightweight composites-part 1 mix designmethodology and hardened propertiesrdquo Cement and ConcreteComposites vol 44 pp 17ndash29 2013

[25] T Y Lo H Z Cui W C Tang and W M Leung ldquoe effectof aggregate absorption on pore area at interfacial zone oflightweight concreterdquo Construction and Building Materialsvol 22 no 4 pp 623ndash628 2008

[26] J Newman B S Choo and P Owens Advanced ConcreteTechnology Processes Elsevier Ltd New York NY USA 2003

[27] J Newman and P Owens ldquo2-properties of lightweightconcreterdquo in Advanced Concrete Technology pp 3ndash29Butterworth-Heinemann Oxford UK 2003

[28] ASTM C157C157M-08(2014)e1 Standard Test Method forLength Change of Hardened Hydraulic-Cement Mortar andConcrete ASTM International West Conshohocken PAUSA 2014 httpwwwastmorg

[29] ASTM C 1012C1012M-15 Standard Test Method for LengthChange of Hydraulic-Cement Mortars Exposed to a SulfateSolution ASTM International West Conshohocken PA2015httpwwwastmorg

[30] S Chandra and L Berntsson ldquo6-lightweight aggregate con-crete microstructurerdquo in Lightweight Aggregate Concretepp 131ndash166 William Andrew Publishing Norwich NY USA2002

[31] J I Tobon J Paya and O J Restrepo ldquoStudy of durability ofPortland cement mortars blended with silica nanoparticlesrdquoConstruction and Building Materials vol 80 pp 92ndash97 2015

[32] R Talero ldquoExpansive synergic effect of ettringite from poz-zolan (metakaolin) and from OPC co-precipitating ina common plaster-bearing solution part I by cement pastesand mortarsrdquo Construction and Building Materials vol 24no 9 pp 1779ndash1789 2010

[33] R Talero ldquoExpansive synergic effect of ettringite from poz-zolan (metakaolin) and from OPC co-precipitating ina common plaster-bearing solution part II fundamentals

explanation and justificationrdquo Construction and BuildingMaterials vol 25 no 3 pp 1139ndash1158 2011

[34] ASTMC1157C1157M-17 StandardPerformance Specification forHydraulic Cement ASTM International West ConshohockenPA USA 2017

[35] ASTM C642-13 Standard Test Method for Density Absorp-tion and Voids in Hardened Concrete PA USA 2013 httpwwwastmorg

[36] S T Lee H Y Moon and R N Swamy ldquoSulfate attack androle of silica fume in resisting strength lossrdquo Cement andConcrete Composites vol 27 no 1 pp 65ndash76 2005


International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018


Active and Passive Electronic Components

VLSI Design



Shock and Vibration


Civil EngineeringAdvances in

Acoustics and VibrationAdvances in



Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

Journal of



Journal ofEngineeringVolume 2018

SensorsJournal of



RotatingMachinery


Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018


Chemical EngineeringInternational Journal of Antennas and

Propagation




Navigation and Observation


Hindawi

wwwhindawicom Volume 2018

Advances in

Multimedia

Submit your manuscripts atwwwhindawicom

pores in the cement paste hydrated by the reaction with theportlandite and the formation of brucite [2] MgSO4 reactsmainly with the hydration products of the cement the reactionof the sulfate with calcium hydroxide released during the hy-dration of the cement forms calcium sulfates (gypsumCaSO4 middot H2O) andmagnesium hydroxide (brucite Mg(OH)2)according to the following reaction [3]

MgSO4 + Ca(OH)2 + 2H2OrarrCaSO4 middot 2H2O + Mg(OH)2

(1)

Another possible effect of magnesium sulfate is the re-action with the C-S-H gel where due to the decalcificationproduced by this sulfate a hydrated magnesium silicate isobtained M-S-H which is a poor cohesive gel [4] non-cementitious which leads to softening of the cement matrix[5 6] according to the following reaction In addition asa result of this reaction gypsum and hydrated silica areproduced

C-S-H + MgSO4rarrCaSO4 middot 2H2O + M-S-H (2)

is gypsum produced in (2) could react with C3A toproduce ettringite as shown in the following reaction [1]

CaSO4 middot 2H2O + Al2O3 middot 3CaO + 26H2O

rarrCa6Al2 SO4( 11138573(OH)12 middot 26H2O(3)

In the presence of carbonates and under the appropriateenvironmental conditions the formation of thaumasite(CaSiO3 middot CaSO4 middot CaCO3 middot 15H2O) can be produced asshown in the following reaction [3]

nSiO2 middot H2O + CaOH + CaCO3 + MgSO4

rarrCaSiO3 middot CaSO4 middot CaCO3 middot 15H2O

+ CaSO4 middot 2H2O + Mg(OH)2

(4)

To fully appreciate lightweight concrete it is essential tounderstand the intrinsic nature of lightweight aggregates(LWA) and how they influence the properties of concretemade from them e LWA have an array of vesicles or airvoid within their masse size spacing and interconnectionof the vesicles make these aggregates capable of producingconcrete with lower density close to 1850 kgm3 with ad-vantages such as increased thermal insulation extendedmoistcuring and increased durability [7]

e effect of lightweight aggregates on both the mi-crostructure and durability of mortars and concretes hasbeen studied by several researchers [8ndash12] Finding that lightaggregates affect the microstructure of the interfacial tran-sition zone (ITZ) of porous quality which has been im-proved with the addition of fly ash and silica fume findingthat in order to improve resistance to sulfate attack withthese materials the content of fly ash or natural pozzolanshould be between 25 and 35 by mass while for silica fumebetween 7 and 15 (ACI 201-2) [13ndash15] e addition ofsuch materials significantly reduces the permeability of theconcrete and also when combined with the alkalis and thecalcium hydroxide which are released during the hydrationof the cement the potential for gypsum formation reduces

Nanosilica (NS) has been widely recognized as an activeadditive to cement [16 17] Its activity accelerates the hy-dration reaction by means of the nucleation mechanism(early activity) for the formation of C-S-H and its pozzo-lanic activity increases the production of C-S-H Addi-tionally NS also acts as a filler decreasing the waterabsorption that allows us to improve the durability of thecementitious matrix [9 10]

is work focuses on the study of the morphology andcomposition (chemical and mineralogical) of the LWA thereplacement of cement by nanosilica in the formation of themicrostructure and the thickness of the ITZ and the in-fluence of this on the resistance to attack by magnesiumsulfate in lightweight concretes

2 Materials and Methods

For themanufacture of concretes ordinary Portland cementnanosilica (NS) and two lightweight aggregates thermallyexpanded clay aliven (AL) and perlite (PE) as well wereused

e methodology proposed for the development of thisresearch is divided into three main activities chemicalmineralogical and physical characterization of rawmaterialsthrough X-ray diffraction (XRD) scanning electron mi-croscopy (SEM) optical microscopy (OM) specific surfacearea (BET) and density and water absorption of aggregates(ASTMC 127 [18]) e second stage consisted in the designand preparation of the concretes and finally the study of themechanical properties and durability of the LWC

21 Chemical Characterization of Materials e chemicalcomposition of cement nanosilica perlite and expandedclay was determined by X-ray fluorescence (XRF) using ARL8680 S equipment in boron lithium oxide (B4Li2O7) pills InTable 1 it can be seen that silicon oxide is present in a greaterproportion for both aggregates being higher in perlite(7245) than in aliven (5967) e second componentpresent in greater quantity in both aggregates is aluminumoxide but unlike SiO2 aliven has a higher content of Al2O3in comparison with the perlitee NS used is of high purityemain constituent of the cement is calcium oxide presentin 6069 followed by 20 silicon oxide and lower pres-ence of sulfur of interest in this research e chemical

Table 1 Chemical composition of materials

Chemical compositionWeight ()

Perlite Aliven NS CementSilicon oxide (SiO2) 7245 5967 9356 209Titanium oxide (TiO2) 022 119 002 021Aluminum oxide (Al2O3) 1338 1695 000 472Iron oxide (Fe2O3) 135 979 039 320Magnesium oxide (MgO) 008 413 013 180Calcium oxide (CaO) 120 357 022 6069Sodium oxide (Na2O) 340 207 062 037Potassium oxide (K2O) 457 128 002 061Sulfur oxide (SO3) 009 004 030 013Ignition losses at 1000degC 292 075 446 368







Inte

nsity

(cou

nts)

5000

4500

4000

3500

3000

2500

2000

1500

1000

Q

A

0 10 20 30 40 50 60 70Position (2 theta)

Q quartzA albite

(a)

Inte

nsity

(cou

nts)

20000

18000

16000

14000

12000

10000

8000

6000

4000

2000

Q QH A

Q A QA Q A Q

Q

0 10 20 30 40 50 60 70Position (2 theta)


A albiteHE hematite

(b)

Inte

nsity

(cou

nts)

700

600

500

400

300

200

100

0

Position (2 theta)0 10 20 30 40 50 60 70

(c)








(a) (b) (c)


(a) (b)(c)















Surface area(m2g)


Waterabsorption ()

PE 210 3055 420AL 113 5199 103NS 5140 112 mdash



7 days (MPa)













ex

pans

ion

05

04

03

02

01

00


ALC5-0ALC5-10

PEC5-0PEC5-10











(a) (b)


(a) (b)


30 μm EHT = 1500 kVWD = 95 mm



M-S-H

Crack

(a)

2 μm EHT = 1500 kVWD = 90 mm



CS

(b)









2 μm EHT = 1500 kVWD = 85 mm



CS

(a)

2 μm EHT = 1500 kVWD = 80 mm



CS

(b)


2 μm EHT = 1500 kVWD = 85 mm



CS

(a)

2 μm EHT = 1500 kVWD = 85 mm



CS

(b)


S

S

Si

Ca

O

Fe

Mg

Al

Ca

Ca

Spectrum 3






4 Conclusions


1 μm EHT = 1500 kVWD = 85 mm



M-S-H

(a)

2 μm EHT = 1500 kVWD = 85 mm



M-S-H

CS

C-S-H

(b)


1 μm EHT = 1500 kVWD = 80 mm



M-S-H

CS

(a)

2 μm EHT = 1500 kVWD = 80 mm



CS

Ettringite

(b)


2 μm EHT = 1500 kVWD = 80 mm



CS

(a)

2 μm EHT = 1500 kVWD = 75 mm



CS

(b)









Data Availability




Acknowledgments


References










































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia







Inte

nsity

(cou

nts)

5000

4500

4000

3500

3000

2500

2000

1500

1000

Q

A

0 10 20 30 40 50 60 70Position (2 theta)

Q quartzA albite

(a)

Inte

nsity

(cou

nts)

20000

18000

16000

14000

12000

10000

8000

6000

4000

2000

Q QH A

Q A QA Q A Q

Q

0 10 20 30 40 50 60 70Position (2 theta)


A albiteHE hematite

(b)

Inte

nsity

(cou

nts)

700

600

500

400

300

200

100

0

Position (2 theta)0 10 20 30 40 50 60 70

(c)








(a) (b) (c)


(a) (b)(c)















Surface area(m2g)


Waterabsorption ()

PE 210 3055 420AL 113 5199 103NS 5140 112 mdash



7 days (MPa)













ex

pans

ion

05

04

03

02

01

00


ALC5-0ALC5-10

PEC5-0PEC5-10











(a) (b)


(a) (b)


30 μm EHT = 1500 kVWD = 95 mm



M-S-H

Crack

(a)

2 μm EHT = 1500 kVWD = 90 mm



CS

(b)









2 μm EHT = 1500 kVWD = 85 mm



CS

(a)

2 μm EHT = 1500 kVWD = 80 mm



CS

(b)


2 μm EHT = 1500 kVWD = 85 mm



CS

(a)

2 μm EHT = 1500 kVWD = 85 mm



CS

(b)


S

S

Si

Ca

O

Fe

Mg

Al

Ca

Ca

Spectrum 3






4 Conclusions


1 μm EHT = 1500 kVWD = 85 mm



M-S-H

(a)

2 μm EHT = 1500 kVWD = 85 mm



M-S-H

CS

C-S-H

(b)


1 μm EHT = 1500 kVWD = 80 mm



M-S-H

CS

(a)

2 μm EHT = 1500 kVWD = 80 mm



CS

Ettringite

(b)


2 μm EHT = 1500 kVWD = 80 mm



CS

(a)

2 μm EHT = 1500 kVWD = 75 mm



CS

(b)









Data Availability




Acknowledgments


References










































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia







(a) (b) (c)


(a) (b)(c)















Surface area(m2g)


Waterabsorption ()

PE 210 3055 420AL 113 5199 103NS 5140 112 mdash



7 days (MPa)













ex

pans

ion

05

04

03

02

01

00


ALC5-0ALC5-10

PEC5-0PEC5-10











(a) (b)


(a) (b)


30 μm EHT = 1500 kVWD = 95 mm



M-S-H

Crack

(a)

2 μm EHT = 1500 kVWD = 90 mm



CS

(b)









2 μm EHT = 1500 kVWD = 85 mm



CS

(a)

2 μm EHT = 1500 kVWD = 80 mm



CS

(b)


2 μm EHT = 1500 kVWD = 85 mm



CS

(a)

2 μm EHT = 1500 kVWD = 85 mm



CS

(b)


S

S

Si

Ca

O

Fe

Mg

Al

Ca

Ca

Spectrum 3






4 Conclusions


1 μm EHT = 1500 kVWD = 85 mm



M-S-H

(a)

2 μm EHT = 1500 kVWD = 85 mm



M-S-H

CS

C-S-H

(b)


1 μm EHT = 1500 kVWD = 80 mm



M-S-H

CS

(a)

2 μm EHT = 1500 kVWD = 80 mm



CS

Ettringite

(b)


2 μm EHT = 1500 kVWD = 80 mm



CS

(a)

2 μm EHT = 1500 kVWD = 75 mm



CS

(b)









Data Availability




Acknowledgments


References










































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia













Surface area(m2g)


Waterabsorption ()

PE 210 3055 420AL 113 5199 103NS 5140 112 mdash



7 days (MPa)













ex

pans

ion

05

04

03

02

01

00


ALC5-0ALC5-10

PEC5-0PEC5-10











(a) (b)


(a) (b)


30 μm EHT = 1500 kVWD = 95 mm



M-S-H

Crack

(a)

2 μm EHT = 1500 kVWD = 90 mm



CS

(b)









2 μm EHT = 1500 kVWD = 85 mm



CS

(a)

2 μm EHT = 1500 kVWD = 80 mm



CS

(b)


2 μm EHT = 1500 kVWD = 85 mm



CS

(a)

2 μm EHT = 1500 kVWD = 85 mm



CS

(b)


S

S

Si

Ca

O

Fe

Mg

Al

Ca

Ca

Spectrum 3






4 Conclusions


1 μm EHT = 1500 kVWD = 85 mm



M-S-H

(a)

2 μm EHT = 1500 kVWD = 85 mm



M-S-H

CS

C-S-H

(b)


1 μm EHT = 1500 kVWD = 80 mm



M-S-H

CS

(a)

2 μm EHT = 1500 kVWD = 80 mm



CS

Ettringite

(b)


2 μm EHT = 1500 kVWD = 80 mm



CS

(a)

2 μm EHT = 1500 kVWD = 75 mm



CS

(b)









Data Availability




Acknowledgments


References










































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia











ex

pans

ion

05

04

03

02

01

00


ALC5-0ALC5-10

PEC5-0PEC5-10











(a) (b)


(a) (b)


30 μm EHT = 1500 kVWD = 95 mm



M-S-H

Crack

(a)

2 μm EHT = 1500 kVWD = 90 mm



CS

(b)









2 μm EHT = 1500 kVWD = 85 mm



CS

(a)

2 μm EHT = 1500 kVWD = 80 mm



CS

(b)


2 μm EHT = 1500 kVWD = 85 mm



CS

(a)

2 μm EHT = 1500 kVWD = 85 mm



CS

(b)


S

S

Si

Ca

O

Fe

Mg

Al

Ca

Ca

Spectrum 3






4 Conclusions


1 μm EHT = 1500 kVWD = 85 mm



M-S-H

(a)

2 μm EHT = 1500 kVWD = 85 mm



M-S-H

CS

C-S-H

(b)


1 μm EHT = 1500 kVWD = 80 mm



M-S-H

CS

(a)

2 μm EHT = 1500 kVWD = 80 mm



CS

Ettringite

(b)


2 μm EHT = 1500 kVWD = 80 mm



CS

(a)

2 μm EHT = 1500 kVWD = 75 mm



CS

(b)









Data Availability




Acknowledgments


References










































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia








(a) (b)


(a) (b)


30 μm EHT = 1500 kVWD = 95 mm



M-S-H

Crack

(a)

2 μm EHT = 1500 kVWD = 90 mm



CS

(b)









2 μm EHT = 1500 kVWD = 85 mm



CS

(a)

2 μm EHT = 1500 kVWD = 80 mm



CS

(b)


2 μm EHT = 1500 kVWD = 85 mm



CS

(a)

2 μm EHT = 1500 kVWD = 85 mm



CS

(b)


S

S

Si

Ca

O

Fe

Mg

Al

Ca

Ca

Spectrum 3






4 Conclusions


1 μm EHT = 1500 kVWD = 85 mm



M-S-H

(a)

2 μm EHT = 1500 kVWD = 85 mm



M-S-H

CS

C-S-H

(b)


1 μm EHT = 1500 kVWD = 80 mm



M-S-H

CS

(a)

2 μm EHT = 1500 kVWD = 80 mm



CS

Ettringite

(b)


2 μm EHT = 1500 kVWD = 80 mm



CS

(a)

2 μm EHT = 1500 kVWD = 75 mm



CS

(b)









Data Availability




Acknowledgments


References










































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia








2 μm EHT = 1500 kVWD = 85 mm



CS

(a)

2 μm EHT = 1500 kVWD = 80 mm



CS

(b)


2 μm EHT = 1500 kVWD = 85 mm



CS

(a)

2 μm EHT = 1500 kVWD = 85 mm



CS

(b)


S

S

Si

Ca

O

Fe

Mg

Al

Ca

Ca

Spectrum 3






4 Conclusions


1 μm EHT = 1500 kVWD = 85 mm



M-S-H

(a)

2 μm EHT = 1500 kVWD = 85 mm



M-S-H

CS

C-S-H

(b)


1 μm EHT = 1500 kVWD = 80 mm



M-S-H

CS

(a)

2 μm EHT = 1500 kVWD = 80 mm



CS

Ettringite

(b)


2 μm EHT = 1500 kVWD = 80 mm



CS

(a)

2 μm EHT = 1500 kVWD = 75 mm



CS

(b)









Data Availability




Acknowledgments


References










































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia




4 Conclusions


1 μm EHT = 1500 kVWD = 85 mm



M-S-H

(a)

2 μm EHT = 1500 kVWD = 85 mm



M-S-H

CS

C-S-H

(b)


1 μm EHT = 1500 kVWD = 80 mm



M-S-H

CS

(a)

2 μm EHT = 1500 kVWD = 80 mm



CS

Ettringite

(b)


2 μm EHT = 1500 kVWD = 80 mm



CS

(a)

2 μm EHT = 1500 kVWD = 75 mm



CS

(b)









Data Availability




Acknowledgments


References










































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia








Data Availability




Acknowledgments


References










































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia


























RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia


Performance and Microstructural Analysis of Lightweight ...Feb 13, 2018 · 325kg/m3 of concrete,...

Documents

Transcript of Performance and Microstructural Analysis of Lightweight ...Feb 13, 2018 · 325kg/m3 of concrete,...