SCIÉNDO INGENIUM

ISSN 3084-7788 (En línea) Scién. inge. 21(2): 57-68, (2025)

Assessment of cement-based boards reinforced with fibers extracted

from Andean Ichu grass

C. Palomino^1*

; G. Hinostroza²

; S. Candiotti²

; H. Savastano-Junior³

S. Charca²

;

¹Department of Materials Engineering, Universidad Nacional de Trujillo, Av. Juan Pablo II s/n, Trujillo, 13006, Perú.

²Department of Mechanical Engineering, Universidad de Ingenieria y Tecnologia – UTEC, Lima, 15063, Peru

³Department of Biosystems Engineering, FZEA, USP, Pirassununga, 13635-900, Brazil

* Corresponding author: cmpalominob@unitru.edu.pe (C. Palomino)

DOI: 10.17268/scien.inge.2025.02.04

ABSTRACT

The continuousgrowingof the constructionindustry it is challengingto findthe rightchoice forraw materials

especially fibers for cement-based composites. In this study, raw Ichu fibers were evaluated to be used as

reinforcement of cement matrices; mercerization treatment of the original fibers followed by the shear

defibrillation technique were used to obtain the pulp; afterward, slurry-dewatering with the final pressing

process technique were usedto manufacture thecomposites boards. Resultsshow that Ichufibers requiredlow

aggressive mercerizationtreatment; furthermore, with mechanical shear defibrillationmore than 80% of the

defibrillated fiber present an aspect ratio over 80. The manufactured fiber cement composites board presenta

modulus of rupture over 8 MPa; moreover, with outdoor and indoor aging, samples modulus of rupture

increases, reaching around 13.5 MPa for the outdoor aging; furthermore, progressive embrittlement was

observedwithimpactoveragingtime.Finally,basedonthemechanicalpropertiesoftheboards,resultssuggest

that with 9%wt of the Ichu pulp fibers as reinforcement, boards shown a bests characteristic.

Keywords: Ichu fibers;fiber cement composites; naturalfibers; mechanical properties; physical properties.

1. INTRODUCTION

Since recent years fiber cement boards have been commonly used in various non-structural applications such

as internal walls, external walls, roofcoveringand cladding(Khorami, 2019). Its composition is based mainly

on a matrix of Portland cement and fibers as reinforcement, which produce a substantial increment in the

mechanical properties of the final composites, such as its flexural strength, fatigue, impact, toughness and

permeability. The mostwidely methodused fortheproductionof theseboardsis the Hatschekprocess(slurry-

dewatering), which allows the manufacture boards in different thicknesses and shapes depending on their

application. Accordingto Reichert, approximately85% ofthe fibercementproducts soldin worldwideare the

product produces by the Hatschek method (Ikai et al., 2020). Nonetheless, the methodology and composition

of fiber cement has undergone changes over time, due to the incorporation of new chemical and mineral

additives, different fiber options and matrixes with different characteristics (Bezerra et al., 2016).

Lastdecades,polypropylene(PP)andpolyvinylalcohol(PVA)fibershavebeenthemostusedasreinforcement

in the production of fibrocement; however, due to its synthetic nature, the production of this type of fiber

requires a large amount of energy, as well as chemicaland petrochemical raw materials, causingdamage to

health and the environment in the longrun (Tonoli, 2019). Because of that, great interest has been focused in

the use of lignocellulose fibers as a replacement for synthetic reinforcements. Fibers such as corn stalks,

sunflowerstalks,eucalyptus,sisal,bamboo,flax,banana,jute,bagasse,kraftandsoon(Khorami,2019,Jarabo,

2013, Fuente, 2020)were explored. Lignocellulose fiberspresentexcellent propertiessuch aslow density, low

cost and it is environmentally friendly material (Yanget al., 2019). Even though these benefits, fibers arenot

compatiblewithmineralmatrixlikecement,dueto tannin,sugar,starch,phenols,hydroxylatedcarboxylicacid

compounds present into thelignocellulosic fibers (Santoset al., 2017); becauseof that, they should be treated

prior to use as a reinforcement. The most widely method used to treat thesefibers is the mercerization(alkali

treatment), which canbe done usingNaOH solution; KOH and Ca (OH)₂can be usedas well (Azevedoet al.,

2022). With the mercerization, outer surface extractives can be removed, lignin and hemicellulos as well

Fecha de envío: 15-01-2025 Fecha de aceptación: 18-06-2025 Fecha de publicación: 30-06-2025

Palomino, C. et al.; Sciéndo ingenium, v. 21, n. 2, pp. 57 – 68, 2025.

(Santos et al., 2017); as a consequence, cellulose proportion intofiberincreasesandwiththis, theirmechanical

properties;furthermore,fibercompatibilitywiththematrixcanbeimprovedandfiberdimensionalstabilization

as well.

Literature suggestthatthefibers in the range of8 – 12% wt%, from theoverallfiber cementcomposite, arethe

optimal proportion of the reinforcements to obtain the maximum performance in the mechanical properties

(Coutts,2011).Furthermore,lignocellulosefibersaregoodenoughreinforcementtocompetewiththesynthetic

fibers, especially to reinforcemineral matrixes like cement (Shahinur and Hasan, 2020). However, its shape

(aspectratio)anditschemicalcompositionarekeyparameterstoexploititsmaximumcapacitiesincomposites.

Whenthenaturalfiberswereusedwithouttreatment,thepropertiesoffibercementcompositeswillnotexceed

3 MPa (Hasan et al., 2021); on the other hand, accordingto Savastano et al., the mechanical properties of the

fibercementcompositesusingthesisalpulpfibers,canreachover18MPainthemodulusofrupture(Savastano

et al., 2016). The pulpingprocess itself is a surface modification process, and this process can give the fibers

dimensionalstability, thus improvingthe propertiesof the final fiber cement composites and theirdurability

(Fuente et al., 2020).

Another aspect to beconsideredin theproductionof fibercement compositeis the energy spent toproduce the

cement matrices, it is known that the limestonecan replace up to 15% wt the cement matricesinto the fiber

cement composites(Gudissa, 2010, Mohammed, 2010). Ichu fibers(Stipa obtusa) or commonlycalled in Peru

as “paja brava” is a grass of the Andean area. Since ancient times, this grass had been widely used by local

people as a building material for roofs and for weaving ropes. Nevertheless, the introduction of new

construction materials has significantly diminished their usage (Mori et al., 2020). Different properties of the

Ichu fibershavebeenstudiedduringthe lastyears, thefindings ofthesestudiesindicateencouragingoutcomes

(Mori, 2020, Candiotti, 2020). An additional benefit of these materials is their accessibility and affordable

harvesting cost (approximately $0.15/kg). Research utilizing image segmentation techniques estimates a

potential annual production of over 70,000 tons of these grasses across the Andean region (Mori et al., 2020).

Since the Ichu fibers are novel materials, their treatment and their properties were explored usinga design of

experiment(DOE)methodology,showingexcellentmechanicalpropertiesassinglematerialandincomposites

(Morietal.,2020).Thesecharacteristicgivestothesefibershighpotentialtobeexploredinanotherapplication

like fiber cement composites.

The main objective of this researchis to determine the feasibility to useIchu grass fiber as a reinforcement of

cement matrices; manufactured panels wereevaluated after fullycured and after natural weathering(indoor

and outdoor); physical and mechanical properties is going to be presented and analyzed.

2. MATERIALS AND METHODS

2.1. Reinforcement

Since raw fibers show high proportion of extractives in their composition, prior to manufacture the pulp, they

were subjected to mercerization process (0.5 M, NAOH at 60°C, for 4 h); with this process, part of the lignin,

waxes and otherextractiveswere removed, Table 1 shows the true density and chemical composition for the

raw and treated fibers (Charca et al., 2015). From the bundle of treated fibers (mercerized), uniform shape

fibers whereselected in orderto measure theirmechanical properties, accordingto the ASTM C1557-14and

Candiotti recommendation(Candiottiet al., 2020); thetest was performedusingdisplacement control with1.2

mm/min and gauge lengthof 20mm. On the otherhand, remainingtreated fiberswere manually cut to lengths

between 10 - 20 mm, after that; 30 g. of fiberswerepulpby mechanical shearingtechniquein 1 L of water for

3 minutes usingblender, eachminute thespeed was changed, from 3400 rpm, thento a speedof 7600rpm and

finally, to a speed of 17500rpm (the blender usedfor this process wasOsterXpert). This blendedproductwas

drainedin a strainer, in order to eliminateas much water as possible; thenit was placedto dry in the oven at

60°C for 48 h. It is important to mention that the true density andchemical composition of the pulp fibers,

shown in the Table1, were measured immediatelyafterthe mercerizationprocess, sincethepulpingprocessis

purely mechanical, the chemical compositionandthe truedensity shouldnotchangeafter thepulpingprocess.

Once the pulpfibersare ready, certainnumberof fiberswere takingrandomlyand placedin a petriwith small

amount of water and in the top of that, transparent glass was placed; with this setup and with the microscope

(Olympus SZ), thickness and length of each fiber filament can be measured.

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Table 1. True density and chemical composition of fibers used as reinforcement according to the TAPPI standard

(Tenazoa et al., 2021)

Raw Ichu fibers

(wt%)

Treated Ichu fiber (pulp

fibers, wt%)

Density (gr/cm³)

Cellulose

1.34 ± 0.03

69.37 ± 0.79

2.63 ± 1.63

1.51 ± 0.02

90.75 ± 0.32

0.41 ±0.92

4.15 ± 0.3

Hemicellulose

Lignin

12.13 ± 0.29

10.49 ± 0.00.36

5.05 ± 0.00.41

Extractives

Ashes

3.43 ± 0.27

1.23 ± 0.23

2.2. Matrices

Cement, Sol UNACEM - Portland Type I(NTP-334.009) cement was used as main matrix, their composition

is showingin the Table 2. This typeof cementwas chosenbecauseit does notpresentmajormineral additions

in its composition.

Limestone, this material was used as a partial replacement for Portland cement (COMACSA), their

composition is showing in the Table 2.

Table 2. Cement and limestone composition (% weight, Sol UNACEM - Portland Type I and COMACSA)

CaO

-

SO₃

MgO

2.93

SiO₂

-

Al₂O₃

-

C₂S

11.9

-

C₃S

54.2

-

C₃A

10.1

-

C₄AF

9.7

-

Cement

3.00

Limestone

46 - 52

Max 1.0 0.75 - 1.5 10 - 16.5

1.9 - 3.5

2.3. Fiber cement board manufacturing

Boards were manufacturedusingthreepulp fiberweight fractions (6, 9 and 12 %wt); as a matrix, 12%wt of

limestone and the rest Type IPortland cement were used. The technique used was slurry-dewateringwith the

final pressingprocess, which can be summarize as follow; the correspondingfiber pulp was placed in a 1600

mL water container and stirring at 1000 rpm for 5 min; after this time, the cement and the corresponding

limestone were addedaccordingto the compositions. This mixturewas stirredfor10 more minutesat thesame

speed, to then be pouredinto the mold, after that a vacuum (-60 kPa) was applied for 5 minutes in order to

remove water. Afterward, manufactured board was removed from the vacuum chamber and taken to the

hydraulicpresswhere a pressureof ~ 2.8 MPa was appliedfor 5 minutes to obtain the finalthicknessof ~ 6

mm. The finalboardwasremovedfromthepressandplacedinhermeticbagsfor48hoursatroomtemperature.

Afterthat,theboardswerecuredbybeingimmersedinwaterfor26days.Oncethecuringprocesswasfinished,

thepanelswerecutintothespecimensizesforflexuraltestsandimpacttest,usingadiamonddiskcuttercooled

by water.

2.4. Natural weathering

A groupofsampleswereexposedtonaturalweatheringforaperiodof6and12months,consideringtwoaging

conditions: a) laboratory environment, the samples were placed with a 45º of slope with a light intensity of

0.001 to 10 Lux, relative humidity of 75 to 95%, with a temperatureof 16 to 22°C; b) Outdoor environment,

the samples were installedin a sample rack with an slopeof 30º oriented to the north(south hemisphere), on

the roof of theUniversidad deIngenieriay Tecnologia(latitude 12º 6 '6.98 ”, longitude77º 1' 20.91”), altitude

200 masl, ambient temperature from 11 to 27°C, relative humidity from 65 to 95%, maximum wind speed11

m/s and average 3.11 m/s, total rain precipitation of 11.2 mm during the period of aging, maximum solar

radiation of 1148.00 W/m²and 0.8 km m away from the Pacific Ocean.

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2.5. Physical properties.

Physicalpropertieslikebulkdensity(apparentdensity),waterabsorption,andapparentporosityofthesamples

were determinedaccordingto the ASTM C948 Standardtest methods. For the measurementof the thickness

swelling(TS), sampleswere completely immersedhorizontallyunder water maintainedat 25ºC for 24h; after

soaking, samples were drained on paper towels to remove excess water; thereafter, thickness at different

specific pointswere measured ineachsampleusinga micrometer, afterward, samples weredriedin an ovenat

60°C for a week; after that, the dryingtemperature in the ovenwas increased to 100°C andthe weight of the

samples was measuredperiodicallyuntil reachinga same previousmeasure;finally, thickness was measured

at the same location were measured previously.

2.6. Mechanical properties

Tests were performed usingMTS Exceed with 5 kN of load cell under displacement control (1.5 mm/min).

Three-point bend test method with 120 mm of span was used to determine, the stress at the limit of

proportionality (LOP, Eq. 1), elastic modulus (MOE, Eq. 2), modulus of rupture (MOR, Eq. 3), and the

toughness of the material (Eq. 4).

퐿

LOP = ^푃

(1)

(2)

푙표푝.

2

푏.ℎ

3

276.퐿

1296.푏.ℎ

MOE =

₃. 푚³

.퐿

MOR = ^푃

(3)

(4)

ꢀ푎푥

2

푏.ℎ

Toughness = ^{ꢁ푏푠ꢂ푟푏푒푑 푒푛푒푟푔푦}

푏.ℎ

}

Where P_lopis the load correspondingto the upper point of the linear portion of the load deflectioncurve, L is

the span length between supports, b and h are the samples width and thickness, m is the slope of the linear

portionof the load-deflection curve and P_maxis themaximum load reachduringthe test. The absorbed energy

is the area under load-deflection curve up to the point corresponding to 0.3 of MOR.

Impactstrengthwasalsomeasuredusing10mmx7mm x 100mmunnotchedsamples.Thistestwasperformed

usingGuntPendulumImpactTester25Nm;sinceimpactstrengthisconsiderablelowforthiskindofmaterial,

the minimum scalewas rescalingin order toobtaina reasonablemeasurement. For theflexural test andimpact

test, 7 samples were tested as a minimum.

3. RESULTS AND DISCUSION

3.1 Pulp fibers characteristics

Treated Ichufibers(mercerized) havea linearelastic behavior as showsFigure1, similar curveswere foundin

the previous studies (Mori, 2020, Tenazoa, 2021);however, stiffness, strength and strainto failurehave higher

valuescomparedtothereported;thesehighervaluesarerelatedtothehighercellulosecontent. Figur e 2,shows

the Weibull plot for the modulus of elasticity, strength and strain to failure for the treated fibers, shape

parametersare over 6, whichmeanthatthe results haveconsistent value; similarly, R has values over 0.92.

Treated fibers weresubjected to the mechanical shearingdefibrillation process, theresultantpulp fibers aspect

ratio was determined; Figure 3 shows the aspect ratiodistribution histogram and the Weibull plots. It is clear

that after the mechanical pulping, more than 70 % of the fibers present an aspect ratio over 80, which are

optimum to beused asreinforcement; however, around30 % of thedefibrillatedfibers can beclassified asfine

particles; dueto theshortlength, thesefiberscannot have a direct effect as a reinforcement. The average value

of the aspect ratio was 62.96 with average fiber thickness of 12.31 m.

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E = 35.55 ± 4.02 GPa

s_f= 585.77 ± 79.09 MPa

500

400

300

200

100

0

e_f= 0.00176 ± 00292 mm/mm

0.000 0.002 0.004 0.006 0.008 0.010 0.012 0.014 0.016

Strain (mm/mm)

Figure 1. Typical stress - strain curve for the treated Ichu fibers

3

Modulus of elasticity

a = 9.91, s = 37.34 GPa, R = 0.98

o

2

1

Strength

a = 8.52, s = 619.50 MPa, R = 0.92

o

0

-1

-2

-3

-4

Strain to failure

a = 6.42, s = 0.019, R = 0.92

o

3.2

3.3

3.4

3.5

Ln(E (GPa))

3.6

3.7

3.8

6.0

6.1

6.2

6.3

6.4

6.5

6.6

6.7

Ln(s_f(MPa))

-4.5

-4.4

-4.3

-4.2

-4.1

-4.0

-3.9

-3.8

Ln(e_f(mm/mm))

Figure 2. Weibull distribution plot for the modulus of elasticity, strength and strain to failure for the treated fibers

70

60

50

40

30

20

10

2

1

0

-1

-2

-3

-4

a = 1.4347

s_o= 71.42

R = 0.967

0

-5

1.5

0-20

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

20-40 40-60 60-80

80-100

100-120120-140140-160160-180

Aspect ratio (l/t)

ln(Aspect ratio)

Figure 3. Pulp fiber characteristics, a) aspect ratio histogram, b) Weibull distribution plot of aspect ratio.

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Aspect ratio plays an important rule to increase theeffectiveness to transfer the load from the matrix to the

fiber, and with this the improvementof the strengthand the toughnessof the composites. Studies developed

on bamboo, eucalyptus and pine pulps reinforcingcement matrices showssimilar average aspect ratio (51, 61

and 53 respectively) (Mori, 2020, Correia, 2018); although, it would always be better to have larger aspect

ratios to improve mechanical interlocking.

An important aspect on the natural fibers is the lignin content, since the lignin is highly susceptible to

degradation in alkaline environment. The studied Ichu fibers has considerably lower percentage of lignin (<

5%, Table 1), comparedto reportedin previousstudies(Charca, 2015, Tenazoa, 2021); thesedifferences are

commonly observed in biomass materials, since depends on the plants growing condition.

3.2 Physical properties of fiber cement composites: apparent density, water absorption, apparent

porosity and swelling

Table 3 and Table 4 show the physical properties of the fiber cement composites, considering the weight

percentageofthefiberandtheagingtimeintwoenvironmentconditions.Resultsfortheunagedsamplesshows

that, with greater amount of fiber the apparent density, water absorption, apparent porosity and swelling

increases. On the other hand, apparent density increases with aging time as well as the water absorption,

apparent porosityand thickness variation(swelling); however, after 6 months, their values maintainrelative

constant, even decreases.

Table 3. Apparent density and percentage of water absorption for samples aged in laboratory (indoor) and outdoor

environment.

Apparent density (g/cm3)

9 %wt

Water absorption (WA, %)

9 %wt

Time

(month)

6 %wt

Outdoor

1.40 ± 0.031

12 %wt

Outdoor

6 %wt

12 %wt

Outdoor

Indoor

Indoor Outdoor

1.45 ± 0.020

Indoor

Indoor Outdoor

11.9 ± 1.080

Indoor

Outdoor

Indoor

0*

6

1.49 ± 0.016

12.6 ± 0.230

13.8 ± 0.870

1.84 ± 0.05 1.91 ± 0.04 1.79 ± 0.07 1.90 ± 0.05 1.70 ± 0.08 1.78 ± 0.13 20.7 ± 0.78 18.3 ± 0.74 22.3 ± 0.95 19.2 ± 0.88 26.2 ± 2.69 24.0 ± 2.01

1.76 ± 0.04 1.83 ± 0.02 1.71 ± 0.09 1.85 ± 0.03 1.63 ± 0.09 1.69 ± 0.11 20.9 ± 0.70 18.7 ± 0.76 23.0 ± 1.38 18.7 ± 0.56 25.9 ± 2.06 24.5 ± 2.21

12

0* correspond to samples cured 48 h in a sealed bag + 27 days in water.

Table 4. Apparent porosity and percentage of thickness variation (swelling) for samples aged in laboratory (indoor) and

outdoor environment.

Apparent porosity (%)

9 %wt

Swelling (%)

9 %wt

Time

(month)

6 %wt

Indoor Outdoor

18.5 ± 1.410

12 %wt

Indoor Outdoor

20.9 ± 1.010

6 %wt

Outdoor

0.14 ± 0.012

12 %wt

Indoor Outdoor

0.51 ± 0.097

Indoor

Outdoor

Indoor

Outdoor

0*

6

19.31 ± 0.32

0.37 ± 0.016

26.8 ±

0.55

25.8 ±

27.6 ± 0.56 26.1 ± 0.60 28.6 ± 0.57

27.1 ± 0.25 25.5 ± 0.68 28.3 ± 0.89

30.7 ± 1.53 30.0 ± 0.72 1.08 ± 0.57 1.00 ± 0.20 1.03 ± 0.35 1.53 ± 0.37 0.77 ± 0.09 1.84 ± 0.33

29.6 ± 0.79 29.3 ± 0.80 1.27 ± 0.21 1.33 ± 0.09 1.60 ± 0.15 1.45 ± 0.24 1.80 ± 0.46 1.42 ± 0.25

12

0.33

0* correspond to samples cured 48 h in a sealed bag + 27 days in water.

Accordingto the results, samples with outdoor agingpresent in overall higher density for all weight ratios,

compared to the indoor aged; the incrementin the density over time was observedby Akers, 1989, as well.

Furthermore, studies developed in roofing tiles reinforced by vegetable fibers (< 6 %wt) shows that their

densityincreases after 155days exposed to naturalweatheringaging; although, their values donot exceed1.4

g/cm³(Roma et al., 2018). Tonoli 2007, attributed that the increment in the densityis relatedto the formation

of the hydration product and carbonatation of the fibers, which cause a densification of the composites.

Accelerated agingof fiber cement compositescancauseincrement in thedensityas well, contraryto thewater

absorption and apparent porosity which decreases (Tonoli, 2019); however, with natural weathering aging

water absorptionandapparentporosity increases, whichwas observedbyTonoli aswell; although, thedensity

decreases; which is contrary to the result observed in this study. Due to a carbonatation mechanism, some

metastableproduct like ettringite and calcium silicatehydrate(C-S-H) can decompose; whichin the end can

cause high water absorption and high apparent porosity (Tonoli, 2019, Taylor 1997).

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The secondaryeffects on increasingthe apparent porosity and the water absorption of the samples with aging

time, are the higher values of swelling over time as well, although the values obtained are lower than the

recommendation of ISO 8335 (<2%).

3.3 Mechanical properties

3.3.1 Stress – strain curves.

Typical stress – strain curves areshowingin Figure 4. It is evident that to higher percentageof reinforcement,

ductility increases; instead, samples with 6 %wt shows a suddenand brittle failure. On the other hand, it is

clear thedifference between agedand unagedsamples. Withaging, samplesgain stiffness and strength(Akers,

1989;Savastano,2016);however,theyloseductilitydrastically,especiallyforthe9%wtsamples.Meanwhile,

outdoor aged samples present an overall high strength compared to the samples aged indoor.

Lima is a highly denselypopulated citywith the Pacific Ocean on the west, these especialconditions makes

the city environment very aggressive, accordingto the measurement performed by SENAMHI and Lima city

administration. Alongthecity, thereare high concentrationsof carbonmonoxide(CO, 1300to 4684.3 g/m³),

hydrogensulfide (H₂S, 40.89 to 120 g/m³) and nitrogendioxide(NO₂, 45 to 210 g/m³); combinedwith sea

water particles(chloride ions) make the environmentacid; theseconditionscan reduce the surfacealkalinity

of the boards, maintainingthe fibers with minimum damage. Accordingto the study developed by Zuwonski

et al., 2018, environmentcan produceprogressivenaturalcarbonatationthrough the thickness, which improve

fiber/matrix interlockingat the interface, reducingsignificantlythe fiber pull out for the samples with 6 and

9%wt. As shows Figure1(b)samplesagedattheindoor andoutdoorenvironmentwith9%wtofreinforcement,

after the matrix failure, fibersstill takesome load, as shows the stress-strain relationbetween 0.001to 0.002

of strain.

14

a)

6 %wt

Indoor - 6 %wt (6M)

Outdoor - 6 %wt (6M)

Indoor - 6 %wt (12M)

Outdoor 6 %wt (12M)

12

10

8

6

4

2

0

0.000

0.002

0.004

0.006

0.008

Strain (mm/mm)

14

12

10

8

14

c)

b)

9 %wt

12 %wt

Indoor - 9 %wt (6M)

Outdoor - 9 %wt (6M)

Indoor - 9 %wt (12M)

Outdoor 9 %wt (12M)

Indoor - 12 %wt (6M)

Outdoor - 12 %wt (6M)

Indoor - 12 %wt (12M)

Outdoor 12 %wt (12M)

12

10

8

6

4

2

0

0.000

0

0.000

0.002

0.004

0.006

0.008

0.002

0.004

0.006

0.008

Strain (mm/mm)

Figure 4. Typical stress - strain curves for evaluated non-aged and six and twelve months (6M, 12M) aged samples, a) 6

%wt, b) 9 %wt and c) 12 %wt

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3.3.2 Limit of proportionality (LOP) and modulus of elasticity (MOE).

Improvement in the fiber/matrixinteractionmay increasethe limit of proportionality; as shows in the Figure

5, the value of LOP increases with the agingtime, there are no significant differences between the resultsfor

the indoor andoutdoor agingcondition. On the other hand, at the early stages of aging, the LOP is higher for

lower ratio of reinforcement; however, overtime, especiallyat outdoorenvironment, the LOPfor 9 %wt keep

increasing, while for the6 %wt decreases. Accordingto Tonoli et al. with aging, calcium re-precipitationinto

the fiber/matrix and fiber lumen may occur (Tonoli et al., 2019); with a subsequent petrification of thefibers;

furthermore, matrix densification can happen around the fibers/matrix interface (Bentur and Akers, 1989);

those playsa special role, avoidingthefiber pull out, andimprovingthe interlockingmechanism. On the other

hand, at the early stages, lignincansuffer degradationdue to the alkalienvironment(BenturandAkers, 1989);

which, in the end, can cause a premature failure of the fibers; however, as show

Table 1 , the lignin contentin the treated fibers is considerable low, therefore the degradationcan shift to the

hemicellulose and cellulose directly.

b)

a)

6 %wt

9 %wt

12 %wt

14

12

10

8

14

12

10

8

6

4

0

2

4

6

8

10 12

0

2

4

6

8

10 12

Time (month)

Figure 5. Variation of limit of proportionality over time a) laboratory environment (indoor), b) outdoor environment.

Higher strength at the fiber/matrix interface not only can increase the LOP, but the stiffness can also be

improved. Figure 6 shows how the modulusof elasticityincreaseswith agingtime. For the 6, 9 and 12 %wt

there are no main differences in the trend; however, after 12 months of aging, MOE reduces in their valuefor

allsamples,comparedtothe6monthsofaging;although, sampleswith9%wtandagedinoutdoorenvironment

shows better MOE. Depending of the manufacturing process and the materials quality, the stiffness of the

lignocellulosicfiber cement composites can vary from ~ 1 to ~ 27 GPa (Hasan, 2021, Tonoli, 2007); in this

study, the values obtained are in the average reported in the literature.

14

12

10

8

14

12

10

8

a)

b)

6

4

6 %wt

9 %wt

12 %wt

2

0

2

4

6

8

10 12

0

2

4

6

8

10 12

Time (month)

Figure 6. Variation of modulus of elasticity over time a) laboratory environment (indoor), b) outdoor environment.

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3.3.3 Modulus of rupture (MOR) and flexural toughness.

As observed in the Figure 7, the modulus of rupture increases with time in samples aged in outdoor

environment, keepingthe 9 %wt of reinforcement with the best behavior. On the other hand, samples aged at

the indoorenvironment don’t show changesfor the 9 and 12 wt%, although, thereis an increment for the 6

%wt. The carbonatation process is progressive, as observed by Zukowski (Zukowski et al., 2018);

contrastingly, during the flexural test, the outer layer is subjected to the maximum stress, which cause the

failure; therefore, progressive carbonatation over time may not be reflected in the MOR value.

a)

b)

14

12

10

8

14

12

10

8

6 %wt

9 %wt

12 %wt

6

0

2

4

6

8

10 12

0

2

4

6

8

10 12

Time (month)

Figure 7. Variation of modulus of rupture over time a) laboratory environment (indoor), b) outdoor environment.

Figure 8 shows theflexural toughness overtime, there arenochanges inthetoughness for sampleswith higher

content of reinforcement (12 %wt). Samples with 9 %wt shows and reduction in their toughness, although

samples exposed to outdoor environment shows higher reductions. On the other hand, trendsare quite similar

to the indoor and outdoor samples for the 6 %wt. Toughness measured in this study is considerable higher

compared to the reported to plain matrices (0.02 – 0.04 kJ/m²) (Savastano et al., 2016); although, they are

similar to the values obtained for fiber cement reinforced by sisal pulp (Santos et al., 2015).

b)

a)

6 %wt

9 %wt

12 %wt

1.0

0.8

0.6

0.4

0.2

0.0

1.0

0.8

0.6

0.4

0.2

0.0

0

2

4

6

8

10 12

0

2

4

6

8

10 12

Time (month)

Figure 8. Variation of flexural toughness over time a) laboratory environment (indoor), b) outdoor environment.

3.3.4 Specific Impact strength.

Impact strength has a particularbehavioras show Figure 9, at early stages, there is a clear differencein their

values between 6, 9 and 12 %wt; however, with the aging time, these differences are reduced. Partial

carbonatation contributedsignificantly to the toughness, since the surface and subsurface gain strengthlosing

ductility due to the progressivecarbonatationand embrittlement, the inner part still maintainstheir ductility;

therefore, this combination gives to the composite unique benefit to increase the toughness; albeit, with

complete carbonatation these benefits will be lost, as happen for 12 months of exposure.

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Palomino, C. et al.; Sciéndo ingenium, v. 21, n. 2, pp. 57 – 68, 2025.

a)

b)

3.5

3.0

2.5

2.0

1.5

1.0

3.5

3.0

2.5

2.0

1.5

1.0

6 %wt

9 %wt

12 %wt

0

2

4

6

8

10 12

0

2

4

6

8

10 12

Time (month)

Figure 9. Variation of impact strength over time a) laboratory environment (indoor), b) outdoor environment.

Accordingto the results, to produce Ichu pulprequire low aggressive mercerization treatment (0.5M NaOH),

compared to the treatment in other natural fibers (Noori, 2021, Madhu, 2019). Since the raw materials present

a relativehigh percentage of cellulose already;besides, in their natural statethe Ichufibers areporous(Charca

etal., 2015),thereforesodiumhydroxidesolutioncandiffuseeasilyintothefibersareachfastertothetechnical

fibers and produce defibrillation. On the other hand, during the process of shearingdefibrillation (pulpingby

blender), it is still requireda high amount of energy, in whichhasa room to improveandoptimizethisprocess

especially for this type of fibers.

It is also important to say that theseresultsregardingthe agingcycles were limited by the methodology used,

since theywere performed manually whenthe ideal wouldbe to havethe necessary equipment to perform the

aging cycles automatically.

In overall, compositeboardmanufacturedshows acceptable physical and mechanical properties accordingto

the Peruvianand international standards (NTPISO 8336, ASTM C1186 and NBR 5640). Unfortunately, due

to the pandemic consequence, it wasn’t possible to developthe micrography fracturestudy usingSEM, since

it is necessary to take the images immediately after the flexural andimpacttest. Opticalmicrographywas an

alternative; however, a limited and nonclear information was revealed; therefore, these results weren’t

presented in this study.

4. CONCLUSIONS

In this paper, the feasibility to use Ichu fiber as reinforcement of cement matrix was evaluated on the

applicationof anAndean grass. It can beconcludedfrom thisstudythat fiber pulpingprocesswas successfully

implementedfortheIchu raw fibers, obtainingover70 % of the fiberswith aspectratio over 80; although finer

particle (aspect ratio < 20) still represents certain percentage (~18 %).

In terms of mechanical properties, the progressive embrittlement of the samples with the aging time was

identifiedwith the stress-straincurve andthe impact strength, showinga higher impact strength for 6 months

of aging when the samples are partially carbonated (surface and sub-surface).

Ichu fiber cement composite boards were manufacturedeffectively, consideringthree weight fractions (6, 9

and12%wt),andtheagingprocesswasevaluatedconsideringtheindoor(laboratoryenvironment)andoutdoor

environment. Compositesmanufacturedwith 9 %wt show better behavior comparedto the 6 and 12 %wt in

their mechanicalbehavior, with~11.5 MPa and13.5MPa in modulus of rupturefornon-aged(curedsamples)

and aged in outdoor environment respectively; furthermore, themodulus of elasticityincreasedwith theaging

time in all the samples.

5. ACKNOWLEDGMENTS

This study was developed as part of a project funded by CONCYTEC, under contract number N° 103-2018 -

FONDECYT-BM. The authors express their gratitudeto the PeruvianGovernment for its financial support.

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