TAPIA, et al. - Study of an Environmentally Friendly High-Performance Concrete (HPC) . pp. 95-110 ISSN:1390-5007 EÍDOS 24

2024

Resumen:

Este estudio se centra en la evaluación del impacto de

la adición de diferentes porcentajes de nanosílice (NS)

(0.75 %, 1.5 % y 3 % - y microsílice (MS) – 5 %, 10 %

y 15 %), como sustitutos parciales del cemento en la

formulación de concreto de alto desempeño (HPC). Se

realizaron evaluaciones mecánicas, incluidas medicio-

nes de compresión, tensión, resistencia a la exión,

módulo dinámico, índice de Poisson y elasticidad, en

intervalos de 3, 7, 28, 56 y 91 días, para comprender el

impacto en las características estructurales del HPC.

Además, se llevaron a cabo microscopía electrónica

de barrido (SEM), microscopía electrónica de transmi-

sión (TEM) y espectroscopia de rayos X de dispersión

de energía (EDS), para examinar los cambios en la

microestructura. Los resultados indican que la incor-

poración de un 15 % de microsílice en la mezcla de

hormigón, produce una mejora más pronunciada en

las propiedades mecánicas, en comparación con la

adición de sólo un 3 % de nanosílice, superando inclu-

so la combinación de un 15 % de microsílice y un 3 %

de nanosílice. Este enfoque de sustitución mejora la

sostenibilidad al reducir el uso de cemento.

Palabras claves: Cementos ecológicos, materiales

HPC, microsílice, nano-sílice, propiedades físico-me-

cánicas, sostenibilidad.

Jhon Fabricio Tapia Vargas,

2,3,4

Mohammadfarid Alvansazyazdi,

Alexis Andrés Barrionuevo Castañeda

Maestría en Construcciones de Obras Civiles Mención Gestión y Dirección, Facultad de Ingeniería y Ciencias

Aplicadas, Universidad Central del Ecuador, Av. Universitaria. ing.jftapiav@outlook.es.

ORCID: 0000-0002-6089-040X

Institute of Science and Concrete Technology, ICITECH, Universitat Politècnica de València,Spain.

Carrera de Ingeniería Civil, Universidad Central del Ecuador, Av. Universitaria, Quito 170521, Ecuador.

Facultad Ingeniería, Industria y Construcción, Carrera Ingeniería Civil, Universidad Laica Eloy Alfaro de Manabi,

Manta, Ecuador. faridalvan@uce.edu.ec. ORCID: 0000-0001-8797-5705

Gobierno Autónomo Descentralizado Municipal del Cantón Pastaza. alexis_3214@hotmail.com.

ORCID: 0009-0000-7634-5513

Study of an Environmentally Friendly High-Performance

Concrete (HPC) Manufactured with the Incorporation

of a Blend of Micro-Nano Silica

Estudio de un hormigón de alto rendimiento (HPC),

respetuoso con el medio ambiente, fabricado

con la incorporación de una mezcla de micronano sílice

EÍDOS N

Revista Cientíca de Arquitectura y Urbanismo

ISSN: 1390-5007

revistas.ute.edu.ec/index.php/eidos

Abstract:

This study focuses on the evaluation of the impact of

the addition of different percentages of nanosilica (NS)

(0.75 %, 1.5 % and 3 % - and microsilica (MS) – 5 %,

10 % and 15 %), as partial cement substitutes in the

formulation of high performance concrete (HPC).

Mechanical assessments, including compression,

tension, exural strength, dynamic modulus, Poisson's

ratio, and elasticity measurements, were performed at

intervals of 3, 7, 28, 56, and 91 days to understand

the impact on HPC's structural characteristics.

Additionally, scanning electron microscopy (SEM),

transmission electron microscopy (TEM), and energy-

dispersive X-Ray spectroscopy (EDS) were carried out

to examine changes in microstructure. Results indicate

that incorporating 15 % microsilica in the concrete mix

yields a more pronounced improvement in mechanical

properties compared to adding only 3 % nano-silica,

surpassing even the combination of 15 % microsilica

and 3 % nano-silica. This substitution approach

enhances sustainability by reducing cement usage.

Keywords: Cementitious Environmentally Friendly,

HPC Materials, Microsilica, Nano-silica, Physical-

mechanical properties, sustainability.

Recepción: 17, 03, 2024 - Aceptación: 01, 05, 2024 - Publicado: 01, 07, 2024

TAPIA, et al. - Study of an Environmentally Friendly High-Performance Concrete (HPC) . pp. 95-110 ISSN:1390-5007

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1. INTRODUCTION

The economic development and evolution

of countries are closely engaged with the

construction industry and the creation of

new materials. Improving the durability of

cement has been instrumental in prolonging

the service life of concrete structures [1-5].

The introduction of nanotechnology into the

construction sector, particularly through the

use of nano-silica (NS), has been shown to

signicantly improve the mechanical prop-

erties and durability of cement-based prod-

ucts due to its high purity and specic sur-

face area, which affect the hydration and

microstructure of cement [6, 7].

Building upon this foundation, the inte-

gration of various nanomaterials beyond

nano-silica, such as nano-alumina, carbon

nanotubes, and others, continues to push

the boundaries of concrete’s capabilities

[8, 9]. These materials contribute to a sig-

nicant enhancement in the compressive,

tensile, and exural strengths of concrete

by optimizing the particle packing and

reducing the porosity of the cementitious

matrix, leading to denser and more robust

concrete structures [10-12]. This evolution

in concrete technology not only supports

structural integrity but also extends the

lifespan of infrastructure, marking a pivotal

shift towards more sustainable construc-

tion practices [13].

Moreover, the addition of nanomaterials

has been found to improve the workability

and reduce the water absorption of con-

crete, factors that are crucial for the prac-

tical application and longevity of concrete

structures in various environmental con-

ditions [14]. Enhanced workability facili-

tates easier mixing and application, while

reduced water absorption minimizes the

risk of damage from freeze-thaw cycles

and chemical attack, thereby preserving

the structural health and integrity over time

[15, 16].

In this regard, it is necessary to design

high-performance concretes (HPC) with

nanomaterials incorporated into the con-

crete matrix, aiming to achieve good work-

ability, durability, and superior strength

properties compared to conventional con-

crete. This can be accomplished by em-

ploying existing calculation methods and

available materials [7, 17-20].

Nowadays, HPC plays a crucial role in the

construction of specialized structures due

to the enhancements it offers over conven-

tional concrete. HPC enables the construc-

tion of increasingly slender structures by

reducing the cross-sections of structural

elements, thereby providing more avail-

able space within buildings [21, 22].

Moreover, the development of Environmen-

tally Friendly High-Performance Concrete

(HPC) incorporating a blend of micro-nano

silica represents a signicant stride to-

wards sustainable construction practices.

This innovative approach not only aims to

enhance the mechanical and durability

properties of concrete but also focuses on

reducing the environmental impact associ-

ated with traditional concrete production

methods. By integrating micro and nano

silica, the concrete matrix can be signi-

cantly improved, leading to a reduction in

the carbon footprint of construction mate-

rials and promoting eco-friendly building

solutions [23, 24].

Lastly, the environmental sustainability of

concrete is signicantly enhanced through

the use of nanomaterials. By improving

the material's mechanical properties and

durability, the lifecycle of concrete struc-

tures is extended, reducing the overall en-

vironmental impact associated with their

construction and maintenance [25]. Fur-

thermore, an example of sustainable prac-

tices in the construction industry, although

not analyzed in this study, is the use of

nanomaterials such as y ash contributes

to sustainable development practices by

recycling industrial waste, further dimin-

ishing the construction industry's carbon

footprint[26].

The importance of this study extends be-

yond the technical advancements in con-

TAPIA, et al. - Study of an Environmentally Friendly High-Performance Concrete (HPC) . pp. 95-110 ISSN:1390-5007 EÍDOS 24

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crete properties. The research aims to

provide a comprehensive understanding

of how the combined effects of micro and

nano silica can optimize HPC's perfor-

mance, offering a viable solution that aligns

with global sustainability goals. By explor-

ing alternative micro and nano silica dos-

age and methods that reduce the reliance

on conventional cementitious materials, this

research contributes to the development of

more sustainable urban environments.

2. EXPERIMENTAL PROCEDURE

2.1. Materials Used

For the analysis in this research, aggre-

gates from the Pifo quarry, located in the

province of Pichincha in Ecuador, were uti-

lized. Holcim type Gu cement [27] and a

superplasticizer 7955 from Basf [28] were

also employed.

For this research, MasterlLife SF 100 mi-

crosilica is used from the company Basf

and distributed by Imperquik, whose tech-

nical specication recommends the use of

microsilica in percentages of between 5%

and 15% as an addition to the cement [28].

Nanosilica is made up of dozens of nano-

meter-sized amorphous particles com-

posed of silica dioxide (SiO2), which is the

interaction of silicon with oxygen that is

commonly called silica. This nano compo-

nent has pozzolanic properties that, when

reacting with the cement, improve its me-

chanical properties.

Among all the characteristics, the coarse

aggregate has a maximum size of ½", a

specic gravity of 2.47 g/cm3, and an ab-

sorption capacity sof 4.92%. The ne ag-

gregate is a crushed natural quarry sand

with a specic gravity of 2.57 g/cm3, an

absorption capacity of 3.1%, and a ne-

ness modulus of 2.96. All the parameters

for both the coarse and ne aggregates

comply with the requirements specied in

the ASTM [29].

2.2 Mixing and Testing Procedure

The concrete mixture process was me-

ticulously followed to ensure optimal con-

sistency and strength of the nal product.

First, we dampened the interior of the con-

crete mixer to prevent any dry materials

from sticking and to facilitate an even mix.

Then, we added both the coarse and ne

aggregates into the mixer, allowing them to

blend for a full minute to achieve a uniform

distribution.

Following the initial mixing, we introduced

the specied amount of cement to the ag-

gregate mixture, continuing the blending

process for an additional 30 seconds to

ensure the cement was thoroughly inte-

grated with the aggregates. After the ce-

ment had been mixed in, we added water

that had been pre-mixed with nano-silica

to the mixer. This combination was then

mixed for approximately two minutes, al-

lowing the nano-silica to disperse evenly

throughout the mixture, which enhances

the concrete's mechanical properties and

durability.

Finally, we incorporated the additive into

the mixture. This step was done carefully

to allow sufcient time for the additive to

react properly with the other components,

ensuring proper particle adherence and

achieving the desired chemical and physi-

cal properties in the nished concrete. This

methodical approach to mixing ensures

that the concrete possesses the neces-

sary workability, strength, and longevity

required for our construction needs. The

mixture proportion is provided in Table.

To enhance the properties of nano-silica in

the concrete, a mechanical mixer is used

to achieve a homogeneous mixture of

nano-silica and water, producing a slurry

that guarantees improved properties in the

concrete fabrication process.

Once the mixture was ready, a portion of

it was used to measure the slump ow ac-

cording to the standard ASTM C-161 [30] s,

and the remaining mixture was poured into

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100 mm molds for compression and tensile

studies. The specimens fabricated were

left to cure in the curing chamber for the

assigned ages of 3, 7, 28, 56, and 91 days

for their respective tests.

3.LABORARY TEST, RESULTS AND

DISCUSSION

3.1. Slump Flow Test

According to the data presented in Table

1, for a water-to-cement ratio (w/c) of 0.3

and varying percentages of added micro-

silica and nano-silica particles to the high-

performance concrete (HPC), an increase

in their content leads to a reduction in the

ow diameter of the mixture compared to

the control mix. This observation can be at-

tributed to the specic surface area of the

microsilica and nano-silica particles, which

causes cohesion forces between both mi-

cro and nanoparticles, resulting in the for-

mation of silica agglomerates. As a result,

these agglomerates exhibit high adsorp-

tion and signicant water retention capac-

ity due to their high specic surface area

and porosity at the micro and nanoscale.

The specic surface areas of microsilica

and nano-silica particles signicantly im-

pact their cohesion forces, leading to the

formation of silica agglomerates. This phe-

nomenon is attributed to factors such as

the surface energy of the particles and

their interaction with surrounding condi-

tions. Studies have shown that higher sur-

face energy in substances like amorphous

silica spheres enhances adhesion forces

between particles, facilitating their ag-

gregation (Kamel, 2016). Additionally, the

presence of hydrophobic silica nanopar-

ticles can induce anti-adhesive forces at

interfaces, altering the adhesive properties

and promoting the formation of aggregates

[32]. Furthermore, the dynamic adhesion

behavior of silica particles is highly depen-

dent on surface and electrostatic heteroge-

neity, inuencing how particles adhere and

aggregate under different conditions [33].

The formation of a dense agglomeration of

solid particles in the mixture containing mi-

crosilica and nano-silica is another reason

for the substantial increase in owability

and viscosity of the cementitious materials.

To address this, higher dosages of water-

reducing superplasticizer are recommend-

ed to maintain workability and inhibit ow

reduction in high-performance concrete

(HPC) due to the increased percentage

of cement substitution and the increased

specic surface area of microsilica and

nano-silica particles.

Table 1. Proportion of HPC mixes (Kg/m³)

Mix code Type w/b Cement Water

Micro-

SiO2

Nano-

SiO2

Gravel Sand SP

Slump ow

diameter (cm)

C - 0,30 550 165 - - 944,53 652,63 6.6 59

5% MS

SF100

522.5 165 27.5 - 940.4 649.8 7.15 51

10% MS

SF100

495 165 55 - 946.9 646.9 7.7 53

15% MS

SF100

467.5 165 82.5 - 932 644 8.8 56

0,75% NS NS200 545.875 165 - 4.125 943.6 652 11 52.5

1,5% NS NS200 541.75 165 - 8.25 942.7 651.4 14.3 55

3% NS NS200 533.5 165 - 16.5 940.9 650.1 17.05 56

15% MS+

1,5% NS

ML+NS 459.25 165 82.5 8.25 930.2 642.7 23.1 54

15% MS +

3% NS

ML+NS 451 165 82.5 16.5 928.4 641.5 25.85 51

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3.2. Mechanical Properties

3.2.1. Compressive Strength

The results of the mechanical tests for

compressive strength and indirect tensile

strength are shown in Table 2 and Table 3,

respectively.

The incorporation of nanosilica into con-

crete has been specically studied for

its impact on compression resistance.

Nanosilica acts as a partial replacement

for cement, contributing to the improve-

ment of the concrete's mechanical prop-

erties due to its pozzolanic reaction and

microstructural renement. For instance,

Ganesh et al. [34, 35] and Ardalan et al.

[35] observed that the addition of nano-

silica improves the compressive strength

of concrete by enhancing the hydration

process and rening the microstructure

of the cementitious matrix. Additionally,

Zanon et al. [36] and Lim & Mondal [37]

reported that the combined use of nano-

silica with other admixtures, like silica

fume, can further increase compressive

strength, reduce capillary absorption, and

minimize chloride penetration, primarily

attributed to the synergetic effect of nano-

silica in the cementitious composite. This

demonstrates that nanosilica contributes

positively to the compression resistance

of concrete, making it a valuable compo-

nent for enhancing the structural proper-

ties of concrete mixtures.

Based on the results obtained with the in-

corporation of microsilica and pyrogenic

nano-silica in the mixture, the mechanical

strengths have improved as the curing

ages increase for both the mixtures with

the incorporation of micro and nanoparti-

cles compared to the control concrete.

There is a positive effect for nano-silica, as

its incorporation into the matrix of cement-

based materials like concrete is attributed

to a 4-fold increase in performance. Both

microsilica and nano-silica demonstrate

high pozzolanic activity and control unfa-

vorable crystallization due to a large num-

ber of micro and nanoparticles among

hydration products, along with their con-

nement role.

Table 2. Compressive strength test result (MPa)

Mix code

Curing Age

3 Days 7 Days 28 Days 56 Days 91 Days

C 31.42 43.92 58.65 64.74 69.71

5% MS 31.99 43.86 62.06 70.76 76.39

10% MS 30.17 42.98 62.06 71.53 78.19

15% MS 25.11 41.90 74.62 79.90 81.85

0,75% NS 24.36 41.47 57.55 64.66 70.23

1,5% NS 27.39 38.59 57.71 65.34 71.37

3% NS 27.53 39.61 57.52 65.52 73.27

15% MS+ 1,5%NS 17.33 36.57 61.85 72.77 78.51

15% MS + 3% NS 22.42 42.37 64.21 74.98 80.24

Table 3. Indirect tensile strength test result (MPa)

Mix code

Curing Age

3 Days 7 Days 28 Days 56 Days

C 2.22 3.63 4.29 4.59

15%MS 2.24 3.62 4.78 5.89

3%NS 2.22 3.45 4.75 5.83

15%MS + 3%NS 1.93 3.39 4.79 5.87

100

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Nanosilica, when incorporated into the

matrix of cement-based materials such as

concrete, has been shown to have a signi-

cantly positive effect on their performance.

This study has shown that the addition of

nanosilica results in an increase of up to

4 times the strength and durability of con-

crete. Both microsilica and nanosilica ex-

hibit high pozzolanic activity, allowing them

to control unfavorable crystallization in the

concrete matrix.

Research by Qing, Zhang, Li, and Chen

[38] demonstrates that nano-SiO2 exhib-

its notably higher pozzolanic activity com-

pared to silica fume, contributing to im-

proved compressive and bending strength

in concrete, especially at early ages. Fur-

thermore, Hassan [39] explores the inef-

ciency of traditional testing methods for

nano-silica in concrete, proposing a modi-

ed approach due to nano-silica's unique

properties such as its high surface area

and pozzolanic reactivity.

Micro and nano particles incorporated in

concrete help control micro and nanoscale

porosity within its microstructure, speci-

cally in the transition zone between aggre-

gates and cement paste, thus contributing

to increased strength. For a water-to-bind-

er ratio (w/b) of 0.30, higher values were

obtained using 15% microsilica and 3%

nano-silica, as compared to other percent-

age additions. This is attributed to the parti-

cles' ability to act as ller agents, reducing

the formation of micro pores and enhanc-

ing the material's density [40, 41].

According to Table 2, the compressive

strength is greater for microsilica, nano-sil-

ica, and their combination across various

curing periods. The highest values were

achieved for 15% MS, 3% NS, and 15% MS

+ 3% NS. This resulted in an increase of

17%, 5%, and 15% respectively at 91 days,

thereby obtaining higher strengths than the

control mix. The compressive strength of

High-Performance Concrete (HPC) incor-

porating microsilica, nano-silica, and the

combination of both was higher than the

control mix. At early ages, slightly lower

strengths were obtained for the values of

15% MS, 3% NS, and 15% MS + 3% NS.

However, these differences may be attrib-

uted to the increased pozzolanic activity.

While there is no standardized method for

enhancing the dispersion of micro- and

nanoparticles of silica, employing expen-

sive techniques like ultrasonic mixing has

resulted in better distribution of nanopar-

ticles throughout the microstructure.

Figure 1. Compression Strength of Microsilica

Figure 1 presents the results of the com-

pression tests for the control specimen com-

pared to specimens containing microsilica

at concentrations of 5%, 10%, and 15%.

The inuence of microsilica is evident, as

the trend curve lines for all concrete sam-

ples with added microsilica surpass that of

the control specimen in terms of compres-

sion behavior. Notably, specimens with a

15% microsilica content exhibited superior

compressive strength compared to those

with 5% and 10%, which displayed nearly

identical levels of compression resistance.

It was observed that all specimens demon-

strated comparable resistance at the age

of 7 days; however, beyond this period, the

compressive strength of the specimens

containing 15% microsilica increased sig-

nicantly. This trend was particularly no-

ticeable at 28 days. By day 96, the differ-

ences in compressive resistance among

various microsilica dosages became mini-

mal, suggesting that the variations in mi-

crosilica content (5%, 10%, and 15% in

this study) primarily affect early-age com-

pressive strength rather than long-term

strength. Nevertheless, additional experi-

mental studies are required to verify these

ndings conclusively.

101

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Regarding concrete samples that just in-

corporated nanosilica, no signicant dif-

ferences were observed in compression

behavior, contrasting with results from

concrete samples containing microsilica.

Figure 2 illustrates the compression test

outcomes for concrete specimens incorpo-

rating varying concentrations of nanosilica

in their mix designs, specically 0.75%,

1.5%, and 3%. These ndings suggest

that, unlike microsilica, the inclusion of

nanosilica at these specic percentages

does not notable affect the compressive

strength behavior of the concrete.

To better understand the differential im-

pacts of microsilica and nanosilica on

compressive strength, Figure 3 displays

the comparative resistance trends be-

tween concretes incorporating the highest

percentages used in this study: 15% mi-

crosilica and 3% nanosilica, respectively.

It is evident that microsilica exerts a sig-

nicant inuence on compressive strength

when compared with both the nanosili-

ca-enhanced concrete and the control

specimen. This effect is pronounced both

in the early age (28 days) and at a more

advanced age (96 days). Specically, a

notable increase of 22.8% in compressive

resistance at 28 days was observed for the

concrete containing microsilica.

3.2.2. Indirect tensile strength (Brazilian

test)

The utilization of nanosilica and microsilica

in concrete compositions has been exten-

sively studied, revealing signicant en-

hancements in the mechanical properties

relevant to the Brazilian test for concrete.

These admixtures are found to notably

improve the splitting tensile strength and

exural strength of concrete. This improve-

ment, however, can coincide with reduc-

tions in compressive strength and modulus

of elasticity, illustrating the need for careful

balance in composite formulations. The en-

hancements attributable to nanosilica and

microsilica are particularly pronounced

when used in tandem, suggesting a syn-

ergistic interaction that bolsters the con-

crete’s mechanical integrity [42-44].

Moreover, the inclusion of nanosilica has

been linked to considerable improvements

in the compressive and tensile strengths of

concrete, specically when optimal dosag-

es are employed. This nding is critical for

early-age concrete curing, where strength

development is crucial for subsequent con-

struction phases and long-term durability

[34, 45]. The combined use of nanosilica

and microsilica not only contributes to su-

perior hardened properties but also aligns

with sustainable construction practices by

potentially lowering the cement content

required for achieving desired strength

levels. This dual benet underscores the

importance of integrating these materials

into modern concrete mixes for enhanced

performance and sustainability [46, 47].

The results from the indirect Brazilian ten-

sile strength tests (Fig. 4) indicate a sig-

nicant enhancement in tensile strength

with the incorporation of microsilica, nano-

silica, and their combination. At 56 days,

an increase of 28% in tensile strength was

Figure 2. Compression Strength of Nano-silica Figure 3. Compression Strength of Micro and Nano-silica

102

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noted for mixtures with a 15% microsilica

substitution as well as for those with a com-

bined substitution of 15% microsilica and

3% nanosilica. In both instances, the per-

formance improvement was substantial,

with only a marginal difference of one per-

centage point compared to mixtures that

contained solely 3% nanosilica.

Figure 4. Tensile Strength of Micro-Nano-silica and Hybrid

3.2.3. Flexure test

The integration of nanosilica and micro-

silica into concrete formulations has shown

signicant improvements in the exural

behavior and bond strength of reinforced

concrete. Research indicates that the ad-

dition of nanosilica enhances the bond be-

tween concrete and reinforcement bars,

leading to increased load-carrying capac-

ity, reduced crack widths, and improved

ductility. These improvements suggest that

nanosilica may serve as an effective poz-

zolanic admixture for enhancing structural

properties in concrete applications [48].

Furthermore, experimental results have

demonstrated the superior performance

of nanosilica-added high-performance

concrete over traditional and microsilica-

added concretes, particularly in terms of

the concrete-rebar interface and exural

strength [49].

In addition to the enhanced bond strength,

nanosilica has also been found to signi-

cantly improve the mechanical and trans-

port properties of lightweight aggregate

concrete. Even small dosages of nanosili-

ca result in considerable strength improve-

ments and a reduction in transport prop-

erties. This is attributed to the compaction

of the concrete matrix and modication of

the air-void system, which leads to a more

rened pore structure and improved over-

all mechanical performance [50]. The ad-

dition of nanosilica not only contributes to

higher exural and compressive strengths

but also enhances the durability of light-

weight concrete structures [51].

Explain the test approach. Samples and

etc. or photo.

Regarding exural strength, the mixtures

show relatively low increase values, with

the highest being 7% observed for the mix-

ture with 15% Micro silica substitution, and

the lowest value of 3% for the mixture with

3% Nano silica substitution. Considering

the Mixed Mixture with 15% Micro silica

+ 3% Nano silica substitution, the ex-

ural strength is not statistically signicant,

with only a one-percentage-point increase

compared to the nano silica mixture.

Figure 5. Flexural strength by percentage of cementitious

additions at 56 day.

3.2.4. Tests for modulus of elasticity and

Poisson's ratio

The modulus of elasticity (MOE) is a critical

parameter for both ultra-high performance

concrete (UHPC) and conventional con-

crete as it directly inuences the structural

behavior and serviceability of constructed

facilities. For UHPC, the MOE is signi-

cantly impacted by the composition and

characteristics of the materials used. Re-

cent studies have proposed new equations

for predicting the MOE at different ages

based on the specic mixtures and local

materials used, which can lead to a bet-

ter understanding of the structural behav-

ior of UHPC and its applications in design

[12, 20, 52, 53].

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In contrast, conventional concrete exhib-

its a wider range of MOE due to variations

in mix design, aggregate type, and other

factors. Extensive research has been con-

ducted to evaluate the MOE of conven-

tional concrete under different conditions,

highlighting the effects of water/cement

ratio, aggregate size, and type, as well as

the inclusion of y ash [54, 55]. These stud-

ies have led to the development of predic-

tive models that provide a reliable estima-

tion of the MOE based on the compressive

strength and other easily measurable prop-

erties of concrete [56, 57].

The modulus of elasticity obtained for the

different tested cementitious additions

at 28 days shows an increase in its value

compared to the control mixture. The mix-

tures with 15% microsilica and the mixed

mixture with 3% nano silica and 15% mi-

crosilica are particularly representative in

this regard.

Figure 6. Modulus of Elasticity by percentage of

cementitious additions at 28 days

3.2.5. X-ray Diffraction Analysis (XRD)

X-ray Diffraction Analysis (XRD) is a power-

ful non-destructive testing technique used

to analyze the phase composition and

crystalline structure of materials, including

concrete. In the context of concrete tests,

XRD is used to identify the types of cement

hydrates and other crystalline substances

formed during the hydration process of ce-

ment and to assess the presence of poten-

tially harmful compounds like alkali-silica

reaction (ASR) products or ettringite [58].

Figure 7 displays the diffractogram ob-

tained from X-ray testing for dosages of

0.75% at ages of 3, 7, and 28 days. The

peaks observed in the graph allow us to

estimate the different compounds present

in the analyzed sample.

Figure 7. X-ray Diffraction (XRD) of 0.75% nano-silica at 3,

7, and 28 days

Figure 8 displays the diffractogram ob-

tained from X-ray testing for dosages of

1.5% nano-silica at 3, 7, and 28 days. The

peaks observed in the graph allow us to

estimate the different compounds present

in the analyzed sample.

Figure 8. X-ray Diffraction (XRD) of 1.5% nano-silica at 3,

7, and 28 days

Figure 9 displays the diffractogram ob-

tained from X-ray testing for dosages of 3%

nano-silica at 3, 7, and 28 days. The peaks

observed in the graph allow us to estimate

the different compounds present in the an-

alyzed sample.

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Figure 9. X-ray Diffraction (XRD) of 3% nano-silica at 3, 7,

and 28 days

Figure 10 displays the diffractogram ob-

tained from X-ray testing for dosages of

1.5% NS + 15% MS at 3, 7, and 28 days.

The peaks observed in the graph allow us

to estimate the different compounds pres-

ent in the analyzed sample.

Figure 10. X-ray Diffraction (XRD) of 1.5% NS-15% MS at

3, 7, and 28 days

Figure 11 displays the diffractogram ob-

tained from X-ray testing for dosages of

3% NS + 15% MS at 3, 7, and 28 days. The

peaks observed in the graph allow us to

estimate the different compounds present

in the analyzed sample.

Scrivener, K., et al. [58] research has dem-

onstrated similar trends, revealing signi-

cant alterations in the microstructure cor-

responding to various nano-silica dosages,

paralleling the ndings from this study at

nano-silica concentrations of 0.75%, 1.5%,

and 3% across different timeframes. The

comparative examination underscores a

uniform trend of enhanced pozzolanic re-

actions and concrete matrix densication

with increased nano-silica levels, aligning

with the outcomes observed in this work.

Additionally, the ndings from the com-

bined application of 1.5% nano-silica and

15% micro-silica in this research Scrivener,

K., et al. observations, shedding light on

the combined effects of these additives,

corroborating with his results on optimized

mix designs for reactive powder concrete.

Figure 11. X-ray Diffraction (XRD) of 3% NS-15% MS at 3,

7, and 28 days

3.2.6. SEM and EDS Analysis

Scanning Electron Microscopy (SEM) and

Energy-Dispersive X-ray Spectroscopy

(EDS, also known as EDX or EDXS) are

complementary techniques used in mate-

rials science, biology, and various other

elds to analyze the surface topography,

composition, and properties of materials.

Figure 12 presents the specimens with a

1.5% nano-silica substitution for the ce-

mentitious material, indicating the percent-

ages of each element present in the sample.

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Tvhe elements constituting the con-

crete sample with 3% nano-silica

substitution for the cementitious ma-

terial are presented, and the percent-

ages of each element present in the

sample can be seen in the table.

Figure 12. SEM Micrograph a) Micrograph of 1.5% nano-silica at 3

days b) Micrograph of 1.5% nano-silica at 28 days

Figure 14. SEM Micrograph a) Micrograph of 3% nano-silica at 3 days

b) Micrograph of 3% nano-silica at 28 days.

Figure 13. EDS Analysis for a nano-silica mixture with 1.5% content

Figure 15. EDS Analysis for a nano-silica mixture with 3% content

The elements constituting the con-

crete sample with a mixed incorpora-

tion of 1.5% NS + 15% MS as a sub-

stitution for the cementitious material

are presented, and the percentages

of each element present in the sam-

ple can be seen in the table.

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Figure 16. SEM Micrograph a) Micrograph of nano-silica and

microsilica with a percentage of (1.5 % + 15%) at 3 days

b) Micrograph of nano-silica and microsilica with a percentage of

(1.5 % + 15 %) at 28 days.

Figure 18. SEM Micrograph, a) Micrograph of the mixed mixture of

3 % nano-silica and 15 % microsilica at 3 days, b) Micrograph of the

mixed mixture of 3 % nano-silica and 15 % microsilica at 28 days

Figure 17. EDS Analysis for a mixture of 1.5% nano-silica and 15%

microsilica

Figure 19. EDS Analysis for a mixture of 3 % nano-silica and 15 %

microsilica

The elements constituting the con-

crete sample with a mixed incorpora-

tion of 3% NS + 15% MS as a sub-

stitution for the cementitious material

are presented, and the percentages

of each element present in the sam-

ple can be observed in the table.

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4. SUMMARY AND CONCLUSIONS

In this study, an experimental design was

carried out that incorporated different per-

centages of microsilica and nanosilica. The

ndings revealed that the substitution of

15% microsilica resulted in a notable 28%

increase in compressive strength at 28 days,

and a 17% increase at 91 days, in contrast

to the control mixture. On the other hand, the

inclusion of 3% nanosilica showed a minor

impact, improving compressive strength by

only 5% at 91 days. These results led to the

identication of an optimal formulation that

combines 15% microsilica and 3% nano-

silica, giving the concrete greater strength

compared to the control mixture. This nd-

ing highlights the importance of the specic

combination of microsilica and nanosilica

in improving the mechanical properties of

concrete, which has signicant implications

in the construction industry and opens new

possibilities for the development of high-

performance materials.

The inclusion of nanoparticles as partial

substitutes for cement has been shown

to signicantly improve the mechanical

properties of concrete, highlighting a no-

table increase in compressive and tensile

strength. These results were achieved

without signicantly affecting the exural

strength, elastic modulus or Poisson's ra-

tio compared to the base mix. Addition-

ally, this modication has been shown to

improve concrete workability by mitigating

aggregate segregation and ensuring ad-

equate concrete slump. These ndings not

only highlight the potential of nanoparticles

in improving concrete properties, but also

suggest a promising approach for the de-

velopment of high-performance construc-

tion materials with practical applications in

the construction industry.

In summary, the incorporation of microsilica

in high-performance concrete not only im-

proves its mechanical properties and work-

ability, but also contributes signicantly to

meeting sustainability requirements. By re-

ducing the amount of cement needed, the

use of microsilica decreases the environ-

mental impact associated with cement pro-

duction, including reducing carbon dioxide

emissions. This positions microsilica as a

viable and environmentally friendly alterna-

tive in the construction industry, in line with

global sustainability objectives and current

environmental regulations.

5. RECOMMENDATIONS

It is necessary to perform a larger number

of test specimens as the results presented

in this study are indicative rather than rep-

resentative of concretes in order to obtain

a statistical analysis.

It is proposed to perform various tests on

specimens with different additions of nano-

silica ranging from 1.5% to 3% of nano-

silica, as well as micro-silica in the range

of 10% to 15%. The objective is to nd

an optimal addition to achieve maximum

strength.

It is advisable to conduct tests in the fresh

state of the cementitious material with ad-

ditions of nano-silica and micro-silica in or-

der to determine normal consistency and

setting times. This is because the reaction

between these additives produces an exo-

thermic reaction, leading to an increase in

hydration heat.

DECLARATION OF COMPETING

INTEREST

The authors hereby state that they have

no known nancial interests or personal

relationships that may have inuenced the

work reported in this paper.

ACKNOWLEDGEMENTS

We would like to express our gratitude to

Dr. Alexis Debut from the Center for Na-

noscience and Nanotechnology, Armed

Forces University ESPE, for his support,

as well as to the laboratory staff. We would

also like to thank the personnel of INECYC

and the material testing laboratory at the

Central University of Ecuador.

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