Revista Científica de Ingeniería, Industria y Arquitectura

Vol.9, Num.18 (jul-dec 2026) ISSN: 2737-6451

Suggested citation: Alvansazyazdi, M.; Quimbia Tasgacho, D., Padilla

Folleco, W., & Zambrano-Roldán, K. (2026). Determination of the Optimal

Clay Nanoparticle Content in Mortars to Improve Compressive Strength

Compared to Conventional Mortar for Plastering. Revista Científica FINIBUS

– Ingeniería, Industria y Arquitectura. 9(18) 115-134

https://doi.org/10.56124/finibus.v9i18.010

Received: 25-06-2024 Review: 05-10-2024

Accepted: 15-12-2024 Published: 24-01-2025

DOI: https://doi.org/10.56124/finibus.v9i18.010

Received: 15-09-2025 Review: 05-01-2026

Accepted: 02-02-2026 Published: 01-07-2026

Article

Determination of the Optimal Clay Nanoparticle

Content in Mortars to Improve Compressive Strength

Compared to Conventional Mortar for Plastering

Mohammadfarid Alvansazyazdi [1]

Diego Quimbia Tasgacho [1]

Wilman Padilla Folleco [1]

Karen Zambrano-Roldán[2]

[1] Faculty of Engineering and Applied Sciences, School of Civil Engineering, Central University of Ecuador. Quito, Ecuador.

[2] Faculty of Engineering, Industrial and Architecture, School of Civil Engineering, Laica Eloy Alfaro de Manabí University, Manta,

Ecuador.

Corresponding author: farid.alvan@uce.edu.ec

Abstract

This study focuses on enhancing the mechanical properties of plaster mortars through the incorporation of clay nanoparticles. The main

objective was to determine the optimal dosage of clay nanoparticles by evaluating their effect on compressive strength, water absorption, and

permeability, supported by nanometric-scale microstructural analysis. Mortars were prepared using Holcim type N cement and Selvalegre

type HS cement, local washed quarry sand, and potable water. Clay nanoparticles were added at 0.25%, 0.50%, 0.75%, and 1.00% replacing

part of the cement. The mortars underwent characterization tests including fine aggregate analysis, compressive strength, absorption,

permeability (contact angle), and microstructural evaluations using SEM, TEM, XRD, and EDS. All tests were conducted under controlled

temperature and humidity following national standards (NTE INEN 488, 2518, 2536) and applicable ASTM norms. Results showed that a

0.25% nanoparticle dosage was most effective, increasing compressive strength from 12.60 to 16.61 MPa in type N mortars and from 30.54

to 37.87 MPa in type HS mortars. Water absorption slightly decreased in type N and slightly increased in type HS mortars. Permeability

analysis revealed hydrophilic behavior in type N mortars and a shift from hydrophobic to hydrophilic in type HS mortars. Microstructural

analysis indicated a denser matrix and enhanced chemical and physical interactions between nanoparticles and hydration products, improving

durability and mechanical performance. It is concluded that 0.25% clay nanoparticles is the optimal dosage to significantly improve

mechanical properties without negatively affecting absorption and permeability. This improvement is applicable for mortars used in plastering

works requiring enhanced strength. However, nanoparticle incorporation increases costs by 63.26% compared to conventional mortars,

requiring prior cost-benefit analysis for practical application.

Keywords: clay nanoparticles; plaster mortar; compressive strength; optimal dosage; mechanical properties.

Artículo original

Determinación del contenido óptimo de nanopartículas de arcilla en morteros para mejorar

la resistencia a la compresión en comparación con el mortero convencional para enlucido

Resumen

Este estudio se centra en mejorar las propiedades mecánicas de los morteros de yeso mediante la incorporación de nanopartículas de arcilla.

El objetivo principal fue determinar la dosificación óptima de nanopartículas de arcilla evaluando su efecto sobre la resistencia a la

compresión, la absorción de agua y la permeabilidad, con el apoyo de un análisis microestructural a escala nanométrica. Los morteros se

prepararon utilizando cemento Holcim tipo N y cemento Selvalegre tipo HS, arena de cantera lavada local y agua potable. Se añadieron

nanopartículas de arcilla en proporciones de 0,25 %, 0,50 %, 0,75 % y 1,00 %, sustituyendo parte del cemento. Los morteros se sometieron

a ensayos de caracterización que incluyeron análisis de agregados finos, resistencia a la compresión, absorción, permeabilidad (ángulo de

contacto) y evaluaciones microestructurales mediante SEM, TEM, XRD y EDS. Todos los ensayos se realizaron bajo temperatura y humedad

controladas, siguiendo las normas nacionales (NTE INEN 488, 2518, 2536) y las normas ASTM aplicables. Los resultados mostraron que

una dosificación de nanopartículas del 0,25 % fue la más efectiva, aumentando la resistencia a la compresión de 12,60 a 16,61 MPa en

morteros tipo N y de 30,54 a 37,87 MPa en morteros tipo HS. La absorción de agua disminuyó ligeramente en los morteros tipo N y aumentó

ligeramente en los morteros tipo HS. El análisis de permeabilidad reveló un comportamiento hidrofílico en los morteros tipo N y un cambio

de hidrofóbico a hidrofílico en los morteros tipo HS. El análisis microestructural indicó una matriz más densa y una mayor interacción

química y física entre las nanopartículas y los productos de hidratación, lo que mejora la durabilidad y el rendimiento mecánico. Se concluye

que el 0,25 % de nanopartículas de arcilla es la dosificación óptima para mejorar significativamente las propiedades mecánicas sin afectar

negativamente la absorción y la permeabilidad. Esta mejora es aplicable a morteros utilizados en trabajos de enlucido que requieren mayor

resistencia. Sin embargo, la incorporación de nanopartículas aumenta los costos en un 63,26 % en comparación con los morteros

convencionales, lo que requiere un análisis previo de costo-beneficio para su aplicación práctica.

Palabras Clave: nanopartículas de arcilla; mortero de yeso; resistencia a la compresión; dosificación óptima; propiedades mecánicas.

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1. Introduction

This research aims to develop an innovative mortar with

enhanced strength properties, while also evaluating adjacent

physical characteristics such as absorption, permeability, and

nanometric characterization to support the results obtained

(Alvansazyazdi et al., 2019). This approach could represent

a significant step toward the creation of more sustainable and

high-performance construction materials (Alvansazyazdi et

al., 2025a). Nanotechnology has long been a reality in

various fields of daily life; however, its limited applications

in the construction industry have not yet been consolidated

(Golshan et al., 2012). This is largely due to strategies that

rely on combining expensive nanomaterials with

conventional cementitious materials. Although such

practices may produce some positive effects on material

properties, they also significantly reduce the primary

competitive advantage of cement-based materials: their low

cost. Therefore, this study proposes and successfully tests a

new approach (Alvansaz Yazdi et al., 2014; Gaitero

Redondo, 2011).

Among the documented advances, pozzolanic nanoparticles

such as nanosilica have been shown to increase strength and

reduce porosity; titanium dioxide (TiO₂) contributes

environmental benefits through contaminant reduction; and

nanometric-scale void filling generates denser

microstructures with lower free water content

(Alvansazyazdi et al., 2025b, 2025c; López Molina, 2013).

Previous studies have demonstrated that modified clays can

act as pozzolanic or nucleating agents, accelerating

hydration and improving mortar compactness, thereby

supporting their use in the development of more efficient and

sustainable cementitious composites (Alvansazyazdi &

Rosero, 2019; Guzmán Cardona et al., 2024). Several

investigations have shown that the incorporation of

nanoparticles in mortars significantly improves compressive

strength and other physicomechanical properties compared

to conventional mortars. The best results have been achieved

with 2% nanosilica, 2–4% nanoalumina, and the

combination of 3% nanosilica with 1% nanoalumina, the

latter reaching the highest strength (Alvansaz et al., 2022;

Andrade Vieira, 2017).

Nanotechnology applied to mortars and concretes is

transforming the way hydraulic mixtures are designed, since

even small doses of nanoparticles can substantially alter the

physicochemical properties of the base material (Franco-

Luján et al., 2023). Due to their reduced size and high

surface-to-volume ratio, these particles enhance matrix

density, accelerate hydration, and act as nucleating agents

that promote the formation of C-S-H gel (Abhilash et al.,

2021; Franco-Luján et al., 2023). Recent studies on nanoclay

(montmorillonite) indicate that dosages below 3% of the

cement significantly improve mechanical strength and

reduce permeability, thanks to its function as a fine filler and

hydration catalyst. This contributes to densifying the

microstructure and reducing water absorption (Bunea et al.,

2023; Kafi et al., 2016). Future perspectives point toward the

engineering of materials specifically designed for each

application, supported by advanced techniques in synthesis,

characterization, and computational modeling (Franco-

Luján et al., 2023).

To study the properties of cementitious materials at the

nanoscale, analytical techniques such as X-ray Diffraction

(XRD), Scanning Electron Microscopy (SEM), Energy

Dispersive X-ray Spectroscopy (EDS), and Transmission

Electron Microscopy (TEM) are used. These methods enable

the understanding of phase variations in cement and

cementitious systems during hydration in the presence of

nanomaterials (Alvansazyazdi et al., 2025d; Ray et al.,

2021).

This study is presented as an experimental contribution

aimed at establishing the optimal proportion of nanoclay in

mortar mixtures, evaluating their mechanical performance

over time under controlled conditions. Identifying the

optimal addition percentage, analyzing its effects on

microstructure, and assessing potential technical and

economic advantages guide the methodology, allowing for a

critical comparison of the performance of modified mortar

against conventional mortar. It is hypothesized that the

incorporation of clay nanoparticles significantly enhances

mortar performance for plastering applications, by

increasing compressive strength, reducing absorption and

permeability, and reinforcing internal cohesion, thereby

contributing to durability. Furthermore, the modified mortar

is expected to offer additional properties such as greater

impermeability and potential improvement in acoustic

insulation. The findings will be valuable for professionals

and industries seeking to optimize their products without

increasing costs or compromising sustainability (Alvansaz et

al., 2019; Alvansazyazdi et al., 2024a).

2. Materials and Methods

2.1 Materials used

In this study, two types of cement (Table 1) were employed

for the preparation of mortars. “Holcim Maestro” Type N

cement is designed for high-quality masonry work and

provides a 50% reduction in CO₂ emissions, meeting and

exceeding the requirements of the NTE INEN 1806 standard

for non-structural use cements (Alvansazyazdi et al., 2025e;

Holcim, 2022). Meanwhile, “Selvalegre Campeón” Type HS

cement is a hydraulic cement with high sulfate resistance,

intended for dense concretes and structures requiring

durability against aggressive soils and waters, in compliance

with the NTE INEN 2380 standard (Alvansazyazdi et al.,

2025f; Cemento Selvalegre, 2025). The density of the

cement used was determined in the laboratory prior to mortar

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Determination of the Optimal Clay Nanoparticle Content in Mortars to Improve Compressive Strength

Compared to Conventional Mortar for Plastering

preparation, following the NTE INEN 156:2009 standard.

The values obtained were 2.82 g/cm³ for Type N and 2.836

g/cm³ for Type HS, both of which comply with the standards

required for proper performance in cementitious mixtures.

Table 1. Density type N and type HS cement

Test

Cement Density

Cement

Maestro Holcim

Campeón Selvalegre

Type

#1 (g/cm3)

2.83

#2 (g/cm3)

2.82

2.83

#3 (g/cm3)

2.81

2.85

Average (g/cm3)

2.82

2.836

The fine aggregate used was washed natural sand from the

Copeto quarry (Santo Domingo de los Tsáchilas), selected in

accordance with ASTM C33. This sand meets the

requirement of 100% passing through the No. 3/8” sieve, is

free of impurities, and exhibits controlled gradation,

ensuring proper workability and compaction of the mortar

(Table 2, Figure 1) (ASTM International, 2018; Morales et

al., 2020). Characterization of the fine aggregate was carried

out following various Ecuadorian standards. Gradation was

evaluated according to NTE INEN 696:2011 (Instituto

Ecuatoriano de Normalización [INEN], 2011a), obtaining an

average fineness modulus of 2.48 from three samples, within

the optimal range of 2.3–3.1.

Table 1. Sieve Analysis of Fine Aggregate – Sample 3

FINE AGGREGATE – SAMPLE No. 3 - Po=500,4 g

Sieve

Retained

% Retained

% Passing

Specification

Limits

Partial (g)

Cum. (g)

3/8

0,00

100,00

100

N.°4

0,00

100,00

95 - 100

N.°8

6,60

1,32

98,68

80 - 100

N.°16

99,90

106,50

21,32

78,68

50 - 85

N.°30

149,20

255,70

51,19

48,81

25 - 60

N.°50

145,40

401,10

80,30

19,70

10 - 30

N.°100

76,70

477,80

95,66

4,34

2 - 10

N.°200

14,60

492,40

98,58

1,42

0 - 2

Pan

7,10

499,50

100,00

0,00

∑

499,50

Mo (g)

500,40

0,90

% Error (< 0.3)

0,9982

0,18%

MF (2.3-3.1) =

2,50

Figure 1. Grain Size Distribution Curve of Fine Aggregate – Sample 3.

The content of fine material passing through the No. 200

sieve was determined according to NTE INEN 697:2010

(INEN, 2010a), resulting in 1.9%, below the maximum limit

of 3%. Density, specific gravity, and absorption were

measured following NTE INEN 856:2010 (INEN, 2010b),

yielding values of 2.74 g/cm³ and 1.7%, respectively, within

the accepted ranges. The loose and compacted unit mass was

evaluated according to NTE INEN 858:2010 (INEN, 2010c),

with results of 1573 kg/m³ and 1695 kg/m³, respectively,

falling within reference ranges. The presence of organic

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impurities was analyzed according to NTE INEN 855

(INEN, 2010d), showing no significant content; friable

particles were determined following NTE INEN 698 (0.8–

1.2%) (INEN, 2010e) and lightweight particles according to

NTE INEN 699 (0.4%) (INEN, 2011b), both below the

maximum allowable limits. All results confirm that the fine

aggregate meets the required standards to produce high-

quality mortars (Table 3).

Table 2. Summary of Fine Aggregate Characterization

General Characterization of Fine Aggregate

Test

Value

Unit

Range

Fine material, passing °200

sieve

1.9

<3%

Density

2.74

g/cm³

2.5-2.8 g/cm³

Absorption

1.7

<3%

Loose unit weight

1573

kg/m³

1200–1750 kg/m³

Compact unit weight

1695

kg/m³

1400–1900 kg/m³

Colorimetry

Gardner 1 White

to Transparent

Escala de

Gardner

Gardner >5

Friable Particles

0.8-1.2

<2%

Light Particles

0.4

<1%

Potable water was used in compliance with the specifications

of ASTM C1602/C1602M, which regulates mixing water for

concrete and mortar (ASTM International, 2022). The

Nanoclay (Figure 2), surface-modified, containing 25–30

wt.% trimethyl stearyl ammonium, supplied by Sigma-

Aldrich, was employed, specifically designed to disperse

effectively within cementitious matrices (Alvansazyazdi et

al., 2025g, 2025h). Although the aggregates may measure up

to < 20 µm, the individual platelets exhibit nanometric

dimensions, with particle sizes below 100 nm

(Alvansazyazdi et al., 2025i; Sigma-Aldrich, 2011).

Figure 2. Specifications of the Used Nanoclay.

2.2. Standard Mixing Procedure, Modified Mixture, and

Tests

The study methodology is presented through a flowchart

detailing the fundamental stages (Figure 3), all supported by

a thorough review of relevant standards: material

characterization, experimental design, test execution, and

interpretation of results (Alvansazyazdi et al., 2024b). This

framework ensures clarity, standardization, and replicability

of the process, thereby guaranteeing scientific rigor in

accordance with current regulations, as developed in this

section. To this end, a comparative experiment was designed

with one control group and several experimental groups,

while keeping all other parameters that may influence the

material’s strength constant (Alvansazyazdi et al., 2024c,

2024d; Hernández Sampieri et al., 2014).

In section A of this chapter, the description and

characterization of the materials used were established. The

following presents a brief explanation of the reference mix

proportion. According to the Ecuadorian Technical Standard

NTE INEN 488:2009, which specifies the test method for

determining the compressive strength of mortars in 50 mm

cube specimens, each mortar batch must be prepared with

three specimens for each testing age. For this research, a

standard mix proportion of 740 g of cement and 2,035 g of

sand was used, adjusting the amount of water required to

achieve a flow of 115% on the flow table, thus meeting the

requirements of the standard, which specifies a flow range of

110 ± 5% in 25 drops, as detailed in NTE INEN 2500

(Alvansazyazdi et al., 2025j; INEN, 2009a). The specimens

were tested at 1, 3, and 7 days to evaluate compressive

strength. The maximum permissible range of variation

among the three specimens is 9.4%. If the variation exceeds

this limit, the value furthest from the average is discarded,

and the range of the remaining two specimens is verified. If

fewer than two valid values remain after this procedure, the

test must be repeated (Table 4) (Alvansazyazdi et al., 2023;

INEN, 2009b).

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Determination of the Optimal Clay Nanoparticle Content in Mortars to Improve Compressive Strength

Compared to Conventional Mortar for Plastering

Figure 3. Flowchart of the Methodology Used in the Study.

Table 3. Mix proportion, w/c ratio, and flow of the reference

mortars obtained

Number of Specimens

9 Mortar Cubes

Material

Type N

Type HS

Cement (g)

740

Sand (g)

2035

Water (cm3)

423.1

412.2

RETIO W/C

0.572

0.557

FLOW (%)

115

114

Since the specimens of the reference mix were found within

this margin of error, it can be concluded that the mix

proportion is stable and reproducible. Therefore, it can be

used as a reference for the modified mixes with nanoclay at

0.25%, 0.50%, 0.75%, and 1.00% (three specimens per

dosage tested at 1, 3, 7, 28, and 90 days; testing ages). This

procedure ensures that the specimens meet the criteria for

workability, uniformity, and reliability of compressive

strength as established by the standard (Table 5).

Table 4. Material Quantities for Mortars According to Nanoclay

Percentage

% Nanoclay

0,25%

0,50%

0,75%

1,00%

Ages

1 – 3 – 7 – 28 – 90 días

Material

Material Quantity (g)

Type N Cement

Cement

738,15

736,3

734,45

732,6

Sand

2035

Water

423,1

Nanoclay

1,85

3,7

5,55

7,4

Type HS Cement

Cement

738,15

736,3

734,45

732,6

Sand

2035

Water

412,2

Nanoclay

1,85

3,7

5,55

7,4

2.2.1. Mortar preparation

Cracking and drying were carried out to obtain a

representative sample free of surface moisture, ensuring the

accuracy of the tests. Cracking allowed the aggregate to be

divided systematically and homogeneously, while oven dries

at a controlled temperature until constant mass, following the

standard, ensured the elimination of moisture. This

procedure guarantees that the sample is statistically

representative of the original batch and validates laboratory

results (Alvansazyazdi et al., 2025k; INEN, 2009b). The

nanoclay was previously dispersed in water by mechanical

stirring at 888.9 RPM, to ensure homogeneous distribution

and prevent agglomeration. This pre-mixing promotes

proper interaction of the nanomaterial with the cementitious

matrix and optimizes its effect on the properties of hardened

mortar. Cement, sand, nanoclay, and water were accurately

dosed using a calibrated electronic balance, ensuring precise

mix proportions and guaranteeing reproducibility and

reliability of the experimental results.

The mixing process consisted of an initial homogenization

of cement and water for 30 seconds, followed by the

incorporation of sand and, in nanoclay mixtures, the pre-

dispersed additive, continuing with another 30 seconds of

mixing. Subsequently, a 90-second pause was performed to

reincorporate material adhered to the walls and bottom of the

container, preventing losses or segregation. Finally, mixing

was resumed for 60 additional seconds, completing an

effective mixing time of 3 minutes, according to the standard

(INEN, 2009b).

The workability of fresh mortar was evaluated using the flow

table test established by ASTM C1437, which involves

placing the mixture in a truncated cone mold, removing it,

and applying 25 jolts in 15 seconds, then measuring the

average spread diameter. This parameter reflects mortar

workability and depends on factors such as water–cement

ratio, particle size distribution, and the presence of additives.

Values of 110–115 mm correspond to standard mortars,

whereas higher spreads indicate greater fluidity with

segregation risk, and lower values indicate drier, less

workable mixes (ASTM International, 2020a; Neville,

2011). Cubic specimens of 5 × 5 × 5 cm were molded

according to ASTM C109/C109M in two manually

compacted layers. After 24 hours, the specimens were

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demolded and cured in water at 20 ± 2 °C until testing at 1,

3, 7, 28, and 90 days (INEN, 2009b; Salgado et al., 2019).

2.2.2. Compressive Strength Test

Compressive strength was determined by testing at least

three specimens per condition, using a calibrated hydraulic

press that applied continuous axial load until failure, in

accordance with ASTM C109/C109M-20b. The maximum

recorded load was converted to compressive stress (MPa),

allowing evaluation and comparison of the mechanical

performance of nanoclay-modified mortars with

conventional mortars (ASTM International, 2020b; INEN,

2009b).

2.2.3. Water Absorption Test

Water absorption, related to mortar porosity and durability,

was determined according to ASTM C642-13, adapted for 5

× 5 × 5 cm cubes. The samples were oven-dried at 105 ± 5

°C until constant mass (m₁), weighing every 2 hours to verify

stability and extending drying time, if necessary, until

confirming the driest condition. Subsequently, the specimens

were immersed in water for 24 hours, and periodic

weighing’s were performed until saturated mass (m₂)

stabilized. The absorption percentage was calculated from

the difference between these two masses, allowing

evaluation of the material’s response to moisture and

external agents (ASTM International, 2013).

2.2.4. Permeability Test

The contact angle test, regulated by ASTM D7334-08, was

used as an indirect method to evaluate the surface

permeability of the mortar. It consists of measuring the angle

formed by a water droplet on the specimen surface,

determining whether it is hydrophilic (<90°) or hydrophobic

(>90°), and thus its tendency to absorb or repel moisture. The

procedure was carried out using samples with uniform

surfaces, controlled droplet volumes, and optical analysis

with a goniometer and specialized software under stable

environmental conditions. This test allowed comparison

between conventional mortars and nanoclay-modified

mortars to determine the additive’s effect on water

penetration resistance and material durability (Figure 4)

(ASTM International, 2008).

Figure 4. Contact Angle Measurement Process – Surface Permeability Assessment.

3. Results

3.1 Properties in Fresh State

The flow test, performed in accordance with NTE INEN

2500:2014 (Servicio Ecuatoriano de Normalización, 2014)

and ASTM C1437 (ASTM International, 2020b), showed

that the incorporation of nanoclay causes a progressive

decrease in workability in both types of cement (N and HS),

with the addition of nanoclay being indirectly proportional

to the fluidity of the mortar but still remaining within the

recommended range for plaster mortars (105–115%).

3.1.1. Type N Cement

The standard mortar had a fluidity of 116%, while the

addition of nanoclay caused a progressive reduction,

reaching 106% with 1.00% nanoclay. The dosages of 0.25%

and 0.50% maintained workability within the recommended

upper range (113% and 109%, respectively), ensuring good

handling on site. The variation in mortar fluidity according

to the percentage of nanoclay is shown in Figure 5.

Figure 5. Variation in mortar fluidity with type N cement,

depending on the addition of nano-clay

3.1.2. Type HS Cement

The fluidity of the standard mortar was 114%, decreasing to

108% with 1.00% nanoclay. The best ratio between

workability and stability was achieved with 0.25% nanoclay

(113%), while consistency was more affected at dosages of

0.50% and above. These results are shown in Figure 6.

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Determination of the Optimal Clay Nanoparticle Content in Mortars to Improve Compressive Strength

Compared to Conventional Mortar for Plastering

Figure 6. Variation in mortar fluidity with HS cement, depending

on the addition of nano-clay

3.2. Compressive Strength

The evolution of strength, evaluated at 1, 3, 7, 28, and 90

days, showed similar behavior in both cements (Type N and

Type HS), with a significant increase with 0.25% nanoclay

and stabilization or reduction at higher doses.

3.2.1. Type N Cement

At 90 days, the standard reached 12.60 MPa, while with

0.25% nanoclay, 16.61 MPa (+31.8%) was achieved. Higher

doses did not show consistent improvement: 0.50% → 12.94

MPa; 0.75% → 13.16 MPa; and 1.00% → 13.81 MPa. The

maximum yield was obtained at 0.25%, with evident

increases also at 28 days. The compressive strength results

over time are presented in Table 6, while their graphical

behavior is shown in Figure 7.

3.3. Absorption

Water absorption was evaluated in mortars with Type N and

Type HS cements, incorporating nanoclay in proportions of

0.25%, 0.50%, 0.75%, and 1.00% by weight of cement and

comparing the results with their respective standard mortars.

The results allow the identification of differential trends

between the two types of cement, as well as the impact of

nanomaterial dosage on the reduction or increase in

absorption capacity. Taking these results into account, some

differences were observed between mortars with Type N and

Type HS cement.

Table 5. Compressive strength results for type N mortars over

time, at different percentages of nano-clay.

Age

Standard

% of nanoclay in mortar

0,25%

0,50%

0,75%

(days)

(MPa)

1,06

1,21

0,81

1,21

0,95

4,48

4,23

3,69

4,66

4,70

6,83

7,14

4,88

8,44

7,63

10,22

12,74

9,76

9,65

10,15

12,60

16,61

12,94

13,16

13,81

Figure 7. Compressive strength curves for type N mortar, for each

percentage of nano-clay, and its behavior over time.

3.2.2. Type HS Cement

At 90 days, the standard reached 30.54 MPa and the mixture

with 0.25% nanoclay reached 37.87 MPa (+24.0%). The

0.75% dosage also performed well (34.49 MPa), although it

was below the optimum. Dosages of 0.50% and 1.00% did

not significantly exceed the standard. The compressive

strength results are presented in Table 7, and their evolution

over time is shown in Figure 8.

Table 6. Compressive strength results for HS-type mortars over

time, at different percentages of nano-clay.

Age

Standard

% of nanoclay in mortar

0,25%

0,50%

0,75%

(days)

(MPa)

5,13

5,19

4,47

5,16

4,97

14,69

15,48

14,25

13,58

9,89

20,20

21,22

19,06

24,09

19,76

25,37

29,31

25,88

26,80

25,88

30,54

37,87

29,62

34,49

32,58

Figure 8. Compressive strength curves HS mortar, for each

percentage of nano-clay, and its behavior over time

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3.3.1. Type N Cement

In mortar made with Type N cement, the standard showed an

average absorption of 12.00% at 28 days. The addition of

0.25% nanoclay slightly reduced the value to 11.89%, while

the 0.50% dosage achieved the lowest recorded absorption

(10.71%), showing a slight improvement in the compactness

of the matrix. However, from 0.75% onwards, the trend was

reversed, with 10.85% and 11.96% recorded at 0.75% and

1.00%, respectively, values close to those of conventional

mortar. These results suggest that nanoclay can contribute to

a temporary refinement of the porous network at low doses,

but at higher proportions, particle agglomeration limits its

positive effect. The absorption results are presented in Table

8, and their comparison according to the percentage of

nanomaterial is shown in Figure 9.

Table 7. Absorption results for type N mortar

Nanoclay

Dry Mass

(gr)

Wet Mass

(gr)

ABSORPTION

Standard

253,98

284,20

11,90%

12,00%

263,02

294,83

12,09%

0,25%

269,46

301,27

11,81%

11,89%

263,33

294,85

11,97%

0,50%

268,30

298,44

11,23%

10,71%

261,82

288,50

10,19%

0,75%

267,09

292,09

9,36%

10,85%

265,42

298,15

12,33%

1,00%

259,25

289,60

11,71%

11,96%

269,32

302,20

12,21%

Figure 9. Comparison of the % absorption in each % of

nanomaterial in type N mortar.

3.3.2. Type HS Cement

In mortar made with Type HS cement, the standard sample

had an absorption rate of 10.07%. With the addition of 0.25%

nanoclay, the absorption rate increased slightly to 10.29%,

which could be due to initial interference in the hydration

process. At 0.50%, the value remained practically the same

as the standard (10.12%), with no significant changes. From

0.75% and 1.00% onwards, there was a slight reduction to

9.72% and 9.66%, respectively, suggesting a more

pronounced microfilling effect at higher proportions.

However, the overall variations are minimal and do not

imply significant improvements in terms of durability. The

absorption results are presented in Table 9, while their

comparison according to the percentage of nanomaterial is

shown in Figure 10.

Table 8. Absorption results for type HS mortar.

Nanoclay

Dry Mass

(gr)

Wet Mass

(gr)

ABSORPTION

Standard

258,75

284,67

10,02%

10,07%

255,16

280,98

10,12%

0,25%

281,32

310,06

10,22%

10,29%

283,42

312,79

10,36%

0,50%

273,05

300,44

10,03%

10,12%

275,71

303,85

10,21%

0,75%

281,17

307,39

9,33%

9,72%

273,84

301,54

10,12%

1,00%

282,57

309,48

9,52%

9,66%

280,16

307,59

9,79%

Figure 10. Comparison of the % absorption in each % of

nanomaterial in HS-type mortar.

3.4. Surface Permeability

3.4.1. Type N Cement

The minimum absorption was 10.71% with 0.50% nanoclay,

compared to 12.00% for the standard. However, the

differences were not significant. The contact angle remained

hydrophilic (<90°) in all dosages, with 0.25% showing less

dispersion of values, suggesting greater surface

homogeneity. The comparative permeability results obtained

from the contact-angle measurements are presented in Table

10.

3.4.2. Type HS Cement

Absorption remained stable, with values between 9.66% and

10.29%. The standard mortar was hydrophobic (≈100°), but

the incorporation of any amount of nanoclay reduced the

angle below 90°, increasing its affinity with water. The effect

was more pronounced at 0.75% and 1.00%, with values

below 45°. The comparative permeability results obtained

for the Type HS mortar are presented in Table 11.

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Determination of the Optimal Clay Nanoparticle Content in Mortars to Improve Compressive Strength

Compared to Conventional Mortar for Plastering

Table 9. Comparison of permeability results (contact angle)

between mortar with standard N-type cement and mortar with %

nano-clay

PERMEABILITY – MORTAR WITH CEMENT N

NANOCLAY

Contact angles

∠ right (°)

∠ left (°)

Behavior

Standard

35.212

48.73

30.291

48.31

θ <

90°

Hydrophilic

55.824

58.901

55.152

55.742

0.25%

45.589

42.99

45.13

49.60

θ <

90°

Hydrophilic

44.162

53.516

39.208

50.163

0.50%

46.865

41.26

47.663

42.63

θ <

90°

Hydrophilic

39.946

39.547

36.982

40.668

0.75%

38.498

46.69

41.608

44.85

θ <

90°

Hydrophilic

40.657

35.335

60.927

57.615

40.025

45.68

45.537

51.13

θ <

90°

Hydrophilic

59.261

56.444

37.752

51.401

Table 10. Comparison of permeability results (contact angle)

between mortar with standard HS cement and mortar with % nano-

clay.

PERMEABILITY - MORTAR WITH HS CEMENT

NANOCLAY

Contact angles

∠ right (°)

∠ left (°)

Behavior

Standard

103,507

100,80

101,9

100,07

θ >

90°

Hydrophobic

99,951

99,32

98,952

99,03

0,25%

75,700

75,52

77,53

72,86

θ <

90°

Hydrophilic

81,136

72,47

69,731

68,59

0,50%

44,301

63,87

49,28

63,04

θ <

90°

Hydrophilic

85,061

86,27

62,235

53,56

0,75%

42,469

38,33

31,86

28,88

θ <

90°

Highly

hydrophilic

31,161

26,44

41,362

28,35

58,174

54,08

34,21

41,92

θ <

90°

Hydrophilic

51,68

41,86

52,395

49,7

3.5. Microstructural Characterization

SEM, TEM, XRD, and EDS analyses confirmed that 0.25%

nanoclay:

• Improves matrix compaction.

• Promotes the formation of C-S-H gel, identified by

the peak at 16° in XRD.

• Increases Ca, Si, and Al content according to EDS,

enhancing pozzolanic reactions.

• Partially reduces crystallinity, promoting denser and

more stable amorphous phases.

3.5.1. Type N Cement

• Scanning Electron Microscopy Analysis

The addition of 0.25% nanoclay showed a more compact

microstructure, with homogeneous plates and uniformly

distributed dark areas associated with a higher density of

heavy elements. This indicates a more closed and stable

matrix. The comparison between the standard mortar and the

mortar containing 0.25% nanoclay is shown in Figure 11.

Figure 11. Comparison of SEM results between mortar with

standard N-type cement (a) and mortar with 0.25% nano-clay (b).

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• Transmission Electron Microscopy Analysis

The analysis revealed smaller, irregular particles with higher

local density and dark areas, indicating intense interaction

between nanoclay and hydration products. However, some

agglomerations suggest that dispersion could be improved to

maximize the benefits of the nanomaterial. The comparison

of the TEM results is shown in Figure 12.

Figure 12. Comparison of TEM results between mortar with

standard N-type cement (a) and mortar with 0.25% nano-clay (b).

• X-Ray Diffraction Analysis

The mortar with nanoclay showed a reduction in the 16°

peak, indicating lower crystallinity of the C-S-H gel and

favoring an amorphous structure, as well as the

disappearance of the peak at 54°, associated with the

consumption of secondary phases such as ettringite. The

increase in the peak at 29° suggests greater portlandite

formation. The XRD pattern of the standard mortar is shown

in Figure 13, while the pattern corresponding to the mortar

containing 0.25% nanoclay is shown in Figure 14. A

comparative interpretation of the identified peaks is

presented in Table 12.

Figure 13. XRD Analysis - Type N Standard Mortar

Figure 14. XRD analysis - Mortar 0.25% nanoclay - type N

Table 11. Summary of interpretation of peaks in XRD in type N

mortar

ANGLE

(2θ)

Possible

crystalline phase

Chemical

compound

Interpretation

16°

C-S-H gel not very

neat

Hydrated

calcium silicate

Main phase of

hydrated cement,

usually not very

crystalline (partial

amorphism).

26°

Residual silica or

quartz

SiO₂

(crystalline)

It may come from

mineral additives or

sand.

29°

Portlandite

Ca(OH)₂

Direct product of

the hydration of C₃S

and C₂S (important

for evaluating the

degree of

hydration).

54°

Possible ettringite

or residual alite

C₃A, C₃S, or

secondary

phases

Disappearance may

indicate

consumption or

transformation by

the nanoclay.

• Energy-Dispersive X-Ray Spectroscopy Analysis

Increases in Si (+0.46%), Al (+0.26%), and Ca (+1.71%)

compared with the standard confirmed the incorporation of

nanoclay and its participation in pozzolanic reactions. Na

appeared exclusively in the sample with nanoclay,

corroborating its smectitic origin. The EDS results for the

control mortar are shown in Figure 15, while those obtained

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Vol.9, Num.18 (jul-dec 2026) ISSN: 2737-6451

Determination of the Optimal Clay Nanoparticle Content in Mortars to Improve Compressive Strength

Compared to Conventional Mortar for Plastering

for the mortar containing 0.25% nanoclay are shown in

Figure 16. The comparison of the elemental composition of

both samples is presented in Table 13.

3.5.2. Type HS Cement

Scanning Electron Microscopy Analysis

The standard mortar showed particles distributed in a less

orderly manner. With the addition of 0.25% nanoclay, the

microstructure became more compact, with homogeneous

plates and a greater presence of dark areas related to denser

and possibly crystallized phases. The comparison of both

microstructures is shown in Figure 17.

• Transmission Electron Microscopy Analysis

The sample with nanoclay presented irregular particles and

a more heterogeneous distribution, indicating an increase in

contact surface area but lower densification if the dispersion

is not optimal. The comparison of the TEM results between

the standard mortar and the modified mortar is shown in

Figure 18.

Figure 15. EDS Analysis – Control Mortar – Type N.

Figure 16. EDS Analysis – Mortar with 0.25% Nanoclay – Type N

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Table 12. Comparison of EDS results between mortar with standard N-type (Figure 15) cement and mortar with 0.25% nano-clay (Figure

16).

Symbol

% by normalized weight

0% nanoclay

% by weight

normalized 0.25%

nanoclay

Variation (%)

Interpretation

61,45%

58,37%

🔽 -3,08%

Slight decrease may be due to an increase in denser

phases (such as silicates or aluminates) or partial

replacement of bound water.

—

0,64%

🆕 Nuevo

Presence attributable to impurities in the nano-clay, as it

does not appear in mortar without addition.

0,78%

0,72%

🔽 -0,06%

Minor changes, probably related to the cement matrix.

2,16%

2,42%

🔼 +0,26%

Slight increase possibly due to the structure of the

nanoclay (montmorillonite is rich in Al).

5,81%

6,27%

🔼 +0,46%

Increase consistent with the silica contribution of the

nanoclay.

0,58%

0,54%

🔽 -0,04%

No significant changes.

28,04%

29,75%

🔼 +1,71%

Significant increase may indicate higher presence of

portlandite or hydration products.

1,17%

1,30%

🔼 +0,13%

It may be associated with traces of Fe in the nano-clay or

cement.

Figure 17. Comparison of SEM results between mortar with standard HS cement (a) and mortar with 0.25% nano-clay added (b).

Figure 18. Comparison of TEM results between mortar with standard HS cement (a) and mortar with 0.25% nano-clay (b).