Effects of thermal cycling accelerated aging on PET-Modified rendering mortars: a physico-mechanical analysis

Lemos, Bárbara; Yamaguti, Lucas do Carmo; Oliveira, Victor Molieri de; Higuti, Ricardo Tokio; Akasaki, Jorge Luis; Fioriti, Cesar Fabiano

doi:10.1590/s1678-86212025000100922

Abstract

This study evaluated rendering mortars with 5%, 10%, 15%, and 20% fine aggregate replacement by polyethylene terephthalate (PET) flakes, subjected to accelerated aging through thermal cycling. Properties such as fluidity, water retention, immersion absorption, capillary absorption, vapor permeability, compressive strength, ultrasonic pulse velocity, and dynamic modulus of elasticity were analyzed. The mean spreading diameter was highest for the A10% mix. Both capillary and immersion water absorption were highest for the A20% mix. Non-aged samples exhibited higher vapor permeability. Compressive strength was highest for the A15% mix, while the highest ultrasonic pulse velocity was observed in the PET-free sample. It was concluded that PET contents of up to 10% provide a balance between mechanical performance and durability. This study contributes to the application of recycled PET in rendering mortars.

Keywords
PET-modified mortar; Accelerated aging; Thermal cycling; Cementitious composites; Durability assessment

Resumo

Este estudo avaliou argamassas de revestimento com substituição de 5%, 10%, 15% e 20% do agregado miúdo por flocos de politereftalato de etileno (PET), submetidas a envelhecimento acelerado por ciclos térmicos. Propriedades como fluidez, retenção de água, absorção por imersão, absorção capilar, permeabilidade ao vapor, resistência à compressão, velocidade de pulso ultrassônico e módulo de elasticidade dinâmico foram analisadas. O diâmetro médio de espalhamento foi maior para a mistura A10%. Tanto a absorção capilar quanto a imersão foram maiores para a mistura A20. Amostras não envelhecidas apresentaram maior permeabilidade ao vapor. A resistência à compressão foi maior para a mistura A15%, enquanto a maior velocidade de pulso ultrassônico foi observada na amostra sem PET. Concluiu-se que teores de PET de até 10% proporcionam um equilíbrio entre desempenho mecânico e durabilidade. Este estudo contribui para a aplicação de PET reciclado em argamassas de revestimento.

Palavras-chave
Argamassa modificada com PET; Envelhecimento acelerado; Ciclagem térmica; Compósitos cimentícios; Avaliação de durabilidade

Introduction

The inadequate management of urban solid waste represents one of the most pressing environmental challenges of the 21st century, particularly concerning the disposal of polymeric materials. According to the Global Plastics Outlook report by the Organisation for Economic Co-operation and Development (OECD) (2022), approximately 460 million tons of plastics were produced globally in 2019, with projections exceeding 600 million tons by 2030. Among discarded plastic waste, only 9% is recycled worldwide, while 19% is incinerated, 50% ends up in landfills, and the remaining 22% is disposed of in uncontrolled dumps, openly burned, or released into the environment. In Brazil, despite plastic recycling reaching 1.4 million tons in 2023, the post-consumer mechanical recycling rate remains low at 20.6%, highlighting a significant underutilization of its potential (ABIPLAST, 2023).

The improper disposal of plastic waste in terrestrial and aquatic environments exacerbates soil pollution, compromises water quality, and poses a severe threat to wildlife, which is susceptible to accidental ingestion or entanglement. Over time, the physical and chemical degradation of these materials generates micro and nanoplastics, whose effects remain poorly understood but raise growing concerns regarding potential risks to human health and ecosystem stability.

In this context, polyethylene terephthalate (PET), widely used in disposable packaging, particularly beverage bottles, stands out as one of the most abundant plastic wastes in urban environments. Its high chemical resistance and thermal stability contribute to its persistence in the environment, intensifying ecological impacts when improperly discarded. Consequently, strategies for valorizing recycled PET in sustainable industrial applications, such as construction, have gained increasing attention as part of decarbonization efforts and the promotion of a circular economy, aligned with the United Nations' Sustainable Development Goals, in particular SDG 11 (Sustainable Cities and Communities) and SDG 12 (Responsible Consumption and Production) (UNITED NATIONS, 2015a; 2015b).

The construction sector is traditionally characterized by high consumption of natural resources and significant waste generation, accounting for approximately 40% of global raw material consumption and 35% of solid waste production (United Nations Environment Programme (UNEP) and the United Nations Human Settlements Programme (UN-Habitat), 2021). In response, the incorporation of plastic waste into cementitious composites has emerged as a promising alternative to reduce natural aggregate extraction, mitigate environmental impacts, and develop more sustainable materials. Numerous studies have explored the feasibility of partially replacing fine aggregates with recycled PET, demonstrating benefits such as reduced density, improved impact resistance, and lower thermal conductivity in mortars (Spósito et al., 2020; Oliveira et al., 2020; Garcia et al., 2021; Patrício, 2021; Lerna et al., 2023; Resende et al., 2024).

Recent research has investigated PET incorporation in cementitious composites, either as a partial aggregate substitute (Spósito et al., 2020; Oliveira et al., 2020; Garcia et al., 2021; Resende et al., 2024; Almeshal et al., 2020; Bamigboye et al., 2021; Belmokaddem et al., 2020; Gravina et al., 2021; Górak et al., 2021; Hao et al., 2024; Kangavar et al., 2023; Khan et al., 2022; Kunthawatwong et al., 2022; Skibicki et al., 2022; Su et al., 2025; Tayeh et al., 2021; Wattanavichien; Iwanami, 2024) or as polymeric fibers (Abdullah; Haido, 2022; Alani et al., 2022; Chinchillas-Chinchillas et al., 2020; Gao et al., 2025; Lee et al., 2023; Mohammed; Rahim, 2020; Mohammed; Karim, 2023; Mouna et al., 2024; Tang et al., 2022; Zeng et al., 2020; Křížová et al., 2024; Shaikh, 2020). When used as an aggregate replacement, studies consistently report a decline in mechanical properties, such as compressive and tensile strength (OLIVEIRA et al., 2020; Garcia et al., 2021; Resende et al., 2024; Almeshal et al., 2020; Bamigboye et al., 2021; Belmokaddem et al., 2020; Gravina et al., 2021; Górak et al., 2021; Hao et al., 2024; Kangavar et al., 2023; Kunthawatwong et al., 2022; Skibicki et al., 2022; Su et al., 2025; Tayeh et al., 2021; Wattanavichien; Iwanami, 2024), especially at higher substitution rates.

Regarding the specific properties evaluated in mortars with partial sand replacement by PET, previous studies have addressed characteristics such as workability (Spósito et al., 2020; Oliveira et al., 2020; Patrício, 2021; Górak et al., 2021; Kunthawatwong et al., 2022), water retention (Spósito et al., 2020), compressive strength (Oliveira et al., 2020; Garcia et al., 2021; Patrício, 2021; Górak et al., 2021; Hao et al., 2024; Kunthawatwong et al., 2022; Skibicki et al., 2022; Su et al., 2025), water vapor permeability (Spósito et al., 2020), ultrasonic pulse velocity and dynamic modulus of elasticity (Spósito et al., 2020; Kunthawatwong et al., 2022), capillary water absorption (Spósito et al., 2020; Oliveira et al., 2020; Garcia et al., 2021; Patrício, 2021), and immersion water absorption (Spósito et al., 2020; Kunthawatwong et al., 2022). Furthermore, techniques such as Scanning Electron Microscopy (SEM) (Spósito et al., 2020; Górak et al., 2021; Kunthawatwong et al., 2022; Skibicki et al., 2022; Su et al., 2025) have also been used to investigate the microstructural modifications promoted by PET incorporation.

However, despite the growing number of investigations on cementitious composites with PET addition, most studies focus on analyses under ideal curing conditions, neglecting the effects of prolonged exposure to environmental degradation agents. In tropical climate regions like Brazil, natural cycles induce significant alterations in cementitious coating properties, reducing their service life. Under these conditions, durability studies with laboratory simulations that replicate long-term degradation processes in a reduced timescale become essential.

Many recents researchs has extensively employed accelerated aging protocols to assess cementitious composite performance, utilizing several standardized methods like controlled temperature-humidity variations (Gehlot; Shrivastava, 2024; Mudi; Shaw, 2025; Parracha et al., 2024; Sadrolodabaee et al., 2022; Wang et al., 2025), combined thermal cycles (heat-rain/heat-cold) and freeze-thaw conditioning (Mudi; Shaw, 2025; Gou et al., 2023; Kosiachevskyi et al., 2022; Zhao et al., 2023), aggressive marine environment simulations through seawater/saline immersion (Wang et al., 2025; Gou et al., 2023; Cao et al., 2024; Jiang et al., 2025; Lin et al., 2025; Thomas et al., 2021; Zeng et al., 2022), wetting-drying cycles (Alcivar-Bastidas et al., 2024; Cheng et al., 2020; Gao et al., 2022; Huang et al., 2025; Noor-E-Khuda, 2021; Niu et al., 2023; Sainz-Aja et al., 2021; Song et al., 2024; Yang et al., 2022), deionized water immersion tests (Santos et al., 2025), chemical resistance evaluations using sulfate/acid solutions (Mudi; Shaw, 2025; Zeng et al., 2022; Cheng et al., 2020; Pachla et al., 2024). These methodologies collectively address tropical degradation mechanisms while enabling laboratory-accelerated durability assessments.

Alcivar-Bastidas et al. (2024) analyzed the behavior of fiber-reinforced mortars containing alkali-treated abaca fibers, subjected to two distinct accelerated aging processes involving wetting and drying cycles (WD-1 and WD-2). In WD-1, based on the protocol by Neves Junior et al. (2019), water-saturated samples after 24 hours of immersion were dried at 36±1 °C in a forced ventilation chamber for 48 hours, with the process repeated 6 times. In WD-2, adapted from Wei et al. (2016), specimens were alternately immersed and dried at 70 °C, with mass variation monitored to determine the end of the cycles. After aging, the results indicated that the addition of treated fibers led to improvements of up to 20% in compressive strength, 30% in tensile strength, and 11% in flexural strength compared to the reference mortar, particularly after the WD-1 cycle, which was considered less aggressive.

Song et al. (2024) investigated the durability of cement composites reinforced with ZrO₂-modified hemp fibers, subjected to an accelerated aging protocol involving wetting-drying cycles based on the method by Stapper, Gauvin, and Brouwers (2021). The samples were immersed in water at room temperature for 7 days, followed by 4 days of oven drying at 60 °C and then 3 hours of cooling at ambient temperature. This cycle was repeated 5 times (totaling 5 full cycles). The results demonstrated that ZrO₂ modification enhanced the composites' compressive and flexural strength, yielding an improvement of up to 18% compared to unmodified composites. Additionally, it reduced water absorption and water vapor permeability, improving the composites' resistance to aging cycles. This effect was most pronounced after the first three cycles, where the modification proved most effective in mitigating aging-induced damage.

Among the employed procedures, accelerated aging through hygrothermal cycles has been widely adopted as a methodological tool to assess the durability of cementitious composites (GAO et al., 2022; Noor-E-Khuda, 2021; Yang et al., 2022). Alcivar-Bastidas et al. (2024) and Neves Júnior et al. (2019) emphasize that modified mortars with recycled additives exhibit significant sensitivity to these cycles, directly impacting their physical and microstructural properties. Key observed effects include increased water absorption, mass loss, reduced cohesion, and heightened pore connectivity.

To assess the degradation mechanisms in tropical climates, wetting-drying cycles emerge as the most appropriate methodology due to their unique ability to replicate the synergistic effects of high humidity and thermal fluctuations characteristic of these regions. As demonstrated by Kumar et al. (2025), Brazilian tropical conditions present a distinctive combination of persistent relative humidity, intense UV radiation and cyclic temperature variations between 25-35 °C. This protocol effectively simulates three fundamental degradation pathways: differential thermal expansion between composite phases, ionic transport through capillary networks during wet phases, and microcrack propagation during drying cycles - all critical factors governing long-term durability in cementitious systems

In this context, the present study aimed to evaluate the behavior of rendering mortars with partial replacement of fine aggregate by recycled PET, subjected to different accelerated aging cycles through wetting and drying. By analyzing hygroscopic, physical, mechanical, and microstructural parameters across three distinct stages of cyclic exposure, the research investigated the progression of composite degradation and the effects of polymer addition on durability performance.

Experimental program

Materials

The Portland cement used was a composite type with carbonate filler addition (CP II-F-32), complying with NBR 16697 (ABNT, 2018) standards and equivalent to C595 (ASTM, 2025) Type IL cement, containing 6-10% pozzolanic material by mass. The hydrated lime was CH-III type according to NBR 7175 (ABNT, 2013), equivalent to C207 (ASTM, 2024) Type S, with a minimum of 90% calcium hydroxide [Ca(OH)₂] in its composition.

Natural river sand (NS) was used as conventional fine aggregate. For partial replacement, post-consumer recycled PET flakes supplied by Global PET S.A. (São Carlos, Brazil) were incorporated, with a median diameter (D₅₀) of 1.19 mm.

Water used for mixture preparation was sourced from the public supply system and complied with the requirements of NBR 15900-1 (ABNT, 2009) (equivalent to C1602 (ASTM, 2022)).

Figure 1 shows the morphology of the recycled PET flakes, while Figure 2 presents the comparative particle size distribution between natural sand and PET. Table 1 summarizes the physical properties of the materials used as fine aggregates.

Figure 1
Recycled PET flakes

Figure 2
Comparative particle size distribution between NS and PET

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Table 1
Physical properties of NS sand and PET

The particle size distribution curves (Figure 2) reveal a marked disparity between the natural sand (NS) and the recycled PET aggregates. The natural sand exhibits a smaller particle size, with the majority of particles concentrated between approximately 0.15 mm and 1.0 mm, which favors a dense packing arrangement and reduced void content. In contrast, the PET particles display a significantly coarser profile, with a substantial fraction retained on sieves larger than 1.0 mm and a less continuous grading. Such characteristics are likely to impair packing density, increase interparticle voids, and consequently elevate water demand to achieve the same workability as NS-based mixtures. Furthermore, the reduced specific surface area and smoother morphology of PET particles may weaken the interfacial transition zone (ITZ) with the cementitious matrix, potentially influencing both mechanical performance and durability.

The physical characterization (Table 1) reinforces the previous observations, showing that PET has a notoriously lower specific gravity (1.35 g/cm³) and bulk density (430 kg/m³) compared to natural sand (2.64 g/cm³ and 1710 kg/m³, respectively), reflecting its polymeric nature and lower mass per unit volume. The higher maximum particle size (2.36 mm) and fineness modulus (3.79) of PET, relative to natural sand (0.60 mm and 1.36, respectively), corroborate its coarser grading and scarcity of fine particles, which may reduce packing density and increase the void ratio in the mixture. Additionally, PET exhibits lower water absorption (0.10%) than natural sand (0.45%), associated with its hydrophobic surface and smooth texture, potentially affecting fresh-state workability and the microstructural development of the ITZ. These differences highlight the necessity of adjusting mix design parameters to mitigate potential reductions in mechanical strength and optimize the physical performance of mortars incorporating PET as a partial sand replacement.

Mix proportions

All formulated rendering mortars were based on those used by Spósito et al. (2020). The mixtures employed a binder matrix composed of Portland cement and hydrated lime in a 1:1:5 volumetric ratio (cement: hydrated lime: NS). A constant water/binder (w/b) ratio of 1.04 was maintained for all formulations.

Volumetric replacement of NS with PET flakes was implemented at four distinct levels: 5%, 10%, 15%, and 20%. The reference formulation without PET addition was designated as A0%. Other compositions were labeled A5%, A10%, A15%, and A20% according to their respective conventional fine aggregate replacement percentages. The nomenclature follows the pattern Ax%, where "x" represents the volumetric fraction of PET replacing natural aggregate (ranging from 0% to 20%). Table 2 presents the adopted proportions and corresponding identification of each evaluated mix design.

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Table 2
Mix proportions of mortar formulations (kg/m³)

Samples preparation and curing conditions

The mixing procedure followed NBR 16541 (ABNT, 2016) guidelines with specific adaptations to ensure material homogeneity. Solid components were weighed, and the mixer bowl was pre-moistened. The binders (Portland cement and hydrated lime) were initially combined with mixing water and mechanically blended at low speed for 30 seconds. Subsequently, NS and PET flakes were incorporated, followed by high-speed mixing for 60 seconds. The sequence concluded with 90 seconds of manual homogenization and a final 60-second high-speed mechanical mixing cycle to ensure complete uniformity.

Fresh mortars were cast into prismatic specimens with dimensions of 4 × 4 × 16 cm (larger specimens) and 1.5 × 4 × 5 cm (smaller specimens), compacted using vibration at 45.7 Hz for 15 seconds. Molds were sealed with plastic film and stored in a humidity chamber for 48 hours (larger specimens) and 24 hours (smaller specimens), respectively. After demolding, specimens underwent 28-day moist curing at 23±2 °C and > 95% RH.

Prior to testing, specimens were oven-dried at 80±5 °C for 48 hours (larger prisms) or 12 hours (smaller prisms) to eliminate interstitial water, then acclimatized to laboratory conditions until thermal stability was achieved. For water vapor permeability tests, cylindrical specimens (Ø145×20mm) were prepared using identical procedures as the 4×4×16cm prisms.

Mortar characterization was performed through a series of tests evaluating both fresh and hardened state properties. The analyses covered physical, mechanical, and microstructural aspects by assessing the following parameters: water retention, consistency index, capillary water absorption, immersion water absorption, water vapor permeability, compressive strength, ultrasonic pulse velocity, and scanning electron microscopy (SEM). The experimental tests were conducted according to the following technical standards: water retention (EN 1015-8) (ECS, 1999); consistency index (NBR 13276) (ABNT, 2016); capillary water absorption (NBR 15259) (ABNT, 2005a); immersion water absorption (NBR 15259) (ABNT, 2005a); water vapor permeability (EN 1015-19) (ECS, 2000); compressive strength (NBR 13279) (ABNT, 2005b); and ultrasonic pulse velocity (C597-22) (ASTM, 2022). Microstructural analysis was performed using scanning electron microscopy (SEM) with protocols adapted for cementitious composites on fractured surfaces obtained from fragments of the compressive strength test. The samples were coated with a thin layer of gold using a Quorum Q150R ES sputter coater to improve conductivity. Analyses were conducted in a Zeiss EVO LS15 microscope, operating with a secondary electron detector under the parameters indicated in the figure captions (Figures 10a, 10b, 10c and 10d). Additionally, visual inspections were conducted after each accelerated aging cycle to identify morphological changes, surface cracks, and other macroscopic manifestations in the specimens.

Figure 10
Scanning electron microscopy as a function of aging cycles. Unaged (a); first cycle (b); second cycle (c); and third cycle (d)

Accelerated aging

The experimental protocol was based on the methodology proposed by Gao et al. (2022), with adaptations in exposure times and immersion solution to ensure compatibility with the specific characteristics of the evaluated composites. Each cycle consisted of three stages: immersion of specimens in water at room temperature for 17 hours to promote capillary saturation, subsequent drying in an oven at 60 °C for 6 hours (a temperature also used by Noor-E-Khuda (2021) and Cheng et al. (2020)) to simulate thermal shrinkage without inducing premature cracking and final resting period in a controlled environment for 1 hour to ensure gradual thermal transition between process phases.

The drying temperature selection was based on findings that higher temperatures (frequently used in previous studies) promote microcrack formation in the cementitious matrix, especially in composites with alternative materials like PET, which would compromise results (Yang et al., 2022).

Three distinct experimental series were conducted, consisting of 12, 13, and 14 consecutive cycle repetitions, equivalent to 12, 13, and 14 days of exposure. Similar procedures were employed by Alcivar-Bastidas et al. (2024), who subjected samples to alternating immersion and oven-drying cycles at 36±1 °C, and by Neves Júnior et al. (2019) for mortars containing recycled additives. Following each stage, specimens underwent both destructive and non-destructive testing to characterize the evolution of physical, mechanical, and microstructural properties throughout the aging process.

Statistical data treatment

The results from various tests were subjected to statistical analysis to identify significant variations among mixes with different PET contents and throughout the accelerated aging cycles. For datasets exhibiting parametric behavior, we performed analysis of variance (ANOVA) followed by Tukey's multiple comparison test. When ANOVA assumptions were not met, the Kruskal-Wallis test was employed with Dunn's post-hoc analysis for multiple comparisons. All statistical procedures were conducted using OriginPro^® 2025 software (Version 11.0) to ensure precise and reliable result interpretation, with a 95% confidence level (α = 0.05) applied throughout the analysis. Data normality was verified using Shapiro-Wilk tests (p>0.05), while homoscedasticity was confirmed via Levene's test, and effect sizes were calculated using η² (eta-squared) for significant ANOVA outcomes.

Results and discussion

Water retention

Figure 3 presents the results obtained in this phase of the study, where subtle variations between the evaluated mixes can be observed, with a maximum difference of 3.77%.

Figure 3
Water retention capacity (%) versus PET content (vol%)

The mortar with 20% PET content (A20%) exhibited the highest water retention value (91.79%), while the reference mixture (A0%) showed the lowest (88.02%). Analysis of variance (ANOVA) revealed statistically significant differences between groups (p < 0.05), as confirmed by Tukey's multiple comparisons test, except between A5% and A15% mixes where the difference was non-significant.

The absence of a linear trend aligns with findings by Spósito et al. (2020), who observed inverse behavior under different environmental conditions, demonstrating that variables like temperature and relative humidity directly affect water retention capacity. From a microstructural perspective, PET presence may modify the matrix's capillary network, interfering with water redistribution and binder interaction.

Consistency index

The consistency index results are presented in Figure 4.

Figure 4
Consistency index of PET-modified mortars

All PET-modified mortars exhibited greater flow diameters than the reference mix (A0%). The A10% formulation achieved the maximum spread (353.33 mm), representing a 7.83% increase over the PET-free mortar (327.67 mm) and constituting the only statistically significant difference (p = 0.03) according to Tukey's test. Other replacement levels showed no statistical significance, indicating maintained workability.

PET's hydrophobic nature, low surface roughness, and reduced water absorption promote mixture fluidity by decreasing internal friction - a phenomenon previously documented by Spósito et al. (2020), Oliveira et al. (2020) and Resende et al. (2024). However, researchers including Patrício (2021) and Zerig et al. (2023) reported decreased flowability at replacement levels exceeding 15% or when using fibrous geometries. These variations underscore the critical importance of particle size control and optimal replacement ratios for preserving suitable rheological properties.

Capillary water absorption

Figure 5 presents the capillary coefficient values at different accelerated aging stages.

Figure 5
Capillary water absorption after 3 aging cycles

In the initial state, PET-modified mixes showed higher absorption than the reference (A0%), particularly A20% (21.79 g/dm²·min¹/²). After the first aging cycle, A20% reached the highest value (25.81 g/dm²·min¹/²), while A0% exhibited reduced absorption (14.69 g/dm²·min¹/²), suggesting possible matrix densification through delayed hydration.

The second and third cycles revealed progressive absorption increases, especially in higher PET-content mixes, with A20% reaching 30.51 g/dm²·min¹/² – a 40.05% increase from the unaged condition. This pattern indicates cumulative degradation, enhancing pore connectivity and microcrack formation, as also reported by Parracha et al. (2024), Maia et al. (2021) and Xiong et al. (2021).

ANOVA showed statistical significance between cycles for all formulations. However, A15% and A20% showed no difference between the second and third cycles, suggesting structural stabilization from degradation mechanism saturation.

Water absorption by immersion

Figure 6 presents the results obtained after three accelerated aging cycles.

Figure 6
Water absorption by immersion after 3 aging cycles

Prior to aging exposure, a progressive increase in water absorption was observed with rising PET content, ranging from 15.00% (A0%) to 17.63% (A20%). This trend is attributed to polymer-induced porosity enhancement, as similarly reported by Spósito et al. (2020) for recycled-PET composites. The 2.63 percentage point increase corresponds to a 17.5% relative growth in absorption capacity compared to the reference mortar.

Following the first aging cycle, water absorption decreased in formulations A0% to A15%, indicating matrix densification through continued hydration. In contrast, the A20% composition showed a marginal 0.32% increase (from 17.63% to 17.95%), suggesting threshold behavior at high PET content. As aging progressed, most mixes showed continued absorption reduction, suggesting microstructural stabilization. Exceptions were A10% and A15%, which exhibited slight increases (0.3-0.5%) likely due to pore re-opening at polymer-cement interfaces.

Statistical analysis (ANOVA and Tukey's test) confirmed significant differences between aging cycles for formulations A0%, A5%, A10%, and A15%, with notable stabilization emerging from the second cycle onward. The A20% formulation showed no statistically significant variation between cycles (p > 0.05), suggesting early structural stability likely favored by hydrophobic nature of PET and weak interfacial bonding with the cement matrix.

Water vapor permeability

Mass variations observed throughout the aging cycles are shown in Figure 7(a) and 7(d).

Figure 7
Water vapor permeability (a) unaged, (b) after 1 cycle, (c) after 2 cycles, and (d) after 3 cycles

In the initial state (Figure 7a), composites with higher PET content (A10%, A15%, A20%) showed greater mass variation, indicating higher permeability associated with increased porosity induced by weak PET adhesion to the cementitious matrix. The lowest permeability was observed for A5%, behavior similar to that reported by Spósito et al. (2020) and Silva, Brito and Veiga (2014), who related increasing PET content to enhanced water vapor diffusion.

After the first cycle (Figure 7b), a generalized reduction in permeability was observed, attributed to precipitation of hydration products and matrix compaction. A20% remained the mix with highest permeability, while A5% maintained the lowest values.

In the second cycle (Figure 7c), A0%, A15% and A20% continued reducing their permeability, while A5% and A10% showed slight increases, suggesting partial pore re-opening or capillary network redistribution. After the third cycle (Figure 7- d), all formulations showed continued reduction, demonstrating matrix structural stabilization. A10% and A15% achieved the highest absolute reductions (86.13% and 83.07% respectively).

Parracha et al. (2024) and Gouveia (2021) also identified significant permeability reduction in mortars subjected to accelerated aging.

Statistical analysis using the Kruskal-Wallis test indicated statistically significant differences (p < 0.05) between cycles for all formulations. Dunn's test revealed these differences were concentrated between the initial state and aged cycles, with comparisons among cycles 1, 2 and 3 being statistically similar (p > 0.10), suggesting stabilization after the first cycle. The most sensitive behavior to variation was observed in A10% and A15% formulations.

Compressive strength

Figure 8 presents the average results obtained across different accelerated aging cycles.

Figure 8
Compressive strength in different accelerated aging cycles

In the initial state, the A15% formulation achieved the highest strength value (6.83 MPa), followed by A0% and A5% (both 6.32 MPa). A10% showed the lowest performance (5.98 MPa), supporting studies that report strength reduction with increasing PET content (Oliveira et al., 2020; Lerna et al., 2023; Resende et al., 2024). Conversely, specific findings like those of Garcia et al. (2021) and Patrício (2021) demonstrate that moderate PET contents can enhance initial performance.

With the application of aging cycles, a gradual strength loss was observed. After the first cycle, the reduction ranged from 4% to 11%, with A10% and A15% showing the most pronounced decreases. The second cycle intensified the strength loss, particularly for A15% (−21.3% vs initial). By the third cycle A0% and A5% exhibited stabilization, A10% and A15% maintained significant decline. A20% showed slight recovery suggesting internal matrix reorganization.

The statistical analysis (ANOVA and Tukey) revealed significant differences between cycles for PET composites, particularly between the last two cycles, while the reference mortar (A0%) showed no statistically relevant variation.

Ultrasonic pulse velocity analysis

Figure 9 presents the mean results of ultrasonic pulse velocity (UPV) throughout the aging cycles.

Figure 9
Wave propagation velocity as a function of aging cycles

In the initial condition, the reference mortar (A0%) exhibited the highest UPV, indicating greater density and cohesion of the cementitious matrix. Increasing PET content led to a progressive reduction in UPV, reaching the lowest value in A20% – a behavior associated with increased porosity and polymer-induced stiffness loss, as previously reported by Spósito et al. (2020).

After the first cycle, A0%, A10%, and A20% showed increased UPV, likely due to secondary hydration. In contrast, A5% and A15% displayed significant reductions (−5.34% and −7.22%, respectively), suggesting the onset of microcracking.

Dynamic elastic moduli (estimated via UPV) confirmed this trend, with A15% showing a 13.89% decrease and A20% remaining unchanged.

After two cycles, degradation became more evident. Most composites recorded reduced UPV, except A15%, which showed a temporary increase (+8.37%), suggesting structural reconfiguration. The highest stiffness loss was observed in A20%, with a 26.92% reduction.

After three cycles, the generalized UPV decrease demonstrated progressive degradation. A0% showed −12.72%, A5% −10.19%, and A15% −13.58%. Conversely, A10% and A20% exhibited moderate increases, indicating possible localized effects from hydration product precipitation. A20%'s final elastic modulus was the lowest among the composites (0.0021 GPa).

Statistical analysis (ANOVA and Tukey) confirmed significant differences between cycles, particularly for A5%, A15%, and A20%, reflecting these formulations' sensitivity to thermal aging. Meanwhile, A10% showed statistically significant fluctuations, suggesting nonlinear behavior throughout the cycles.

Microstructural analysis

The microstructural analysis was conducted via SEM on samples of the A15% formulation, selected based on its superior initial mechanical performance. The image of the unaged sample (Figure 10a) reveals a PET particle embedded in the cementitious matrix, bordered by an interfacial transition zone (ITZ) with pronounced porosity. The weak interfacial adhesion stems from PET's low surface roughness, paste shrinkage during curing and material polarity mismatch, collectively promoting interfacial discontinuities as observed by Spósito et al. (2020). The microstructure shows C-S-H gel formation preferentially around sand particles, with the matrix demonstrating effective void-filling capacity.

After the first aging cycle (Figure 10b), multiple PET particles were identified in close proximity, associated with erosion of the cementitious matrix surrounding the polymer. Although the amount of C-S-H increased, the ITZ remained a critical point of fragility.

During the second cycle (Figure 10c), sample A15% showed reduced mechanical performance and revealed a higher concentration of PET particles with angular edges, which may have negatively affected structural cohesion. The ITZ remained evident, indicating persistent interfacial weaknesses.

The image after the third cycle (Figure 10d) showed advanced deterioration: increased porosity, isolated PET particles, and specimen disintegration after compression testing. The impossibility of extracting intact fragments prevented detailed analysis, indicating critical loss of structural cohesion.

The progressive degradation of ITZs, with evolving porosity and microcracking, explains the performance loss throughout the cycles. Although PET may initially improve certain properties, its microstructural stability is limited under cyclic aging conditions. Similar results were reported by Dębska (2024), who associated increased porosity with composite residues, highlighting the importance of constituent compatibility for long-term integrity.

The microstructural analysis was conducted via SEM on samples of the A15% formulation, selected based on its superior initial mechanical performance. The image of the unaged sample (Figure 10a) reveals a PET particle embedded in the cementitious matrix, bordered by an interfacial transition zone (ITZ) with pronounced porosity.

Visual inspection of samples

The samples were visually inspected with the naked eye at each stage of the aging process. Figure 11 illustrates the evolution of the specimens' appearance.

Figure 11
Visual inspection of samples throughout aging cycles. Unaged (a); first cycle (b); second cycle (c); and third cycle (d)

On initial condition (Figure 11a), the surfaces appeared clear, homogeneous, and compact, with low porosity, particularly in the A0% sample. Increasing PET content (A5% to A20%) resulted in higher porosity and surface heterogeneity, associated with weak polymer-cement matrix adhesion. After the first cycle (Figure 11b) slight surface erosion was observed, with increased PET exposure and partial pore disappearance, suggesting fine particle redistribution and possible formation of secondary hydration products. Sediment accumulation in the containers supported the hypothesis of mass loss due to mechanical wear.

At second cycle (Figure 11c) formulations with higher PET content showed intensified degradation, with microcracks, localized spalling, and structural deformations, especially in A15% and A20% samples. After the third cycle (Figure 11d), degradation reached critical levels - while surface loss stabilized, pronounced cracks appeared and some A20% specimens completely fragmented, indicating structural collapse. These effects were attributed to high porosity, weak interfacial transition zone cohesion, and thermally induced stresses. Figure 12 illustrates both crack formation (a) and complete fracture (b). These results match observations by Skibicki et al. (2022) and Parracha et al. (2024), confirming that higher PET content increases degradation susceptibility.

Figure 12
Crack formation (a) and complete fracture (b) of samples

Conclusions

The incorporation of recycled PET flakes as partial replacement for natural sand in cement-lime mortars demonstrated complex effects on the composite's physico-mechanical performance, particularly under accelerated thermal aging conditions. The results revealed that moderate PET contents (especially 10-15%) may initially enhance properties like water retention and compressive strength; however, this advantage becomes limited by progressive degradation induced by weathering cycles.

PET was found to alter the cementitious matrix's microstructure, increasing porosity and modifying the interfacial transition zone (ITZ), with direct consequences for vapor permeability, water absorption, and structural cohesion. These effects became more pronounced with extended aging cycles, particularly in formulations with high replacement ratios (15-20%). While delayed hydration reactions may temporarily mitigate degradation effects, prolonged exposure ultimately led to cracking, stiffness reduction, and in some cases, partial specimen collapse.

From a durability perspective, PET-modified mortars showed satisfactory short-term performance but require careful consideration for structural stability in environments with intense thermal and hygrometric variations. The data suggests a technical replacement limit of approximately 10-15%, beyond which structural integrity may be compromised. Progressive visual degradation and crack formation also highlight the need to consider aesthetic and surface aspects when evaluating the composite's service life.

These findings advance the use of polymeric waste in cementitious materials, providing relevant technical insights for developing sustainable mortars. Future studies should investigate the interplay between PET morphology, matrix composition, and different aging protocols to optimize mix design and improve long-term performance.

Declaração de Disponibilidade de Dados

Os dados de pesquisa estão disponíveis em repositório.

References

ABDULLAH, Q. M.; HAIDO, J. H. Response of hybrid concrete incorporating eco-friendly waste PET fiber: Experimental and analytical investigations. Construction and Building Materials, v. 354, p. 129071, 2022.
ALANI, A. H. et al Effect of the incorporation of PET fiber and ternary blended binder on the flexural and tensile behaviour of ultra-high performance green concrete. Construction and Building Materials, v. 331, p. 127306, 2022.
ALCIVAR-BASTIDAS, S. et al Effect of aging process on mechanical performance of reinforced mortar with NaOH abaca fibers. Case Studies in Construction Materials, v. 20, p. e03122, 2024.
ALMESHAL, I. et al Eco-friendly concrete containing recycled plastic as partial replacement for sand. Journal of Materials Research and Technology, v. 9, n. 3, p. 4631-4643, 2020.
AMERICAN SOCIETY FOR TESTING AND MATERIALS. C117-23: standard test method for materials finer than 75-μm (no. 200) sieve in mineral aggregates by washing. West Conshohocken, 2023.
AMERICAN SOCIETY FOR TESTING AND MATERIALS. C128-22: standard test method for relative density (specific gravity) and absorption of fine aggregate. West Conshohocken, 2022.
AMERICAN SOCIETY FOR TESTING AND MATERIALS. C136/C136M-19: standard test method for sieve analysis of fine and coarse aggregates. West Conshohocken, 2019.
AMERICAN SOCIETY FOR TESTING AND MATERIALS. C1602/C1602M-22: standard specification for mixing water used in the production of hydraulic cement concrete. West Conshohocken, 2022.
AMERICAN SOCIETY FOR TESTING AND MATERIALS. C207-24: standard specification for hydrated lime for masonry purposes. West Conshohocken, 2024.
AMERICAN SOCIETY FOR TESTING AND MATERIALS. C29/C29M-23: standard test method for bulk density (“unit weight”) and voids in aggregate. West Conshohocken, 2023.
AMERICAN SOCIETY FOR TESTING AND MATERIALS. C595-25: standard specification for blended hydraulic cements. West Conshohocken, 2025.
AMERICAN SOCIETY FOR TESTING AND MATERIALS. C597-22: standard test method for pulse velocity through concrete. West Conshohocken, 2022.
ASSOCIAÇÃO BRASILEIRA DA INDÚSTRIA DO PLÁSTICO. Perfil 2023: as indústrias de transformação e reciclagem de plástico no Brasil. São Paulo, 2023.
ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 13276: argamassa para assentamento e revestimento de paredes e tetos: determinação do índice de consistência. Rio de Janeiro, 2016.
ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 13279: argamassa para assentamento e revestimento de paredes e tetos: determinação da resistência à tração na flexão e à compressão. Rio de Janeiro, 2005b.
ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 15259: argamassa para assentamento de paredes de alvenaria: determinação da absorção de água. Rio de Janeiro, 2005a.
ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 15900-1: argamassa para assentamento e revestimento de paredes e tetos: parte 1: requisitos gerais. Rio de Janeiro, 2009.
ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 16541: argamassa industrializada para assentamento de paredes e revestimento de paredes e tetos. Rio de Janeiro, 2016.
ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 16697: cimento Portland: requisitos. Rio de Janeiro, 2018.
ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 7175: cal hidratada para argamassas. Rio de Janeiro, 2013.
BAMIGBOYE, G. O. et al Evaluation of eco-friendly concrete having waste PET as fine aggregates. Cleaner Materials, v. 2, p. 100026, 2021.
BELMOKADDEM, M. et al. Mechanical and physical properties and morphology of concrete containing plastic waste as aggregate. Construction and Building Materials, v. 257, p. 119559, 2020.
CAO, K. et al Binder mixture proportion optimization and durability of three-dimensional textile reinforced cementitious composites via thermodynamic modeling and experimental analysis. Construction and Building Materials, v. 436, p. 136883, 2024.
CHENG, S. et al Degradation progress of Portland cement mortar under the coupled effects of multiple corrosive ions and drying-wetting cycles. Cement and Concrete Composites, v. 111, p. 103629, 2020.
CHINCHILLAS-CHINCHILLAS, M. J. et al A new application of recycled-PET/PAN composite nanofibers to cement–based materials. Journal of Cleaner Production, v. 252, p. 119827, 2020.
DĘBSKA, B. et al Study of the influence of accelerated aging on the physical and mechanical properties of polymer composites containing rubber, polyethylene and poly (ethylene terephthalate) waste. Journal of Cleaner Production, v. 444, p. 141273, 2024.
EUROPEAN COMMITTEE FOR STANDARDIZATION. EN 1015-19: methods of test for mortar for masonry: part 19: determination of water vapour permeability of hardened rendering and plastering mortars. Brussels, 2000.
EUROPEAN COMMITTEE FOR STANDARDIZATION. EN 1015-8: methods of test for mortar for masonry: part 8: determination of water retention of fresh mortar by the substrate method. Brussels, 1999.
GAO, D. et al Effects of a novel hydrophobic admixture on the sulfate attack resistance of the mortar in the wet-dry cycling environment. Construction and Building Materials, v. 344, p. 128148, 2022.
GAO, Z. et al Shrinkage and creep characteristic of recycled plastic fiber reinforced sustainable self-compacting concrete with recycled concrete aggregates. Journal of Building Engineering, p. 112022, 2025.
GARCIA, M. et al. Performance of mortars with PET. Journal of Material Cycles and Waste Management, v. 23, n. 2, p. 699-706, 2021.
GEHLOT, M. R.; SHRIVASTAVA, S. Development of rendering mortar from granite cutting waste and impact of accelerated aging environment on its adhesive strength. Construction and Building Materials, v. 411, p. 134177, 2024.
GÓRAK, P. et al Lightweight PET based composite aggregates in Portland cement materials-Microstructure and physicochemical performance. Journal of Building Engineering, v. 34, p. 101882, 2021.
GOU, H. et al Durability development of lightweight and high-strength engineered cementitious composites subject to combined sulfate–chloride attack under freeze–thaw cycles. Construction and Building Materials, v. 408, p. 133659, 2023.
GOUVEIA, J. P. M. Análise ao comportamento de argamassas após aplicação nos suportes Coimbra, 2021. Dissertação (Mestrado em Engenharia Civil) – Universidade de Coimbra, Coimbra, 2021.
GRAVINA, R. J. et al HDPE and PET as aggregate replacement in concrete: life-cycle assessment, material development and a case study. Journal of Building Engineering, v. 44, p. 103329, 2021.
HAO, H. et al Enhancing compressive strength in cementitious composites via plasma-treated PET aggregates: Insights into interface mechanics. Cement and Concrete Composites, v. 149, p. 105529, 2024.
HUANG, G. et al Study on the deterioration mechanism and sulfate ion diffusion behavior in hybrid basalt-polypropylene fiber-reinforced concrete subjected to sulfate drying-wetting cycles. Journal of Building Engineering, v. 104, p. 112390, 2025.
JIANG, Z. et al Long-term shear performance of prestressed GFRP bars in accelerated seawater aging: Role of alkalinity reduction in concrete matrix. Construction and Building Materials, v. 463, p. 140039, 2025.
KANGAVAR, M. E. et al Development of sustainable concrete using recycled polyethylene terephthalate (PET) granules as fine aggregate. Developments in the Built Environment, v. 15, p. 100192, 2023.
KHAN, M. I. et al Effective use of recycled waste PET in cementitious grouts for developing sustainable semi-flexible pavement surfacing using artificial neural network (ANN). Journal of Cleaner Production, v. 340, p. 130840, 2022.
KOSIACHEVSKYI, D. et al Assessment of the hygrothermal, microstructural and chemical evolution of a hemp-based cementitious mortar under ETICS total weathering aging protocol. Construction and Building Materials, v. 314, p. 125471, 2022.
KŘÍŽOVÁ, K. et al Study of the behaviour of recycled and traditional fibres in cement composite at extreme temperatures. Journal of Building Engineering, v. 95, p. 110134, 2024.
KUMAR, M. et al Field based analysis of vegetation and climate impacts on the hydrological properties of urban vegetated slope. Scientific Reports, v. 15, n. 1, p. 7702, 2025.
KUNTHAWATWONG, R. et al Recycled Non-Biodegradable polyethylene terephthalate waste as fine aggregate in fly ash geopolymer and cement mortars. Construction and Building Materials, v. 328, p. 127084, 2022.
LEE, M. et al Mechanical characterization of recycled-PET fiber reinforced mortar composites treated with nano-SiO2 and mixed with seawater. Construction and Building Materials, v. 392, p. 131882, 2023.
LERNA, M. et al Effect of the chemical and mechanical recycling of PET on the thermal and mechanical response of mortars and premixed screeds. Materials, v. 16, n. 8, p. 3155, 2023.
LIN, X. et al Durability of biochar-cementitious composites incorporating crystalline admixture in chloride and sulphate environments. Construction and Building Materials, v. 458, p. 139554, 2025.
MAIA, J. et al Durability of a New Thermal Aerogel-Based Rendering System under Distinct Accelerated Aging Conditions. Materials, Basel, v. 14, n. 18, p. 5413, 2021.
MOHAMMED, A. A.; KARIM, S. H. Impact strength and mechanical properties of high strength concrete containing PET waste fiber. Journal of Building Engineering, v. 68, p. 106195, 2023.
MOHAMMED, A. A.; RAHIM, A. A. F. Experimental behavior and analysis of high strength concrete beams reinforced with PET waste fiber. Construction and Building Materials, v. 244, p. 118350, 2020.
MOUNA, Y. et al A statistical-experimental study to investigate the optimal parameters of fibres made from waste PET bottles for strengthening concrete. Construction and Building Materials, v. 420, p. 135613, 2024.
MUDI, C.; SHAW, A. Experimental investigation on durability of chemically treated natural fiber textile reinforced cementitious composite. Construction and Building Materials, v. 466, p. 140298, 2025.
NIU, Y. et al Effect of age and sulfate chloride environment on the Self-Healing performance of the desert sand engineered cementitious composite materials. Construction and Building Materials, v. 408, p. 133806, 2023.
NEVES JUNIOR, A. et al Effect of early age curing carbonation on the mechanical properties and durability of high initial strength Portland cement and lime-pozolan composites reinforced with long sisal fibres. Composites Part B: Engineering, v. 163, p. 351-362, 2019.
NOOR-E-KHUDA, S. Influence of wetting–drying cycles on compressive and flexural strength of cement mortar and CFRP-mortar bond strength. Construction and Building Materials, Amsterdam, v. 271, p. 121513, 2021.
OLIVEIRA, M. R. et al Mortar with pet: preliminary results. Energy Reports, v. 6, supl. 1, p. 800–803, 2020.
ORGANISATION FOR ECONOMIC CO-OPERATION AND DEVELOPMENT. Global plastics outlook: economic drivers, environmental impacts and policy options. Paris, 2022.
PACHLA, E. C. et al Durable lightweight cementitious composites incorporating rice husk: Accelerated aging studies with acidic and basic solutions. Journal of Building Engineering, v. 95, p. 110057, 2024.
PARRACHA, J. L. et al Effects of hygrothermal and natural aging on the durability of multilayer insulation systems incorporating thermal mortars with EPS and aerogel. Cement and Concrete Composites, v. 148, p. 105483, 2024.
PATRICIO, S. M. R. Incorporação de PET triturado em substituição parcial ao agregado miúdo para utilização em argamassas Campina Grande, 2021. 137 f. Tese (Doutorado em Engenharia de Processos) - Universidade Federal de Campina Grande, Campina Grande, 2021.
RESENDE, D. M. et al Coating mortars produced with recycled PET aggregates: a technical, environmental, and socioeconomic approach applied to Brazilian social housing. Journal of Building Engineering, v. 83, p. 108426, 2024.
SADROLODABAEE, P. et al Effect of accelerated aging and silica fume addition on the mechanical and microstructural properties of hybrid textile waste-flax fabric-reinforced cement composites. Cement and Concrete Composites, v. 135, p. 104829, 2023.
SAINZ-AJA, J. et al Aging of recycled aggregates mortars by drying-wetting cycles. Construction and Building Materials, v. 307, p. 124934, 2021.
SANTOS, H. C. et al Effects of ethylene glycol and nano-CaCO₃ on carbonation and self-healing potential of aging Portland cement mortars. Journal of Building Engineering, v. 104, p. 112391, 2025.
SHAIKH, F. U. A. Tensile and flexural behaviour of recycled polyethylene terephthalate (PET) fibre reinforced geopolymer composites. Construction and Building Materials, v. 245, p. 118438, 2020.
SILVA, A. M. da; BRITO, J. de; VEIGA, R. Incorporation of fine plastic aggregates in rendering mortars. Construction and Building Materials, v. 71, p. 226-236, 2014.
SKIBICKI, S. et al The effect of using recycled PET aggregates on mechanical and durability properties of 3D printed mortar. Construction and Building Materials, v. 335, p. 127443, 2022.
SONG, H. et al Evaluation of zirconia modification on the durability of natural fiber-reinforced cement composites using accelerated aging. Journal of Building Engineering, v. 84, p. 108632, 2024.
SPÓSITO, F. A. et al Incorporation of PET wastes in rendering mortars based on Portland cement/hydrated lime. Journal of Building Engineering, v. 32, p. 101506, 2020.
STAPPER, J. L.; GAUVIN, F.; BROUWERS, H. J. H. Influence of short-term degradation on coir in natural fibre-cement composites. Construction and Building Materials, v. 306, p. 124906, 2021.
SU, J. et al Experimental investigation on fracture behavior of high-ductility cementitious composites with recycled PET fine aggregate. Construction and Building Materials, v. 470, p. 140464, 2025.
TANG, R. et al Preparation and performance analysis of recycled PET fiber reinforced recycled foamed concrete. Journal of Building Engineering, v. 57, p. 104948, 2022.
TAYEH, B. A. et al Performance of sustainable concrete containing different types of recycled plastic. Journal of Cleaner Production, v. 328, p. 129517, 2021.
THOMAS, C. et al Effect of high temperature and accelerated aging in high density micro-concrete. Construction and Building Materials, v. 272, p. 121920, 2021.
UNITED NATIONS ENVIRONMENT PROGRAMME; UNITED NATIONS HUMAN SETTLEMENTS PROGRAMME. 2021 Global Status Report for Buildings and Construction Nairóbi, 2021.
UNITED NATIONS. Sustainable Development Goal (SGD) 11: Sustainable Cities: Make cities and human settlements inclusive, safe, resilient and sustainable. New York: United Nations, 2015a.
UNITED NATIONS. Sustainable Development Goal (SGD) 12: Responsible Consumption: Ensure sustainable consumption and production patterns. New York: United Nations, 2015b.
WANG, W. et al Comparative study on the durability of ultra-high toughness cementitious composites and mortar under salt attacks. Journal of Cleaner Production, v. 494, p. 144844, 2025.
WATTANAVICHIEN, P.; IWANAMI, M. Investigation of the mechanical, microstructure, and durability properties of concrete with fine uniform and non-uniform polyethylene terephthalate (PET) aggregates. Cleaner Materials, v. 13, p. 100267, 2024.
WEI, J. et al Correlation between hydration of cement and durability of natural fiber-reinforced cement composites. Corrosion Science, v. 106, p. 1-15, 2016.
XIONG, H. et al Pore structure, adsorption, and water absorption of expanded perlite mortar in external thermal insulation composite system during aging. Cement and Concrete Composites, v. 116, p. 103900, 2021.
YANG, R. et al Microstructural insight into the deterioration mechanism of the mortar subject to the combined action of external sulfate attack and cyclic wetting–drying. Construction and Building Materials, v. 317, p. 125484, 2022.
ZENG, J. et al Durability assessment of PEN/PET FRP composites based on accelerated aging in alkaline solution/seawater with different temperatures. Construction and Building Materials, v. 327, p. 126992, 2022.
ZENG, J. et al Stress-strain behavior of polyethylene terephthalate fiber-reinforced polymer-confined normal-, high-and ultra high-strength concrete. Journal of Building Engineering, v. 30, p. 101243, 2020.
ZERIG, T. et al Combined sand eco-mortar reinforced with polyethylene Terephthalate: Behavior and optimization using RSM method. Construction and Building Materials, v. 404, p. 133160, 2023.
ZHAO, S. et al Experimental study of the durability of high-performance cementitious composites with amorphous metallic fibers. Construction and Building Materials, v. 367, p. 130295, 2023.

Edited by

Editores:
Marcelo Henrique Farias de Mederios e Eduardo Pereira

Publication Dates

Publication in this collection
20 Oct 2025
Date of issue
2025

History

Received
05 July 2025
Accepted
18 Aug 2025

This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

[1] ABDULLAH, Q. M.; HAIDO, J. H. Response of hybrid concrete incorporating eco-friendly waste PET fiber: Experimental and analytical investigations. Construction and Building Materials, v. 354, p. 129071, 2022.

[2] ALANI, A. H. et al Effect of the incorporation of PET fiber and ternary blended binder on the flexural and tensile behaviour of ultra-high performance green concrete. Construction and Building Materials, v. 331, p. 127306, 2022.

[3] ALCIVAR-BASTIDAS, S. et al Effect of aging process on mechanical performance of reinforced mortar with NaOH abaca fibers. Case Studies in Construction Materials, v. 20, p. e03122, 2024.

[4] ALMESHAL, I. et al Eco-friendly concrete containing recycled plastic as partial replacement for sand. Journal of Materials Research and Technology, v. 9, n. 3, p. 4631-4643, 2020.

[5] AMERICAN SOCIETY FOR TESTING AND MATERIALS. C117-23: standard test method for materials finer than 75-μm (no. 200) sieve in mineral aggregates by washing. West Conshohocken, 2023.

[6] AMERICAN SOCIETY FOR TESTING AND MATERIALS. C128-22: standard test method for relative density (specific gravity) and absorption of fine aggregate. West Conshohocken, 2022.

[7] AMERICAN SOCIETY FOR TESTING AND MATERIALS. C136/C136M-19: standard test method for sieve analysis of fine and coarse aggregates. West Conshohocken, 2019.

[8] AMERICAN SOCIETY FOR TESTING AND MATERIALS. C1602/C1602M-22: standard specification for mixing water used in the production of hydraulic cement concrete. West Conshohocken, 2022.

[9] AMERICAN SOCIETY FOR TESTING AND MATERIALS. C207-24: standard specification for hydrated lime for masonry purposes. West Conshohocken, 2024.

[10] AMERICAN SOCIETY FOR TESTING AND MATERIALS. C29/C29M-23: standard test method for bulk density (“unit weight”) and voids in aggregate. West Conshohocken, 2023.

[11] AMERICAN SOCIETY FOR TESTING AND MATERIALS. C595-25: standard specification for blended hydraulic cements. West Conshohocken, 2025.

[12] AMERICAN SOCIETY FOR TESTING AND MATERIALS. C597-22: standard test method for pulse velocity through concrete. West Conshohocken, 2022.

[13] ASSOCIAÇÃO BRASILEIRA DA INDÚSTRIA DO PLÁSTICO. Perfil 2023: as indústrias de transformação e reciclagem de plástico no Brasil. São Paulo, 2023.

[14] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 13276: argamassa para assentamento e revestimento de paredes e tetos: determinação do índice de consistência. Rio de Janeiro, 2016.

[15] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 13279: argamassa para assentamento e revestimento de paredes e tetos: determinação da resistência à tração na flexão e à compressão. Rio de Janeiro, 2005b.

[16] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 15259: argamassa para assentamento de paredes de alvenaria: determinação da absorção de água. Rio de Janeiro, 2005a.

[17] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 15900-1: argamassa para assentamento e revestimento de paredes e tetos: parte 1: requisitos gerais. Rio de Janeiro, 2009.

[18] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 16541: argamassa industrializada para assentamento de paredes e revestimento de paredes e tetos. Rio de Janeiro, 2016.

[19] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 16697: cimento Portland: requisitos. Rio de Janeiro, 2018.

[20] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 7175: cal hidratada para argamassas. Rio de Janeiro, 2013.

[21] BAMIGBOYE, G. O. et al Evaluation of eco-friendly concrete having waste PET as fine aggregates. Cleaner Materials, v. 2, p. 100026, 2021.

[22] BELMOKADDEM, M. et al. Mechanical and physical properties and morphology of concrete containing plastic waste as aggregate. Construction and Building Materials, v. 257, p. 119559, 2020.

[23] CAO, K. et al Binder mixture proportion optimization and durability of three-dimensional textile reinforced cementitious composites via thermodynamic modeling and experimental analysis. Construction and Building Materials, v. 436, p. 136883, 2024.

[24] CHENG, S. et al Degradation progress of Portland cement mortar under the coupled effects of multiple corrosive ions and drying-wetting cycles. Cement and Concrete Composites, v. 111, p. 103629, 2020.

[25] CHINCHILLAS-CHINCHILLAS, M. J. et al A new application of recycled-PET/PAN composite nanofibers to cement–based materials. Journal of Cleaner Production, v. 252, p. 119827, 2020.

[26] DĘBSKA, B. et al Study of the influence of accelerated aging on the physical and mechanical properties of polymer composites containing rubber, polyethylene and poly (ethylene terephthalate) waste. Journal of Cleaner Production, v. 444, p. 141273, 2024.

[27] EUROPEAN COMMITTEE FOR STANDARDIZATION. EN 1015-19: methods of test for mortar for masonry: part 19: determination of water vapour permeability of hardened rendering and plastering mortars. Brussels, 2000.

[28] EUROPEAN COMMITTEE FOR STANDARDIZATION. EN 1015-8: methods of test for mortar for masonry: part 8: determination of water retention of fresh mortar by the substrate method. Brussels, 1999.

[29] GAO, D. et al Effects of a novel hydrophobic admixture on the sulfate attack resistance of the mortar in the wet-dry cycling environment. Construction and Building Materials, v. 344, p. 128148, 2022.

[30] GAO, Z. et al Shrinkage and creep characteristic of recycled plastic fiber reinforced sustainable self-compacting concrete with recycled concrete aggregates. Journal of Building Engineering, p. 112022, 2025.

[31] GARCIA, M. et al. Performance of mortars with PET. Journal of Material Cycles and Waste Management, v. 23, n. 2, p. 699-706, 2021.

[32] GEHLOT, M. R.; SHRIVASTAVA, S. Development of rendering mortar from granite cutting waste and impact of accelerated aging environment on its adhesive strength. Construction and Building Materials, v. 411, p. 134177, 2024.

[33] GÓRAK, P. et al Lightweight PET based composite aggregates in Portland cement materials-Microstructure and physicochemical performance. Journal of Building Engineering, v. 34, p. 101882, 2021.

[34] GOU, H. et al Durability development of lightweight and high-strength engineered cementitious composites subject to combined sulfate–chloride attack under freeze–thaw cycles. Construction and Building Materials, v. 408, p. 133659, 2023.

[35] GOUVEIA, J. P. M. Análise ao comportamento de argamassas após aplicação nos suportes Coimbra, 2021. Dissertação (Mestrado em Engenharia Civil) – Universidade de Coimbra, Coimbra, 2021.

[36] GRAVINA, R. J. et al HDPE and PET as aggregate replacement in concrete: life-cycle assessment, material development and a case study. Journal of Building Engineering, v. 44, p. 103329, 2021.

[37] HAO, H. et al Enhancing compressive strength in cementitious composites via plasma-treated PET aggregates: Insights into interface mechanics. Cement and Concrete Composites, v. 149, p. 105529, 2024.

[38] HUANG, G. et al Study on the deterioration mechanism and sulfate ion diffusion behavior in hybrid basalt-polypropylene fiber-reinforced concrete subjected to sulfate drying-wetting cycles. Journal of Building Engineering, v. 104, p. 112390, 2025.

[39] JIANG, Z. et al Long-term shear performance of prestressed GFRP bars in accelerated seawater aging: Role of alkalinity reduction in concrete matrix. Construction and Building Materials, v. 463, p. 140039, 2025.

[40] KANGAVAR, M. E. et al Development of sustainable concrete using recycled polyethylene terephthalate (PET) granules as fine aggregate. Developments in the Built Environment, v. 15, p. 100192, 2023.

[41] KHAN, M. I. et al Effective use of recycled waste PET in cementitious grouts for developing sustainable semi-flexible pavement surfacing using artificial neural network (ANN). Journal of Cleaner Production, v. 340, p. 130840, 2022.

[42] KOSIACHEVSKYI, D. et al Assessment of the hygrothermal, microstructural and chemical evolution of a hemp-based cementitious mortar under ETICS total weathering aging protocol. Construction and Building Materials, v. 314, p. 125471, 2022.

[43] KŘÍŽOVÁ, K. et al Study of the behaviour of recycled and traditional fibres in cement composite at extreme temperatures. Journal of Building Engineering, v. 95, p. 110134, 2024.

[44] KUMAR, M. et al Field based analysis of vegetation and climate impacts on the hydrological properties of urban vegetated slope. Scientific Reports, v. 15, n. 1, p. 7702, 2025.

[45] KUNTHAWATWONG, R. et al Recycled Non-Biodegradable polyethylene terephthalate waste as fine aggregate in fly ash geopolymer and cement mortars. Construction and Building Materials, v. 328, p. 127084, 2022.

[46] LEE, M. et al Mechanical characterization of recycled-PET fiber reinforced mortar composites treated with nano-SiO2 and mixed with seawater. Construction and Building Materials, v. 392, p. 131882, 2023.

[47] LERNA, M. et al Effect of the chemical and mechanical recycling of PET on the thermal and mechanical response of mortars and premixed screeds. Materials, v. 16, n. 8, p. 3155, 2023.

[48] LIN, X. et al Durability of biochar-cementitious composites incorporating crystalline admixture in chloride and sulphate environments. Construction and Building Materials, v. 458, p. 139554, 2025.

[49] MAIA, J. et al Durability of a New Thermal Aerogel-Based Rendering System under Distinct Accelerated Aging Conditions. Materials, Basel, v. 14, n. 18, p. 5413, 2021.

[50] MOHAMMED, A. A.; KARIM, S. H. Impact strength and mechanical properties of high strength concrete containing PET waste fiber. Journal of Building Engineering, v. 68, p. 106195, 2023.

[51] MOHAMMED, A. A.; RAHIM, A. A. F. Experimental behavior and analysis of high strength concrete beams reinforced with PET waste fiber. Construction and Building Materials, v. 244, p. 118350, 2020.

[52] MOUNA, Y. et al A statistical-experimental study to investigate the optimal parameters of fibres made from waste PET bottles for strengthening concrete. Construction and Building Materials, v. 420, p. 135613, 2024.

[53] MUDI, C.; SHAW, A. Experimental investigation on durability of chemically treated natural fiber textile reinforced cementitious composite. Construction and Building Materials, v. 466, p. 140298, 2025.

[54] NIU, Y. et al Effect of age and sulfate chloride environment on the Self-Healing performance of the desert sand engineered cementitious composite materials. Construction and Building Materials, v. 408, p. 133806, 2023.

[55] NEVES JUNIOR, A. et al Effect of early age curing carbonation on the mechanical properties and durability of high initial strength Portland cement and lime-pozolan composites reinforced with long sisal fibres. Composites Part B: Engineering, v. 163, p. 351-362, 2019.

[56] NOOR-E-KHUDA, S. Influence of wetting–drying cycles on compressive and flexural strength of cement mortar and CFRP-mortar bond strength. Construction and Building Materials, Amsterdam, v. 271, p. 121513, 2021.

[57] OLIVEIRA, M. R. et al Mortar with pet: preliminary results. Energy Reports, v. 6, supl. 1, p. 800–803, 2020.

[58] ORGANISATION FOR ECONOMIC CO-OPERATION AND DEVELOPMENT. Global plastics outlook: economic drivers, environmental impacts and policy options. Paris, 2022.

[59] PACHLA, E. C. et al Durable lightweight cementitious composites incorporating rice husk: Accelerated aging studies with acidic and basic solutions. Journal of Building Engineering, v. 95, p. 110057, 2024.

[60] PARRACHA, J. L. et al Effects of hygrothermal and natural aging on the durability of multilayer insulation systems incorporating thermal mortars with EPS and aerogel. Cement and Concrete Composites, v. 148, p. 105483, 2024.

[61] PATRICIO, S. M. R. Incorporação de PET triturado em substituição parcial ao agregado miúdo para utilização em argamassas Campina Grande, 2021. 137 f. Tese (Doutorado em Engenharia de Processos) - Universidade Federal de Campina Grande, Campina Grande, 2021.

[62] RESENDE, D. M. et al Coating mortars produced with recycled PET aggregates: a technical, environmental, and socioeconomic approach applied to Brazilian social housing. Journal of Building Engineering, v. 83, p. 108426, 2024.

[63] SADROLODABAEE, P. et al Effect of accelerated aging and silica fume addition on the mechanical and microstructural properties of hybrid textile waste-flax fabric-reinforced cement composites. Cement and Concrete Composites, v. 135, p. 104829, 2023.

[64] SAINZ-AJA, J. et al Aging of recycled aggregates mortars by drying-wetting cycles. Construction and Building Materials, v. 307, p. 124934, 2021.

[65] SANTOS, H. C. et al Effects of ethylene glycol and nano-CaCO₃ on carbonation and self-healing potential of aging Portland cement mortars. Journal of Building Engineering, v. 104, p. 112391, 2025.

[66] SHAIKH, F. U. A. Tensile and flexural behaviour of recycled polyethylene terephthalate (PET) fibre reinforced geopolymer composites. Construction and Building Materials, v. 245, p. 118438, 2020.

[67] SILVA, A. M. da; BRITO, J. de; VEIGA, R. Incorporation of fine plastic aggregates in rendering mortars. Construction and Building Materials, v. 71, p. 226-236, 2014.

[68] SKIBICKI, S. et al The effect of using recycled PET aggregates on mechanical and durability properties of 3D printed mortar. Construction and Building Materials, v. 335, p. 127443, 2022.

[69] SONG, H. et al Evaluation of zirconia modification on the durability of natural fiber-reinforced cement composites using accelerated aging. Journal of Building Engineering, v. 84, p. 108632, 2024.

[70] SPÓSITO, F. A. et al Incorporation of PET wastes in rendering mortars based on Portland cement/hydrated lime. Journal of Building Engineering, v. 32, p. 101506, 2020.

[71] STAPPER, J. L.; GAUVIN, F.; BROUWERS, H. J. H. Influence of short-term degradation on coir in natural fibre-cement composites. Construction and Building Materials, v. 306, p. 124906, 2021.

[72] SU, J. et al Experimental investigation on fracture behavior of high-ductility cementitious composites with recycled PET fine aggregate. Construction and Building Materials, v. 470, p. 140464, 2025.

[73] TANG, R. et al Preparation and performance analysis of recycled PET fiber reinforced recycled foamed concrete. Journal of Building Engineering, v. 57, p. 104948, 2022.

[74] TAYEH, B. A. et al Performance of sustainable concrete containing different types of recycled plastic. Journal of Cleaner Production, v. 328, p. 129517, 2021.

[75] THOMAS, C. et al Effect of high temperature and accelerated aging in high density micro-concrete. Construction and Building Materials, v. 272, p. 121920, 2021.

[76] UNITED NATIONS ENVIRONMENT PROGRAMME; UNITED NATIONS HUMAN SETTLEMENTS PROGRAMME. 2021 Global Status Report for Buildings and Construction Nairóbi, 2021.

[77] UNITED NATIONS. Sustainable Development Goal (SGD) 11: Sustainable Cities: Make cities and human settlements inclusive, safe, resilient and sustainable. New York: United Nations, 2015a.

[78] UNITED NATIONS. Sustainable Development Goal (SGD) 12: Responsible Consumption: Ensure sustainable consumption and production patterns. New York: United Nations, 2015b.

[79] WANG, W. et al Comparative study on the durability of ultra-high toughness cementitious composites and mortar under salt attacks. Journal of Cleaner Production, v. 494, p. 144844, 2025.

[80] WATTANAVICHIEN, P.; IWANAMI, M. Investigation of the mechanical, microstructure, and durability properties of concrete with fine uniform and non-uniform polyethylene terephthalate (PET) aggregates. Cleaner Materials, v. 13, p. 100267, 2024.

[81] WEI, J. et al Correlation between hydration of cement and durability of natural fiber-reinforced cement composites. Corrosion Science, v. 106, p. 1-15, 2016.

[82] XIONG, H. et al Pore structure, adsorption, and water absorption of expanded perlite mortar in external thermal insulation composite system during aging. Cement and Concrete Composites, v. 116, p. 103900, 2021.

[83] YANG, R. et al Microstructural insight into the deterioration mechanism of the mortar subject to the combined action of external sulfate attack and cyclic wetting–drying. Construction and Building Materials, v. 317, p. 125484, 2022.

[84] ZENG, J. et al Durability assessment of PEN/PET FRP composites based on accelerated aging in alkaline solution/seawater with different temperatures. Construction and Building Materials, v. 327, p. 126992, 2022.

[85] ZENG, J. et al Stress-strain behavior of polyethylene terephthalate fiber-reinforced polymer-confined normal-, high-and ultra high-strength concrete. Journal of Building Engineering, v. 30, p. 101243, 2020.

[86] ZERIG, T. et al Combined sand eco-mortar reinforced with polyethylene Terephthalate: Behavior and optimization using RSM method. Construction and Building Materials, v. 404, p. 133160, 2023.

[87] ZHAO, S. et al Experimental study of the durability of high-performance cementitious composites with amorphous metallic fibers. Construction and Building Materials, v. 367, p. 130295, 2023.

Material	NS	PET	Standards
Specific gravity (g/cm³)	2.64	1.35	C128 (ASTM, 2022)
Bulk density (kg/m³)	1710	430	C29 (ASTM, 2023)
Water absorption (%)	0.45	0.10	C128 (ASTM, 2022)
Fineness modulus	1.36	3.79	C136 (ASTM, 2019)
Maximum size (mm)	0.60	2.36	NBR NM 248 (ABNT, 2003)
Pulverulent material (%)	0.39	-	C117 (ASTM, 2023)

Mortar	Cement	Hydrated Lime	NS	PET	Water	∑
A₀	180.80	155.49	1,386.73	–	348.08	2,071.10
A₅	180.80	155.49	1,334.99	26.66	348.08	2,046.00
A₁₀	180.80	155.49	1,279.94	54.93	348.08	2,019.20
A₁₅	180.80	155.49	1,221.47	85.24	348.08	1,990.90
A₂₀	180.80	155.49	1,159.03	117.21	348.08	1,945.30