Sustainable cementitious mortars produced with polymer waste from synthesis reactor cleaning

ABSTRACT

The transition toward a circular economy has encouraged the construction sector to adopt more sustainable material solutions. In this context, the reuse of industrial polymeric waste in cementitious mortars represents a promising approach that combines environmental and economic benefits by reducing waste incineration and preserving virgin raw materials. This study investigated the feasibility of partially replacing fine aggregates with white water sludge, a byproduct obtained after flocculation and filtration through a filter press during the washing of polymer resin reactors. The polymeric waste was dehydrated, granulated, and characterized to reproduce the particle size distribution of a reference medium sand. High-strength mortars were produced with volumetric sand replacement levels of 5, 10, 15, and 20 vol.%. Consistency and setting time (Vicat) tests were performed in the fresh state. After 28 days of curing, the specimens were evaluated in terms of microstructure using scanning electron microscopy, density, water absorption, compressive strength, and thermoacoustic behavior. The incorporation of polymeric waste caused a gradual reduction in density, indicating potential for lightweight composites. Although compressive strength decreased with increasing replacement, values remained suitable for non-structural applications, including cladding panels and sealing blocks. Functionally, waste addition improved sound attenuation and thermal insulation. This confirms practical feasibility.

Keywords:
Polymeric waste; Circular economy; Cementitious mortars; Thermal and acoustic performance

1. INTRODUCTION

Climate change and rising global temperatures, both capable of triggering severe environmental and socioeconomic disruptions, have prompted governments and industries to adopt strategies aimed at reducing the environmental impacts associated with economic production [¹, ²]. In this context of escalating global challenges, the traditional linear economic model, based on the extraction of primary resources and characterized by short product life cycles [³], has increasingly revealed structural limitations. This has accelerated the transition toward the circular economy paradigm, which seeks to maintain the value of resources within integrated production chains for as long as possible. By emphasizing efficiency in resource use, particularly through the valorization of urban and industrial waste, the circular economy aims to achieve a more balanced relationship between economic growth, environmental preservation, and social well-being [⁴, ⁵].

Solid waste management is a central concern within this transition. In Brazil, this agenda was first formalized by Law No. 11,445/2007 [⁶] and later consolidated by Law No. 12,305/2010 [⁷], which established the National Solid Waste Policy (NSWP) [⁸]. The NSWP assigns shared responsibility for waste management, tasking the private sector with properly handling the waste it generates and reintegrating it into production cycles, thus promoting innovation and value recovery [⁹]. The central principle of the NSWP is to reduce the volume of materials destined for final disposal, adding value to the waste [¹⁰]. However, truly effective reuse depends on technological innovations capable of extending the useful life of materials [¹¹]. Plastics exemplify this challenge: they constitute a significant portion of solid waste (approximately 8 wt% and 20 vol.%) and are highly resistant to natural degradation [¹², ¹³].

Recent studies [¹⁴,¹⁵,¹⁶] show that, despite Brazil having relevant regulatory frameworks—such as the National Solid Waste Policy and the National Solid Waste Plan—key targets, including the elimination of open dumps and significant progress in recycling by 2024, have not been met. This highlights the need for greater technological investment, strengthened municipal capacities, and increased economic cooperation among government, businesses, and society to accelerate the transition to a circular economy.

The discussion on waste utilization gains relevance when considering the still limited performance of recycling in Brazil. In 2023, the annual study by the Plastic Transforms Movement/MaxiQuim reported an overall mechanical recycling rate for post-consumer plastics of ~20.6% and recovery of plastic packaging of ~28.6% [¹⁷]. In 2024, there was a slight recovery: the industry recorded ~21% recycling for post-consumer plastics and ~24.4% for packaging, after the contraction in 2023, in a scenario pressured by the prices of virgin resins [¹⁸]. Additionally, sectoral reports highlight that 1.4 million tons of plastics were sent for recycling in 2023, but bottlenecks in collection and sorting—including low productivity and limited participation of cooperatives—continue to restrict the potential for circularity in the country [¹⁹].

The environmental impacts of human activities are a constant concern. Therefore, researchers seek to develop new materials. To move forward, it is important to improve techniques for reusing alternative materials in order to reduce the environmental impacts associated with them [²⁰].

The construction sector plays a strategic role in this context, being the second-largest consumer of polymers worldwide. These materials have increasingly replaced traditional components such as steel and concrete due to their favorable technical characteristics [¹³], including low density (0.9 g/cm³–2.3 g/cm³) [²¹], low thermal conductivity [²²], and the ability to absorb and dissipate sound waves [²³].

Simultaneously, the polymer synthesis industry generates substantial volumes of waste each month, primarily originating from the cleaning of resin reactors [²⁴]. Latex, paints and coating production commonly rely on emulsion polymerization, a heterogeneous polymerization process conducted in aqueous media [²⁴, ²⁵]. This process involves monomers such as n-butyl acrylate, methyl methacrylate, along with additives containing carboxylic acids that contribute to colloidal stability [²⁶, ²⁷]. Following polymerization, reactor cleaning produces wastewater known as “white water”, which requires treatment with flocculants and coagulants. Subsequent solid-liquid separation generates white water sludge (solid waste), a polymer-rich waste typically destined for incineration [²⁸, ²⁹], resulting in high operational costs and avoidable energy losses.

The reuse of this polymeric waste as a partial substitute for fine aggregates in cementitious mortars emerges as a viable strategy to enhance sustainability in both industries [³⁰,³¹,³²]. Incorporating such waste can improve thermoacoustic performance by reducing thermal conductivity and attenuating sound transmission [³³], while simultaneously mitigating waste generation and virgin resource consumption.

Regarding the use of waste in materials, Souza, as cited by KURZ et al. [³³], points out that products containing recycled material must meet the service requirements to which they will be subjected and comply with ABNT standards, while maintaining functionality for both the user and the construction industry.

In this context, the present work aims to develop cementitious mortars incorporating polymeric waste from the resin synthesis industry. Fine aggregates were partially replaced with dehydrated and granulated polymeric particles of comparable granulometry, with the goal of improving thermal and acoustic insulation while advancing circular economy principles. The research encompasses white water characterization, preparation of the polymer aggregate, the formulation of high-strength mortars (1:0.5:4.0) containing 5, 10, 15, and 20 vol.% replacements, and subsequent evaluation of mechanical behavior, microstructural morphology, and thermal and acoustic performance.

2. MATERIALS AND METHODS

2.1. Materials

White water sludge obtained after flocculation and filtration through a filter press, produced during the washing of polymer resin reactors, was kindly provided by Dow Chemical Company (Jacareí/SP). The binders and aggregates used in this study included CP-II E 32-RS Portland cement (TUPI), commercial medium washed sand (Areião ABC), and hydrated lime CH-III (ITAÚ).

All materials were purchased from local construction suppliers and used within the validity period recommended by manufacturers.

2.2. Methods

2.2.1. White water characterization

Because the industrial process involves different formulations, the chemical composition of white water may vary slightly depending on the product synthesized on the collection day. To monitor these variations, residual monomer content was analyzed daily over eleven days using an Agilent 8890 gas chromatograph. Samples were prepared by dissolving a 1:1 aliquot of white water in a 250-ppm CPMK (cyclopropyl methyl ketone) aqueous solution used as an internal standard.

A headspace sampling technique was employed, with vial temperature of 130 °C, a loop temperature of 170 °C, and a transfer-line temperature of 190 °C. The vial equilibration time was 10 minutes, and the total analysis cycle was 28 minutes. The injector temperature was maintained at 225 °C, and the oven temperature increased at a rate of 40 °C/min until reaching 230 °C. Compounds were separated in the chromatographic column and quantified using a flame ionization detector (FID).

2.2.2. Characterization and preparation of aggregates

Particle size distribution is a key parameter for quality control in mortars and concretes and is defined by the NBR 7211 (ABNT) [³⁰], which specifies the requirements for fine aggregates.

The reference aggregate used in the study was medium commercial sand. Its particle size distribution was determined using a standard sieve sequence with 1 kg of sand and the following mesh apertures: 4.75 mm, 2.36 mm, 1.18 mm, 0.6 mm, 0.3 mm, and 0.15 mm.

In parallel, the polymeric waste (white water sludge) was processed for use as an alternative aggregate. After initial solid-liquid separation, the sludge was dried at 50 ºC for 24 h. The dried material was then ground using a high-speed industrial blender (Skymsen, 900W) and subjected to an additional 24 h drying cycle. The same sieve set used for sand characterization was employed to classify the polymeric particles into the corresponding size fractions. This procedure enables reconstruction of particle size distribution matching that of the reference sand.

The final preparation step involved reconstituting the polymeric aggregate according to the particle size distribution of the medium sand, using volumetric proportions adjusted for the density of each fraction.

2.2.3. Preparation of the mortar and fabrication of the test specimens

Mortars were prepared using a strong mix (1:0.5:4.0) with volumetric replacements of sand by polymeric waste at 5, 10, 15, and 20 vol.%. Material dosage was carefully controlled, with aggregate replacement conducted strictly on a volumetric basis.

Workability control was essential to isolate the effect of the polymeric waste on fresh-state properties. Water content was adjusted for each mix to achieve a consistent slump value of approximately 150 mm, following ABNT guidelines. The corresponding mix parameters are presented in Table 1.

Table 1
Mortar preparation and aggregate proportions by volume.

COMPOSITION	CEMENT PORTLAND CP II	HYDRATED LIME CH III	MEDIUM SAND CHARACTERIZED	CHARACTERIZED WASTE	WATER/CEMENT RATIO
Reference (0%)	1	0.5	4.0	0	1.40
Waste (5%)	1	0.5	3.8	0.2	1.44
Waste (10%)	1	0.5	3.6	0.4	1.48
Waste (15%)	1	0.5	3.4	0.6	1.52
Waste (20%)	1	0.5	3.2	0.8	1.56

Cylindrical test specimens were molded with dimensions of 5 × 10 cm (diameter x height) for axial compression characterization and 5 × 2 cm for water absorption tests, while a plate-shaped specimen measuring 15 × 15 × 2 cm (base × base × height) was used for thermal and acoustic evaluations. All specimens were prepared and cured in a water-saturated atmosphere for 28 days. After curing, the top and bottom surfaces were ground and planned to adjust thickness and ensure surface flatness, minimizing variations in results.

2.2.4. Determination of compressive strength

Compressive strength tests were performed using an EMIC universal testing machine (model GR048) equipped with a 100 kN load cell and operated at a displacement rate of 10 mm/min. The procedure followed NBR 7215 standard [³⁴], and a minimum of five specimens were tested for each composition.

2.2.5. Determination of apparent density, water absorption, porosity and void ratio

Apparent density and water absorption were determined in accordance with ABNT NBR 9778 [³⁵]. Prior to testing, specimens were oven-dried at 105 °C to ensure complete removal of moisture. Apparent density was calculated as the ratio between dry mass and the geometric volume of the specimen.

Water absorption was measured by first determining the dry mass (m_s) and subsequently immersing the specimens in water at 23 ± 2 °C for 72h. During saturation, the specimens were suspended such that one-third of their height was submerged during the first 4h, two-thirds during the following 4h, and fully immersed for the remaining 64h. Specimens were weighed after 24, 48, and 72h of immersion to obtain the saturated mass (m_sat). Before weighing, excess surface water was gently removed using a slightly damp cloth.

2.2.6. Evaluation of thermal insulation

A thermal insulation evaluation system was developed, consisting of two chambers constructed with EPS walls and internal dimensions of 62.5 × 42.5 × 37.5 cm. The closed system containing chambers A and B, of equal volume, has the test specimen positioned between them. This configuration aims to simulate solar radiation (Chamber A – controlled isothermal environment) and the temperature response in an internal environment (Chamber B), as illustrated in Figure 1.

Figure 1
Schematic representation of the device developed to evaluate the thermal insulation performance.

In chamber A (control/simulated external environment), conditions represent an outdoor setting exposed to intense solar radiation. A 250W infrared lamp was used as a heat source, maintaining the air temperature, monitored by an ambient temperature sensor (T1), at an isothermal condition of 43 °C during the first 8h of testing, simulating a period of direct sunlight.

In chamber B (test/simulated internal environment), conditions represent the interior of the building, where the effectiveness of the insulation is evaluated. Two temperature sensors were used: an infrared sensor (T2) positioned to measure the inner surface of the specimen (cold side), and an ambient temperature sensor (T3) placed inside the chamber to monitor the air temperature. Thermal monitoring focused primarily on the response temperatures in Chamber B. Sensor T2 determines the temperature directly on the test specimens, measuring the temperature of the inner face (cold side) of the sample, which would be facing the interior environment of the building. The rate at which temperature T2 increases during heating and decreases during cooling, relative to T1, indicates how quickly heat passes through the material. A sample with better thermal insulation will have a slower increase response in T2. Sensor T3 measures the air temperature inside Chamber B, simulating the internal thermal comfort of the house, and is the ultimate indicator of insulation performance. In addition, the combination of T2 and T3 readings in Chamber B is essential to correlate the thermal effusivity properties of the surface.

Each specimen was performed over a 16h cycle consisting of a heating phase (0-8h) and a cooling phase (8–16h). The delay in peak temperature during heating provides insight into the thermal inertia of the material. During cooling, the lowest temperature reached by T3 after 8h indicates the sample’s ability to retain heat under the test conditions, thereby characterizing thermal performance.

2.2.7. Sound insulation evaluation

The acoustic insulation performance of the mortar samples was evaluated using a laboratory apparatus specifically designed to measure sound attenuation through the test specimens under controlled conditions. The device consists of two distinct environments separated by samples with the same dimensions as those used in the thermal insulation assessments, as illustrated in Figure 2. In Environment A (open external/noise generation), sound was produced using a loudspeaker connected to a signal-generator software capable of emitting sinusoidal waves at controlled frequencies. Tests were performed at four frequencies: 50 Hz, 400 Hz, 2,000 kHz, and 10,500 kHz.

In Environment B (closed internal/transmitted-noise capture), representing the interior of a building, the noise transmitted through the specimen was measured. The chamber is acoustically insulated to ensure that the primary transmission path is through the test sample itself. This configuration enables accurate assessment of the attenuation capacity of each material, as illustrated in Figure 2.

Figure 2
Schematic representation of the device developed to evaluate acoustic insulation performance.

The measurement of sound attenuation (acoustic insulation) was performed using two calibrated microphones (sound level meters), with results expressed in A-weighted decibels (dBA). Microphone IS-1 (external sound intensity) was positioned in Environment A, 10 cm from the noise source and 40 cm from the test specimen, measuring the incident sound intensity (side A). This reference establishes the baseline noise level at each test frequency. Microphone IS-2 (internal sound intensity) was placed in Environment B, 10 cm from the surface of the test specimen, measuring the transmitted sound intensity (side B) after sound propagation through the mortar sample. The acoustic insulation performance of each sample was quantified by its Sound Reduction Power (R), defined as the difference between the incident and transmitted sound intensities:

$$\text{R}=\text{Side}\text{A}-\text{Side}\text{B}\left(\text{dBA}\right)$$

A higher R value indicates superior acoustic insulation, meaning that the mortar specimen effectively reduces the transmitted sound pressure level. The comparison of R across the different test frequencies provides insight into the influence of polymeric waste incorporation on frequency-dependent sound insulation performance.

3. RESULTS

3.1. White water characterization

Table 2 presents the average concentration of residual monomers in white water.

Table 2
Measurement of the average concentration of residual monomers in white water.

MONOMERS	CONCENTRATION (PPM)
Methyl methacrylate	19 ± 16
n-butyl acrylate	30 ± 26
Ethyl acrylate	13 ± 9
Styrene	7 ± 6
2-Ethylhexyl acrylate	2 ± 1

3.2. Morphological characterization of polymeric waste and mortar after curing

Figure 3 shows the SEM images of the polymeric waste (A and B, with different magnification) and revealing particles with irregular shapes, rough surfaces and the presence of microcracks and pores resulting from the flocculation and mechanical pressing system. This structure favors water retention and mechanical interaction with the components of the cementitious matrix. Figures 3 (C and D) shows SEM images of the composition with 20% of polymeric waste, and it is possible to observe the cementitious mortar with the inserted debris and some cracks, possibly due to the debris/cement interaction. Figures 3E and F show the surface of the cementitious mortar (0 % of polymeric waste) after curing, and it is possible to observe hydrated calcium silicate (C-S-H) and the large hexagonal plates of Portlandite.

Figure 3
SEM images of (A) and (B) polymeric waste, (C) and (D) composition 20% waste, (E) and (F) reference test specimen (0%).

3.3. Compressive strength determination

Figure 4 shows the curves of the axial compressive strength tests for all compositions.

Figure 4
Compression behavior of cementitious mortar containing increasing polymer aggregate contents: (A)typical axial compression stress-strain curves, (B) maximum compressive stress, (C) compression modulus, (D) deformation.

Table 3 presents the results for maximum specification stress, optimization modulus, and deformation of the compositions.

Table 3
Maximum stress variation, modulus of variation and deformation for cementitious mortars.

COMPOSITION	MAXIMUM COMPRESSIVE STRESS (MPA)	COMPRESSION MODULUS (MPA)	DEFORMATION (%)
Reference (0%)	9.7 ± 1.2	932 ± 113	1.4 ± 0.2
Waste (5%)	5.5 ± 0.4	548 ± 49	1.6 ± 0.1
Waste (10%)	4.1 ± 0.2	500 ± 26	1.6 ± 0.1
Waste (15%)	3.0 ± 0.2	125 ± 11	1.4 ± 0.1
Waste (20%)	2.6 ± 0.3	60 ± 6	2.0 ± 0.2

3.4. Apparent density, water absorption, void ratio, and porosity

Figure 5 shows the results for water absorption, density of the specimens developed with different polymeric waste levels, void ratio, and porosity.

Figure 5
Behavior of cementitious mortar containing increasing polymer aggregate contents: (A) Water absorption curves, (B) density, (C) void ratio, (D) porosity.

3.5. Determination of thermal insulation

The determination of thermal insulation was carried out by fixing the isothermal temperature in the control chamber (T1 (A)) at 43 ºC for all samples, for a period of 8h, subsequently turning off the heat source and monitoring the temperatures on the surface of the specimen and in the environment of chamber B (T2 and T3, respectively), using reference specimens and specimens with different polymer exclusion contents. Figure 6 shows the temperature versus time curves at T1 (A), T2 (B) and T3 (C).

Figure 6
Results of thermal insulation tests: (A) T1 measurement in chamber A, (B) T2 measurement on the test sample in chamber B, (C) T3 measurement in the indoor environment of chamber B.

Table 4 presents the values obtained in the thermal insulation tests.

Table 4
Data obtained from thermal insulation tests on cementitious mortar containing polymeric waste.

COMPOSITION	TEMPERATURE PEAK (8H)	FINAL TEMPERATURE (16H)
Reference (0%)	31 ºC	21 ºC
Waste (5%)	29 ºC	20 ºC
Waste (10%)	29 ºC	20 ºC
Waste (15%)	28 ºC	20 ºC
Waste (20%)	30 ºC	21 ºC

3.6. Acoustic insulation determination

Figure 7 shows the difference in sound intensity for the compositions created, at different frequencies, each value representing the mean and standard deviation of ten specificities.

Figure 7
Resulting difference in sound intensity for the compositions studied at different frequencies.

4. DISCUSSION

Table 2 shows that residual monomer concentrations in the acrylic wastewater remained consistently low throughout the monitoring period, with values never exceeding 56 ppm. These levels lie well within the acceptable range for the reference acrylic dispersions used in the industrial process, which typically contain up to 3% solids. Despite the expectation of low monomer content, daily monitoring was essential because deviations in polymerization performance, reactor washing conditions, or formulation changes could yield atypical monomer peaks. Maintaining monomer concentrations within controlled limits is critical not only for industrial quality but also for environmental and occupational safety, given the toxicological implications associated with unreacted acrylates [³⁶].

Direct disposal of white water to sewage systems is problematic due to its significant organic load. The effluent contains acrylic acid, methacrylic acid, acetic acid, and polymeric chains such as poly (acrylic acid) (PAA), all of which contribute to high chemical oxygen demand (COD). Moreover, many of these compounds exhibit pH-dependent swelling or partial solubility, which can disrupt activated sludge systems and hinder bio-degradation processes [³⁷]. Therefore, valorizing this material by incorporating it into cementitious composites offers both environmental and economic benefits.

A principal concern when incorporating polymeric waste into mortars is the potential long-term release of unreacted monomers during curing or service life. The analytical results obtained here mitigate this concern: monomer concentrations remained below 50 ppm, significantly lower than the 100 ppm threshold established by ANVISA RDC nº 56/2012 for materials with direct food contact [³⁸]. This suggests that polymeric waste is chemically stable and unlikely to release harmful volatiles, supporting its adoption as a sustainable alternative fine aggregate. Comparable concentrations have been reported for acrylic and vinyl paint wastes reused in construction materials, reinforcing the environmental safety of this approach [³⁹].

SEM analysis provided insights into how polymeric waste alters the mortar microstructure and performance. The waste particles (Figure 3A–B) exhibit irregular geometry, cracked surfaces, and a heterogeneous pore network resulting from flocculation followed by mechanical dewatering in a filter press. These morphological features increase water retention capacity and interact with the cementitious matrix by promoting both mechanical interlock and higher porosity. Even after granulometric correction to mirror the particle size distribution of natural sand, the intrinsic porosity of the waste increased water demand, consistent with the hydrophilic and hygroscopic characteristics of polyacrylates [⁴⁰]. This effect explains the need for additional mixing water to maintain workability (Table 1), which has downstream impacts on mechanical strength and durability.

As shown in Figure 3C, polymer waste exhibit limited chemical affinity with the hydrophilic cement paste, consistent with literature describing reduced adhesion between organic polymers and mineral binders [⁴¹]. This results in weak interfaces where microcracks initiate under applied stress. Figure 3D further illustrates fractured spherical waste, likely due to mismatches in shrinkage kinetics between the polymer and cement hydration products, an effect widely discussed by SCRIVENER et al. [⁴²]. Additionally, the agglomeration of polymeric particles, observed in several regions, contributes to heterogeneity, increases voids, and adversely affects hydration uniformity—all factors known to reduce compressive strength and increase water absorption [⁴³].

Figures 3 E and F confirm the presence of typical hydration products such as calcium hydroxide (portlandite) plates and fibrous C–S–H gel, responsible for mechanical development in Portland cement-based materials. However, the composite mortars containing polymeric waste exhibited distinct mechanical behaviors. The control specimen presented conventional brittle failure with compressive strength of 9.7 ± 1.2 MPa, while increasing waste content systematically reduced strength (5–20% replacement). This behavior can be attributed to increased porosity, reduced ITZ quality, and disrupted hydration in regions surrounding polymer clusters [⁴⁴, ⁴⁵]. Despite the reduction in maximum compressive strength, waste-containing mortars demonstrated enhanced deformability and ductility. This behavior aligns with observations for polymer-modified mortars, in which polymer particles absorb fracture energy and slow crack propagation by bridging microstructural flaws [⁴⁶].

Figure 4 shows that the reference mortar (0%) reaches the highest compressive strength (9.7 ± 1.2 MPa), with a typical brittle response characterized by an abrupt post-peak stress drop at ~1.4% strain—consistent with unmodified cementitious materials [⁴⁰]. All mortars incorporating polymeric waste exhibited a progressive reduction in peak stress as the replacement level increased, confirming that the waste weakens the load-bearing capacity of the matrix under the tested conditions.

Despite the reduction in maximum strength, waste-modified mortars displayed substantially higher deformation at failure, indicating increased toughness. This behavior reflects the ability of polymeric particles to absorb fracture energy and delay microcrack propagation, a well-reported phenomenon in polymer-modified cementitious systems [⁴⁴]. Thus, although mechanically weaker, the modified mortars exhibit greater ductility—an attribute desirable in applications where energy absorption, impact resistance or controlled deformation are advantageous.

The decline in compressive strength and stiffness stems primarily from microstructural alterations introduced by the waste. Unlike mineral aggregates, polymer particles bond poorly to the cementitious matrix and may interfere with hydration, generating weak interfacial zones and localized porosity that hinder the formation of load-carrying hydration products [⁴³]. These effects explain the consistent drop in strength as waste content increases.

The modulus also decreased with increasing waste content, but with more variability than the compressive strength. This non-linearity reflects the sensitivity of stiffness to internal heterogeneity. Polymer agglomeration, variable particle–matrix adhesion, and discontinuities produced during hydration lead to nonuniform stress distribution, which makes the modulus more susceptible to fluctuations even when the trend in strength remains consistent. In addition, the polymeric phase can act as a compliant inclusion that increases deformability without proportionally affecting final strength under monotonic loading [⁴³, ⁴⁷].

Overall, the mechanical results show that polymer waste incorporation systematically reduces strength and stiffness—limiting structural applications—but simultaneously enhances deformability and toughness. Joint analysis of compressive strength and modulus clarifies the performance boundaries of these composites and supports their suitability for non-structural, sustainability-driven applications where reduced density, higher energy absorption, and improved functional properties compensate for the mechanical trade-offs [⁴⁸].

This reduction can be attributed to the quantity and size of the waste particles, since according to Andrade [⁴⁹], the smaller the particle size, the greater the interaction between these particles and the matrix, increasing resistance and hardness, making it difficult for defects to move in the material.

Density decreased proportionally with waste incorporation, confirming the formulation of a lightweight mortar. In the context of ABNT NBR 13281:2016 [⁵⁰], such mortars are suitable for non-structural applications, particularly where reduced weight and enhanced thermal/acoustic performance are advantageous [⁴⁸]. The density reduction correlates strongly with increased water absorption (Figure 5), driven by polymer swelling during mixing followed by shrinkage during curing, which leaves a network of interconnected pores. The formation of such pores reduces durability by facilitating water ingress and weakens mechanical performance, consistent with previous findings in polymer-filled composites [⁵¹, ⁵²]. The combination of density, porosity, and mechanical performance highlights 15% waste replacement as the optimal condition, beyond which performance deteriorates substantially (e.g., at 20%).

Figure 6A shows the results of the thermal insulation tests. After the 16h heating–cooling cycle, the reference mortar (0% waste) reached the lowest final temperature (18.8 °C), indicating the fastest heat loss. The mortars with polymeric waste cooled more slowly, showing that the waste improves heat retention. After 8h of cooling from 43 °C, these samples ended up as much as 2.2 °C warmer than the reference, demonstrating better insulation capacity.

This improvement is due to the waste low thermal conductivity and its ability to increase porosity in the mortar. The trapped air inside the pores acts as an efficient thermal barrier, reducing the thermal conductivity (λ) and thermal diffusivity (α) of the material [⁵³,⁵⁴,⁵⁵]. Because diffusivity controls how fast heat spreads during temperature changes, lower α means slower heating and cooling, and therefore greater thermal inertia [⁵⁶, ⁵⁷]. The lower thermal effusivity (E) of the modified mortars also reduces the rate of heat exchange at the surface, helping keep the internal temperature more stable [⁵⁸].

The inner-surface temperatures (Figure 6C) reinforce this behavior. When the external face was kept at 43 °C, the reference mortar reached an internal peak of about 31 °C, while mortars with waste reached around 29 °C. A 2 °C difference is significant for thermal comfort and energy consumption in buildings. During cooling, the reference mortar dropped 17.5 °C, while waste-modified mortars dropped about 15 °C, confirming their higher thermal inertia. Among the mixtures, 15% waste performed best during heating (lowest peak), while 20% waste showed the highest heat retention during cooling (smallest ΔT).

The acoustic results show that adding polymeric waste—and therefore increasing porosity—improves sound absorption, especially at high frequencies. Porous structures dissipate sound energy as the waves travel through the voids, reducing what is transmitted to the other side.

Sound insulation was evaluated by the Sound Reduction Index (R), calculated as the difference between the sound levels on the emitting and receiving sides. As expected, at low and medium frequencies (50–2,000 Hz), the modified mortars did not show large improvements compared to the reference mix, because insulation at these frequencies depends mainly on mass. Since the waste replaces dense sand with a lighter material, the surface density decreases, limiting performance according to the Law of Mass [⁵⁹,⁶⁰,⁶¹].

At high frequencies (10,500 kHz), however, the performance improved substantially. The reference mortar (32.8% porosity) provided 23 dBA of attenuation, while the 15% waste mortar (46.7% porosity) achieved 36 dBA, reducing the transmitted sound by about 95%. The 20% waste mix (52.9% porosity) also performed very well (90% reduction), although slightly below the 15% mix. This indicates an optimal waste content: if too much polymer is added, particle agglomeration may interfere with the pore network and reduce efficiency [⁶², ⁶³].

The improvement is explained by two mechanisms: porous absorption (high-frequency waves enter the pores and lose energy through friction with the internal surfaces) and viscoelastic damping (polymer chains convert part of the sound vibration into heat) [⁶⁴].

These results show that polymeric waste enhances both thermal and acoustic performance, with the best balance observed at 15 vol%.

5. CONCLUSIONS

The results demonstrate a clear performance trade-off: while the incorporation of polymeric waste reduces mechanical strength, it simultaneously provides substantial functional gains, particularly in thermal insulation, acoustic attenuation, and material lightning.

The mechanical characterization showed a progressive reduction in compressive strength as the waste content increased, with the reference (0%) achieving the highest stress (9.5 MPa). This reduction is attributed to the weak interfacial bonding between the hydrophobic polymer and the hydrophilic cementitious matrix. Nonetheless, the modified mortars exhibited increased deformability and toughness, desirable in non-structural applications where flexibility and impact resilience are important, such as wall coatings, interior rendering, and ceiling mortars. Thus, although mass resistance decreases, performance diversification improves.

Improvements in functional properties were directly associated with increased porosity and reduced density. Thermal testing confirmed that polymeric waste acts as an efficient insulating agent, reducing thermal diffusivity and enhancing heat retention. The 15% waste composition demonstrated the most favorable balance, reducing the internal peak temperature by approximately 2 °C compared with the reference sample under controlled test conditions. This highlights the material’s potential for improving thermal comfort and contributing to energy savings in buildings.

Acoustic performance also benefited from waste incorporation, particularly at 10.5 kHz. The 15% waste mix achieved the highest performance, with 36 dBA of sound reduction and an effective 95% decrease in transmitted sound intensity relative to the reference sample.

Overall, the findings validate the feasibility of using polymeric waste as a partial replacement for fine aggregates in mortars intended for non-structural applications. The modified composites combine reduced density with enhanced thermo-acoustic properties, offering functional advantages for building envelopes and interior finishing layers. Beyond technical benefits, this approach contributes directly to circular economy strategies by valorizing an industrial by-product typically destined for incineration, reducing environmental impacts, and decreasing the demand for natural sand extraction.

6. ACKNOWLEDGEMENTS

The authors are grateful to FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo, process 2024/11092-8) and CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico, process 307933/2021-0) for financial support. The author thanks Dow Chemical Company for providing the polymer waste.

7. BIBLIOGRAPHY

• ^[1] HORNEG, D., BHADA-TATA, P., KENNEDY, C., “A produção de resíduos deve atingir o pico neste século”, Nature, v. 502, pp. 615–617, 2013.
• ^[2] MINGHUA, Z., XIUMIN, F., ROVETTA, A., et al., “Municipal solid waste management in Pudong New Area, China”, Waste Management, v. 29, n. 3, pp. 1227–1233, 2008. doi: https://doi.org/10.1016/j.wasman.2008.07.016. PubMed PMID: 18951780.
  » https://doi.org/10.1016/j.wasman.2008.07.016
• ^[3] SANCHEZ, J.V.M., IZQUIERDO, M. E. F., MARTÍNEZ, G. L., et al., Economia circular: fundamentos e aplicações, 1 ed., Cizur Menor, Aranzadi, 2021.
• ^[4] WEBSTER, K., The circular economy: a wealth of flows, 2 ed., Cowes, Ellen MacArthur Foundation Publishing, 2015.
• ^[5] HERRERO, L.M.G., LAGUELA, E.P., Economia circular: Espiral, Madrid, Ecobook, 2019.
• ^[6] BRASIL, “Lei nº 11.445, de 5 de janeiro de 2007. Estabelece diretrizes nacionais para o saneamento básico”, Diário Oficial da União, Brasília, DF, 8 jan. 2007.
• ^[7] BRASIL, “Lei nº 12.305, de 2 de agosto de 2010. Institui a Política Nacional de Resíduos Sólidos”, Diário Oficial da União, Brasília, DF, 3 ago. 2010.
• ^[8] SOARES, C.S., Plano de gerenciamento de resíduos sólidos – PGRS, Enap, Brasília, 2016.
• ^[9] CENTRO ESTADUAL DE VIGILÂNCIA EM SAÚDE, www.cevs.rs.gov.br, accessed in November, 2024.
  » www.cevs.rs.gov.br
• ^[10] FARIA, C.R.S.M., A Política nacional de resíduos sólidos, Senado Federal, Brasília, 2010.
• ^[11] OLIVEIRA, A.C.V., SILVA, A.D.S., MOREIRA, I.T.A., “Economia circular: conceitos e contribuições na gestão de resíduos urbanos”, Revista de Desenvolvimento Econômico, v. 3, n. 44, 2019.
• ^[12] MILANI, K.C., “Avaliação de argamassas cimentícias especiais com adição de fibras poliméricas eletrofiadas de PET e PVB”, Tese de M.Sc., Universidade Tecnológica Federal do Paraná, Toledo, Paraná, 2020.
• ^[13] HIPOLITO, I., HIPOLITO, R.S., LOPES, G.A., “Polímeros da Construção Civil”, In: Simpósio de Excelência em Gestão e Tecnologia – SEGeT, Resende, RJ, 23–25 Outubro 2013.
• ^[14] INTERNATIONAL TRADE ADMINISTRATION, Brazil waste management, https://www.trade.gov/market-intelligence/brazil-waste-management, accessed in January, 2025.
  » https://www.trade.gov/market-intelligence/brazil-waste-management
• ^[15] AGÊNCIA BRASIL, Política nacional de resíduos sólidos completa 13 anos, https://www.abrema.org.br/2024/03/04/politica-nacional-de-residuos-solidos-completa-13-anos/, accessed in January, 2026.
  » https://www.abrema.org.br/2024/03/04/politica-nacional-de-residuos-solidos-completa-13-anos/
• ^[16] CIRCLE ECONOMY FOUNDATION, Circularity gap report 2024, Amsterdam, Circle Economy, 2024, https://www.circularity-gap.world/2024, accessed in January, 2026.
  » https://www.circularity-gap.world/2024
• ^[17] MOVIMENTO PLÁSTICO TRANSFORMA, Panorama da reciclagem de plásticos no Brasil: avanços e desafios em 2023, https://www.plasticotransforma.com.br/materia-detalhe/panorama-de-reciclagem-de-plasticos-no-brasil-avancos-e-desafios-em-2023, accessed in January, 2026.
  » https://www.plasticotransforma.com.br/materia-detalhe/panorama-de-reciclagem-de-plasticos-no-brasil-avancos-e-desafios-em-2023
• ^[18] INDÚSTRIA NEWS, Brasil acelera na reciclagem de plásticos pós-consumo, https://www.industrianews.com.br/2025/09/brasil-acelera-na-reciclagem-de-plasticos-pos-consumo/, accessed in January, 2026.
  » https://www.industrianews.com.br/2025/09/brasil-acelera-na-reciclagem-de-plasticos-pos-consumo/
• ^[19] EXAME, 1,4 milhão de toneladas de plástico foram encaminhadas para reciclagem em 2023, apesar de desafios, https://exame.com/esg/14-milhao-de-toneladas-de-plastico-foram-recicladas-em-2023-apesar-de-desafios-na-cadeia/, accessed in January, 2026.
  » https://exame.com/esg/14-milhao-de-toneladas-de-plastico-foram-recicladas-em-2023-apesar-de-desafios-na-cadeia/
• ^[20] BEZERRA, I.M.T., “Cinza da casca do arroz utilizada em argamassas de assentamento e revestimento”, Tese de M.Sc., Universidade Federal de Campina Grande, Campina Grande, Paraíba, 2010.
• ^[21] PASSATORE, C., Química dos polímeros, São Paulo, Centro Paula Souza, 2013.
• ^[22] MANO, E.B., Polímeros como materiais de engenharia, São Paulo, Edgard Blücher, 2000.
• ^[23] RECENA, F.A.P., Conhecendo argamassa, 2 ed., Porto Alegre, EdiPUCRS, 2012.
• ^[24] SZIGETHY, S.A., Resíduos sólidos urbanos no Brasil: desafios tecnológicos, políticos e econômicos, www.ipea.gov.br, accessed in November, 2024.
  » www.ipea.gov.br
• ^[25] CUNHA MS, Propriedades de polímeros e de adesivos sensíveis à pressão de base aquosa, São Paulo, H.B. Fuller, 2018.
• ^[26] CANEVAROLO JUNIOR, S.V., Ciência dos polímeros, 2 ed., São Paulo, Artliber, 2006.
• ^[27] LOVELL, P.A., EL-AASER, M.S., Emulsion polymerization and emulsion polymers, West Sussex, John Wiley & Sons, 1999.
• ^[28] ZUBITUR, M., ASUA, J.M., “Factors affecting kinetics and coagulum formation during the emulsion copolymerization of styrene/butyl acrylate”, Polymer, v. 42, n. 14, pp. 5979–5985, 2001. doi: https://doi.org/10.1016/S0032-3861(01)00039-8.
  » https://doi.org/10.1016/S0032-3861(01)00039-8
• ^[29] AGUIAR, V.R.C., SILVA JUNIOR, M.G., UCKER, F.E., et al., “Levantamento dos resíduos gerados em uma indústria de tintas”, Revista Uniaraguaia, v. 13, n. 3, pp. 67–88, 2020.
• ^[30] RODRIGUES, F.P., “Estudo da viabilidade da incorporação de politereftalato de etila – PET reciclado em massa cimentícia”, Revista Científica UMC – Edição Especial PIBIC, v. 3, n. 3, 2018.
• ^[31] OLIVEIRA, L.S., “Reaproveitamento de resíduo de poliestireno expandido em compósitos cimentícios”, Tese de M.Sc., Universidade Federal de São João Del-Rei, São João Del Rei, Minas Gerais, 2013.
• ^[32] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICA, ABNT NBR 7211: Agregados para concreto – Especificação, Rio de Janeiro, ABNT, 2005.
• ^[33] KURZ, M.N., BRANDELLI, T.M., PALIGA, C.M., et al., “A potencialidade do uso de resíduo de borracha de pneu em argamassa: análise das propriedades físicas e mecânicas”, Matéria, v. 23, n. 3, pp. e12154, 2018.
• ^[34] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS, ABNT NBR 7215: Cimento Portland — Determinação da resistência à compressão, Rio de Janeiro, ABNT, 2019.
• ^[35] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. ABNT NBR 9778: Argamassa e concreto endurecidos — Determinação da absorção de água, índice de vazios e massa específica, Rio de Janeiro, ABNT, 2005.
• ^[36] MATTAR, R., VIANA, R.V., “Utilização de resíduos poliméricos da indústria de reciclagem de plástico em blocos de concreto”, Revista Eletrônica em Gestão, Educação e Tecnologia Ambiental, v. 8, n. 8, pp. 1722–1733, 2012.
• ^[37] MATERIAL PROPERTIES, Ácido poliacrílico: fórmula, propriedades e aplicação, www.material-properties.org, accessed in November, 2025.
  » www.material-properties.org
• ^[38] BRASIL, “Resolução - RDC nº 56, de 16 de novembro de 2012”, Diário Oficial da União, p. 66, Nov. 2012.
• ^[39] SITIVESP, Manual de gerenciamento de resíduos para a indústria de tintas e vernizes, São Paulo, SITIVESP, 2010.
• ^[40] MANZANO, M.A.R., TRALDI, C.L., SILVA, E.F., et al, “Mecanismo de atuação dos polímeros superabsorventes na hidratação de materiais cimentícios”, In: Congresso Brasileiro do Concreto – CBC, Natal, 7–10 Outubro 2014.
• ^[41] SILVA, R.A., OLIVEIRA, L.A., COSTA, M.R., “Efeitos da adição de polímeros reciclados em argamassas: análise microestrutural e desempenho mecânico”, Matéria, v. 25, n. 3, pp. 1–12, 2020.
• ^[42] SCRIVENER, K., SNELLINGS, R., LOTHENBACH, B., A practical guide to microstructural analysis of cementitious materials, Boca Raton, CRC Press, 2018. doi: https://doi.org/10.1201/b19074.
  » https://doi.org/10.1201/b19074
• ^[43] SILVA, D.A., AGOPYAN, V., “Utilização de resíduos industriais na produção de materiais cimentícios”, Revista Ambiente Construído, v. 7, n. 2, pp. 47–58, 2007.
• ^[44] SOARES NETO, G.A., MENDES, E.L.S., “Análise do comportamento mecânico da argamassa com materiais poliméricos”, In: Congresso Técnico Científico da Engenharia e da Agronomia – CONTECC, Maceió, 16-17 Setembro 2021.
• ^[45] OURIQUE, M.A., “Avaliação do uso de materiais poliméricos na composição do concreto”, Tese de B.Sc, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, 2021.
• ^[46] HELENE, P., TERZIAN, P., Materiais de construção civil e princípios de ciência e engenharia dos materiais, São Paulo, PINI, 1992.
• ^[47] MEHTA, P.K., MONTEIRO, P.J.M., Concreto: microestrutura, propriedades e materiais, 2 ed., São Paulo, IBRACON, 2014.
• ^[48] JOHN, V.M., ZORDAN, S.E., Materiais reciclados na construção civil, São Paulo, PINI, 2001.
• ^[49] ANDRADE, C., MYNRINE, V., SILVA, D.A., et al., “Compósito para a construção civil a partir de resíduos industriais”, Matéria, v. 21, n. 2, pp. 321–329, 2016. doi: https://doi.org/10.1590/S1517-707620160002.0031.
  » https://doi.org/10.1590/S1517-707620160002.0031
• ^[50] ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICA, ABNT NBR 13281: Argamassa para assentamento e revestimento de paredes e tetos – Requisitos, Rio de Janeiro, ABNT, 2016.
• ^[51] SOUZA, A.T., “Análise comparativa de propriedades mecânicas e de durabilidade de argamassas de revestimento mistas e aditivadas”, Tese de M.Sc. Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, 2019.
• ^[52] MEDEIROS, M.C., “Avaliação de métodos para determinação de índices de vazios máximo e mínimo de materiais granulares”, Tese de B.Sc, Universidade Federal do Rio de Janeiro, Rio de Janeiro, 2018.
• ^[53] LAMBERTS, R., DUTRA, L., PEREIRA, L.O.R., Eficiência Energética na Arquitetura, 4 ed., Rio de Janeiro, Eletrobras/Procel, 2014.
• ^[54] SANTOS, W.N.D., GREGÓRIO, F.R., MUMMERY, P., et al., “Propriedades térmicas de polímeros por métodos transientes de troca de calor”, Polímeros, v. 13, n. 4, pp. 265–269, 2003. doi: https://doi.org/10.1590/S0104-14282003000400011.
  » https://doi.org/10.1590/S0104-14282003000400011
• ^[55] RIBEIRO, B.B., NASCIMENTO, A.S., SOUZA, R.B., “Desempenho térmico de argamassas com resíduos de borracha”, In: Congresso Brasileiro de Cerâmica, Águas de Lindóia, 7-10 Dezembro 2020.
• ^[56] NASTA, A.P., “Uma contribuição para o design do conforto: avaliação da difusividade térmica de blocos cerâmicos e de concreto”, Tese de M.Sc., Universidade Federal do Paraná, Curitiba, Paraná, 2015.
• ^[57] CONZÁLES CRUZ, G.A., “Estudio experimental de las propriedades termofísicas de materiales de construccion”, Tese de D.Sc., Universidade Politécnica de Catalunha, Barcelona, 2003.
• ^[58] VAN DER KOLK, P.R., “Thermal effusivity of building materials: measurement and analysis”, M.Sc. Thesis, Delft University of Technology, Delft, Netherlands, 2011.
• ^[59] BISTAFA, S.R., Acústica aplicada ao controle do ruído, São Paulo, Edgard Blücher, 2011.
• ^[60] GERGES, S.N.Y., Ruído: fundamentos e controle, 2 ed., Florianópolis, Autor, 2000.
• ^[61] SOUTO, A., Acústica: o que é e quais as suas fórmulas (com exercícios), https://www.todamateria.com.br/acustica/, accessed in October, 2025.
  » https://www.todamateria.com.br/acustica/
• ^[62] SCHAFER, R.M., A afinação do mundo: uma exploração pioneira pela história passada e pelo presente do ambiente sonoro, São Paulo, UNESP, 2001.
• ^[63] HAWLITSCHEK, F.H., “Caracterização das propriedades de agregados miúdos reciclados e a influência no comportamento reológico de argamassas”, Tese de M.Sc., Universidade de São Paulo, São Paulo, São Paulo, 2015.
• ^[64] CASSU, S.N., FELISBERTI, M.I., “Comportamento dinâmico-mecânico e relaxações em polímeros e blendas poliméricas”, Química Nova, v. 27, n. 4, pp. 583–596, 2004.

Publication Dates

• Publication in this collection
  10 Apr 2026
• Date of issue
  2026

History

• Received
  21 Nov 2025
• Accepted
  27 Feb 2026