Incorporation of dregs and grits wastes in mortars: evaluation of mechanical performance and durability

Incorporação de resíduos de dregs e grits em argamassa: avaliação de desempenho mecânico e durabilidade

Abstract

Accelerated population growth, coupled with high consumption of natural resources, requires research focused on waste utilization. Solid waste from the pulp mill, originating from the Kraft process, is generated in large quantities and, despite its potential, still lacks an adequate destination. This paper investigates the mechanical properties and durability of coating mortars with the addition (7.5% and 15%) of the dregs and grits wastes, comparing them to a reference mix. The results indicate that the incorporation of dregs into the cementitious matrix offers advantages over both the reference and the grits waste. The use of dregs shows better mechanical performance and an alkali-silica reaction expansion equivalent to the reference for the 15% addition. However, the 7.5% addition of dregs results in the highest expansion among all the mortars studied. Both residues exhibit an expansion behavior inversely proportional to the addition rate of the wastes. With the addition of grits, all mortars show characteristics similar to the reference. Thus, the study identifies the potential for reusing both residues.

Keywords
Dregs; Grits; Mortar; Alkali-silica reaction

Resumo

O crescimento populacional acelerado em conjunto com o alto consumo de recursos naturais demandam pesquisas voltadas à utilização de resíduos. Os resíduos sólidos da indústria de celulose, provenientes do processo Kraft, possuem uma grande geração e até o momento, apesar de seu potencial, não possuem uma destinação adequada. Dessa forma, o artigo desenvolve um estudo acerca da análise de propriedades mecânicas e de durabilidade de argamassas de revestimento com a adição (7.5% e 15%) dos resíduos dregs e grits, comparando-as com uma mistura de referência. Os resultados indicam que o resíduo dregs incorporado à matriz cimentícia apresenta vantagens tanto em relação à referência quanto ao resíduo grits. O uso do dregs mostra melhores resultados para o desempenho mecânico e uma expansão por reação álcali-sílica equivalente à referência para o teor de 15% de adição. Contudo, quando utilizado o teor de 7.5% de dregs observa-se a maior expansão dentre todas as argamassas estudadas. Em ambos os resíduos se verifica um comportamento de expansão inversamente proporcional ao teor de adição dos resíduos. Com a adição de grits, verifica-se que todas as argamassas possuem características semelhantes em relação à referência. Sendo assim, identifica-se potencial de reaproveitamento de ambos os resíduos no âmbito do estudo.

Palavras-chave
Dregs; Grits; Argamassa; Reação álcali-sílica

Introduction

According to estimates by the United Nations, the number of inhabitants on the planet should reach 10.4 billion by 2080 (UN, 2023). This population growth will encourage the consumption of natural resources and, consequently, the generation of waste. Based on these premises, Law n° 12.305 was instituted in Brazil on August 2, 2010, which infers the National Solid Waste Policy (Brazil, 2010).

To achieve sustainable development and compliance with environmental legislation, three fundamental principles are required to not compromise the needs of future generations: reducing consumption, reusing, and recycling (Dal Molin et al., 2016). It is clear that among these alternatives, it is often unfeasible to apply the first option, which is why studying and practicing waste reuse and recycling is extremely important.

The construction industry, responsible for the consumption of approximately 50% of the planet’s raw materials (John, 2001), presents itself as an excellent option for reusing by-products generated in industrial processes and has already been the target of study by several research that aimed at valuing waste (Almada; Santos; Souza, 2022; Carvalho et al., 2023; Oliveira; Costa; Motta, 2024; Simões et al., 2023).

In this context, the use of supplementary cementitious materials (SCMs) has emerged as the primary alternative to developing cement with reduced clinker contents (He et al., 2022; Juenger; Snellings; Bernal, 2019; Scrivener; John; Gartner, 2018). The use of residual SCMs, such as fly ash, silica fume, and granulated blast furnace slag, is already widely adopted by the cement industry. NBR 16697 (ABNT, 2018a) allows for the partial substitution of clinker with up to 75% blast furnace slag and up to 50% pozzolanic material. However, as highlighted by Scrivener, John, and Gartner (2018), by 2050, these resources may meet less than 20% of global demand, leaving space for the development of new research seeking potential alternative materials for cement production.

The cement industry has been adopting the addition of limestone powder as a filler by partially replacing clinker, promoting a reduction in pollutant emissions (Scrivener; John; Gartner, 2018). In addition to being a more sustainable alternative, limestone-filled cement can refine the microstructure and reduce the porosity of cementitious materials (Wang et al., 2018). Studies also demonstrate that limestone can react during the cement hydration process with alumina and form carboaluminate compounds, which in turn contribute to strength and durability (Lothenbach et al., 2008; Matschei; Lothenbach; Glasser, 2007).

The scientific community has also studied the use of industrial waste. These materials can be finely ground and used as fillers as long as they have an appropriate chemical composition. Fillers can be added to concrete over the cement mass, filling voids and creating nucleation points, thus improving mechanical properties and durability (Lawrence; Cyr; Ringot, 2003). This approach can reduce environmental impact and promote greater sustainability in the construction industry by decreasing clinker consumption and utilizing waste without defined use. Among these wastes are those generated from cellulose production.

The Brazilian cellulose industry, in 2020, had a production of around 21 million tons (IBÁ, 2022; FAO, 2022), with the Kraft process being one of the most adopted methods for cellulose production. It is estimated that it represents 80% of the procedures industry uses in the United States (Cheremisinoff; Rosenfeld, 2010). Globally, approximately 130 million tons from the Kraft process are produced annually (Mathew et al., 2018). From this, due to the implementation of a recovery plant in the process, various wastes are generated that require better disposal, and among these, dregs and grits stand out.

Dregs waste is generated from the green liquor clarification process, which removes suspended solids by decantation and washing the material to remove residual soda (Martins, 2006). Grits is a residue from the hydrator and is classified as uncalcined lime, removed from the bottom of the lime slaker (Torres, 2016).

Based on data provided by a pulp industry in southern Brazil, it is estimated that the monthly generation of dregs and grits is, respectively, 9.339,51 and 619,27 tons. Therefore, it is notable that these wastes present a representative generation and signal the possibility and need for use.

However, evaluating the bibliography reveals that the high potential for reuse of these by-products becomes challenging due to the high content of alkalis (Na₂O and K₂O) in the chemical composition of the materials. These alkalis can promote expansive reactions, especially in cementitious matrices of the alkali-silica type (Mymrin et al., 2020; Rodrigues et al., 2019; Santos et al., 2019).

The analysis of the impact generated by alkalis present in waste on cementitious matrices has not yet been thoroughly explored in the existing literature. This research aims to contribute to closing this gap. Thus, this paper proposes the production of coating mortars by incorporating different levels of waste to evaluate the feasibility of using dregs and grits waste. The proposed systems underwent characterization tests in both fresh and hardened states, as well as expansion tests through the alkali-silica reaction (ASR) test to detect any reactive tendencies caused by the addition of this residue.

Experimental program

Materials

The wastes used in this research were made available by a pulp industry in the southern region of Brazil. Collected at the factory, these went through a drying process in an oven at 100 °C for a period of 24 hours to remove all moisture present. When collected, the dregs residue, dark gray in color, was found in fine grain size, with few lumps, while the grits, light gray in color, had a more significant number of lumps but were very friable (Figure 1).

Figure 1
Waste after collection: (a) dregs and (b) grits

The grits were crushed using a jaw crusher so that both residues would have similar granulometric characteristics. After this process, both residues were sieved through a mesh with an opening of 0.15 mm.

The Portland cement used was CP V-ARI. This cement was chosen due to its high purity and lack of chemically active additions (ABNT, 2018a).

The fine aggregate, coming from the natural extraction of Guaíba River/ Porto Alegre/ RS, was separated into different particle size fractions, as requested by NBR 15577-4 (ABNT, 2018b), to enable the characterization tests to be carried out and alkali-silica reactivity.

The surface area test (BET) determined the area to be 5.02 m²/g for dregs and 1.60 m²/g for grits. To determine the particle size distribution, laser granulometry of the fines was carried out with a PSA 1090 L Anton-PASR equipment (grain reading range between 40 nm-500 mm and wet method in isopropyl alcohol) and is presented in Figure 2.

Figure 2
Granulometric distribution of materials

Figure 3 displays electron scanning microscopy micrographs of the dregs and grits residues, respectively. Both residues appear as clusters with irregular-shaped structures. It is noted that the particle size distribution obtained by laser granulometry corroborates with what is found in the micrographs, where the grits present larger grain sizes compared to the dregs. Both residues, especially the dregs, have rough surfaces, which can significantly increase water demand due to the greater hydration surface. As also observed by BET analysis, the dregs have a larger surface area.

Figure 3
MEV by secondary electrons (x500)

The analysis by X-ray fluorescence, using a Rigaku RIX 2000 X-ray fluorescence spectrometer, of CP V-ARI shows the predominant presence of CaO and SiO₂, as demonstrated in Table 1.

Table 1
Chemical composition of CP V - ARI

%	SiO2	Al2O3	TiO2	Fe2O3	MnO	CaO	MgO	K2O	P2O5	PF
CP V - ARI	18.43	3.53	0.24	2.76	0.04	63.18	2.80	0.86	0.12	3.60

The mineralogical analysis of the samples was carried out using X-ray Diffraction, with the Philips X-ray diffractometer, model X’Pert MDP (X-ray tube with Cu radiation) in the range of 5 – 80°. The analysis was carried out using the X’Pert High Score software. Figure 4 presents the diffractograms of the dregs and grits, and it is possible to observe a remarkable similarity between the position and intensity of the peaks. Being mainly composed of calcium carbonate in the form of calcite (CaCO₃), dregs also contain the presence of sodium nitrate in the form of nitrate (NaNO₃), and in grits, the presence of silicon dioxide (SiO₂) and hematite (Fe₂O₃).

Figure 4
Diffractography of samples of (a) dregs and (b) grits (C: CaCO₃, N: NaNO₃, S: SiO₂ and H: Fe₂ O₃)

$\mathrm{\%}{\mathbf{C}\mathbf{a}\mathbf{C}\mathbf{O}}_3=\frac{{\mathrm{MCaCO}}_3}{{\mathrm{MCO}}_2}\ast \mathrm{\%}{\mathbf{C}\mathbf{O}}_2$ Eq. 1

From the thermogravimetric analysis of the residues (Figura 5a), a prominent peak can be seen, in common, between 600 ºC and 800 ºC. This peak may be related to the decomposition of CaCO₃. For CP V-ARI (Figure 5b), Ca(OH)₂ and CaCO₃ are mainly identified. Table 2 presents the percentages of mass loss obtained for the products present in the samples, calculated according to Eq. 1, which uses the molar relations between CaCO₃ (100.09 g/mol) and CO ₂ (44.01 g/mol).

Figure 5
Thermogravimetry

Table 2
Mass losses of products present in cement samples

Materials	Weight loss (%)
	Ca(OH) 2	CaCO3	Total
CP V-ARI	1.73	12.25	13.98
Dregs	-	86.71	86.71
Grits	-	93.17	93.17

Methods

Mortars were molded with a mass ratio of 1:2.25 and a fixed water/cement ratio of 0.47. The percentages of waste addition about cement were 7.5 and 15%. Therefore, the addition of dregs has the nomenclatures of 7.5D and 15D, and with grits of 7.5G and 15G. Furthermore, a mortar was produced without the addition of any residue, called REF, used as a comparison standard for the other formulations. The mixing and production of mortars took place according to the normative parameters of NBR 15577-4 (ABNT, 2018b). Table 3 shows the amount of each material used in the mixtures.

Table 3
Quantity of materials used by mass

Materials		REF	7.5D	15D	7.5G	15G
Cement (g)		1000	1000	1000	1000	1000
Sand (g) in each sieve opening	2.36mm	225	225	225	225	225
	1.18mm	562.5	562.5	562.5	562.5	562.5
	0.6mm	562.5	562.5	562.5	562.5	562.5
	0.3mm	562.5	562.5	562.5	562.5	562.5
	0.15mm	337.5	337.5	337.5	337.5	337.5
Waste (g)		0	75	150	75	150
Water (g)		470	470	470	470	470

To analyze the influence of different levels of waste addition in the mortars in the fresh state, they were subjected to the mass density test (ABNT, 2005a) and consistency index (ABNT, 2016).

In the set state, tests were carried out to characterize mass density (ABNT, 2005b), dynamic modulus of elasticity (ABNT, 2008), determination of flexion and compression strength (ABNT, 2005a), and water absorption by capillarity (ABNT, 2005c). The specimens were kept in a climate-controlled chamber with a temperature of 23±2 ºC and humidity of 60±5٪ until tests were carried out at 28 days.

The alkali-silica reaction test was carried out using the accelerated mortar prism method following the guidelines of NBR 15577–4 (ABNT, 2018b).

Results and discussions

Properties in the fresh state

Table 4 presents the test results to determine the consistency index and mass density in the fresh state of the mortars. It is observed that the mortar with the addition of 7.5% grits presented the highest consistency index, while the mortar with 7.5% dregs presented the lowest. A decrease in the workability of mortars following the introduction of dregs was also observed by Menezes (2022), Novais et al. (2018), and Oliveira (2022). About grits Oliveira Junior et al. (2019), from the partial replacement of natural sand with residue, an increase in the fluidity of the mortars with the addition of residue was also noted. Therefore, the 7.5G system has better workability than the others, as it is related to the ability to spread and fill irregularities in the substrate.

Table 4
Parameters of mortars in the fresh state

Tests	REF	7.5D	15D	7.5G	15G
Consistency index (cm)	24.83	24.50	24.67	27.50	26.83
Mass density (kg/m³)	2176.65	2228.88	2248.29	2151.60	2168.29

It can be inferred that using dregs residue tends to promote a decrease in the consistency index of the mortars by 1.34% and 0.67% for 7.5D and 15D, respectively. As for grits, a contrary behavior is noted, with an increase in workability compared to the reference, by 10.74% and 8.05% for 7.5G and 15%, respectively.

The mass density test showed that the mortar with the addition of 15% dregs presented the highest mass density value, while the one with the addition of 7.5% grits presented the lowest. The samples with the addition of dregs showed an increase of 2.40% and 3.29% at concentrations of 7.5% and 15%, respectively. Conversely, for grits, there were reductions of 1.15% and 0.38% at concentrations of 7.5% and 15%, respectively.

As observed in the characterization tests of the dregs, the residue has smaller particle sizes and a larger surface area. This can contribute to higher water absorption in the mixture, resulting in lower consistency index values. Additionally, the reduced particle size of the dregs, compared to the grits, can lead to a higher mass density.

Properties in hardened state

Table 5 shows the mortars’ mass density and capillarity coefficient tests.

Table 5
Mass density and capillarity coefficient.

Tests	REF	7.5D	15D	7.5G	15G
Mass density (kg/m³)	2074.9 ± 33.39	2113.8 ± 10.20	2147.9 ± 21.75	2098.4 ± 3.63	2075.2 ± 27.92
Capillarity coefficient (g/dm².min 1/2)	3.41 ± 0.49	3.66 ± 0.04	3.02 ± 0.23	4.28 ± 0.29	3.09 ± 0.21

Due to the residue’s fine granulometry, higher mass density values were evident for systems with dregs additions. Alvarenga et al. (2021) also observed that this fact is possibly linked to the considerable fineness of this residue, which has a granulometric profile close to that of cement. In general, the other test results demonstrate remarkable similarity, with all systems with the addition of residues presenting values higher than those of the reference.

Regarding the capillarity coefficient, it is noted that in the 7.5D and 7.5G systems, there was a gain of 7.4% and 25.7%, respectively, in relation to the reference. The capillarity coefficients for the 15D and 15G systems were lower than the reference, in the order of 11.3% and 9.5%, respectively.

The analysis of variance (ANOVA), with a 95% confidence level, identifies a statistically significant difference between the samples for mass density in the hardened state. However, when analyzing the capillarity coefficient, the samples are considered equivalent, as demonstrated in Table 6.

Table 6
ANOVA of mass density and capillarity

Effect	Square Sum	Degrees of freedom	Mean Square	F Test	Probability	Significant Influence
Mass density
Sample	10995	4	2749	5.5	0.012979	Yes
Error	4969	10	497
Capillarity coefficient
Sample	1.6260	4	0.4065	0.7918	0.556503	No
Error	5.1336	10	0.5134

The analysis of multiple means using the Tukey test, conducted for the mass density results in the hardened state, was found to be statistically significant, as presented in Table 7.

Table 7
Multiple mean analysis for the results of mass density in the hardened state

-	Samples	1	2	2	4	5
1	REF	-	NS	S	NS	NS
2	7.5D	NS	-	NS	NS	NS
3	15D	S	NS	-	NS	S
4	7.5G	NS	NS	NS	-	NS
5	15G	NS	NS	S	NS	-

Most of the samples exhibit equivalence when compared to each other. However, there are significant differences observed in samples 15D and 7.5D compared to REF and 15G compared to 15D and 7.5D.

Figure 6 presents the results obtained for compressive strength and dynamic modulus of elasticity of the mortars studied.

Figure 6
Compressive strength and dynamic modulus of elasticity of mortars

The 15D system presented greater mechanical resistance to compression, 9.0% about REF, and a higher dynamic modulus of elasticity. This probably occurs due to the filling of voids, which the high fineness of this residue made possible. The results of mass density tests in the hardened state corroborate this hypothesis. Similarly, the 7.5D system demonstrated a gain of 0.9% concerning the REF.

The increase in mechanical strength through the incorporation of dregs in cementitious matrices was also observed by Martínez-Lage et al. (2016). In this study, the authors observed that for an addition content of 10% of dregs, the proposed systems presented mechanical resistance, in the order of 4%, higher than the reference (without additions).

On the other hand, the systems with the addition of grits, 7.5G and 15G, showed a reduction in compressive strength of 9.2% and 3.8%, respectively, about the reference. These results are likely linked to the larger particle size of the grits. According to Oliveira, Costa and Motta (2024), the additions must have dimensions less than 75 µm to promote the physical effect.

Oliveira, Costa and Motta (2024) found similar results from replacing CP V-ARI cement with dregs and grits at 5, 10, 20 and 30% levels. The authors found that minor substitutions, such as 10%, promote small reductions in compressive strength, 12 and 18% for dregs and grits, respectively. Additions of 30% have a representative impact, in the order of 46% and 49%.

Regarding compressive strength and dynamic modulus of elasticity, the analysis of variance indicates that for both tests, the results show statistically significant differences between the analyzed mortars (Table 8).

Table 8
ANOVA of compressive strength and dynamic modulus of elasticity

Effect	Square Sum	Degrees of freedom	Mean Square	F Test	Probability	Significant Influence
Compressive strength
Sample	227.44	4	56.86	16.68	0.000001	Yes
Error	85.24	25	3.41	-	-	-
Dynamic modulus of elasticity
Sample	30.08	4	7.52	4.36	0.026905	Yes
Error	17.26	10	1.73	-	-	-

Table 9 presents the results of multiple mean analysis for the compression strength and dynamic modulus of elasticity results.

Table 9
Multiple mean analysis (a) compressive strength and (b) dynamic modulus of elasticity

-	Samples	1	2	3	4	5		-	Samples	1	2	3	4	5
1	REF	-	NS	S	S	NS		1	REF	-	NS	NS	NS	NS
2	7.5D	NS	-	S	S	NS		2	7.5D	NS	-	S	NS	NS
3	15D	S	S	-	S	S		3	15D	NS	S	-	NS	NS
4	7.5G	S	S	S	-	NS		4	7.5G	NS	NS	NS	-	NS
5	15G	NS	NS	S	NS	-		5	15G	NS	NS	NS	NS	-

For compressive strength, it is verified that among most samples there is a statistically significant difference. The samples 15G and 7.5G are considered equivalent in relation to REF, 15G, and REF in relation to 7.5D, and 15G in relation to 7.5G. For the dynamic modulus of elasticity, only the sample 15D in relation to 7.5D is considered different, while the others are considered equivalent.

The results of the flexural strength test can be viewed in Figure 7. It is possible to observe substantial similarity between the values found for all systems evaluated. In relation to the reference, the 7.5D mortar shows an increase in strength of about 4.4%, whereas 15D, 7.5G, and 15G exhibit reductions of about 0.4%, 4.2%, and 10.9%, respectively. However, the slight reduction in resistance that is noted, proportional to the addition of residues, is in line with the bibliography since previous studies also found a decrease in strength in flexion of mortars when molded with the addition of dregs and grits residues (Alvarenga et al., 2022; Oliveira Junior et al., 2019; Martínez-Lage et al., 2016).

Figure 7
Tensile strength in flexion

Regarding flexural tensile strength, ANOVA does not identify a statistically significant difference between the results, as shown in Table 10.

Table 10
ANOVA of flexural tensile strength

Effect	Square Sum	Degrees of freedom	Mean Square	F Test	Probability	Significant Influence
Sample	2.3772	4	0.5943	1.293	0.336295	No
Error	4.5951	10	0.4595	-	-	-

Expansion by alkali-silica reaction (ASR)

The determination of expansion in mortar bars using the accelerated method occurred by NBR 15577 (ABNT, 2018b, 2018c), parts 1 and 4. The molded systems, subjected to normative parameters, showed expansive behavior throughout the test period, as demonstrated in Figure 8.

It was observed that the incorporation of waste, both grits, and dregs, increased the reactivity and promoted the major expansion of the mortars when in contact with the alkaline solution at high temperatures. The system with the addition of 7.5% dregs showed greater expandability than the others after 30 days of testing. Regarding the reference, the mortars 7.5D, 15D, 7.5G, and 15G showed, respectively, higher expansion in the order of 42.3%, 10.6%, 24.3%, and 18.8%.

Figure 8
Average expansion of mortar system bars over time

The bibliography confirms this behavior since the alkaline equivalent of dregs varies between 3.6 to 12.4% (Siqueira; Holanda, 2018; Rodrigues et al., 2019; Mymrin et al., 2020) and grits between 0.7 and 4.7% (Rodrigues et al., 2016; Siqueira; Holanda, 2018; Mymrin et al., 2020). Therefore, a higher alkali content is found in dregs than in grits.

Contrary to expectations, increasing the level of waste addition in the mortars did not increase reactivity since systems with 15% waste incorporation recorded lower expansibility than systems with 7.5% addition. This inversely proportional behavior had already been registered in previous studies evaluating rice husk ash residue (Andrade; Santos; Fontoura, 1993; Hasparik, 1999; Silveira, 2007; Abbas; Kazmi; Munir, 2017).

The observed inverse behavior, with smaller expansions for 15% additions, is believed to be related to the filler effect created by the increased incorporation of dregs and grits. This densification of the cementitious matrix likely limits the penetration of alkalis from the sodium hydroxide solution used in the accelerated mortar bar test. However, further studies are necessary to better understand this behavior.

Furthermore, the CP V–ARI cement adopted to carry out the test, according to NBR 16697 (ABNT, 2018a), can only have up to 10% carbonate material as a mineral addition. In this sense, several studies have already found that the lack of additions of pozzolanic material or blast furnace slag makes it incapable of promoting ASR mitigation (Dutra, 2018; Tiecher, 2006). Notably, the fine aggregate used in molding mortar systems showed reactive behavior since the reference system reached expansibility values higher than the normative limits.

Table 2 of item 5.3 of NBR 15577-1 (ABNT, 2018c) shows that the natural fine aggregate used in the test is classified as potentially reactive grade R1, as it showed expansion between 0.19% and 0.40% at 30 days. This factor may have contributed to amplifying expansion values observed for systems with waste addition. Therefore, the 15D and 15G systems are also classified as R1, while the 7.5D and 7.5G compositions are classified as potentially reactive grade R2 (0.41% to 0.6%). It is important to note that these classifications pertain to mortars made with standard cement. In this research, they are also applied to classify mortars with dregs and grits wastes, serving as a comparative benchmark for the results obtained.

The analysis of variance (ANOVA), with a reliability of 95%, identifies a statistically significant difference between the controllable factor (addition) and the response variable (expansion) at 30 days for both wastes (Table 11).

Table 11
ASR variance analysis

Effect	Square Sum	Degrees of freedom	Mean Square	F Test	Probability	Significant Influence
Dregs	0.03279	2	0.016395	31.15	0.000678	Yes
Error	0.003158	6	0.000526	-	-	-
Grits	0.010876	2	0.005438	18.582	0.002686	Yes
Error	0.001756	6	0.000293	-	-	-

The multiple means analysis (Figure 9) using the Tukey method demonstrated that the difference occurs between 7.5D about the others in systems with the addition of dregs; therefore, REF and 15D are considered equivalent. Regarding grits, the mortar without adding grits presents significantly different values from the samples with 7.5 and 15% residue, whereas the compositions 7.5D and 15D are considered equivalent.

Figure 9
Multiple comparisons of means

Conclusion

Based on the results obtained, it can be concluded that:

1. at an intermediate level of grits addition (7.5%), the presence of this waste increases the consistency index of the mortar, making it more workable;

2. at higher levels of dregs (15%), the mortars presented values of mechanical strength to compression and dynamic modulus of elasticity more heightened than the reference system, indicating that this addition may be capable of amplifying the mechanical performance of mortars;

3. regarding the alkali-silica reactivity test, the predictable expansibility of the residue that would be brought to the mortar concerning the reactive medium was verified. However, it is noteworthy that the increase in the waste incorporation content reduced the expansive behavior compared to lower levels;

4. the results show that waste can be a viable alternative when used as an addition to cement matrices; and

5. new studies are suggested regarding using dregs and grits in mortars, particularly non-reactive aggregates, and proposing incorporating a wider range of addition levels of these residues and other types of cement Portland.

References

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Edited by

• Editores
  Marcelo Henrique Farias de Medeiros

• Editores de seção
  Edna Possan, White José dos Santos e Daniel Pagnussat

Publication Dates

• Publication in this collection
  10 Mar 2025
• Date of issue
  Jan-Dec 2025

History

• Received
  09 Mar 2024
• Accepted
  22 June 2024