Bibliometric analysis in databases on publications related to the replacement of natural aggregates by residues with a focus on sustainability and Brazil

As part of a research project on the substitution of natural aggregates for residues, this article carried out a literature review, identifying articles that have the words aggregates, residues and concrete in their topics, in the Scopus and Web of Sciences bases. Among the main objectives of this review are: to verify what is the relative position of Brazil in relation to research in the area of substitution of aggregate for waste; to identify the main residues that are being studied to be used as raw material substitutes in the construction industry, mainly in Brazil; evaluate the hypothesis that a search using the words concrete, aggregate and residue will result in articles from the environmental and civil engineering areas. The main results are: Brazil is the country that most published articles with the characteristics investigated in the present work, followed by the countries China, Italy, USA and Spain; articles by Brazilian authors are predominantly from the areas of engineering and the environment; there are several studies investigating the substitution of natural aggregates for residues, mainly the substitution for residues of the civil construction itself; in Brazil, the most investigated residues to be used as raw material substitutes for the civil engineering industry are the residues of the civil engineering industry and the residues of agricultural products. The result of the review also identied the need for an improvement in the data and research tools of the databases used. The reasons are the probable data inconsistencies and aws in the research tools found in the databases. With all these results, this work intends to provide basic information for researchers who intend to initiate research on the substitution of natural aggregates for waste, in addition to using them to continue the research project of replacing part of natural aggregates with electronic waste in the production of concrete. It also intends to show the importance of revision work for the improvement of data and database tools. Abstract residue, waste To evaluate the effects of partial replacement of the natural sand aggregate of an ecological mortar by different percentages of grain residue on the compressive, exural and tensile strength of the material. The results indicate a potential for the use of this residue as a partial replacement of ne aggregates in coating mortars and suggest that 15% can be considered the ideal replacement ratio. Journal To study the use of natural sand by two mineral residues in the production of concrete. of sludge Evaluate the potential of lightweight concrete produced by replacing part of the coarse aggregate with sawdust residue, together with sludge from water treatment. chemical sodium hydroxide solution (NaOH) the physical, and microstructural properties of concrete with two levels of rubber residue 30%) as a natural substitute for ne aggregate, and the addition of silica fumes and 15%) Portland Examine the mechanical properties, resistance to compression and exion, of polymeric mortars (PM) made with used foundry waste, that is, foundry sand impregnated with polymer as aggregate. To evaluate a coating with tire waste. develop innovative polymeric composites produced with residues of industrial alumina, a by-product the steel showed compressive strength values between and 80.2 shows that it is possible to produce PC (Polymer Concrete) composites that meet the current of the civil sector using environmentally friendly materials, compromising their general Abstract Keywords Waste Residue Evaluates the partial replacement of blast furnace slag by slag from the basic oxygen furnace in the production of Portland cement. The with the of oxygen oven slag obtained initial and nal strength gains for all replacement levels. The use of oxygen furnace slag as a partial replacement for blast furnace slag proves to be a technical, economical and environmentally viable alternative for the cement industry. Methodology Journal


Introduction
Various actions, such as the increase in the number of Universities and Institutes with a focus on sustainability, contribute to infer that the commitment to sustainability is growing in the world (Khalili et al., 2015). This increase has produced improvements in some environmental indicators in recent decades. However, empirical data shows that the global increase in energy and raw material consumption has put pressure on the environment (Askham et al., 2012), mainly due to the exponential increase in the exploitation of natural resources observed in the last decades. (Gómez-Baggethun & Naredo, 2015).
Along with the increase in the consumption of natural resources, the generation of waste is also a negative factor for sustainable development. Thus, the use of waste as a raw material contributes to sustainable development, since this practice has the main bene ts of reducing environmental pollution and conserving natural resources (Onuaguluchi & Panesar, 2014).
The construction industry is largely responsible for extracting resources from nature, and today it is the largest consumer of limited natural resources, including sand, water, rocks and gravel (Mefteh et al., 2013). Many natural aggregates used in concrete are dug out of maritime mats, riverbeds, mines and other natural geological structures (Khankhaje et al., 2016). These activities cause irreparable damage to the environment due to the destruction of the geological structure and the contamination of the soil, air and water (Khankhaje et al., 2017).
In view of what has been exposed so far, this work understands that a way to contribute to lessen the negative impacts to nature, caused by the construction industry, is to replace part of the natural aggregates with residues in the production of concrete. As an initial step in this project, a literature review was carried out, with the following objectives: -Identify the pro le of the articles with the words aggregates, residues and concrete in the title, abstract or keywords, in the Scopus and Web of Science databases and with Brazilian authors; and -Obtain basic information on the types of waste under investigation to replace natural aggregates, mainly in Brazil. When obtaining this information from the literature review, this present work intends to provide basic information for researchers who intend to initiate research on the substitution of natural aggregates for residues. Another objective is to use this data to continue this project, investigating the use of electronic waste as a substitute for part of natural aggregates in the production of concrete.
In the course of this research, possible inconsistencies in the data and results provided by the tools used were identi ed. When identifying these possible inconsistencies, the objective of this work also became to contribute to the improvement of the information provided by the databases used, in addition to demonstrating the importance of literature review works to give the bases reliability and correct any information errors.

Methodology
On 09/30/2020 a survey was carried out on the Scopus base. In this research, articles were selected that had the words aggregates, residues and concrete in the title or keywords, or in the abstract. The same process was carried out on the Web of Sciences database, on 10/07/2020. With the research data, graphics were produced that shows the distribution of articles by year of publication, by country and by subject area.
After analyzing the results of the information obtained so far, this work quantitatively analyzed the data related to articles in the environmental areas. The reason is that these are the areas of interest of this present work. These analyzes produced graphs showing the distribution of articles by year of publication and country of the authors.
As one of the objectives of this work is to identify the pro le of these articles with Brazilian authors, graphics were produced that presented the following data: distribution by year of publication; distribution by thematic area; distribution, by year of publication, of articles with Brazilian authors in the environmental area; types of waste studied; graphics showing the occurrence of the words investigated here in the title, abstract or keywords; and nally, a table with the most relevant information from the articles analyzed here.

Scopus Base
In the Scopus database, 371 articles were identi ed containing the words aggregates, residues and concrete in the title or in the keywords or in the abstract. Figure 1 shows the distribution, by year of publication, of these articles. Figure 2 shows the 20 countries that most published articles with the words aggregates, residues and concrete in the title or in the keywords or in the abstract. It is worth mentioning that the Scopus Base was unable to identify the country of origin of 41 articles. Figure 3 shows the distribution of the 371 articles in the Scopus database by subject area. Figure 4 shows the distribution, by country, of the 99 articles found in the Scopus database that have the words aggregates, residues, concrete in the title or in the keywords or in the abstract and which are from the Environmental Science subject area. Figure 5 shows the evolution of the number of publications of articles in the Environmental Science subject area in the Scopus database. Figure 6 shows the summary of the main information for the article data in the Scopus database. Figure 7 shows the distribution, per year, of Brazilian publications with the words aggregates, residues and concrete in the title or abstract or in the keywords.   3.2 Web of Science Base Figure 11 shows the distribution, by year of publication, of articles with the words aggregates, residues and concrete in the title or in the keywords or in the abstract, in the Web of Science database. Figure 12 shows the distribution, by subject area, of the articles identi ed in the Web of Science database with the same characteristics as the articles researched in the Scopus database. Figure 13 shows the number of publications, distributed by country in the Web of Science database. Figure 14 shows the distribution, by year of publication, of articles in the Science Ecology Environmental subject area. Figure 15 shows the distribution, by country, of articles in the Environmental Science area. Figure 16 shows the summary of the main information for the article data on the Web of Sciences. Figure 17 shows the distribution, by subject area, of articles that have the words aggregates, residues and concrete in the title or keywords or in the abstract in the Web of Science database. Figure 18 shows the distribution, by year of publication, of articles that have Brazilian authors. Figure 19 shows the distribution, by year of publication, of articles by Brazilian authors in the subject area Sciences Ecology Environmental. Figure 20 shows the summary of the main information for article data with Brazilian authors in the Web of Sciences database.

Environmental articles with Brazilian authors
Chart 1 shows the main information from articles in the environmental areas with Brazilian authors. As can be seen in Chart 1, the total number of articles identi ed was 35. This quantity is different from the sum of the articles identi ed in the Web of Science database, which was 33, with the number of articles identi ed in the Scopus database, which was 8. This is due to the fact that ve articles are in the two bases. To study the use of natural sand by two mineral residues in the production of concrete.
It has been demonstrated that it is possible to obtain self-compacting structural concrete, self-compacting concrete without structural purpose and conventional concrete using mineral residues instead of natural aggregates. The results showed that composites with substitutions of mineral aggregates, up to 40% by mass, meet the established requirements and can be used in asphalt paving. Figure 21 shows the occurrence of the words investigated by this work in the title. Figure 22 shows the occurrence of the words investigated by this work in the abstract. Figure 23 shows the occurrence of the words investigated by this work in the keywords. Figure 24 shows the types of waste, which were studied as substitutes for raw materials in the construction industry, for the articles provided by the base tools.

Global considerations
The results show that 371 articles were found in the Scopus database and 401 in the Web of Sciences database with the characteristics investigated by this present work. The rst article with these characteristics identi ed in the Scopus database was published in 1963. In the Web of Sciences database, it was in 1996. The trend in the annual evolution of publications is similar in both bases ( Figs. 1 and 11), showing a trend of increase in the number of publications since 2006. Both bases also have their peak of publications in 2019. It is important to note that the data for 2020 refer to 09/30/2020 for the Scopus database and until 10/07/2020 for the Web of Science database. Thus, it is very likely that the peak of publications will be the year 2020, con rming the trend of increasing publications in both bases.
When analyzing the distribution of articles by country, it appears that in both bases, Brazil is the country that most published articles with the characteristics investigated in this work, both in the Scopus database and in the Web of Sciences database. Here is an observation of what is probably an inconsistency in the Web of Science base, in relation to publications by Brazilian authors. The observation is that on the day of the survey, the database showed that there were 85 articles by authors from Brazil and 5 articles by authors from "Brasil". In other words, there are actually 90 articles with authors from Brazil. It appears that the Web of Science database was unable to identify that "Brasil" is the spelling of Brazil in Portuguese. There is also an observation regarding the Scopus base. The observation is that the database was not able to identify the country of the authors of 41 articles. This number occupies the second position in the ranking of publications by country, that is, it is only behind Brazil, which has the largest number of published articles. This shows that this inconsistency is signi cant.
Regarding the subject area, Figs. 3 and 12 show that the area that most published articles was Engineering, followed by the Materials Science and Environmental areas. This on both bases. This result was already expected since the study on aggregates for concrete is strictly linked to Civil Engineering and Materials Science. The fact that the environmental area is the third area with the most publications was also expected. Among the reasons for this result, this present work highlights the fact that e cient use of natural resources is the main global political, social and economic agenda (Fargnoli et al., 2014). As a result, consumers are demanding that companies, such as the Civil Construction Company, which is largely responsible for extracting resources from nature (Mefteh et al., 2013), adopt sustainable processes to produce their products (Adeyeye et al., 2017), forcing it to invest in research in this area.
Another important factor that justi es the positions of the engineering and environmental areas is the increased concern with the destination of waste from the construction industry itself, as this type of waste occupies a lot of space in land lls worldwide (Tam et al., 2018). This factor, together with the fact that the construction industry is a major consumer of natural resources, makes concerns about sustainability occupy more space in this industry (Saieg et al., 2018). The result of these concerns is the production of more research involving the engineering and environmental areas. These researches are mainly focused on replacing natural aggregates with recycled ones, since raw materials, such as aggregates used in concrete, are nite (Onuaguluchi & Panesar, 2014).
As it is a type of waste that occupies a lot of space in land lls around the world, a large number of studies have been identi ed suggesting the use of waste from the civil construction industry itself (Tam et al., 2016). An example of this type of study is the one carried out in Turkey, where (Elçi, 2016) investigated the use of tile waste as aggregates in the production of concrete, with the objective of reducing the cost of production and minimizing the environmental impact caused by waste from tiles.
Another type of waste that is being investigated as a substitute for some of the natural aggregates in the production of concrete is agricultural waste. Although research on the use of agricultural waste as a concrete aggregate is relatively new (Sha gh et al., 2014), some studies have been identi ed in this regard. In their work (Alengaram et al., 2013) they identi ed 74 studies, only in relation to the use of palm oil as a substitute for part of natural aggregates in the production of concrete. Studies have also been identi ed that suggest the use of other types of agricultural waste as substitutes for natural aggregates.
Residues such as sugar cane ash (Ismail & Jaeel, 2014) and sugar cane bagasse (Sampaio et al., 2014). Several other studies were also identi ed indicating the feasibility of using, with acceptable performance, various solid agricultural residues, such as coconut husks, rice husks and tobacco residues as aggregates in the manufacture of concrete (Sha gh et al., 2014).
This work also identi ed several studies, such as the one carried out which suggest the use of waste tires as part of natural aggregates in the production of concrete.
In addition to the residues, this work identi ed several other studies suggesting other types of residues as a substitute for natural aggregates in the production of concrete. Among them, the polyethylene terephthalate residue (Frigione, 2010) (Saikia & De Brito, 2013). Or yet, proposals such as the use of ash from incinerated waste in dumps (Wegen et al., 2013) (Abbà et al., 2014), steel slag (Netinger et al., 2011), iron ore tailings (Shettima et al., 2016) and sewage sludge (Kosior-Kazberuk, 2011).
The analysis of the data referring to articles in the environmental areas are remarkably like the analysis made referring to the data of the total articles in the two databases. The rst article, on the Scopus database, was published in 1976 and on the Web of Science database in 1992. The trend, in both bases, is for growth starting in 2006, the same trend seen in both bases when analyzing articles from all areas.
The relevant differences in relation to the evolution of the number of publications were found in the Scopus database. The rst difference is that the peak in the number of publications was in 2018, as opposed to the peak of publications on articles from all areas, which was in 2019. The second difference is that there was a decrease in the number of publications of articles in the environmental area in 2019, while the number of publications for articles in all areas increased. The third difference is that Brazil becomes the second country to publish articles with the characteristics studied in this present work. India is in now rst place. The fourth and nal difference is the inclusion of the Single Kingdom among the main countries that have published articles.

Considerations about articles with Brazilian authors
Among the main information, in relation to articles with Brazilian authors, the fact that Brazil is in rst place in number of publications in both bases stands out. The evolution of the number of articles with published Brazilian authors is similar in both bases. Upward trend with peak in the number of publications in 2019.
Following the global trend, the largest number of Brazilian articles is from the Engineering area, followed by the Materials Science area, in both bases. In third place comes the Construction Building Technology area, on the Web of Science base, and Physics and Astronomy on the Scopus base. The environmental area is in the fourth position, in the Web of Sciences base, and in the fth position, in the Scopus base. It is worth mentioning that the Engineering, Construction Building Technology and Materials Science areas are related to civil engineering. In this way it is possible to a rm that a large part of the Brazilian articles identi ed here are from the area of Civil Engineering. The fact that the majority of articles by Brazilian authors are from the engineering area may have as one of the reasons that the construction industry has a great weight in the Brazilian economy (William et al., 2013). In 2014, the construction industry was responsible for 14% of the Gross Domestic Product (GDP) in Brazil. This industry also has great social importance, since it generates a large part of jobs for the most disadvantaged population (Santana & Oliveira, 2004).
Despite the articles in the environmental area occupying the fourth (Web of Sciences base) and the fth (Scopus base) place in the ranking of research areas, when considering only articles with Brazilian authors, these articles occupy a prominent position, globally. In the Web of Science base, it is in rst place and in Scopus in second. You also must consider that the keywords investigated here are very much related to engineering. So, it is natural to obtain more articles related to engineering, which was the case.
The fact that the environmental area appears right after the engineering areas is a strong indication that the environmental issue is a truly relevant topic for Brazil. However, considering the relevant environmental issue does not mean having an optimal condition in relation to the environment. Although Brazil publishes a lot about the environmental area, the country has di culty in dealing with sustainability. Among the main reasons for this di culty is Brazil's delay in taking concrete actions to achieve sustainability. An example of this delay are actions to tackle the issue of post-consumer waste, which had as a landmark the National Solid Waste Policy (NSWP) (DEMAJOROVIC & Migliano, 2013).
Although the NSWP was regulated on December 23, 2010, it still faces di culties in its real implementation in relation to the collection, recycling and reverse logistics of various wastes, mainly ewaste (DEMAJOROVIC et al., 2016). The consequence of these delays is the country's di culty in correctly managing its waste, such as e-waste, which has an estimated collection rate of only 2% (Azevedo et al., 2017).

Considerations on the data in Chart 1
The rst information that this work highlights from Chart 1 is that most studies used the experimental research methodology, with 31 articles, representing more than 88% of the articles. The rest of the articles used the case study methodology, two of which analyzed the product life cycle.
This present work used the tools of the Scopus and Web of Science databases to identify articles that have the words concrete, aggregate and residue in their title or abstract or Keywords. However, these tools returned articles that did not meet the research parameters, as can be seen in Figs. 21, 22 and 23. When analyzing the information of the articles, provided by the tools of the databases, in relation to the title of the articles (Fig. 21), it is possible to verify that only two articles met the research parameters. Regarding the information about the abstract (Fig. 22), only 14 articles. And lastly, regarding the Keywords (Fig. 23), no article was identi ed. It is important to note that in ve articles all three words investigated by this work appeared in two items, that is, in the title or in the abstract, in the title or in the Keywords or in the abstract and Keywords. Thus, of the 35 articles provided by the database tools, only 11 fully met the research parameters.
When considering the word "waste", which is a synonym for residue, the number of articles that met the search parameters are 4, 18 and 1 for the titles, abstract and keywords respectively. Subtracting the ve articles that contain the words in more than one item, gives a total of 18 articles. Thus, even validating the word "waste", almost 50% of the articles provided by the databases did not meet the research parameters.
It is worth highlighting the information shown in Fig. 24, where it shows that the waste that is most studied, by the selected articles, is the waste of the civil construction industry itself. This fact shows that Brazilian research follows the global trend, since the waste from the construction industry is the most investigated to be used as a substitute for raw material in this industry. Another important highlight that can be observed in the data in Fig. 24 is in relation to agricultural waste. There are several types of agricultural waste being investigated in these articles. Thus, if agricultural waste is grouped into a single type of waste, it would occupy the rst position, with seven articles.

Conclusions
The words aggregate, residues and concrete are strongly related to the area of Engineering, mainly Civil Engineering. They are also strongly related to environmental areas. This con rms the hypothesis that using these words, in the search for articles on substitution of natural aggregates for recycled ones, is an e cient way to start a research on the subject. This search will return many articles dealing with engineering and environmental issues.
The result of the search in the articles, from the Environmental area of Brazilian authors, showed that the word "waste" had a higher frequency than the word "residue". Thus, this work evaluates that it is important to include the word "waste" as a parameter in research when the objective is to investigate the replacement of natural aggregate by waste in the production of material for the civil engineering industry.
The positive evolution of the number of publications with the words aggregates, residues and concrete in the title, or in the summary or in the key words, shows the commitment of organizations to sustainability. This evolution occurs both in articles in the engineering and environmental areas, as well as in the sum of articles in all areas.
Brazil is the country with the largest number of articles published in the Scopus and Web of Sciences databases when considering all areas. It is also the rst in the environmental eld at the Web of Sciences database. At the Scopus base, it is in second place. These positions in Brazil show the country's commitment to sustainability. However, Brazil still faces great challenges to achieve it, mainly in relation to waste management.
This work suggests that the Web of Science and Scopus databases analyze the possibility of reviewing the data available in their article databases. It also suggests a review of the grassroots research tools.
The reasons for these suggestions are that an inconsistency in the number of articles with Brazilian authors was identi ed in the Web of Science database and a large number of articles without identifying the nationality of the authors in the Scopus database. In addition to these inconsistencies in the databases, it was identi ed that the search engines returned articles that did not fully meet the research requirements.
The research result, showing that the word "waste" occurred more than the word "residue", suggests that it is important to include the word "waste" as a search parameter. What will be done in a future work to compare with this one.   The 20 countries that most published articles with the words aggregates, residues, concrete in the title or keywords or in the abstract. Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors.

Figure 3
Articles found in the Scopus database by subject area Distribution, by country, of the 99 articles in the Environmental Science subject area, containing the words aggregates, residues and concrete in the title or in the keywords or in the abstract. Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors. Evolution of the number of Brazilian publications of articles with the words aggregates, residues and concrete in the title or in the keywords or in the abstract Yearly distribution of Brazilian articles on thematic area Environmental Science in the Scopus database Figure 10 Summary of the main information obtained in the Scopus base of articles with Brazilian authors with the words aggregates, residues and concrete in the title, abstract or keywords Figure 11 Page 38/45 Articles with the words aggregates, residues and concrete in the title or keywords or abstract of the Web of Sciences database Distribution, by subject area, of articles with the words aggregates, residues and concrete in the title or keywords of the Web of Sciences database Distribution, by country, of the 401 articles containing the words aggregates, residues and concrete in the title or in the keywords or in the abstract. Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors. The 230 articles in the subject area Environmental Sciences Ecology, containing the words aggregates, residues and concrete in the title or in the keywords or in the abstract in the Web of Sciences base. Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors.

Figure 16
Summary of the main information obtained in the Web of Sciences base of articles with the words aggregates, residues and concrete in the title, abstract or keywords   Summary of the main information obtained in the Web of Sciences base of articles with Brazilian authors with the words aggregates, residues and concrete in the title, abstract or keywords