A bibliometric and content analysis of research trends in paver blocks: Mapping the scientific landscape

2.2.1 Bibliometric analysis

The bibliometric analysis, a quantitative approach, focused on several key indicators, including publication evolution over time, geographical distribution, and collaboration among countries, influential sources of publication, productive authors and their collaboration networks, and keyword occurrence and co-occurrence analyses [36,37]. Tableau was used to create visualizations and graphs, while VOSviewer software (version 1.6.17) was employed to generate and analyze bibliometric networks, such as co-authorship, keyword co-occurrence, and citation linkages [38].

2.2.2 Content analysis

To complement the quantitative bibliometric analysis, a qualitative content analysis was conducted on the top ten most cited articles in the paver block literature [39]. The content analysis examined the research objectives, methodologies, key findings, and implications of these influential studies. Particular attention was given to the incorporation of waste materials in paver block production, innovative design strategies for enhancing paver block performance and sustainability, and the optimization of mix designs and processing techniques. The content analysis aimed to provide a deeper understanding of the most significant contributions and trends in the field and identify potential areas for future research [40]. In summary, this study integrates bibliometric and content analysis to comprehensively and rigorously assess the paver block research landscape. Using Scopus as the data source, along with Excel, Tableau, and VOSviewer for data processing, analysis, and visualization, ensures a transparent and replicable approach to mapping the scientific knowledge in this domain.

3.1.1 Publication trends

Figure 2 shows the publication evolution in the field of paver block research. The annual scientific production shows a steady growth trend over the years, with some interesting fluctuations. This growth can be attributed to the increasing importance of sustainable construction practices and the need for alternative materials in the construction industry [41,42]. In the early years, from 1983 to 1991, the number of publications remained relatively low, ranging from 1 to 4 per year, with no significant impact on citations. This suggests that the field of paver block research was still in its early stages, with limited interest from the scientific community. However, a noticeable increase in publications started in 1992, with a peak of five publications in 2000. This indicates a growing interest in paver block research during this period, which can be attributed to the increasing awareness of environmental issues and the need for sustainable construction practices. The year 2002 stands out as a remarkable year, with a single publication garnering an impressive 364 citations. This highly influential work, titled “Use of recycled concrete aggregate in concrete paving blocks” by Poon et al. [43], significantly contributed to the field by demonstrating the feasibility of using RCA in paver block production. From 2005 onward, there is a consistent increase in the number of publications, with a substantial rise in citations. The year 2007 marks a significant milestone, with four publications collectively amassing 453 citations, highlighting the impact and relevance of the research conducted during this year. The annual scientific production in paver block research reaches new heights from 2016 to 2024, with a substantial increase in both publications and citations. This upward trend aligns with the global push toward sustainable development goals and the increasing demand for eco-friendly construction materials. The year 2016 saw a surge in publications, with 26 articles published, accompanied by an impressive 782 citations. This growth continues, with the highest number of publications (60) recorded in 2023, demonstrating the growing interest and investment in this field.

Figure 2

Evolution of publication output and citations for paver block research.

Overall, the analysis of the evolution of publication in the field of paver block research reveals a positive growth trend, with increasing annual scientific production and a corresponding rise in citations. The data highlights the years 2002 and 2007 and the period from 2016 to 2024 as particularly significant in terms of research output and impact, reflecting the ongoing development and importance of this field in sustainable construction practices. The increasing research indicates that the study of paver block is in its “growth stage” and has great potential for further development.

To further investigate the temporal distribution of keywords used in search string, Figure 3 presents a stacked area plot illustrating the frequency of each keyword from 1983 to 2024. This graph reveals the relative prominence and evolution of keywords over time, providing insights into the changing research focus within the paver block domain.

Figure 3

Search string keyword frequency over time.

As shown in Figure 3, the keyword “paver block” has maintained its dominance throughout the years, while other keywords such as “interlocking concrete block,” “permeable paver,” and “concrete paving block” have gained increasing attention, particularly in the last decade. This trend suggests a growing interest in specific paver block types and their functional properties, reflecting the advancements and priorities in paver block research.

3.1.2 Geographical distribution and international collaboration in paver block research

The analysis of the geographical distribution of paver block research, as summarized in Table 1, reveals that India has made the most significant contribution to this field, with 143 publications accounting for 37.73% of the total. This high productivity may be attributed to the rapid urbanization and infrastructure development in India, which has spurred interest in sustainable construction materials like paver blocks. Malaysia follows India with 28 publications (7.39%), while the United States ranks third with 27 publications (7.12%). However, the United States leads in terms of total citations (1,312) and citations per paper (48.59), indicating the high impact and visibility of the research originating from this country. Brazil and China also feature prominently, with 22 (5.80%) and 15 (3.96%) publications, respectively. Notably, publications from China have garnered a high number of citations (688), with an average of 45.87 citations per paper, suggesting the influential nature of the research. The United Kingdom, Italy, Canada, Hong Kong, and Spain each contribute between 2.64 and 3.17% of the total publications. Among these, Hong Kong stands out with an exceptionally high number of citations per paper (129.70), indicating the significant impact of the research from this region.

The international collaboration network among countries involved in paver block research, as shown in Figure 4, reveals three main clusters of cooperation, showcasing the global nature of this research field. The first cluster, represented in red, includes China, Germany, Spain, Sri Lanka, Turkey, the United Kingdom, and the United States, suggesting a strong collaborative relationship among these countries. The United States and China appear to be the key players in this cluster, likely due to their significant research output and influence in the field. Moreover, both countries have a high number of citations per paper (48.59 for the United States and 45.87 for China), indicating the substantial impact of their collaborative research. The second cluster, depicted in green, comprises Egypt, Hong Kong, Indonesia, Malaysia, Pakistan, Poland, and Saudi Arabia, indicating active collaboration among these countries. Malaysia seems to be a central node in this cluster, possibly as a bridge connecting the other countries. This is consistent with the geographical distribution data, which places Malaysia as the second most productive country. The high average citations per paper (11.86) for Malaysia further highlight the significance of its collaborative efforts within this cluster. The third cluster, shown in blue, consists of Australia, Canada, India, Italy, and South Korea, with India appearing to be the most prominent collaborator within this group. The role of India in this cluster is not surprising, given its top position in the geographical distribution of paver block research. These clusters reveal interesting trends and differences among countries. For example, while India leads in publication count, the United States and China demonstrate higher citation impacts, suggesting a difference in the influence and visibility of their research. Additionally, countries like Malaysia and India play central roles in connecting researchers from different regions, facilitating international collaboration.

Figure 4

International collaboration network for paver block research.

Interestingly, some countries, such as Hong Kong and Italy, despite having a relatively lower number of publications (10 and 12, respectively) have established strong collaborative ties within their clusters. This suggests that the quality and impact of research, as indicated by the high citations per paper (129.70 for Hong Kong and 10.25 for Italy), may play a crucial role in fostering international collaboration. The key players identified within each cluster, such as the United States, China, Malaysia, and India, have not only contributed significantly to the research output but have also played a vital role in connecting researchers from different countries, facilitating knowledge exchange, and driving innovation in paver block research.

3.1.3 Analysis of the top ten most influential journals in paver block research

The analysis of the top ten most influential journals in paver block research, as listed in Table 2, reveals several interesting findings. Out of the 379 research articles and reviews published across 174 journals, the top ten journals collectively account for 33.86% of the total publications (Figure 5), indicating their significant contribution to the field. Construction and Building Materials emerges as the most prolific journal, with 28 publications (7.39%) and an impressive total citation count of 1,581, resulting in the highest citation per paper ratio (56.46) among the top ten journals. The journal’s h-index of 259 further underscores its substantial impact on the field. Journal of Cleaner Production follows closely, with 12 publications (3.17%) and the second-highest total citation count of 1,100, translating to an average of 91.67 citations per paper and an h-index of 309, which is the highest among the listed journals. This suggests that the journal publishes highly influential and widely cited research in the area of sustainable construction materials, including paver blocks.

Figure 5

Top ten most prolific journals.

It is noteworthy that Materials Today: Proceedings has published 17 articles (4.49%) on paver block research, indicating a growing interest in this topic among material science researchers. However, the relatively low citation count (32) and average citations per paper (1.88) suggest that these articles may be more recent or focused on niche aspects of paver block research. On the other hand, journals such as Case Studies in Construction Materials and Road Materials and Pavement Design have published fewer articles (12 and 11, respectively) but have garnered higher average citations per paper (25.92 and 10.36, respectively), indicating the publication of impactful research.

The presence of journals from various disciplines, such as construction materials (Construction and Building Materials, Case Studies in Construction Materials), cleaner production (Journal of Cleaner Production), pavement engineering (Road Materials and Pavement Design, International Journal of Pavement Engineering), and civil engineering (Journal of Materials in Civil Engineering), highlights the multidisciplinary nature of paver block research. This diversity in journal scope suggests that paver block research encompasses a wide range of aspects, including material properties, sustainability, pavement design, and civil engineering applications.

In total, the 379 research articles and reviews published in the 174 journals have amassed an impressive 6,366 citations, emphasizing the growing interest and impact of paver block research. The analysis of the top ten most influential journals provides valuable insights into the key players driving the advancement of this field and the multidisciplinary nature of the research being conducted.

3.1.4 Most productive authors and their collaboration

Table 3 presents the productivity and citation impact of the leading authors in paver block research. The analysis of the top ten most productive authors in paver block research reveals intriguing insights into the distribution of research output and impact across countries and individuals. Sunitha V. and Arjun Siva Rathan R.T. from India lead the list with nine publications each, followed by Poon C.S. from Hong Kong with eight publications. However, when considering the total citations and average citations per publication, Poon C.S. stands out with an impressive 1,154 total citations and an average of 144.25 citations per paper, indicating the high impact and influence of their work. Ling T.C. from China also demonstrates a strong research impact, with six publications garnering 401 total citations and an average of 66.83 citations per paper. Interestingly, while Sunitha V. and Arjun Siva Rathan R.T. have the highest number of publications, all nine of Arjun Siva Rathan R.T.’s papers are first-authored, whereas Sunitha V. has no first-author publications (Figure 6), suggesting a potential mentorship or collaboration dynamic between the two researchers. Bahurudeen A., another researcher from India, has five publications with a notable average of 43.40 citations per paper despite no first-author publications. The presence of multiple authors from India, Malaysia, and Pakistan among the top ten most productive researchers highlights the significant contributions of these countries to paver block research.

Figure 6

Comparison of total publications and first-author contributions among paver block researchers.

To gain insights into the collaboration patterns among authors in paver block research, a co-authorship network (Figure 7) was generated using VOSviewer, with the condition that a minimum of three co-authored documents per author was required for inclusion. Out of 1,072 authors who have published papers on paver blocks, only 39 met this criterion, suggesting that extensive collaboration among authors is relatively limited. The network diagram reveals the formation of several small clusters, indicating that collaborations tend to occur within specific research groups or institutions rather than spanning a wide network of authors. The largest cluster centers around the partnership between Poon C.S. and Ling T.C., two highly influential authors in the field, as evidenced by their high citation counts and average citations per paper. This strong collaboration likely contributes to their significant impact on paver block research. Other notable clusters include the collaboration between Sunitha V. and Arjun Siva Rathan R.T., who have co-authored all nine of their publications, as well as a group of authors from Malaysia, including Iftikhar B., Vafaei M., and Nor H.M. The relatively isolated nature of these clusters suggests that there may be opportunities for increased cross-institutional and international collaboration in paver block research, which could potentially lead to more diverse perspectives and innovative approaches in the field.

Figure 7

Co-authorship network of paver block researchers.

3.1.5 Keyword occurrence frequency and co-occurrence analysis

The keyword occurrence frequency and co-occurrence network provide valuable insights into the research trends and hotspots within the field of paver block research. The keyword data have been cleaned to ensure clarity and consistency by converting plurals to singulars, expanding abbreviations to full forms, and unifying synonymous terms. The analysis of the refined keyword occurrence frequency reveals that “paver block” is the most prominent keyword, appearing 85 times, followed by “compressive strength” (49 occurrences), “concrete paver block” (44 occurrences), and “concrete” (29 occurrences) (Figure 8). The high frequency of these keywords strongly suggests that the primary focus of research in this field has been on the mechanical properties and performance of paver blocks, with concrete being the most widely studied material.

Figure 8

Top ten keywords with highest occurrence frequency.

The keyword data highlight the increasing importance of sustainability and eco-friendly materials in paver block research. “Fly ash,” a waste material from coal-fired power plants, appears 27 times, indicating its growing use as a sustainable alternative to traditional cement in paver block production. The keyword “sustainability” itself occurs 19 times, underscoring the rising emphasis on developing environmentally friendly paver block solutions. Furthermore, the presence of keywords such as “permeable pavement” (20 occurrences) and “permeability” (14 occurrences) reflects the growing interest in the design and development of paver blocks that can facilitate stormwater management and reduce urban runoff.

The refined keyword data also emphasize the significance of long-term performance and durability in paver block research. “Durability” appears 21 times, while “mechanical properties” occur 17 times, highlighting the need to investigate the longevity and structural integrity of paver blocks under various environmental conditions. This focus on durability and mechanical properties is crucial for ensuring the successful application of paver blocks in real-world scenarios and promoting their widespread adoption in the construction industry.

The network visualization of the keyword co-occurrence (Figure 9) further elucidates the main research areas within the paver block domain. The largest cluster (red) focuses on permeable pavements, with prominent keywords such as “permeability, “permeable pavement,” “stormwater,” and “pervious concrete,” emphasizing the significant research attention given to the development and analysis of paver blocks with enhanced water permeability and stormwater management capabilities. The second cluster (green) revolves around the materials and sustainability aspects of paver blocks, with keywords like “fly ash,” “geopolymer,” and “cement,” indicating the exploration of alternative and eco-friendly materials in paver block production. The third cluster (blue) delves into the engineering properties and recycling, as evident from keywords such as “reclaimed asphalt pavement,” “recycled aggregate,” and “durability.”

Figure 9

Keyword network visualization for paver block research.

The smaller clusters in the network visualization provide further insights into specific research areas. The fourth cluster (yellow) focuses on specific mechanical properties and materials, such as “compressive strength,” “density,” and “crumb rubber,” while the fifth cluster (violet) is centered around the interlocking nature and optimization of paver blocks. The sixth cluster (cyan) represents the basic constituents of paver blocks, such as “coarse aggregate.”

The interconnectedness of the clusters in the keyword co-occurrence network suggests that researchers are exploring the synergies between different aspects of paver blocks, such as materials, mechanical properties, and environmental performance, to develop holistic and sustainable solutions. The presence of clusters related to recycled materials and waste utilization underscores the growing emphasis on sustainability and circular economy principles in paver block research, aligning with the findings from the keyword occurrence frequency analysis.

3.2.1 Review of the most prominent paver block studies

Figure 10 shows the top ten most influential publications on concrete paving blocks, which are all research articles. Most of these studies focused on the incorporation of various waste materials, such as recycled aggregates, waste marble, cathode ray tube (CRT) glass, and marble sludge, in the production of concrete paving blocks. The findings demonstrate the feasibility of utilizing these waste materials as partial replacements for natural aggregates or cement while maintaining or even enhancing the properties of the resulting paving blocks.

Figure 10

Ten most cited academic papers.

Several studies investigated the use of recycled aggregates from construction and demolition waste in paving blocks [43,44]. These studies found that replacing natural aggregates with recycled aggregates at levels up to 50% had minimal impact on the compressive strength of the blocks while increasing the transverse strength. The incorporation of common construction and demolition waste contaminants, such as crushed clay brick, tiles, glass, and wood chips, at a level of 10% in RCAs was found to be acceptable without significantly compromising the quality of the paving blocks [44].

The application of photocatalytic materials, particularly titanium dioxide (TiO₂), in concrete paving blocks for air purification purposes, was explored in several studies [45,46]. These studies investigated the influence of mixed design parameters, such as TiO₂ type, content, and application method, on the pollutant degradation efficiency of the paving blocks. The findings indicated that optimal mix designs, incorporating finer TiO₂ powder, higher TiO₂ dosages, and the use of recycled materials like glass aggregates, could enhance the photocatalytic performance of the blocks.

The utilization of waste marble and marble sludge as replacements for natural aggregates and cement, respectively, in paving blocks was also investigated [47,48]. These studies found that the incorporation of waste marble decreased the compressive strength but improved the freeze–thaw durability and abrasion resistance of the paving blocks. Marble sludge, when used as a partial cement replacement at an optimal level of 20%, enhanced the compressive strength, flexural strength, and water absorption of the concrete mixes.

The potential for paving blocks to mitigate stormwater runoff and urban heat island effects was explored by developing permeable and water-retaining paver designs [49,50]. Permeable pavers, such as those made with crushed stone, were found to significantly reduce runoff volume and pollutant discharge compared to conventional asphalt pavement. The novel water-retaining paver blocks demonstrated the ability to temporarily store rainwater for evaporative cooling, thereby reducing surface temperatures and mitigating urban heat island effects.

The use of waste glass, particularly CRT funnel glass, as a fine aggregate in paving blocks was investigated, with a focus on the potential for alkali-silica reaction (ASR) and the effectiveness of mineral admixtures in suppressing ASR expansion [51,52]. These studies found that limiting the CRT glass content to 25% or incorporating an appropriate level of fly ash (10%) could effectively control ASR expansion while maintaining acceptable block properties.

In summary, the content analysis of these influential papers highlights the potential for producing high-quality sustainable concrete paving blocks by incorporating various waste materials and adopting innovative design strategies. The findings support the revision of specifications to allow for higher levels of recycled materials and contaminants in paving block production, thereby promoting the recycling of waste streams. However, careful optimization of mixed designs and processing techniques is necessary to ensure satisfactory performance and durability of the paving blocks.

3.2.2 Gaps and future directions

Based on the content analysis of the ten most influential papers on concrete paving blocks, several potential research gaps and future research directions can be identified:

• Long-term performance and durability: While the reviewed studies investigated various properties of paving blocks incorporating waste materials, there is a need for more research on the long-term performance and durability of these products under real-world conditions. Future studies should focus on assessing the resistance of these paving blocks to weathering, traffic loading, and other environmental factors over extended periods.

• Life cycle assessment (LCA) and environmental impact: Although the incorporation of waste materials in paving blocks contributes to sustainability by diverting these materials from landfills, a comprehensive LCA of the environmental impact of these products is necessary. Future research should quantify the net environmental benefits of using waste materials in paving blocks, considering factors such as energy consumption, greenhouse gas emissions, and resource depletion throughout the product life cycle.

• Optimization of mix designs and processing techniques: While the reviewed studies explored various mix designs and processing techniques for incorporating waste materials in paving blocks, there is potential for further optimization to maximize waste utilization and enhance product performance. Future research should investigate advanced mix design strategies, such as using nanomaterials or chemical admixtures, and innovative processing techniques, like 3D printing or extrusion, to improve the properties and sustainability of paving blocks.

• Combination of multiple waste streams: Most reviewed studies focused on incorporating a single type of waste material in paving blocks. Future research could explore the feasibility and synergistic effects of combining multiple waste streams, such as recycled aggregates, waste glass, and marble sludge, in a single paving block product. This approach could further enhance the sustainability and performance of the blocks.

• Photocatalytic efficiency and air purification performance: While some studies investigated the photocatalytic properties of paving blocks containing TiO₂, more research is needed to optimize the pollutant degradation efficiency and assess the real-world air purification performance of these products. Future studies should evaluate the long-term stability and effectiveness of photocatalytic paving blocks under various environmental conditions and explore novel photocatalytic materials and activation methods.

• Stormwater management and urban heat island mitigation: The reviewed studies highlighted the potential of permeable and water-retaining paving blocks for mitigating stormwater runoff and urban heat island effects. However, further research is needed to quantify the hydrological and thermal performance of these products at a larger scale and under different climatic conditions. Future studies should also investigate the integration of these paving blocks with other sustainable urban drainage systems and green infrastructure elements.

• Economic and social implications: While the technical feasibility of incorporating waste materials in paving blocks has been demonstrated, research is needed on the economic and social implications of adopting these sustainable products. Future studies should assess the cost-effectiveness, market acceptance, and societal benefits of using sustainable paving blocks, considering factors such as raw material availability, production costs, and public perception.

• Policy and standardization: To facilitate the widespread adoption of sustainable paving blocks, research is needed to inform policy development and standardization efforts. Future studies should engage with policymakers, industry stakeholders, and standardization bodies to develop guidelines, specifications, and incentives that promote the use of waste materials in paving block production and ensure the quality and consistency of these products.