*3.4. Authors*

Citations indicate a researcher's influence within a certain study domain [104]. For the evaluation of authors, the "kind of analysis" was chosen "co-authorship", and the "unit of analysis" was chosen "authors". The minimal paper restrictions for a writer were kept at 5, and 50 of the 2226 authors met this condition. Table 3 summarizes the most prolific authors in terms of publications and citations in the research of RHA concrete, as determined by data obtained from the Scopus search engine. The average citations for each author were calculated by dividing the total citations by the total publications. It will be difficult to quantify a scientist's efficacy when all factors such as the number of publications, total citations, and average citations are included. In contrast, the writer's assessment will be determined independently of each factor, i.e., total publications, total citations, and average citations. Nuruddin M.F. is the leading author with 16, followed by Zain M.F.M. and Mahmud H.B. with 14 each, and Shafiq N. with 13 publications. Jaturapitakkul C. leads the field in terms of total citations with 973, Zain M.F.M. is second with 738, and Chindaprasirt P. is third with 668 total citations in the current study area. Furthermore, when comparing average citations, the following writers stand out: Jaturapitakkul C. has around 97, Chindaprasirt P. has approximately 84, and Bui D.D. has approximately 82

average citations. Figure 8 illustrates the relationship between authors who have published at least ten publications and the most eminent authors. It was noticed that the largest set of connected authors based on citations are 6 of the 60 authors. This study revealed that a small number of writers are connected by citations in the research of RHA concrete.

**Figure 7.** Keywords analysis: (**a**) scientific visualization; (**b**) density visualization.


**Table 3.** Authors with at least five publications in the research of RHA concrete up to 2021.

#### *3.5. Documents*

The amount of citations a document obtains reflects its influence on a certain area of research. Papers with a high citation count are recognized as pioneers in their respective fields of research. For the assessment of documents, the "kind of analysis" was set to "bibliographic coupling" and "unit of analysis" to "documents". The least citations requirement for a document was 50, and 121 of 917 documents satisfied this requirement. The top ten papers in

the area of RHA concrete by citations are included in Table 4, along with their writers and citation information. Ganesan K. [105] received 346 citations for their article "Rice husk ash blended cement: Assessment of optimal level of replacement for strength and permeability properties of concrete". G.C. Isaia [106] and D.-Y. Yoo [107] received 329 and 228 citations, respectively, for their publications and were positioned in the leading three. However, up until 2021, only 18 publications received more than 200 citations. In addition, Figure 9 illustrates the map of linked papers based on citations, as well as the density of those documents in the current study subject. The analysis revealed that 112 of 121 papers were linked by citations. Figure 9a illustrates the citation-based mapping of connected articles. Also, the density mapping (Figure 9b) reveals the top articles' enhanced density concentration.

**Figure 8.** Scientific visualization of authors that published articles in the related research area.

**Table 4.** The top ten highly cited published articles up to 2021 in the research of RHA concrete.


**Figure 9.** Scientific mapping of published articles in the related research area up to 2021; (**a**) connected articles in terms of citations, (**b**) density of connected articles.
