*3.3. Keywords*

Keywords are important in research because they define and highlight the study domain's fundamental subject [103]. The "analysis type" was set to "co-occurrence" and the "analysis unit" to "all keywords" for the evaluation. The least repetition constraint for a keyword was maintained at 20, and 96 of the 4185 keywords were retained. The leading 20 keywords most commonly used in published articles in the topic area are listed in Table 2. Rice husk ash, compressive strength, concretes, fly ash, and cements are the five most-often appearing keywords in the subject research area. According to the keyword analysis, RHA has been studied primarily as an SCM in normal concrete, self-compacting concrete, and high-performance concrete, as well as a precursor material in

geopolymers. Figure 7 depicts a visualization map of keywords in terms of co-occurrences, linkages, and the density related to their frequency of occurrence. In Figure 7a, the size of a keyword circle implies its frequency, whereas its position implies its co-occurrence in articles. Also, the graph illustrates that the leading keywords have wider circles than the others, implying that they are critical terms for RHA concrete research. Clusters of keywords have been highlighted in the graph in a way that reflects their co-occurrence across a range of publications. The color-coded clustering is based on the co-occurrence of numerous keywords in published publications. The existence of four clusters is indicated by distinct colors (blue, red, green, and yellow) (Figure 7a). As seen in Figure 7b, different colors indicate varying concentrations of keyword density. The colors red, yellow, green, and blue are organized, corresponding to their density concentrations, with red indicating the highest and blue indicating the lowest density concentration. Compressive strength, rice husk ash, and concretes all exhibit red signs implying a higher concentration of density. This discovery will assist aspiring authors in choosing keywords that will facilitate the identification of published data in a certain field.


**Table 2.** The leading 20 frequently employed keywords in the research of RHA concrete.
