# Effect of Aggregate Size on Recycled Aggregate Concrete under Equivalent Mortar Volume Mix Design
###### Abstract  
In this paper, the effect of the original aggregate size of the recycled aggregate on the mechanical properties of the recycled aggregate concrete was evaluated. A series of concretes were produced in which natural aggregates, recycled aggregates, and original aggregates in recycled aggregates were matched for a single particle size distribution curve. The replacement levels of recycled aggregate were 25% and 50%, and equivalent mortar volume mix design was applied for recycled aggregate concrete. The results show that the mechanical strength of recycled aggregate concrete increases with increasing original aggregate size. This effect was observed to be greater in concrete using recycled aggregate with a high residual mortar content. recycled concrete aggregate; original aggregate; recycled aggregate concrete; concrete mix design; equivalent mortar volume; aggregate size; particle size distribution +
Footnote †: journal: Applied  
**Citation**: [PERSON]; [PERSON]; [PERSON] [PERSON] Effect of Aggregate Size on Recycled Aggregate Concrete under Equivalent Mortar Volume Mix Design. _Appl. Sci._**2021**, _11_, 11274. [[https://doi.org/10.3309/appr112311274](https://doi.org/10.3309/appr112311274)]([https://doi.org/10.3309/appr112311274](https://doi.org/10.3309/appr112311274))  
Academic Editor: [PERSON]  
Received: 19 October 2021  
Accepted: 26 November 2021  
Submitted: 28 November 2021  
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feasible [16]. This is because recycled materials used as alternative aggregates have different physical and chemical properties from NA, which is one of the necessities of extensive research on recycled materials. When NA is replaced by RCA, the concrete matrix becomes more complex. RCA is composed of original aggregate (OA) and residual mortar, and the residual mortar is the fundamental cause of the poor quality of RCA than that of NA [19]. It has been shown that the amount of residual mortar depends on the grain size of RCA [20,21]. According to [22], in the coarse fractions, 10-20 mm, the habitual values range between 23-52%, whereas in the finer fraction, they can ascend up to 32-61%. In this context, grains of different sizes then have different effects on the properties of the new concrete. In the literature [23], compared with the corresponding parent concrete, the strength reduction in recycled aggregate concrete (RAC) with the maximum RCA size of 10 mm was 20-35%, and as for RCA sizes of 20 mm and 40 mm, the strength loss was 14-35% and 10-25%, respectively. The authors of that study concluded that a smaller maximum size of RCA resulted in a greater reduction in the strength of RAC due to an increase in the amount of old residual mortar present in RCA. [PERSON] et al. [24] measured the compressive strength and tensile strength of concrete using RCAs with maximum aggregate sizes of 9.5, 19, and 31.5 mm. The results showed that RAC with a maximum aggregate size of 19 mm had the highest strength, and RAC made with a maximum size of 31.5 mm had the lowest strength. On the other hand, [PERSON] et al. [25] reported that smaller aggregates made concrete about 10-15% stronger. Moreover, [PERSON] et al. [26] stated that smaller sized aggregates are preferable to design durable concrete. According to the above literature review, the effect of the RCA size on the properties of concrete seems ambiguous, thus, more research is needed in depth. This may be associated with the fact that the increase in the RCA size includes both favorable (e.g., enhanced RCA quality) and unfavorable factors (e.g., increasing ITZ and heterogeneity in RAC matrix) to the properties of concrete. Residual mortar unfavorably affects RCA quality and performance of RAC. Recently, several researchers have reported that the properties of RAC can be improved by applying an appropriate mix design for RAC called the equivalent mortar volume (EMV) mix design [18,27,28,29,30,31].