## 1 Introduction
### General Facts on Compressive Strength Estimation
For example, basalt can be considered to be a high-quality aggregate due to its high density and high mechanical strength, but its bond with the cement paste may be not strong enough due to its very smooth texture which is relatively similar to that of glass [11]. Thus, the calculated strength may be overestimated. In terms of chemical reactivity, the study of [PERSON] and [PERSON] [11] showed that the amount of OH\({}^{-}\) that is absorbed by the aggregates and that releases Si\({}^{4+}\) at the same time depends on the geological nature of the aggregates, and this process significantly affects the pore structure of the hydration product and the ITZ as a result. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Aggregate Class**} & \multicolumn{3}{c}{**A**} & \multicolumn{3}{c}{**B**} & \multicolumn{3}{c}{**C**} & \multirow{2}{*}{**D**} \\ \cline{2-2} \cline{4-2} \cline{6-9}  & **I** & **II** & **III** & **I** & **I** & **III** & **I** & **II** & **III** \\ \hline Minimum over-dried density (kg/m\({}^{3}\)) & 2600 & 2500 & 2400 & 2300 & 2200 & 2100000 & 1900 & 1800 & \\ Maximum water absorption (\%) & 1.5 & 2.5 & 3.5 & 5 & 6.5 & 8.5 & 10.5 & 13 & 15 & No limit \\ Maximum LA abrasion mass loss (\%) & 40 & & & 45 & & 50 & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Physical boundaries for each proposed class of aggregates [7]. Therefore, this study attempted to show the effect of the geological nature of the aggregates on the ultimate strength of concrete and how the scatter between the estimated and the actual strength of concrete decreases if the results take the geological nature of the virgin aggregates into account. Generally, the geological nature of aggregates affects the ultimate strength of concrete in different ways. When the strength of aggregates is lower than that of the cement paste, the quality of the aggregates controls the ultimate strength, because failure occurs though the aggregates. However, when the strength of the aggregates is higher than that of the cement paste, failure may not only occur in the cement paste itself but also in the ITZ between the aggregates and the cement paste [13]. In fact, the quality of the aggregates needs to be considered a main factor in the estimation of the compressive strength for low and high strength concrete mixes. It is well known that failure normally occurs in the ITZ between the aggregates and the cement paste because the effective water to cement ratio (\(w/c\)) of the cement paste around the aggregate particles is higher than that of the other parts of the cement paste [14]. This phenomenon relates to the capillary absorption between cement paste and aggregates which is affected by the WA and density of the aggregates. Since the effect of SP, binder content and its characteristics, the \(w/c\) and aggregate content and the parameters described in [15; 16] on concrete have already been studied, this study focuses on the effects of the quality and geological nature of NA on the compressive strength of concrete when all the mentioned parameters are constant, mainly by considering two modified models shown in the next sub-section. Thus, in terms of the aggregates, it is advisable to focus on the two mentioned parameters rather than only on the source of the aggregates, e.g., NA versus RA. To that purpose, this study considered the results of 84 publications for concrete made with virgin aggregates and 41 other publications (Section 2) for concrete made with RA.