The determination of the mineral composition of aggregates which constitute an important component of concrete is essential to understand and estimate the durability of structures. The modal (quantitative mineralogical) analysis of rocks is generally determined by point-counting method on thin sections or slabs. However, there is a difficulty of mineral identification depending not only on the experience and capability of the operator but also on the size of observable grains. In this study, XRD (X-Ray Diffraction)/Rietveld analysis is proposed as an alternative and a comparison study is performed for eight different rocks. The results show equivalent proportions to those of the point counting method for the major phases (minerals), although discrepancies are observed for the minor minerals. Complementary tests as XRF (X-Ray Fluorescence) and density measurements are also performed to pre-characterize and confirm the obtained modal analysis. For instance, the density calculations based on XRD/Rietveld analysis provide close values to the measured densities. Overall, this method can be an excellent alternative to the point counting method especially in the context of construction materials laboratory.

确定构成混凝土重要组成部分的集料的矿物成分对于理解和评估结构的耐久性至关重要。岩石的模态（定量矿物学）分析通常是通过对薄板或平板上的点计数方法确定的。然而，不仅取决于操作者的经验和能力，而且取决于可观察到的晶粒的尺寸，存在难以识别矿物的困难。在这项研究中，提出了XRD（X射线衍射）/ Rietveld分析作为替代方案，并对8种不同的岩石进行了比较研究。结果表明，与主要矿物相（矿物）的点计数方法相同的比例，尽管在次要矿物中存在差异。还进行了补充测试，如XRF（X射线荧光）和密度测量，以预先表征并确认获得的模态分析。例如，基于XRD / Rietveld分析的密度计算提供了与测得的密度接近的值。总体而言，此方法可以作为点数计算方法的极好替代方法，尤其是在建筑材料实验室的情况下。