Results of measurements of the absolute spectral sensitivity of silicon semiconductor detectors for 7–20 keV x rays are presented. Synchrotron radiation from a 2-T wiggler, installed at the VEPP-3 storage ring, was used for this study. Two quite different approaches were applied to measure the detector spectral sensitivity. According to the first approach, the measurements were performed in monochromatic radiation. The absolute photon flux was determined by a scintillation counter with known detection efficiency and monitored by a transmission ionization chamber. The second approach corresponds to the measurements in a ‘‘white’’ synchrotron radiation beam through sets of known absorption filters and via the following unfolding of the spectral sensitivity from a set of integral equations. The experimental results obtained by both procedures are in good agreement. The accuracy of the experimental calibration procedures is assumed to be not worse than 10%.

48 concentrates, is of significant scientific and practical interest, and resolving it is a relevant task. 2. Literature review and problem statement Concrete, according to [1], represents the poly-structural system "matrix-filler-their interface", in which cement stone is the matrix. At the same time, cement stone is a hydration product of the dispersive system "dispersed phase-dispersion medium" in which the dispersed phase is the binder's particles and the dispersion medium is water or aqueous solutions of chemical substances. The structure of the cement stone, according to [2], is determined by the shape and content of hydrated compounds. As well as by those grains that did not react, by the volume and size of pores, including technological cracks [1],

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