Search for "Popov L.N." or the Russian title "Лабораторные испытания строительных материалов" . It is frequently mirrored here in both DJVU and PDF formats.
Since the file is in , you will need a specific reader to open it: WinDjView: The most popular lightweight reader for Windows. Search for "Popov L
Similar to Libgen, searching for the ISBN or title in Russian often yields the 1984 "Vysshaya Shkola" edition. Search for "Popov L