Features of the Physical-Mechanical Properties and Chemical Composition of Chert Gravels

The chert gravels are a by-product of sand mining in the south of Israel; the reserves amount to tens of millions of tons and continue to grow. The attempts of their comminution for the production of aggregates by conventional mechanical methods have not yet been successful due to the high abrasiveness, as well as the flaky form of their fracturing. This study was motivated by the need to find an alternative method to rock comminution that would ensure aggregate production in line with the requirements of the asphalt and concrete industry. This article deals with the first inevitable stage on the way to this goal, which consists of an extensive laboratory study of the physical and mechanical properties of the chert gravels, as well as the features of their chemical composition. The results show that the chert rock, consisting of quartz micro grains, contains calcium, sulfur, phosphorus, and barium impurities. The rock is characterized by extremely low porosity and water absorption (less than 1%) and high values of tensile strength (10.8 +/- 3.3) and electrical resistivity (23.0 +/- 11.9 k ohm m). The cubic uniaxial compression strength of the rock is relatively not high (37.3 +/- 10.4 MPa), which contradicts the assessment made based on the Schmidt hammer and Point Load studies (158 +/- 30.4 MPa and 321 +/- 118.5 MPa, respectively).