Classification of common rocks from gravel sources
Since 1990s, with the rapid development of highway construction in China, the related research on pavement performance has been deepened, focusing on the changes of pavement structure and asphalt performance, with remarkable results. However, whether it is the change of pavement structure or the modification of asphalt, the cost of pavement will increase greatly accordingly. Asphalt pavement is a combination of asphalt and mineral materials through certain physical and chemical actions, and the performance of stone materials will greatly affect the performance of pavement. Several common rocks are classified as follows:
1) basalt: basic ejected magmatic rock, with low water absorption (below 0.5%), high ultimate compressive strength (above 294~392MPa), strong frost resistance and weathering resistance. Because of its high mechanical strength, it is widely used in asphalt pavement surface of high-grade highway, but it is difficult to mine, roll and process.
2) Diabase: composed of basic plagioclase and augite, with low water absorption (0. 1%~0.4%), high ultimate compressive strength (196~29MPa) and wear rate less than 3%. Because of its high mechanical strength and good technical performance, it is also recommended by Technical Specification for Highway Asphalt Pavement Construction (JTJ03-94), but it is difficult to mine, roll and process.
3) andesite: jetted magmatic rock, with lighter specific gravity than basalt, ultimate compressive strength 1 18~294MPa and good mechanical properties, is widely used in asphalt pavement surface of high-grade highway.
4) Limestone: Pure limestone is composed of calcium carbonate, with light specific gravity, low strength and large porosity. The mechanical properties of limestone from different producing areas are very different, so limestone is mostly used for asphalt pavement base of high-grade highway or low-grade pavement.
Engineering classification of rocks
(1) is divided into:
Hard rock: the uniaxial ultimate compressive strength of rock specimen (specimen diameter 7~ 10CM, same height and diameter) under saturated humidity is greater than 29. 4X 103KPA, such as granite, diorite, basalt and other magmatic rocks; sedimentary rocks such as iron-calcium cemented conglomerate, sandstone, limestone, argillaceous limestone and dolomite; Metamorphic rocks such as gneiss, quartzite, marble and slate.
Soft rock: the uniaxial ultimate compressive strength of rock samples under natural humidity is 4.9x103-29.4x103kpa, such as suspected magmatic rocks such as limestone and pumice; Mud conglomerate, argillaceous shale, argillaceous conglomerate, marl, mudstone and hard rock, the strength is reduced to 4.9x103-29.4x103kpa after weathering.
Extremely soft rock: the uniaxial ultimate compressive strength of rock samples under natural humidity is less than 4.9x103-29.4x103kpa, such as clay rocks, coal and other sedimentary rocks; Metamorphic rocks such as mica schist or phyllite, and other rocks whose strength is reduced to below 4.9x103-29.4x103kpa due to weathering.
(2) According to its crushing degree, it can be divided into:
(a) Block-most of the rock mass is divided into blocks over 40 cm;
Broken-most rock masses are divided into 20-40 cm pieces;
(c) Gravelly-most of the rock mass is divided into 2-20cm blocks.
(3) Gravel
The water chestnut stone with rough surface made by crushing and sieving rocks is one of the most widely used materials in road construction factories and the main research object of this book. It is mainly used as coarse aggregate of cement concrete or asphalt concrete in road construction projects.
Gravel can be divided into coarse gravel, medium gravel, fine gravel and stone blood according to its particle size. The particle size range of crushed stone is usually 5-5-100 mm (rock fragments smaller than 5MM are artificial sand or stone powder), but there are many regulations according to different engineering objects. In highway engineering, due to different purposes, the specifications of gravel used are also different.