During the crushing process, crushed stone or angular rock sometimes develops an angular and jagged edge. It is the most basic mineral on the planet. It is plentiful, easily available, and reasonably priced. It is a form of construction aggregate that is usually made by mining a suitable rock deposit and crushing the extracted rock to the desired size. It is a substance that is common to people in almost every country on the planet. Gravel, which is formed by natural weathering and erosion, differs from crushed stone in that it has a more rounded shape.
Just a few naturally occurring materials possess the properties needed to serve as an in-kind substitute for aggregate. In certain low-specification applications, shells, caliche (carbonate-cemented soil typical of arid areas), and clinker (rock hardened by heat from natural coal fires) can be used instead of aggregate. Crushed stone is a type of stone that contains a mixture of stone dust. When heavy compaction is needed, this form of stone is best used as a foundation. As a consequence, it’s commonly used for the foundations of homes, concrete and paving schemes, and driveway bases.
Crushed stone production in the United States reached 1.33 billion tons in 2017. For each resident, this equates to around four tons of crushed stone. Most people can’t imagine how four tons of crushed stone were used for their benefit in the previous year. For the entire year, that equates to about twenty pounds of crushed stone per person. The fractured stone is thrown into a primary crusher, which breaks the big rock fragments into smaller pieces. Since rapid size reduction achieved by applying large forces often results in the creation of unnecessary fines, crushing to the proper size is typically done in stages.
Riprap, railroad track ballast, and filter stone can all be made from crushed natural stone without the use of a binder. It can be found in a composite material like concrete, tarmac, or asphalt concrete with a binder. After primary crushing, the material is sent to one or more secondary crushers for further processing. The rock is broken into smaller parts through compression, impact, or shear in these crushers. Around 25,000 tons of crushed stone was used per mile in the construction of a two-lane asphalt highway. Around 300 tons of crushed stone are used per home in a small residential subdivision.
Despite the low value of its raw materials, the crushed stone industry is a significant contributor to and predictor of a country’s economic health. Crushed stone demand is largely dictated by the level of construction activity and, as a result, the demand for construction materials. Crushed stone is made from a variety of rock forms. Limestone, granite, trap rock, sandstone, quartzite, dolomite, volcanic cinder and scoria, marble, slate, dacite, shell, and calcareous marl were among the crushed stone forms used in the United States in 2017.
After each crushing step, the material is screened to distinguish appropriately sized particles (“throughs”) from those that require more crushing (“overs”). To remove undesirable material, additional washing, screening, or other processing may be needed. The world’s stone supplies are enormous. Many geographic areas have a scarcity of high-purity limestone and dolomite suitable for specialty applications. Sand and gravel, as well as slag, are crushed stone replacements for road construction.
The amount of processing required is determined by the sand and gravel deposit’s characteristics as well as the intended usage. If there are large cobbles or boulders in the gravel deposits, they can be crushed in a primary crusher. To extract undesirable material, the material may be run through one or more secondary crushers, then cleaned, screened, or further processed. Crushed stone is a low-value, high-volume product. The industry is fiercely competitive, with many businesses serving local or regional markets. The cost of labor, machinery, electricity, and water, as well as the costs of complying with environmental and safety regulations, determine the majority of production costs.
Crushed stone is hardly ever manufactured or exported from the United States. Imports account for less than 1% of domestic crushed stone use in the United States due to high transportation and handling costs. Crushed stone of suitable quality is locally accessible in most parts of the United States, with the exception of certain coastal areas that are underlain by a vast plain of sand rather than rock. Crushed stone shipped prices are heavily influenced by transportation costs. The cost of transporting crushed stone from the plant to the market is often equal to or greater than the product’s selling price at the plant. Crushed stone is normally sold locally due to the high cost of shipping and the large amounts of bulk material that must be transported.
Government building projects, commercial and residential development, and other forms of construction drive crushed stone demand. According to the US Geological Survey, 1.72 billion tonnes of crushed stone worth $13.8 billion was sold or used in 2006, with 1.44 billion tonnes used as building aggregate, 74.9 million tonnes for cement production, and 18.1 million tonnes for lime production. The total amount of crushed marble sold or used was 11.8 million tonnes, with the bulk of it being finely ground and used as calcium carbonate. The average cost of crushed stone at the plant site in the United States in 2012 was $9.75 per metric ton. At least 80% of the crushed stone manufactured in the United States is transported by truck from the mine. The stone’s transported cost is increased by 12 to 15 cents per ton-mile by truck transport.
4.53 million tonnes of crushed stone were also used as fillers and extenders (including asphalt fillers or extenders), 2.71 million tonnes for sulfur oxide removal-mine dusting-acid water treatment, and 1.45 million tonnes for poultry grit or mineral food. Prior to World War II, crushed stone was used sparingly because it was extremely difficult to manufacture. Crushed stone production started to increase rapidly after the invention of reliable track equipment (one of the few benefits of war). Recessions in the general economy have slowed growth, as shown in the graph by output drops of varying magnitudes.
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