{"id":19749,"date":"2025-12-13T14:28:14","date_gmt":"2025-12-13T13:28:14","guid":{"rendered":"https:\/\/www.darda.de\/?page_id=19749"},"modified":"2025-12-13T14:28:14","modified_gmt":"2025-12-13T13:28:14","slug":"melting-point","status":"publish","type":"page","link":"https:\/\/www.darda.de\/en\/knowledge\/melting-point","title":{"rendered":"Melting point"},"content":{"rendered":"
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The melting point describes the temperature at which a solid transitions into the liquid state. In the context of concrete demolition, special demolition, rock excavation, tunnel construction as well as building gutting and cutting, this term has particular significance: it helps classify materials, processes, and risks\u2014especially when comparing thermal methods with mechanical, cold<\/em>-working applications using tools such as concrete pulverizers<\/strong> or hydraulic rock and concrete splitters<\/a> by Darda GmbH. Whereas thermal methods heat material up into the melting range, hydraulic cutting and splitting processes rely on pressure and shear rather than heat\u2014with clear effects on operational safety, structural element behavior, and tool wear.<\/p>\n

Definition: What is meant by melting point<\/h2>\n

The melting point<\/strong> is the temperature at which a crystalline solid, at a defined pressure (usually 1 bar), is in equilibrium with the liquid phase. Upon reaching this melting temperature, latent heat<\/em> (heat of fusion) is absorbed without the temperature rising further during the phase transition. Pure metals have a sharply defined melting point; alloys often show a melting range<\/em>. Amorphous substances such as glass, bitumen, or many plastics do not have a distinct melting point but exhibit softening or glass transition ranges. For rocks and concrete, a clear melting point is likewise not given, as these are multi-component and composite systems with different thermal decomposition steps.<\/p>\n

Physical fundamentals and influencing factors<\/h2>\n

The melting point depends on several factors. Pressure usually changes it only moderately (at the pressures relevant here), impurities and alloying elements often lower it (eutectic), and the microstructure (grain size, precipitates, pre-treatment) influences transition ranges. Thermal conductivity, heat capacity, and thermal expansion determine how quickly a component is locally heated and whether thermal stresses arise. In the practice of demolition and deconstruction, process heat mainly results from friction at cutting edges, pressing faces, and reinforcing steel contact surfaces as well as from energy conversion in the hydraulic system\u2014well below melting temperatures, but relevant with respect to tempering colors, loss of hardness, and wear in tool steels.<\/p>\n

Significance of the melting point in concrete demolition and special demolition<\/h2>\n

In concrete demolition, concrete and rock are typically broken brittle<\/em> and not melted. Here, the melting point serves more as a reference parameter to assess thermal risks and material behavior: reinforcing steel has melting temperatures far above what mechanical methods can reach. If high friction is nevertheless involved, local heating can affect tool cutting or jaw zones. Mechanical methods with concrete pulverizers<\/strong> and hydraulic splitters<\/strong> act purposefully without significant heat input, minimizing thermal microstructural changes in the component and sparks\u2014an advantage for safety, especially in special operation<\/em> and on contaminated structures.<\/p>\n

Concrete pulverizers: controlled separation without melting<\/h3>\n

Concrete pulverizers generate high compressive and shear forces to crush concrete and cut reinforcing steel. The material remains in the solid state; the phase transition does not act as the operating principle but only as a safety and material limit. The key is limiting frictional heat so that the cutting-edge hardness is maintained and no tempering zones form.<\/p>\n

Hydraulic splitters: brittle fracturing instead of thermal separation<\/h3>\n

Hydraulic splitters use controlled tensile and compressive stresses to initiate and propagate cracks. The melting point of the mineral phases is theoretically present but practically irrelevant here, because the process operates far from thermal methods. More relevant are crack propagation, notch effect, and the stress state within the material.<\/p>\n

Material properties: steel, concrete, and rock compared<\/h2>\n

For planning and evaluating separation strategies, it is helpful to know typical temperature ranges:<\/p>\n