Heated fresh concrete: A report from Finland

Since the early 1980s, the use of heated concrete mixes has increased in Finland. The properties and uses of 'hot concrete' (the term most commonly used) have been studied both in the laboratory and on building sites. Hot concrete is a useful method in winter concreting for it makes possible a rapid turnover of forms. For concrete to gain rapid demolding strength in winter, delays in concreting should be avoided; the concrete should be protected early with heat insulation, and additionally heated at the edges of the structure. Construction work demands a rapid turnover of concrete forms in all seasons. During winter, concrete needs to be heated efficiently for a one- to three-day turnover of forms. Heating concrete has traditionally been carried out after concreting, but it is also possible to heat components to the mix, or the mix itself, during mixing. This heated concrete mix is usually called hot concrete. The author examines the preparation and properties of the mix, the use of hot concrete, measurements of concrete temperature for large molds, and placing of thermocouples.