Temperature control of hot mix asphalt concrete is required in all plants except those producing cold mixes using bitumen emulsion. Thermometers (mercury or electric) has to be located in the flow of aggregate from the dryer, in each hot bin, and in the binder supply line. The number of thermometers used and their locations have to be such that the readings are valid indications of the material temperatures. The thermometers should have accurate to within I percent and their registrations clearly and conveniently visible to the operator.
In the production of Hot mixes the aggregate must be heated only sufficiently to obtain a mix at the required temperature. Overheating may result in damage by oxidation of the binder while it is in the form of thin films during the mixing process.
If the mix is too hot, the binder will drain from the particles of aggregate with the result that some portions of the mix may be dry and others fatty. This applies particularly to open graded mixes. See related posts of hot mix asphalt concrete for further knowledge.