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The distinctive feature of the contemporary U. S. approach to production control is the application of statistical methods and fines as punishment for exceeding admis­sible limits or deviations from the mix design. (Sometimes bonuses, or incentives, are also used to reward exceptional production consistency, but penalties are more common.) The quality control methods widely employed […]

The SMA mixture production process, like that of other asphalt mixtures, is subject to procedures to control its mixed components and other selected properties. These procedures differ among various countries, but in almost all cases, the control of gradation and binder content form their common root. The control of the production process mostly consists of […]

Most guidelines for SMA do not recommend producing large quantities of a mix­ture and holding it in reserve for too long for future use. SMA stockpiling is an uncertain business due to the risk of binder draindown when storing hot mixture. Such limitations cause problems when the asphalt plant has a low output and large […]

SMA mixtures are very susceptible to overbatching of the binder quantity during production. When this occurs, an extra amount of binder appearing in a mixture is followed by the rapid decrease of mastic consistency and a change in the volume ratios of the entire SMA. Moreover the risk of binder or mastic draindown becomes much […]

There are two types of drum-mix plants: parallel-flow drum-mix plants and counter-flow drum-mix plants (conventional and double barrel). In drum-mix plants, cool aggregate is delivered from cold-feed bins to a dryer-mixer and then into a silo through a slat conveyor. The mixture gradation control is exercisedthrough establishing suitable proportions of individual aggregate fractions in cold-feed […]

The KGO-III (Viman et al., 2004) method has been experimentally applied in Sweden since 2002. It consists of changing the order of batching and mixing the constituents in a batch plant. The suggested KGO-III mixing order is as follows: FIGuRE 9.5 One sequence of batching SMA constituents into a pugmill using a loose form of […]

When incorporating a loose stabilizer, which is usually packed in shrink-wrapped bags, extra time is needed for dry mixing the stabilizer with aggregate. A bag of stabilizer is thrown into the pugmill when the filler is being batched, and then an extra period (about 3 seconds) of dry mixing the fibers with the aggregate follows. […]

There is a widespread opinion among a large body of practitioners in the field of SMA production that, after all, the sequence of mixing should vary, depending on the kind of stabilizer. In the case of a granulated stabilizer, this is typically batched with the filler and then mixed with the aggregate without any special […]

Establishing the sequence of putting materials into the pugmill is chiefly aimed at securing the final homogeneity of a mixture. Mixing constituents consists of the fol­lowing two stages: • Dry mixing—this starts the moment the aggregate is deposited into the pugmill, and it ends the moment the binder batching starts. • Wet mixing—this starts the […]

Mixing the components of a bituminous mixture, proportioned by weight from hot — bins, in a batch asphalt plant takes place in a pugmill. Contemporary batch plants have pugmills of various sizes, usually from 1 ton to 8 tons. Despite the different sizes of pugmills and the resulting output of the plants, mixing time, by […]