Sand from the Rocks for Concrete Production

Aggregates Processing

Sand from the Rocks for Concrete Production

New Type of Crushed Sand to replace natural Sand in Concrete Production
The availability of natural sand for concrete production is facing challenges, while the so-called waste stockpiles at aggregate crushing areas are causing problems for producers. This means that the industry has a huge need to solve this challenge by finding suitable technology for usable crushed sand production.
(ed. WoMaMarcel - 24/9/2015)
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The air-classification experiments with the 10 different materials are now finished. The results demonstrated that the classification process of the equipment can be successfully adapted to a narrow desired result by adjusting the classification process parameters, i.e. the air-flow, which is regulated by the main air inlet valve and adjusted by the secondary air inlet valve (primary and secondary air ratio).

The success of the experiments can be illustrated (see Figs. 5 - 7) by the initial gradings of filler from all 10 crushed sands after the first stage of classification, an example of classification results (when the filler part is distributed into separate fractions), and the possibilities of recombining those fractions if one of the initial gradings is chosen as the reference.


Fig. 5: The intrinsic gradings of fillers from all 10 crushed sands after the first stage of classification with a GI air-classifier. The apparent “bump” of the curves at 100 µm is an artefact of the PSD measurement method used.

Fig. 6: Example of the complete air-classification results (0/2 mm feed split into 0.125/2, 0.063/0.125, 0.020/0.063 and 0/0.020 mm fractions) for quartzite material.

Fig. 7: Recombining the achieved fractions if one of the initial gradings (quartzite) is chosen as the reference; a very wide range of other curves can also be achieved with the same accuracy. The apparent “bump” of the curves at 100 µm is an artefact of the PSD measurement method used.

The acquired filler fractions have now been delivered to the Norwegian University of Science and Technology where work within the COIN project will continue with the further elaboration of the knowledge on how the different filler characteristics affect the properties of fresh concrete.

Crushed Sand Application on the Aggregates Market

As described above, already today a technology for producing high quality manufactured sand that would be acceptably similar to that of the natural origin or at least “good enough” is available. Even though it is not always straight forward and not all the rocks can be classified as equally suitable for that, the questions for the future still are- can we make the manufactured sand even better than the natural, how, and, last but not least, why? An attempt to answer the first two parts of the question was given above in the article. If continuing with the last part of the question: aggregates constitute up to 75% of the total volume in concrete, while their price is second from the bottom, normally only water being less expensive. The aggregate prices in many places do not even keep up with the inflation, the only exception being natural sand, in some cases.

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