Gypsum reduced

Gypsum constituents in recycled concrete – origin, effects and removal by jigging, part 2

Installation plan for the Triple A wet jigging machine from AGS Anlagen und Verfahren GmbH

Experimental rig for testing the jigging process a General view of the test set-up

View inside the jig bed

Light material discharge onto the dewatering screen

Particle size distributions of the starting materials for the jigging trials

Building material from the bath cubicles

Diagram showing the sequence for the sample assessment and the methods used

Mass balance calculated as average values from the results of the machine setting trials

Changes in the levels of concrete in the product and light material as a function of the product yield at different machine settings

Changes in the levels of gypsum in the product and light material as a function of the product yield at different machine settings

Changes in the levels of gypsum in the product as a function the gypsum content in the feed material

Decrease in the amount of product generated and reduction of the gypsum content during multiple passes

Changes in the levels of gypsum and brick in the product as a function of gypsum content during multiple passes

Mass distribution of the bulk densities of the light and heavy materials, shown as relative frequency and cumulative frequency

$Changes in the levels of concrete and gypsum due to the jigging process as a function of the product yield for different particle size fractions$

Changes in the levels of concrete and gypsum due to the
jigging process as a function of the product yield for different particle size fractions

Changes in the levels of concrete and gypsum due to the jigging process as a function of the product yield for the practical mixtures

Changes in the particle size distributions of the feed materials compared with the heavy materials discharged as product –
for the practical mixtures

Summarized comparison of the levels of gypsum in the product with the levels of gypsum in the starting materials

Summarized comparison of the levels of concrete in the product with the levels of concrete in the starting materials

Sampling of the material

Wet jigging machine during the experimental procedure

Summarized comparison of the product bulk densities with the bulk densities of the starting materials

Summarized comparison of the average particle size of the
product with the average particle size of the starting material

Summarized representation of the product yield as a function of the levels of gypsum in the starting materials

Summary: Part 1 of the following article – published in AT 6/2010, p. 34-43 – discussed the structural implications of gypsum constituents in recycled concrete. The authors explain the possibilities available in mineral processing for the removal of this building material in the reclaiming of concrete rubble on the basis of a series of gypsum removal tests using jigs. Evaluation of the test results clearly shows an improvement in the quality of the recycled building material, which, thanks to the lower gypsum content, meets environmental and structural requirements and can easily be made suitable for further use.

4.2 Procedure for removing gypsum from recycled

building materials during the jigging trials

4.2.1 Test set-up

The Triple A wet jigging machine together with all the necessary accessories and supply units was installed and commissioned at the Erfurt municipal works at the building waste recycling centre in Erfurt-Schwerborn. Fig. 8 shows the structure of the plant that consists of the actual wet jigging machine, a settling container, a pump sump, a dewatering screen and a Linatex 80 pump. The jigging machine, including the peripheral equipment and some details, is shown in Fig. 9 a–c. At full...