Rubber Asphalt

@Carl-Zide Here is a short podcast in Swedish about the project.

Chromium 6 (Cr6) is an important factor when recycling concrete. Elisabeth Helsing at Rise concludes in a recent article in Bygg & Teknik that the chromium 6 varies depending on:

• lower pH = leaching risk of Cr6 is tenfold when pH decrease from 12.5 to between 8-11

• higher carbonatization (due to porosity/smaller fraction size/aging etc) = increased leaching risk

Ways of decreasing leaching risk could be:

• to use ground granulated blast-furnace slag GGBS in the concrete.
• remove other conatminated materials from the concrete before recycling
• wash the concrete using a wet process
• covering the concrete aggregates under crushed rocks, asphalt or other types of isolation

Further reading:

• Article 2020-11-26 Bygg & Teknik Vad händer med sexvärt krom i återvunnen betong? (print version)

• Report 2019 RISE Krom i krossad återvunnen betong

What other methods do we have to decrease the risk of chromium 6 leaching?

Excess materials and other biproducts from construction and demolition projects are transported, sold, recycled and reused by numerous different companies.

1. Construction companies, contractors and haulages
   The largest part of the secodary market is managed by the companies involved in the generation of excess materials. The reuse of materials is usually limited to "clean" materials (mindre än ringa risk). Examples of companies: Peab, NCC, Svevia, Veidekke, Skanska, Sveab, NKR Demolition, Destroy, Märsta Förenade, Bellmans, ABT-bolagen etc.

2. Recycling companies, quarries and terminals
   Another large actors are specialised of different types of fairly clean materials. These companies usually crush or sort part of the materials. Examples of companies: Swerock, ABT-bolagen, Märsta Förenade, Veidekke, Skanska, DA Mattsson, Hans Andersson, Hummeltorp, RGS etc.

3. Landfills
   Landfills usually do not ever resell the material received. They receive all types of materials including completely clean material to hazardous waste. Examples of companies: Ragn-Sells,

4. Brokers
   Brokers of materials are primaily focused of matching excess supply and demand for "clean" materials (mindre än ringa risk) between different construction companies. The brokers usually add different types of quality tests in addition to brokering the deal. Companies includes: Massbalans, Massoptimering, Avfallspartner etc.

5. Market places
   Markets places are trying to match supply and demand by some sort of open or semi-open market place. The largest one in Sweden was previously Loop Rocks with over 18 000 registrered users, that site is no longer active. Companies today include: Massabyte, CCBuild, Pinpointer, Fleety etc.

Please suggest other companies and categories.

The first report from a project to create scientifically based environmetal risk assessment tools was just published. The goal of the project is to create an easy to use tool for risk assessment when you apply for a registration to use recycled materias with slighty higher pollution levels (ringa risk according to the Swedish regulation). Today, each local municipally have the ability create their own local risk assessment models which is highly detrimental for the use of recycled material in Sweden.

The project was financed by SBUF and more about the project can be found on their website. The report can be downloaded here. The report is written in Swedish.

Other similar reports in Sweden includes a risk assessment model for soil material from road ditches from Trafikverket (the Swedish Transportation Agency) and a similar report about bottom ash recycling in road construction from Avfall Sverige (the municpal waste management and heating companies).

The next step in the project to create a scientific risk assessment tool is to gather knowledge about the correlation between total content and leaching values for different materials. If suceessful we will be able to approximate the envrionmental risk for certain materials based only on total content levels.

Do you have any input and suggestions for the upcoming new projects?