Waste reduction final report -4 - Test Input

study mentioned before claims that there have to be a certain amount of material illegally
dumped or backfilled. It says that this can be supposed as a result of mass balances.
Some of the waste materials are discussed in the following parts. On the one side, these are
important materials in view of needed amounts, furthermore there are presented materials
with a great potential for recycling in future and finally, the discussion will be hold on an
exemplary case for a material not mentioned until now in this report.
Concrete
Concrete is a mixture of aggregate (gravel), water, cement, additives and other chemical
admixtures. The definition of recycling concrete as to SN EN 206-1 (2000) includes a
minimum of 25 % in weight of recycled concrete aggregates and/or recycled mixed
aggregates [SNV 2000]. Secondary concrete can therefore be made out of concrete
demolition, mixed mineral debris or asphalt. In Switzerland, recycled asphalt conrete and
concrete made of concrete are widely accepted. In contrast, secondary material out of mixed
C&D waste still does not have a good reputation on the market due to strongly unsteady
properties (see section below). Another issue is that life cycle assessments (LCA’s) have
shown the secondary concrete does not improve environmental impacts (especially for CO 2
emissions) much if at all, so that this incentive drops out for companies (“greener”
products/production). The crucial points for CO 2 emissions in (recycling) concrete production
are the type and amount of cement. Furthermore, type and distance of transport have a big
influence on environmental performance [Kytzia 2009, TUM 2006]. A positive result of
those LCA’s proves the durability of recycling concrete to be as high as of primary material.
Furthermore, the use of waste as resource helps to protect valuable soil resources.
On the economic side, the price for recycling concrete is equal or higher than the one for
primary concrete. However, on the long term, secondary materials could become cheaper
than primary materials, depending on technologies and fees for waste conditioning or
landfilling. All in all, [Dosho 2008] concludes that encouragement of the use of recycled
aggregate concrete needs to secure a good balance between (a) safety and quality, (b)
environmental impact, and (c) cost effectiveness.
Recycled mixed aggregates
As a special case of concrete raw material, recycled mixed aggregates are presented in this
section. Recycled mixed aggregates can be made out of bricking and/or out of mixed mineral
materials. As long as materials can’t be separated in a proper way, recycled mixed aggregates
would ostensibly be a very good solution to prevent landfilling. However, only estimated
20% of bricking and mixed mineral waste is recycled. Even if there are other unrecorded
uses, a big amount of these materials is still landfilled.
Recycled mixed aggregates are not well accepted in the industry because of several properties
listed below [Hoffmann 2005]:
- Gypsum, fine materials or other materials are not desirable in recycled mixed aggregates,
but today can’t be avoided in many cases.
- Composition of the granules fluctuates much and therefore the properties of the material.
- Because of a high amount of non-cubic aggregates, cavity is higher and therefore the
need of cement increases. The same is valid for water absorption.
- The more mixed mineral debris, the lower is the modulus of elasticity. As compressive
resistance remains the same, a higher distortion results.
- Shrinking is twice as high as for primary gravel.
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