STIMULATING
THE USE OF SECONDARY MATERIALS IN THE CONSTRUCTION INDUSTRY: THE ROLE OF
CERTIFICATION
R.J. van Eijk and
H.J.H.Brouwers
Department of Civil Engineering and
Management
In the
period from 1960 till 1980 the production of waste materials increased
dramatically in the
In the
construction industry large amounts of materials are used which are generally
from the environment. Examples are soil, clay, sand and rocks. Alteration of
landscape (digging and dredging) also produces large amounts of material that
has to be dealt with. Finally, used constructions are demolished, producing
large amounts of waste. The destiny of all these materials may be reuse,
disposal or burning. Burning or treating waste will result in new and other
waste products.
The
Primary
materials are raw materials extracted from the natural environment and used in a
production process for the first time. Secondary materials are materials that
are released during industrial processes and used again in a new production
process. Replacing primary materials with secondary materials could save natural
resources and contribute to a sustainable society in which material life cycles
as much as possible. Both the Dutch government and Dutch industry stimulate this
policy of sustainable development and executed technical research and example
projects in order to find new treatment techniques and ways of usage of
secondary materials.
As a result
of the environmental policy and the increasing availability of waste treatment
techniques, the construction industry is confronted with the availability of
secondary materials that can be used as an alternative for traditional primary
materials. The interested parties on this market may act both as supplier (e.g.
demolisher or dredger) and as the user (constructor) of the new building
material.
However, even when the
secondary material satisfied all necessary product demands and leaching
conditions, this has not always been sufficient for a successful market
introduction. All aspects that could influence a successful introduction on the
market can be categorized into three items:
·
policy (governmental
and industrial)
·
material properties
(physical and environmental)
·
commerce (financial and
image related)
The requirements for a
successful introduction of secondary materials in the construction industry will
be explained below based on these three aspects.
Recently in the
There is a difference
between the roles of government and industry concerning the introduction of
secondary materials (Van Eijk, 2001). When the new material is financially
attractive, its introduction and application will be developed automatically and
can be stimulated by the industry itself. When it is not financially attractive
the supplier depends on the environmental policy of its customer but even then
this is not always sufficient for a successful market implementation. In that
case governmental influence may be necessary in order to enforce a market
implementation. In order to reach this goal the authorities have several
possibilities:
·
making the dumping of
the (waste) material costly (or even not allowed at all)
·
prohibiting or
introducing levies on the traditional primary material.
Authorities itself can
be in charge of the construction of civil objects, and in such case they play the role of customer. In that
role they can demand the use of secondary materials in the civil object.
Authorities can also initiate and be in charge of trial projects in which
secondary materials are to be used.
Solidification/stabilization
(S/S) techniques may be required in order to render a raw secondary material
into an immobilisate that can be used safely as a construction material. The
treatment costs will then be compared with the costs that would need to be made
when the material had to be transported and dumped. When S/S results in a
product that is more expensive (taking account of treatment costs and avoided
dumping costs), than its traditional alternative on the construction market its
properties should be worth the extra price (Van Eijk, 2001). Otherwise the buyer
will not consider it as a serious alternative. The extra environmental value is
often not considered as a real extra value in a commercial market like the
construction industry. Only physical material properties that differentiate it
from the traditional material will be considered as real extra values. Such
properties include a specific shape, colour or density.
A secondary material is
also a low-cost alternative when its application saves time, when its raw
material is more easily available or when its processing is more straightforward
compared to the traditional material.
In order to convince
the buyer that the secondary material is an environmentally and technically safe
product it is the task of the supplier to obtain the required knowledge about
these properties (Van Eijk, 2001). This will clarify the possibilities and
restrictions on its application. This knowledge of the product will also help in
obtaining product certification.
Introducing secondary
materials on a commercial market like the construction industry is difficult
(Van Eijk, 2001). The customer has to be convinced about the liability involved
with the product as well as the supplier. A supplier of secondary materials will
often have to deal with a negative image of his product because it is still
related to waste. Solving these problems take a lot of effort and research. When
the supplier is a small company, its limited knowledge, experience and financial
possibilities make it difficult to do research, to set-up trial projects and to
obtain certification.
Introduction of
secondary materials requires that all parties of interest will be satisfied. The
government wants to minimize environmental effects when these materials are
applied. The consumer will consider the secondary materials as a good
alternative only when its quality is assured. It is also advantageous for the
supplier when it is in a position to give his insurance to his product. All
interests can be met by a clear and unambiguous certification system (Van Eijk,
2001). When the construction material is certified, the user will also be less
worried about liability aspects during the service time of the material. Thus,
certification gives both suppliers and consumers certainty about the quality of
the material and therefore is considered to be an important step towards
successful introduction of secondary materials.
During the set-up of
the BMD the Dutch government has paid a lot of attention to the enforcement of
the rules by the local authorities (Eikelboom, 1999). Therefore certification
for building materials was introduced in the decree to improve effectiveness and
efficiency of the enforcement. Certification is a means of ensuring products are
in compliance with legal standards. All test methods have to be performed by
accredited laboratories in order to get uniform results and to ensure proper
interpretation of the test methods and a proper way of taking samples. The most
extended type of certification is based on basic characterisation tests that
have been chosen to give a general judgment. It can only be given by accredited
certification institutes. A less expensive and less time consuming acceptance
procedure results in an examination report for one specific stock of
materials.
All tests required for
certification are described in standard protocols, e.g. NEN norms. For organic
substances only maximum concentration levels in the product have been defined
(Ministry of VROM and others, 1999). For inorganic substances maximum immission
values were defined as the maximum quantities that may disperse into the soil or
surface water when released from the material. Release of inorganic materials is
measured by means of some advanced release tests: a column test (NEN 7343, 1995)
for granular materials and a diffusion test (NEN 7354, 1995) for moulded or
monolithic materials. Formulae were developed to make a connection between the
leaching results and the maximum immission values. These formulae deals with the
type of work, the way the material is used in a work and possible isolation
measures that can be taken.
When the material
contains organic levels that succeed the maximum levels it is not applicable in
any way. When immission of inorganic substances is below levels without the
requirement of isolation the material is defined as a category-1 building
material and may be applied without isolation measures. When immission levels
can only be fulfilled when isolation measures are taken, the material is defined
as a category-2 material. These types of materials have to be applied taking
into account directives for isolation, conserving and controlling of the
application. When the material cannot fulfill the immission demand, even with
isolation, it is not applicable in its present form (and dump may be the only
solution).
Roles of principal and designer
Because the principal gives the orders and because he finances and holds title in the work, he will be the party with most participation, responsibilities and interests during the construction process (ministry of VROM, 2000). He will make the final decision on whether to use secondary materials or not and thus has the power to stimulate this use or constrain it. Designers can advise about the use of secondary materials and its consequences. This advising role of the designer will have most impact when the principal does not have much experience and knowledge on constructing. In some cases it is decided that the builders will play a more significant role during the construction process. This means that they will play an advising role during the designing process and communicate more directly with principal and designer. In that role they will have more participation in the choice for secondary materials. This can be advantageous when he has good experiences working with secondary materials.
Use of materials
Traditionally the specifications of a work contain the amounts and types of materials that will be used and the builders are not allowed to deviate from it. As an alternative the principal may choose to use specifications based on performance. This means that the specifications contain more general demands and the builder has more freedom in making choices in order to comply with the requested demands and performances. With this way of working the principal can set environmental demands, e.g. the use of a minimum amount of secondary materials. The Dutch government ordered the building of many road constructions and promised additional payments to the builders if they used secondary materials.
The builders will have to deal with proper
application of building materials. For example they must obey the rules relating
to isolation, control and monitoring when using category 2 building materials.
Also, they must observe the rule governing removal, in other words they must use
the material in a manner that allows it to be removed.
The principal is responsible for the quality
and environmental impact of the work they order to build and must take all
necessary measures in order to fulfil these demands (ministry of VROM, 2000).
The principals must record or have recorded all information on the chemical
composition and leaching behaviour of building materials, which are covered by
the BMD. He must keep this information available and is sometimes required to
furnish the information beforehand to the empowered authority. He is also
required to ensure that any rules governing use (e.g. isolation measures) are
complied with. Therefore he will demand that suppliers, builders and sometimes
even designers will show him this information. In order to prevent
misunderstandings during the construction process, it may be necessary that the
principal makes clear to the builders what rules are to be complied with and
exactly what types of information they require for his duty of information (e.g.
a recognised approval or a batch inspection). Thus, although the principal must
provide the authorities with information, actually the suppliers or builders
will supply the requisite information. This information will proof that batches
of stony material or earth that will be delivered satisfy the quality
requirements of the BMD.
Obtaining product
knowledge, setting up the proper certification procedure and finally introducing
a secondary material on the market is difficult, time consuming and expensive.
In order to overcome these problems some parties of interest in the
Powder coal
fly ash is the remaining product from the burning of powder coal in power
plants. Both industry and government agreed that dumping of this material should
be prevented. The Dutch coal power plants founded the Fly Ash Union, an
institute that was given the task of implementing and sustaining sales of fly
ash to the construction industry (Anonymous, 1997, Cornelissen and Jenners,
1998). The collaboration between the suppliers (coal power plants), customers
(cement manufacturers and concrete companies) and government, led to financial
advantages required for research and certification. A certification procedure
was set up that fulfilled the demands of all parties of interest. As a result of
this collaboration Dutch powder coal fly ash is now reused for 100 % and applied
successfully in the cement and concrete industry. In the Table below the reuse
percentages of other European countries are given, showing that the Netherlands
is the only country where fly ash is reused for 100% (Cornelissen and Jenner,
1998). If this is due to certification is difficult to say, because availability
of primary materials and space for dumping of waste differs significantly from
country to country. On the other hand, the Netherlands is the only country in
the list, where the government and the construction industry closely
collaborated and now exchange clear information and publications related to
certification (ministry of VROM, 2000).
Table 1:
Reuse of fly ash
|
Country |
Percentage of produced fly
ash that is
reused |
|
Netherlands |
100 |
|
Germany |
95 |
|
Belgium |
95 |
|
United Kingdom |
40 |
In the
Netherlands the government allows the co-combustion of maximum 10% of secondary
fuels (sludges, waste wood etc.) together with coal. A technical research
program has revealed that the resulting fly ashes to be conforming to powder
coal fly ash, enabling the reuse of these fly ashes as secondary material as
well (Lamers et al. (2000)).
In 1998 a
Center for Immobilization was founded in the Netherlands (see
www.immobilisatie.nl). Members of this center include producers of
immobilisates, waste disposers, research and knowledge institutes, governmental
institutes and the cement industry.
The main task of this center was performing an active and substantial
contribution in canceling obstructions for application of secondary materials.
The center combines knowledge and experience from industry and authorities and
acts as discussion partner for all parties of interest. It gives information
about technical and legislative possibilities and restrictions for applying
secondary materials. It is also involved in research and setting up/improving
legislation, certification procedures and tests.
For market introduction
of secondary materials many problems need to be overcome. A successful market
introduction depends heavily on certification and dealing with the interests of
all involved parties. Best results can be expected when authorities,
suppliers and users of the new material collaborate by consulting each other
about technical aspects and their demands concerning the product. Collaboration
between suppliers makes joint investments possible in order to obtain
certification and enhance knowledge about their product. When certification
procedures are set up in dialogue with all parties of interest, they will
satisfy demands of both government and customer and be clear for the
supplier(s). On the other hand, when the certification procedure and values are
determined by governmental parties only, i.e. without any consulting, this can
even result in procedures that are not supported by the involved users or that
are impossible to comply with. In that case, certification can even result in a
limitation of the application possibilities instead of an improvement.
In some cases it can be useful to establish an
institute that is responsible for preparation and implementation of the sales of
the secondary material. This institute will execute research, certification and
contribute to a good image of the product.
Collaboration between suppliers will stimulate
the idea that the supplier is a good and reliable trading partner for the user.
When market introduction has been successful the same institute can take care of
continuous delivery and quality of the material.
Anonymous
(1997), Year results NV GKE 1997, Vliegasunie, The Bilt, Netherlands (in Dutch)
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