Subject matter

A series of international standards (ISO 14040-14044) is well accepted nowadays for the assessment of environmental impacts of a product or systems, known as LCA – life cycle assessment. Its application on concrete structure is discussed in ISO/TC 71/SC 8 and a first part of a series of standards in this topic has already been published (General Principals, ISO 13315-1:2012). The procedure includes a comprehensive collection of all the inputs and outputs of materials and emissions involved in a process and the assessment of their environmental impacts. Such assessment of concrete structure requires special attention due to the large number of items to be addressed: proper definition of the functional unit, allocation of impacts regarding by-products, the large amount of materials used for concrete manufacture as well as concrete service life issues. Thus, its implementation can create a large variability between simulations.

To do so, the future TC will focus on the three first steps of the Life Cycle Analysis as listed in the international standards: 1) definition of the aim and scope of the study, 2) gathering data for the Life Cycle Inventory and 3) conversion of this inventory into environmental impacts.

1) For the first step of the LCA, the TC will mainly focus on questions related to the system boundary definition. The system boundaries of the study comprise the whole concrete structure; however, one of the objectives of the study is to precisely define the most appropriate system boundary for a correct environmental evaluation. When performing an environmental comparison between two products it is imperative to compare products that can provide the same functional requirement (same strength, durability, workability,…). In this committee, we will look in detail at the sensitivity of the results to varying system boundaries.

The estimated service life of the concrete structure when exposed to harmful substances in situ, is considered as one of the most crucial inputs to a valid sustainability assessment. In this TC, we will evaluate the consequences, in term of LCA, of durability differences between concrete types rather than on service life studies. To do so, it is expected to have members in the TC that are experts on concrete durability and use the results from other TC focused on concrete durability (e.g. 213-MAI: Model assisted service life prediction…, 238-SCM: Hydration & microstructure of concrete with SCM, 230-PSC: Performance-based specifications of concrete durability or TC-DTA: Durability testing of alkali-activated materials).

The boundary of the studied system will not include the thermal performance of buildings. As mentioned above, the focus of the committee will be on concrete structures and not full buildings. Thus, as long as heavy structure is involved, the thermal difference between various options is assumed to be negligible.

The future committee will focus on the environmental impact of concrete structures based on the principles listed in ISO 14040-14044 as well as the future ISO standards made under the ISO/TC71/SC8. The objective of this future committee is to highlight the main parameters which have a critical influence on the results and are therefore fundamental to pay attention to during an environmental evaluation. This TC will allow strengthening the LCA results of in order to help environmental evaluation to be used in public decisions. The focus of the committee will be on the concrete structure rather than the whole building in view that the concrete structure serves as a sustained platform for other components/systems that change during its life.

Construction waste comprises a significant part of the solid waste worldwide. Aspects related to the environmental impacts of demolition waste from concrete structures with respect to optional uses (e.g. recycled aggregates, raw material for cement production, landfilling) will be dealt with as well. Carbonation rate and resulting corrosion resistance of concrete during its service life and the CO2 sequestration potential of the concrete debris after demolition is also an area of concern.

2) Concerning the second step of the LCA, The TC will work on data quality. In particular, it will work on their variability due to the processes involved and the sensitivity of the different parameters that influence the results.

- CO

2 certificates, economic considerations: economic allocation and money transfer

- Gathering environmental data on alternative binders will also be done in this task.

3) Finally, a last task of the TC will be a study of the environmental indicators as proposed by the different problem and/or damage oriented impact methods. The objective is not to define a set of indicators that would be more adapted than others, but rather to identify what aspect of the life cycle of a concrete structure is controlling each indicator. The only impact where concrete materials would need a specific indicator, different from the commonly used environmental indicators, is for the recycling and more generally for the use of natural resources such as sand and gravel. The impact of the consumption of virgin materials is not accurately quantified with currently available indicators.

Since these structures usually contain reinforcing steel, the environmental impact of the latter will also be included in the study.

Among the different aspects that influence the result of an LCA study, a particular attention will also be paid to the sensitivity of the LCA to allocation. Whenever a process produces more than one end-product, the overall impact should be properly divided over all end-products. This partitioning can be done based on the mass or the economic value of the different end-products.

The following topics will be dealt with:

- Environmental impact of industrial by-products commonly used in concrete, e.g. fly ash, blast-furnace slag, silica fume etc.

Terms of reference

The TC will work for 4 to 5 years.

Members of the TC will be recruited from the academic world as well as from the industry, based on their experience in life cycle assessment, concrete structures and environmental assessment. In order to strengthen and validate the results obtained in this TC, experts from the LCA research field will be invited to participate in TC meetings and chair sessions in conference where the TC will meet, as it has already been done in Nantes LCA&construction conference (July, 2012).

A comprehensive literature survey will identify gaps of knowledge that prevent an accurate LCA of concrete structures. The knowledge in some areas is sometimes overwhelming in a way that it prevents the identification of the important parameters. Gathering this information from literature surveys as well as from workshops/conferences will enable focussing on them.

Members of the TC will determine a calculation method that will be evaluated by a simulated round robin test that will take into account local conditions existing in each country of the participating members. In these tests, different concrete mix designs and structures will be evaluated using different software and different environmental database.

Detailed working programme

First and second year:

Gathering state-of-the-art information regarding the evaluation of environmental impacts of concrete structures. The information will include evaluation methods, definitions of the system boundaries of the assessment, availability of environmental data regarding concrete structures, accuracy of data and any other information required for the assessment. A workshop/conference is planned towards the end of the second year to complete the acquisition of information and data.

Third year:

Solidification of information into rules and built up of a simplified methodology to accurately perform LCAs of reinforced concrete structures without losing accuracy. A Round robin calculation will be performed by members of the TC to evaluate the accuracy of the LCA outcome. In addition, the key parameters in each step of the LCA (definition of goal and scope, inventory analysis, impact analysis and interpretation) need to be identified.

Fourth and fifth year:

Dissemination of the conclusions and the methodology by means of training courses that can be linked to a conference with a similar topic, and by means of student workshops like those organized by Paristech.