240-FDS : A framework for durability design of fibre-reinforced strain-hardening cement-based composites (SHCC)
Technical Committee 240-FDS
Deputy Chair: Dr. Flávio DE ANDRADE SILVA
Activity ending in: 2016
Strain-Hardening Cement Composites (SHCC) are classes of fibre-reinforced cement-based composites in which crack formation in the cement-based matrix is controlled by fibres bridging cracks to the extent that multiple, closely spaced fine cracks form at increasing tensile deformation and force. The durability hereby afforded to the structural system in service conditions must be appropriately modelled and characterised to enable recommendation of rational design guidelines for durability design with SHCC. In addition, a standard test procedure is required for such characterisation to verify compliance of a material to specified durability requirements.
The work follows on that of the subcommittee on durability of TC 208-HFC, which has drafted a comprehensive State-of-the-Art report on durability of SHCC, and performed preliminary Round Robin tests on crack patterns in SHCC under various loading conditions. Such crack pattern characterisation physical experiments must be extended, and the link to ingress of deleterious liquids and gases made through appropriate physical experiments and theoretical studies.
The experiments will be performed in several laboratories, spread wide in the world, to establish laboratory compliance as well as conformity of SHCC materials prepared from local ingredient materials to the standardised test and durability categorisation outcomes.
Terms of reference
A 5 year period is required, with the following milestones:
(1) international workshop on durability of SHCC, with published proceedings in year one
(2) results of preliminary Round Robin tests presented at a meeting in year 2
(3) reports on bibliographic and theoretical studies on appropriate models and parameters, presented at meeting in year 3
(4) results of final Round Robin tests with standardised test(s) agreed upon,
(5) final Report and papers in Materials and Structures on standard test method and framework for durability design.
Recruitment of members will be from those actively participating in TC 208-HFC, subcommittee 2 on durability, and extended to the international research community on cement-based construction materials with similar mechanical and durability characteristics like textile reinforced concrete (TC TDT). Members of TC PSC (Performance based specifications and control of concrete durability) and TC CTC (Corrosion initiating chloride threshold concentrations in concrete) will be approached due to the relevance of their research on SHCC durability.
Detailed working programme
The work will
- start by invitation of paper article contributions on durability of SHCC classes of materials to a special session at an international workshop to be arranged in the first year of this TC.
- At this first meeting the framework for durability design with SHCC will be drafted (dFDS), in order to define the scope of investigation and applicability of a standardised test method to quantify durability classification.
- Based on these contributions, the State-of-the-Art report and final results of TC 208-HFC SC2, a series of physical experiments will be proposed for execution by members in the following year.
- Reports on results of the tests will be presented and thoroughly discussed at a meeting towards the end of year 2
- Based on the reports the dFDS will be revisited, with intended outcome to lay the theoretical basis for the FDS. Theoretical studies for the following research year (3) will be proposed.
- The theoretical studies will be presented and thoroughly discussed at a meeting towards the end of year 3.
- A final series of Round Robin tests will be proposed at the above meeting, by consensus.
- A meeting at the end of year 4 will be devoted to scrutinise the Round Robin test results
- Year 5 will be used to draft, review and submit a final Report on the FDS and recommended standard test method.
- At least two papers, one on the test method and one on the FDS, will be prepared and submitted to Materials and Structures.
The activities of this TC build on the work by subcommittee 2 of TC 208-HFC, so its members are invited to the new TC.
Relevant research is currently performed in TC TDT, TC CTC and TC PSC. The work in these TC’s will be followed closely through inviting members to become members also of TC FDS.
Research outputs include the following:
- contributions to workshop proceedings on durability of SHCC,
- a final report including
_a framework for durability design and
_proposed test method for durability of SHCC;
_summaries of durability test results from various participating laboratories.
- Two articles in Materials and Structures to disseminate the TC results in this shortened format.
Group of users
The lack of characterisation and standardised test is believed to be a contributing factor to limited application of SHCC in industry. Therefore, it is a specific goal to inform and equip industry with guidelines for design for durability with SHCC.
Design engineers of infrastructure, but also owners and developers of such infrastructure are main targeted users. This class of material lends itself to durable repair of existing structures and infrastructure. Owners of especially large infrastructure, diagnostic and repair engineering designers and specifiers, may benefit from the recommendations from this TC. Laboratories responsible for standardised testing of construction materials will take note of the procedures.
Specific use of the results
Initial cost is frequently the governing criterion in selection of construction materials, for new construction as well as for repair of existing structures. This approach has contributed to the current level of infrastructural repair required and performed internationally. A main use of these results will be for the consideration and quantified evaluation of SHCC as alternative construction material for infrastructure or (infra)structural elements, or repair strategies with long-term cost benefits.