277-LHS : Specifications for testing and evaluation of lime-based repair materials for historic Structures
Technical Committee 277-LHS
Deputy Chair: Dr. Jan VALEK
(i) The test procedures for repair mortars and grouts for historic structures (HS) are following the standards established for cement-based mortars. These procedures lead to erroneous results as they are based on certain technical assumptions valid only for modern calcium-silicate cement based binders. However, in case of repair of HS the current trend is to support the use of lime-based binders that are in many ways regarded as compatible with the HS. The existing EN standards for lime (EN459), as well as the relevant to mortars series EN1015 do not address specific issues related to lime-based mortars and grouts, such as mixing and stirring scenarios, slow setting and hardening, time of testing mechanical characteristics and physical properties, testing durability (wetting-drying, freezingthawing, sulphate attack etc). Therefore, laboratories dealing with the aforementioned materials often modify existing standard procedures addressed to other materials. Thus test results from different laboratories or industry, are not easily compared. The major subject matter is thus adapting/modifying test procedures for repair mortars and grouts to be more realistic in terms of describing properties, behaviour and performance of non-cement binders (e.g. lime, lime-pozzolana, NHL). The scope is to deal with necessary modifications of testing procedures of mortars and grouts for HS and to carry out a harmonisation and pre-normative work with a potential to propose changes and adaptations to the current standards.
(ii) Adaptation of simple field test methods to assess behaviour and performance of lime-based repair materials on the building site, which will be verified by corresponding laboratory tests. The proposed TC aims at modifying /adapting the basic qualifying test procedures for mortars/grouts, not the specific ones (i.e. thermal properties).
Terms of reference
- Review the classification of mortars/grouts, according to their functional role in HS and evaluation of the basic performance requirements in relation to the properties of mortars and grouts (Reports of TC203-RHM).
- Analysis of binding systems and mechanisms (setting-hardening, deteriorating) of lime-based binders used in mortars of HS. Review of modern available binders and regulation frames. Collection and analysis of existing practices in the various laboratories and literature data regarding adapted testing procedures on repair mortars. Determination of a number of test procedures (incl. specifications of raw materials, curing conditions, cycles etc.) related to specific binders/ binder combinations. Laboratory testing. Formulation of new testing procedures (pre-normative). For example to suggest smaller Marsh cone for the fresh grout
fluidity measurement experimental work (including some round robin tests) is needed.
- Collection of field test methods used in practice. Analysis of working principles in relation to the tested properties; Development of new field tests. Validation of the effectiveness of field tests by comparing them with the laboratory ones.
- A minimum time necessary for the activities of this TC is 5 years. The reason is that laboratory testing is part of the activities.
- The work will imply a thorough reviewing of existing practices and literature. Lab and field testing and comparison of conditions and results is foreseen.
- Membership of this TC: Czech Republic (1), Greece (3x), USA (1), Netherlands (2), Italy (2), Portugal (2), Scotland (1), Slovenia (1), Switzerland (2), has been confirmed in the previous TC243-SGM. Researchers from Spain (tbc.), Ireland (tbc) and Germany will be invited to join the proposed TC.
- The relevance to industry is to provide adequate, reliable and performance based testing methods for checking and controlling the quality of prefab mortars/grouts applicable to repair in historic masonry.
- The harmonized and unified test methods facilitate and promote the market of materials all over Europe. Furthermore construction industry is very much benefited from enhancing the quality of works. At European level any investment in the field of HS preservation is upgraded.
Detailed working programme
Most of the members are coming from Universities and Research Centres with long-term experience in testing lime-based repair mortars/grouts.
A number of workgroups will be formed in the first meeting to share objectives and responsibilities.
Two meetings per year will be arranged followed recommendations of RILEM for TC(s).
Links with previous RILEM TCs:
• Technical Committee 167-COM: Characterization of historic mortars with respect to their repair
• Technical Committee 203-RHM: Repair mortars for historic masonry
• Technical Committee 216-SAM: Strategies for the assessment of historic masonry structures with NDT
• Technical Committee 243-SGM: Specifications for non-structural grouting of historic masonries and historic architectural surfaces
Actually, the objectives of the proposed TC emerged during the works of previous TC(s). That is why an effort of round robin testing started on testing fresh properties of grouts in the frame of TC 216-SAM.
The proposed TC is very relevant to RILEM ‘s mission as Rilem since more than 15 years promotes TC activities in the field of cultural heritage (current Cluster E)
Most appropriate cluster to be assigned to: Cluster E. Masonry, Timber and Cultural Heritage (Convener: Robert FLATT)
Apart from RILEM TC(s) and Cluster link with CEN TC346 Standardisation on Conservation of Cultural Heritage will be made. The proposer has already communicated with Prof. V. Fassina and discussed the objectives of the proposed TC. They have not confronted in the frame of Workgroups of CEN TC546 and it would be useful to keep contact with relevant WG of CEN TC346.
The direct benefit, for which is a significant need in the conservation practice, is to be able to use in design of repairs more realistic data in terms of properties, behaviour and performance of mortars/grouts containing non-cement binders (e.g. lime, lime-pozzolana, NHL) by adapting/modifying currently used test procedures for cement-based materials.
The TC will produce:
- Harmonized and unified testing procedures relevant to lime-based binders (pre-normative), for their use in mortars and grouts, concerning properties in fresh and hardened state as well as basic durability aspects.
- A state-of-the art report about test procedures currently in use to characterise behaviour and performance of historic mortars.
- A state-of-the art report about current field testing of historic porous building materials (mortar, stone, brick, adobe, ceramics)
The TC will organize 1 workshop and its members will participate in international courses (such as Mare 2017) and international conferences such as Historic Mortar Conference 2019 to present the results of the TC.
Group of users
The target groups are testing laboratories, academic Researchers (incl. PhD students), practitioners and industry. Other target groups are public and private organisations (Ministries or State Departments, Archaeological Schools etc., contractors and constructing companies, conservators, architects, and engineers) involved in the preservation of the cultural heritage and bearing a role in supervising such operations.
Specific use of the results
For all those groups, mentioned in 7, it is very important to carry out repair works based on realistic data. The proposed TC aims at contributing and improving the testing methods regarding repair mortars/grouts. This is in fact a basic requirement for the building conservation practice, which is up to now still not fulfilled. The TC deliverables will provide a set of Laboratory and field procedures for testing quality of mortars and grouts, used almost in all repair interventions. It is believed that these modified specifications will advance the level of repair works for the benefit of economy and longevity of HS.