177-MDT : Masonry durability and on-site testing
Technical Committee 177-MDT
The work will cover the following masonry materials: 1. Units (rectangular prismatic bricks of blocks) made from: Fired clay, Concrete, Calcium silicate; Aerated concrete, Reconstituted stone, Natural stone; 2. Irregularly shaped pieces of natural stone (rubble). 3. Bonding mortar of the following types: Portland cement-sand mixtures, hydraulic lime-sand mixtures, pure lime-sand mixtures, special formulations, e.g. thin-bed mortars and lightweight mortars. The work will concentrate on the development of laboratory accelerated tests to predict the durability under ambient environmental actions and site (in-situ) tests and monitoring systems to assess contemporary condition/performance, and the effectiveness of repairs. The tests may be concerned with either the elements, e.g. units, or the composite masonry structure, and may be either non-destructive (NDT), cause minor (not structurally/ aesthetically significant) damage (MDT) or be destructive (DT). The scope will include theoretical studies and empirical experimental evaluation of prototype tests. This is new work inspired by the current worldwide trend away from prescriptive specifications for materials towards performance specifications, and the trend away from demolition/rebuilding towards conservation and rehabilitation.
Terms of reference
Timetable: a period of 5 years is proposed in which priorities will be set; existing data will be reviewed; draft test procedures will be established; tests will be evaluated in individual labs; inter-laboratory checking will be carried out; final drafts will be developed, then published. Membership: estimated number 20 plus, some recruited from RILEM committee 127-MS which finishes in 1997, but a number of new members have been proposed to widen the range of expertise and the international representation. Business will be carried on via correspondence and at least one meeting per year.
Detailed working programme
Year 1: Prioritisation - Decide on priority objectives and research existing data on known performance and test behaviour. Year 2: Development - Either develop new tests, adapt existing draft tests or adopt tests which fully meet the objectives. Year 3: Assessment - Assess reliability, repeatability and accuracy in single laboratory trials; produce first drafts. Year 4: Operator sensitivity - Carry out inter-laboratory or round-robin evaluations where necessary: discuss and refine drafts. Year 5: Publication - Publish final drafts.
The new committee would have links to two new RILEM committees: 1) "Characterization of Old Mortars with respect to their repair" (COM) and 2) "Computer Modelling of Mechanical behaviour of Masonry structures" (MMM). It would also continue well-established links between RILEM and CIB committee W23 A. The committee will be the sole RILEM body with a remit to develop tests for the whole range of masonry applications.
The main output is expected to be harmonised test method recommendations. These would normally include, as appropriate, both the necessary definitions of specialised terminology and the basic public domain bibliography which underpins the principles of the tests. The TC would also intend to arrange at least one symposium, around year 4, to allow wider consultation before final drafting.
Group of users
Academics, testing laboratories, industrialists and practitioners.
Specific use of the results
The main aim is to put tests which are under development in individual institutions on a more formal and consensus footing, and to make sure that they are subjected to a critical evaluation by peers to weed out poor or impractical techniques, unrepeatable or unreliable methods, methods which work but give information of no value and inconsistent or ambiguous drafting. To this end, a lot of care will be taken to ensure that the scope tells the potential user very clearly what the test can and cannot achieve. This will contribute towards the user's getting better value from the test methods. As concerns durability, a particular aim will be to provide the basis for a future generation of wholly performance-based standards for masonry materials. Application of the site tests will enable engineers and conservationists to design/redesign, troubleshoot, and renovate buildings with more confidence.