Each of the above tests measure a material property but they do not consider the effect of a number of stresses together – the real life scenario.
The issue of expansive pyrite within existing houses is frequently in the news in Ireland. There are at present no direct simple tests that can evaluate the likelihood of future damage when stone containing pyrite is used within or under a building. A long-term objective is to develop a simple laboratory test that will evaluate the likelihood of heave due to the presence of pyrite, this objective will commence with the collating of existing information on pyrite.
Hypothesis: As noted above there are significant deficits in the testing of stone, particularly aggregates produced by quarries.
Decisions are being made on the acceptability of material for use in construction, infrastructure, rail, road etc. based on testing that does not replicate the actual conditions the aggregate encounters during its useable life.
Large volumes of marginal material must be considered waste unless an engineering use can be found for it. Our natural resources are finite and the best possible uses of the valuable assets. We cannot afford to dispose of material when there is a possibility that it can be better used.
Further the costs associated with inadequate testing of aggregates are being felt daily. The pyrite issue continues to expand in effect. Originally it was considered the hardcore under a few houses were degrading and causing aesthetic and structural damage to the a few houses. More recently it has been recognised that the problem is bigger and that a large number of homes are being affected. As of this week the Association of Consulting Engineers of Ireland (ACEI) has warned members that there is evidence of pyrite damage ion houses where the block work is disintegrating.
Methodologies: Before new testing can be considered the tests now in use, both in Ireland and internationally will be examined. This will be undertaken by procuring samples from Quarries – Morrissey’s, CRH (Roadstone), Murphy’s, Kilsaran.
Two sample types will be considered referenced based on NRA standards – Class 6F (capping) and Class 800 series (sub-base). Testing will then be undertaken on these samples to:
In cooperation with a number of large suppliers and commercial laboratories we propose to evaluate the existing tests by simulating the repeated loading effects of traffic, both road and rail and comparing these simulations with the existing tests.
As part of this research it is hoped to begin to evaluate the possibilities for the development of a test or tests to predict pyritic reaction in granular material. This will likely be a long-term project and will require collation and digestion of the existing experience both nationally and internationally.
Locally and nationally the use and availability of granular material influences productivity. Tests that do not predict performance are causing operational difficulties in a number of multi -national developments that have been completed or are in the process of completion. Very good granular material is a scarce resource and should be used only where needed – in effect applying the business strategy “just-in-time delivery” to infrastructure development “just-good -enough material”. Material “not-good enough” fails in operation and the knock -on costs are usually many multiples of the original construction cost.
(a) Recommendations regarding existing tests as to their reliability and suitability
(b) Recommendations as to further research for suitable tests for particular loading and environmental conditions – rail, road, aircraft runway
(c) Commencement of pyrite testing programme – this hopefully will develop into a long-term research project