Portland cement cocciopesto mortar for repairs to outdoor pavements

0433827 - ÚTAM 2015 RIV MX eng O - Others
Drdácký, Miloš - Frankeová, Dita - Janotová, Dana - Mlázovský, V.
Portland cement cocciopesto mortar for repairs to outdoor pavements.
2014
R&D Projects: GA ČR(CZ) GBP105/12/G059
Institutional support: RVO:68378297
Keywords : lime metakaolin mortar * portland cement cocciopesto mortar * material tests
Subject RIV: JN - Civil Engineering

Repairs to outdoor pavements at historic castles have been carried out with the use of mortar from natural hydraulic limes or cements prepared from aerial lime mixed with hy-draulic sands, e.g. crushed slag. Modifications based on latent hydraulic materials, for exam-ple metakaoline, have resulted in mixtures with sufficient strength and appearance to be acceptable to the conservation authorities. However, they exhibit rather significant wear and limited frost resistance. New mixtures taking advantage of the properties of white Portland cement were therefore suggested by Mlázovský, and the durability and other material char-acteristics of this material were studied in the laboratory after one year of in situ application at Karlštejn, a Czech Royal Castle. For the mechanical characterization, the small sample-small specimen test methodology developed by Drdácký was utilized, including the prolonga-tion of short specimens for bending tests by means of prosthesization. In addition to tests of other relevant physical characteristics (capillary water uptake, specific weight and surface wear by grinding), a careful investigation of frost resistance was made, and the changes were observed visually and by ultrasonic testing. The material composition was checked using thermogravimetry and XRF. Interesting results were yielded from the porosity tests (mercury porosimetry), which showed that the mortar has one order lower porosity than fine brick, and its main peak of pores lies at around 0,1 μm. However, brick dust and aggregates release wa-ter slowly and contribute to a high degree of hydration. Cement-gauged cocciopesto hydrau-lic lime mortar showed remarkably better performance than the previously-used PC-free hydraulic lime mixtures, which need yearly maintenance or impregnation, e.g. with linseed oil. Cement-gauged cocciopesto hydraulic lime mortar has been accepted by the conservation au-thorities for severe outdoor conditions.
Permanent Link: http://hdl.handle.net/11104/0237991