NOGUEIRA, RITA1; FERREIRA PINTO, ANA PAULA2; GOMES, AUGUSTO3; G. ALMEIDA, NUNO4

1) Research Assistant, IST-ICIST, Department of Civil Engineering, Architecture and Georesources, rita.nogueira@tecnico.ulisboa.pt

2) Assistant Professor, IST-ICIST, Department of Civil Engineering, Architecture and Georesources, anapinto@civil.ist.utl.pt

3 Associate Professor, IST-ICIST, Department of Civil Engineering, Architecture and Georesources, augusto@civil.ist.utl.pt

4 Research Assistant, IST-ICIST, Department of Civil Engineering, Architecture and Georesources, nunoal@civil.ist.utl.pt

This paper proposes the contact sponge method for assessing water absorption of mortars in renders: the moist sponge is placed against the material surface during a predefined period, at constant pressure. The mass difference of the sponge, before and after the test provides information on the water absorption characteristics of materials. The method is easy to carry out and non-destructive. The testing parameters of the method (available amount of water in the sponge, contact time and pressure in the sponge) are features that must be previously defined to obtain reliable results. Some research has been developed to understand the influence of these parameters on the results, but studies concerning mortars are scarce. In this paper, the influence of the water amount and the contact time on the results is analyzed. An experimental campaign was developed and four water amounts added to the sponge (5g, 7g, 9g, 10g) and five contact times (15s, 30s, 45s, 60s, 90s) were studied. Tests were performed in brick renders of mortar mixtures frequently found in masonry renders. The testing parameters which enabled significant, sensitive and accurate results were identified. The discussion of the results provided important criteria for the choice of the testing parameters in further works.

Keywords: contact sponge method, water absorption coefficient, porosity, rendering mortars