A. Santos Silva

The importance of SEM-EDS analysis in the study of old mortars

Materials Department, National Laboratory of Civil Engineering, Av. Brasil 101, 1700-066 Lisbon, Portugal, padriano@lnec.pt, ssilva@lnec.pt Buildings Department, National Laboratory of Civil Engineering, Av. Brasil 101, 1700-066 Lisbon, Portugal, rveiga@lnec.pt Geosciences Department and Geophysic Center of Evora, University of Evora, R. Romao Ramalho 59, 7000-671 Evora, jmirao@uevora.pt Chemistry Department and Chemistry Center of Evora, University of Evora, R. Romao Ramalho 59, 7000-671 Evora, candeias@uevora.pt

Mortars characterization of Olisipo late Roman wall

Trabalho de projecto de mestrado, Geologia Aplicada (Geologia de Engenharia), Universidade de Lisboa, Faculdade de Ciencias, 2015

Risk of ASR in coating mortars incorporating glass aggregates and a Portland–limestone cement

As the cement content is one of the parameters that control alkali–silica reaction (ASR), this study examined its influence on the expansion of glass mortars. The mortars had volumetric ratio of 1:4 (cement: aggregate) and various aggregate compositions, obtained using replacement ratios of natural sand with waste glass, of 0, 20, 50 and 100%. A volumetric ratio 1:4 was chosen because it is a current composition for cementitious coating mortars. In fact, mortar mixes with increased cement content can lead to erroneous conclusions for in situ mixtures with reactive aggregates. It is concluded that it is feasible to produce glass mortars without deleterious ASR expansion depending on the amount of cement used. For normal cement/aggregate ratios for coating mortars (1:4, in volume), a CEM II/B-L 32.5 N mortar with glass incorporation has a low ASR risk.

The role of SEM in the diagnosis of expansive chemical reactions in cement-based building materials

The alkali-silica reaction (ASR) and internal sulfatic reaction (ISR), normally both referred as internal expansive reactions, are among the most common causes of concrete structures deterioration worldwide. These reactions, which could be present simultaneously, origin products those are responsible for expansive stresses in the cement-based building materials, leading to severe cracking and loss of strength. The reaction products are also often amorphous or badly crystallized, or even present in very low content that they are very difficult to identify by current analytical physico-chemical techniques. The main macroscopic evidence of these degradation phenomena in concrete structures are the superficial occurrence of map-cracking, pop-outs and exudates (figure 1). Nevertheless, these symptoms are not exclusive and enough to establish a correct diagnosis.