ABSTRACT Carbonation and chloride action are the two leading causes of degradation in reinforced concrete structures. Despite the combined action of these two mechanisms being a reality, there is little research on the effect of this combination in cementitious matrices. Furthermore, the incorporation of fly ash in cementitious matrices has been frequently used in order to make the matrix more resistant to the action of chlorides. On the other hand, it is known that Ca(OH)2 existing in the matrix is consumed by the pozzolanic reactions, which makes easier the carbonation front advance. Therefore, this paper presents a study of the behavior of cementitious matrices, with and without fly ash, subjected to the combined action of chlorides and carbonation. Two different kinds of mortars were produced: reference (only cement CEM I 42.5R) and fly ash mortar (40% replacement of cement). After curing, the specimens were subjected to three different wetting-drying cycles, considering NaCl solutions and CO2 atmospheres. Afterwards, chloride profiles and carbonation front were measured. Results show that carbonation has a direct influence on chloride penetration, decreasing it for cement mortars with 0% fly ash and increasing it for mortars with 40% cement replacement by fly ash. Moreover, the evolution of carbonation is also influenced by chloride presence, which decreases under the combined action.

This work studied the influence of rendering mortar layer on chloride transport into concrete structures. Concrete specimens rendered with three different mortar mixtures and two rendering thickness were used. Five of the six faces of the specimens were coated with epoxy resin to simulate unidirectional flux. The specimens were subjected to weekly wetting and drying cycles in a sodium chloride solution for 49 days. At the end, total chloride profiles were obtained. Results show that rendering mortars influence chloride transport into concrete and this is more accentuated for less porous mortars and with higher cement content. There is also a chloride accumulation close to the interface mortar-concrete region, which is explained by the differences on chloride transport ability between mortar and concrete. Although mortars are more porous than concrete, they can represent an additional protection against chloride penetration into concrete.

Este trabajo estudió la influencia de la capa de mortero en el transporte de cloruros en estructuras de hormigón. Probetas de hormigón con capas de tres distintos morteros y dos espesores de revestimiento fueron empleadas. Las probetas tuvieron cinco de sus seis caras pintadas con resina epoxi para simular un flujo unidireccional y fueron sometidas a ciclos semanales de inmersión y secado en disolución de cloruro sódico a lo largo de cuarenta y nueve días. Al final, perfiles de cloruro totales fueron obtenidos. Los resultados indican que la capa de mortero influye en el transporte de cloruro en el hormigón y esta influencia es más fuerte en el caso de los morteros menos porosos y más ricos en cemento. También se observa una acumulación de cloruro cerca de la interface mortero-hormigón, la cual es explicada por las diferencias en la capacidad de transporte entre mortero y hormigón. A pesar de que los morteros son más porosos que el hormigón, estos pueden representar una protección adicional respecto a la penetración de cloruro en el hormigón.

Este trabalho estudou a influência da camada de revestimento em argamassa na penetração de cloretos no concreto. Para tanto, foram moldados corpos de prova de concreto nas dimensões 8 cm x 8 cm x 8 cm e relação água/cimento de 0,55, sobre os quais foram aplicados três tipos de argamassa de revestimento, após uma fina camada de chapisco. Vencidos os períodos de cura de 28 dias para o concreto e a argamassa de revestimento, cinco das seis faces dos CPs foram isoladas com resina epóxi para simular um fluxo unidirecional. Esses CPs foram submetidos ao ensaio de imersão e secagem por 49 dias e, após isso, foram retiradas e analisadas amostras para a obtenção dos perfis de cloretos. Os resultados indicam que as argamassas de revestimento influenciam no transporte de cloretos no concreto e que essa influência é mais pronunciada para as argamassas menos porosas e mais ricas em cimento. Também se observou um acúmulo de cloretos na região próxima à interface argamassa-concreto, o qual é explicado pelas diferenças na capacidade de transporte entre a argamassa e o concreto. Apesar de as argamassas serem mais porosas que o concreto, elas podem representar uma proteção adicional em relação ao retardamento na penetração de cloretos no concreto.

This study investigated the influence of the rendering mortar layer on chloride penetration in concrete. Cubic concrete specimens were cast measuring 8 cm x 8 cm x 8 cm and a water to cement ratio of 0.55. Three different mortar mixtures were used to cover one concrete face, after a thin layer of spatter dash treatment. Reference concrete specimens were also cast. After curing periods of 28 days for concrete and mortar rendering, five out of the six faces of the specimens were coated with epoxy resin to simulate unidirectional flow. The specimens were then subjected to wetting and drying cycles for 49 days and, afterwards, samples were extracted and analysed to obtain chloride profiles. The results show that mortar renderings influence chloride transport into concrete and this is more accentuated for less porous mortars and with higher cement content. There is also chloride accumulation close to the mortar-concrete interface region, which is explained by the differences in the chloride transport ability between mortar and concrete. Although mortars are more porous than concrete, they can represent an additional protection against chloride penetration into concrete.