Water and chloride ions are key parameters in corrosion processes of reinforced concrete. Furthermore, rebars corrosion is the first cause of decay in historical monuments made of concrete. Thus to develop new techniques to be able to detect or quantify water and chloride ions seems to be an interesting approach in the diagnosis of cultural heritage reinforced concrete buildings, especially if these new techniques are non-destructive. The technique SUSI-R© is a non-invasive microwaves system, based on the measure of a dielectric contrast between dry and wet material. Water content and salinity index are calculated from the resonance properties of the probe, which are a function of the material permittivity. Initially developed to quantity the moisture content and to detect the presence of salts in mural paintings, SUSI-R© was considered in this study for concrete. In a first phase; the SUSI-R© technique was tested to follow the moisture and salts content in reinforced concrete slabs, made with CEM I or CEM III cements, after their semi-immersion in water or in a sodium chloride solution. Several series of measurements were then realized before and during the rise of the imbibition front. In the second phase, the calibration of SUSI-R© was made in laboratory on prisms made with the same concretes as those used for the slabs, and that had undergone the same curing conditions. The resonance parameters were correlated to the moisture content contained in these samples, with various saturation rates, in water and salted water. The first results of this study showed that the technique allows to follow the hydric changes of the material but also to differentiate the type of imbibition solution: water or salted water. Different evolutions of salinity index were also distinguished according the type of cement. The calibration in laboratory allowed to connect the resonance parameters of the probe with values of moisture content, and so to quantify the moisture content of the concrete slabs investigated during the first phase of the study.
Measurement of water content and salinity index in concrete by evanescent field dielectrometry
C Riminesi
2017
Abstract
Water and chloride ions are key parameters in corrosion processes of reinforced concrete. Furthermore, rebars corrosion is the first cause of decay in historical monuments made of concrete. Thus to develop new techniques to be able to detect or quantify water and chloride ions seems to be an interesting approach in the diagnosis of cultural heritage reinforced concrete buildings, especially if these new techniques are non-destructive. The technique SUSI-R© is a non-invasive microwaves system, based on the measure of a dielectric contrast between dry and wet material. Water content and salinity index are calculated from the resonance properties of the probe, which are a function of the material permittivity. Initially developed to quantity the moisture content and to detect the presence of salts in mural paintings, SUSI-R© was considered in this study for concrete. In a first phase; the SUSI-R© technique was tested to follow the moisture and salts content in reinforced concrete slabs, made with CEM I or CEM III cements, after their semi-immersion in water or in a sodium chloride solution. Several series of measurements were then realized before and during the rise of the imbibition front. In the second phase, the calibration of SUSI-R© was made in laboratory on prisms made with the same concretes as those used for the slabs, and that had undergone the same curing conditions. The resonance parameters were correlated to the moisture content contained in these samples, with various saturation rates, in water and salted water. The first results of this study showed that the technique allows to follow the hydric changes of the material but also to differentiate the type of imbibition solution: water or salted water. Different evolutions of salinity index were also distinguished according the type of cement. The calibration in laboratory allowed to connect the resonance parameters of the probe with values of moisture content, and so to quantify the moisture content of the concrete slabs investigated during the first phase of the study.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
