Estudio del contenido de humedad en un material en base cemento midiendo su impedancia y su gamma-densitometría

The local water content in cementitious material depends on the equilibrium between its atmospheric environment and its bulk properties. So, the moisture profile in material can vary with time. The object of this study is to follow the change of this profile by measuring the electrical impedance of the material with pairs of small wires embedded at different depths. This method was applied to young cement paste specimens. The results obtained show that this method is quite satisfactory. The best frequency to be applied, is about 50 or 100 Hz. These results were compared with those obtained with gamma-densitometry.El agua contenida en los materiales en base cemento depende del equilibrio entre la atmósfera que le rodea y las propiedades de la matriz sólida. Por lo tanto el perfil de humedad en los materiales puede variar con el tiempo. La finalidad de este estudio es seguir los cambios en dicho perfil, a través de la medición de la impedancia eléctrica del material con varios pares de pequeños conductores situados a diferentes profundidadades. Este sistema se aplicó a diversas muestras de pasta de cemento Jóvenes. Los resultados obtenidos nos hacen ver que el método es satisfactorio, debiendo aplicarse a una frecuencia de 50 a 100 Hz. Dichos resultados se compararon con los obtenidos a través de la gammadensitometría

Electrochemical Methods for evaluating inhibitors of steel corrosion in concrete

Electrochemical methods were used to evaluate sodium phosphate and sodium nitrite as inhibitors for the corrosion of steel in saturated calcium hydroxide solution containing chloride ions. The studies included immersion, potentiodynamic, potentiostatic, and galvanostatic tests. The results obtained from these methods were in good agreement. They show that sodium nitrite is an anodic inhibitor which is not effective if its concentration is lower than that of the chloride ions. Sodium phosphate acts as an anodic inhibitor if its concentration is higher than 0·6 times the chloride concentration. It is totally effective when its concentration equals the chloride concentration

Study of reinforced concrete slabs after three years of cathodic protection under severe conditions

International audienceThe objective of this study is to determine the influence of cathodic protection on the properties of concrete cover in concrete slabs. To accelerate deterioration, the slabs were subjected to freezing and thawing cycles and sprayed with sodium chloride solution. Cathodic protection was applied to the reinforcements for three years. Then, the test pieces underwent physico-chemical analysis. Scanning electron microscopy and X-ray spectrometry were used to study the reinforcement-concrete interface, in particular for detecting alkali-silica reaction due to the alkalization. Carbonation depths, chloride penetration profiles and examinations of the reinforcements showed the good condition of the concrete cover and the beneficial effect of the cathodic protection of embedded steel