Concrete structures as bulk property from the point of view of nuclear methods

The Small-Angle Neutron Scattering (SANS) uses a method which provides an indispensable contribution to the nondestructive characterization of bulk properties of cement-bound concrete, its development and its influence within a range from one nanometer to several micrometer, depending on the neutron wavelength and the corresponding spectrometer. For the first time repeated long-term observations of the scattering parameters have been carried out at a time interval of up to three years. The relation of scattering curve and fractal dimension allows an interpretation of microscopic properties of concrete such as diffusion coefficent and permeability by microscopic structural sizes which are determined nondestructively as bulk property. The new NMR one-sided access system nondestructively measures the humidity profile in the region fundamental for the evaluation of the carbonization and the penetration of moisture of the concrete cover up to depths of approximately three centimeters and a depth resolution of one millimeter. Diverse radio tracer techniques (radiometry for the aquisition of temporal transport courses and the determination of crack depths; autoradiography for the display of tow-dimensional distribution) continually track the transport of moisture and the transport of salt ions connected from millimetric todecimetric range. The combination of acoustic and eletric emission offers enlarged possibilities for the understanding of crack kinetics in the bulk.