Influence of internal relative humidity and mix design of radiation shielding concrete on air permeability index

- A procedure of specimen preparation of homogeneous RH a desired value was proposed.
- API of shielding concrete in oven dry state and at a specific, stabilized RH was determined.
- Linear relationship between API and concrete RH in range of 2% to 99% was found.
- The influence of the type of aggregate for shielding concrete on API value was determined.

The permeation properties of concrete are strongly influenced by the degree of saturation of capillary pores. Test results of the Autoclam air permeability index (API) of radiation shielding concrete are presented. Concrete specimens were made with CEM I and CEM III/A cements and special aggregates for radiation shielding: crushed barite, magnetite, serpentine and amphibolite. Two procedures of accelerated drying with simultaneous measurement of moisture distribution in the specimens were proposed. The specimens were tested at different RH levels from a fully saturated state to an oven dried state. The linear relationship between the API and RH was obtained. Effects of heavyweight and hydrogen-bearing aggregates on air permeability index were revealed.