In the frame of an extended research program dealing with wood shavings utilization in mortar, a set of procedures were developed for verifying effects of wood shavings addition to specific mortar properties. Mixes containing wood shavings replacing fine aggregates by 0, 30, 50 and 70% of their volume were made. Workability, fresh mortar unit weight, ultrasonic pulse velocity (UPV) and flexural and compressive strength were determined, based on measurements, at various curing ages. Measurement results and analysis suggest that compressive strength reduction caused by wood shavings addition could be predicted. The outcome was standardized in the form of a multifactorial sigmoidal model. It was also made evident that the mix proportion of cement increases when wood shavings are used as a by volume replacement of conventional fine aggregates, due to the low value of specific gravity of wood compared to conventional aggregates. Another procedure is suggested based on mass and volume measurements aiming at the verification of the mix proportions in the final mortar mixture.

Ultrasonic pulse velocity (UPV) is a nondestructive technique used for the estimation of concrete properties. This paper investigates the use of UPV test in combination with compressive strength test in order to lower the uncertainty of the latter. For this purpose, 23 mixes were used. The uncertainty of converting UPV measuring results into compressive strength was estimated. A function for combining compressive strength test results with UPV measurements is introduced along with a corresponding uncertainty budget.

In the frame of an extended research program dealing with wood shavings and wood sawdust utilization in mortar, thermal conductivity and thermal behavior under various temperatures of mortars containing wood shavings and sawdust as a replacement for a part of the conventional aggregates were studied. Mixes with 0, 30, 50 and 70% replacement of conventional fine limestone aggregates with wood shavings were made. Also, mixes with 0, 10 and 20% replacement of aggregates with wood sawdust were made. The density of fresh concrete and the thermal conductivity of hardened concrete were determined. Thermal conductivity was determined with the guarded hot plate method according to standard ΕΝ 12667:2001. Specimens were also submitted to 100, 200, 300, 400, 500 and 600 °C. Flexural and compressive strength were determined 24 h after thermal strain. Results showed that thermal conductivity decreased when volume replacement increased, both for the use of wood shavings and sawdust, thus improving the thermal properties of mortar. Flexural and compressive strength exponentially decrease as exposure temperature increases.

According to 2013/59/Euratom Directive, the activity concentration index (ACI) is required to be estimated for each building material that is of concern from a radiation protection point of view. This index applies to building materials and not to constituents that cannot be used as building materials themselves. Fly ash is a byproduct of coal-fired power plants and is one of the main constituents of cement. The radioactivity in fly ash that is produced by Greek lignite power plants cannot be considered insignificant. For example, in the case of the Megalopolis power plant, the concentration for radioisotopes of the ²²⁶Ra chain is found to be about 1 kBq/kg. Since natural radionuclide concentrations, which are harmful to human health in terms of radiation exposure, exist in fly ash, ACI should be assessed for building materials containing fly ash. The present study evaluates the ACI of concrete containing fly ash cement when used in multistory residential buildings. Results showed that cement produced in Greece by the three main Greek cement production plants, containing lignite fly ash, and used as a material for concrete multistory constructions, should not be considered as “of concern from a radiation protection point of view”. Each country that wishes to evaluate the use of fly ash into constructions should repeat the method for the ACI uncertainty budget proposed in this study, to assess whether it significantly exceeds the reference value (whether it is of concern from a radiation protection point of view).

The Activity Concentration Index (ACI), defined in Directive 2013/59/Euratom, serves as a criterion for the radiological significance of Naturally Occurring Radioactive Materials (NORMs) concentrated in building materials, considering related exposures due to the external gamma radiation field but not due to radon concentration levels. This study proposes a simple way of applying the ACI to interior spaces when concrete is the dominant construction material. Three calculation methods were examined, using four spaces within existing buildings, namely Method A, using the building elements’ mass proportions as a weighting factor; Method B, using only the geometrical characteristics of the internal space; and Method C, combining the mass proportions and inverse square distances. This methodology proposes a way of calculating the ACI based on data provided by existing studies about NORM concentrations in building materials and, thus, no sampling and subsequent NORM concentration measurements were required. The spatial data could be easily determined using either building plans or in situ measurements, using a handheld laser distance meter. The advantages and disadvantages of all three methods were analyzed, along with a comparison to in situ gamma radiation field measurements, performed with a portable Geiger–Müller detector. All the methods showed proportionality to the measured values. Method C was found to be the most suitable, especially for existing buildings, and Method A is recommended for early-stage design assessments.