Developing non-destructive methods (NDT) that can deliver faster and more accurate results is an objective pursued by many researchers. The purpose of this paper is to present a new approach in predicting the concrete compressive strength through means of ultrasonic testing for non-destructive determination of the dynamic and static modulus of elasticity. For this study, the dynamic Poisson’s coefficient was assigned values provided by technical literature. Using ultra-sonic pulse velocity (UPV) the apparent density and the dynamic modulus of elasticity were determined. The viability of the theoretical approach proposed by Salman, used for the air-dry density determination (predicted density), was experimentally confirmed (measured density). The calculated accuracy of the Salman method ranged between 98 and 99% for all the four groups of specimens used in the study. Furthermore, the static modulus of elasticity was deducted through a linear relationship between the two moduli of elasticity. Finally, the concrete compressive strength was mathematically determined by using the previously mentioned parameters. The accuracy of the proposed method for concrete compressive strength assessment ranged between 92 and 94%. The precision was established with respect to the destructive testing of concrete cores. For this research, the experimental part was performed on concrete cores extracted from different elements of different structures and divided into four distinct groups. The high rate of accuracy in predicting the concrete compressive strength, provided by this study, exceeds 90% with respect to the reference, and makes this method suitable for further investigations related to both the optimization of the procedure and = the domain of applicability (in terms of structural aspects and concrete mix design, environmental conditions, etc.).

Air quality in school environments is of particular interest due to the significant amount of time children spend in these settings. Children, being a particularly sensitive demographic, are exposed to various pollutants at school or kindergarten. In this regard, our studies have focused on monitoring the concentrations of three main categories of pollutants: VOCs (volatile organic compounds), VICs and PM (particulate matter). We conducted two experimental campaigns in seven classrooms within public educational institutions. The average concentration values of TVOC (total volatile organic compounds) ranged from 554 µg/m³ to 2518 µg/m³, of CO₂ from 1055 ppm to 2050 ppm, of NH₃ (Ammonia) from 843.2 µg/m³ to 1403.4 µg/m³, of PM2.5 from 25.1 µg/m³ to 89.9 µg/m³, and of PM10 from 63.7 µg/m³ to 307.4 µg/m³. In most instances, the registered values exceeded the limit values set by national or international regulations. Furthermore, this study highlights the significant impact of a heat recovery ventilation system in improving indoor air quality by substantially reducing the levels of CO₂ and PM. However, it also underscores the need for further measures to more efficiently reduce TVOC concentrations. The aim of our paper was to enhance the understanding of pollution levels in school environments, increase awareness of the importance of indoor air quality, and highlight the adverse effects of polluted air on the health of occupants.

Indoor air quality (IAQ) and energy consumption (Q) are well-known building estimators, but they are used separately. Energy consumption is used during the design stage, while IAQ is used during operation. The novelty of our approach is that we propose using both estimators simultaneously during building operations. The purpose of this study was to find an adaptive ventilation strategy that maintained good indoor air quality with minimal energy consumption. The second novelty of our approach consists of IAQ estimation. While the operation of ventilation systems depends only on the indoor carbon dioxide (CO₂) concentration at present, our novel approach uses a more global IAQ index that includes four different air pollutants. Physical models are used for the hourly prediction of the two indices: global IAQ and Q. This study presents a comparative analysis of several ventilation operations strategies: fixed versus adaptive. The main findings show that a decrease in the ventilation rate, n_a, from 3.5 h⁻¹ to 2.0 h⁻¹ leads to a diminishment in energy consumption of 42.9%, maintaining the global IAQ index under the limited health risk value (VRL). Moreover, an adaptive ventilation strategy of n_a, maintaining the global IAQ index value under VRL, achieves a further reduction in energy consumption of 72.9%, highlighting its efficiency.

Nowadays, indoor air quality (IAQ) and the energy performance of buildings are two main scientific and technical challenges because they are in direct connection with human health and the depletion of energy resources. In this study, we analyzed the influence of an outdoor air flow introduced through a mechanical ventilation system, focusing on the two aforementioned topics. A standardized ventilation rate (25 m³/h/person) led to an increase in the indoor O₃ concentration (from 5 μg/m³ to 50 μg/m³) and, simultaneously, to a decrease in the indoor CO₂ concentration (from 2000 mg/m³ to 800 mg/m³), a decrease in the PM_2.5 concentration (from 300 μg/m³ to 150 μg/m³), and the maintenance of a constant indoor HCHO concentration. In our study, a new, single indoor air quality index, I_IAQ, is proposed. This new index presents different implications: on the one hand, it has the ability to simultaneously take into account several pollutant species, and on the other hand, it can prioritize the ventilation strategy that responds to the extreme values of a certain pollutant. Moreover, indoor air quality classes were elaborated, similar to energy classes. The possibility of using this new index simultaneously with energy consumption may lead to ventilation strategies that are adaptative to dynamic outdoor pollutant concentrations.

The depletion of non-renewable resources is followed by severe ecological and social impacts, and the heavily usage of raw, virgin resources leaves significant, long lasting footprints. In order to move into a more sustainable economic system, a recently more frequently discussed approach for overcoming the current linearity of product lifecycles is the concept of circular economy (CE). The transition to a more circular economy, where the value of products, materials and resources is maintained and circulated (by recycling activities) in the economy for as long as possible, is an essential contribution to the EU’s efforts to develop a sustainable, low carbon, resource efficient and competitive economy. In this context, ecological solutions consisting of materials which helps carbon sequestration and necessitates small amounts of energy for production are becoming increasingly popular from buildings construction point of view, namely: the raw material is cheap and in large quantities; have low thermal conductivity; are from a renewable source. The paper presents an analysis of some innovative thermal insulating products made from renewable or recycled resources (recycled plastics, low quality wool, straw, cellulose), their thermal conductivities over a temperature interval and acoustics coefficients (α_s, α_w), the purpose being to inform the market in order to increase the present level of technical knowledge and to facilitate the implementation of high energy efficiency buildings with products from recycled materials or using industrial by-products.

In the frame of the 2030 Agenda, adopted also by Romania, Good Health and Well-being for people is the third of the Sustainable Development Goals (SDGs) settled by the United Nations General Assembly. Because human health concerns are in the core of the mission of sustainability, health and sustainable development are strongly interlinked. Numerous worldwide studies specify that many health problems are associated with the air pollutants and their interactions with comfort parameters. Therefore, the approaches towards more sustainable buildings or construction products must take into consideration potential human exposure to pollutants and associated health effects. Our studies were conducted in various type of spaces -offices, residential and educational, by the monitoring of the pollutants’ concentrations and the comfort parameters. Regarding to the CO₂ concentration, it was observed that the recorded average values were between 888 and 1668ppm, in offices, between 1053 and 1389 ppm, in residential, and between 1720 and 4302ppm, in educational spaces, in all cases above the limit of 800ppm. The average values of CO concentration varied between 0.35 and 3.90 ppm, under the limit of 50 ppm. It was observed that the temperature and relative humidity have a determinant influence on the level of monitored pollutants.