CFD simulation study and experimental analysis of indoor air stratification in an unventilated classroom: A case study in Spain.

Health problems and respiratory diseases are associated with poor indoor air ventilation. We investigated the air quality inside a classroom-laboratory where no ventilation is provided. The case of study, consisting of an internal enclosure, is located at the Escuela Técnica Superior de Edificación (ETSEM) of Madrid (Spain). The high height favours air stratification which is analysed in terms of temperature and CO2 spatial distribution. Temperature, air humidity, atmospheric pressure and CO2 concentration measurements were taken in time at three different height locations. A CFD numerical model was established to analyse air quality. Flow circulation is derived by solving full 3D Navier - Stokes governing equations, coupled with the thermal problem. The diffusion problem of the CO2 produced by the inner occupants is then derived from the kinematics solution. Three scenarios were taken into account: occupants seated (1), standing (2), half seated, half standing (3). Results clearly show the air stratification as a result of density gradient, which is in turn determined by temperature difference between the occupants and the surrounding air. Temperature prediction maximum relative error is contained to 3.5 %. As expected, CO2 concentration increases over time, reaching maximum values depending on the configuration considered and height location.

Flexural Capacity of Concrete Beams with Basalt Fiber-Reinforced Polymer Bars and Stirrups.

The flexural properties of six 120 × 300 × 4500 mm concrete beams reinforced with bars made from basalt fiber-reinforced polymer (BFRP) basalt fibers and concrete stirrups were investigated. The beams contained different concrete compositions (with or without basalt fibers). Steel and BFRP bars were used as longitudinal and shear reinforcement. As expected, all the beams failed by the crushing of the concrete in the top compression fibers because of using BFRP bars. Beams with BFRP bars should be designed to fail by concrete crushing because it is safer than a brittle failure of the bars. The beams with composite reinforcement were characterized by the greatest number of cracks with the largest crack width. The use of basalt fibers resulted in slightly reduced cracks in beams. The most significant deflections were recorded for the beams with BFRC composite reinforcement, the smallest for FRC beams. Adding basalt fibers to the concrete resulted in slightly reduced deflection of FRC beams compared to RC beams and significantly reduced deflection compared to BFRC beams. Results showed that introducing basalt fibers to the concrete increased curvature ductility of these beams. A theoretical analysis of flexural capacity showed that the ACI standard design is more similar to experimental values (0.87). A more restrictive standard, as it turns out, is the fib Model Code (0.68).

Indoors ventilation in times of confinement by SARS-CoV-2 epidemic: A comparative approach between Spain and Italy.

With the arrival of the SARS-CoV-2 coronavirus, the scientific academia, as well as policymakers, are striving to conceive solutions as an attempt to contain the spreading of contagion. Among the adopted measures, severe lockdown restrictions were issued to avoid the diffusion of the virus in an uncontrolled way through public spaces. It can be deduced from recent literature that the primary route of transmission is via aerosols, produced mainly in poorly ventilated interior areas where infected people spend a lot of time with other people. Concerning contagion rates, accumulated incidence or number of hospitalizations due to COVID-19, Spain, and Italy have reached very high levels. In this framework, a regression analysis to assess the feasibility of the indoor ventilation measures established in Spain and Italy, with respect to the European framework, is here presented. To this aim, ten cases of housing typology were and analyzed. The results show that the measures established in the applicable regulations to prevent and control the risk of contagion by aerosols are not adequate to guarantee a healthy environment indoors. The current Italian guidelines are more restrictive than in Spain, yet the ventilation levels are still insufficient in times of pandemic.

Study of the Mechanical and Physical Behavior of Gypsum Boards with Plastic Cable Waste Aggregates and Their Application to Construction Panels.

The objective of this study was to analyze the physico-mechanical properties of gypsum boards including plastic waste aggregates from cable recycling. The plastic cable waste is incorporated into the gypsum matrix without going through any type of selection and/or treatment, as it is obtained after the cable recycling process. In the experimental process, gypsum boards of different dimensions were manufactured and tested for their Young's modulus, shock-impact resistance, flexural strength, thermal conductivity, and thermal comfort. The results obtained show a significant increase in the elasticity of the boards with plastic waste (limited cracking), compliance with the minimum value of flexural strength, and a slight improvement in the thermal conductivity coefficient (lower energy demand) and surface comfort (reduced condensation and greater adherence). Therefore, the analyzed material could provide a suitable alternative to currently marketed gypsum boards, contributing to sustainable construction not only in new constructions, but also in building renovations.