Deterioration of PVC floor covering due alkaline moisture

Concrete as alkaline (pH ∼12,5) and moist material can cause deterioration of polyvinyl chloride (PVC) floor coverings and adhesives through alkaline hydrolysis. Attempts to prevent alkaline hydrolysis have mainly been made by installing PVC floor coverings above ‘dry-enough’ concrete or by using self-levelling low-alkali (pH ∼11…11,5) screeds between concrete and floor coverings. In this study, screed, adhesive and PVC floor covering combinations have been varied by using different floor covering conditions in laboratory test series. VOC emissions have been analysed from flooring material samples (Bulk-VOC). The test samples have been measured for two to three years after installing floor covering. According to the results, a 5 mm layer of low-alkali screed (pH less than 11,5) will effectively protect PVC flooring against alkaline hydrolysis. It could also be concluded that the pH level immediately under floor covering has a better correlation with VOC emission than the RH of concrete in the moment of installing the floor covering.

Experimental and CFD Investigation of a Modified Uneven-Span Greenhouse Solar Dryer in No-Load Conditions under Natural Convection Mode

An uneven-span modified greenhouse dryer was constructed and tested in no-load conditions under natural convection mode under the weather conditions of Marrakech, Morocco, for two distinct days. Moreover, a CFD evaluation of the uneven-span greenhouse dryer was performed as tool to visualize the air temperature distribution inside the dryer. For validating the CFD model, the temperature variations along the hours of the day were compared to the experimental results. A good agreement is obtained between the computed and measured inside air temperature with a difference not exceeding 8.46°C, with a correlation coefficient ( r ) and root mean square percentage deviations ( e ) 0.94 and 8.17, respectively. Furthermore, the maximum inside air temperature was measured to be 56°C and 52°C while the minimum inside relative humidity was measured to be 17% and 12%, for day-1 and day-2, respectively. The benefice of using asphalt as a floor covering material was revealed as an efficient way to heat the inside air at low solar radiations. The performances of the dryer were evaluated by the percentage of net heat gain variation as a way to validate the effectiveness of the dryer. This latter is found to be equal to 46% and 48% for the two days, respectively.

Underfloor heating as a cause of fire

Introduction. The relevance of the topic, addressed in the article, is backed by the fact that modern heating systems, such as the underfloor heating, remain potential sources of fire, despite the improvement in their designs. The purpose of the study is to identify the causes of fires that occur in the process of operation of modern heating systems “Underfloor Heating”; to analyze and generalize the conclusions made by the fire safety experts in respect of the heating systems analyzed in the article.Materials and methods. To assess the flammability of the infrared film underfloor heating, an experiment was conducted by the experts: the process of underfloor heating was simulated under normal environmental conditions at room temperature.Results and discussion. The experiment has shown that the floor covering, made of the material capable of accumulating heat, is the most dangerous one, although its small area prevents its disconnection from the thermal sensor. When dismantling the construction, the co-authors found out that the foil insulator had been melting in the area of maximal temperatures. Over the course of seven hours of operation, the temperature exceeded 120 ºC, and after that the odor of products of thermal decomposition of a synthetic product appeared.Conclusions. Despite all the features of advanced underfloor heating systems, their automated operation and transformation, they remain potentially flammable. Modern underfloor heating systems can take fire both as a result of violation of the fire precautions in case of non-compliance with the requirements for the operation of heating devices, and as a result of overheated film heaters located under the floor covering.