No abstract

This article focuses on the impact of fly ash from the combustion of municipal sewage sludge (FAMSS) as a cement additive in the amounts of 5%, 10%, 15%, 20% and 25% (by mass) on selected concrete properties. In the course of the experimental work, water penetration depth and compressive strength measurements were made at various periods of curing (from 2 to 365 days). In addition, the potential impact of FAMSS on the natural environment was examined by determining the leachability of heavy metals. FAMSS-modified concretes showed small values of water penetration depth (lower than 50 mm), as well as good compressive strength (reaching minimum class C30/37 after 130 days of maturing)—similar to the compressive strength obtained for conventional concrete. In addition, the partial replacement of cement with FAMSS has environmental benefits, expressed as a reduction in CO2 emissions. In addition, study has shown that compliance with environmental requirements is associated with heavy metal leaching.

On the basis of the registered indications of the water meter, a study on the size and variability of water consumption on the WULS campus in the academic years 2012/16 is presented. The average specific water consumption at a time when classes are implemented amounted to 26.6 dm 3 per student per day for full-time studies student and 19.7 dm 3 per student per day for the student part-time studies. During the holiday season, the rates are lower at 18.4 and 11.8 dm 3 per student per day, respectively. These ratios were determined without taking the water consumption in the dorms into account. The daily peaking factor amounted (N d) to 1.36, while the hourly peaking factor (N h), reached 1.71. Within the week cycle, the highest water consumption was observed in Tuesdays and the lowest-in Sundays. The average Tuesday demands are 40% higher than the Sunday demands. The water consumption peaks during the day occur between 11 a.m. and 1 p.m. as well as 11 p.m. and 1 a.m. The hourly structure of the water distribution in the WULS-SGGW campus is similar to the weekend structure of water distribution in multi-family residential buildings, with the exception of the later occurrence of the evening summit.

The article presents the results of tests of minor head losses through PVC and PP elbows for a flow of water and mixtures of water and sand with grain sizes of up to 0.5 mm and concentrations of 5.6 g·L−1, 10.84 g·L−1, and 15.73 g·L−1. The tests were carried out at variable flow velocities for three elbow diameters of 63 mm, 75 mm, and 90 mm. The flow rate, pressure difference in the tested cross-sections, and temperature of the fluids were measured and automatically recorded. The results of the measurements were used to develop mathematical models for determining the minor head loss coefficient as a function of elbow diameter, sand concentration in the liquid, and Reynolds number. The mathematical model was developed by cross validation. It was shown that when the concentration of sand in the liquid was increased by 1.0 g∙L−1, the coefficient of minor head loss through the elbows increased, in the Reynolds number range of 4.6 × 104–2.1 × 105, by 0.3–0.01% for PP63, 0.6–0.03% for PP75, 1.1–0.06% for PP90, 0.8−0.01% for PVC63, 0.8–0.02% for PVC75, and 0.9–0.04% for PVC90. An increase in Re from 5 × 104 to 2 × 106 for elbows with diameters of 63, 75 and 90 mm caused a 7.3%, 6.8%, and 6.0% decrease in the minor head loss coefficient, respectively.