Improving the mechanical behavior of pervious concrete using polypropylene and waste rope fibers

Urbanization has led to the damage of infrastructure due to floods and water accumulation on roads and sidewalks. To address this problem, pervious concrete was designed to drain water smoothly. However, pervious concrete has certain drawbacks, such as brittleness and poor tensile strength. To overcome these shortcomings, it is reinforced with fiber. Polypropylene fibers are commonly used for this purpose. On the other hand, managing waste plastic is a major problem as it has a significant environmental impact and requires large areas for landfills. Waste rope fibers (WRF) are among these wastes. There have been very limited investigations on the use of WRF in pervious concrete. Therefore, this study aims to investigate the effect of polypropylene (PP) fibers and waste rope fibers (WRF) on the mechanical and structural properties of pervious concrete. PP and WRF fibers were added in proportions of 0.25%, 0.5%, and 0.75% by volume of concrete. A range of tests (compressive strength, tensile strength, density, permeability, load-deflection behavior, and ductility) were conducted to evaluate the resulting concrete. The results indicated that although the permeability was decreased by adding fibers, the fibers significantly improved the mechanical and structural properties of pervious concrete. The highest values for compressive strength, splitting tensile strength, and ultimate load were 83.4%, 72.4%, and 89.62% for PP fibers-based mixtures, while they were 49.9%, 41.9%, and 102.83% for mixtures made with WRF at an addition rate of 0.5% for both types of fibers. The results also demonstrated that the existence of fibers improved the ductility of the concrete, which means that WRF can be used successfully in producing eco-friendly pervious concrete with better performance than the control specimen.</jats:p

Modified Chrispin-Norman chest radiography score for cystic fibrosis: observer agreement and correlation with lung function

Contains fulltext : 96114.pdf ( ) (Closed access)OBJECTIVE: To test observer agreement and two strategies for possible improvement (consensus meeting and reference images) for the modified Chrispin-Norman score for children with cystic fibrosis (CF). METHODS: Before and after a consensus meeting and after developing reference images three observers scored sets of 25 chest radiographs from children with CF. Observer agreement was tested for line, ring, mottled and large soft shadows, for overinflation and for the composite modified Chrispin-Norman score. Correlation with lung function was assessed. RESULTS: Before the consensus meeting agreement between observers 1 and 2 was moderate-good, but with observer 3 agreement was poor-fair. Scores correlated significantly with spirometry for observers 1 and 2 (-0.72<R<-0.42, P < 0.05), but not for observer 3. Agreement with observer 3 improved after the consensus meeting. Reference images improved agreement for overinflation and mottled and large shadows and correlation with lung function, but agreement for the modified Chrispin-Norman score did not improve further. CONCLUSION: Consensus meetings and reference images improve among-observer agreement for the modified Chrispin-Norman score, but good agreement was not achieved among all observers for the modified Chrispin-Norman score and for bronchial line and ring shadows