Porosity of porous concrete is an important parameter used for both mechanical properties of pavement and environmental design. Nano-particles have received increasing attention and have been used in various fields such as concrete to develop novel materials with interesting functions, all because of dedicated physical and chemical properties of nanoparticles. The authors describe new findings of an experimental work on mechanical properties and permeability of porous concrete containing nano-silicon dioxide. Plain porous concrete and porous concrete containing micro-silicon dioxide have been studied as control materials. Twenty-eight-day results showed higher compressive and flexural strengths for porous concrete containing nano-silicon dioxide compared with those of plain porous concrete with the same water–cement ratio. It was demonstrated that nano-silicon dioxide was more effective than micro-silicon dioxide in enhancing porous concrete flexural strength. Samples with 5% nano-silicon dioxide by weight of binder presented the highest mechanical properties, in which the flexural and compressive strength of porous concrete were enhanced by 56% and 48%, respectively. From experimental study of the permeability behavior of porous concrete containing nano- and micro-silicon dioxide, it appeared that nano-silicon dioxide and micro-silicon dioxide could both reduce water penetration through porous concrete; however, micro-silicon dioxide was found more effective for equal nanoparticles and material voids.

Weaving segments are among the most important segments in any kind of facility. One of their key features is their maximum length (Lwmax), which determines the performance of the facility as a weaving or separate merge and diverge segments. Based on an equation in the Highway Capacity Manual (HCM 2016), only two variables VR (volume ratio) and Nwl (number of weaving lanes) influence this length. However, certain cases can be found in which traffic conditions are different but Nwl and VR values are equal. In this study, three separate weaving segments in Tehran, Iran were used and their data were collected to further analyze the influence of the traffic parameters. Calibration of field data was performed using GEH values of freeways and ramps for simulation and field traffic volumes. The simulation was therefore used on the basis of different traffic and geometric parameters, and the effects of these parameters on Lwmax were carefully observed. There were 184 simulated scenarios in Aimsun using data collected from the three weaving segments in Tehran plus simulation. In these scenarios, two geometric parameters (Nwl and Lwmax) and four traffic parameters were considered variable. It was found that for Nwl = 2 the accepted regression model containing three new variables has an R2 value equal to 0.95, and for Nwl = 3 two of the three variables were used for the model produced with an R2 value equal to 0.7.

No abstract

No abstract