The sound absorption of a road pavement depends not only on geometric and volumetric factors but also on pore shape factors. In turn, pore shape factors mainly refer to thermal and viscous factors (i.e., thermal and viscous effects that usually occur inside porous materials). Despite the presence of a number of studies and researches, there is a lack of information about how to predict or estimate pore shape factors. This greatly affects mixture design, where a physical-based or correlation-based link between volumetrics and acoustics is vital and plays an important role also during quality assurance and quality control (QA/QC) procedures. Based on the above, the objective of this study is to link mixture volumetrics and pore shape factors. In particular, 10 samples of a porous asphalt concrete were tested in order to estimate their thickness, air voids content (vacuum-sealing method, ASTM D6857/D6857M), sound absorption coefficient (Kundt’s tube, ISO 10354-2), airflow resistivity (ISO 9053-2), and permeability (ASTM PS 129). Subsequently, two models (herein called STIN and JCAL) were used to derive both volumetrics and pore shape factors from the estimated parameters listed above, and statistical analysis was carried out to define correlations among the parameters and models performance. Results confirm the complexity of the tasks and point out that estimates of the pore shape factors can be derived based on mixture volumetrics. Results can benefit researchers (in acoustic and pavement mixtures) and practitioners involved in mix design and pavement acceptance processes.
Air pollution is an important issue worldwide. Solid components in air (particulate matter, PM) originate
from a variety of natural or anthropogenic sources and have different morphological, physical, and chemical properties.
Their presence in the air also depends on meteorological conditions, such as humidity, rainfall, and wind speed. PM
pollution has adverse effects on environment and human health. Therefore, it is very important to address sources and
processes involved in PM generation. Among the existing sources, a special attention must be paid to PM emissions
from road traffic, i.e., exhaust sources (e.g., fuel combustion) and non-exhaust sources (e.g., road, tyre, brakes). These
traffic-related sources contribute to PM concentrations in cities, and this calls for research into new possible systems
and/or mitigation measures. In light of the facts above, the objectives of this study are 1) To evaluate the contribution
to PM emission from traffic-related sources. 2) To evaluate existing mitigation measures and to identify new ones to
reduce PM production. First results show that: 1) Non-exhaust sources have a different role in PM generation and they
differently affect PM10, PM2.5, and PM0.1. 2) Even if emissions-related regulations have led to reductions in exhaust
emissions from road traffic, other mitigation measures could reduce the non-exhaust part of emissions (e.g., brakes wear,
road wear, and tyre wear). 3) New technologies could be developed to reduce PM from non-exhaust sources.
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