Sound propagation over soft ground without and with crops and potential for surface transport noise attenuation

Growing demand on transportation, road, and railway networks has resulted in increased levels of annoyance from road traffic. Optimized use of green surfaces in combination with vegetation may be desirable as a method for reducing the noise impact of road traffic in urban and rural environments. Sound propagation over soft ground and through crops has been studied through outdoor measurements at short and medium ranges and through predictions. At lower frequencies, ground effect is dominant, and there is little or no attenuation due to crops. At higher frequencies above 3–4 kHz, the attenuation in crops is dominant. It was also found that the ground effects and the influence of crops can be treated independently and can be added to obtain the total effect. Sound attenuation by crops is the result of multiple scattering between the stems and leaves, loss of coherence, and viscous and thermal losses due to foliage. The major contribution is associated with viscous and thermal losses. A model for sound attenuation by vegetation is proposed. Insertion losses for a typical road traffic noise source have been calculated that result either by replacing hard ground with different types of acoustically soft ground or by growing crops along the road sides

Impact of repairs on embodied carbon dioxide expenditure for a reinforced-concrete quay

Studies on structural repair using life-cycle analysis are still lacking the environmental impact of repair actions. This research work shows that the choice of the best repair option for reinforced-concrete structures is a function of long-term environmental impact, considering the longevity of maintenance intervention and embodied carbon dioxide expenditure. The purpose of this work was to assess the lifetime of a quay superstructure exposed to an aggressive marine microenvironment by using a probabilistic performance-based approach and then to select the best repair option for its reinforced-concrete structures. The comparison is made for reinforced-concrete service life using three different concrete types and two different corrosion inhibitors. Longevity and embodied carbon dioxide were predicted for the expected number of repair actions per 100 years. It is shown that concretes may have a higher impact at the outset, although they result in a much lower impact across the service life of the structure

Exposure of mortars to cyclic chloride ingress and carbonation

The presence of chloride ions is one of the primary factors causing the degradation of reinforced concrete structures. An investigation to monitor ingress of chlorides during a 24-week wetting and drying exposure regime to simulate conditions in which multiple-mode transport mechanisms are active was conducted on a variety of binders. Penetration was evaluated using free and total chloride profiles. Acid extraction of chlorides is quantitatively reliable and practical for assessing penetration. X-ray diffraction was used to determine the presence of bound chlorides and carbonation. The ability of the cement blends to resist chloride penetration was, from best to worst, ground granulated blast-furnace slag, microsilica, pulverised-fuel ash, Portland cement. The effect of carbonation on binding capability was observed and the relative quantity of chlorides also showed a correlation with the amount of chlorides bound in the form of Friedel’s salt