International audienceWhile LCA (Life Cycle Assessment) is considered to yield either generic or regionally/technologically specific data on products, this method's implementation can reveal a certain variability due to the nature of the local industrial process as well as to heterogeneous site characteristics in the case of natural aggregate production. Energy consumption and the release of atmospheric emissions from aggregate production processes have been investigated in this study at three quarry sites, which encompass two types of rock (and include explosives). This paper describes the methodology adopted for the specific local production investigation and offers results for the three quarry sites using seven indicators derived from the LCA framework. Site characteristics and differences have been assessed in terms of plant equipment and off-road vehicles, and a detailed description is provided of the grading conducted onsite. It is found that fine grading consumes more energy for production, given the fact this type of grading is recycled inside the plant. This assessment has been performed for 1 ton of aggregate produced during 1 year and with distinction in grading category. Results indicate that the discrepancy in local energy consumption due to site differences lies within an interval between −9.5% and +13.7%, while the interval for impacts is situated at −24.5% to +27.5% whereas for global warming potential the range is from −15.4% to +12.9% as a maximum. Explosives are assumed to contribute less than 1% to the total impacts. Both the electrical energy and fossil fuel consumption ratios are displayed. The upstream processes specific to electricity production significantly contribute to human toxicity potential and ecotoxic potential indicators, as for other indicators and also diesel production (all indicators) the contribution is in proportion close to site results ones. However, this study indicates that an environmental load decrease may be investigated with respect to quarry processes as well as equipment age and use

In this work, a new laboratory test method is developed to characterise the relationship between rolling resistance and macrotexture of road surfaces. This test would allow a fast characterisation and comparison of different wearing courses in terms of rolling resistance. Description of the test machine, samples and test protocol is provided. The effect of influential factors such as speed, temperature and surface texture on the test results is evaluated. Particular attention is paid to the relationship between surface macrotexture and rolling resistance. The macrotexture of the samples is characterised using the measured surface profiles. The partial profile envelopment by the rubber and its effect on the results is simulated by applying different filters to the surface profiles. Obtained results show that by considering the envelop profile a good correlation between surface macrotexture and rolling resistance can be observed. The laboratory results are in good agreement with those obtained using the road test.

Road skid resistance decreases under traffic and climate actions. For a surface made of bituminous concrete, the skid resistance evolution involves a removal of the bitumen layer and a polishing of the aggregates. Previous researches have been focused on polishing mechanisms and less is known about bitumen removal phase. This paper presents a laboratory study to better understand the behavior of the stone mastic asphalt under simulated actions of traffic. Due to its formulation, this bituminous concrete contains more bitumen than other materials used for road surfacing. Polishing tests are performed on circular cores using tWehner/Schulze machine, which simulates the traffic-induced polishing by means of rolling rubber cones and measures the tire friction by means of sliding rubber pads. Tests are stopped at predefined numbers of passes for friction measurements, 3D cartographies of surface texture and scanning electron microscopic observations of the cores' surface. Statistical tests are performed to identify relevant texture parameters to explain friction evolution. During bitumen removal phase (i.e. before 20,000 passes of polishing), Ssc (average curvature of peaks) and Sdq (average quadratic slope of asperities) are correlated with friction values. After 50,000 passes, volume parameter Vvc is more adapted due to the abrasion of asphalt mix surface. Then, scanning electron microscopic observations show that a layer composed by bitumen and particles (small aggregates and sand) is a third-body surrounding aggregates, which evolves in thickness and size of aggregates during polishing. The system composed of the aggregates, the bitumen–particles layer and the polishing cones can be assimilated to a tribosystem with a tribological circuit at the interface. The bitumen–particles layer acts as an internal flow, before leaving the contact area. The movement of the layer under the shear stress induced by the polishing cones explains the ejection of big aggregates and the heterogeneity of the layer around aggregates.

In this paper, a versatile drum setup for measuring rolling resistance of small wheels is presented. The purpose is to provide a flexible setup for testing of models for rolling resistance under controlled circumstances. To demonstrate this, measurements of rolling resistance with a series of sandpapers of different grit sizes representing surface textures were carried out. The measurements show a clear increase in the rolling-resistance coefficient with increasing surface roughness, rolling speed and load. Numerical calculations in the time domain for a visco-elastic contact model run on equivalent surfaces agree with the trends found experimentally. We conclude that this approach to simplifying the experiment in order to obtain a high degree of control, accuracy and repeatability is useful for validating and testing models for calculating the rolling resistance for a given surface texture.

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