Effect of Different Types of "Dry Way" Additions in Porous Asphalt Mixtures.

Polymers are widely used to improve the mechanical performance of asphalt mixtures. Among them, styrene butadiene styrene (SBS) is the most commonly used, especially in the wet modification of virgin bitumen. This method, which is extensively utilized, has several advantages, but also some disadvantages, concerning its performance (such as the risk of instability or a lack of homogeneity) and logistical management (such as the need for special equipment, the transport of materials, and the dependence on the refinery that modifies the bitumen). This paper analyses the use of the most conventional types of polymers (two types of SBS, one type of BS, and rubber from end-of-life tires), dry added, as an alternative method. They have been used in porous asphalt mixtures. This type of bituminous mixture is usually designed with commercial polymer-modified bitumen, due to the mechanical requirements, and it is very sensitive to the properties of the binder used. The mechanical behavior of experimental porous asphalt mixtures has been significantly improved, especially in the case of SBS, although the performance did not reach that of commercial polymer-modified bitumen. The results have shown that the dry method is a suitable and feasible option to manufacture modified mixtures, especially considering its advantages, from a logistical viewpoint, in comparison with the wet method.

Effect of Sodium Chloride on the Modulus and Fatigue Life of Bituminous Mixtures.

Bituminous mixtures are not perfectly elastic materials, so their viscoelastic properties play a decisive role in knowing their behavior. This research aims to find out this behavior through the values of the resilient modulus, the dynamic modulus, and the fatigue life for asphalt concrete and porous mixtures when they are influenced by the presence of salt (NaCl, sodium chloride). The aforementioned influence of salt has been evaluated by utilizing three different methods: submerging specimens of bituminous mixture in salt water; introducing salt into the specimens as if it was aggregate and immersing the aggregate in salt water; and drying it and then manufacturing the bituminous mixture with it. As the results indicate, the mixtures submerged in salt water do not show large differences in comparison to the reference mixtures for hot mix asphalt and porous mixtures. However, for hot mix asphalt in which salt has been added as aggregate, the resilient modulus is greater than in the reference mixture. For the bituminous mixtures in which an aggregate saturated in salt water has been used for its manufacture, the results of the resilient modulus test, dynamic modulus test, and fatigue life test are lower than in the reference mixture, especially when the specimens are submerged.

Modification Tests to Optimize Highway Construction in Crown of Slate Random Embankments with Compaction Quality Control.

The compaction control of random fills has developed very little due to the limitations of particle sizes, with methods usually using a simple procedural control. In order to develop new quality control procedures for random slate filling, the necessary field work and laboratory tests were carried out. New test procedures for wheel-tracking or settlement tests have been successfully investigated. A total of 4500 in situ measurements of density and 580 topographic settlements, 960 wheel-tracking trolley tests and more than 130 slab rolling tests have been determined. An analysis of variance (ANOVA) has been carried out, obtaining correlations between tests in order to replace the deductibles. The variables that were used to analyze variance were the average lot density, the average settlement between last and first roller pass, the average wheel impression after test carriage, the first vertical modulus of the plate bearing test (PLT), the second vertical modulus of the PLT and the relation between second and first modulus of the PLT. The research proposes a new procedure for the quality control of the compaction of the randomized slate filling used in the crown area.

Modification Tests to Optimize Compaction Quality Control of Granite Rockfill in Highway Embankments.

Particle size can be a problem in terms of rockfill compaction control methods, with little practical development of these techniques. The necessary fieldwork and laboratory tests were carried out to develop new quality control procedures for granite rockfill. This involved the revision of certain tests like the wheel-tracking or topographic settlement tests. More than 1100 in-situ density and moisture content measurements were performed for this research. In addition, more than 220 topographic settlements and 250 wheel-tracking carriage tests were carried out. The quality control processes were completed with 24 plate bearing tests. The results of granite rockfills were classified according to their use in the different areas of core or crown. Possible evidence of statistical correlations between compaction control tests was identified. An analysis of variance (ANOVA) was performed. When testing proved relationships between them, the replacement of one by the other was evaluated by deduction. Finally, the study suggests new procedures for compaction quality control of granite rockfill for its application in core and crown.

Laboratory analysis of the infiltration capacity of interlocking concrete block pavements in car parks.

Interlocking concrete block pavements (ICBPs) have been widely used in car parks to reduce runoff. Researches have demonstrated that clogging is the most influential factor in the reduction of the infiltration capacity of this type of permeable pavement. Nevertheless, there is no laboratory study of the infiltration performance of ICBPs that combines clogging levels with variables related with the topography of car parks such as runoff surface length (R(SL)) and surface slope (S(S)). This paper studies the infiltration behaviour of ICBP during their operational life in a car park using an improved version of the Cantabrian Fixed (CF) Infiltrometer. This laboratory device simulates direct rainfall and runoff from adjacent impervious areas over an ICBPs surface of 0.25 m(2) for different slopes (0, 3, 5, 7 and 10%) and three scenarios of clogging (surface newly built, surface clogged and surface clogged with maintenance). This paper presents the results of the tests and a statistical analysis based on three regression models (corresponding to each clogging scenario) depending on the R(SL) and S(S) variables. All models passed a confidence level of 95%, presenting high R(2) values and showing that R(SL) is a more influential variable than the S(S) for all clogging scenarios.

Long-term analysis of clogging and oil bio-degradation in a System of Catchment, Pre-treatment and Treatment (SCPT).

Runoff contamination has motivated the development of different systems for its treatment in order to decrease the pollutant load that is discharged into natural water bodies. In the long term, these systems may undergo operational problems. This paper presents the results obtained in a laboratory study with a 1:1 scale prototype of a System of Catchment, Pre-treatment and Treatment (SCPT) of runoff waters. The analysis aims to establish the operational behaviour of the SCPT in the long term with respect to oil degradation and hydraulic conductivity in the geotextile filter. It is concluded that bio-degradation processes take place inside the SCPT and that hydraulic conductivity of the geotextile filtration system decreases slowly with successive simulated runoff events.