Morea F.,CONICET |
Marcozzi R.,LEMIT CIC |
Castano G.,LEMIT CIC
Construction and Building Materials | Year: 2012
Warm Mix Asphalts (WMAs) have been developed with the objective of minimizing the CO 2 emissions in the production and placement process of Hot Mix Asphalts (HMAs) by reducing temperatures at which these are mixed and compacted. However, this reduction must not affect the manufacturability and final performance of the mixture. WMA additives allow reducing the production temperature while maintaining mixture workability during the mix process and without compromising the final performance of concrete asphalt. There are different additives, some of which modify the rheological behavior of asphalts (wax or paraffin) while others, in theory, allow for unaffected rheological behavior (chemical additives). In this work the differences between the rheological properties of conventional and polymer modified asphalts, with and without chemical tensoactive additives, obtained from HMA and WMA, were studied by a Dynamic Shear Rheometer (DSR). Additionally, rutting resistance and moisture susceptibility were evaluated in these mixtures. The rheological properties of polymer modified asphalt were affected by the WMA additives, while in the conventional asphalt the rheological properties were not significantly affected. The WMA additives improved the workability of the mixtures in the production process. Performance improvements in the submerged wheel-tracking test were observed for WMA when additives were used, yielding results similar to HMA. © 2011 Elsevier Ltd. All rights reserved.
Rico Y.,LEMIT CIC |
Bidegain J.C.,LEMIT CIC
Quaternary International | Year: 2013
A sedimentary sequence called "Fogones de la Costa" located at 38° 17' 35″ S, 57° 50' 50″ W, on the coastal cliffs, south of Miramar city, was studied from geological, paleomagnetic and rock magnetic viewpoints. The stratigraphic column shows normal and reverse polarity records associated with chrons and subchrons of magnetopolarity. The younger sediments were assigned to the Brunhes Polarity Chron (<0.78Ma) and the older sediments of the middle and lower part of the profile were assigned to Upper Matuyama (0.99-0.78Ma), Jaramillo (1.05-0.99Ma) and Middle Matuyama (1.78-1.05Ma). A very short normal polarity record between cycles V and VI, at the base of the cliff, suggests the presence of a condensed record of Cobb (or Olduvai?). The oldest reverse polarity layers at the base of the profile should be related to the lower Matuyama (>1.9Ma). On the basis of these data, the sequence should span from the Lower Pleistocene to the Holocene, and may be correlated (although partially) with the geological formations of San Andrés, Miramar, and Arroyo Seco described in coastal cliffs north of Miramar. The model of behavior of concentration parameters (κ, χ, Ms and Mr) is in agreement with that determined in other loess sections studied in northern Buenos Aires province. The values of the concentration of magnetic parameters decrease with increasing pedogenesis and weathering of the original material (loess and loess-like). This is a behavioral feature, independent of the carrier agent (wind or water). The medium silt fraction is dominant over the other grain sizes. In that fraction, the amount of magnetic minerals increases significantly. Conversely, the layers corresponding to paleochannels and paleolagoons show a decrease of magnetic minerals, the medium silt fraction also decreases, and the very fine silts and clays increase. © 2013 Elsevier Ltd and INQUA.