Evaluation of recycled asphalt pavement in Colombia

Reclaimed asphalt pavements are obtained from existing pavements through recovery techniques and are used for new asphalt mixtures production with the inclusion of virgin aggregates and asphalt cement, constituting environmentally friendly mixtures at a lower total cost, by requiring fewer quantities of new materials. This research, unlike the studies found on the subject, focuses on the study of reclaimed asphalt pavement by analyzing its granulometric distribution and asphalt cement content. For this purpose, representative reclaimed asphalt pavement samples were taken from four Colombia cities, to verify their heterogeneity. The obtained reclaimed asphalt pavement was analyzed in the laboratory, to obtain the material granulometric distribution, through extraction and asphalt content tests, following Colombian regulations from the “Instituto Nacional de Vías”. The results show that the granulometry of all cities has a central tendency (average) that moves towards an upper limit in the 2 mm particles. When analyzing the granulometry separately of the four cities, it is observed that they present a different trend in their granulometry, which shows their heterogeneity. The asphalt cement content presented values between 4.0% and 5.0%.

Asphalt concrete mixtures with addition of reclaimed asphalt pavements

The effect of using reclaimed asphalt pavements (RAP) to asphalt concrete mixtures besides their utilization is to reduce the amount of the new bituminous binder and aggregate added to hot mix asphalt. This publication presents studies on asphalt mixtures with an increased up to 40% amount of RAP additive with the simultaneous use of 2 types of added bitumen, i.e. 35/50 and PMB 25/55-60. The aim of the paper is the evaluation of the basic mixture properties in a wide range of operating temperatures, as a part of the AC testing at high temperatures, the resistance to rutting at 60° C and indirect tensile strength at 40° C. The assessment of properties at intermediate operating temperatures is based on indirect tensile tests, including: elastic stiffness modulus at 5° C, 15° C and 30° C and static strength at 25° C. The low temperature properties have been tested in water and frost resistance tests by indirect tensile strength ratio. The results of the study were subjected to the analysis of the statistical significance of differences, which showed an improvement in the resistance of AC with the addition of RAP to the formation of permanent deformations and an increase in the stiffness modulus as well as indirect tensile strength. There was no adverse effect of the RAP additive on asphalt mixtures resistance to water and frost action.

Study of the Incorporation of Ladle Furnace Slag in the Manufacture of Cold In-Place Recycling with Bitumen Emulsion

Cold in-place recycling with bitumen emulsion is a good environmental option for road conservation. The technique produces lower CO2 emissions because the product is manufactured and spread in the same location as the previous infrastructure, and its mixing with bitumen emulsion occurs at room temperature. Adding materials with cementitious characteristics gives the final mixture greater resistance and durability, and incorporating an industrial by-product such as ladle furnace slag (of which cementitious characteristics have been corroborated by various authors) enables the creation of sustainable, resistant pavement. This paper describes the incorporation of ladle furnace slag in reclaimed asphalt pavements (RAP) to execute in-place asphalt pavement recycling with bitumen emulsion. Various test groups of samples with increasing percentages of emulsion were created to study both the density of the mixtures obtained, and their dry and post-immersion compressive strength. To determine these characteristics, the physical and chemical properties of the ladle furnace slag and the reclaimed asphalt pavements were analyzed, as well as compatibility with the bitumen emulsion. The aforementioned tests define an optimal combination of RAP (90%), ladle furnace slag (10%), water (2.6%), and emulsion (3.3%), which demonstrated maximum values for compressive strength of the dry and post-immersion bituminous mixture. These tests therefore demonstrate the suitability of ladle furnace slag for cold in-place recycling with bitumen emulsion.