Modelización numérica en 3D de materiales reciclados en frío in situ con emulsión bituminosa en carreteras de bajo tráfico de la República Sudafricana

Esta XII Jornada tuvo lugar en Madrid, el 30 y 31 de mayo de 2017.[Resumen:] En esta comunicación se hace una modelización numérica de secciones de firme recicladas “in situ” con emulsión asfáltica. Se analizan firmes constituidos por un 25 % de material bituminoso fresado (Reclaimed Asphalt Pavement, RAP) y un 75 % de áridos naturales (capa granular), tanto con un 1 % de cemento como sin él. Se modeliza el comportamiento resiliente y permanente de estos materiales. Se calculan las respuestas del firme bajo una carga de ruedas gemelas, con cuatro tipos de explanadas de diversas características. Se obtiene la ley de variación del módulo resiliente para las cuatro explanadas y para los dos materiales reciclados (con cemento y sin cemento). Se analiza finalmente la deformación permanente de estos materiales reciclados

Compactability and mechanical properties of cold recycled mixes prepared with different nominal maximum sizes of RAP

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG[Abstract:] The use of cold recycled asphalt mixtures (CRM) has been soaring during recent years. Reclaimed Asphalt Pavement (RAP) is the main component of CRM, and despite the numerous studies on CRM, the impact of different RAP types has not been deeply studied. This study compares the volumetric and several mechanical properties of CRM prepared with RAP from two different sources and with various nominal maximum sizes (NMS). The mix design was fixed, and specimens were prepared using gyratory and impact compactors. Densities were measured before and after accelerated curing. Stiffness of CRM was investigated with Indirect Tensile Stiffness Modulus, tension–compression, and dynamic tests. Additionally, the cracking behavior was evaluated with Indirect Tensile Strength and Semi-Circular Bending tests. The particle size distribution was a key factor in the compactability of the CRMs studied. Together with temperature, the most influential factor on the studied mechanical properties was the air void content, while the differences in NMS showed no clear trends.Ministerio de Ciencia e Innovación; BIA2016-80317-RMinisterio de Ciencia e Innovación; BES-2017-07963

Influence of ageing on the properties of bitumen from asphalt mixtures with recycled concrete aggregates

The reuse of recycled concrete aggregates in new hot-mix asphalt can be a more sustainable method of production, but these mixtures may need a heat treatment before compaction to improve their water sensitivity performance. A direct consequence of this treatment is an increase in the hot-mix asphalt resilient modulus. The aim of this paper is to analyse the effect of ageing on the stiffness of asphalt mixtures with different amounts of recycled concrete aggregates, before and after a heat treatment, which was analysed through the assessment of its bitumen properties. Moreover, this paper also aims to analyse whether the rolling thin-film oven test is able to simulate the ageing effect of the heat treatment. In the laboratory work, a paving grade bitumen B50/70 has been used to produce asphalt mixtures with 0% and 30% recycled concrete aggregates, and the bitumen was later characterised (using penetration, softening point, dynamic viscosity and dynamic shear rheometer tests) in various situations, such as when using virgin bitumen, short-term aged bitumen, aged bitumen after heat treatment (simulated with 4 h of rolling thin-film oven test) and bitumen samples recovered from asphalt mixtures with different production mixes (0% and 30% recycled concrete aggregate) and heat treatment conditions (0 and 4 h of curing time in the oven). Based on the results obtained, it could be concluded that the ageing resulting from the heat treatment is the primary cause of the hot-mix asphalt's increased stiffness, while recycled concrete aggregate content has a small influence. Moreover, it could be concluded that when there is no curing time, the recycled concrete aggregate protects the bitumen against ageing. Additionally, it could be stated that the rolling thin-film test is able to adequately simulate the ageing effect of the heat treatment. Thus, this test is useful for determining the ageing suffered by the bitumen when the recycled concrete aggregate mixture is manufactured using a heat treatment.The authors would like to acknowledge the Spanish Ministry of Education and Science for sponsoring this research through Project BIA2010-17751

Improving the Sustainability of Semi-Dense Asphalt Pavements by Replacement of Recycled Concrete Aggregate Fractions

Waste concrete is one of the most highly produced types of waste in the urban environment and finding a means for its re-use is crucial to making infrastructure sustainable. Semi-Dense Asphalt (SDA) is a type of asphalt mixture, which is commonly used in Switzerland to reduce pavement noise. This study examined the use of various fractions of Recycled Concrete Aggregates (RCA) into SDA mixtures. The virgin aggregates were replaced by RCA in selected fractions of 2/4 and 0.125/2 at 100% and 50%, with only one fraction being replaced for any single mixture. The mixtures were evaluated by volumetrics, indirect tensile strength and water sensitivity (EN 12697-12) in order to assess the effects of each RCA fraction. The results showed that RCA coarse aggregates absorb high amounts of binder, which is not the case for the RCA sand. The ITS results showed increase peak load for the RCA replacement samples but also increased brittleness. The ITSR% was similar to the control for lower fraction of RCA replacement samples, but significantly lower with higher replacement

Use of lignin biopolymer from industrial waste as bitumen extender for asphalt mixtures

Liquid waste containing lignin, a biopolymer of vegetable origin, is generated from the production of wood hardboards. Because polymers improve the performance of asphalt mixtures, this work studies the possibility of using this industrial waste as a bitumen extender in the production of asphalt mixtures. Thus, asphalt mixtures with 0% (control), 5%, 10%, 20%, and 40% of industrial waste were produced. The bitumen–aggregate adhesion, moisture damage resistance, resilient modulus, permanent deformation resistance, and thermal susceptibility of such mixtures were analysed. Asphalt mixtures with 20% of industrial waste showed the best moisture damage resistance. As the percentage of industrial waste increased, the thermal susceptibility of the mixture also increased. In this regard, at 5 °C, the resilient modulus of the mixture made with 20% of industrial waste was 19.08% lower than that of the control mixture. Moreover, at 30 °C, the resilient modulus of the mixture made with 20% of industrial waste was 10.48% higher than that of the control mixture. Therefore, it can be stated that it is appropriate to use this industrial waste containing lignin as a bitumen extender. It can be used in asphalt mixtures for road pavement, mainly by substituting 20% of the bitumen by this liquid waste. It reduces the consumption of bitumen and improves the performance of asphalt mixtures, contributing to the purpose of sustainable construction. The industrial waste was not subjected to any transformation process, thus facilitating its use. The reduction in the use of bitumen in asphalt mixtures by adding this industrial waste contributes to the goals of sustainable development and cleaner production of asphalt mixtures