Passing ability of fresh concrete : A probabilistic approach

In the present paper, it is first reminded that the probability of granular blocking of a suspension crossing a flow contraction increases with the number of particles crossing the obstacles, their volume fraction and the ratio between the diameter of the particles and the contraction gap. It is moreover reminded that this phenomenon can be described using a simple dimensionless geometric parameter as this phenomenon only slightly depends on the rheology of the suspending fluid. An adaptation of this dimensionless parameter to the specific case of concrete is proposed and compared to experimental results. Finally, an application to the prediction of the passing ability of Ordinary Rheology Concrete (ORC) and Self Compacting Concrete (SCC) is proposed and compared to the European technical recommendations

Increasing the Use of Reclaimed Asphalt in Italy towards a Circular Economy: A Top-Down Approach

This contribution concerns recommendations which could be made to Italian regulatory bodies to improve their use of reclaimed asphalt (RA) in the road engineering sector. It is essential for the use of RA to be established as a standard practice since it has been proven that it can serve as an end-of-waste product that complies with the principles of a circular economy within both an open- and a closed-loop approach [1,2]. Several aspects will be covered, starting with an analysis of European nations whose economies can be classed as “more circular” compared to Italy’s. This refers to nations which have a high usage of RA. Furthermore, nations which have clear regulatory guidelines on the use of RA in road construction or, alternatively, nations which have very lax statutory requirements on pavement design allowing best practice to reign could be considered as more circular if these regulations or permissiveness result in a greater uptake in the use of RA in road construction

From Buildings' End of Life to Aggregate Recycling under a Circular Economic Perspective: A Comparative Life Cycle Assessment Case Study

The demolition of buildings, apart from being energy intensive and disruptive, inevitably produces construction and demolition waste (C&Dw). Unfortunately, even today, the majority of this waste ends up underexploited and not considered as valuable resources to be re-circulated into a closed/open loop process under the umbrella of circular economy (CE). Considering the amount of virgin aggregates needed in civil engineering applications, C&Dw can act as sustainable catalyst towards the preservation of natural resources and the shift towards a CE. This study completes current research by presenting a life cycle inventory compilation and life cycle assessment case study of two buildings in France. The quantification of the end-of-life environmental impacts of the two buildings and subsequently the environmental impacts of recycled aggregates production from C&Dw was realized using the framework of life cycle assessment (LCA). The results indicate that the transport of waste, its treatment, and especially asbestos' treatment are the most impactful phases. For example, in the case study of the first building, transport and treatment of waste reached 35% of the total impact for global warming. Careful, proactive, and strategic treatment, geolocation, and transport planning is recommended for the involved stakeholders and decision makers in order to ensure minimal sustainability implications during the implementation of CE approaches for C&Dw

Examining the critical factors that influence the success of construction and demolition waste reverse logistics operations

The reverse logistics (RL) performance of construction and demolition waste (C&DW) differs significantly between countries. Although some countries are successfully circular, other countries are still far behind; with C&DW being largely directed to landfills or being illegally dumped. There is a lack of guidelines on the requirements for transitioning countries towards C&DW diversion, and little attention has been given to the factors that influence the success of C&DW RL and increased circularity. This study aims to develop a framework that helps in structuring and assessing the success of C&DW RL on a regional level and serves as a guide for transitioning developing countries towards implementing such operations. Since the framework should help evaluate where interventions are needed to enhance performance, the exact domains to be used and their priorities should be identified. A systematic litera- ture review was conducted to identify the critical factors that affect the outcome of RL operations. After their identification, the interrelationships between the factors and the dependence and driving power of each are examined through interpretive structural modelling. This analysis provides valuable insights and thus, allows for the establishment of a hierarchy of factors that can serve as a guide for decision-makers. The developed framework can be utilized for enhancing the efficiency of current RL operations as well as for identifying the direction of action and efforts needed to shift developing countries towards the implementation of circular economy in the sector of C&DW

STATE OF PRACTICE IN THE C&DW SECTOR WHILE PURSUING CIRCULAR ECONOMY: THE ITALIAN RECYCLED MATERIALS MARKET IN ROAD ENGINEERING

Construction and demolition waste (C&DW) is mainly produced during the construction, demolition, or renovation activities of engineering structures and it accounts for a remarkable amount of the total C&DW generated, as it is estimated to be around 30%. This proportion differs across countries belonging to different types of economies and tends to be greater in countries with developing economies reaching 74% of total annual production. There is a plethora of applications that C&DW can be used for under a circular economic model and in this research study a focus is being given in the utilization of C&DW within the pavement engineering sector, and more specifically, in the utilization of said waste in road earthworks. Circular Economy can act as a steppingstone towards the uptake of C&DW recycling and exploitation. To understand the state of practice, a market and an implementation analysis have been conducted in Italy. The current applications of C&DW recycling into road projects were analyzed along with the existing regulations, and local producers. The results projected the various challenges faced by the involved stakeholders, along with the barriers that hinder the wide recycling of C&DW in road engineering projects. Finally, the proposed national action plans are analyzed and the future potential use of C&DW is put into context. The future of the specific research is going to involve a full scale, on-site implementation of C&DW in a defined road segment

How to monitor the modulus of elasticity of concrete, automatically since the earliest age ?

Monitoring the evolution of an early age set of parameters on concrete is necessary to predict the early age behaviour of structures. The difficulty lies in the fact that this monitoring must be automatic because the concrete hardening process takes place over a long period after the casting. This paper presents a new methodology and an apparatus, specifically designed at IFSTTAR, to monitor the hardening process of a concrete. Mainly, the Young's modulus can be monitored in compression. Measurements start soon after having cast the concrete and the sample temperature is completely controlled so that the concrete maturity is well mastered. The performances of this apparatus, obtained on an ordinary concrete, are compared to more classical measurements using an extensometer mounted on the sample just after the setting time and to ultrasonic measurements. In these cases, the temperatures were not controlled and results have to be expressed in equivalent time. A comparison with another method developed and used at ULB by using the same concrete, in the frame of a joined cooperation between our two laboratories is achieved. This test set up is based on the so called Temperature Stress Testing Machine (TSTM). This device has been specifically designed with a control of the concrete maturity by the use of a dummy specimen only submitted to free deformations (thermal, shrinkage). The TSTM allows compressive and tensile testing starting just after the setting time. In addition, concrete properties, such as compressive and tensile strength, have been characterized at early age. These values have been used for the design of the loading histories applied in the automatic tests. The heat released by the cement hydration has also been measured in order to express the results on a maturity scale. © 2013 RILEM.SCOPUS: ar.jinfo:eu-repo/semantics/publishe