Bogdan Cazacliu

Gustave Eiffel University · Department of Materials and Structures (MAST)

The discrete element method (DEM) is used to simulate the behavior of a model sand under cyclic stress. Two approaches are employed in the contact model to account for the effect of anisotropic particle shape: (1) spheres with a rolling resistance moment and (2) clumps of spheres. Model parameters are calibrated using experimental results from drai...

The use of earth as a building material is sustainable and conserves cultural character, reduces energy consumption, is environmentally friendly, and provides a healthy and convenient indoor climate. In this paper, cob like and adobe like specimen were produced in the laboratory and the effects of implementation technique on microstructure of the e...

The objective of this paper was to study the impact of crushing and grinding on the porosity of hardened cement paste, which is responsible for the high values of recycled concrete aggregate (RCA) water absorption. Hardened cement pastes with three different water to cement ratios have been crushed in one to three steps with a jaw crusher to produc...

Discrete element method (DEM) is adopted in this work to characterize the behaviour of Fontainebleau sand NE34 under cyclic stress. For that YADE, an open-source software, is used where a linear contact model is utilized. The effect of anisotropic particle shape is modelled by a rolling resistance moment. The model parameters are first calibrated t...

Each year, the number of scrap tires disposed of in huge piles across the world continuously increases. Consequently, new recycling solutions for these materials have to be proposed. Among them, one possibility consists of shredding tires and mixing the obtained tire chips with sand, which can be used as alternative soils in various geotechnical ap...

Heat transport in rotating processes finds a wide range of application in which academic issues in the fluid mechanics and heat transfer areas are here reported. This paper discusses successive works from the seminal paper of Taylor (1923) to recent numerical results established from a broad range of methods such as DNS, LES, RANS or LB methods. Th...

Recycled Concrete Aggregates (RCA) are mainly composed of two different materials: natural aggregate and attached mortar. Hence, RCA may have a much significant heterogeneity compared to natural aggregates. This heterogeneity limits their reuse in concrete due to the uncertainty in their expected behaviour. To clarify the effect of the attached pas...

Herein, hydrodynamic analysis from a large-eddy simulation in Couette–Taylor–Poiseuille (CTP) geometry is numerically investigated. The present geometry is inspired by a previous experimental work in which heat transport phenomena were investigated in a heat recovery system devoted to a rotary kiln facility. The streamwise and spanwise components o...

Light earth is a natural insulating material composed of earth and vegetal fibres. It can be used to insulate existing and new buildings to reduce energy and resources consumption, and excavated earth generation by the construction sector. A pedological database is crossed with suitability thresholds in order to evaluate spatially the availability...

Recycled concrete aggregates (RCA) incorporate hydrates that can be carbonated. The FastCarb project aims to mineralize CO2 within RCA, improving the quality of these aggregates by the clogging of the porosity and finally decreasing the CO2 impact of concrete in structures. It has two main objectives: to optimize in laboratory conditions the accele...

Rheological analysis of fiber reinforced mortar is a complex subject since fibers induce significant flow disturbances in the paste-fiber system. The aim of this study is to compare the rheological properties of PVA-fiber reinforced mortars determined by two different rheometer probes: vane system and a sphere that is dragged across a fluid (ball m...

The paper presents a comparison of the concentration methods conventional jig, air jig, and sensor-based sorting to treat construction and demolition waste. All tests were made with concrete, brick, and gypsum particles and the tests aim to separate these materials into different size ranges, depending on the method. The equipment tested, conventio...

Mixtures of rigid sand particles and soft rubber particles (rubber chips) are prepared and submitted to vertical taps in a confined cell to investigate their propensity to segregate. The mixture evolution is characterized by means of image analysis of slices obtained by a gelification technique. We show that, in case of equally sized particles, the...

This paper presents a physical characterization for the recycling into new concretes of three comminuted concretes: C16/20 (“ordinary concrete”), C50/60 (“high strength concrete”), and C70/85 (“very high strength concrete”). The top size of the crushed concretes was 19.1 mm and the size range was 4.75 to 19.1 mm. The characterization was carried ou...

Concrete mixing can lead to mechanical degradation of aggregates, particularly when dealing with recycled concrete aggregates. In this work, the attrition of such materials during mixing is studied by means of experiments and simulations. The effect of the presence of fines, water addition, flow configuration of the mixer (co- or counter-current) a...

An accelerated carbonation method was applied to improve the ability of recycled aggregates to store CO2 through the rolling carbonation process; moreover, recycled concrete aggregates’ physicochemical properties to produce secondary aggregates for civil engineering applications were explored and evaluated. The carbonation tests were carried out in...

A literature review comprising 166 publications published over a period of 26 years from 1992 to 2018 is presented in this paper. This review discusses the generation and recycling of con-struction and demolition wastes (CDW) as well as their main uses as raw materials for the con-struction engineering sector. This review pays attention to the use...

This paper proposes pre-beneficiation studies by air jigs of the coal layers from a Moatize coal deposit. Pre-beneficiation, also called destoning, removes tailings before the beneficiation plant. The air jigs operate in the same granulometric size range as the heavy-media cyclones (HMCs) that are installed in the preparation plant. With the deston...

This paper proposes pre-beneficiation studies by air jigs of the coal layers from a Moatize coal deposit. Pre-beneficiation, also called destoning, removes tailings before the beneficiation plant. The air jigs operate in the same granulometric size range as the heavy-media cyclones (HMCs) that are installed in the preparation plant. With the deston...

Accelerated carbonation was employed to improve the physicochemical properties of the recycled sand through CO2 sequestration by a method called rolling carbonation. The carbonation process was fully evaluated by varying some parameters such (i) moisture of the sand, (ii) rotation speed, (iii) recycled sand amount in the reactor, (iv) initial inter...

An inorganic sludge from construction and demolition wastes (ICDW) was grafted with APTES to obtain an inorganic-organic modified adsorbent ICDW-APTES. This adsorbent was successfully employed for ciprofloxacin (CFX) adsorption and treatment of synthetic hospital effluent. The chemical composition of ICDW presented large quantities of SiO2 and Al2O...

Green routes to prepare or manufacture sustainable building materials have been attracting much attention over the years targeting sustainability issues. In this investigation, for the first time, sludge from the inert mineral part of the construction and demolition waste (RA-S) is used as a primary raw material in the fabrication of fired bricks f...

Concrete slurry is an abundant, cheap, and commonly found waste all over the world where construction activities take place; concrete slurry, which is rich in calcium and metallic oxides, could be successfully employed in the phosphate (P) removal from aqueous media. For the first time, the effect of the carbonation process on concrete adsorbent pr...

Large quantities of construction and demolition waste is generated annually around the world. Part of this material is processed in recycling plants. After removing metals, fines and lights, the construction and demolition waste is crushed and sized and can be used as aggregates for low resistance concrete, for road sub-base, city landfill and othe...

Large quantities of construction and demolition waste is generated annually around the world. Part of this material is processed in recycling plants. After removing metals, fines and lights, the construction and demolition waste is crushed and sized and can be used as aggregates for low resistance concrete, for road sub-base, city landfill and othe...

This study aimed to investigate phosphate removal from aqueous effluents by an inorganic sludge from the inert part of construction and demolition wastes (CSW) as adsorbent. It is also discussed the application of the loaded P adsorbent as potential fertiliser. The CSW was also thermally treated at 800 °C for 2 h (CSW-T), and its influence in the P...

The production of recycled aggregates requires thorough quality control. Sampling procedures already exist to ensure the representativeness of natural aggregates. However, given the heterogeneity of recycled aggregates, new sampling procedures have to be developed. The first step is the homogenization of the field sample which must then be reduced...

Green routes to prepare or manufacture sustainable building materials have been attracting a lot of attention over the years targeting sustainability issues. In this investigation, for the first time, sludge from the inert mineral part of the construction and demolition waste (RA-S) is used as main raw material in the fabrication of fired bricks fo...

Mixing is one of the mortar processing steps (the others being proportioning, transport and application) that, due to its apparent operational simplicity, has been somewhat undermined. However, the mixing process quality has direct influence on the mortar’s rheological behavior and its hardened state properties. In this context, this study’s object...

Past builders have developed very low-embodied energy construction techniques optimizing the use of local building materials. These techniques are a source of inspiration for modern sustainable building. Unfortunately, this know-how was orally transmitted and was lost as earth construction fell into disuse during the 20th century in European countr...

In this work, an accelerated carbonation method called “rotating carbonation” is applied to improve the physical chemical properties of recycled aggregates aiming to produce secondary aggregates for civil engineering applications; moreover, the ability of such aggregates in storing CO2 through the rotating carbonation is explored and evaluated. The...

The stockpiling of waste tires at landfill sites has become a nuisance for the society. One of the alternatives could be converting the recycled rubber into powdered form and mixing it with soil to use it as the backfill of the retaining structures. This paper is based on the study of such sand-rubber mixtures. In this work, Discrete Element (DEM)...

The volume of scrap tyres, an undesired urban waste, is increasing rapidly in every country. Mixing sand and rubber particles as a lightweight backfill is one of the possible alternatives to avoid stockpiling them in the environment. This paper presents a minimal model aiming to shed light on the relevant physical parameters governing the evolution...

Pavement material production requires a highly intensive energy processing related to the drying and the heating of granular materials within a rotary kiln. Thus, a better prediction of thermophysical parameters of bituminous concrete materials during their transformation is required to improve the processes in order to reduce their environmental i...

Particle size variation plays a key role in jigging performance, and despite extensive research in the area, very little attention has been given in the case of pneumatic jigging. The aim of this study was to look into particle stratification in a pilot-scale pneumatic jig when varying the particle size and the range of the particle size distributi...

Recycled concrete aggregates (RCA) are composed of two different materials: natural aggregate and attached cement paste. It is generally admitted that finer the RCA greater is the quantity of adhered cement paste. In this study it is shown that for a given granular class, very large disparities may be present in the adhered cement paste content, wh...

A new methodology based on the cross-referencing of spatialized pedological and heritage data is proposed to identify and quantify soil resources available for earth construction. The paper underlines the pedological particularities of areas containing earth heritage and uses these particularities to propose criteria to assess the suitability of so...

A new image analysis technique coupled with the power consumption were employed in this paper and proved to be a relevant method to detect the different characteristic times of the mixing evolution, i.e. the cohesion time, the fluidity time and the half-life time of the mixture evolution after fluidity. It was shown that the “effective water-to-pow...

New hybrid materials using kaolin and the organosilicas methyl-polysiloxane (MK), methyl-phenyl-polysiloxane (H44), tetraethyl-ortho-silicate (TEOS) and 3-amino- propyl-triethoxysilane (APTES) were obtained by sol-gel process. These materials presented specific surfaces areas (S BET ) in the range of 20-530 m2 g -1 . Scanning electron microscopy (S...

The present paper deals with experimental measurements performed within a heat exchanger devoted to the thermal rotating machineries. The device is based on a rotor-stator system scaled from an industrial rotary kiln. The thermal recovery system is able to capture the heat losses while the kiln wall is cooled. The inner moving wall-to-air heat exch...

Initial moisture and pre-wetting method influence on the water absorption of recycled concrete aggregates (RCA) have been studied experimentally. For this purpose, RCA were pre-wetted by three methods: soaking under partial vacuum (simulating long term wetting), soaking under atmospheric pressure, and spraying (simulating short term wetting). The r...

Poor estimation of the water absorption coefficient (WA) of recycled concrete aggregates (RCA) engenders inadequate effective water for the recycled aggregate concrete (RAC), leading to poor mechanical properties or poor workability. Pre-saturation of RCA before mixing could appear as a potential technical solution. However, pre-saturation before m...

The proposition of this paper is to introduce a sorting platform aiming to increase quality on recycled aggregates by supplementary use of mineral processing techniques and more sorting. The difficulty of liberation is discussed and the methodology currently used in mineral processing is proposed. Jigs, hydrocyclones and sensor-based sorting are eq...

The volume of scrap tyres, an undesired urban waste, is increasing rapidly in every country. Mixing sand and rubber particles as a lightweight backfill is one of the possible alternatives to avoid stockpiling them in the environment. This paper presents a minimal model aiming to capture the evolution of the void ratio of sand-rubber mixtures underg...

The use of air jigging for performing multi-component separation in the treatment of mixed construction and demolition waste was studied. Sorting tests were carried out with mixtures of equal bulk volume of concrete and brick in which fixed quantities of unwanted materials - gypsum, wood and paper - were added. Experimental results have demonstrate...

The improvement of inline mixer measurements is imposed in a growing concrete industry employing increasingly complex manufacturing processes. In this work we discuss an inline image analysis technique applied to the monitoring of concrete mixing, which is based on the evolution of the texture of pictures taken at the surface of the mixing bed. The...

The complexity of the Life Cycle Assessment (LCA) method requires many subjective choices throughout the procedure, which make decision making difficult and LCA results insecure. Our approach consists in combining life cycle thinking and sensitivity analysis to provide information to the actor of a foreground system within a product's life cycle. F...

This paper proposes an economic analysis of three different types of processing in CDW (construction and demolition waste) recycling platforms, according to the sophistication of the processing technologies (current advanced, advanced and advanced sorting). The methodology that is adopted is in the economic evaluation concept of projects and is cla...

Rammed earth was traditionally used in western European countries before industrial building materials replace it during 20th Century. Construction strategies developed by former builders were dictated by locally available construction materials and engendered local constructive cultures. Unfortunately, this knowledge was orally transmitted and is...

In this paper, we compare different methods for determining the water absorption of recycled aggregates (RAs) and, highlighting advantages and critical points, attempt to suggest alternatives for a better way to measure it. Water absorption (WA) capacity has two purposes: (a) measuring the interconnected porosity, which is useful for mechanical con...

In this work, the recycled concrete aggregate (RCA) friability during mixing was studied in order to better understand the evolution of this material during the mixing process and improve the recycled aggregate concrete mix-design. The influence of some important materials and process parameters was evaluated: initial abrasion resistance and initia...

The will of reducing environmental and social impact of building industry has led to a renewed interest in earth construction. Most of earth construction literature dealt with rammed earth or adobe techniques, but very little with cob. Yet, cob participates in the diversity of vernacular earth construction processes that value local materials and i...

This work deals with the characterization of fragmentation of recycled concrete aggregate (RCA) by the Los Angeles test. The standard testing procedure for the Los Angeles index requires the measurement of the mass passing 1.6 mm after 500 revolutions of the drum. Questions arise on the significance of this measure for RCA as the resistances of the...

This study investigates the influence of wall effects on particle separation in an air jigging device. Tests were conducted with a ternary mixture of concrete, brick and gypsum particles in the size range from 12 to 20 mm for three different jigging times. It is shown that an unusual, remarkable segregation occurred in the direction perpendicular t...

Time effects on granular soils have been observed in the laboratory and by in-situ tests, but these cannot be reproduced by classical elasto-plastic models. To address these concerns, existing specific modelling approaches were based on the theory of viscoplasticity formulated by Perzyna or on a viscous evanescent relationship. This work explores a...

The goal of this article is to provide some essential results for the solution of a regularized viscoplastic frictional flow model adapted from the extensive mathematical analysis of the Bingham model. The Bingham model is a standard for the description of viscoplastic flows and it is widely used in many application areas. However, wet granular vis...

The purpose of this paper is to propose a sorting platform to increase the quality of recycled aggregates through the supplementary use of mineral processing techniques and additional sorting. The difficulty of liberation is discussed, and the methodology currently used in mineral processing is proposed. Jigs, hydrocyclones and sensor-based sorting...

Abstract Heating is the dominant energy load in the french construction sector for both residential and commercial buildings. Many researches were made on hemp based insulation products as hemp-lime is a renewable and bio based resource. Moreover, it exhibits interesting ability in inner air moisture control. However, the physical properties of thi...

The aim of this article is to develop a methodological approach allowing to assess the influence of parameters of one or more elementary processes in the foreground system, on the outcomes of a life cycle assessment (LCA) study. From this perspective, the method must be able to: (1) include foreground process modeling in order to avoid the assumpti...

The advancement on the physical heat transfer model in granular system is crucial for the energy process efficiency development such as flights rotary kiln encountered in many industrial areas. The present paper is devoted to a coupled thermal-granular model development applied to that process. Based on the exchange surfaces estimation governing th...

The proposition of this paper is to propose a sorting platform aiming to increase quality on recycled aggregates by supplementary use of mineral processing techniques and more sorting. The difficulty of liberation is discussed and the methodology currently used in mineral processing is proposed. Jigs, hydrocyclones and sensor-based sorting are equi...

Advection-dispersive phenomena inside two geometries of porous media, corresponding to a structured and unstructured network of minichannels, are studied from a combination of analytical, numerical and electrodiffusion (ED) techniques. The instantaneous limiting diffusion current, connected to the concentration of electro-active species flowing in...

The recycling of inert construction and demolition materials (C&D) remains problematic if these materials are used to process high-quality recycled aggregates suitable for manufacturing new concrete. Even when selective demolition is employed, the crushing and classification of C&D produces recycled aggregates with an unacceptable level of impuriti...

In many industries where the manufacturing process involves casting of a fluid or a suspension, it is essential to have tools predicting the flow and the possible subsequent hardening process for mould design and process planning. Trial and error may be applied to optimize the casting process when a large number of small samples are produced. Howev...