Durability of Construction and Demolition Waste-Bearing Ternary Eco-Cements

In recent years, the development of ternary cements has become a priority research line for obtaining cements with a lower carbon footprint, with the goal to contribute to achieve climate neutrality by 2050. This study compared ordinary Portland cement (OPC) durability to the performance of ternary cements bearing OPC plus 7% of a 2:1 binary blend of either calcareous (Hc) or siliceous (Hs) concrete waste fines and shatterproof glass. Durability was measured further to the existing legislation for testing concrete water absorption, effective porosity, pressurized water absorption and resistance to chlorides and CO2. The experimental findings showed that the 7% blended mortars performed better than the reference cement in terms of total and effective porosity, but they absorbed more pressurized water. They also exhibited lower CO2 resistance, particularly in the calcareous blend, likely due to its higher porosity. Including the binary blend of CDW enhanced chloride resistance with diffusion coefficients of 2.9 × 10−11 m2 s−1 (calcareous fines-glass, 7%Hc-G) and 1.5 × 10−11 m2 s−1 (siliceous fines-glass, 7%Hs-G) compared to the reference cement’s 4.3 × 10−11 m2 s−1. The siliceous fines-glass blend out-performed the calcareous blend in all the durability tests. As the mortars with and without CDW (construction and demolition waste) performed to similar standards overall, the former were deemed viable for the manufacture of future eco-efficient cements.This research was conducted as part of a national project funded by the Spanish Ministry of Science, Innovation and Universities (MICIU), the Spanish National Research Agency (AEI) and the European Regional Development Fund (ERDF), grant number RTI2018-097074-B-C21 and C-22

Behaviour and Properties of Eco-Cement Pastes Elaborated with Recycled Concrete Powder from Construction and Demolition Wastes

This work analyses the influence of fine concrete fractions (<5 mm) of different natures —calcareous (HcG) and siliceous (HsT)—obtained from construction and demolition waste (C&DW) on the behaviour of blended cement pastes with partial replacements between 5 and 10%. The two C&DW fractions were characterised by different instrumental techniques. Subsequently, their limefixing capacity and the physico-mechanical properties of the blended cement pastes were analysed. Lastly, the environmental benefits of reusing these fine wastes in the manufacture of future ecoefficient cement pastes were examined. The results show that HsT and HcG exhibit weak pozzolanic activity, owing to their low reactive silica and alumina content. Despite this, the new cement pastes meet the physical and mechanical requirements of the existing regulations for common cements. It should be highlighted that the blended cement pastes initially showed a coarser pore network, but then they underwent a refinement process between 2 and 28 days, along with a gain in compressive strength, possibly due to the double pozzolanic and filler effect of the wastes. The environmental viability of the blended cements was evaluated in a Life Cycle Assessment (LCA) concluding that the overall environmental impact could be reduced in the same proportion of the replacement rate. This is in line with the Circular Economy goals and the 2030 Agenda for Sustainable Development.This research was funded by the Spanish Ministry of Science, Innovation and Un iversities (MICIU), the Spanish National Research Agency (AEI) and the European Regional Development Fund (ERDF), grant number RTI2018-097074- B-C21-22, as well as by the Spanish Training Program and the European Social Fund (MINECO/FSE) [grant number BES-2016-078454]

Simulation of the Attrition of Recycled Concrete Aggregates during Concrete Mixing

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) and impeller frequency is discussed. Experiments were performed in a laboratory Eirich mixer. Discrete element numerical simulations (DEM) were performed on the same geometry by mimicking the behaviour of the material and, in particular, the cohesion induced by water and the cement paste using either Hertz–Mindlin or Hertz–Mindlin with Johnson–Kendall–Roberts (JKR) contact laws. The combination of the collision energy spectra extracted from the DEM simulations and an attrition model allowed the prediction of the mass loss due to attrition in 1-min experiments. Semi-quantitative agreement was observed between experiments and simulations, with a mean relative error of 26.4%. These showed that higher mass losses resulted from operation at the highest impeller speeds, co-current operation, and also with the wet aggregate. Mixing of the agglomerate in the concrete mix resulted in a significant reduction in attrition when compared to mixing aggregates alone. With further validation, the proposed simulation approach can become a valuable tool in the optimization of mixing by allowing the effects of material, machine and process variables to be studied on the mass loss due to attritionThis research was partially funded by the Brazilian Research Agency CNPq (grant number 310293/2017-0)

ACT-Discover: identifying karyotype heterogeneity in pancreatic cancer evolution using ctDNA

BACKGROUND: Liquid biopsies and the dynamic tracking of somatic mutations within circulating tumour DNA (ctDNA) can provide insight into the dynamics of cancer evolution and the intra-tumour heterogeneity that fuels treatment resistance. However, identifying and tracking dynamic changes in somatic copy number alterations (SCNAs), which have been associated with poor outcome and metastasis, using ctDNA is challenging. Pancreatic adenocarcinoma is a disease which has been considered to harbour early punctuated events in its evolution, leading to an early fitness peak, with minimal further subclonal evolution. METHODS: To interrogate the role of SCNAs in pancreatic adenocarcinoma cancer evolution, we applied whole-exome sequencing of 55 longitudinal cell-free DNA (cfDNA) samples taken from 24 patients (including 8 from whom a patient-derived xenograft (PDX) was derived) with metastatic disease prospectively recruited into a clinical trial. We developed a method, Aneuploidy in Circulating Tumour DNA (ACT-Discover), that leverages haplotype phasing of paired tumour biopsies or PDXs to identify SCNAs in cfDNA with greater sensitivity. RESULTS: SCNAs were observed within 28 of 47 evaluable cfDNA samples. Of these events, 30% could only be identified by harnessing the haplotype-aware approach leveraged in ACT-Discover. The exceptional purity of PDX tumours enabled near-complete phasing of genomic regions in allelic imbalance, highlighting an important auxiliary function of PDXs. Finally, although the classical model of pancreatic cancer evolution emphasises the importance of early, homogenous somatic events as a key requirement for cancer development, ACT-Discover identified substantial heterogeneity of SCNAs, including parallel focal and arm-level events, affecting different parental alleles within individual tumours. Indeed, ongoing acquisition of SCNAs was identified within tumours throughout the disease course, including within an untreated metastatic tumour. CONCLUSIONS: This work demonstrates the power of haplotype phasing to study genomic variation in cfDNA samples and reveals undiscovered intra-tumour heterogeneity with important scientific and clinical implications. Implementation of ACT-Discover could lead to important insights from existing cohorts or underpin future prospective studies seeking to characterise the landscape of tumour evolution through liquid biopsy

Durability of Construction and Demolition Waste-Bearing Ternary Eco-Cements

In recent years, the development of ternary cements has become a priority research line for obtaining cements with a lower carbon footprint, with the goal to contribute to achieve climate neutrality by 2050. This study compared ordinary Portland cement (OPC) durability to the performance of ternary cements bearing OPC plus 7% of a 2:1 binary blend of either calcareous (Hc) or siliceous (Hs) concrete waste fines and shatterproof glass. Durability was measured further to the existing legislation for testing concrete water absorption, effective porosity, pressurized water absorption and resistance to chlorides and CO2. The experimental findings showed that the 7% blended mortars performed better than the reference cement in terms of total and effective porosity, but they absorbed more pressurized water. They also exhibited lower CO2 resistance, particularly in the calcareous blend, likely due to its higher porosity. Including the binary blend of CDW enhanced chloride resistance with diffusion coefficients of 2.9 &times; 10&minus;11 m2 s&minus;1 (calcareous fines-glass, 7%Hc-G) and 1.5 &times; 10&minus;11 m2 s&minus;1 (siliceous fines-glass, 7%Hs-G) compared to the reference cement&rsquo;s 4.3 &times; 10&minus;11 m2 s&minus;1. The siliceous fines-glass blend out-performed the calcareous blend in all the durability tests. As the mortars with and without CDW (construction and demolition waste) performed to similar standards overall, the former were deemed viable for the manufacture of future eco-efficient cements

Optimisation du procédé de malaxage du béton : suivi et contrôle

The concrete mixing corresponds to the stage of the manufacturing process which consists in homogeneously distributing and wetting (structuring) all the components present in the mixer. Parameters influencing the mixing are still relatively uncontrolled while the properties of concrete are strongly related. After a literature review, a database provided by a central ready-mix concrete plant is analyzed to identify the factors affecting the properties of concrete produced industrially. Then, a first experimental study aims to better understand the degradation of the recycled concrete aggregates during the mixing of new concretes, depending on certain parameters such as mixing speed and time, type of agitation, resistance to abrasion of aggregates ... Finally, a second experimental study brings new elements to the understanding of the mixing evolution in function of process parameters (time and speed of mixing, temperature) and formulations (water dosage, dosage and gravel type). In this context, an innovative image analysis technique allowing on-line monitoring of the concrete mixing evolution has been developed. The technique has thus been validated on laboratory scale and on real scale.Le malaxage du béton correspond à l’étape du procédé de fabrication qui consiste à distribuer de façon homogène et à mouiller (structurer) tous les constituants présents dans le malaxeur. Des paramètres qui influencent le malaxage restent de nos jours peu maitrisés, alors que les propriétés du béton en sont fortement liées. Après une étude bibliographique, une base des données fournie par une centrale de béton prêt à l’emploi est analysée pour identifier des facteurs affectant les propriétés du béton produit industriellement. Ensuite, une première étude expérimentale vise à mieux comprendre la dégradation des granulats de béton recyclés lors du malaxage pour produire un nouveau béton, en fonction des certains paramètres comme la vitesse et le temps de malaxage, le type d’agitation, la résistance à l’abrasion du granulat … Enfin, une seconde étude expérimentale apporte des éléments nouveaux pour la compréhension de l’évolution du malaxage en fonction de paramètres process (temps et vitesse de malaxage, température) et de formulations (dosage en eau, dosage et type des gravillons). Dans ce cadre, une technique innovante d’analyse d’images permettant un suivi en ligne de l’évolution du malaxage du béton a été développée. La technique a été ainsi validée à échelle laboratoire et à échelle réelle

Optimization of the concrete mixing process : monitoring and control

Le malaxage du béton correspond à l’étape du procédé de fabrication qui consiste à distribuer de façon homogène et à mouiller (structurer) tous les constituants présents dans le malaxeur. Des paramètres qui influencent le malaxage restent de nos jours peu maitrisés, alors que les propriétés du béton en sont fortement liées. Après une étude bibliographique, une base des données fournie par une centrale de béton prêt à l’emploi est analysée pour identifier des facteurs affectant les propriétés du béton produit industriellement. Ensuite, une première étude expérimentale vise à mieux comprendre la dégradation des granulats de béton recyclés lors du malaxage pour produire un nouveau béton, en fonction des certains paramètres comme la vitesse et le temps de malaxage, le type d’agitation, la résistance à l’abrasion du granulat … Enfin, une seconde étude expérimentale apporte des éléments nouveaux pour la compréhension de l’évolution du malaxage en fonction de paramètres process (temps et vitesse de malaxage, température) et de formulations (dosage en eau, dosage et type des gravillons). Dans ce cadre, une technique innovante d’analyse d’images permettant un suivi en ligne de l’évolution du malaxage du béton a été développée. La technique a été ainsi validée à échelle laboratoire et à échelle réelle.The concrete mixing corresponds to the stage of the manufacturing process which consists in homogeneously distributing and wetting (structuring) all the components present in the mixer. Parameters influencing the mixing are still relatively uncontrolled while the properties of concrete are strongly related. After a literature review, a database provided by a central ready-mix concrete plant is analyzed to identify the factors affecting the properties of concrete produced industrially. Then, a first experimental study aims to better understand the degradation of the recycled concrete aggregates during the mixing of new concretes, depending on certain parameters such as mixing speed and time, type of agitation, resistance to abrasion of aggregates ... Finally, a second experimental study brings new elements to the understanding of the mixing evolution in function of process parameters (time and speed of mixing, temperature) and formulations (water dosage, dosage and gravel type). In this context, an innovative image analysis technique allowing on-line monitoring of the concrete mixing evolution has been developed. The technique has thus been validated on laboratory scale and on real scale

Physical and Mechanical Behavior of New Ternary and Hybrid Eco-Cements Made from Construction and Demolition Waste

Construction and demolition waste (CDW) currently constitutes a waste stream with growing potential use as a secondary raw material in the manufacture of eco-cements that offer smaller carbon footprints and less clinker content than conventional cements. This study analyzes the physical and mechanical properties of two different cement types, ordinary Portland cement (OPC) and calcium sulfoaluminate (CSA) cement, and the synergy between them. These cements are manufactured with different types of CDW (fine fractions of concrete, glass and gypsum) and are intended for new technological applications in the construction sector. This paper addresses the chemical, physical, and mineralogical characterization of the starting materials, as well as the physical (water demand, setting time, soundness, water absorption by capillary action, heat of hydration, and microporosity) and mechanical behavior of the 11 cements selected, including the two reference cements (OPC and commercial CSA). From the analyses obtained, it should be noted that the addition of CDW to the cement matrix does not modify the amount of water by capillarity with respect to OPC cement, except for Labo CSA cement which increases by 15.7%, the calorimetric behavior of the mortars is different depending on the type of ternary and hybrid cement, and the mechanical resistance of the analysed mortars decreases. The results obtained show the favorable behavior of the ternary and hybrid cements made with this CDW. Despite the variations observed in the different types of cement, they all comply with the current standards applicable to commercial cements and open up a new opportunity to improve sustainability in the construction sector

Monitoring of concrete mixing evolution using image analysis

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 method is used to study the evolution of the paste during processing in an intensive laboratory scale mixer for three different formulations: a hard-to-mix concrete, a self-compacting mortar and an easy to mix cement paste. The evolution of the texture allows obtaining important information on the evolution of the different formulations during mixing; in addition, the technique allows identifying with a good repeatability the main characteristic points of the mixture evolution, i.e. the cohesion time and the fluidity time

Recycled concrete aggregate attrition during mixing new concrete

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 initial moisture of the aggregates, mixer geometry, mixing time and mixing speed. To assess the mixing process effect on the recycled concrete aggregate friability, three different aspects were evaluated; the mass loss (mass of fraction inferior to 2.5 mm) the grading and the angularity evolutions with mixing time of an initially 10-14 mm aggregate. Tests were carried out in two types of laboratory concrete mixers, a planetary 30 l mixer from Skako and an intensive 5 l Erich mixer. The results revealed that in normal laboratory setting of the mixers configuration, the mass loss for natural aggregate (NA) is less than 1% of the coarse aggregate. This percentage reach 3% for good quality recycled concrete aggregate (MDE value of 21) and 5% for lower quality recycled concrete aggregate (MDE value of 27). The mass loss directly depends on the mixing parameters and the degradation of the recycled concrete aggregate drastically increased when the mixing speed was raised to 500 RPM. By analyzing the grading evolution during mixing, it was shown that both cleavage (creation of intermediate size particles) and attrition (creation of small particles) mechanisms influenced the aggregate degradation. However, the configuration of mixing significantly influenced the proportion of attrition and cleavage mechanisms. To complete this work, the angularity evolution showed that recycled concrete aggregate surface becomes smoother and the edges more rounded after mixing