Influencia de estériles de carbón activados térmicamente en la fabricación de cementos de bajo contenido en clinker: durabilidad frente a agentes agresivos

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Geología y Geoquímica. Fecha de lectura: 21-04-2020Esta tesis tiene embargado el acceso al texto completo hasta el 21-10-202

Progress in the influence of recycled construction and demolition mineral-based blends on the physical–mechanical behaviour of ternary cementitious matrices

The serious technical and environmental problems associated with the management of construction and demolition wastes (CDW) have led to a worldwide growing interest in the recycling of that waste stream as secondary raw material for sustainable building applications. This research work investigates the physical and mechanical behaviour of mortars made with ternary cements containing 7% of a binary recycled CDW mixture comprising the fine fraction (<5 mm) of recycled concrete waste (both siliceous and calcareous nature) in combination with recycled laminar glass in three different proportions (1/1, 1/2, and 2/1, respectively). To this end, the chemical composition and fineness of the anhydrous ternary cements were analysed, as well as their behaviour in paste and mortar matrices, in both fresh and hardened states, verifying the requirements established by the applicable standards. The results attest to the viability of using these ternary cements, as their performance is comparable to that of an ordinary Portland cement (OPC), without evidencing any significant dependence on the glass content. The compressive strength values decrease by 7–8% with respect to that of the OPC mortar, revealing the prevalence of the filler effect over the pozzolanic reaction. The ternary cements analysed in this study met the chemical, physical and mechanical requirements for the elaboration of future eco-efficient cements.This research was 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-C21-22. The authors are also grateful for the support received from the Spanish Construction and Demolition Waste Recycling Association (RCDA), the Spanish Institute of Cement and its Applications (IECA) and Sika (Madrid, Spain). We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI)

Progress in the influence of recycled construction and demolition mineral-based blends on the physical–mechanical behaviour of ternary cementitious matrices

[Abstract:] The serious technical and environmental problems associated with the management of construction and demolition wastes (CDW) have led to a worldwide growing interest in the recycling of that waste stream as secondary raw material for sustainable building applications. This research work investigates the physical and mechanical behaviour of mortars made with ternary cements containing 7% of a binary recycled CDW mixture comprising the fine fraction (<5 mm) of recycled concrete waste (both siliceous and calcareous nature) in combination with recycled laminar glass in three different proportions (1/1, 1/2, and 2/1, respectively). To this end, the chemical composition and fineness of the anhydrous ternary cements were analysed, as well as their behaviour in paste and mortar matrices, in both fresh and hardened states, verifying the requirements established by the applicable standards. The results attest to the viability of using these ternary cements, as their performance is comparable to that of an ordinary Portland cement (OPC), without evidencing any significant dependence on the glass content. The compressive strength values decrease by 7–8% with respect to that of the OPC mortar, revealing the prevalence of the filler effect over the pozzolanic reaction. The ternary cements analysed in this study met the chemical, physical and mechanical requirements for the elaboration of future eco-efficient cements.Ministerio de Ciencia, Innovación y Universidades; RTI2018-097074-B-C21-2

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]

Durability of Eco-Efficient Binary Cement Mortars Based on Ichu Ash: Effect on Carbonation and Chloride Resistance

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG[Abstract] This research work focuses on the performance of mortars containing ichu ash as a potential environmentally-sound alternative to traditional pozzolans (at 6% and 10% replacement levels) under CO2 and chloride ion rich environments, in order to evaluate the capacity of this material to produce more sustainable and durable blended cements. The results indicate that ichu ash increases the susceptibility to carbonation, although mortars with 6% ichu ash content behave similarly to OPC ones. However, both density and mechanical strength improve after 250 days of carbonation for both ichu-blended mortars. In terms of resistance to chloride penetration, the addition of ichu ash contributes to retaining the ions in the superficial layers of the mortars, inhibiting their advance. It was found that formulations with both 6% and 10% ichu ash content produced a reduction in the chloride diffusion coefficient of approximately 60%. This phenomenon was mainly attributed to the refinement and increased complexity of the microstructure of the mortars due to the pozzolanic effect. Therefore, it was found that in certain types of environments, ichu ash can be an interesting tool to improve the durability of cements while reducing their environmental footprint and exploiting local resources.This research work was carried out thanks to the Framework Partnership Agreement between CSIC (Spain) and UTEC (Peru) [ref. n. ACAM 2021040044 BDC and 20215065] and the economic support of FONDECYT [contract n. 103-2018-FONDECYT –BM]. L. C-M. gratefully acknowledges the funding received by the Spanish Training Programme and the European Social Fund (MINECO/ESF) [grant number BES-2016-078454]. Funding for open access charge: Universidade da CoruñaPerú. Consejo Nacional de Ciencia, Tecnología e Innovación Tecnológica (CONCYTEC); 103-2018-FONDECYT–B

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

Water exchange rates and mechanisms in tetrahedral [Be(H2O)4]2+ and [Li(H2O)4]+ complexes using DFT methods and cluster‐continuum models

[Abstract] The water exchange reactions in aquated Li+ and Be2+ ions were investigated with density functional theory calculations performed using the [Li(H2O)4]+·14H2O and [Be(H2O)4]2+·8H2O systems and a cluster‐continuum approach. A range of commonly used functionals predict water exchange rates several orders of magnitude lower than the experimental ones. This effect is attributed to the overstabilization of coordination number four by these functionals with respect to the five‐coordinated transition states responsible for the associative (A) or associative interchange (Ia) water exchange mechanisms. However, the M06 and M062X functionals provide results in good agreement with the experimental data: M062X/TZVP calculations yield a concerted Iamechanism for the water exchange in [Be(H2O)4]2+·8H2O that gives an average residence time of water molecules in the first coordination sphere of 260 μs. For [Li(H2O)4]+·14H2O the water exchange reaction is predicted to follow an A mechanism with a residence time of inner‐sphere water molecules of 25 ps.Ministerio de Economía y Competitividad; CTQ2013‐43243‐PMinisterio de Economía y Competitividad; CTQ2015‐71211‐RED

Meta-GWAS identifies the heritability of acute radiation-induced toxicities in head and neck cancer

Background and purpose: We aimed to the genetic components and susceptibility variants associated with acute radiation-induced toxicities (RITs) in patients with head and neck cancer (HNC). Materials and methods: We performed the largest meta-GWAS of seven European cohorts (n = 4,042). Patients were scored weekly during radiotherapy for acute RITs including dysphagia, mucositis, and xerostomia. We analyzed the effect of variants on the average burden (measured as area under curve, AUC) per each RIT, and standardized total average acute toxicity (STATacute) score using a multivariate linear regression. We tested suggestive variants (p < 1.0x10-5) in discovery set (three cohorts; n = 2,640) in a replication set (four cohorts; n = 1,402). We meta-analysed all cohorts to calculate RITs specific SNP-based heritability, and effect of polygenic risk scores (PRSs), and genetic correlations among RITS. Results: From 393 suggestive SNPs identified in discovery set; 37 were nominally significant (preplication < 0.05) in replication set, but none reached genome-wide significance (pcombined < 5 × 10-8). In-silico functional analyses identified “3′-5'-exoribonuclease activity” (FDR = 1.6e-10) for dysphagia, “inositol phosphate-mediated signalling” for mucositis (FDR = 2.20e-09), and “drug catabolic process” for STATacute (FDR = 3.57e-12) as the most enriched pathways by the RIT specific suggestive genes. The SNP-based heritability (±standard error) was 29 ± 0.08 % for dysphagia, 9 ± 0.12 % (mucositis) and 27 ± 0.09 % (STATacute). Positive genetic correlation was rg = 0.65 (p = 0.048) between dysphagia and STATacute. PRSs explained limited variation of dysphagia (3 %), mucositis (2.5 %), and STATacute (0.4 %). Conclusion: In HNC patients, acute RITs are modestly heritable, sharing 10 % genetic susceptibility, when PRS explains < 3 % of their variance. We identified numerus suggestive SNPs, which remain to be replicated in larger studies

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 (&lt;5 mm) of different natures —calcareous (HcG) and siliceous (HsT)—obtained from construction and demolition waste (C&amp;DW) on the behaviour of blended cement pastes with partial replacements between 5 and 10%. The two C&amp;DW fractions were characterised by different instrumental techniques. Subsequently, their lime-fixing 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 eco-efficient 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

Raman spectroscopy and SERS methodology for the analysis of a melamine admixture superplasticizer for concrete.

XXVII National Spectroscopy Meeting / XI Iberian Spectroscopy Conference, Málaga from 5 to 8 of July 2022. -- Conferencia invitadaAdmixtures used in concrete are natural or artificial compounds which are added in the kneading water to improve some properties of the fresh and the hardened concrete, such as durability, workability, mechanical strength, etc. Admixtures are classified according to modified properties and are defined as plasticizers, air entrainers, accelerators, retarders or superplasticizers and are added in concentrations below 1%. Due to the low concentration of admixtures it is difficult to monitor them after the interaction with the cement particles. This work is focused on a methodology to study a superplasticizer admixture based in polymerized melamine with Raman Spectroscopy and Surface Enhanced Raman Spectroscopy (SERS). The admixture is commercialized as a transparent liquid of high density where the polymerized melamine is dissolved. A drop of admixture has been heated at 40ºC degrees during four hours to evaporate the solvent; the quantity of the solid in the commercial admixture has been calculated at 21% in mass. The polymerized melamine has been analyzed with Raman spectroscopy before and after a heating treatment at 40ºC, thereby Raman spectrums of the admixture have been obtained as liquid and as solid. Besides, a SERS study of the same molecule has been done analyzing the commercial liquid admixture, and the solid left after the heating treatment by diluting the polymerized melamine in distilled water at 21% in mass. Results indicate that the polymerized melamine is not degraded during heating treatment, besides, Raman spectrum show signals which below to the aromatic ring at the melamine and other signals which correspond to the polymer. It has been tested that SERS technique is viable for the analysis of polymerized melamine as superplasticizer admixtures in the experimental conditions considered, being possible to identify characteristic signals of the aromatic ring of the melamine at 922 and 1030 cm-1.This study was funded by the Regional Government of Madrid, (S2018/NMT-4372 TOP Heritage-CM Programme) and by the Spanish Ministry of Science, Innovation and Universities (MICIU), the Spanish National Research Agency (AEI) and the European Regional Development Fund (ERDF) under project RTI2018-097074-B-C21-22. The authors wish to acknowledge the professional support of the Plataforma Temática Interdisciplinar del CSIC Patrimonio Abierto: Investigación y Sociedad (PTI-PAIS)