Influence of Accelerators on Cement Mortars Using Fluid Catalytic Cracking Catalyst Residue (FCC): Enhanced Mechanical Properties at Early Curing Ages.

Supplementary cementitious materials (SCMs) have been used in the construction industry to mainly reduce the greenhouse gas emissions associated with Portland cement. Of SCMs, the petrochemical industry waste known as fluid catalytic cracking catalyst residue (FCC) is recognized for its high reactivity. Nevertheless, the binders produced using SCMs usually present low mechanical strength at early curing ages. This study aims to assess the effect of different accelerating additives (KOH, sodium silicate SIL, commercial additive SKR) on the mechanical strength of mortars containing FCC. The results show that after only 8 curing hours, the compressive strength gain of the FCC mortars containing SKR was over 100% compared to the FCC mortar with no additive (26.0 vs. 12.8 MPa). Comparing the compressive strength of FCC mortar containing SKR to the control mortar, the enhancement is spetacular (6.85 vs. 26.03 MPa). The effectiveness of the tested accelerators at 8-24 curing hours was KOH ≈ SIL < SKR, whereas it was KOH < SIL < SKR for 48 h-28 days. The thermogravimetric data confirmed the good compatibility of FCC and the commercial accelerator.

Study of the Pozzolanic Reactivity of Sugar Cane Straw Ashes (SCSA) Burned under Controlled Conditions.

The aims of this work were to evaluate the reactivity of sugarcane straw ashes (SCSA) burned under controlled conditions and to analyze their reactivity in blended cement and hydrated lime pastes by thermogravimetric analysis (TG) and calorimetry. Four different ashes were produced, and burned at 600 °C, 700 °C, 800 °C and 900 °C (SCSA600, SCSA700, SCSA800 and SCSA900, respectively). These ashes were characterized by X-ray fluorescence spectroscopy, X-ray diffractometry, particle size distribution by laser diffraction and specific area surfaces to assess their potential interest in the partial replacement of inorganic binders (Portland cement (OPC) and hydrated lime). The hydrated lime pastes were subjected to scanning electron microscopy (SEM) and TG. The blended cement pastes were analyzed by TG and calorimetry, compressive strength testing and mercury intrusion porosimetry. High lime fixation percentages were observed in the hydrated lime and OPC pastes and were higher than 75% and 50% for the ashes burned at 600 °C and 700 °C, respectively. Calorimetry showed a delay in the heat release of SCSA600 and SCSA700 compared to the control paste. These pastes also had higher compressive strength and a smaller total pore volume. The results indicate the positive response of preparing sugar cane ashes under controlled conditions (mainly for straw calcined within the 600-700 °C range) for their use as pozzolanic addition by partially replacing inorganic binders.

Transition of patients with metabolic bone disease from paediatric to adult healthcare services: current situation and proposals for improvement.

BACKGROUND: There are currently no models for the transition of patients with metabolic bone diseases (MBDs) from paediatric to adult care. The aim of this project was to analyse information on the experience of physicians in the transition of these patients in Spain, and to draw up consensus recommendations with the specialists involved in their treatment and follow-up. METHODS: The project was carried out by a group of experts in MBDs and included a systematic review of the literature for the identification of critical points in the transition process. This was used to develop a questionnaire with a total of 48 questions that would determine the degree of consensus on: (a) the rationale for a transition programme and the optimal time for the patient to start the transition process; (b) transition models and plans; (c) the information that should be specified in the transition plan; and (d) the documentation to be created and the training required. Recommendations and a practical algorithm were developed using the findings. The project was endorsed by eight scientific societies. RESULTS: A total of 86 physicians from 53 Spanish hospitals participated. Consensus was reached on 45 of the 48 statements. There was no agreement that the age of 12 years was an appropriate and feasible point at which to initiate the transition in patients with MBD, nor that a gradual transition model could reasonably be implemented in their own hospital. According to the participants, the main barriers for successful transition in Spain today are lack of resources and lack of coordination between paediatric and adult units. CONCLUSIONS: The TEAM Project gives an overview of the transition of paediatric MBD patients to adult care in Spain and provides practical recommendations for its implementation.

Evaluation of Thermochemical Treatments for Rice Husk Ash Valorisation as a Source of Silica in Preparing Geopolymers.

The use of geopolymers has revolutionized research in the field of construction. Although their carbon footprint is often lower than that of traditional mortars with Portland cement, activators such as sodium silicate have a high environmental impact in the manufacturing of materials. Employing alternative alkali sources to produce geopolymers is necessary to obtain materials with a lower carbon footprint. The present research explores the use of rice husk ash (RHA) as an alternative source of silica to produce alkaline activators by four methods: reflux; high pressure and temperature reaction; thermal bath at 65 °C; and shaking at room temperature. To evaluate the efficiency of these methods, two types of experiments were performed: (a) analysing silica dissolved by the filtering/gravimetric method; and (b) manufacturing mortars to compare the effectiveness of the treatment in mechanical strength terms. The percentages of dissolved silica measured by the gravimetric method gave silica dissolution values of 70-80%. The mortars with the best mechanical strength results were the mixtures prepared with the thermal bath treatment at 65 °C. Mortar cured for 1 day (at 65 °C), prepared with this activator, yielded 45 MPa versus the mortar with commercial reagents (40.1 MPa). It was generally concluded that utilising original or milled RHA in preparing activators has minimal influence on either the percentage of dissolved silica or the mechanical strength development of the mortars with this alternative activator.

Lipidic profiles of patients starting peritoneal dialysis suggest an increased cardiovascular risk beyond classical dyslipidemia biomarkers.

Patients on peritoneal dialysis (PD) have an increased risk of cardiovascular disease (CVD) and an atherogenic lipid profile generated by exposure to high glucose dialysis solutions. In the general population, the reduction of classic lipids biomarkers is associated with improved clinical outcomes; however, the same results have not been seen in PD population, a lack of data this study aims to fulfill. Single-center prospective observational study of a cohort of CKD patients who started renal replacement therapy with continuous ambulatory peritoneal dialysis. The differences in the lipid profile and analytical variables before and 6 months after the start of peritoneal dialysis were analyzed. Samples were analyzed on an Ultra-Performance Liquid Chromatography system. Thirty-nine patients were enrolled in this study. Their mean age was 57.9 ± 16.3 years. A total of 157 endogenous lipid species of 11 lipid subclasses were identified. There were significant increases in total free fatty acids (p < 0.05), diacylglycerides (p < 0.01), triacylglycerides, (p < 0.01), phosphatidylcholines (p < 0.01), phosphatidylethanolamines (p < 0.01), ceramides (p < 0.01), sphingomyelins (p < 0.01), and cholesterol esters (p < 0.01) from baseline to 6 months. However, there were no differences in the classical lipid markers, neither lysophosphatidylcholines, monoacylglycerides, and sphingosine levels. 6 months after the start of the technique, PD patients present changes in the lipidomic profile beyond the classic markers of dyslipidemia.

Reusing Construction and Demolition Waste to Prepare Alkali-Activated Cement.

Large amounts of waste are derived not only from construction processes, but also the demolition of existing buildings. Such waste occupies large volumes in landfills, which makes its final disposal difficult and expensive. Reusing this waste type is generally limited to being employed as filler material or recycled aggregate in concrete, which limits its valorisation. The present work proposes reusing construction and demolition waste to manufacture alkali-activated cement to improve its sustainability and recovery. Construction and demolition waste (C&DW) from a demolition waste collection plant in Valencia (Spain) was physically and chemically characterised. This residue contained large fractions of concrete, mortar, bricks, and other ceramic materials. X-ray fluorescence (XRF) analysis showed that its chemical composition was mainly CaO, SiO2 and Al2O3. X-ray diffraction (XRD) analysis revealed that it presented some crystalline products, and quartz (SiO2) and calcite (CaCO3) were the main components. Blends of C&DW and blast furnace slag (BFS) were alkali-activated with mixtures of sodium hydroxide and sodium silicate. The corresponding pastes were characterised by techniques such as thermogravimetry and scanning electron microscopy (SEM). The alkali-activated mortars were prepared, and the resulting mortars' compressive strength was determined, which was as high as 58 MPa with the 50% C&DW-50% BFS mixture. This work concluded that it is possible to make new sustainable binders by the alkali activation of C&DW-BFS without using Portland cement.

Hybrid Lime-Pozzolan Geopolymer Systems: Microstructural, Mechanical and Durability Studies.

This work studies the possibility of using geopolymer materials to enhance the mechanical and durability properties of hydrated lime-pozzolan mixtures, which gave rise to the so-called "hybrid systems". Two different waste types were used as pozzolan in the lime-pozzolan system: rice husk ash (RHA) and spent fluid catalytic cracking (FCC). The geopolymer fabricated with FCC was activated with commercial reagents (NaOH and Na2SiO3), and also with alternative sources of silica to obtain a lower carbon footprint in these mixtures. The alternative silica sources were RHA and residual diatomaceous earth (RDE) from the beer industry. The geopolymer mixture substituted the lime-pozzolan mixture for 30% replacement in weight. The hybrid systems showed better mechanical strengths for the short and medium curing ages in relation to the lime-pozzolan mixtures. Thermogravimetric analyses were performed to characterise the types of products formed in these mixtures. In the durability studies, hybrid systems better performed in freeze-thaw cycles and obtained lower capillarity water absorption values.

Development and Testing of a Portable Virtual Reality-Based Mirror Visual Feedback System with Behavioral Measures Monitoring.

Virtual Reality (VR) is a technology that has been used to provide the Mirror Visual Feedback (MVF) illusion to patients with promising results. In the present work, the goal is to design, develop and test a portable VR-based MVF system that monitors behavioral information about the performance of a simple motor task. The developed application runs in a stand-alone VR system and allows the researcher to select the real and virtual hands used to perform the motor task. The system was evaluated with a group of twenty healthy volunteers (12 men and 8 women) with ages between 18 and 66 years. Participants had to repetitively perform a motor task in four different experimental conditions: two mirror conditions (performing real movements with the dominant and with the non-dominant hand) and two non-mirror conditions. A significant effect of the experimental condition on embodiment score (p < 0.001), response time (p < 0.001), performance time (p < 0.001), trajectory length (p < 0.004) and trajectory maximum horizontal deviation (p < 0.001) was observed. Furthermore, a significant effect of the experimental moment (initial, middle and final parts of the training) on the performance time was observed (p < 0.001). These results show that the monitored parameters provide relevant information to evaluate the participant's task performance in different experimental conditions.

Incidence, Clinical Characteristics, Risk Factors, and Outcomes of Upper Gastrointestinal Bleeding in Patients With COVID-19: Results of the UMC-19-S12.

OBJECTIVE: The authors investigated the incidence, risk factors, clinical characteristics, and outcomes of upper gastrointestinal bleeding (UGB) in patients with coronavirus disease 2019 (COVID-19), who were attending the emergency department (ED), before hospitalization. METHODS: We retrospectively reviewed all COVID-19 patients diagnosed with UGB in 62 Spanish EDs (20% of Spanish EDs, case group) during the first 2 months of the COVID-19 outbreak. We formed 2 control groups: COVID-19 patients without UGB (control group A) and non-COVID-19 patients with UGB (control group B). Fifty-three independent variables and 4 outcomes were compared between cases and controls. RESULTS: We identified 83 UGB in 74,814 patients with COVID-19 who were attending EDs (1.11%, 95% CI=0.88-1.38). This incidence was lower compared with non-COVID-19 patients [2474/1,388,879, 1.78%, 95% confidence interval (CI)=1.71-1.85; odds ratio (OR)=0.62; 95% CI=0.50-0.77]. Clinical characteristics associated with a higher risk of COVID-19 patients presenting with UGB were abdominal pain, vomiting, hematemesis, dyspnea, expectoration, melena, fever, cough, chest pain, and dysgeusia. Compared with non-COVID-19 patients with UGB, COVID-19 patients with UGB more frequently had fever, cough, expectoration, dyspnea, abdominal pain, diarrhea, interstitial lung infiltrates, and ground-glass lung opacities. They underwent fewer endoscopies in the ED (although diagnoses did not differ between cases and control group B) and less endoscopic treatment. After adjustment for age and sex, cases showed a higher in-hospital all-cause mortality than control group B (OR=2.05, 95% CI=1.09-3.86) but not control group A (OR=1.14, 95% CI=0.59-2.19) patients. CONCLUSIONS: The incidence of UGB in COVID-19 patients attending EDs was lower compared with non-COVID-19 patients. Digestive symptoms predominated over respiratory symptoms, and COVID-19 patients with UGB underwent fewer gastroscopies and endoscopic treatments than the general population with UGB. In-hospital mortality in COVID-19 patients with UGB was increased compared with non-COVID patients with UGB, but not compared with the remaining COVID-19 patients.

Características clínicas, asistenciales y evolutivas de la insuficiencia cardiaca aguda en el clima subtropical: resultados del estudio CANAR-ICA / Acute heart failure in subtropical climates: clinical characteristics, management, and outcomes in the Canary Islands versus continental Spain — the CANAR-ICA study results

Objetivo: Investigar si existen diferencias clínicas, asistenciales y evolutivas entre los episodios de insuficiencia cardiaca aguda (ICA) desarrollados en residentes en las Islas Canarias (CAN), de clima subtropical, y en los del territorio español continental (CON). Método: Los pacientes con ICA incluidos en el registro EAHFE se dividieron en CAN o CON. Se recogieron 38 variables demográficas, de estado clínico basal, clínicas y terapéuticas. Se analizó la mortalidad intrahospitalaria y a los 30 días, la hospitalización prolongada (> 7 días) y el evento combinado post-alta (reconsulta o muerte a 30 días). Se compararon los pacientes CAN y CON, ajustando los resultados por las diferencias entre grupos. Resultados: Se incluyeron 18.390 pacientes: CAN = 697 (3,8%), CON = 17.673 (96,2%). Tras el ajuste, los CAN eran más jóvenes, más frecuentemente mujeres, tenían más antecedentes de hipertensión, diabetes e ICA previa, y estaban en clase funcional más avanzada, pero tenían menos dislipemia, valvulopatías y dependencia funcional, y recibían menos frecuentemente inhibidores del eje renina-angiotensina. Aunque la gravedad del episodio de descompensación fue similar, los CAN recibían más tratamientos endovenosos en urgencias y se hospitalizaban menos. El riesgo ajustado de hospitalización prolongada en los CAN resultó incrementado (OR 2,36; IC 95%:1,52-3,02), pero no hubo diferencias en la mortalidad intrahospitalaria (OR 0,97; IC 95%: 0,68-1,37), a 30 días (OR 0,9; IC 95%: 0,67-1,27) o en los eventos combinados post-alta a los 30 días (OR 1,19; IC 95%: 0,93-1,53). (AU)

Objectives: To determine whether there are differences in the clinical characteristics, management, and outcome of episodes of acute heart failure (AHF) in residents of the Canary Islands, where the climate is subtropical, and episodes in continental Spain. Material and methods: Cases were identified in the registry for Epidemiology of Acute Heart Failure in Emergency Departments and categorized as in the Canary Islands or continental Spain. Data for 38 demographic, baseline, clinical, and therapeutic variables were extracted. We analyzed statistics for in-hospital and 30-day mortality, long hospital stay (more than 7 days), and a composite outcome after discharge (revisits or death within 30 days). The results for island and continental patients were compared and adjusted for between-group differences. Results: A total of 18 390 patients were studied, 697 islanders (3.8%) and 17 673 continental patients (96.2%). Comparisons showed that the islanders were younger; more often women; and more likely to have hypertension, diabetes, and a prior AHF episode. Their New York Heart Association functional class was also likely to be higher. However, their rates of dyslipidemia, valve disease, and functional dependence were lower, and they were also less likely to be on reninangiotensin system blockers. Although the severity of cardiac decompensation was similar in island and continental patients, the islanders received more intravenous treatments in the emergency department and were admitted less often. The adjusted risk of a long hospital stay was higher for the islanders (odds ratio [OR], 2.36; 95% CI, 1.52-3.02) but their risk for mortality and the composite outcome did not differ: in-hospital mortality, OR 0.97 (95% CI, 0.68-1.37); 30-day mortality, OR, 0.9 (95% CI, 0.67-1.27); and the post-discharge composite, OR, 1.19 (95% CI, 0.93-1.53). (AU)

Acute heart failure in subtropical climates: clinical characteristics, management, and outcomes in the Canary Islands versus continental Spain - the CANAR-ICA study results. / Características clínicas, asistenciales y evolutivas de la insuficiencia cardiaca aguda en el clima subtropical: resultados del estudio CANAR-ICA.

OBJECTIVES: To determine whether there are differences in the clinical characteristics, management, and outcome of episodes of acute heart failure (AHF) in residents of the Canary Islands, where the climate is subtropical, and episodes in continental Spain. MATERIAL AND METHODS: Cases were identified in the registry for Epidemiology of Acute Heart Failure in Emergency Departments and categorized as in the Canary Islands or continental Spain. Data for 38 demographic, baseline, clinical, and therapeutic variables were extracted. We analyzed statistics for in-hospital and 30-day mortality, long hospital stay (more than 7 days), and a composite outcome after discharge (revisits or death within 30 days). The results for island and continental patients were compared and adjusted for between-group differences. RESULTS: A total of 18 390 patients were studied, 697 islanders (3.8%) and 17 673 continental patients (96.2%). Comparisons showed that the islanders were younger; more often women; and more likely to have hypertension, diabetes, and a prior AHF episode. Their New York Heart Association functional class was also likely to be higher. However, their rates of dyslipidemia, valve disease, and functional dependence were lower, and they were also less likely to be on reninangiotensin system blockers. Although the severity of cardiac decompensation was similar in island and continental patients, the islanders received more intravenous treatments in the emergency department and were admitted less often. The adjusted risk of a long hospital stay was higher for the islanders (odds ratio [OR], 2.36; 95% CI, 1.52-3.02) but their risk for mortality and the composite outcome did not differ: in-hospital mortality, OR 0.97 (95% CI, 0.68-1.37); 30-day mortality, OR, 0.9 (95% CI, 0.67-1.27); and the post-discharge composite, OR, 1.19 (95% CI, 0.93-1.53). CONCLUSION: Baseline patient characteristics and clinical management of AHF episodes differ between the subtropical region and those in southern continental Europe. Hospitalization was required less often, but hospital stays were longer.

OBJETIVO: Investigar si existen diferencias clínicas, asistenciales y evolutivas entre los episodios de insuficiencia cardiaca aguda (ICA) desarrollados en residentes en las Islas Canarias (CAN), de clima subtropical, y en los del territorio español continental (CON). METODO: . Los pacientes con ICA incluidos en el registro EAHFE se dividieron en CAN o CON. Se recogieron 38 variables demográficas, de estado clínico basal, clínicas y terapéuticas. Se analizó la mortalidad intrahospitalaria y a los 30 días, la hospitalización prolongada (> 7 días) y el evento combinado post-alta (reconsulta o muerte a 30 días). Se compararon los pacientes CAN y CON, ajustando los resultados por las diferencias entre grupos. RESULTADOS: Se incluyeron 18.390 pacientes: CAN = 697 (3,8%), CON = 17.673 (96,2%). Tras el ajuste, los CAN eran más jóvenes, más frecuentemente mujeres, tenían más antecedentes de hipertensión, diabetes e ICA previa, y estaban en clase funcional más avanzada, pero tenían menos dislipemia, valvulopatías y dependencia funcional, y recibían menos frecuentemente inhibidores del eje renina-angiotensina. Aunque la gravedad del episodio de descompensación fue similar, los CAN recibían más tratamientos endovenosos en urgencias y se hospitalizaban menos. El riesgo ajustado de hospitalización prolongada en los CAN resultó incrementado (OR 2,36; IC 95%:1,52-3,02), pero no hubo diferencias en la mortalidad intrahospitalaria (OR 0,97; IC 95%: 0,68-1,37), a 30 días (OR 0,9; IC 95%: 0,67-1,27) o en los eventos combinados post-alta a los 30 días (OR 1,19; IC 95%: 0,93-1,53). CONCLUSIONES: Existen diferencias tanto en las características basales como en el manejo clínico de los episodios de insuficiencia cardiaca en los residentes de una región subtropical respecto a los de una zona meridional europea. Además, tienen menor necesidad de hospitalización, aunque estas son más prolongadas.

Design and Validation of an FPGA-Based Configurable Transcranial Doppler Neurofeedback System for Chronic Pain Patients.

Neurofeedback is a self-regulation technique that can be applied to learn to voluntarily control cerebral activity in specific brain regions. In this work, a Transcranial Doppler-based configurable neurofeedback system is proposed and described. The hardware configuration is based on the Red Pitaya board, which gives great flexibility and processing power to the system. The parameter to be trained can be selected between several temporal, spectral, or complexity features from the cerebral blood flow velocity signal in different vessels. As previous studies have found alterations in these parameters in chronic pain patients, the system could be applied to help them to voluntarily control these parameters. Two protocols based on different temporal lengths of the training periods have been proposed and tested with six healthy subjects that were randomly assigned to one of the protocols at the beginning of the procedure. For the purposes of the testing, the trained parameter was the mean cerebral blood flow velocity in the aggregated data from the two anterior cerebral arteries. Results show that, using the proposed neurofeedback system, the two groups of healthy volunteers can learn to self-regulate a parameter from their brain activity in a reduced number of training sessions.

Use of ancient copper slags in Portland cement and alkali activated cement matrices.

Some Chilean copper slag dumps from the nineteenth century still remain, without a proposed use that encourages recycling and reduces environmental impact. In this paper, the copper slag abandoned in landfills is proposed as a new building material. The slags studied were taken from Playa Negra and Púquios dumps, both located in the region of Atacama in northern Chile. Pozzolanic activity in lime and Portland cement systems, as well as the alkali activation in pastes with copper slag cured at different temperatures, was studied. The reactivity of the slag was measured using thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD), electrical conductivity and pH in aqueous suspension and Fourier Transform Infrared Spectroscopy (FTIR). Furthermore, copper slag-Portland cement mortars with the substitution of 25% (by weight) of cement by copper slag and alkali-activated slag mortars cured at 20 and 65 °C were made, to determine the compressive strength. The results indicate that the ancient copper slags studied have interesting binding properties for the construction sector.

Assessment of Pozzolanic Activity Using Methods Based on the Measurement of Electrical Conductivity of Suspensions of Portland Cement and Pozzolan.

The use of methods based on measuring electrical conductivity to assess pozzolanic activity has recently been used primarily in aqueous suspensions of pozzolan: calcium hydroxide. However, the use of similar methods in suspensions of cement with pozzolans has not been widely studied. This paper proposes a new method for rapid assessment of the pozzolanic activity of mineral admixtures in aqueous cement suspensions. In this study, the conditions for the application of the method were optimized, such as time, temperature, w/c ratio and dosage procedure. Finally, results are presented from the application of this method for characterizing the pozzolanic activity of the spent catalytic cracking catalyst. These results corroborate as previously reported, namely the high reactivity of this pozzolan obtained by other methods, such as thermogravimetry or evolution of the mechanical strength. In addition, the pozzolanic activity of the catalyst was compared with other pozzolans such as metakaolin and silica fume.

Assessment of the Pozzolanic Activity of a Spent Catalyst by Conductivity Measurement of Aqueous Suspensions with Calcium Hydroxide.

The pozzolanic activity of the spent catalyst produced by fluid catalytic cracking (FCC) has been studied by various methods in recent years. However, no quick and easy method has been reported for this activity based on the associated studies. In this work, the pozzolanic activity of a spent catalyst was investigated by measuring its electrical conductivity in aqueous suspensions of pozzolan/calcium hydroxide. The behavior of the FCC catalyst residue was compared to that of reactive and inert materials of similar chemical compositions. Further, the influence of temperature on the suspension was studied, and also, a new method was proposed in which the pozzolan/calcium hydroxide ratio was varied (with the initial presence of solid Ca(OH)2 in the system). It was concluded that the method is effective, fast and simple for evaluating the high reactivity of the catalyst. Therefore, this method is an alternative for the evaluation of the reactivity of pozzolanic materials.

Use of Slag/Sugar Cane Bagasse Ash (SCBA) Blends in the Production of Alkali-Activated Materials.

Blast furnace slag (BFS)/sugar cane bagasse ash (SCBA) blends were assessed for the production of alkali-activated pastes and mortars. SCBA was collected from a lagoon in which wastes from a sugar cane industry were poured. After previous dry and grinding processes, SCBA was chemically characterized: it had a large percentage of organic matter (ca. 25%). Solutions of sodium hydroxide and sodium silicate were used as activating reagents. Different BFS/SCBA mixtures were studied, replacing part of the BFS by SCBA from 0 to 40% by weight. The mechanical strength of mortar was measured, obtaining values about 60 MPa of compressive strength for BFS/SCBA systems after 270 days of curing at 20 °C. Also, microstructural properties were assessed by means of SEM, TGA, XRD, pH, electrical conductivity, FTIR spectroscopy and MIP. Results showed a good stability of matrices developed by means of alkali-activation. It was demonstrated that sugar cane bagasse ash is an interesting source for preparing alkali-activated binders.

Increase of the reactivity of densified silica fume by sonication treatment.

Five silica fumes from different manufacturers were subjected to ultrasonic treatment in order to decrease particle agglomeration and improve particle dispersion. The effectiveness of the sonication was observed as a reduction in particle size distribution of sonicated silica fume (SSF) compared to non-sonicated silica fume. SSF was added to Portland cement, and then the hydrated paste was analysed by thermogravimetric analyses (TGA/DTG) and scanning electron microscopy (SEM/EDX). The results were compared with those of control pastes made with untreated densified silica fume (DSF), as well as a reference cement paste of ordinary Portland cement (OPC). A maximum grade of de-agglomeration by the sonication was obtained, with a high volume of particles of diameter less than 1 µm. Images obtained by transmission electron microscopy (TEM) of the SSF showed sintered particles that could not be fragmented by the treatment. Micro-structural characterisation results showed an increase in the reactivity of the silica fume after the treatment.