Adilson A. Freitas, Rodrigo Lino Santos, R. Colaço, Ricardo Bayão Horta, José N. Canongia Lopes,
Thirteen different cement-clinker crystalline phases present in the lime-silica-alumina system have been systematically modeled using a simple and general force field. This constitutes a new type of approach towards the study of lime-silica-alumina systems, where the simpler and more transferable Lennard-Jones potential was used instead of the more traditional Buckingham potential. The results were validated using experimental density and structural data. The elastic properties were also considered. ...
Tópico(s): Clay minerals and soil interactions
2015 - Royal Society of Chemistry | Physical Chemistry Chemical Physics
Patrizia Paradiso, Rodrigo Lino Santos, Ricardo Bayão Horta, José N. Canongia Lopes, P.J. Ferreira, R. Colaço,
Pastes of calcium silicate binders with low CaO/SiO2 (C/S) ratio with an overall C/S molar ratio of 1.1 were produced by mixing these materials with water or with an aqueous solution of Na2SiO3. Both types of pastes (non-activated and Na2SiO3 activated) were analysed using X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM). The observations show that the hydration process of this novel type of cements results in the formation of tobermorite nanocrystals embedded in ...
Tópico(s): Recycling and utilization of industrial and municipal waste in materials production
2018 - Elsevier BV | Acta Materialia
Mónica Antunes, Rodrigo Lino Santos, João R. Pereira, Paulo Novis Rocha, Ricardo Bayão Horta, R. Colaço,
Currently, the production of one ton of ordinary Portland cement (OPC) releases considerable amounts of CO2 into the atmosphere. As the need and demand for this material grows exponentially, it has become a challenge to increase its production at a time when climate-related problems represent a major global concern. The two main CO2 contributors in this process are fossil fuel combustion to heat the rotary kiln and the chemical reaction associated with the calcination process, in the production of ...
Tópico(s): Recycling and utilization of industrial and municipal waste in materials production
2021 - Multidisciplinary Digital Publishing Institute | Materials
Rodrigo Lino Santos, Ricardo Bayão Horta, João R. Pereira, Teresa Nunes, Paulo Novis Rocha, José N. Canongia Lopes, R. Colaço,
In this paper we describe the production of CaO/SiO2-based hydraulic binders formed of dendritic belite embedded in an amorphous phase. These hydraulic binders are produced by a process involving heating the raw materials with a specified CaO/SiO2 ratio to a temperature bellow the liquidus surface, followed by a two-step cooling ramp, in order to obtain during solidification a dendritic morphology of the crystalline phase. After milling the clinker obtained by this process, and by adding up to 25% ...
Tópico(s): Advanced ceramic materials synthesis
2015 - Elsevier BV | Cement and Concrete Research
Rodrigo Lino Santos, Ricardo Bayão Horta, João R. Pereira, Teresa Nunes, Paulo Novis Rocha, R. Colaço,
Abstract A quasi‐amorphous low‐calcium‐silicate hydraulic binder, with an overall CaO/SiO 2 (C/S) molar ratio of 1.1, was produced. This cementitious material was then hydrated with aqueous solutions containing 3 wt% alkalis (either Na OH , Na 2 CO 3 or Na 2 SiO 3 ). The evolution of the hydration processes of the samples were monitored by compressive strength testing, XRD , FTIR , 29 Si and 27 Al MAS NMR , isothermal calorimetry and TGA . It was found that the nearly exclusive hydration product formed was a C‐ ...
Tópico(s): Innovative concrete reinforcement materials
2018 - Wiley | Journal of the American Ceramic Society
Rodrigo Lino Santos, Ricardo Bayão Horta, João R. Pereira, Teresa Nunes, Paulo Novis Rocha, José N. Canongia Lopes, R. Colaço,
New amorphous calcium silicate binders, hydraulically active, were produced by a process consisting in fully melting and rapid cooling of a mixture of typical raw materials (limestone, sand, fly-ash and electric furnace slag) with overall CaO/SiO2 molar ratios (C/S) comprised between 1.1 and 1.25. Pastes were produced from these materials by mixing them with water in a water/binder ratio of 0.375. Compressive strength was determined at the ages of 7, 28 and 90 days and the hydration of these pastes ...
Tópico(s): Magnesium Oxide Properties and Applications
2016 - Elsevier BV | Cement and Concrete Research
Mónica Antunes, Rodrigo Lino Santos, João R. Pereira, Ricardo Bayão Horta, Patrizia Paradiso, R. Colaço,
In this work, the apparent activation energy (Ea) of a novel low-calcium binder was, for the first time, experimentally determined, using a calorimetric approach. Additionally, a correlation between the Ea, measured at the acceleration period with the C/S ratio of the hydration product is proposed. The Ea of the prepared pastes was determined through isothermal calorimetry tests by calculating the specific rate of reaction at different temperatures, using two different approaches. When comparing ...
Tópico(s): Magnesium Oxide Properties and Applications
2021 - Multidisciplinary Digital Publishing Institute | Materials
Daniela Santos, Rodrigo Lino Santos, João R. Pereira, Ricardo Bayão Horta, R. Colaço, Patrizia Paradiso,
A systematic investigation of the influence of pseudowollastonite on the performance of a new family of low calcium hydraulic binders is described. Samples of the new low calcium binder were produced by an innovative process consisting of heating and homogenizing the mix of raw materials (limestone, sand, and fuel cracking catalyst) at a constant temperature followed by the rapid cooling of the mixture itself. Different maximum temperatures, close to the melting temperature of the mix, were tested, ...
Tópico(s): Glass properties and applications
2019 - Multidisciplinary Digital Publishing Institute | Materials
Mónica Antunes, Rodrigo Lino Santos, Ricardo Bayão Horta, R. Colaço,
Because of the severe environmental impact of the CO2 emissions associated with the production of ordinary Portland cement (OPC) and the increasing demand for this commodity material, the development of alternative products has become a global concern. One alternative to OPC, or alitic-based clinkers, are amorphous-wollastonitic low-calcium hydraulic binders (AWLCs). This new class of hydraulic binders, described in the literature for the first time in 2015, may significantly reduce the CO2 emissions ...
Tópico(s): Advanced materials and composites
2023 - Multidisciplinary Digital Publishing Institute | Materials
Mónica Antunes, Rodrigo Lino Santos, João R. Pereira, Ricardo Bayão Horta, R. Colaço,
To ensure the acceptable mechanical strength of amorphous wollastonitic hydraulic binders (AWHs), activation with a sodium silicate solution is necessary. However, the use of this type of activator increases the final cost and the complexity of the product’s overall use. In this work, we focus on enhancing the manufacturing of the alkaline activator by producing three Na2SiO3 powders using cost-effective raw materials. The procedure consisted of heating a mixture of NaOH pebbles with either sand, ...
Tópico(s): Building materials and conservation
2024 - Multidisciplinary Digital Publishing Institute | Materials
Mónica Antunes, Rodrigo Lino Santos, Ricardo Bayão Horta, R. Colaço,
In cement industry the use of supplementary cementitious materials (SCMs) play an important role in the reduction of CO2 emissions by allowing a decrease in clinker content. The present work investigates the incorporation of four different SCM into an amorphous wollastonitic hydraulic (AWH) clinker, which requires alkaline activation with a sodium silicate solution. This alkaline activation process could potentially allow the use of some SCMs as precursors within the SCM+AWH mixture. Hence, besides ...
Tópico(s): Recycling and utilization of industrial and municipal waste in materials production
2024 - Elsevier BV | Case Studies in Construction Materials
The present discussion focuses on a particular type of merger: the newly created full-function joint-ventures and specifically, on the practical issues Competition Authorities may face on when to assess this particular kind of mergers, the so-called ‘triggering event’. Its objective is to promote a discussion on the most appropriate moment, from a Competition Authority’s procedural perspective, to analyse a newly created Full-Function Joint Venture (hereinafter, ‘FFJV‘). Considering that the full-functionality ...
Tópico(s): Merger and Competition Analysis
2014 - RELX Group (Netherlands) | SSRN Electronic Journal
Mónica Antunes, Rodrigo Lino Santos, Ricardo Bayão Horta, R. Colaço,
Tópico(s): Recycling and utilization of industrial and municipal waste in materials production
2024 - Elsevier BV | Case Studies in Construction Materials
Mónica Antunes, Rodrigo Lino Santos, Ricardo Bayão Horta, R. Colaço,
This study investigates how different sodium silicate SiO
Tópico(s): Recycling and utilization of industrial and municipal waste in materials production
2024 - Multidisciplinary Digital Publishing Institute | Materials
S Pinheiro, Alexandra Bayão Horta, P Gomes, C Febra, A Ricardo, S. Oliveira, MJ Goes, J Rolo, M Serra, AS Castro,
Tópico(s): Porphyrin Metabolism and Disorders
2004 - Portuguese Society of Internal Medicine | Medicina internă