Performance of Silica Fume-Based Geopolymer Grouts for Heritage Masonry Consolidation

UID/CTM/50025 SFRH/BPD/108427/2015Despite the increasing number of studies on geopolymer-based materials, a lack of information still prevails concerning the use of geopolymer materials for the consolidation and conservation of the built heritage. Since the introduction of the term “geopolymer” by Davidovits, several studies have pointed out geopolymers as a potential replacement for traditional binders, mainly due to their advantages associated with mechanical properties and low carbon dioxide emissions. The geopolymers (also known as alkali-activated materials or inorganic polymers) are obtained by a chemical process through which precursors rich in silica and alumina interact with an alkaline medium to result in a material with binding properties. The aim of this study is to exploit the potential of geopolymer-based grouts in the consolidation of stone masonry buildings. Grouting or grout injection is a technique used for the consolidation of heritage masonry buildings; it consists of the introduction of a binding agent to fill the internal voids and cracks. An experimental program was carried out to improve knowledge of geopolymer grouts suitable for consolidation purposes. The experimental findings revealed that the silica-fume-based geopolymer grout has a worse performance from a rheological point of view, whereas it showed promising results in terms of mechanical strength when compared to traditional hydraulic-lime-based grout.publishersversionpublishe

Use of Wood Waste as Aggregate in Mortars: An Experimental Study

The construction sector is one of the largest and most active in the world economy, being responsible for consumption of huge amounts of natural resources. Natural sand and gravel are the most important resources in construction, they are mainly used as aggregates, and its extraction often causes environmental damages. Bearing these considerations in mind, the wood waste has been used as partial replacement of natural sand in concrete and mortars to reduce the environmental burden of natural sand extraction. The aim of this paper is to characterize the physical and mechanical properties of natural hydraulic lime-based mortars proportioned with different percentages of wood wastes (0% to 30%) as replacement of natural sand. Thus, several specimens of mortar proportioned with wood wastes have been subjected to different experimental procedures, such as: workability, mechanical strength, water absorption and thermal conductivity. Results obtained showed that the incorporation of wood waste causes a reduction of mechanical resistance mostly due to the increase in open porosity, but on the other hand the thermal conductivity presents an improvement up to 83%. The results obtained are quite acceptable and encouraging for the follow-up studies using wood wastes as fine aggregate in mortars and, simultaneously, to improve the energy efficiency of buildings since this waste material contributes to obtain mortars with improved thermal performance.publishersversionpublishe

Preliminary Investigation of the Mechanical and Physical Properties of Natural Hydraulic Lime Grouts with Nano-Silica

This research was funded by Portuguese National Funds through FCT—Portuguese Foundation for Science and Technology, Reference UID/CTM/50025/2019 and FCT/MCTES under the Grant SFRH/BPD/108427/2015.Natural hydraulic lime-based grouts are often used in the structural consolidation of old stone masonry walls, mainly to re-establish the monolithic behaviour of masonry constructions. To ensure an adequate grouting operation, it is essential to have good fresh and hardened grout properties. The motivation of the present study was to examine the fresh and hardened properties of natural hydraulic lime grouts with nano-silica (NS) and silica fume (SF). The contribution of these materials and the dosage of a high range water reducer admixture (HRWR) were investigated on the rheological properties, water capillarity, open porosity and mechanical strength of injection grouts. The effects on rheology were analysed through plastic viscosity and yield stress. The results indicated that, even for reduced NS content, an increase in plastic viscosity and yield stress occurred, which required a higher HRWR content in order to not compromise the grout’s rheological performance. The results also showed that, when NS and SF were combined, a beneficial joint effect occurred, resulting in a substantial and positive change on the mechanical strength and microstructure of the hardened injection grouts. Taguchi’s method was used to optimize the grout’s formulation and to fulfil the required performance concerning the fresh and hardened state.publishersversionpublishe

Transport inefficiency in branched-out mesoscopic networks: An analog of the Braess paradox

We present evidence for a counter-intuitive behavior of semiconductor mesoscopic networks that is the analog of the Braess paradox encountered in classical networks. A numerical simulation of quantum transport in a two-branch mesoscopic network reveals that adding a third branch can paradoxically induce transport inefficiency that manifests itself in a sizable conductance drop of the network. A scanning-probe experiment using a biased tip to modulate the transmission of one branch in the network reveals the occurrence of this paradox by mapping the conductance variation as a function of the tip voltage and position.Comment: 2nd version with minor stylistic corrections. To appear in Phys. Rev. Lett.: Editorially approved for publication 6 January 201

Experimental study and modeling of rheological and mechanical properties of NHL grouts

The support from the strategic project Pest-C/CTM/LA0025/2011This paper aims to model the effect of grout composition on properties of two natural hydraulic lime (NHL) grouts based on the correlation between grout rheometer results and simple flow tests. First, the effects of water:binder ratio and superplasticizer dosage on its rheological properties and flowability were analyzed. Dosage of superplasticizer and water:binder ratio were varied from 0.6 to 1.2% (by mass of binder) and 0.45-0.55, respectively. A good correlation between classical flow tests and the rheological properties was obtained. Then, statistical models were formulated in order to estimating the grout parameters, such as plastic viscosity and yield stress just by performing simple flow tests. The models coefficients were calculated using multiple regression analysis. The statistical modeling results indicated that the properties of the grouts studied are linearly related to water:binder ratio, superplasticizer dosage, and specific surface area of natural hydraulic limes. Finally, the accuracy of the models was experimentally confirmed using random grout compositions. The predicted-to-measured ratio ranged from 0.97 to 1.08, indicating a good agreement between the confirmation results and the expected results from the statistical models.authorsversionpublishe

Effects of polypropylene fibers and measurement methods on the yield stress of grouts for the consolidation of heritage masonry walls

FeDeR funds through the COMPeTe 2020 Programme under the project number POCI-01-0145-FeDeR-007688.The injection of grouts is a consolidation technique suitable for overcoming the structural deterioration of old stone masonry walls. Grouting operations involve introducing a suspension (grout) into a masonry core with the aim of improving the load capacity of the wall, as well as reducing its brittle mechanisms. The yield stress of injection grouts will affect the injection pressure and their flow inside the masonry. However, the determination of some rheological properties such as yield stress in hydraulic grout is challenging, due to the combined effects of hydration reactions and interactions between the particles present in the suspension. In this study, the determination of the yield stress of natural hydraulic lime-based grouts with polypropylene fibers was carried out. The changes in yield stress with time, fibers content and hydration were evaluated by two measurement methods using a rotational rheometer. Additionally, the static and dynamic yield stress as well as the critical shear-strain rate were determined, which provided useful information on the grout design in order to achieve successful grouting operations.publishersversionpublishe

Developing "BUILDING/ FACILITY ENERGY CONSUMPTION DATA SHEET" for Political Subdivisions, Institutions of Higher Education, and State Agencies, to Satisfy Senate Bill 898 (82nd R) Reporting Requirements

As mandated by the 82nd R Legislature (2011), Senate Bill 898, Health and Safety Code, Section 388.005, beginning September 1, 2011, each political subdivision, institution of higher education or state agency shall establish a goal to reduce the electric consumption by the entity by at least 5% each state fiscal year for 10 years. Each entity annually is to report to the State Energy Conservation Office (SECO), on forms provided by SECO, regarding the entity's goal, the entity's efforts to meet the goal, and progress the entity has made. An entity that does not attain the 5% goal must include in the report justification that the entity has already implemented all available cost-effective measures. SECO is to annually provide the commission and the Energy Systems Laboratory (Laboratory) with an evaluation of the effectiveness of state and political subdivision energy efficiency programs. The Laboratory is mandated to calculate, based on the evaluation and the forms submitted to the office, the amount of energy savings and estimated reduction in pollution achieved as a result of the implementation of the programs, and then provide the information to the Texas Commission on Environmental Quality, the United States Environmental Protection Agency, and the Electric Reliability Council of Texas to help with long-term forecasting and in estimating pollution reduction. During the first quarter of 2012, the Laboratory, working with SECO, devised and proposed to SECO a standardized form for use by political subdivisions, institutions of higher education and state agencies in order to satisfy the new reporting requirements set by Senate Bill 898. The form contains the minimum information needed to show an accurate estimated energy savings and estimated reduction in pollution as a result of the implementation of the programs. In July 2012, the basic form proposed by the ESL was enhanced electronically so that the form could be filled on a computer and emailed back, and the data could be pulled automatically. The form that was proposed to SECO by the ESL appears on the next page (showing default dates that could be changed by the submitter)

Corelates of Legalism in a Global Sample of Seventh-day Adventists

The Seventh-day Adventist Church is often identified as a strict church (Iannaccone, 1994; Chen et al., 2019; McBride et al., 2020) in that it has specific dietary and behavioral requirements for joining and continued membership. These include abstinence from alcohol, tobacco, and illicit drugs as well as a strong emphasis on vegetarianism (McBride et al., 2020). This has resulted in longevity advantage for Adventists (Fraser et al., 2020). This focus on behavioral requirements have resulted in critics viewing Adventists as legalists (WELS, 2022). The purpose of this research is to examine the issue of legalism among Adventist Church members

Increased pathogenicity of pneumococcal serotype 1 is driven by rapid autolysis and release of pneumolysin

Streptococcus pneumoniae serotype 1 is the predominant cause of invasive pneumococcal disease in sub-Saharan Africa, but the mechanism behind its increased invasiveness is not well understood. Here, we use mouse models of lung infection to identify virulence factors associated with severe bacteraemic pneumonia during serotype-1 (ST217) infection. We use BALB/c mice, which are highly resistant to pneumococcal pneumonia when infected with other serotypes. However, we observe 100% mortality and high levels of bacteraemia within 24 hours when BALB/c mice are intranasally infected with ST217. Serotype 1 produces large quantities of pneumolysin, which is rapidly released due to high levels of bacterial autolysis. This leads to substantial levels of cellular cytotoxicity and breakdown of tight junctions between cells, allowing a route for rapid bacterial dissemination from the respiratory tract into the blood. Thus, our results offer an explanation for the increased invasiveness of serotype 1

Estrogen protection in Parkinson´s disease – a GDNF role?

Estrogen protection in Parkinson´s disease – a GDNF role