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1 – 3 of 3Diogo Henrique de Bem, Priscila Ongaratto Trentin and Ronaldo A. Medeiros-Junior
Efflorescence formation is very common in cement-based materials. In the case of mortar, efflorescence is more studied when only Portland cement is used as a binder. However, the…
Abstract
Purpose
Efflorescence formation is very common in cement-based materials. In the case of mortar, efflorescence is more studied when only Portland cement is used as a binder. However, the repair of historical heritage, as well as the construction system of some countries, usually uses mortars composed of hydrated lime and Portland cement. This study aims to determine the influence of the hydrated lime content on the incidence of efflorescence in mortars.
Design/methodology/approach
Mortars with 0%, 50%, and 100% lime/cement ratio were studied, using three different methods to accelerate efflorescence formation. The surface area of mortars affected by efflorescence was quantified by analysis using image software. Also, analysis of mercury intrusion porosity test, flexural tensile, compressive strength, absorption of water by capillarity, porosity, XRD and TGA was performed.
Findings
More efflorescence in mortars with a higher amount of lime in their composition was observed. The results show that the increase in the lime content reduces the flexural tensile and the compressive strength and increased the absorption of water by capillarity and the porosity of the mortars. The material formed by the efflorescence was calcium carbonate, proven by microstructural tests.
Originality/value
The results of greater efflorescence formation in mortars with lime are important to alert users who apply this type of material. Some type of protection must be done more rigorously for lime-cement mortars, especially concerning contact with water, since efflorescence tends to be faster for this type of material.
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Diogo Henrique de Bem, Daniel Petzold Barbosa Lima and Ronaldo A. Medeiros-Junior
The purpose of this paper is to verify the influence of superplasticizer and air entrainment admixtures (AEs) in the electrical resistivity of concrete.
Abstract
Purpose
The purpose of this paper is to verify the influence of superplasticizer and air entrainment admixtures (AEs) in the electrical resistivity of concrete.
Design/methodology/approach
Ten different types of concrete have been studied. Three levels of superplasticizer and air AEs have been used (0.20, 0.35 and 0.50 per cent). Concrete samples were cast and the electrical resistivity was monitored at the ages of 28, 63 and 91 days. Compressive strength and density tests have also been executed.
Findings
The superplasticizer admixture presented an optimal level of 0.35 per cent that significantly increased the electrical resistivity. The air AEs at the same dosage caused a considerable decrease in the electrical resistivity. The concrete with air AEs showed highest resistivity/MPa ratio.
Research limitations/implications
The results should be carefully extrapolated for other materials and admixtures.
Practical implications
The usage of chemicals admixture in concrete is extremely common nowadays. However, only a few authors have studied the impact of such materials on the concrete’s electrical resistivity. Since many other researchers have already correlated electrical resistivity with other concrete’s properties, such as strength, setting time and corrosion probability, it is important to better understand how superplasticizers and air-entraining agents, for instance, impact the resistivity.
Originality/value
The vast majority of studies only tested the resistivity of cement paste or mortar and usually for short period of time (up to 28 days), which seems not to be adequate since the cement reaction continues after that period. This paper fills this gap and studied the impact of admixture on concrete and for a period of 91 days.
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Cléverson Vasconcelos da Nóbrega and Diogo Henrique Helal
The article aims at analyzing the social representations of retirement in two different groups of professors – pre-retired and retired – from a public higher education…
Abstract
Purpose
The article aims at analyzing the social representations of retirement in two different groups of professors – pre-retired and retired – from a public higher education institution. The goal is to explore the experiences, reflections, beliefs, and attitudes originated from the transition to retirement.
Design/methodology/approach
The research, of exploratory and descriptive nature, was guided by the Social Representation Theory (SRT) and took a qualitative approach. 16 professors were interviewed, 8 in each group (pre-retired and retired professors), using semi-structured interviews that followed a script designed to discover the main aspects of the transition to retirement.
Findings
Three figurative cores were raised – the financial aspect, the centrality of work, and the will to continue contributing, and the unpreparedness for retirement – and testimonies have shown heterogeneous representations. The study observed that although relevant, the bonus for continued services is not the main determinant for professors to continue working in the university.
Originality/value
The results of this study indicate the need to treat retirement as a complex and multidimensional process, offering a fresh perspective on the social representations of retirement in the academic context. The use of the Social Representation Theory to explore these perspectives adds to the originality of the approach, highlighting the multifaceted nature of the retirement process in this specific professional group.
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