Research

18 pages, 25328 KiB

Open AccessArticle

Effect of Type of Curing and Metakaolin Replacement on Air Lime Mortars for the Durability of Masonries

by João Monteiro, Vitor Silva and Paulina Faria

Infrastructures 2021, 6(10), 143; https://doi.org/10.3390/infrastructures6100143 - 08 Oct 2021

Cited by 5 | Viewed by 1995

The interest in restoration and maintenance of old masonries towards their durability is nowadays combined with the concept of sustainability and the need to implement more suitable materials for building heritage interventions. This has led to the importance of having a better knowledge [...] Read more.

The interest in restoration and maintenance of old masonries towards their durability is nowadays combined with the concept of sustainability and the need to implement more suitable materials for building heritage interventions. This has led to the importance of having a better knowledge of air lime mortars, namely on the effect of pozzolanic additions, curing conditions and evolution at early stages. This study consisted in the characterization of mortars based on hydrated air lime and sand, with 1:2 (lime:sand) volumetric composition, with different weight percentages of substitution of lime by metakaolin (Mk): 0%, 10% and 20%. Mortar prisms were analyzed in three different curing environments: maritime (by the Atlantic Ocean), in laboratory humidity (95 ± 5% relative humidity, RH) and standard (65 ± 5% RH) conditioning. Tests were conducted to evaluate fresh and hardened properties of mortars, considering physical, chemical and mechanical performance at 28, 90 and 180 days. Results showed the viability of applying air lime-Mk mortars with curing conditions similar to the tested ones. In the standard curing, the mortar with 20% Mk revealed advantages in mechanical parameters. Concerning the behaviour towards water, improvements were shown at an early stage with the humid curing, while maritime curing benefited its behaviour for at least up to 6 months. Full article

(This article belongs to the Special Issue Durability and Degradability of Construction Materials)

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24 pages, 4719 KiB

Open AccessArticle

Uncertainty in Building Inspection and Diagnosis: A Probabilistic Model Quantification

by Clara Pereira, Ana Silva, Cláudia Ferreira, Jorge de Brito, Inês Flores-Colen and José D. Silvestre

Infrastructures 2021, 6(9), 124; https://doi.org/10.3390/infrastructures6090124 - 01 Sep 2021

Cited by 8 | Viewed by 2163

Abstract

In the field of building inspection and diagnosis, uncertainty is common and surveyors are aware of it, although it is not easily measured. This research proposes a model to quantify uncertainty based on the inspection of rendered façades. A Bayesian network is developed, [...] Read more.

In the field of building inspection and diagnosis, uncertainty is common and surveyors are aware of it, although it is not easily measured. This research proposes a model to quantify uncertainty based on the inspection of rendered façades. A Bayesian network is developed, considering three levels of variables: characteristics of the building, façade and exposure conditions; causes of defects; and defects. To compute conditional probabilities, the results of an inspection campaign from the literature are used. Then, the proposed model is validated and verified using inspection results from another sample, the combination of a strength-of-influence diagram and sensitivity analysis and the application of the model to a case study. Results show that the probabilities computed by the model are a reasonable representation of the hesitancy in decision making during the diagnosis process based only on visual observation. For instance, design and execution errors show lower probabilities due to not being verifiable a posteriori without detailed documentation. The proposed model may be extended and replicated for other building materials in the future, as it may be a useful tool to improve the perception of uncertainty in a key stage of building maintenance or rehabilitation. Full article

(This article belongs to the Special Issue Durability and Degradability of Construction Materials)

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15 pages, 4399 KiB

Open AccessArticle

State of Conservation of Concrete Heritage Buildings: A European Screening

by Gabriel Pardo Redondo, Giovanna Franco, Antroula Georgiou, Ioannis Ioannou, Barbara Lubelli, Stefano F. Musso, Silvia Naldini, Cristiana Nunes and Rita Vecchiattini

Infrastructures 2021, 6(8), 109; https://doi.org/10.3390/infrastructures6080109 - 03 Aug 2021

Cited by 6 | Viewed by 2944

Abstract

Historic concrete buildings are at risk. Limited knowledge of concrete technology until the 1960s led to more sensitive buildings than modern concrete buildings. In addition, the lack of sensibility regarding their heritage value and insufficient protection is leading to remorseless demolition. Still, concrete [...] Read more.

Historic concrete buildings are at risk. Limited knowledge of concrete technology until the 1960s led to more sensitive buildings than modern concrete buildings. In addition, the lack of sensibility regarding their heritage value and insufficient protection is leading to remorseless demolition. Still, concrete has proved to be a resilient material that can last over a century with proper care. There is not yet an estimation of the status of historic concrete buildings in Europe. Until now, a few attempts have been done to secondarily, and subjectively, gauge their conservation status. This paper is the result of a joint investigation studying forty-eight historic concrete buildings distributed in four countries. They were surveyed by expert teams according to a predefined methodology. The study aims to identify recurrent damages and parameters affecting the conservation state. It also aims to serve as the first trial for an objective and measurable methodology, to apply it with a statistically significant number of cases. Damages related to the corrosion of reinforcement and moisture-related processes were the most recurrent. The use of plasters, flat roofs, and structural façade walls show a positive effect in protecting the concrete. The state of conservation has a great variability across countries. Full article

(This article belongs to the Special Issue Durability and Degradability of Construction Materials)

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13 pages, 3670 KiB

Open AccessArticle

Influence of Patching on the Shear Failure of Reinforced Concrete Beam without Stirrup

by Stefanus Adi Kristiawan, Halwan Alfisa Saifullah and Agus Supriyadi

Infrastructures 2021, 6(7), 97; https://doi.org/10.3390/infrastructures6070097 - 26 Jun 2021

Cited by 3 | Viewed by 2655

Abstract

Deteriorated concrete cover, e.g., spalling or delamination, especially when it occurs at the web of a reinforced concrete (RC) beam within the shear span, can reduce the shear capacity of the beam. Patching of this deteriorated area may be the best option to [...] Read more.

Deteriorated concrete cover, e.g., spalling or delamination, especially when it occurs at the web of a reinforced concrete (RC) beam within the shear span, can reduce the shear capacity of the beam. Patching of this deteriorated area may be the best option to recover the shear capacity of the beam affected. For this purpose, unsaturated polyester resin mortar (UPR mortar) has been formulated. This research aims to investigate the efficacy of UPR mortar in limiting the shear cracking and so restoring the shear capacity of the deteriorated RC beam. The investigation is carried out by an experimental and numerical study. Two types of beams with a size of 150 × 250 × 1000 mm were prepared. The first type of beams was assigned as a normal beam. The other was a beam with a cut off in the non-stirrup shear span, which was eventually patched with UPR mortar. Two reinforcement ratios were assigned for each type of beams. The results show that UPR mortar is effective to hamper the propagation of diagonal cracks leading to increase the shear failure load by 15–20% compared to the reference (normal) beam. The increase of shear strength with the use of UPR mortar is consistently confirmed at various reinforcement ratios. Full article

(This article belongs to the Special Issue Durability and Degradability of Construction Materials)

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19 pages, 1473 KiB

Open AccessArticle

Effects of the Ratio of Porosity to Volumetric Cement Content on the Unconfined Compressive Strength of Cement Bound Fine Grained Soils

by Teresa Santana, João Gonçalves, Fernando Pinho and Rui Micaelo

Infrastructures 2021, 6(7), 96; https://doi.org/10.3390/infrastructures6070096 - 26 Jun 2021

Cited by 4 | Viewed by 2373

Abstract

This paper presents an experimental investigation into the effects of porosity, dry density and cement content on the unconfined compressive strength and modulus of elasticity of cement-bound soil mixtures. A clayey sand was used with two different proportions of type IV Portland cement, [...] Read more.

This paper presents an experimental investigation into the effects of porosity, dry density and cement content on the unconfined compressive strength and modulus of elasticity of cement-bound soil mixtures. A clayey sand was used with two different proportions of type IV Portland cement, 10% and 14% of the dry mass of the soil. Specimens were moulded with the same water content but using four different compaction efforts, corresponding to four different dry densities. Unconfined compression testing was conducted at seven days of curing time on unsoaked samples. The results showed that the compressive strength increased with the increase in cement content and with the decrease in porosity. From the experimental data, a unique relationship was found between the unconfined compressive strength and the ratio of porosity to volumetric cement content for all the mixtures and compaction efforts tested. The equation developed demonstrates that it is possible to estimate the amount of cement and the dry density to achieve a certain level of unconfined compressive strength. A normalized general equation was also found to fit other authors’ results for similar soils mixed with cement. From this, a cement-bound soil model was proposed for the development of a mixing design procedure for different soils. Full article

(This article belongs to the Special Issue Durability and Degradability of Construction Materials)

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12 pages, 1514 KiB

Open AccessArticle

Cement-Bonded Particleboards with Banana Pseudostem Waste: Physical Performance and Bio-Susceptibility

by Lina Nunes, Eleonora Cintura, João L. Parracha, Bruno Fernandes, Vitor Silva and Paulina Faria

Infrastructures 2021, 6(6), 86; https://doi.org/10.3390/infrastructures6060086 - 13 Jun 2021

Cited by 10 | Viewed by 4740

Abstract

This article evaluates the relevant properties of cement-bonded particleboards (CBPB) made with a portion of maritime pine (Pinus pinaster) particles replaced with an agricultural waste, banana pseudostem (Musa sp.). The industrial production of CBPB was simulated in the laboratory based [...] Read more.

This article evaluates the relevant properties of cement-bonded particleboards (CBPB) made with a portion of maritime pine (Pinus pinaster) particles replaced with an agricultural waste, banana pseudostem (Musa sp.). The industrial production of CBPB was simulated in the laboratory based on a reference composition defined by a manufacturing company. Test specimens were produced assuming 0%, 25%, 50% and 75% partial replacement of wood particles with banana pseudostem fibres. Some physical properties (bulk density, thermal conductivity, and dimensional stability) and the mould susceptibility of the different variables were assessed. Results show that the thermal conductivity of the boards increased with the banana fibre proportion and ranged between 0.233 W/(m.K) and 0.279 W/(m.K). The bulk density values generally increased with the banana fibre proportion and ranged between 1754–1995 kg/m³, being the highest value obtained for B50 (equal weight proportion of wood particles and banana fibres). Specimens with a higher percentage of banana fibres have reduced thickness resulting from swelling, ranging between 0.38% and 0.11% (for 0% and 75% of banana fibres, respectively). CBPBs with unsanded surfaces seem to be unsusceptible to mould development, whereas those with sanded surfaces, simulating wearing, show some bio-susceptibility. Mould development increases with the proportion of banana fibre. The results highlight the need for regular maintenance of the particleboards, thus avoiding surface wear over time and resulting in the exposure of the wood particles and/or banana fibres to the outside environment. Full article

(This article belongs to the Special Issue Durability and Degradability of Construction Materials)

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18 pages, 6539 KiB

Open AccessArticle

Incorporation of Natural Fibres in Rendering Mortars for the Durability of Walls

by Cinthia Maia Pederneiras, Rosário Veiga and Jorge de Brito

Infrastructures 2021, 6(6), 82; https://doi.org/10.3390/infrastructures6060082 - 01 Jun 2021

Cited by 4 | Viewed by 2447

Abstract

One of the main functions of renders, together with the overall aesthetic appearance of the building, is the protection of the walls against external aggressive actions, such as water, salts solutions, erosion, and mechanical impacts. However, some anomalies of renders may drastically hinder [...] Read more.

One of the main functions of renders, together with the overall aesthetic appearance of the building, is the protection of the walls against external aggressive actions, such as water, salts solutions, erosion, and mechanical impacts. However, some anomalies of renders may drastically hinder their protection ability. In fact, cracking, high water permeability, and loss of adherence to the substrate of renders limit their barrier effect and favour the exposure of the substrate to external actions. The incorporation of fibres in mortars is commonly pointed out to reduce their cracking susceptibility, due to the probable enhancement in tensile strength and ductility of the composite. The use of lime in substitution of the part of the cement binder is seen as a method to reduce the modulus of elasticity and therefore enhance the resistance to cracking due to drying shrinkage. Therefore, this study investigates the wall protection-related properties of natural fibre-reinforced renders with cement-lime as a binary binder at 1:1:6 volumetric ratio. With this purpose, wool, coir, and flax fibres are used at 20% by total mortar volume and the water behaviour, cracking susceptibility, and adherence to the substrate of the mortars are assessed. Specifically, the water absorption by capillarity, drying rates, permeability to water under pressure, adherence strength, and shrinkage are evaluated. In order to evaluate the renders’ durability and therefore the durability of the protection to the walls, an artificial accelerated ageing test is performed based on heating-freezing and humidification-freezing cycles. The results indicate that the fibres’ addition reduced the shrinkage and modulus of elasticity of the mortars, which suggests lower susceptibility to cracking. The addition of fibres in mortars seemed to slightly affect their water performance and only at early ages. From the results, it was concluded that the adherence strength is not affected by the fibres’ incorporation. The fibres seem also to reduce the impacts of the ageing cycles on the mortar and the improvements provided by the fibres’ addition to the mortars’ performance remained after ageing when compared to the mortars without fibres, thus being a potential alternative to increase their durability. These aspects are particularly important for buildings, since they can extend their service life and promote their sustainability. Full article

(This article belongs to the Special Issue Durability and Degradability of Construction Materials)

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15 pages, 3302 KiB

Open AccessArticle

Impact of Incorporating NIR Reflective Pigments in Finishing Coatings of ETICS

by Nuno M. M. Ramos, Joana Maia, Andrea R. Souza, Ricardo M. S. F. Almeida and Luís Silva

Infrastructures 2021, 6(6), 79; https://doi.org/10.3390/infrastructures6060079 - 25 May 2021

Cited by 20 | Viewed by 2802

Abstract

Near-infrared (NIR) reflective materials are being developed for mitigating building cooling needs. Their use contributes to broadening the range of colours, responding to the urban aesthetic demand without compromising the building performance. Despite the increase in NIR reflective pigments investigation, there is still [...] Read more.

Near-infrared (NIR) reflective materials are being developed for mitigating building cooling needs. Their use contributes to broadening the range of colours, responding to the urban aesthetic demand without compromising the building performance. Despite the increase in NIR reflective pigments investigation, there is still a knowledge gap in their applicability, impact, and durability in multilayer finishing coatings of External Thermal Insulation Composite Systems (ETICS). Hence, the main goal of this work consists of evaluating the impact of incorporating NIR reflective pigments (NRP) in the solar reflectance of the surface layer of ETICS, without affecting the colour perception, as well as their influence on the colour durability and surface temperature. As such, colour, solar reflectance, and surface temperature were monitored for 2 years in dark-coloured specimens of ETICS, with and without NRP and a primer layer. It was confirmed that the main contribution of NRP is the increase of solar reflectance and, consequently, the decrease in surface temperature, especially for high exterior temperatures (around 30 °C). Moreover, these pigments highly increase the NIR reflectance without affecting the visible colour. In addition, they contribute to maintaining the colour characteristics. The application of primer increased the surface temperature, especially for higher exterior temperatures. However, it contributes to a lower colour difference and solar reflectance variation, which is an important achievement for durability purposes. Full article

(This article belongs to the Special Issue Durability and Degradability of Construction Materials)

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17 pages, 1922 KiB

Open AccessArticle

Performance and Durability of Rendering and Basecoat Mortars for ETICS with CSA and Portland Cement

by Tiago Trigo, Inês Flores-Colen, Luís Silva, Nuno Vieira, Ana Raimundo and Giovanni Borsoi

Infrastructures 2021, 6(4), 60; https://doi.org/10.3390/infrastructures6040060 - 17 Apr 2021

Cited by 4 | Viewed by 2317

Abstract

The production of Portland cement (OP) is commonly associated to significant level of energy consumption and gas emissions. The use of calcium sulfoaluminate cement (CSA) can be a sustainable alternative binder, since its production releases about half of the CO₂ emissions and [...] Read more.

The production of Portland cement (OP) is commonly associated to significant level of energy consumption and gas emissions. The use of calcium sulfoaluminate cement (CSA) can be a sustainable alternative binder, since its production releases about half of the CO₂ emissions and its clinker requires 200 °C lower temperatures, when compared to OP. Furthermore, CSA has fast setting time and achieves higher strength in shorter periods, as well as reduced shrinkage. This paper discusses the incorporation of CSA in rendering mortars and basecoat mortars for ETICS (External Thermal Insulation Composite Systems). The physical-mechanical properties of mortars made with OP and CSA cements were experimental evaluated. The results showed that the introduction of CSA generally improves shrinkage, compressive strength, water absorption at low pressure, enhances the tensile bending strength and decreases the setting time. The amount of CSA introduced into the mixture significantly affected the properties of the cement matrix. Full article

(This article belongs to the Special Issue Durability and Degradability of Construction Materials)

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