scholarly journals Experimental procedure for studying the degradation and alteration of limestone slabs applied on exterior cladding

2021 ◽  
Author(s):  
Vera Pires ◽  
P. M. Amaral ◽  
J. A. R. Simão
Keyword(s):  
Strong Influence ◽  
Mechanical Performance ◽  
Construction Materials ◽  
Rock Cutting ◽  
Clay Material ◽  
Fluid Circulation ◽  
Experimental Procedure ◽  
Standard Procedures ◽  
Anchoring System ◽  
Ventilated Facade

Abstract The studied limestone is a well known Portuguese natural stone that occurs in Valverde – Alcanede region, located in the Maciço Calcário Estremenho (centre of Portugal). This stone is used in several exterior and interior applications such as paving, cladding, masonry and decorations. Slabs made of the studied limestone were installed in ventilated facade with a “kerf” anchoring system in a building located in Valencia (Spain). After approximately five years, signs of degradation were detected on the facades through changes in color, cracks and fissures that caused instability and collapse on several slabs. Limestone slabs comprise irregular patterns due to rock cutting across stylolites. These features represent ideal paths for fluid circulation through the slab and can be identify as vulnerability zones for exterior applications. Experimental procedure included several laboratory analyses in order to study clays and the iron oxide contents. Microscopic petrography, XRD and SEM observations were important to identify the interaction of the clay material in stylolites and fossil contours. Results show the importance of establishing standard methods for selecting stone on cladding applications. From the results, it is possible to understand that clay minerals have a strong influence on the mechanical performance of this stone. Among other important remarks, results show the importance of the development of standard procedures that acknowledge the structure and mineral composition before setting these natural products as construction materials. Proper stone selection was found important to avoid facade degradation, and hence contribute to prevent accidents and promote user safety as well as economic impacts.

scholarly journals Mortars with CDW Recycled Aggregates Submitted to High Levels of CO2

2021 ◽  
Vol 6 (11) ◽  
pp. 159
Author(s):  
Ricardo Infante Gomes ◽  
David Bastos ◽  
Catarina Brazão Farinha ◽  
Cinthia Maia Pederneiras ◽  
Rosário Veiga ◽  
...  
Keyword(s):  
Large Scale ◽  
Mechanical Performance ◽  
Construction Materials ◽  
Environmental Benefits ◽  
Recycled Aggregates ◽  
Construction And Demolition Wastes ◽  
Short Period ◽  
Natural Aggregates ◽  
Cement Factories ◽  
Made In

Construction and demolition wastes (CDW) are generated at a large scale and have a diversified potential in the construction sector. The replacement of natural aggregates (NA) with CDW recycled aggregates (RA) in construction materials, such as mortars, has several environmental benefits, such as the reduction in the natural resources used in these products and simultaneous prevention of waste landfill. Complementarily, CDW have the potential to capture CO2 since some of their components may carbonate, which also contributes to a decrease in global warming potential. The main objective of this research is to evaluate the influence of the exposure of CDW RA to CO2 produced in cement factories and its effect on mortars. Several mortars were developed with a volumetric ratio of 1:4 (cement: aggregate), with NA (reference mortar), CDW RA and CDW RA exposed to high levels of CO2 (CRA). The two types of waste aggregate were incorporated, replacing NA at 50% and 100% (in volume). The mortars with NA and non-carbonated RA and CRA from CDW were analysed, accounting for their performance in the fresh and hardened states in terms of workability, mechanical behaviour and water absorption by capillarity. It was concluded that mortars with CDW (both CRA and non-carbonated RA) generally present a good performance for non-structural purposes, although they suffer a moderate decrease in mechanical performance when NA is replaced with RA. Additionally, small improvements were found in the performance of the aggregates and mortars with CRA subjected to a CO2 curing for a short period (5 h), while a long carbonation period (5 d) led to a decrease in performance, contrary to the results obtained in the literature that indicate a significant increase in such characteristics. This difference could be because the literature focused on made-in-laboratory CDW aggregates, while, in this research, the wastes came from real demolition activities, and were thus older and more heterogeneous.

State of the art on geopolymer concrete

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Zoi G. Ralli ◽  
Stavroula J. Pantazopoulou
Keyword(s):  
Mechanical Performance ◽  
State Of The Art ◽  
Construction Materials ◽  
Cementitious Materials ◽  
Sustainable Construction ◽  
Geopolymer Concrete ◽  
Critical Material ◽  
Content Type ◽  
Critical Requirement

PurposeImportant differentiating attributes in the procedures used, the characteristic mineral composition of the binders, and the implications these have on the final long term stability and physico-mechanical performance of the concretes produced are identified and discussed, with the intent to improve transparency and clarity in the field of geopolymer concrete technologies.Design/methodology/approachThis state-of-the-art review covers the area of geopolymer concrete, a class of sustainable construction materials that use a variety of alternative powders in lieu of cement for composing concrete, most being a combination of industrial by-products and natural resources rich in specific required minerals. It explores extensively the available essential materials for geopolymer concrete and provides a deeper understanding of its underlying chemical mechanisms.FindingsThis is a state-of-the-art review introducing the essential characteristics of alternative powders used in geopolymer binders and the effectiveness these have on material performance.Practical implicationsWith the increase of need for alternative cementitious materials, identifying and understanding the critical material components and the effect they may have on the performance of the resulting mixes in fresh as well as hardened state become a critical requirement to for short- and long-term quality control (e.g. flash setting, efflorescence, etc.).Originality/valueThe topic explored is significant in the field of sustainable concrete technologies where there are several parallel but distinct material technologies being developed, such as geopolymer concrete and alkali-activated concrete. Behavioral aspects and results are not directly transferable between the two fields of cementitious materials development, and these differences are explored and detailed in the present study.

Durability of a ventilated stone facade: A case study of a limestone facade affected by the corrosion of the anchorage system

2020 ◽  
Author(s):  
Vera Pires de Almeida Ribeiro
Keyword(s):  
Chemical Characterization ◽  
Masonry Walls ◽  
Concrete Walls ◽  
Reinforced Concrete Walls ◽  
Correct Execution ◽  
Anchoring System ◽  
Ventilated Facade ◽  
Non Destructive

<p>The mechanical behavior of a natural stone ventilated facade is inevitably based on the correct execution of both anchoring elements, stone cladding and enclosure support, either with brick masonry walls or reinforced concrete walls. In the case studied in the present work, the origin of the damages on the facade of a building located in Lisbon has been analyzed, where stone detachments were starting to occur. This enclosure is a ventilated facade cladded with Portuguese limestone Lioz slabs. Non-destructive borescope analysis of the metallic anchoring system employed was performed, as well as X-Ray fluorescence laboratory analysis (FRX) for chemical characterization of the anchoring material. Results obtained demonstrated the problem cause on the stone facade due to incorrect metallic anchoring selection and poor execution combined with stress corrosion effect, especially for slabs with larger dimensions.</p>

Reinforcement Mechanism of Cement/Lime-Fly Ash Treated Sediments as Road Construction Materials

2011 ◽  
Vol 99-100 ◽  
pp. 924-927 ◽  
Author(s):  
Dong Xing Wang ◽  
Hong Xing Wang ◽  
Wen Zhao Chen
Keyword(s):  
Fly Ash ◽  
Mechanical Performance ◽  
Construction Materials ◽  
Road Construction ◽  
Strength Test ◽  
Point Of View ◽  
Environment Friendly ◽  
Reinforcement Mechanism ◽  
Dredged Materials ◽  
Compressive Strength Test

Solidified dredged materials as environment-friendly materials in construction domain are increasingly popular because of their better mechanical performance and low pollution. Based on the physical characteristic of dredged marine sediments, a series of tests, such as unconfined compressive strength test and tensile strength test, were performed to explore the mechanical properties of cement/lime-fly ash treated sediments for the beneficial use in road construction. Finally, the reinforcement mechanism of solidified sediments was explored by SEM tests from the point of view of the formation of CSH phases and the change in microstructure.

A Review of the Utilisation of Recycled Waste Material as an Alternative Modifier in Asphalt Mixtures

2020 ◽  
Vol 6 ◽  
pp. 42-60
Author(s):  
Abdalrhman Abrahim Milad ◽  
Ahmed Suliman B. Ali ◽  
Nur Izzi Md Yusoff
Keyword(s):  
Mechanical Performance ◽  
Permanent Deformation ◽  
Steel Slag ◽  
Asphalt Mixture ◽  
Construction Materials ◽  
Crumb Rubber ◽  
Asphalt Mixtures ◽  
Waste Material ◽  
Waste Materials ◽  
The Road

The possibility of using waste materials in road construction is of great interest as their utilisation may contribute to reducing the problems of hazard and pollution and conserve natural resources. Thus, there is an urgent need to find a sustainable method for using waste materials as a substitute in the standard asphalt binders. There are several concerns about the physical and chemical properties and mechanical performance of asphalt pavements incorporated with waste material in the effort to reduce permanent deformation of the road surface. This review article presents a brief discussion of the asphalt mixtures modified with waste material, and the recycled materials used as a modifier in the asphalt mixture. The present paper summarises the use of crumb rubber, crushed concrete, steel slag, glass fibre and plastic waste in asphalt mixtures. The use of waste materials as a modifier in asphalt mixture resulted in improved asphalt pavement performance. Results advocate that rubberised asphalt mixture with desired properties can be designed as an additive with a friendly environmental approach in construction materials. The researches that adopted the influence of usage, recycle waste material to improve the performance of the asphalt of the road are still limited compared to other construction fields. Doi: 10.28991/cej-2020-SP(EMCE)-05 Full Text: PDF

scholarly journals Investigation on the Combined Effect of Fibers and Cement on the Mechanical Performance of Foamed Bitumen Mixtures Containing 100% RAP

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Ehsan Ashouri Taziani ◽  
Emanuele Toraldo ◽  
Filippo Giustozzi ◽  
Maurizio Crispino
Keyword(s):  
Research Study ◽  
Mechanical Performance ◽  
Asphalt Pavement ◽  
Construction Materials ◽  
Recycled Asphalt ◽  
New Methods ◽  
Dynamic Creep ◽  
Indirect Tensile ◽  
The Common ◽  
Foamed Bitumen

Concerns about virgin aggregate sources and increasing demands for construction materials of transport infrastructures as the key parameters in development are the most important reasons, which convinced pavement engineers to develop new methods in order to use higher amount of recycled asphalt pavement (RAP). One of the common methodologies to produce mixtures containing RAP is foamed bitumen mix (FBM). In addition, according to previous research studies, incorporating various types of fibers and hydraulic binders such as cement could significantly improve the mechanical performance of mixtures. The present research study evaluated FBM containing 100% RAP and two types of fiber and Portland cement. Dynamic modulus, unconfined dynamic creep compression, and indirect tensile strength were evaluated in the laboratory at optimum moisture content, which was investigated in this research. Both types of fiber and cement proved to enhance specific properties of mixtures.

Test on Corrosion Resistance of GFRP Anchor Bolt

2012 ◽  
Vol 535-537 ◽  
pp. 1927-1935 ◽  
Author(s):  
Xiao Yong Luo ◽  
Xie Xing Tang ◽  
Kai Lei Li ◽  
Ya Chuan Kuang
Keyword(s):  
Tensile Strength ◽  
Elastic Modulus ◽  
Loss Rate ◽  
Mechanical Performance ◽  
Effective Means ◽  
Anchor Bolt ◽  
Geological Conditions ◽  
Anchoring System ◽  
Anchor Bolts ◽  
Corrosion Time

Steel is commonly used as the materials of anchor bolts in permanent anchoring works. The nature the steel anchor bolt easy to be corroded, however, poses a serious potential safety hazard to the anchoring system mainly including steel anchor bolts. To use GFRP(glass fiber reinforced polymer) anchor bolts instead of reinforcing bars is an effective means to deal with corrosion. Based on the test of accelerating aging in high solubility, the physical and mechanical performance tests are conducted on GFRP bolts in normal, acid, alkalis and salt conditions, from which the change law of physical and mechanical property can be studied for bolts in different corrosion conditions. As shown from the test results, the weight of GFRP bolt is reduced after it is corroded and the rate of weight loss increases as the corrosion time extends. Thick swelling can be seen on bolts in alkalis conditions. Loss rate of tensile strength and increase rate of elastic modulus are greater in alkalis conditions than in acid conditions, the former reaching 13.76% and the latter 9.83%. As for bolts in acid conditions, tensile strength decreases as the corrosion time extends while the rate and amount of loss is less than that of bolts in acid and alkalis conditions. The tensile strength decreases as the solubility of corrosion solution increases. The loss rate of tensile strength is the most for bolts in alkalis conditions; it comes second in acid conditions and the least in salt conditions. The elastic modulus of bolts in acid conditions and alkalis conditions increases while the rate is comparatively low as the solubility gets higher. Elastic modulus of bolts in salt conditions decreases as the solubility rises with lower rate and smaller amount of loss. These results supply test foundation for application of GFRP bolts in complicated geological conditions.

scholarly journals Effect of Natural Graphite Fineness on the Performance and Electrical Conductivity of Cement Paste Mixes for Self-Sensing Structures

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5833
Author(s):  
Ioanna Papanikolaou ◽  
Chrysoula Litina ◽  
Amir Zomorodian ◽  
Abir Al-Tabbaa
Keyword(s):  
Electrical Conductivity ◽  
Cement Paste ◽  
Mechanical Performance ◽  
Low Cost ◽  
Construction Materials ◽  
Natural Graphite ◽  
Cement Pastes ◽  
Conductive Additive ◽  
Frequent Monitoring ◽  
Wide Availability

Cementitious composites are the most widely used construction materials; however, their poor durability necessitates frequent monitoring and repairs. The emergence of self-sensing composites could reduce the need for costly and time-consuming structural inspections. Natural graphite, due to its low cost and wide availability, is a promising additive to generate an electrically conductive network which could ultimately lead to a self-sensing mechanism. Despite several studies using natural graphite as a conductive additive, the effect of its fineness on the cementitious composite’s performance has not been explored. This study experimentally investigated the effect of three graphite products of varying fineness on the early age, mechanical, and electrical conductivity performance of cement pastes. The fluidity of the graphite-cement paste reduced significantly with increasing graphite fineness, and graphite did not affect the cement hydration. The finer the graphite, the lower the effect on the mechanical performance, as confirmed by compressive strength testing and micro-indentation. Electrical conductivity testing showed that the percolation threshold depended on the graphite fineness and was found at ~20 wt % for the fine and medium graphite, while it increased to 30–40 wt % for the coarse graphite. This is the first study that has investigated holistically the effect of graphite fineness on the performance of cement pastes and will pave the way for using this material as an additive for self-sensing structures.

scholarly journals Durability of Textile Reinforced Concrete: Existing Knowledge and Current Gaps

2021 ◽  
Vol 11 (6) ◽  
pp. 2771
Author(s):  
Mohammad Alma’aitah ◽  
Bahman Ghiassi ◽  
Ali Dalalbashi
Keyword(s):  
Reinforced Concrete ◽  
Mechanical Performance ◽  
Mechanical Tests ◽  
Textile Reinforced Concrete ◽  
Standard Procedures ◽  
Long Term Performance ◽  
Term Performance ◽  
Existing Data

This paper aims to provide a review of the current literature on the durability of textile-reinforced concrete and mortar (TRC/TRM) composites. Most previous studies have focused on the role of chemical attacks, freeze-thaw conditions, and high temperatures on the mechanical performance of these composites. Information on the long-term performance of TRCs under synergistic action of mechanical and environmental loads is scarce. Considering the variety of fabrics and matrices used for the production of TRC composites, the existing data are still very limited and comprehensive studies are needed in this field. Additionally, due to the lack of standard procedures, different approaches are often followed for durability or post-ageing mechanical tests, or sufficient data on the curing and post-ageing preparation procedures followed are not provided. These have led to incompatibility of the existing data and in some cases contradictory results on the durability of these materials.

scholarly journals Potentialities in the performance of coating mortars through the addition of sewage sludge ash

2021 ◽  
Vol 10 (6) ◽  
pp. e25910615736
Author(s):  
João Victor da Cunha Oliveira ◽  
Leila Soares Viegas Barreto Chagas ◽  
Frankslale Fabian Diniz de Andrade Meira ◽  
Arnaldo Manoel Pereira Carneiro
Keyword(s):  
Sewage Sludge ◽  
Mechanical Performance ◽  
Sewage Treatment ◽  
Construction Materials ◽  
Degradation Process ◽  
Cementitious Materials ◽  
Human Beings ◽  
Industrial Sectors ◽  
Thermal Degradation Process ◽  
Sludge Ash

Through environmental policies that provide a gradual discussion about the destination of the tailings produced in the most diverse industrial sectors, the sewage sludge is emphasized by the problematic destination arising from the amount of toxic compounds that compose it, compromising its disposal. Aiming to fulfill the sustainable role through the creation of mechanisms that favor the ecological coexistence between environment and human beings, it is possible through the use of construction materials, considered as conventional, the use of calcined sewage sludge as an enhancer of the properties of matrix materials cement, significantly improving its performance against mechanical stresses and degradation mechanisms. Based on the need to implement measures to mitigate environmental impacts through the production of eco-efficient materials, the ashes of sanitary sewage sludge as a partial substitute for Portland cement have now been used as an input in coating mortars. This substitution focuses on reducing the large volume of sludge generated by the Sewage Treatment Plants, as well as on the reduction in the consumption of cement, a large CO2 generator during its manufacturing process. It was observed that through the use of this calcined by-product applied in mortars, a relevant physical-mechanical performance in cementitious materials is ratified, that in comparison to the material without the use of it, better results are observed, resulting from the reactivity conferred to the sludge after the thermal degradation process, making it a pozzolana.

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