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The durability of concrete under combined acidic exposure and flexural loading was studied. Concrete specimens were made and subjected to up to 168 days of exposure to flexural loading (stress levels of 0, 0.35 and 0.50 of the 28 day flexural strength) and an acidic environment. Concrete properties such as neutralisation depth, mass change, compressive strength and flexural strength were measured. The compositions of different samples were determined by means of X-ray diffraction and chemical analysis and the microstructure of samples was examined using scanning electron microscopy. The results showed that, with an increase in stress level from 0 to 0.50, the performance of the concrete deteriorated gradually and the deterioration in the tension zone was greater than that in the compression zone. The concrete performance improved within 28 days but deteriorated dramatically afterwards. The acidic solution reacted with the cement paste, leading to the formation of harmful gypsum and the decomposition and dissolution of cement hydration products. An increase in stress level increased the porosity of the concrete, accelerating the rate of acid erosion, which led to a deterioration of concrete performance. [ABSTRACT FROM AUTHOR]

Magnesium phosphate cements (MPCs), also known as chemically bonded ceramics, represent a class of inorganic cements that have garnered considerable interest in recent years for their exceptional properties and diverse applications in the construction and engineering sectors. However, the development of these cements is relatively recent (they emerged at the beginning of the 20th century), so there are still certain aspects relating to their durability that need to be evaluated. The present work analyses the chemical durability of magnesium potassium phosphate cements (MKPCs) during 1 year of immersion in three leaching media: seawater, a Na2SO4 solution (4% by mass) and deionized water. For this, pastes of prismatic specimens of MKPC, prepared with different M/P ratio (2 and 3), were submitted to the different chemical attacks. At different ages, the changes on the mechanical strengths, microstructure (BSEM, MIP) and mineralogy (XRD, FTIR, TG/DTG) were evaluated. The results obtained indicate that, in general terms, MKPC systems show good behavior in the three media, with the more resistant system being the one prepared with a M/P molar ratio of 3. [ABSTRACT FROM AUTHOR]

This review focuses on recent advances in concrete durability using graphene oxide (GO) as a nanomaterial additive, with a goal to fill the gap between concrete technology, chemical interactions, and concrete durability, whilst providing insights for the adaptation of GO as an additive in concrete construction. An overview of concrete durability applications, key durability failure mechanisms of concrete, transportation mechanisms, chemical reactions involved in compromising durability, and the chemical alterations within a concrete system are discussed to understand how they impact the overall durability of concrete. The existing literature on the durability and chemical resistance of GO-reinforced concrete and mortar was reviewed and summarized. The impacts of nano-additives on the durability of concrete and its mechanisms are thoroughly discussed, particularly focusing on GO as the primary nanomaterial and its impact on durability. Finally, research gaps, future recommendations, and challenges related to the durability of mass-scale GO applications are presented. [ABSTRACT FROM AUTHOR]

Inferior quality of concrete surface layers can lead to significant deterioration of concrete infrastructure due to the infiltration of fluids and deleterious substances from the surrounding environment. Concrete structures such as foundations, abutments, flatwork, and underground tanks in agricultural and mining zones, as well as slabs in factories producing ammonium-based fertilizers, are highly susceptible to ammonium sulfate attack, which is known as the most aggressive sulfate deterioration driven by acid-sulfate reactions. Coatings are an effective strategy for protecting such concrete structures to restore its performance and prolong its service life. Therefore, this study aimed at investigating the performance of nano-based coatings as superficial treatments for concrete elements exposed to aggravated exposures of ammonium sulfate. Silane (hydrophobic agent) and vinyl ester (membrane-forming polymer) were used as base resins, in which nano-clay and nano-calcium carbonate particulates were dispersed at different dosages (0, 2.5, and 5 %). In addition, a colloidal silica solution was used as a surface treatment. The durability of coated concrete specimens was evaluated under two ammonium sulfate exposures: full immersion and combined with cyclic environmental conditions (freezing-thawing and wetting-drying cycles). Degradation of concrete specimens was monitored by visual assessment and quantified in terms of mass and length changes over time. In addition, the deterioration mechanisms and coatings’ performance were studied by thermal, mineralogical, and microstructural tests. The results showed that colloidal silica could not adequately protect concrete specimens from these exposures. Conversely, silane nanocomposites improved the durability of concrete under both exposures and superior performance was generally observed for concrete specimens coated with vinyl ester nanocomposites.

This study investigates the chemical resistance of cement paste by incorporating liquid-crystal display (LCD) glass powder as a partial replacement for cement. The samples, cured under water and carbonation, were subjected to adverse chemical attacks over a period of up to 90 days, using MgSO4 and H2SO4 for the sulphate attack and acid attack, respectively. The results demonstrate a decrease in compressive strength by upto 14.63% and 32.32% for water- and carbonation-cured samples, respectively, and an increase in carbonation degree by upto 100% with the incorporation of glass powder at 28 days. Under sulphate attack, water curing and carbonation curing displayed strength increase of 21.24–36.13% and 7.56–8.06%, respectively, at 90 days. However, carbonation-cured samples experienced greater leaching of silica and calcium. The compressive strength decreased with acid attack duration, with glass powder incorporation mitigating strength loss in carbonation-cured samples. At 30 days, with an incorporation rate of 30% glass powder, the strength loss was reduced by 37.66% for the carbonation-cured samples. The enhanced resistance with incorporation of glass powder was also evident from mercury intrusion porosimetry results that indicated decreased intrusion levels. Visual inspection revealed a different consistency of white substance deposition, suggesting resistance mechanisms differed between curing methods.

The durability of concrete is critical for the service life of concrete structures, and it is influenced by various factors. This paper investigates the impact of the relative humidity (RH) of the curing environment on the durability of five different concrete types. The aim is to determine a suitable approach for designing concrete that is well-suited for use in the salt lake region of Inner Mongolia. The concrete types comprise ordinary Portland cement (OPC), high-strength expansive concrete (HSEC), high-strength expansive concrete incorporating silica fume, fly ash, and blast furnace slag (HSEC-SFB), steel fiber-reinforced high-strength expansive concrete (SFRHSEC), and high elastic modulus polyethylene fiber-reinforced high-strength expansive concrete (HFRHSEC). All these concrete types underwent a 180-day curing process at three distinct relative humidities (RH = 30%, 50%, and 95%) before being subjected to freeze–thaw cycles in the Inner Mongolia salt lake brine. The curing environment with a 95% RH is referred to as the standard condition. The experimental results reveal that the durability of OPC and HSEC decreases significantly with increasing relative humidity. In comparison with the control sample cured in 95% RH, the maximum freeze–thaw cycles for concrete cured in lower RHs are only 31% to 76% for OPC and 66% to 77% for HSEC. However, the sensitivity of the durability of HSEC-SFB, SFRHSEC, and HFRHSEC to variations in RH in the curing environment diminishes. In comparison with the corresponding reference value, the maximum freeze–thaw cycles for samples cured in dry conditions increase by 14% to 17% for HSEC-SFB and 21% for SFRHSEC. Specifically, the service life of HFRHSEC cured in a low RH is 25% to 46% higher than the reference value. The durability of HSEC-SFB, SFRHSEC, and HFRHSEC has been proven to be appropriate for structures located in the salt lake region of Inner Mongolia. [ABSTRACT FROM AUTHOR]

Due to their potential to lower CO2 emissions linked with the cement and concrete industries, geopolymer binders are a desirable alternative for Portland cement binders. However, if they are to become a viable alternative to conventional Portland cement materials, their resilience in harsh conditions has to be further investigated. This paper presented mechanical and short-term durability properties of metakaolin based geopolymer concrete at sulphuric acid (H2SO4) solutions exposed with the concentrations of 2%, 3%, 4% and 5% for 14 days. (0%) or unexposed sample also prepared as referral and comparison. The geopolymer concretes were synthesized using an alkali activation of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). The main objective of the study was to examine the durability and deterioration mechanism parameters like different acid percentages, changes in weight, compressive strength, density and water absorption. Morphology analysis also performed in this study. The results indicated that metakaolin geopolymer experienced some strength deterioration with increasing sulphuric concentration solutions which are from 32.58 MPa, 20.67 MPa and 4.25 MPa at unexposed (0%), 2% and 5% sulphuric acid immersion respectively. Furthermore, change in weight or mass loss and water absorption after the chemical attack resulted directly proportional to sulphuric acid concentration due to increment of crack on the sample. Among that, the metakaolin geopolymer submerged in 2% acid gives the optimum results in terms of durability, mechanical and physical qualities.

This work evaluates the resistance to chemical attack and thermal shock of porcelain formulated from local raw materials from Burkina Faso for their validation in real use. A kaolinitic clay, a pegmatite and sand were used for the formulation of porcelain tiles. Some samples were shaped by casting into porous molds and sintered at a temperature of 1240 °C. The average heating rate is 10 °C/min up to the final given temperature. These porcelains were immersed to a depth of 25 mm in test solutions and kept closed at 20 °C for 12 days. Six concentrations of test solutions were prepared to perform these tests: ammonium chloride (100 g/L); hydrochloric acid (3% and 18% by volume); lactic acid (5% by volume); citric acid (100 g/L) and alkali KOH (30 g/L and 100 g/L). The test showed that these porcelains are resistant to chemical attacks with insignificant mass variations ranging from −0.030 to 0.053 wt%. The results of the thermal shock test show that formulated porcelains are resistant to the brutal variation of temperature. The results obtained qualify the porcelains for industrial and real use.

Timber has been a prominent construction material for construction from the beginning of human civilization. The research aims at investigating the mechanical properties and durability (against chemical attack) of locally sourced wood species to be used in the construction industry. Authentication test of species, specific gravity, durability, compressive strength, bending strength, tensile strength and shear strength tests were conducted for locally available timber species. From the 34 species investigated, 24 species were observed to have viable properties to be used as softwood and hardwood timber in construction. After being exposed to sulfuric testing, compressive strength results (parallel to grain) of Pihibiya (Filicium decipiens) and Muttikadol (Xylocarpus granatum) were only reduced by 4.3% and 1.6%, respectively. This is evidence of the two species having strong chemical resistivity. Bala, Katta Kumanjal, Muttikadol, Wal Jambu, Karambu, Malkaralla and Thammanna were identified as underutilized timber species in the local context, having bending strengths over 25 N/mm2. Overall, this research is important for the international society as it contributes to sustainable resource management, economic development, environmental conservation, standardization, and knowledge exchange.

Due to their potential to lower CO2 emissions linked with the cement and concrete industries, geopolymer binders are a desirable alternative for Portland cement binders. However, if they are to become a viable alternative to conventional Portland cement materials, their resilience in harsh conditions has to be further investigated. This paper presented mechanical and short-term durability properties of metakaolin based geopolymer concrete at sulphuric acid (H2SO4) solutions exposed with the concentrations of 2%, 3%, 4% and 5% for 14 days. (0%) or unexposed sample also prepared as referral and comparison. The geopolymer concretes were synthesized using an alkali activation of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). The main objective of the study was to examine the durability and deterioration mechanism parameters like different acid percentages, changes in weight, compressive strength, density and water absorption. Morphology analysis also performed in this study. The results indicated that metakaolin geopolymer experienced some strength deterioration with increasing sulphuric concentration solutions which are from 32.58 MPa, 20.67 MPa and 4.25 MPa at unexposed (0%), 2% and 5% sulphuric acid immersion respectively. Furthermore, change in weight or mass loss and water absorption after the chemical attack resulted directly proportional to sulphuric acid concentration due to increment of crack on the sample. Among that, the metakaolin geopolymer submerged in 2% acid gives the optimum results in terms of durability, mechanical and physical qualities. [ABSTRACT FROM AUTHOR]

The objective of this study is to evaluate the effect of pozzolan on the durability of high-performance fiber concretes in two aggressive environments. For this, prismatic test pieces were made at (0%, 10%, 20%, and 40%) of pozzolan and immersed in two acids, hydrochloric and sulfuric. Then characterizations were carried out, such as the loss of mass, the depth of degradation and the mechanical resistance. The results obtained show that with the substitution rate of pozzolan, the loss of mass and the depth of degradation increase in the two acids, while the mechanical strength increases in hydrochloric acid and decreases in sulfuric acid.

The effect of sulfate attack (SA) on the strength of ultrahigh-performance concrete (UHPC) made with different replacements (0%, 50% and 100% by weight) of natural fine aggregate with recycled fine aggregate (RFA) was investigated. The UHPC samples were soaked in 10% sodium sulfate solution for 0–180 days (SA duration). The sulfate ion concentration, flexural strength and compressive strength of the UHPCs were investigated. The microstructure of the UHPCs before and after SA was analysed using a multi-technique approach (analysis of interfacial transition zones (ITZs), X-ray diffraction, scanning electron microscopy–energy-dispersive X-ray spectroscopy and mercury intrusion porosimetry). The results showed that, with an increase in SA duration, the compressive strength of the UHPC made with RFA increased. The generated gypsum and ettringite refined the microstructure by converting harmful pores (>20 nm) into harmless pores (<20 nm) in the UHPC matrix. For the same SA duration, the sulfate ion concentration of UHPC increased with an increase in RFA content due to more ITZs, pores and microcracks introduced by the RFA. Strength development models for UHPC with different RFA contents under SA were developed. [ABSTRACT FROM AUTHOR]

The interaction between the dielectric BaTiO3/poly(vinyl butyral) composite layer (BT@PVB sheet) and the metallic Ni/ethyl cellulose composite layer (Ni@EC sheet) in developing MLCC has been considered an inevitable factor. In this paper, we devised Ni/polymer composite solution (Ni@EC paste) with new concept, which does not damage the dielectric composite layer underneath due to its lack of interaction with the BT@PVB sheet, and introduced emulsified-state suspension as a systematic template. Emulsified Ni@EC paste consists largely of hydrophobic phases, water phases, and PVB surfactants. The components that make up the hydrophobic phase were Ni nanoparticles, EC binders, and organic solvents. Within the emulsified paste (Ni@EC/water), the hydrophobic phase formed the structure of droplets surrounded by surrounding water, resulting in only the water phase being exposed to the outside. During the coating process, the water phase in Ni@EC/water emulsion paste came into contact with the as-prepared BT@PVB sheet, and the hydrophobic phase could not affect the sheet due to the blocking effect of the surrounding water phase. Afterwards, organic solvents as well as water were co-evaporated through the drying process, and most of the organic solvents were removed and solidified before molecular diffusion into BT@PVB sheet occurred. [ABSTRACT FROM AUTHOR]

3D concrete printing represents a modern trend in construction automation, characterized by the layer-by-layer deposition of concrete using 3D printers to construct structures without traditional formwork. This process alters the rheological behavior, microstructure, mechanical properties, and durability of 3D-printed concrete compared to conventional cast concrete. This review outlines the porosity and durability tests conducted in previous research papers. It presents the details and procedures of these tests, along with any referenced standards or guidelines. By comparing printed specimens to cast specimens, both similar and controversial results from the tests are also comprehensively discussed. It becomes evident that the durability properties of printed specimens differ from those of cast specimens due to their distinct pore systems. Ultimately, this review aims to bridge research gaps in 3DPC durability performance and assist in the selection of methodologies for porosity and durability tests. • Tabulation of conducted porosity and durability tests for 3D printed concrete. • Comparison of pore structure between 3D printed and cast specimens. • Comparative analysis of durability aspects between 3D printed and cast concrete. • Recommended test methods for porosity/permeability and durability tests. • Durability of 3D printed concrete is highly related to its pore system. [ABSTRACT FROM AUTHOR]

This study examines the suitability of alternate binders and crumb rubber (CR) to produce light weight alkali‐activated concrete (AAC). For this, strength, and durability performance of AAC incorporating CR by partially replacing fine aggregate was studied. To produce AAC, four different binders, including fly ash, rice husk ash (RHA), metakaolin, and bottom ash were used. Fine aggregates were substituted with CR at 0%, 10%, 20%, and 30% for each AAC mix (with different binders). Furthermore, the mixes were prepared using 12 M sodium hydroxide (NaOH) solution, and the ratio of sodium silicate (Na2SiO3) to NaOH was taken as 2.5. The samples were cured at ambient temperature. Strength and durability properties, including permeability through water absorption and acid attack (hydrochloric acid [HCl] and sulfuric acid [H2SO4]), were also checked. Results of this study revealed that the strength decreased with the increase in CR content. Further, this decrease was high at 30% replacement but strength was satisfactory. AAC showed good relationships among compressive, flexural, and split tensile strengths. Similar footprints were observed for permeability results. However, highest water absorption was observed for bottom ash binder (with 30% substitution of CR). Mixes with fly ash and metakaolin binders outperformed the other mixes while comparing the compressive strength of acid exposed samples. Overall, a sustainable and durable light weight AAC can be prepared using 20% CR. [ABSTRACT FROM AUTHOR]

Concrete, an integral part of a nuclear power plant (NPP), experiences degradation during their operational lifetime of the plant. In this review, the major causes of concrete degradation are extensively discussed including mechanisms that are specific to NPPs. The damage mechanism could be chemical or physical. The major causes of chemical degradation include alkali–aggregate reactions, leaching, sulfate attack, bases and acids attack, and carbonation. Physical degradation is a consequence of both environmental and mechanical factors combined. These factors are mainly elevated temperature, radiation, abrasion and erosion, salt crystallization, freeze–thaw distortions, fatigue and vibration. Additionally, steel reinforcements, prestressing steels, liner plates, and structural steel also experience degradation. The prospective areas in the structural components of the NPP where the degradation could occur are mentioned and the effective solutions to the causes of degradation are highlighted. These solutions are designed to enhance the physical and chemical characteristics of concrete. Some of the major recommendations include addition of mineral substitutes, use of low water-to-cement ratio as well as low water-to-binder ratio, use of low alkali cement, use of special aggregates and fibers, use of corrosion inhibitors, use of cathodic protection, etc. The review concludes with an overview of present methods and possible recommendations used to enhance the quality of concrete towards preventing concrete degradation and increasing the lifetime of NPPs. [ABSTRACT FROM AUTHOR]

Heavy charged particles induce severe damage in DNA, which is a radiobiological advantage when treating radioresistant tumors. However, these particles can also induce cancer in humans exposed to them, such as astronauts in space missions. This damage can be directly induced by the radiation or indirectly by the attack of free radicals mainly produced by water radiolysis. We previously studied the impact of a proton on a DNA base pair, using the Time Dependent-Density Functional Theory (TD-DFT). In this work, we go a step further and study the attack of the OH· radical on the Guanine nucleotide to unveil how this molecule subsequently dissociates. The OH· attack on the H1′, H2′, H3′, and H5′ atoms in the guanine was investigated using the Ehrenfest dynamics within the TD-DFT framework. In all cases, the hydrogen abstraction succeeded, and the subsequent base pair dissociation was observed. The DNA dissociates in three major fragments: the phosphate group, the deoxyribose sugar, and the nitrogenous base, with slight differences, no matter which hydrogen atom was attacked. Hydrogen abstraction occurs at about 6 fs, and the nucleotide dissociation at about 100 fs, which agrees with our previous result for the direct proton impact on the DNA. These calculations may be a reference for adjusting reactive force fields so that more complex DNA structures can be studied using classical molecular dynamics, including both direct and indirect DNA damage. [ABSTRACT FROM AUTHOR]

Generation of solid waste materials from various industrial sources is becoming a challenging issue for safe disposal. Durability performance of hydraulic structures under environmental loadings (aggressive substances) is also a concerning issue. The present paper investigated the durability performance of engineered cementitious composite (ECC) mortar containing stone slurry powder (SSP). SSP was used as partial subrogation of micro silica sand (MSS) and fine sand (FS) by 25% and 50% for each type of sand. Electrical resistivity (ER) and compressive and tensile behavior of various mixes were studied experimentally under chloride, sulphate, and chloride-sulphate combined environmental conditions. Results obtained from various properties revealed that performance of fully MSS and FS containing ECC mixes was affected under aggressive substances at initial stages. The observations demonstrate that ECC containing SSP was durable and maintains better mechanical performance over fully MSS and FS containing mixes. This improvement finds a place in construction of hydraulic structures under aggressive environments. [ABSTRACT FROM AUTHOR]

In the past, researchers focused mainly on the potential use of recycled rubber tyres, in the form of aggregates in construction materials. This process provided a viable environmentally friendly solution for the disposal of waste tyres. These days, the use of different shapes and sizes of rubber aggregates in rubberised self-compacting concrete requires extensive durability checks. In this study, work has been carried out on a new self-compacting sand concrete incorporated with rubber aggregates in three different forms and sizes. The sustainability qualification requires the determination of some specific durability indicators such as the resistance to chemical attacks. It was observed that the presence of rubber aggregates reduced the penetration of ions from acid solutions into the concrete matrix. All the studied characteristics were completed by microscopic analysis of adhesion of different rubber aggregates in the cement matrix. SEM analyses showed clear differences in the homogeneity of the rubber particles in the concrete material. [ABSTRACT FROM AUTHOR]

Introduction: The survivability of mass casualties exposed to a chemical attack is dependent on clinical knowledge, evidence-based practice, as well as protection and decontamination capabilities. The aim of this systematic review was to identify the knowledge gaps that relate to an efficient extraction and care of mass casualties caused by exposure to chemicals.Methods: This systematic review was conducted from November 2018 through September 2020 in compliance with Cochrane guidelines. Five databases were used (MEDLINE, Web of Science Core Collection, Embase, Cochrane, and CINAHL) to retrieve studies describing interventions performed to treat victims of chemical attacks (protection, decontamination, and treatment). The outcomes were patient's health condition leading to his/her stabilization (primary) and death (secondary) due to interventions applied (medical, protection, and decontamination).Results: Of the 2,301 papers found through the search strategy, only four publications met the eligibility criteria. According to these studies, the confirmed chemical poisoning cases in acute settings resulting from the attacks in Matsumoto (1994), Tokyo (1995), and Damascus (2014) accounted for 1,333 casualties including 11 deaths. No study reported comprehensive prehospital clinical data in acute settings. No mention was made of the integration of specialized capabilities in medical interventions such as personal protective equipment (PPE) and decontamination to prevent a secondary exposure. Unfortunately, it was not possible to perform the planned meta-analysis.Conclusions: This study demonstrated gaps in clinical knowledge application regarding the medical extraction of casualties exposed during a chemical attack. Further research is required to optimize clinical practice integrating mixed capabilities (protection and decontamination) for the patient and medical staff. [ABSTRACT FROM AUTHOR]

Glass fiber reinforced cement (GRC) is an excellent composite for architects and engineers because it can be molded to produce laminar panels or to create complicated designs. GRC is a fine concrete reinforced with alkali-resistant glass fibers at 3–5% per mass. However, fiber durability is limited because of the aggressiveness of the alkaline medium produced during Portland cement hydration (effect of portlandite). The objective of this study is to assess GRC with high Portland cement replacement with pozzolans (ground fly ash or a mixture of ground fly ash and sonicated silica fume) in order to reduce the corrosion of the fibers. The selected high-content pozzolan (60% replacement) composites were tested under different conditions: aging, drying–wetting, freezing–thawing, and chemical attack (ammonium chloride and sulfuric acid). The modulus of rupture and toughness were determined. Composite behavior showed that the samples with pozzolans not only better resisted aging, but also physical and chemical attacks, and specimens presented a better modulus of rupture and toughness than the samples prepared with 100% Portland cement (control specimens). Due to the good behavior in durability terms, the high pozzolan content GRC products are suitable in potential corrosive environments for sunscreens, drainage channels, cable trays, sound barriers, or pavements. [ABSTRACT FROM AUTHOR]

This study investigates the performance of structural lightweight geopolymer concrete (SLWGC) exposed to chemical attack. The objective of this study is validation the ability of using light weight geopolymer concrete for structural purpose under hard conditions. The alkali activator was produced using sodium silicate, sodium hydroxide and water. Flay ash and slage as waste materials were replaced by 90% of ordinary Portland cement to produce the geopolymer concrete. Also, ordinary cement concrete produced to comparison. Three types of lightweight aggregate were used instead of normal aggregate represented by pumice stone, expanded clay and construction waste clay brick to produce SLWGC. The unit weight of produced SLWGC were in the range (1800–2100) kg/m3. Normal weight geopolymer concrete and SLWGC were produced simultaneously to compare their performance each with other. The geopolymer concrete mixes treated by heat curing at 65 °C for 24 h after removing the molds. The specimens of all mixes exposed to sulfuric acid with concentration 5% and 10% for 8 weeks. The investigated mechanical properties represented by compressive strength and flexural tensile strength. The results indicate that the geopolymer concrete exhibit better resistance for acid attack compared to OPC concrete where the strength deterioration for SLWGC lower than ORC light weight concrete after exposed to acid, crushed clay bricks exhibit superior mechanical and durability performance compared to other LWA. Finally, the results proved the ability of producing light weight geopolymer concert for structural purposed with acceptable performance of strength and durability under hard chemical conditions. [ABSTRACT FROM AUTHOR]

Structural failures in composite materials often occur due to problems in controlling interfacial interactions and the study to improve the interfacial adhesion between the reinforcement and matriz is of paramount importance for this class of materials. The objective of this work was to optimize the interfacial adhesion of the carbon fiber/epoxy composite, applying oxidative surface treatment with nitric acid in the reinforcement to compare with composites with the untreated fibers. Traction tests, pycnometry, energy dispersion X-ray spectroscopy and scanning electron microscopy were used to determine the properties and validate the treatment applied. The results obtained include superficial morphological changes in the carbon fibers, modifying the roughness and chemical composition. Both the 3K and 12K carbon fibers after treatment had an increase of 11% and 26% in the tensile strength and also in the modulus of elasticity of 6% and 16%, respectively. [ABSTRACT FROM AUTHOR]

Precise online identification of safe-zone evolution has been long desired in the context of indoor chemical attack events. Computational fluid dynamics (CFD) technology can provide great accuracy but is incapable of applying on online predictions of a large-scale fluid system due to the enormous computational costs to date. In this paper, we propose a Multi-Step Spatial-Temporal Situational-Awareness Network (MSSTP-SA Net) based on deep learning algorithms for rapid online estimation of concentration field. The dataset is firstly created by CFD simulation considering different poisonous gas release and decontamination scenarios in pre-specific domain with various combinations of airflow conditions and source parameters. Corresponding experiments are also provided for validations. The test experiments of the trained network suggest that the evolution of concentration field's distribution can be predicted faithfully in millisecond computation time costs. We hope this approach to be highly useful in most chemical attack scenarios to reduce casualties.

Concrete, an integral part of a nuclear power plant (NPP), experiences degradation during their operational lifetime of the plant. In this review, the major causes of concrete degradation are extensively discussed including mechanisms that are specific to NPPs. The damage mechanism could be chemical or physical. The major causes of chemical degradation include alkali–aggregate reactions, leaching, sulfate attack, bases and acids attack, and carbonation. Physical degradation is a consequence of both environmental and mechanical factors combined. These factors are mainly elevated temperature, radiation, abrasion and erosion, salt crystallization, freeze–thaw distortions, fatigue and vibration. Additionally, steel reinforcements, prestressing steels, liner plates, and structural steel also experience degradation. The prospective areas in the structural components of the NPP where the degradation could occur are mentioned and the effective solutions to the causes of degradation are highlighted. These solutions are designed to enhance the physical and chemical characteristics of concrete. Some of the major recommendations include addition of mineral substitutes, use of low water-to-cement ratio as well as low water-to-binder ratio, use of low alkali cement, use of special aggregates and fibers, use of corrosion inhibitors, use of cathodic protection, etc. The review concludes with an overview of present methods and possible recommendations used to enhance the quality of concrete towards preventing concrete degradation and increasing the lifetime of NPPs.

Biological corrosion is a type of effect that influences almost all possible construction projects. The primary measures for its prevention include sanitary and preventive work carried out using various chemicals. The shortcoming of buildings chemical treatment is the degradation effect on building composites with a significant reduction in the life of structures. The subject of the study was presented by the aggressive effect degree of sanitation treatment on various compositions of cement stone assessment. During the research Portland cement and aluminous cement, samples were exposed in two mediums – reagent solution (experimental medium) and tap water (control medium). The degree of medium influence on the cement stone samples was estimated according to the data on the main physic and chemical parameters of the process and phase-structural transformations of the stone after aging in an aggressive environment. There was an increase in the strength of samples after 6 months of exposure both for Portland cement stone and aluminous cement stone compared to the samples aged in pure water and original samples without exposure that showed the absence of the degradation effect of decontamination solution on the cement stone. The increase in the strength of materials occurred due to the intensification of carbonization processes in the sanitation agent medium resulting in the mud injection of pores and voids due to the crystallization of insoluble calcium carbonates. It was confirmed by the compaction of the micro-structure of cement stone expressed by the increase in the mass of samples and the total concentration of carbonate compounds in the volume of the material after 6 months of exposure.

Geopolymer-based materials have attracted increasing interest in construction and infrastructure engineering due to their high mechanical properties but low carbon dioxide emissions. However, it remains unclear whether this type of material can work in a stable way in harsh environments. This study investigated the chemical–physical–mechanical stability of metakaolin-based geopolymer (MKG) mortars under the immersing actions of sodium sulfate and magnesium sulfate solutions up to 180 days by testing their visual appearance, mass, dimensions, strength, microstructure and chemical components. Results show that the immersion actions do not cause obvious changes in mass, dimensions or compressive and flexural strengths of the MKG mortars. A white deposit, consisting of magnesium hydroxide, magnesium sulfate, magnesium carbonate and magnesium silicate aluminate hydrate, appeared on the surfaces of the high-alkali MKG specimens immersed in magnesium sulfate solution for 30 days, and disappeared at later ages due to the continual consumption of magnesium hydroxide. Mg–Na exchanges occurred for the MKG mortars immersed in magnesium sulfate solution. Overall, the chemical–physical–mechanical stability of geopolymer-based materials depends on the material components and interactions with the environment. Caution should be used before any engineering applications, and relevant issues deserve further rigorous investigation in the future. [ABSTRACT FROM AUTHOR]

Wick action is the key factor in understanding the salt weathering of porous materials. In this study, concrete discs were partially exposed to Na2SO4 solution to simulate the wick action in concrete. We evaluated the effects of the relative humidity (RH), solution concentration, and pore structures (different water to cement ratios) on the solution transport mechanism based on the water evaporation rate. Interestingly, we found that lower RH and larger W/C ratio accelerated evaporation, but the higher concentration of the solution slowed it down. The micro-analyzer results of NMR and XRD confirmed that the formation of ettringite and gypsum due to chemical sulfate attack blocked the pores in the concrete, resulting in a decrease in water evaporation. Na2SO4 crystallization distress was not detected in the concrete. Therefore, the solution transport process in the concrete discs could not be described by wick action. [ABSTRACT FROM AUTHOR]

Suitability of geopolymers for the use in an agricultural environment An exchange between research institutions and the construction industry is an important prerequisite for practice‐relevant research, which should not lack sufficient scientific depth. In this context, there has been a lively collaboration between HeidelbergCement AG and the Karlsruhe Institute of Technology (KIT) or the Materials Testing and Research Institute (MPA) Karlsruhe, respectively. An applicable tool to gain answers on relevant questions is the joint supervision of student theses. In addition to gaining knowledge, this offers the students the opportunity to gain deeper insights into a company. On the other hand, the company can possibly attract young people as new employee. In the following, the results of a jointly supervised master thesis on the suitability of geopolymers for the use in an agricultural environment [1] will be presented. These research results have already been reported elsewhere [2]. [ABSTRACT FROM AUTHOR]

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The current paper discusses the petrographic image analysis performed on core specimens that are extracted from a tunnel in the south west of Iran. During tunnel excavation, damages were observed in the inner sections of concrete segments. Due to field observations of damaged segments, environmental parameters and tunnel location, several damage scenarios were proposed. In order to assess damage mechanisms, 69 cores were extracted and a number of standard tests were carried out. Since chemical attacks alter microscopic properties of materials, petrographic image analysis was performed on five of the specimens to evaluate possible microscopic changes in concrete composition. The results show that petrographic image analysis is an efficient method to provide a profound insight into the effects of chemical attacks on concrete members. [ABSTRACT FROM AUTHOR]

The erosion behaviour of cement mortar subjected to sand particle blasting was investigated using the gas-blast method with different impact angles and sand particle fluxes. The corrosion regime under the action of freeze–thaw cycles was also investigated. The erosion rate of the cement mortar was measured and analysed under freeze–thaw cycles using two concentrations of corrosive solutions (8% and 10% mass fractions of salt solutions of sodium chloride and sodium sulfate). Moreover, with the support of scanning electron microscopy images, X-ray diffraction patterns and laser scanning confocal microscopy, the erosion mechanism at different impact angles and freeze–thaw cycles was investigated. The results showed that the erosion rate increased with increasing impact angle and decreased with an increase in sand particle flux. The erosion rate of the cement mortar was also found to first decrease and then increase with an increasing number of freeze–thaw cycles. The erosion damage of the cement mortar surface with significant mass loss was found to be due to two mechanisms – horizontal cutting and vertical pressing. [ABSTRACT FROM AUTHOR]

A repair material for use in the marine environment is developed. The ternary cementitious system (TCS), which contains ordinary Portland cement, calcium aluminate cement and gypsum, causes rapid hardening and displays high strength, and hence can be used as a building repair material. However, the hydration products of the TCS contain a large amount of ettringite, calcium hydroxide and calcium aluminate hydrate, which can be easily corroded by the inorganic ions in seawater. Owing to its pozzolanic activity and ability to bind chloride, slag is added to the TCS. The content of slag in the TCS is a critical factor; hence, the effects of 0–35 wt% slag on the compressive strength, mass change, apparent porosity, and free and total chloride content of TCS immersed in seawater are investigated. The systems with slag show a higher compressive strength than the TCS in seawater, and the reduction in compressive strength of the system with 25 wt% slag is only 14·14% after 180 d. Also, the addition of slag significantly reduces the free and total chloride content of the TCS immersed in seawater. The optimum amount of slag in the TCS is determined to be about 25 wt%. [ABSTRACT FROM AUTHOR]

This paper compares biogenic and chemical acid attack for assessing the final stage of microbially induced corrosion of concrete (MICC). Paste specimens were exposed to either biogenic or sulfuric acid solutions. The solutions had an initial pH of 2. Maintaining the pH of the chemical acid solution in the desired range was highly challenging. The pH of biogenic acid solution remained consistent for a longer time. Calcium leaching measurements showed that biofilm on the surface of specimens exposed to biogenic acidification restricted excessive leaching of calcium from the samples. X-ray fluorescence (XRF) results showed that biogenic acid attack caused higher changes in the chemical composition of the specimens. Flexural strength tests did not show a significant difference between the chemical and biogenic acid attack; however, this could be attributed to the short test duration. [ABSTRACT FROM AUTHOR]

The present study focuses on the combined effects of binder composites on the microstructural, mechanical, and durability characteristics of high-performance concrete that include manufactured sand (M-sand) and Electrical Arc Furnace slag (EAF) aggregate. Also, the influence of multi binders like Ordinary Portland Cement (OPC), Ground Granulated Blast Furnace Slag (GGBS), mS (micro-silica) and nano-silica (nS) have been investigated. The ternary binder system is used to develop HPC mixtures with the effect of the mS in three levels 5%, 10%, and 15% and a quaternary binder system with 1% nS into the optimized ternary system containing 10% mS. Micro-characterization has revealed that the addition of micro-silica (mS) and nano-silica (nS) refined the compact morphology of the multi binder system. Natural aggregate is replaced at the level of 0%, 50%, and 100% with the EAF aggregate. Slump flow value decreased with an increase in micro and nano particles. Mechanical properties of HPC mixes with EAF, as well as a ternary binder without ns and quaternary binder with ns have shown better strength properties due to the combined effect of mS and nS as well as the stronger physical features of EAF slag aggregate. The qualitative tests have shown that the addition of a quaternary binder system has a significant positive effect on the permeable characteristics of HPC mixes. Deterioration due to MgSO 4 solution and HCl acid is reduced due to the addition of ternary and quaternary binder composite. The drying shrinkage of HPC mixes was higher with the inclusion of micro and nanoparticles, but the same decreased with the addition of EAF aggregate. The present finding has revealed that the maximum utilization of EAF aggregate and M-Sand enhanced the durability of concrete. • Quaternary binder system showed dense and refined pore structure. • The better early strength was achieved though ternary and quaternary binder HPC mixes. • Optimized quaternary binder exhibits improved microstructural, mechanical and durability properties. • Over all performance of EAF aggregate enhanced due to ternary and quaternary system. [ABSTRACT FROM AUTHOR]

The experience of operating livestock farms shows that periodic reorganization does not prevent biological corrosion of building structures. In this work, the possibility of using glutaraldehyde as a fungicide for volumetric administration in the preparation of biostable concrete was investigated. The study aims to minimize the adverse effects of the components of commercial biocidal products on the physical and mechanical characteristics of products. For research, we used an aqueous solution of glutaraldehyde with an active substance concentration of 0.5 and 1 %, which was introduced into Portland cement CEM I 42.5 N as mixing water. The degree of influence of the active substance on the properties of cement paste and mortar was estimated according to data on heat release during hydration, strength, and phase composition. The fungicidal activity evaluation of glutaraldehyde in cement systems and the degree of their growth with the Aspergillus niger test culture were evaluated. It was established by isothermal calorimetry that, in mixtures with glutaraldehyde, a delay in the achievement of the main hydration peak is observed – by 30 minutes for 0.5 %, by 1 hour for 1 %. After 72 hours of hydration, a lower total amount of released heat of hydration is observed – for 0.5 and 1% solutions by 6.8 and 5.8 %, respectively. According to X-ray phase and differential thermal analyzes, the phase composition of the initial and aldehyde-modified cement stone on day 28 does not differ and consists of the following phases: ettringite, portlandite, calcite and clinker minerals. Varying the phase composition leads to a change in strength: when using a 0.5 % solution of aldehyde, the power of the cement-sand mortar increases by 6.5 %, and a 1 % solution decreases by 6.7 %. The use of a 0.5 % solution of glutaraldehyde provides a decrease in the intensity of fungal development and the formation of a fungistatic effect. Based on the results, a 0.5 % solution of glutaraldehyde can be recommended for the development of cement composites with prolonged bio-resistance.

High-performance fiber reinforced cementitious composites from ettringite-based binders require much understanding of durability before its real-life applications in construction industry. A strain-hardening fiber reinforced ettringite-based composite from the hydration between ladle slag and gypsum with polypropylene (PP) fibers was the object in this study. To investigate the durability of the developed composite under aggressive conditions in cold regions (e.g., the Northern Europe), the material was subjected to a combined sodium sulfate-chloride solution along with freeze-thaw cycling process, which represented the marine environment of cold regions. The experimental study reports the vital role of PP fibers in control crack propagation and, hence, greatly enhanced the durability of the composite. In addition, the developed composite attained good mechanical performance with deflection-hardening behavior and multiple crack even after aging processes. Materials, aged in water, was mainly destructed by volume expansion from water uptake in structural pores, while those, cured in Na 2 SO 4 NaCl solution, was mainly spoiled by volume increase from both physical and chemical attacks. Image 1 [ABSTRACT FROM AUTHOR]

• Chemical durability of superabsorbent polymers based geopolymer mortars was assessed. • Superabsorbent polymers based geopolymer mortars offered good resistance to acid, sulfate, and chloride attack. • Using superabsorbent polymer offers a protective effect on the microstructure of geopolymer mortars. • Use of superabsorbent in geopolymers demonstrated a greater degree of geopolymerization. This study investigates the durability of superabsorbent polymer (SAP) based geopolymer mortars (GPMs) against acid, sulfate, and chloride attack. Nine mix formulations containing 0, 1, and 2% SAP content by weight of fly ash were prepared. All the samples were cured at 80 °C, followed by curing at room temperature for 24 h. The specimens were immersed in the chemical solutions of 5% hydrochloric acid (HCl), 5% sodium sulfate (Na 2 SO 4), and 5% calcium chloride (CaCl 2) for 180 days. Thereafter, the durability performance of GPMs was evaluated based on the change in weight and change in compressive strength of the specimens. Based on the results, it was deduced that SAP based GPMs were less vulnerable to chemical attack. Furthermore, deterioration effects were lower due to improved sorptivity and porosity values. The X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscope (SEM), and Energy Dispersion X-ray Spectroscopy (EDX) analyses revealed that the inclusion of SAP improves the chemical durability of GPMs. [ABSTRACT FROM AUTHOR]

Construction and associated demolition processes produce huge amount of solid waste, generally termed as construction and demolition waste (CDW). Management and proper disposal of these wastes is an area of prime concern for modern civil engineers. About 90% of all CDW is composed of building derived materials (BDM) obtained from concrete, bricks, and tiles from structural and non-structural elements of a building. The present study emphasizes on the use of virgin BDM, which conserves natural aggregate, reduces the impact on landfills, saves energy, and thus can provide significant cost benefit. Five types of BDM—crushed lightweight concrete (T1), crushed marble tiles (T2), crushed high strength concrete (T3), crushed normal portland cement concrete (T4), and crushed bricks (T5)—are characterised to assess their compatibility when used in conjunction with local soil. The soil, BDM and soil-BDM mixes are characterized from physical, mechanical, mineralogical, microstructural, and chemical aspects. These tests are then repeated for the aforementioned soil-BDM mixes after immersion in acids. Aggregate impact value (AIV) results on the five types of BDM indicate that T1 and T5 are poorly resistant to impact loads. However, T2, T3, and T4 show relatively better resistance to impact loads and satisfy the requirements for sub-base material standards. Shear strength studies show that the average optimum replacement of soil by BDM is in the range of 17-23% by mass. In order to test the compatibility of BDM in soils containing aggressive chemicals, the properties mentioned above are re-evaluated after exposing the BDM to aggressive chemical environments. The results indicate that the internal angle of friction (ϕ) of virgin BDM is found to vary significantly due to acid attack. The results of AIV after exposing the BDM to acids show that BDM are highly susceptible to chemically aggressive environment. The performance of all types BDM are affected by the presence of acids and appropriate measures must be adopted while using BDM in such chemically aggressive environment. These standards can be used as guidelines in the present study in the absence of specific standards for BDM applications. [ABSTRACT FROM AUTHOR]

Objectives: Public transport vehicles (PTVs) play a decisive role in development of the urban economy. However, the safety of PTVs is threatened by the man-released chemical or arson attack. It was found that indoor air safety can be greatly improved by employing air-rain ventilation instead of the common ventilation in a PTV.Methods: Numerical simulations and experiments have been done to prove the effectiveness of the air-rain flow against chemical attack or arson in PTVs.Results: The research shows that, during a chemical attack, an air-rain flow of 0.1 m/s can constrain the spread of a chemical agent in a very limited zone near its source, which is far away from the passengers' breathing area in the PTV. During an arson attack, at an air-rain flow of 0.3 m/s, most of the area in the PTV maintains a low temperature for at least 60 s during a fire, which is long enough for passenger evacuation.Conclusion: Compared to common ventilation, the key characteristic of air-rain ventilation is its resistance to the blending effect of the air. Because of this, the spread of chemical agents, hot gas/combustion products during a fire, and fuel aerosol is constrained to a limited area in a PTV. Passengers are then protected from chemical attack, explosion of fuel aerosols, and high temperatures and smoke. Thus, we can say that this new ventilation mode increases passenger safety in buses. [ABSTRACT FROM AUTHOR]

The chemo-mechanical degradation of unreinforced concrete sewer pipes applied in domestic service locations is assessed through a systematic, integrated experimental approach, considering 18 new and 35 used sewer pipes. The characteristics and environmental conditions of the sewer pipes are reported, and data obtained from surface condition classification, residual alkalinity tests and XRD analyses are combined to identify the type and degree of chemical attack of the used sewer pipes. Concrete material properties are determined by material tests on sewer pipe samples, providing quantitative insight into the age dependency of the Young's modulus, compressive strength, tensile strength and mode I toughness. All relatively old pipes (installed in the 1920s and 1950s) show substantial chemical attack by biogenic sulphide corrosion (at the inner side of the pipe) and carbonation (at the outer side of the pipe). The time development of the corresponding corrosion depths on average follows a linear trend, whereby the corrosion rate for biogenic sulphide corrosion is about a factor of 1.3 larger than for carbonation. Due to these chemical processes, the mechanical properties of concrete may significantly depend on the age of the sewer pipe. In particular, the average compressive strength and average tensile strength decrease approximately linearly with the age of the pipe, in correspondence with relative reductions of, respectively, a factor of 1.7 and 1.5 over a period of almost 100 years. The values and time-dependent trends found for the concrete properties and corrosion depths of sewer pipes can serve as input for practical analyses and advanced numerical simulations on their bearing capacity and time-dependent degradation. The experimental results also emphasize the importance of regularly assessing the amount of chemical degradation of (especially older) in-situ sewer pipes, by determining the (decrease in) effective wall thickness via core sampling and laser profiling. • Concrete sewer degradation is studied through an integrated experimental approach. • Type and degree of (bio)chemical attack are identified. • Concrete material properties are determined by material tests on sewer pipe samples. • Biochemical corrosion depth on average develops linearly in time. • Experimental results can serve as input for analyses on sewer bearing capacity. [ABSTRACT FROM AUTHOR]