Durability Of Concrete Research Articles

PSO-BP model for assessing frost resistance in containment concrete with varying pipe diameters

The safety of containment concrete is of utmost importance for nuclear power plants. The presence of pipe openings in the containment concrete structure introduces weakened areas, which adversely impact the mechanical properties and durability of the concrete. However, little research has been done on the durability of containment concrete with embedded steel pipe (CCESP), and no studies are found on its frost resistance under single-side freezing and thawing conditions. In this paper, using single-side salt freeze-thaw experiment to simulate the practical situation of coastal containment concrete, the effect of different steel pipe diameters (d) on the frost resistance of containment concrete was investigated. Based on the experimental results and using backpropagation neural networks optimized by a particle swarm algorithm (PSO-BP), a model was established to predict the frost resistance of CCESP for varying values of d. The research results showed that wall effects and stress concentrations created an interface zone between the steel pipes and the concrete, leading to a decline of compressive strength. Freeze-thaw cycles had only a slight impact on the relative dynamic elastic modulus (E) of CCESP, while the exfoliation mass per unit area (M) of the concrete specimens increased linearly with d. It indicates that pipe opening adversely impacts the frost resistance of the concrete, and that M can be used to evaluate the frost resistance of CCESP. This study addresses the research gap in the frost resistance of containment concrete with steel pipe openings, and the proposed PSO-BP model can accurately predict the frost resistance of containment concrete with varying pipe diameters under different freeze-thaw cycles.

Assessing the Durability, Mechanical, and Microstructural Properties of Nanosilica-enhanced Coconut Shell Concrete: A Sustainable Approach

This study explores the properties of concrete as a sustainable substitute for cement through the use of nanosilica in an eco-friendly aggregate system. Daily life generates a larger amount of coconut shell waste from the tropical zone. In India, the yearly deposition of coconut shell is about 80,000 tonnes, which is 6.7% of total agricultural waste. Crushing gravel production emits CO2, which is an environmental concern. Simultaneously, to diminish waste disposal of coconut shell can be effectively utilised as coarse aggregate in lightweight concrete. The conventional concrete (CC) was fully replaced by coconut shell coarse aggregate and crushed gravel sand (Msand) as fine aggregate in plain Portland cement. Nanosilica replaces cement in the conventional blend at 0%, 1%, 2%, 3%, and 4%. This study describes the concrete's hardened properties, such as compressive strength, splitting tensile strength, and flexural strength. Among all the mechanical performances, the N2 blend is significant. The N2 mix exhibits a trend that aligns with the correlation between compressive strength and splitting tensile strength. The transport durability performance related to capillary wick action of the optimum blend (N2 mix) has 0.018 mm/min0.5. The pore filler mechanism and pozzolanicity of 2% NS is more synergic than other combinations. The N2 mix in H2SO4 environment has less mass and strength loss. The N2 blend's morphology is robust relative to the CC mix because of the secondary C-S-H gel and homogeneous, smooth hydrated grain. As a result, the report concludes that using coconut shell as an aggregate in concrete can reduce waste disposal in landfills, while using nanosilica in place of cement can reduce CO2 emissions.

ASSESSMENT OF AGGREGATE MIXTURE REACTIVITY IN CONCRETE AT 60°C

Research on the durability of structural concrete requires careful selection of aggregates, particularly considering their reactivity to alkali-silica reaction (ASR). The Miniature Concrete Prism Test (MCPT) allows for shortened testing time and eliminates the need for aggregate crushing, making it a practical alternative to other methods. The aim of the research is to evaluate the reactivity of aggregate mixtures with varying mineral compositions. Research results confirm the significant impact of fine aggregates on concrete expansion in the MCPT method in NaOH solution at 60°C. The observed expansion correlates with a reduction in concrete’s elastic modulus.

Experimental Investigation of the Durability of Ambient-Cured Metakaolin-Based Geopolymer Concrete in Different Sustainable Environmental Conditions

Geopolymer concrete (GPC) has received much attention among researchers in recent decades due to its increased durability properties. It helps reduce massive pollution and high energy consumption during cement production. Various cementitious materials having high alumino-silicate, such as, fly ash (FA), ground granulated blast furnace slag (GGBS), rice husk ash (RHA), and metakaolin (MK), are typically used for producing GPC. These materials are activated by an alkaline solution through a polymerization process. This study examined the durability properties of metakaolin-based GPC with fly ash and GGBS under ambient curing conditions (23 ± 20 ℃). The mechanical characteristics like compressive strength, splitting tensile strength, flexural strength, and durability properties like the sorptivity volume of permeable voids exposed to chloride, sulphate, and acid environments were studied and reported. Also, an effort has been made to establish a relationship among the mechanical properties. The test results show that better performance of GPC can be achieved with 40% replacement of MK with 10% FA and 50% GGBS under ambient curing than controlled concrete. The MK-GPC with a higher proportion of metakaolin, showed good resistance to environmental factors. It is a potential alternative to conventional cement concrete.

Proposed standardization changes in the assessment of concrete durability

The article presents the concept of concrete durability based on the system of concrete resistance classes to ERC exposure included in the proposed standardization documents (EN 206-1 together with EN 206-100 and Eurocode 2). According to the ERC concept, the performance properties of concrete are tested using recognized test methods, and the results are assessed on the basis of criteria independent of the composition of the tested concrete. The ERC durability concept is open to new technical and standardization solutions in the field of concrete composition (new additives) and cement and should replace the generally applicable prescriptive solutions. This solution is important from the point of view of reducing the emissions of the cement industry (production of multi-component cements and the use of new non-clinker main ingredients) and reducing the carbon footprint of concrete (CO2 reduction classes of concrete according to prEN 206-1)

Research on quantitative design methods for the durability of reinforced concrete structures in a hot ocean environment

This paper establishes a quantitative design method for the durability of concrete structures in cross-sea bridges through investigation, rapid chloride migration coefficient method (RCM) and theoretical calculation, considering the impact of temperature on chloride ion diffusion rates in a hot marine salt erosion environment. Combined with the RCM test and bridge service data, a quantitative design method for bridge concrete durability is proposed. Test results show that the growth rate of the chloride ion diffusion coefficient of concrete is approximately 1.028 for every 1 °C increase. For every 5 °C increase, the growth rate of the chloride diffusion coefficient of concrete is about 1.15, and the cover depth of the concrete structure should be multiplied by a coefficient of 1.07. Therefore, the concrete cover depth should be appropriately increased, considering the influence of ambient temperature. Furthermore, fly ash, slag, and stone powder can increase the concrete’s resistance to chloride corrosion. When the influence of temperature on the chloride ion diffusion coefficient is considered, the durability design of the concrete structure of the sea-crossing bridge is conducted, which is beneficial for ensuring their service life.

Study on microstructure and mechanical properties of steel corrosion products in marine environment

The microstructure and mechanical properties of steel corrosion products in marine environment are key parameters for developing the concrete corrosion-induced model. In this study, steel corrosion products from steel plates, concrete specimens with 10 mm and 20 mm covers, and cracked beams in Zhejiang province were sampled and analyzed. Initially, the microstructure of the steel corrosion products were determined by X-ray diffractometry (XRD), thermogravimetric analysis (TG), scanning electron microscopy (SEM), and energy-dispersive spectrometry (EDS). Subsequently, the mechanical properties of steel corrosion products including nanoindentation elastic modulus, hardness and instantaneous elastic modulus were measured by nanoindentation and consolidation experiments. This study holds potential for establishing the concrete corrosion-induced model and assessment of the concrete structure durability in marine environment.

Comparing durability and compressive strength predictions of hyperoptimized random forests and artificial neural networks on a small dataset of concrete containing nano SiO2 and RHA

Through the increasing use of supplementary cementitious materials, the properties of concrete have taken on increased significance in a design code. Using reliable prediction models based on a small data set for the mechanical properties and durability of concrete can reduce the number of trial batches and experiments needed to produce useful design data in the laboratory, reducing time as well as resources. In this study, we investigate how the properties of water penetration, chlorine resistance, and compressive strength can be predicted by polynomial regression (PR), random forest (RF) regression, and artificial neural networks (ANNs) based on the input values of density, workability, and the constituent amount of rice husk ash, cement, and nano SiO 2 . We vary the training data used and test the coefficient of determination ( R 2 score) on the remaining data as a test set to measure predictive capability. We show that RFs and ANNs outperform PR in all settings and have unambiguously extrapolating properties when hyperparameter optimization is designed for this purpose. Remarkably, we obtain R 2 scores on the test data of 0.858 − 0.990 for RFs and 0.825 − 0.985 for ANNs.

Feasibility of foam concrete using recycled brick and roof tile fine aggregates

Brick (BR) and roof tile (RT) fine aggregate fractions derived from construction and demolition wastes have a low recycling rate in new construction and building materials. This article assesses their suitability for replacing the limestone aggregate in foam concrete, which helps valorise such fractions and conserve natural limestone resources. Two concrete categories containing or not silica fume (SF) were investigated, while the BR and RT aggregate replacement rates were 10%, 20% and 40%. Tested properties include flow, density, water absorption, porosity, thermal conductivity, mechanical strengths, microscopy, drying shrinkage, resistance to freeze/thaw cycles and elevated temperature. Results showed that the concrete mechanical properties improved when the limestone aggregate was replaced by 10% BR or RT but gradually curtailed at higher addition rates. Such results concorded with the density, water absorption and porosity measurements. Foamed concrete containing BR is more resistant (compared to RT) to drying shrinkage, freeze/thaw cycle, and heat exposure, which was ascribed to the relatively lower BR porosity that improves the concrete mechanical properties and durability.

Advances in Highly Ductile Concrete Research.

In recent years, high-ductility concrete (HDC) has gradually become popular in the construction industry because of its excellent ductility and crack resistance. Concrete itself is a kind of building material with poor tensile properties, and it is necessary to add a large number of steel bars to improve its tensile properties, which increases the construction cost of buildings. However, most of the research studies on high-ductility concrete are scattered. In this paper, the basic mechanical properties of high-ductility concrete and the effects of dry and wet cycles, freeze-thaw cycles, and salt erosion on the durability of high-ductility concrete are obtained by comprehensive analysis. The results show that the tensile properties of HDC can be significantly improved by adding appropriate fiber. When the volume fraction of steel fiber is 2.0%, the splitting tensile strength of concrete is increased by 98.3%. The crack width threshold of concrete chloride erosion is 55-80 μm, and when the crack width threshold is exceeded, the diffusion of CL-1 will be accelerated, and the HDC can control the crack within the threshold, thereby improving the durability of the concrete. Finally, the current research status of high-ductility concrete is analyzed, and the future development of high-ductility concrete is proposed.

Mechanical properties and micro-mechanism of seawater cementitious materials reinforced by in-situ polymerization

Understanding the potential mechanism of in-situ polymerization of acrylamide (AM) for modifying seawater cementitious materials is crucial for designing high-strength and durable marine concrete. Herein, the acrylamide (AM) in-situ polymerization was investigated for its effects on the hydration behavior, micro-morphology, and pore structure of cementitious materials mixed with seawater and freshwater through a series of elaborately designed microscopic characterization methods. The results reveal that the hydration process of cementitious materials proceeds simultaneously with in-situ polymerization. However, compared with freshwater mixtures, seawater provides a large number of metal ions and SO42- ions, which can cross-link with the generated polyacrylamide (PAM) during in-situ polymerization to form a three-dimensional network structure. The synergistic effect of the hydration, in-situ polymerization, and cross-linking processes of cementitious materials can improve the pore structure of seawater-mixed paste, enhance erosion resistance, and improve the stability and toughness of microstructure. These findings were further confirmed by comparing infrared spectroscopy results, hydration products, pore size, and micro-morphology analysis as well as flexural performance tests. This is of great significance to guide the design of novel materials in marine infrastructure.

Impact of concrete durability improvement on building life cycle carbon emissions: a case study of residential buildings in Northwest China.

Building carbon emissions (CE) have become the focus of the current topic, but there is still no mature typical building life cycle theory method from the perspective of building materials, and the research on the relationship between building durability and building life cycle is still insufficient. To this end, this study established a detailed calculation method for building carbon emissions (CE) and divided the building life cycle (BLC) into three stages: manufacturing, use, and demolition according to the result analysis. In addition, a durability improvement and carbon reduction scheme of "partition, resistance, and repair" is proposed, and the carbon emission reduction index of effectiveness index is proposed. The proposed method is applied to the case of residential buildings in Northwest China. The main conclusions are as follows: the CE of residential buildings are more dependent on the use stage. If the centralized heating system is adopted, the CE in the operation stage account for 80-90%. If the air conditioning refrigeration and heating system is adopted, the CE in the operation stage account for about 50%. Using the method of improving the durability of buildings to extend the service life of buildings is very significant for building carbon reduction (RC); the effectiveness index proposed in this paper includes key indicators such as total CE, service life, and building area. Compared with the traditional index, the effectiveness index is more accurate and comprehensive. CR is the focus of green building, but the impact of economy needs to be considered in practical engineering. In the future research, durability, CE, and economy need to be considered comprehensively for careful study.

Experimental and Modeling Analysis of Polypropylene Fiber Reinforced Concrete Subjected to Alkali Attack and Freeze-Thaw Cycling Effect.

The durability of concrete materials in harsh environmental conditions, particularly in cold regions, has garnered significant attention in civil engineering research in recent years. Concrete structures in these areas are often damaged by the combined effects of alkali-silica reaction (ASR) and freeze-thaw cycles, leading to structural cracks and significant safety hazards. Numerous studies have demonstrated that polypropylene fiber concrete exhibits excellent crack resistance and durability, making it promising for applications in cold regions. This study elucidates the impact of alkali content on concrete durability by comparing the mechanical properties and durability of different alkali-aggregate concretes. The principal experimental methodologies employed include freeze-thaw cycle experiments, which examine patterns of mass loss; fluctuations in the dynamic modulus of elasticity; and changes in mechanical properties before and after freeze cycles. The findings indicate that increased alkali content in concrete reduces its strength and durability. At 100% alkali-aggregate content, compressive strength decreases by 35.5%, flexural strength by 32.9%, mass loss increases by 35.85%, relative dynamic elastic modulus by 39.4%, and residual strength by 97.28%, indicating higher alkali content leads to diminished durability. Additionally, this paper introduces a constitutive damage model, validated by a strong correlation with experimental stress-strain curves, to effectively depict the stress-strain relationship of concrete under varying alkali contents. This research contributes to a broader understanding of concrete durability in cold climates and guides the selection of materials for sustainable construction in such environments.

Long-term study on the mechanical properties of the ITZ in coral aggregate concrete and its impact on material durability

The rich coral reef resources on the island make coral aggregate concrete (CAC) widely applied in marine engineering construction. This study extensively investigates the mechanical properties of the interfacial transition zone (ITZ) within CAC and its consequential influence on the overall mechanical performance of concrete. This article uses the interface bonding strength method, microscopic hardness technology, and X -ray diffraction (XRD) test. It is found that the performance of ITZ is critical to the overall performance of CAC. Optimizing the formation of cement paste and regulating the generation of hydrophilic products can significantly enhance the interface strength and durability of concrete. Our findings demonstrate a clear mathematical correlation between the splitting tensile strength of interface bonding and the microhardness value of the ITZ, offering a novel theoretical framework and practical approach for concrete structure design. The characteristics of hydrophilic products within the ITZ, such as the orientation and dimensions of CH crystals, directly influence the intricate properties of concrete. Therefore, in the process of concrete preparation and construction, attention should be paid to the control and optimization of these micro-structural parameters.

Eco-Sustainable Cement: Natural Volcanic Tuffs’ Impact on Concrete Strength and Durability

This study underscores the potential of utilizing natural volcanic tuffs (NVTs) as supplementary cementitious materials (SCMs) in alignment with global sustainability efforts aimed at mitigating the cement industry’s negative impacts on both the economy and the environment. Experimental investigations were conducted on concrete mixtures containing 10%, 20%, 30%, 40%, and 50% NVT as partial cement replacements to assess their influence on concrete’s mechanical and microstructural properties. Based on the findings, concrete samples with 10% NVT replacements exhibited increased flexural and compressive strengths of 35.6% and 5.6%, respectively, compared with ordinary concrete after 28 days. The depth of water penetration in the concrete samples was significantly reduced by the inclusion of NVT, with a maximum reduction of 56.5%. Microstructural analysis using scanning electron microscopy (SEM) revealed enhanced densification of the concrete microstructures, attributed to the high pozzolanic activity of NVT use in cement-based composites. Analysis of variance (ANOVA) revealed statistically significant relationships between NVT content and both the compressive and flexural strengths of the concrete samples. In conclusion, substituting 10% cement with NVT not only enhances the mechanical properties of concrete but also decreases the energy demand for cement production and reduces carbon dioxide (CO2) emissions, thus contributing to more sustainable construction practices.

Effect of plantain peel ash as an admixture on concrete properties

This study investigates the effect of plantain peel ash as an admixture on concrete properties, which is a sustainable alternative to conventional concrete production. The aim is to optimize the mix design of concrete required for improved performance, investigate the effect of the plantain peel ash on the compressive strength of the concrete, and examine the effects of plantain peel ash as a supplementary material on the durability and service life of concrete. The use of plantain peel ash as an admixture for cement in concrete has gained increasing popularity due to its ability to reduce the environmental impact of concrete production. This study contributes to the understanding of the durability and performance of plantain peel ash in concrete which is crucial for sustainable construction practices. The methodology involves mix design according to IS 10262:2009 for M15 grade of concrete with 5%, 10%, 15% and 20% plantain peel ash replacement, testing of compressive strength and durability of the concrete samples and also the optimal dosage required, in comparison with conventional concrete. The result of this study shows that the addition of 5% plantain peel ash increases the compressive strength of the concrete with obtained value of 27.30 N/mm2 and also has the standard workability for a normal concrete at 45 mm for the control and 60 mm for 5% PPA. The 10%, 15% and 20% shows a decrease in their compressive strength compared to the control mix (0%) with a value of 18.42 N/mm2 for 28 days curing. Overall, it can be said that 5% plantain peel ash has provided a strong basis for the use of plantain peel ash in concrete mixtures. The 5% is equivalent to 0.72 kg PPA.

Enhancing Concrete Performance with Waste Foundry Sand Using Ternary Blended Mixes of Ordinary Portland Cement, Silica Fume, and Ground Granulated Blast Furnace Slag

AbstractMineral admixtures play an important part in improving the strength characteristics of concrete. This manuscript presents the incorporation of silica fume (SF) and ground granulated blast furnace slag into the concrete mix to decrease the cement content and enhance the strength and concrete's durability. In addition, river sand deposits have started to dry up. Also, eco‐friendly disposal of industrial wastes acts as a major threat to industries. Hence, the use of waste foundry sand (WFS) and M‐sand (MS) as fine aggregate is attempted in this study. In the first phase of this research work, concrete specimens have been prepared by partially replaced cement with 0%, 10%, 20%, 30%, and 40% by Ground Granulated Blast Furnace Slag (GGBFS) and 0%, 5%, 10%, and 15% by SF to find their optimum replacements in Ternary Blended Concrete (TBC). In the second phase, concrete specimens replaced with 0%, 10%, 20%, 30%, and 40% by WFS for fine aggregate (MS) were prepared and found optimum usage of foundry sand in waste foundry sand concrete (WFSC). In the third phase, a ternary blended green concrete (TBGC) was prepared by partially replaced cement with 30% GGBFS and 10% SF and replaced MS with 30% WFS and conducted strength (flexural strength, compressive and split tensile strength) and durability (acid and sulfate attack) studies. The above combination was found to be a promising way for the development of environmentally friendly concrete.

Long-term durability of iron-rich geopolymer concrete in sulphate, acidic and peat environments

This study assesses the behaviour of iron-rich type F fly ash geopolymer concretes (GC) exposed to simulated sulphate, acidic, and peat environments, typical of those encountered in tropical peatlands. GC and Portland cement (PC) concrete of comparable strengths were exposed to a range of simulated solutions for 18 months, including 5 % magnesium sulphate (MgSO4), 5 % sodium sulphate (Na2SO4), 1 % and 3 % sulfuric acid (H2SO4) and peat. The GC generally outperformed PC in all conditions. The GC showed a significant increase in strength in the first year, along with enhanced durability properties. Microstructural analysis indicated a decrease in total porosity and pore size. This was attributed to continuing geopolymerization leading to the foration of additional N-A-S-H gel, which filled the pores and solidified the concrete matrix. However, compressive strength decreased at 18 months due to crack propagation caused by drying shrinkage. In Na2SO4, GC attained an 8.9 % and 6.3 % increase in compressive strength at 12 and 18 months, respectively, again attributed to ongoing geopolymerization. GC exposed to MgSO4 exhibited a significant decrease in compressive strength of approximately 11 % at 12 months and 19.8 % at 18 months, attributed to the formation of lower-strength M-A-S-H from reaction between MgSO4 and N-A-S-H gel. After 12 months GC exposed to 1 % and 3 % H2SO4 demonstrated a decrease in compressive strength of approximately 1.2 % and 4.5 %, respectively, together with 2 % and 3 % mass loss. Chemical and microstructural data confirmed this strength reduction due to the vulnerability of N-A-S-H to when exposed to H2SO4. GC exposed to peat solution exhibited a 1.25 % increase in compressive strength at 12-month, but a decrease of 11.3 % at 18-month. Microstructural analysis observed a reduction in Na+ within GC matrix, and the presence of gypsum. The reduction in pore sizes and total porosity suggested generation of zeolite crystalline material was contributing to the pore filling.

Durability fragility curves for service life prediction of concrete with various supplementary cementitious materials subjected to natural carbonation

This study estimates the service life of concretes containing supplementary cementitious materials (SCM) subjected to carbonation from a probabilistic and reliability-based perspective. The aim is to enhance understanding of the risks associated with degradation and to propose an alternative approach for estimating the durability of reinforced concrete (RC) structures. The inclusion of supplementary cementitious materials (SCMs) is crucial for making concrete more sustainable, as these materials can reduce the carbon footprint of concrete production and improve its durability. Using available natural carbonation data from the literature on samples containing SCM, computational codes were developed for reliability analyses via the Monte Carlo Simulation method. The results indicated that all concrete samples exhibited a 100% probability of failure for coverages of 20 mm and 25 mm at an age of 100 years. For a coverage of 30 mm, all samples maintained a failure probability of over 98% within the same period. Notably, concretes incorporating metakaolin showed a substantial reduction in failure probability across all evaluated time periods, indicating superior durability compared to other samples. These findings significantly contribute to a deeper understanding of concrete degradation processes and provide valuable insights for the design and maintenance of RC structures, particularly in the context of using SCM. By adopting a probabilistic approach, the study underscores the importance of considering variability and uncertainties in predicting concrete durability, ultimately aiding in the development of more resilient and long-lasting infrastructure.

Mesoscopic simulation of concrete drying shrinkage with hydration kinetics

Shrinkage-induced cracking significantly impacts the durability of mass concrete structures. Quantitatively evaluating drying shrinkage of concrete proves challenging due to the time-consuming experiments and overlooked microstructure changes during the hydration process. To address this concern, this study initially characterized the long-term hydration products and microstructure of low-heat Portland cement (LHPC) through microstructural experiments. Subsequently, a novel high-resolution mesoscale framework is developed to investigate the drying shrinkage with hydration kinetics. High-resolution models consist of realistic-shaped aggregates are validated by the aggregate morphology and gradation parameters of core sample from mass concrete. Concurrently, the quantitative effects of internal and external factors on LHPC drying shrinkage are explored. Results indicated that LHPC possesses a denser microstructure, lower porosity, higher carbonation resistance, and 20% lower drying shrinkage compared to moderate-heat Portland cement, suggesting promising applications. Furthermore, experimental and computational findings suggested that increasing aggregate volume, controlling aggregate morphology, and adjusting curing time and humidity could be employed to reduce and manage drying shrinkage, ensuring concrete structure durability.