Explore the vast range of titles available.

The effects of acid rain corrosion on the properties of concrete are broadly understood. This study investigated the impact of varying corrosion conditions on the microstructure and mechanical properties of concrete, which has not received sufficient attention using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and compressive tests. In the laboratory, simulated acid rain solutions with pH levels of 0.0, 1.0, and 2.0 were prepared using sulfuric acid solution. A total of 13 sets of 39 concrete cubes each were immersed in these acid solutions for durations of 7, 14, 21, and 28 days. The findings clearly indicate that simulated acid rain corrosion significantly affects both the microstructure and mechanical properties of concrete. Acid alters the material composition of concrete and simultaneously increases the formation of pores within it. This not only changes the number, area, and perimeter of the pores but also affects their shape parameters, including circularity and fractal box-counting dimension. These pores typically measure less than 0.4 μm and include micro- and medium-sized pores, contributing to the more porous and structurally loose concrete matrix. As the duration of acid exposure and the concentration of the acid solution increase, there is noticeable decrease in compressive strength, accompanied by changes in the concrete structure. The rate of strength reduction varies from 6.05% to 37.90%. The corrosion process of acid solution on concrete is characterized by a gradual advancement of the corrosion front. However, this progression slows over time because as the corrosion depth increases, the penetration of the acid solution into deeper layers becomes limited, thereby reducing the rate of strength deterioration. The deterioration mechanism of concrete can be attributed to dissolution corrosion caused by H+ ions and expansion corrosion due to the coupling of SO42− ions.

Acoustic Emission (AE) application for Structural Health Monitoring (SHM) has undergone a swift advance through research and innovation in recent times. The AE monitoring is widely exploited as a tool for damage detection in materials research and structure monitoring. Various advantages of the AE, such as the potential use in large and complex structures, high-sensitivity, real-time monitoring capability, and potential application across a wide range of field study, has given the technique an edge over other approaches. Nevertheless, most of the reported studies had focused on the interpretation of the results in both quantitative and qualitative perspectives to extend the capabilities and application of AE for damage detection strategy. Eventually, the quantification of the damage level of the concrete structure relative to fatigue loading remained unanswered. Therefore, this study presented the experimental investigation of four types of plain concrete beams with a fixed dimension of 100 × 200 × 600 mm in the different notch-to-depth ratios under cyclic loading. A setup of the instrument consisting of four AE sensors type R6I was employed on each concrete beam sample to ensure a precise measurement for the three-point bending test. The b-value, improved b-value (Ib-value), severity, and intensity analysis methods were applied to quantify the damage level of the concrete structure under fatigue loading. Based on the results, the AE analysis successfully classified the damage levels following the observation made during the increasing cyclic loading on the notched concrete beams, the initiation of cracks, the steady growth of cracks, and beam failure. Valuable insights were recorded throughout the observation, including the progression of the fatigue failure mechanism from the Ib-value results, the intensity chart patterns from the intensity analysis, and the increased severity due to the increased loading cycles from the severity analysis. Conclusively, this study would enable researchers to understand the trend in monitoring the damage level under fatigue loading using the AE technique as well as providing fresh insights for further research.

Precast concrete sandwich wall panels (PCSPs) are popular for building exteriors due to their high thermal efficiency, composite performance, and low manufacturing and maintenance costs. Researchers have investigated the possibility of reducing the panel thickness while maintaining the cladding components’ thermal efficiency and strength to further improve efficiency and to reduce material consumption. However, limited research has been conducted on the shear bonding of steel plates, which is critical to ensuring durability and energy efficiency. This study investigated the shear behaviour of PCSPs with an S-type shear connector (SSC) through nine push-off tests and non-linear finite element modelling using Abaqus. Parametric studies were carried out to investigate the influence of the geometric properties of the SSC, the yield strength of the steel and the insulation thickness. The results suggest that the maximum secant stiffness for SSCs was achieved at a width of 101.4 mm and a thickness of 2 mm. Therefore, it is recommended that the width of the SSCs be limited to this value or less. Furthermore, the study found that increasing the yield strength of the steel beyond a thickness of 2 mm and a width of 101.4 mm did not improve the results and had a negative impact on the secant stiffness of the SSCs.

Purpose The purpose of this paper is to present the investigation of damage severity of reinforced concrete (RC) beam subjected to increasing fatigue loading using intensity of acoustic emission (AE) signal. Design/methodology/approach Together 17 RC beams with dimension of 150 × 150 × 750 mm were prepared. Third point loading fatigue test was performed based on load at the first crack (Pcr) and the ultimate static load (Pult). The frequency of 1 Hz was used with the increasing fatigue loadings, 0.5Pcr (P1), 0.8Pcr (P2), 1.0Pcr (P3), 0.2Pult (P4), 0.5Pult (P5) and 0.6Pult (P6). The damage severity of crack for each phase of loading allowed the identification of the crack modes of the beams, namely, Zone A (no significant emission), Zone B (minor), Zone C (intermediate), Zone D (follow-up) and Zone E (major). Findings The intensity analysis indicated clear trend with respect to crack propagation in the beam and, hence, can be used to monitor the crack occurrence in the beam. Originality/value The intensity analysis has been carried out for the beam subjected to increasing fatigue loading. The analysis was based on the AE data obtained from channel basis and located event.

Corrosion of reinforcement is one of the causes of concrete deterioration by the water contained chloride ions and gas, for example hydrogen sulfide that penetrate into the concrete structures. By performing the related transport properties testing, it will fulfill the main objective of this research that is to investigate the fluid transport and bonding properties between normal concrete substrate (NC) and green USM reinforcement concrete (GUSMRC) containing ultra-fine palm oil fuel ash (UPOFA) as repair material. GUSMRC is the type of concrete that has been upgraded from the ultra-high performance fiber reinforces concrete (UHPFRC) with 50 % of UPOFA replacing the cement. Recently many researchers have found that the POFA can be used as partial cement replacement in the concrete which can improve the durability and also the fluid transportation properties. For the bonding properties, two types of surface treatment / roughness will be perform to investigate the greatest bonding and also the durability between NC substrate that act as an old structures with GUSMRC as new repair material. It’s important to perform the other related testing so that the future results obtained can be conclude either this new green ultra-high concrete can resist the harmful environmental aggression and also if it has an excellent bonding with the old concrete as a repair material.

The design of the concrete mixtures of Ultra High Performances Fibre Reinforced Concrete (UHPFRC) is related to a densely compacted cementitious matrix and has outstanding material characteristics involving workability and high mechanical properties. Generally it is a combination between high strength concrete and fibres. UHPFRC offers high compressive strength which is higher than a normal concrete. The application of POFA as a cement replacement enhances the transport properties of concrete and contributes to a sustainable environment. The utilization of 50% UPOFA in mix design leads to develop a new class of concrete designated as GUSMRC. GUSMRC mixtures enhance the mechanical behaviour of concrete. GUSMRC with 50% replacement of the total binder content by ultrafine palm oil fuel ash (UPOFA) could contribute sustainability of environmental. The development of UHPFRC and its application in the field may contribute a good bonding strength at interface as a repair material between a new and old material. However, complex properties of materials can change dramatically when exposed to the elevated temperatures and adversely affected. The physical and chemical will change when occurred to heat. This paper investigates the change in mechanical properties of UHPFRC at elevated temperature and to determine the bonding strength between two layers which is overlay and concrete substrate

The potential properties of carbon nanotube-cement based materials strongly depend on the dispersion of carbon nanotubes (CNTs) within the cement matrix and the bonding between CNTs and the hydrated cement. The homogeneous dispersion of CNTs in the cement matrix yet is one of the main challenges due to strong van der Waals forces between nanotubes. In this study, a polycarboxylic ether based superplasticizer and ultra-sonication technique was used for dispersion of multi-walled carbon nanotubes (MWCNTs). Portland cement concrete specimens with different concentrations of MWCNTs (0.04 and 0.1 % by the weight of cement), with and without the presence of superplasticizer were investigated. Compressive strength test results revealed a significant improvement in mechanical properties of sample containing 0.1 % MWCNTs and 0.2 % superplasticizer. Moreover, field emission scanning electron microscopy (FESEM) images of fractured surfaces of hardened specimens showed a good dispersion of MWCNTs within the cement matrix. This method was developed to facilitate the uniform dispersion of MWCNTs in the cementitious concrete for better reinforcement in nanoscale and mechanical properties enhancement by transfer of load between the nanotubes and matrix.

An experimental investigation was presented in this paper on reinforced concrete box beams subjected to shear, torsion, and bending moment strengthened by carbon fiber reinforced polymer (CFRP). Eight box beams were cast and separated into two groups according to two different torque-to-shear and torque-to-bending moment ratios. Three box beams from each group strengthened by CFRP in different configurations and one control box beam were tested. The main parameters of this experiment were the different ratios and configurations, including U-jacket layers and U-jacket strips with or without longitudinal strips. The cracking and failure mode, effect of wrapping configuration, torsional capacity, and behavior of the different torque-to-shear and torque-to-bending moment ratios were studied in the paper.

Acoustic emission (AE) technique is one of the nondestructive evaluation (NDE) techniques that have been considered as the prime candidate for structural health and damage monitoring in loaded structures. This technique was employed for investigation process of damage in reinforced concrete (RC) frame specimens. A number of reinforced concrete RC frames were tested under loading cycle and were simultaneously monitored using AE. The AE test data were analyzed using the AE source location analysis method. The results showed that AE technique is suitable to identify the sources location of damage in RC structures.

Two groups of rectangular beams, comprising of six specimens, the first group (L) were provided with four longitudinal bars, one at each corner while the second groups of beams (S) were fully reinforced with longitudinal bars and transverse reinforcement. Each group consisted of three beams. Two beams have been strengthened with ultra high performance fiber concrete (UHPFC) on four sides having a thickness of (15mm - 25mm) and one control beam. The variables considered in the experimental study include the transverse reinforcement ratios and the effect of thickness of UHPFC wrap. Experimental results show the effectiveness of the proposed technique at ultimate torque for strengthening beams and behavioral curves. Strengthened RC beams fully wrapped with a thin layer of UHPFC exhibit an enhanced torsional strength when compared to control beam. Results reveal that the transverse reinforcement ratios by 0.66%, increases the UHPFC contribution to torsional strength of strengthened beams with a 15 thick UHPFC; and by up to 7% for strengthened beams with a 25 thick UHPFC, respectively when compared to same strengthened beams without stirrup. It is found that the ultimate torque of beams with a 25 mm thin layer UHPFC is greater than beams with 15 mm by (28% and 28.3%) for the groups L and S, respectively.