Effects of Particle Size and Cement Replacement of LCD Glass Powder in Concrete

The high quality liquid crystal display (LCD) processing waste glass (LPWG) generated from the manufacturing process of Korea’s LCD industries, having the world’s highest technological level and production, was finely ground into particles smaller than cement particles (higher fineness than OPC) to verify their applicability and performance as a replacement for cement. For a concrete mix having a W/B ratio of 0.44, cement was replaced with LPWG glass powder (LGP) at ratios of 5, 10, 15, and 20% (LGP12) and 5 and 10% (LGP5) according to the particle size to prepare test cylinder specimens, which were tested with respect to air contents, slump in fresh concrete, and compressive strength and splitting tensile strength of hardened concrete. The microstructure of the concrete specimens was analyzed through Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX), and a Mercury Intrusion Porosimetry (MIP). Replacement of cement with LGP for cement could effectively decrease the quantity of cement used due to the excellent performance of LGP. It may positively contribute to the sustainable development of the cement industry as well as waste recycling and environment conservation on a national scale

Finite Element Modeling of Interface Behavior between Normal Concrete and Ultra-High Performance Fiber-Reinforced Concrete

The behavior at the interface between normal strength concrete (NSC) and Ultra-High Performance Fiber-Reinforced Concrete (UHPFRC) plays a crucial role in accurately predicting the capacity of UHPFRC for strengthening and repairing concrete structures. Until now, there has been a lack of sufficient finite element (FE) models for accurately predicting the behavior at the interface between NSC and UHPFRC. This study aims to investigate the structural behavior of composite members made of NSC and UHPFRC by developing a model that accurately simulates the interface between the two materials using a linear traction-separation law. Novel parameters for the surface-based cohesive model, based on the traction-separation model, were obtained and calibrated from prior experiments using analytical methods. These parameters were then integrated into seven FE models to simulate the behavior at the interface between NSC and UHPFRC in shear, tensile, and flexural tests. The accuracy of the FE models was validated using experimental data. The findings revealed that the proposed FE models could effectively predict the structural behavior of composite NSC-UHPFRC members under various working conditions. Specifically, the maximum deviations between EXP and FEA were 6.8% in ultimate load for the shear test and 15.9% and 2.8% in ultimate displacement for the tensile and flexural tests, respectively. The model can be utilized to design the use of UHPFRC and ultra-high performance fiber-reinforced shotcrete (UHPFRS) for repairing and strengthening damaged concrete structures

Global Sequence Homology Detection Using Word Conservation Probability

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Incorporating Liquid Crystal Display (LCD) Glass Waste as Supplementary Cementing Material (SCM) in Cement Mortars—Rationale Based on Hydration, Durability, and Pore Characteristics

This paper assesses the feasibility of using liquid crystal display (LCD) waste glass as a supplementary cementing material in cement mortars. Two different sizes of LCD waste glass powder (LGP) particles were used (5 µm and 12 µm) with two substitution levels with cement in mortar (10% and 20%). The resulting mortars were evaluated for strength, hydration, porosity and durability through various experimental techniques. It was found that LGP particles lead to appreciable strength gain at all ages in comparison with control mortar, especially significant strength gain of 18% was observed at 28-day. This is attributed to the greater gel-space ratio as corroborated by the experimental determination of porosity, which is found less for LGP-incorporated mortars as compared to control cement mortar. The smaller particle size of LGPs not only accelerates the pozzolanic reaction in alkaline cementitious matrix, but also fills the smaller pores, thus reducing porosity and contributing to strength gain. Increased hydration was also elucidated qualitatively by backscattered electron imaging. Due to the increased hydration in LGP-incorporated pastes and mortars, the durability (in terms of chloride ion permeability) has also been found improved. Thus, it is established that 10% (by weight) of cement can be replaced with 12 μm LGP, whereas 20% can be replaced with 5 μm LDP for improved strength and durability. Incorporating LCD waste in mortars and concretes as partial replacement of cement can not only help utilize this potentially hazardous waste, but also significantly reduce the associated carbon dioxide emissions, thus promoting sustainable development

Determining the Fracture Process Zone Length and Mode I Stress Intensity Factor in Concrete Structures via Mechanoluminescent Technology

The mechanoluminescent (ML) technology that is being developed as a new and substitutive technology for structural health monitoring systems (SHMS) comprises stress/strain sensing micro-/nanoparticles embedded in a suitable binder, digital imaging system, and digital image processing techniques. The potential of ML technology to reveal the fracture process zone (FPZ) that is commonly found in structural materials like concrete and to calculate the stress intensity factor (SIF) of concrete, which are crucial for SHMS, has never been done before. Therefore, the potential of ML technology to measure the length of the FPZ and to calculate the SIF has been demonstrated in this work by considering a single-edge notched bend (SENB) test of the concrete structures. The image segmentation approach based on the histogram of an ML image as well the skeletonization of an ML image have been introduced in this work to facilitate the measurement of the length of ML pattern, crack, and FPZ. The results show ML technology has the potential to determine fracture toughness, to visualize FPZ and cracks, and to measure their lengths in structural material like concrete, which makes it applicable to structural health monitoring systems (SHMS) to characterize the structural integrity of structures

Analytical Investigation of the Flexural Capacity of Precast Concrete Frames with Hybrid Joints

This study aims to evaluate flexural strength based on the inelastic neutral axis calculated from all stress states of the proposed precast composite columns with hybrid beam-column joints, which facilitate the erection of concrete precast frames in a similar manner to that used for steel frames. It was also shown analytically that hybrid joints with headed studs contribute significantly to the flexural moment capacity and effectively increase the flexural structural performance of precast composite columns. The strain compatibility-based analytical results were compared with test data, showing results with an error of less than 8% at the critical section for the maximum load limit state of specimens. It is observed that the strength contributed by steel sections and headed studs increased by 30% and 35% at the yield limit state and maximum load limit, respectively, reducing the dependence on rebars. The total contribution of the headed studs was as large as 12.2% (average of the two layers of headed studs) at the maximum load limit state, whereas the strength provided by the tensile rebars decreased from 90.5% to 63.9% for the specimen with headed studs at the maximum load limit state

Synergistic Benefits of Using Expansive and Shrinkage Reducing Admixture on High-Performance Concrete

High-performance concrete (HPC) is widely used in construction according to great mechanical properties, but it has a high risk of shrinkage cracking due to autogenous shrinkage stress. Therefore, the aim of this research was to investigate the effect of a combination of expansive admixture (EA) and shrinkage reducing admixture (SA) on the autogenous shrinkage of high-performance concrete without heat treatment. Two different EA to cement weight ratios of 0.0, 5.0%, and two different SA to cement weight ratios of 0.0, and 1.0% were combined and considered. To investigate the differences in the time-zero conditions effect on the autogenous shrinkage behaviors, four different initial points were compared. The test results indicate that the EA and/or SA content was conductive to a little bite increase compressive strength (22.6⁻37.9%) and tensile strength (<4.8%). According to the synergistic effect of the EA and SA on the HPC, the autogenous shrinkage significantly decreased (<50%), as compared to those specimens with only one type of admixture (EA or SA). Furthermore, all the specimens incurred restrained autogenous shrinkage cracks at an early age, except the specimen using the combined EA and SA. Therefore, it can be concluded that the combination of EA and SA is effective for improving the properties of HPC