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Waste glass sludge (WGS), a byproduct of glass plate manufacture, was used to improve the durability properties of concrete under an environmental condition of freezing and thawing, with the existence of de-icing salts. A total of five concrete mix proportions were prepared, by varying the amounts of WGS. In order to observe the effects and roles of WGS on the durability performances of concrete mixtures, compressive strength tests, freezing and thawing tests, chloride ion penetration and surface scaling were carried out. Test results showed that the incorporation of WGS as a partial replacement for cement has beneficial effects on the compressive strength of concrete, especially when used together with fly ash. Moreover, WGS improved the resistance of freezing and thawing with and without de-icing salts, the chloride ion penetration and the resistance of surface scaling of the concrete compared to the control mixture containing 20% fly ash as cement replacement. [ABSTRACT FROM AUTHOR]

Abstract: The restrained ring test is becoming widely used as a standard test method to assess the potential for early-age cracking in concrete mixtures. Previous research focused on the development of analytical solutions for quantifying residual stress development in restrained ring specimens that either assumed that the ring was thin (i.e., a thin wall approximation) or that the shrinkage was uniform along the radial direction for a thick-walled ring. This paper presents an analytical solution to consider the influence of moisture gradients that occur when a thick-walled ring specimen dries from the outer circumference. Toward this end, the ring that dries from the outer circumference is treated as the superposition of a stress field that is caused by external restraint and a stress field that arises due to differential shrinkage. An analytical expression is presented to estimate the stress components. To assess the suitability of the analytical solution, it was compared with results from a finite element analysis and a reasonably good agreement was observed. [Copyright &y& Elsevier]

• Pore distribution in the interlayer analyzed using X-ray Computed Tomography. • Relationship between pore fraction and position of tensile bond fracture determined. • Tensile bond strength of 6.27% of compressive strength obtained. • Weakest layer occurred when tensile stress is perpendicular to printing direction. Recently, researches on additive manufacturing (AM) method have been actively carried out as the latest technique for building concrete structures in the construction field. It is known that the additive manufacturing method, also called 3D printing technique, is a method of constructing a structure by printing layers, and the adhesion strength in the interlayer between the layers plays a dominant role in the performance of the structure. In this study, we focused on the formation of interlayer of concrete structure built using additive manufacturing method. In this study, the position of the interlayer was analyzed using the computed tomography (CT) method and the correlation between porosity and tensile bond strength in the analyzed interlayer was tried. As a result of the CT analysis of 13 specimens extracted from the printed specimens, it was confirmed that the porosity was formed high in the interlayer. The porosity of the interlayer was at least 2.15% and 6.66% higher than the average porosity. After analyzing the porosity by CT, the tensile bond strength of the specimens was measured to confirm the tensile bond strength and location of the fracture surface. Tensile bond strengths were 2.58–3.77 MPa with an average of 2.80 MPa using 10 specimens. It was confirmed that all of the fracture surfaces occurred along the interlayer. It was confirmed that there was no correlation between the tensile bond strength and porosity of the test specimens used in this study. Six of the ten specimens failed in the other interlayer, but four specimens failed in the interlayer with the highest porosity. As a result of analysis of the fracture surfaces of six specimens without fracture at the highest porosity, the porosity at the fracture surface was 5.73–9.18%, which was higher by 0.6–3.3% than the average porosity. However, defects occurred during layer output were confirmed from the failure of six specimens. Through this study, we confirmed that the interlayer is the weakest when tensile stress is applied in the perpendicular direction of printing, and that it is necessary to review the defects when applying the printing method. [ABSTRACT FROM AUTHOR]

Strain rate-dependent shear behavior of ultra-high-performance fiber-reinforced concretes (UHPFRCs) with confining pressure was investigated using a new shear test setup in an improved strain energy impact machine (I-SEFIM). Different confining pressures were applied to the specimens prior to shear testing at both static and high strain rates, and were maintained during testing. The shear strength of UHPFRCs was highly sensitive to the applied strain rate and confining pressure. The effect of confining pressure on the shear strength was more pronounced at a static rate rather than at high strain rates. Strain rate-dependent shear failure surfaces of UHPFRCs were proposed. [ABSTRACT FROM AUTHOR]

• A cement hydration model to simulate the hydration of a CNT-reinforced cement paste. • The CNT dispersion algorithm was proposed to generate the pre-hydration model. • Multiphase voxels were proposed to consider the CNT in the CEMHYD3D. • Dissolution rates were proposed to consider accelerated or delayed hydration. • Simulation results are consistent with experimental results. The study proposed a cement hydration model based on multiphase voxels and a novel dissolution rate to simulate the hydration of a carbon nanotube (CNT)-reinforced cement paste. The proposed multiphase voxels and dissolution rates were validated by considering accelerated or delayed hydration owing to CNTs and superplasticizers. The model can simulate the formation of low-density and high-density calcium silicate hydrates (CSHs) using multiphase voxels and was validated using previous experimental data for cement pastes containing 0.05–0.25 wt% CNTs. The simulation results, including those on the heat flow and heat of hydration, are consistent with the experimental results. [ABSTRACT FROM AUTHOR]

Highlights: [•] The final goal is to develop a fiber reinforced concrete for containment buildings. [•] High rate tensile behavior of FRC was investigated. [•] Strain energy frame impact machine was used for tensile impact tests. [•] Different rate sensitivity of FRC was found according to the type fiber. [•] Adding more fibers by increasing S/a is positive for higher impact resistance of FRC. [ABSTRACT FROM AUTHOR]

• The proposed random distribution method was much saving-time than the correlation function method. • The surface area of silicate phases generated by the RD_13 and the CF methods were quite close. • There were in good agreement between the simulation results using the RD_13 method and experimental results in the OPC with w/c = 0.4 and 0.55. This study investigated the influences of cement particle distribution on the hydration process of cement paste using three-dimensional computer simulation. The pre-hydrated models of cement paste were generated by using both the correlation function (CF) method based on SEM images and the random distribution (RD) method. The hydration process of cement paste was simulated using the model based on the CEMHYD3D. The RD method was simpler and required less time in generating a pre-hydrated model than the CF method. In addition, the simulation results of the RD method were similar to those of the CF method in the properties of cement paste using the cement 133 with water-to-cement ratio of 0.3. Although the simulation results of the RD method was in good agreement with those of the CF method, authors highly recommended that the cement particles larger than a critical diameter (13 µm) in the simulation contain multiple cement crystalline phases whereas the other ones smaller than the critical diameter should contain a single phase. The proposed RD method was validated by using the previously reported experimental results using ordinary Portland cement as well. [ABSTRACT FROM AUTHOR]