Key Engineering Materials Vol. 894

Abstract: The research of Janus colloidal particles has attracted much attention in recent years because of its huge prospects and applications in materials, chemicals, medicine, catalysis, etc. In order to reduce the cost of conducting experiments, the method of molecular dynamics simulation is used to conduct research on Janus particles. However, the current related simulation study lacks the visualization, dynamization and three-dimensionalization of the Janus particle simulation process. Therefore, the author simulates the free diffusion process of two kinds of Janus particles by using 3D visualization dynamic molecular dynamics related software in this paper. By analyzing the influence of the related parameters of particles and droplet on the diffusion process, new directions of the researches about the simulation of Janus particles can be proposed. The simulation results show that the size of the droplet, the position where the droplet is added to the solution, and the mass of the particles will affect the diffusion process rate of the particles in the droplet in the surrounding solution.

Abstract: This research mainly focused on the properties of decorative white cement tiles which made from waste glass and white cement. The ratio of waste glass powder and white cement were studied at 10 : 90, 15 : 85, 20 : 80, 30 : 70, 40 : 60, 50 : 50, 60 : 40 and 70 : 30 by using water content at 30 %wt. All components were mixed and cast into the mould. Decorative white cement tiles were curing at 14, 21 and 28 days. In order to characterize physical and mechanical properties, all tiles were measured density, water absorption and compressive strength. According to the results, it can be obviously seen that density increased and water absorption decreased with increasing waste glass powder content. The highest compressive strength of around 36.5 MPa was found at 20 %wt of waste glass powder. However, compressive strength decreased with increasing waste glass powder over 20 %wt (waste glass powder 20: white cement 80). It was found that the lowest compressive strength of around 30.58 MPa was found at 70 %wt of waste glass powder. Curing time also affected properties as it was found that increasing curing time to 28 days resulted in increasing of density and compressive strength. In order to study how long does essential oil last on decorative white cement tiles, the orange essential oil at 1, 5 and 10 %wt were added into the white cement paste by using waste glass powder : white cement at 20 : 80 with 30 %wt of water. Decorative white cement tiles were smelled by 30 people every morning for 30 days and it can be found that 10 %wt of orange essential oil last longest on the decorative white cement tiles with 22 days.

Abstract: In this research, a sustainable approach is followed to develop efficient mixtures incorporating recycled fine aggregate (RFA) remained from structure demolition as well as limestone filler (LF) from production of hot mix asphalt (HMA). The LF is a byproduct of the drying process in HMA production plant which is not entirely consumed in the production of the HMA and must be hauled and disposed in landfills. The maximum particle size of the LF is approximately 40 µm. Self-Compacting Concrete (SCC) mixtures were designed replacing 5% and 10% of the cement with LF. Incorporation of 50%, and 100% RFA with the fines in the mixtures were considered with and without addition of the LF. Due to the formwork and prefabrication restrictions, the paste volume and the high range water reducer content were tuned in such a way that the slump flow of the mixtures remained between 660 mm to 700 mm without segregation. Durability and mechanical performance of the mixtures were evaluated by resistance against freeze-thaw scaling exposed to deicing agents and compressive strength. It was observed that the SCC mixtures containing 10% LF outperformed those without the use of LF while 5% SCC mixtures did not exhibit tangible superiority. Incorporation of RFA as the fine fraction degraded the durability of all the mixtures. While replacing all the fine fraction with RFA significantly impaired durability and compressive strength, 50% RF mixtures could be designed containing 10% LF that remained in the allowable limits.

Abstract: A support vector machine (SVM) is widely used for predicting the properties of fly ash blended concrete. However, the studies about the optimal design of fly ash blended concrete based on SVM are very limit. This study shows an SVM-based optimal design procedure of fly ash blended concrete. First, we built an SVM model and evaluated the compressive strength of fly ash blended concrete considering the effects of water to binder ratio, fly ash replacement ratio, and test ages. Second, we made parameter studies based on the SVM model. The parameter studies show that fly ash can improve the late age strength of concrete. This improvement is obvious for concrete with lower water to binder ratio. The optimal fly ash replacement ratio increases as the water to binder ratio decreases.

Abstract: In a previous research by authors, a methodology was developed to derive J-R curves for Hot Mix Asphalt (HMA) mixtures using an elastic-plastic approach where a comprehensive understanding of crack propagation regime could be achieved. In this research, the effect of crumb rubber modification of HMA binder is studied in terms of R-curves and crack propagation at low temperatures. Mode I Single edge notched beam (SE(B)) fracture tests were conducted in temperature levels of 0 °C, -10 °C, and -20 °C. PG58-22 and PG64-22 binders were used in the fabrication of HMA samples. Modified specimens consist of 20% crumb rubber along with the incorporation of 3% warm mix admixture. Crack growth resistance curves were obtained in SE(B) tests by means of image processing and recording of the progressive crack length. Elastic-plastic J-R curves revealed that crumb rubber modified mixtures exhibit higher crack growth resistance for each bitumen performance grade. As well, increased ductility and cohesive energy can be observed according to the R-curves as the mixtures are modified by crumb rubber.

Abstract: With no beams, reinforced concrete flat slab buildings are typically built to advance urban growth and to meet the architectural needs of large spans and low storey heights. Its behaviour to avoid a progressive collapse must therefore be investigated. In this research, the progressive collapse resistance of six-storey RC flat slab buildings with varying span lengths and floor heights is assessed by subjecting the building to three different instances of instantaneous removal of columns in the first storey, performing dynamic progressive collapse analysis as per GSA guidelines, and comparing the evaluated joint displacements and chord rotations at column removal locations with the permissible chord rotation for flat slab buildings as per DoD guidelines. The results have shown that the studied flat slab building with all different span lengths and floor heights is prone to progressive collapse. It is also observed that the vertical displacements and chord rotations at column removal positions increase as the span lengths and storey heights are increased alternately.

Abstract: A meso-analysis method which is derived from the base force element method (BFEM) was proposed for recycled aggregate concrete (RAC). A simple algorithm was used to generate the convex recycled concrete aggregate (RCA) model. Uniaxial compression numerical simulations were carried out on the numerical specimens with different replacement rates of RCA. The model predictions were in a good agreement with the test results. The proposed method is very promising. It can totally predict the full stress-strain curve of RAC, as well as the failure process and failure mode, including strain softening and strain localization.

Abstract: This paper conducts surveys on the design, construction and use of the ICF system, a new type of low-energy and industrialized house that has emerged in Guanzhong rural area of China in recent years. The survey content includes family background, house layout design, construction and cost, details and energy consumption simulation, temperature test etc. The paper summarizes the reasons for the popularity of the ICF system and the issues that need attention in future promotions. Construction optimization is also proposed for thermal bridge at the window opening, so that this new system can exert a more comprehensive energy-saving performance.

Abstract: With the OPC industry being responsible for the 8% of CO₂ global emissions, alternative, eco-friendly building materials, called geopolymers, have been in the center of research interest. Their broader use is limited due to the concentrated alkali solution that is involved in the synthesis process. In this study, a wide range of solid reagents are tested for the development of solid mixtures with suitable alkali and silica content that will substitute the corrosive activation solution. One-part geopolymers were synthesized using Greek fly ash as the aluminosilicate precursor. The produced samples were appropriately characterized by XRD, FTIR and SEM analytical techniques while the mechanical performance was evaluated through uniaxial compressive strength measurements. One-part geopolymers using anhydrous sodium silicates with molar ratios SiO₂/Na₂O ≤ 2 as solid activators, can successfully substitute the activation solution since they achieve identical mechanical performance to that of the two-part geopolymers (≥ 60 MPa).