Abstract: The primary problem of eco-materials is how to judge whether a material is environmentally friendly or not, and the method of life cycle assessment is usually used to evaluate it. The depletion of mineral resources is a very important indicator of LCA, but its characterization is still filled with dispute. At present, the most commonly used method is CML, which is put forward by Leiden University, and its core idea is that using the ratio of exploitation amount and reserves of mineral resources as the degree of scarcity. Although being accepted by most of the scholars at work on LCA, CML doesn’t grasp the essence of the depletion of mineral resources. Recently, a new assessment method, injecting new ideas to the conventional life cycle assessment, combines exergy with LCA is arising, which can be used to solve some specific problems of LCA especially the depletion of mineral resources. In this paper, two results of elements’ exergy calculated by Rivero and Szargut respectively are compared, and the exergy of some natural minerals, which can be used in LCA and other minerals-related research, is calculated based on the data of Chinese mineral resources.
Abstract: The amount of CO2 emissions from steelworks accounts for a great share of the total CO2 emissions from industry in China. Thus, reducing CO2 emissions from steelworks is urgent for China’s environmental protection and sustainable development. This study aims at identifying factors that influence CO2 emissions from steelworks and proposing measures to reduce CO2 emissions. The life cycle inventory (LCI) of iron and steel products implies the relationship between the CO2 emissions of the steelworks and the input variables of the LCI. The Tornado Chart Tool is utilized to calculate the variation of CO2 emissions caused by the change of each input variables of LCI. Then, mean sensitivity of each input variable is calculated and the ranking criterion developed is used to identify the main factors influencing the integrated steelworks. Subsequently, measures for reducing CO2 emissions are proposed. The results indicate that the very important influencing factors of CO2 emissions in steelworks are the CO2 emission factor of Blast Furnace Gas (BFG), liquid steel unit consumption of continuous casting, continuous casting slab unit consumption of hot rolling and hot metal ratio of steelmaking. Consequently, many efficient measures for reducing CO2 emissions have been proposed, such as removing CO2 contained in BFG, decreasing the hot metal ratio of Basic Oxygen Furnace (BOF), recycling BFG, optimizing the products’ structure, etc.
Abstract: In order to essentially improve interfacial transition zone between cement paste and aggregate, the concept and ideal model of function aggregate are developed. Function aggregate is composed of a porous matrix with high strength and low water absorption, and a coating layer which can hydrate in cement paste. It can improve ITZ between aggregate and cement paste and control curing range of cement paste. Based on optimization of raw materials and processing techniques, high strength aggregate with low absorption and minor C2S and C4AF phase in coating layer is acquired. Results indicate that cordierite is formed in aggregate when MgO content reaches 2%, and it shows that the presence of cordierite minimizes the potential for micro-crack formation, thus decreases water absorption.
Abstract: Copper doped TiO2 nanoparticles were synthesized by hydrolysis of tetrabutyl titanate (Ti(OBu)4) and copper nitrate (Cu(NO3)2) in water-in-oil (W/O) microemulsions, consisting of water, Triton X-100, n-hexanol, cyclohexane and water. In this W/O system, Trinton X-100, n-hexanol and cyclohexane were used as surfactant, co-surfactant and organic solvent, respectively. The prepared nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). The results show that the Cu-doped TiO2 nanoparticles synthesized by this method have a good dispersion character and relatively small sizes of about 80 nm. The XRD results show that the calcination temperature greatly influences the crystallization transformation. When calcined below 550 °C, the prepared sample is composed of anatase structure. When the calcination temperature increases to 650 °C, rutile phase appears besides the anatase phase. While doping amount has little effects on crystal phase. FTIR analysis indicates that most of the contained water and the residual organic surfactants can be removed by calcination.
Abstract: In this paper both the NaCl immersion and the co-action of load and NaCl solution immersion were employed to analyze the wet adhesive property and resistance of chlorion diffusivity of two types of linear polyaspartic ester (PAE) polyureas coated concrete: B2（PAE-b-H12MDI prepolymerH66）coated concrete and F2（PAE-f-H12MDI prepolymerH62） coated concrete. The research on the adhesion of B2 and F2 coated concrete showed that the adhesion were about 2N/mm and 1.5N/mm respectively before exposure, and the adhesion reduced about 6.8% and 11.8% respectively after 10% NaCl immersion for 300 days and made 8% and 5% further decrease under the co-action of load and NaCl solution immersion, double-factor exposure for 300 days. Compared with single NaCl solution immersion, the co-action of load and NaCl solution immersion also had more influence on the chlorion diffusivity of the coated concrete. The average chlorion content of B2 and F2 coated concrete increased about 19-21%, and the diffusion coefficient of chlorion of B2 and F2 coated concrete was 10－13-10－14m2/s, due to the micro-crack of concrete in tensile area increased under bending load, accelerating chlorion diffusion and permeation. The research showed that chlorion diffusion behaviour of B2 and F2 coated concrete under the NaCl immersion and the co-action of load and NaCl solution immersion satisfied second Fick’s law.
Abstract: In this paper the effect of curing temperature on the morphology and properties of PAE based polyureas were evaluated using FTIR, AFM and electrochemical impedance spectroscopy (EIS). The PAE based polyureas were prepared from synthesized PAE chain extenders and hexamethylene diisocyanate（HDI）trimer/polytetramethylene ether glycol (PTMG) prepolymer. The morphology and properties were investigated through FTIR, EIS and atomic force microscope(AFM). The results indicated that curing temperature has a great influence on morphology and properties of the polyureas. FTIR studies showed that hydrogen-bonded urea carbonyl are increased from 74.3% to 82.1%, and the length of hydrogen bonding were decreased from 0.307 nm to 0.303 nm while curing temperature were increased from 20°C to 80°C. FTIR experimental studies indicated that the degree of hydrogen-bonded –NH groups and urea carbonyl groups increased while curing temperature increased, as a consequence, intermolecular force enhanced. The AFM was applied to study the topography of PAE based polyureas for the first time,and the microphase separation phenomenon of the PAE based polyureas were observed directly through AFM topography studies. AFM studies confirmed that the compatibility of soft and hard segment decreased and microphase separation degree increased while the curing temperature increased. The EIS studies indicated that during 90 days immersion, the resistance of 20°C cured samples changed obviously higher than 80°C cured ones. The results showed that much corrosion medium permeated into the coatings, and the corrosion resistance of 80°C cured PAE based polyureas exhibited a higher EIS features and a better corrosion resistance than the 20°C cured ones. The effect of curing temperature on EIS properties of PAE based polyureas could be confirmed by FTIR and AFM morphology studies.
Abstract: A new robust numerical technique was proposed for analyzing chloride transient diffusion in concrete with non-homogenous coefficient. The method was based on a meshless boundary element method which results in an integral equation for explicitly evaluating field chloride quantities. Weighted residual method and Green’s function were adopted to derive domain and boundary integral equations. A radial integration method coupling with radial basis function approximation technology was used to convert domain integral into equivalent boundary integral. With central finite difference method, an explicit time iteration scheme was established for solving transient diffusion equation. Two numerical examples for 2D diffusion problem were given to demonstrate the robustness of the proposed method. Numerical results show that the non-homogenous diffusion coefficient causes the chloride distribution non-uniform, and the diffusion process is nonlinear with respect to time.
Abstract: In this paper, a novel constitutive model of concrete has been proposed by introducing a new parameter, namely, cracking Poisson’s ratio (νcr), to account for the effect of localization due to cracking. By fitting the curve between the dimensionless strain (ε/εpr) and cracking Poisson’s ratio (νcr), νcr can be expressed as an 3rd order polynomial function of dimensionless longitudinal strain (ε/εpr). The constitutive model for the softening regime can then be proposed with the parameters of dimensionless strain and cracking Poisson’s ratio. Finally, Validity of the proposed model is verified by the test results of cylinder specimens of C30.
Abstract: Since meso-structure of plain concrete can not be observed directly, numerical simulation is the main approach to obtain the model coincident with the real structure on statistics. By applying the discrete element method, we have developed the 3D dynamic simulation for random aggregate model of plain concrete. According to the real ration of mass, the spatial positions of aggregate have been obtained, which is more close-grained compared with the random-distributed models based on Monte Carlo method. Compared with the geometrical generating algorithm for 2D random polyhedral aggregate, the algorithm for 2D or 3D random polyhedral aggregate is simpler. The results are the foundation for further studying the interface fracture and chloride diffused channels.