International Journal of Microstructure and Materials Properties (8 papers in press)
Special Issue on: The Impact of Nanomaterials in Smart Construction Materials
Accurate prediction of nano impermeability and antifreeze concrete ratio in high-rise buildings
by Xiaolei Wu
Abstract: In order to solve the problem of large error between the ratio prediction result and the actual value in the traditional method, an accurate ratio prediction method of nano frost resistant concrete for high-rise buildings is proposed. The NPCA method is used to eliminate the abnormal data, the principal component analysis method is used to obtain the data combination and its score vector and load vector at each time point, and the weight in the structure is updated in the form of top-down to obtain the effective characteristics of the data, so as to realise the accurate prediction of concrete ratio. The simulation results show that the difference between the predicted value and the measured value of this method is small, and the RMSE value is low, indicating that its prediction accuracy is high, which verifies the effectiveness of this method in concrete proportioning prediction.
Keywords: frost resistant concrete; proportioning prediction; NPCA method; DBN algorithm; sliding window residual statistical method.
Modeling study on the influence of nano admixture on the strength of high-rise building concrete
by Jipeng Liu, Fang Yan
Abstract: To solve the problem of high prediction error of concrete strength in traditional methods, a modeling method of the influence of nano admixtures on the strength of high-rise building concrete is proposed. UHPC concrete was selected as the test object to prepare different test blocks. Establish the concrete strength prediction model based on RBF network, optimize the prediction model, obtain the multivariate nonlinear model, input the material preparation data of nano admixture into the model, output the concrete strength prediction results, and complete the analysis of the impact of nano admixture on concrete strength. The test results show that the compressive strength of concrete reaches the best when the nano content is 1%; When the content of nano admixture is 30%, the flexural strength of concrete is the best; When using this method to predict the strength of concrete test block, the minimum prediction error is only 0.5%.
Keywords: nano admixture; concrete strength; compressive strength; flexural strength; multivariate nonlinear model.
Fatigue damage identification method of cement-based nanocomposites based on strain mode
by Changsheng Wang
Abstract: In order to overcome the problems of low sensitivity, low accuracy and long time of traditional methods, a fatigue damage identification method for cement-based nanocomposites based on strain mode was designed in this paper. On the basis of calculating the stress concentration coefficient, the mode decomposition method is used to traverse the stress wave and obtain the new stress value. Then, the propagation process of material fatigue damage is separated by the number of load cycles, and the fatigue damage evolution equation is established. Finally, combined with the ultrasonic wave equation, the location and magnitude of fatigue damage are identified according to the position and amplitude of reflected wave. Experimental results show that the proposed method has the highest sensitivity of 0.944, the highest damage identification accuracy of 97.72%, and the minimum identification time is only 11s, indicating that the proposed method has high reliability and timeliness.
Keywords: cement-based nanocomposites; strain response coefficient; strain modal decomposition; fatigue damage accumulation; damage identification.
Experimental analysis on crack resistance of plant nanofiber concrete under dry and cold environment with large temperature difference
by Lijun Yin
Abstract: In order to analyse the crack resistance of plant nanofiber concrete in the environment of large temperature difference between dry and cold, plant nanofiber concrete is prepared through experiments, and the compressive strength is analysed as the test index. Prepare straw based nanofibers, analyse their structural properties and internal structure, analyse the change of pore negative pressure value of plant nanofiber concrete, obtain the water evaporation in the pores of materials under dry and cold conditions, and determine the factors affecting the crack resistance of plant nanofiber concrete. Calculate the compressive strength and flexural strength of plant nanofiber concrete, and complete the crack resistance analysis of plant nanofiber concrete. The experimental results show that the compressive strength of concrete increases with the increase of the nano content of plant cellulose in the range of 0 ~ 1.5% of the mass fraction of concrete.
Keywords: dry and cold environment with large temperature difference; plant nanofibers; crack resistance; pore negative pressure value; compressive strength.
Study on improvement effect of waterborne two-component polyurethane on radioactive pollution of building decoration materials
by Yan Zhang
Abstract: In order to improve the removal effect of radioactive concentration of building decoration materials, this paper improves the radioactivity of building decoration materials by preparing waterborne two-component polyurethane coating and coating it on the surface of building decoration materials.The reaction mechanism of two-component waterborne polyurethane was analyzed. The content of -NCO in prepolymer samples at a certain time point was determined by Hydrochloric acid - din-butylamine method. The waterborne two-component polyurethane coating was prepared based on IPDI based curing agent and coated on the surface of radioactive building decoration materials to effectively reduce the radioactivity of building decoration materials, Realize the improvement of radioactive pollution of building decoration materials.The experimental results show that the radioactive concentration of building decoration materials treated by this method is only 2.86bg/kg. This method can improve the radioactive pollution of building decoration materials.
Keywords: IPDI based curing agent; waterborne two-component polyurethane; radioactivity; building decoration materials; hydrochloric acid; NCO.
Study on microstructure evolution and toughening of coarse grain heat affected zone of 690 MPa grade bridge steel
by Xuming Wang, Aimin Zhao, Yishun Zhang, Yue Zhang, Zhiyi Bao
Abstract: Using Gleeble-3500 to simulate the coarse-grain heat affected zone (CGHAZ) under different heat inputs (HIs) (15~50 kJ/cm), the welding performance of 690 MPa bridge steel was investigated. Optical microscope (OM), scanning electron microscope (SEM) and electron back-scattering diffraction (EBSD) were used to analyse the microstructure. The mechanical properties were researched by Charpy V-notch test and microhardness test. The results indicate that under different HIs conditions, the microstructure of CGHAZ obtained by simulation is mainly composed of granular bainite (GB), lath bainite (LB)and slight of martensite. As the HIs increases, the martensite content in the microstructure decreases, the content of granular bainite increases. When the HIs is 30 kJ/cm, the obtained microstructure of simulated CGHAZ is mainly LB, with the highest density of large-angle grain boundaries (orientation difference greater than 45 ), resulting the highest impact absorbed energy.
Keywords: grade bridge steel; heat input; coarse graine heat affected zones; microstructure; mechanical properties.
Study on micro compression characteristics of nano carbon fibre reinforced concrete
by Peipei Chen, Aina Qi
Abstract: In order to solve the problem of large error of analysis parameters in the existing research methods of micro compression characteristics of materials, a new research method of micro compression characteristics of nano carbon fibre reinforced concrete is proposed in this paper. Firstly, relevant instruments and materials are selected to prepare nano carbon fibre reinforced concrete. The water adsorption capacity, flexural strength, splitting tensile strength and toughness of concrete surface are calculated, and the characterisation of nano carbon fibre reinforced concrete is analysed. Finally, the micro compression strain distribution characteristics of nano carbon fibre reinforced concrete are determined, and the micro compression characteristics are studied. The experimental results show that this method can effectively analyse the micro compression characteristics of nano carbon fibre reinforced concrete, and the maximum error of characteristic analysis is no more than 10%.
Keywords: concrete materials; micro compression characteristics; Lambert Beer’s law; water adsorption capacity; Kachanov model.
Mechanical properties and crack detection method of nano concrete
by Na Guo, Jiajia Guo
Abstract: In order to test the mechanical properties of nano concrete, this paper takes the shear strength as an example and finds that the shear upper limit value of nano concrete will increase with the increase of its strength. But when the strength level reaches about 30 MPa, the increase rate of the shear upper limit begins to slow down. In view of the concrete cracking problem caused by environmental factors, based on the calculation of the stress load of nano concrete, the paper divides the cracking area by establishing the damage model of nano concrete, and then detects the cracking situation accurately by means of two-dimensional image processing. Experiments show that the detection process of this method needs less time, and its detection accuracy can reach 98.89%. The maximum and minimum leakage detection rates are 4.68% and 3.35%, indicating that this method can accurately detect the cracking of nano concrete.
Keywords: nano concrete; mechanical property; wing plate; resistance to shear; crack detection.