Repairing of Macroscopic Ceramic Cracks by Tiny Expansion Filling Composites

Using SiC, Al, Al_2O_3, ZrO_2 and Y_2O_3 as raw materials, based on chemical reactions those can cause expansion effect to compensate for the sintering shrinkage at elevated temperature among them, such as Al oxidizes to Al_2O_3, SiC converts to SiO_2, and their reaction productions react further to form mullite (3Al_2O_3·2SiO_2), a sort of tiny expansion composites were prepared and designed which can be used to repair macroscopic cracks of sintered ceramics. The total expanding extent can be adjusted by proportion of raw materials or control of sintering temperature. Filling this expandable ceramic ingredient in cracks of real ceramic part in a designed paste state, cracks could be repaired by a re-sintering process.

Influence of Mineral Admixtures on the Electrodeposition Healing Effect of Concrete Cracks

Two types of solutions（Zn SO4, Mg SO4） were selected to study the influence of mineral admixtures on the electro-deposition healing effect of concrete cracks. Four parameters（i e, rates of weight gain, surface coating, crack closure and crack filling depth） were measured. The mineral composition of electro-deposits in the cracks was analyzed. The study shows that the healing effect of mortar specimens with 10% fly ash is the worst, while the healing effect of mortar specimens with 20% fly ash is better than that of the specimens without fly ash. The rates of weight gain, surface coating, crack closure and crack filling depth decrease with increasing content of the ground granulated blast-furnace slag（GGBS）. The mineral admixtures have no influence on the composition of deposits.

Influence of Additives on the Formation of Electrodeposits in the Concrete Cracks

The electrodeposition method for rehabilitation of the cracked reinforced concrete,based on the electrochemical technique,was presented here.The aim of this study was to evaluate the influence of additive on the formation of electrodeposits in the concrete cracks.Cracked mortar specimens of size 40 mm×40 mm×160 mm were immersed in electrolyte solutions（ZnSO4,MgSO4）,and a constant current was applied between the reinforced steel and the external electrode for 15 days.Rate of surface coating,rate of crack closure and rate of crack filling depth were measured and the appearance of electrodeposits in the cracks was observed.The experimental results demonstrate that,under the experimental conditions,rate of surface coating and crack filling depth increase,while rate of crack closure decreases as the percengtage of additive increases.In addition,the electrodeposits become more denser and the microstructure varies with additive content,while the compositions of electrodeposits do not change.

Fundamental Research of Repairing Macroscopic Cracking of Ceramic by Directed Metal Oxidation Method

This study focused on testing the possibility of formation of alumina ceramic phase using aluminum/alumina mixture with other low content sintered at high temperature. It was found from XRD and SEM that aluminium is oxidized to alumina completely and the samples formatted ceramic phase accompanying minute expansion. This research supplies a new method of repairing macroscopic cracking of ceramic.

Effect of Pulse Parameters on Deposition in Concrete Crack using Pulse Current Electro-deposition

To evaluate the effect of pulse parameters on the formation of electrodeposits in concrete cracks, five different types of pulse current were set up, and ZnSO_4 and MgSO_4 solutions were used as the electrolytes. The rate of weight gain, rate of surface coating, rate of crack closure and crack filling depth were measured. Scanning electron microscopy was used to assess the morphology of the electrodeposits, and energy dispersive spectroscopy was used to analyze the mineral composition of the electrodeposits in the cracks. The experimental results demonstrate that, among five different pulse parameters, when T_（on）/T_（off）=0.8 ms/0.8 ms, the healing effect of electro-deposition is the best. The pulse mode hardly affects the mineral composition of the electrodeposits but changes the micromorphology. In addition, for both ZnSO_4 and MgSO_4 solutions, when T_（on）/T_（off）=0.8 ms/0.8 ms, the crystal structure of the electrodeposits is the most uniform and the densest.

Analysis and Modeling of Friction Stir Processing-Based Crack Repairing in 2024 Aluminum Alloy

Abstract A friction stir processing-based method was used to repair cracks in the 2024 aluminum alloy plates. The temperature field and plastic material flow pattern were analyzed on the basis of experimental and finite element simulation results. Microstructure and tensile properties of the repaired specimens were studied. The results showed that the entire crack repairing was a solid-phase process and plastic materials tended to flow toward the shoulder center and then resulted in the repairing of cracks. Meanwhile, the coarse grain structures were refined in repaired zone （RZ）, while the grains in thermal-mechanically affected zone and heat-affected zone were elongated and driven to grow up. Meanwhile, large phases are crushed into small particles and dispersed inside the RZ. Finally, the strength of the repaired specimens can be restored dramatically and their ductility can be partially restored. After heat treatment, the tensile properties of the repaired specimens can be further enhanced.

Computer-vision-guided semi-autonomous concrete crack repair for infrastructure maintenance using a robotic arm

Engineering inspection and maintenance technologies play an important role in safety,operation,maintenance and management of buildings.In project construction control,supervision of engineering quality is a difficult task.To address such inspection and maintenance issues,this study presents a computer-vision-guided semi-autonomous robotic system for identification and repair of concrete cracks,and humans can make repair plans for this system.Concrete cracks are characterized through computer vision,and a crack feature database is established.Furthermore,a trajectory generation and coordinate transformation method is designed to determine the robotic execution coordinates.In addition,a knowledge base repair method is examined to make appropriate decisions on repair technology for concrete cracks,and a robotic arm is designed for crack repair.Finally,simulations and experiments are conducted,proving the feasibility of the repair method proposed.The result of this study can potentially improve the performance of on-site automatic concrete crack repair,while addressing such issues as high accident rate,low efficiency,and big loss of skilled workers.