In this paper, the effect and mechanism of calcareous stone powder with size less than 0.074 mm are investigated in stone chippings concrete. The results show that the stone powder can participate in hydration reactio...In this paper, the effect and mechanism of calcareous stone powder with size less than 0.074 mm are investigated in stone chippings concrete. The results show that the stone powder can participate in hydration reaction and acts as crystal nucleus in hydration process, namely, it has hydration activity to an extent. The strength of stone chippings concrete is enhanced and the easy-mixing capacity of the concrete mortar is modified when stone chippings contain a proper amount of stone powder. The stone powder has little effect on the wearability of the concrete.展开更多
The stone chip resistance performance of automotive coatings has attracted increasing attention in academic and industrial communities.Even though traditional gravelometer tests can be used to evaluate stone chip resi...The stone chip resistance performance of automotive coatings has attracted increasing attention in academic and industrial communities.Even though traditional gravelometer tests can be used to evaluate stone chip resistance of automotive coatings,such experiment-based methods suffer from poor repeatability and high cost.The main purpose of this work is to develop a CFD-DEM-wear coupling method to accurately and efficiently simulate stone chipbehaviorof automotive coatings inagravelometer test.Toachieve this end,an approach coupling an unresolved computational fluid dynamics(CFD)method and a discrete element method(DEM)are employed to account for interactions between fluids and large particles.In order to accurately describe large particles,a rigid connection particle method is proposed.In doing so,each actual non-spherical particle can be approximately described by rigidly connecting a group of non-overlapping spheres,and particle-fluid interactions are simulated based on each component sphere.An erosion wear model is used to calculate the impact damage of coatings based on particlecoating interactions.Single spherical particle tests are performed to demonstrate the feasibility of the proposed rigid connection particle method under various air pressure conditions.Then,the developed CFD-DEM-wear model is applied to reproduce the stone chip behavior of two standard tests,i.e.,DIN 55996-1 and SAE-J400-2002 tests.Numerical results are found to be in good agreement with experimental data,which demonstrates the capacity of our developed method in stone chip resistance evaluation.Finally,parametric studies are conducted to numerically investigate the influences of initial velocity and test panel orientation on impact damage of automotive coatings.展开更多
In this paper, the technical research on the application of stone chips in wet-mixed shotcrete is carried out. By comparing the consistency, initial setting time, final setting time, strength, rebound rate, project co...In this paper, the technical research on the application of stone chips in wet-mixed shotcrete is carried out. By comparing the consistency, initial setting time, final setting time, strength, rebound rate, project cost and other indicators of wet-mixed shotcrete with natural sand and stone chips, the technical and theoretical feasibility of stone chips based wet-mixed shotcrete is determined. Through indoor raw material quality analysis, mix proportion design and verification, and project site construction effect verification, the results are good. First, the fineness modulus and gradation range of raw materials of natural sand and stone chips are basically the same, the particle shape is different, and internal friction and bonding are good. Secondly, the mix proportion, sand ratio and water-binder ratio of natural sand and stone chip-based sprayed concrete are the same, and the mixing time of stone chip-based sprayed concrete needs to be prolonged by 15S. Thirdly, according to the characteristics of stone chip-based shotcrete, such as strong cohesive force and low rebound rate, the thickness of single shotcrete can reach 100mm for the vault and 120mm for the side wall, thus improving the working efficiency.展开更多
文摘In this paper, the effect and mechanism of calcareous stone powder with size less than 0.074 mm are investigated in stone chippings concrete. The results show that the stone powder can participate in hydration reaction and acts as crystal nucleus in hydration process, namely, it has hydration activity to an extent. The strength of stone chippings concrete is enhanced and the easy-mixing capacity of the concrete mortar is modified when stone chippings contain a proper amount of stone powder. The stone powder has little effect on the wearability of the concrete.
基金supported by the National Key R&D Program of China(No.2017YFE0117300)the Science and Technology Planning Project of Guangzhou(No.201804020065)the Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(No.311021013).
文摘The stone chip resistance performance of automotive coatings has attracted increasing attention in academic and industrial communities.Even though traditional gravelometer tests can be used to evaluate stone chip resistance of automotive coatings,such experiment-based methods suffer from poor repeatability and high cost.The main purpose of this work is to develop a CFD-DEM-wear coupling method to accurately and efficiently simulate stone chipbehaviorof automotive coatings inagravelometer test.Toachieve this end,an approach coupling an unresolved computational fluid dynamics(CFD)method and a discrete element method(DEM)are employed to account for interactions between fluids and large particles.In order to accurately describe large particles,a rigid connection particle method is proposed.In doing so,each actual non-spherical particle can be approximately described by rigidly connecting a group of non-overlapping spheres,and particle-fluid interactions are simulated based on each component sphere.An erosion wear model is used to calculate the impact damage of coatings based on particlecoating interactions.Single spherical particle tests are performed to demonstrate the feasibility of the proposed rigid connection particle method under various air pressure conditions.Then,the developed CFD-DEM-wear model is applied to reproduce the stone chip behavior of two standard tests,i.e.,DIN 55996-1 and SAE-J400-2002 tests.Numerical results are found to be in good agreement with experimental data,which demonstrates the capacity of our developed method in stone chip resistance evaluation.Finally,parametric studies are conducted to numerically investigate the influences of initial velocity and test panel orientation on impact damage of automotive coatings.
文摘In this paper, the technical research on the application of stone chips in wet-mixed shotcrete is carried out. By comparing the consistency, initial setting time, final setting time, strength, rebound rate, project cost and other indicators of wet-mixed shotcrete with natural sand and stone chips, the technical and theoretical feasibility of stone chips based wet-mixed shotcrete is determined. Through indoor raw material quality analysis, mix proportion design and verification, and project site construction effect verification, the results are good. First, the fineness modulus and gradation range of raw materials of natural sand and stone chips are basically the same, the particle shape is different, and internal friction and bonding are good. Secondly, the mix proportion, sand ratio and water-binder ratio of natural sand and stone chip-based sprayed concrete are the same, and the mixing time of stone chip-based sprayed concrete needs to be prolonged by 15S. Thirdly, according to the characteristics of stone chip-based shotcrete, such as strong cohesive force and low rebound rate, the thickness of single shotcrete can reach 100mm for the vault and 120mm for the side wall, thus improving the working efficiency.
