| Coal gangue is a kind of solid waste produced in the process of coal mining.Coal gangue is prone to spontaneous-combustion by temperature accumulation,transforming to spontaneous-combustion coal gangue.The Crushed aggregate could be used in structural concrete,i.e.,spontaneous combustion coal gangue concrete(SCGAC),which can achieve positive resource utilizations from passive harmless treatments.Steel-concrete composite slabs has the advantages of convenient construction and high bearing capacity.Introducing SCGAC into steel-concrete composite slabs can reduce the self-weight of structural members and compensate the inferior mechanical properties of SCGAC.The non-uniform shrinkage and creep of steel-concrete composite slabs are obvious,while the non-uniform shrinkage and creep of steel-SCGAC composite slabs are much more obvious.However,the influence of non-uniform shrinkage of concrete is not considered in the long-term performance calculation method of current codes.In this manner,the long-term mechanical properties of SCGAC materials and the long-term properties of steel-SCGAC composite slabs were studied.The details are as follows:(1)A total of 36 SCGAC specimens in 4 groups were designed and fabricated,the effect of spontaneous combustion coal gangue aggregate substitution ration(r_c)on the concrete elastic modulus and drying shrinkage was quantified,and elastic modulus and drying shrinkage prediction model suitable for SCGAC was proposed.The research results show that compared with reference concrete,the elastic modulus of SCGAC with r_c of 100%was reduced by 31.1%and drying shrinkage was increased by 92.0%,the elastic modulus prediction model of SCGAC based on the BNC model can reasonably predict the elastic modulus of concrete,with the average ratio between the prediction elastic modulus and the test results of 0.936,determination coefficient R~2 of 0.837.The drying shrinkage prediction model of SCGAC based on the two components composite material theory can better predict the drying shrinkage of concrete,and the error between the prediction results and the test results was within 10%.(2)A uniaxial stress-strain relationship model was proposed using the existing experimental data of SCGAC,and further introduced to the ABAQUS software to analyze the flexural performance of the steel-SCGAC composite slabs under the ultimate limit state.The results show that the spontaneous combustion coal gangue aggregate substitution ratio had limited effects on the flexural moment of the composite slabs,but had a significant effect on the flexural stiffness.Based on the results of parametric analysis,it is found that the"Code for Design of Concrete Structures"was suitable for the prediction of flexural stiffness of reinforced truss-SCGAC composite slabs,while ACI 318 and AS 3600 specifications was suitable for the prediction of flexural stiffness of profiled steel decks-SCGAC composite slabs.(3)A total of 20 groups of SCGAC shrinkage specimens were designed and fabricated,and the effects of parameters including SCGA replacement ratio,humidity boundary condition,and specimen thickness were investigated experimentally.The non-uniform shrinkage model of SCGAC under different humidity boundary conditions was proposed.Refined finite element model for long-term performance of steel-SCGAC composite slabs was established to quantify the effects of SCGA replacement ratio on long-term performance,and based on the parametric results,the long-term deflection calculation method for steel-SCGAC composite slabs was proposed.The results show that the SCGA replacement ratio had a significant effect on the long-term deflection of the composite slabs,and the long-term deflection of the composite slabs with SCGA replacement ratio of 100%was increased by62.6%～79.8%compared with the reference specimens.The average ratio of the long-term deflection calculation results of the modified steel-SCGAC composite slabs to the finite element results was 1.026,and the determination coefficient R~2 was 0.925. |
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