To study the durability of concrete in harsh environments in Northwest China,concrete was prepared with various durability-improving materials such as concrete anti-erosion inhibitor(SBT-TIA),acrylate polymer(AP),supe...To study the durability of concrete in harsh environments in Northwest China,concrete was prepared with various durability-improving materials such as concrete anti-erosion inhibitor(SBT-TIA),acrylate polymer(AP),super absorbent resin(SAP).The erosion mode and internal deterioration mechanism under salt freeze-thaw cycle and dry-wet cycle were explored.The results show that the addition of enhancing materials can effectively improve the resistance of concrete to salt freezing and sulfate erosion:the relevant indexes of concrete added with X-AP and T-AP are improved after salt freeze-thaw cycles;concrete added with SBTTIA shows optimal sulfate corrosion resistance;and concrete added with AP displays the best resistance to salt freezing.Microanalysis shows that the increase in the number of cycles decreases the generation of internal hydration products and defects in concrete mixed with enhancing materials and improves the related indexes.Based on the Wiener model analysis,the reliability of concrete with different lithologies and enhancing materials is improved,which may provide a reference for the application of manufactured sand concrete and enhancing materials in Northwest China,especially for the study of the improvement effects and mechanism of enhancing materials on the performance of concrete.展开更多
In order to optimize gob-side entry in fully-mechanized working face in moderate-thick-coal seams, we adopt a new attempt to pack roadside by pumping ordinary concrete, which is very important for the development of g...In order to optimize gob-side entry in fully-mechanized working face in moderate-thick-coal seams, we adopt a new attempt to pack roadside by pumping ordinary concrete, which is very important for the development of gob-side entry technology. The concrete has a long initial setting time and a low initial strength. So it is difficult to control the surrounding rock. In this paper, we analyze the effect of using roadside cable to reinforce supporting in gob-side entry surrounding rock controlling based on elas-tic-plastic and material mechanics knowledge. And then we propose a scheme that cable is used to reinforce roadside supporting and a single hydraulic prop is used as the temporary supporting in gob side. Using the numerical simulation software FLAC2D, we numerically simulated supporting scheme. Results of both the 2D modeling and the industrial test on No.3117 face in Jingang Mine prove that the scheme is feasible. The results show that the technology of protecting the roadway in gob-entry retained efficiently make up the deficiency of roadside packing with ordinary concrete, effectively control the roof strata and acquire a good result of retaining roadway.展开更多
采用核磁共振(Nuclear magnetic resonance,NMR)测试了玄武岩-聚丙烯混杂纤维混凝土(HBPRC)的孔隙特征,对比分析了玄武岩纤维(BF)和聚丙烯纤维(PF)及二者混杂对HBPRC的抗压强度、孔隙率、孔径分布和曲折度的影响,并基于核磁共振T2谱和...采用核磁共振(Nuclear magnetic resonance,NMR)测试了玄武岩-聚丙烯混杂纤维混凝土(HBPRC)的孔隙特征,对比分析了玄武岩纤维(BF)和聚丙烯纤维(PF)及二者混杂对HBPRC的抗压强度、孔隙率、孔径分布和曲折度的影响,并基于核磁共振T2谱和孔隙结构分形理论对4个孔径区域的孔隙结构分形维数进行了量化。结果表明:随着BF的添加,T2谱反映出适量的BF可以减小混凝土的孔隙率,而且有利于减小大孔体积占比;而随着PF含量增加,T2谱面积增加,且混凝土内部孔隙有变大的趋势。掺入BF-PF混杂纤维对混凝土的孔隙特征会产生正协同作用,当BF和PF掺量均为0.05vol%时,协同作用最佳,与普通混凝土相比,抗压强度提高了3.52%、孔隙率降低了1.47%、曲折度提高了8.20%。凝胶孔体积占比增大了8.76%,大孔体积占比降低了5.30%,孔径分布得到优化。HBPRC的孔隙结构具有明显的分形特征,孔隙结构分形维数在过渡孔、毛细孔和大孔区域依次增加,此外,分形维数越大,抗压强度越大。通过微观分析认为,纤维在混凝土基体中的粘结状态和分布是影响HBPRC孔隙分形特征的主要原因。展开更多
基金Funded by the National Natural Science Foundation of China(No.52178216)the Research on the Durability and Application of High-performance Concrete for Highway Engineering in the Cold and Arid Salt Areas of Northwest China(No.2022-24)the Construction Project of the Scientific Research Platform of Provincial Enterprises Supported by the Capital Operating Budget of Gansu Province(No.2023GZ018)。
文摘To study the durability of concrete in harsh environments in Northwest China,concrete was prepared with various durability-improving materials such as concrete anti-erosion inhibitor(SBT-TIA),acrylate polymer(AP),super absorbent resin(SAP).The erosion mode and internal deterioration mechanism under salt freeze-thaw cycle and dry-wet cycle were explored.The results show that the addition of enhancing materials can effectively improve the resistance of concrete to salt freezing and sulfate erosion:the relevant indexes of concrete added with X-AP and T-AP are improved after salt freeze-thaw cycles;concrete added with SBTTIA shows optimal sulfate corrosion resistance;and concrete added with AP displays the best resistance to salt freezing.Microanalysis shows that the increase in the number of cycles decreases the generation of internal hydration products and defects in concrete mixed with enhancing materials and improves the related indexes.Based on the Wiener model analysis,the reliability of concrete with different lithologies and enhancing materials is improved,which may provide a reference for the application of manufactured sand concrete and enhancing materials in Northwest China,especially for the study of the improvement effects and mechanism of enhancing materials on the performance of concrete.
基金support from the National Nature Science Foundation of China (No50874124)
文摘In order to optimize gob-side entry in fully-mechanized working face in moderate-thick-coal seams, we adopt a new attempt to pack roadside by pumping ordinary concrete, which is very important for the development of gob-side entry technology. The concrete has a long initial setting time and a low initial strength. So it is difficult to control the surrounding rock. In this paper, we analyze the effect of using roadside cable to reinforce supporting in gob-side entry surrounding rock controlling based on elas-tic-plastic and material mechanics knowledge. And then we propose a scheme that cable is used to reinforce roadside supporting and a single hydraulic prop is used as the temporary supporting in gob side. Using the numerical simulation software FLAC2D, we numerically simulated supporting scheme. Results of both the 2D modeling and the industrial test on No.3117 face in Jingang Mine prove that the scheme is feasible. The results show that the technology of protecting the roadway in gob-entry retained efficiently make up the deficiency of roadside packing with ordinary concrete, effectively control the roof strata and acquire a good result of retaining roadway.
文摘采用核磁共振(Nuclear magnetic resonance,NMR)测试了玄武岩-聚丙烯混杂纤维混凝土(HBPRC)的孔隙特征,对比分析了玄武岩纤维(BF)和聚丙烯纤维(PF)及二者混杂对HBPRC的抗压强度、孔隙率、孔径分布和曲折度的影响,并基于核磁共振T2谱和孔隙结构分形理论对4个孔径区域的孔隙结构分形维数进行了量化。结果表明:随着BF的添加,T2谱反映出适量的BF可以减小混凝土的孔隙率,而且有利于减小大孔体积占比;而随着PF含量增加,T2谱面积增加,且混凝土内部孔隙有变大的趋势。掺入BF-PF混杂纤维对混凝土的孔隙特征会产生正协同作用,当BF和PF掺量均为0.05vol%时,协同作用最佳,与普通混凝土相比,抗压强度提高了3.52%、孔隙率降低了1.47%、曲折度提高了8.20%。凝胶孔体积占比增大了8.76%,大孔体积占比降低了5.30%,孔径分布得到优化。HBPRC的孔隙结构具有明显的分形特征,孔隙结构分形维数在过渡孔、毛细孔和大孔区域依次增加,此外,分形维数越大,抗压强度越大。通过微观分析认为,纤维在混凝土基体中的粘结状态和分布是影响HBPRC孔隙分形特征的主要原因。
