高体积率钢纤维自密实混凝土静态断裂性能研究
发布时间：2018-07-20 21:32
【摘要】：自密实混凝土中可以通过掺入钢纤维来改善其强度和韧性。以往研究都主要集中为普通钢纤维增强自密实混凝土,所选用的钢纤维主要集中在长度为15~35mm,长细比为40~65且体积掺量通常不超过1.5%。尽管普通钢纤维对自密实混凝土的强度和韧性均有一定程度的提高,但提高幅度有限,完全可以通过调整配合比配制出同等强度等级的普通自密实混凝土。此外,当纤维体积掺量超过1.5%后,纤维分散性变差,混合料搅拌难度大易出现结团、流动性降低难以达到自密实,材料基本性能持续提高难以实现。论文以断裂力学阻裂增强机理为基础,以满足自密实混凝土工作性为前提,提出一种刚性纤维改性水泥基复合材料的研究方法,实现传统钢纤维自密实混凝土难以实现的钢纤维高掺量,得到一种具有高强度和高韧性特性的高掺量微细平直型钢纤维自密实混凝土(SFRSCC),并针对高强特性可能导致的缺陷敏感性开展断裂性能试验,即高强材料存在初裂纹的条件下,其高强优势会不会导致其缺陷敏感性也倍增。论文在大量的工作性和基本力学性能试验的基础上,通过三点弯曲缺口小梁试验研究了其静态断裂性能。具体展开了以下工作:①基于断裂力学原理设计的SFRSCC混合料工作性能良好,当钢纤维体积掺量达到6%时,微细平直型钢纤维自密实混凝土混合料的塌落扩展度SP达到了600mm以上,钢纤维乱向均匀分布于混合料中,无明显骨料堆积现象。抗离析性能极好,筛余率为1.3%。对于3×40mm的钢筋间隙,当体积掺量为0~3.0%时,通过性良好H2/H1能达到90%以上,当体积掺量为4.5%~6.0%时会出现轻微堵塞现象。②与C40、C50基准自密实混凝土相比,基本力学性能指标随着纤维体积掺量的增加而提高,当纤维体积掺量达到6%,C40组(A组)SFRSCC立方体抗压强度提高111.4%,抗折强度提高214.2%,劈拉强度提高133.2%,压缩弹性模量提高13.1%,弯拉弹性模量提高9.3%,初裂强度提高217.1%,等效弯曲强度提高1083.3%,弯曲韧性比提高300%;C50组(B组)SFRSCC立方体抗压强度提高73.0%,抗折强度提高143.2%,劈拉强度提高173.6%,压缩弹性模量提高16.5%,弯拉弹性模量提高9.8%,初裂强度提高125.0%,等效弯曲强度提高了1080.3%,弯曲韧性比提高264.7%。③三点弯曲缺口小梁断裂性能测试表明,预裂相同情况下,与C40、C50的素基准自密实混凝土相比,C40组(A组)SFRSCC有效裂缝高度平均提高51.8%,断裂韧度平均提高193.7%,起裂韧度平均提高139.6%,失稳韧度平均提高195.7%,加载点最大位移平均提高1002.4%,断裂能增益比平均为23.0。C50组(B组)SFRSCC有效裂缝高度平均提高102.6%,断裂韧度平均提高236.5%,起裂韧度平均提高98.1%,失稳韧度平均提高285.6%。加载点最大位移平均提高1071.1%。断裂能增益比平均为23.27。当纤维层≥60mm,随着纤维层厚度的提高,有效裂纹长度增长缓慢,趋于稳定,达到1/3梁截面高度(包括预裂缝长度),断裂韧度值也趋于稳定。SFRSCC试件的P-CMOD曲线和荷载-位移曲线呈现明显的塑性特征,素自密实混凝土达到峰值荷载后曲线迅速下降,失去承载能力。SFRSCC不仅具有非线性弹性阶段,在达到峰值荷载后具有较长的塑性阶段,曲线缓慢下降,裂缝稳定扩展时间长,裂纹尖端张开位移提高明显,具有高强韧特性。④运用ANSYS有限元分析软件得出的断裂韧度值与试验研究得出的断裂韧度值随着纤维层厚度增大而变化的规律一致,验证缺口小梁的断裂韧度的准确性。综上所述,与普通自密实混凝土相比,试验研究配制出的高体积率钢纤维自密实混凝土工作性能及力学性能良好,具有广阔的应用前景。
[Abstract]:The strength and toughness of self compacting concrete can be improved by adding steel fiber. The previous study was mainly concentrated on steel fiber reinforced self compacting concrete. The steel fiber selected mainly concentrated in the length of 15~35mm, the length and slenderness ratio of 40~65 and the volume content usually not more than 1.5%., although the strength of the self compacting concrete was stronger than that of the ordinary steel fiber. The degree and toughness are improved to a certain extent, but the increase in the range is limited, and the ordinary self compacting concrete with the same strength grade can be prepared by adjusting the mix ratio. In addition, when the volume of the fiber is more than 1.5%, the dispersion of the fiber becomes worse and the mixing is difficult to be mixed, and the flow property is difficult to achieve self compacting, and the material is difficult to achieve self compacting. It is difficult to realize the continuous improvement of basic performance. Based on the strengthening mechanism of fracture mechanics, this paper puts forward a research method of rigid fiber modified cement based composite on the premise of satisfying the working property of self compacting concrete, and realizes the high admixture of steel fiber which is difficult to be realized by the traditional steel fiber self compacting concrete, and obtains a high strength. The high admixture of high admixture and high tenacity steel fiber self compacting concrete (SFRSCC), and to carry out the fracture performance test for the defect sensitivity of high strength properties, that is, under the condition of the initial crack in the high strength material, its high strength will not cause the defect sensitivity to be doubled. On the basis of the performance test, the static fracture performance of the three point bending notch trabecula was studied. The following work was carried out: (1) the working performance of the SFRSCC mixture based on the principle of fracture mechanics was good. When the volume of steel fiber volume reached 6%, the collapse expansion of the self compacting concrete mixture was S P reaches more than 600mm, and the steel fiber is uniformly distributed in the mixture without obvious aggregate accumulation. The anti segregation performance is excellent, the sieve residual rate is 1.3%. for 3 x 40mm steel bar gap, when the volume content is 0~3.0%, the good H2/H1 can reach more than 90%. When the volume content is 4.5%~6.0%, there will be a slight clogging phenomenon. (2) and C40, C50 Compared with the base self compacting concrete, the basic mechanical performance index increases with the increase of the volume of fiber volume. When the volume of fiber volume reaches 6%, the compressive strength of SFRSCC cube in group C40 (A group) is increased by 111.4%, the flexural strength is raised by 214.2%, the splitting tensile strength is increased by 133.2%, the elastic modulus of compression is increased by 13.1%, the flexural modulus is increased by 9.3%, and the initial crack strength is strong. The equivalent bending strength is raised by 217.1%, the equivalent bending strength is increased by 1083.3%, the flexural toughness is 300%, the compressive strength of the SFRSCC cube in group C50 (B group) is increased by 73%, the flexural strength is raised by 143.2%, the splitting tensile strength is increased by 173.6%, the compression modulus is raised by 16.5%, the flexural modulus is raised by 9.8%, the initial crack strength is increased by 125%, the equivalent bending strength is increased 1080.3%, the bending strength is 1080.3%, bending. The fracture performance test of the flexural toughness ratio (264.7%.) three point bending notched trabecula shows that the effective crack height of C40 group (A group) is increased by 51.8%, the fracture toughness increases by 193.7%, the crack toughness increases by 139.6% and the instability toughness increases 195.7%, and the instability toughness increases by 195.7%. The point maximum displacement is increased by 1002.4%, the fracture energy gain is higher than the average 23.0.C50 group (B group), the effective crack height of SFRSCC is increased by 102.6%, the fracture toughness increases by 236.5%, the crack toughness increases by 98.1%, the instability toughness increases averaging the maximum displacement of the 285.6%. loading point and the 1071.1%. fracture energy gain ratio is 23.27. as the average fiber. As the layer is more than 60mm, with the increase of the thickness of the fiber layer, the effective crack length increases slowly and tends to stable, reaching the height of the 1/3 beam section (including the length of the pre crack). The fracture toughness values also tend to be stable in the P-CMOD curve and load displacement curve of the.SFRSCC specimen, and the curve of the self compacting concrete is rapidly under the peak load. .SFRSCC not only has nonlinear elastic phase, but also has a long plastic stage after reaching the peak load. The curve slows down slowly, the crack growth time is long, the crack tip opening displacement increases obviously and has high toughness characteristics. (4) the fracture toughness value obtained by using the ANSYS finite element analysis software and experimental study The fracture toughness values are consistent with the increase of the thickness of the fiber layer, and the accuracy of the fracture toughness of the notched trabecula is verified. In summary, compared with the ordinary self compacting concrete, the high volume rate steel fiber self compacting concrete has a good working performance and good mechanic performance, which has a broad application prospect.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528
[Abstract]:The strength and toughness of self compacting concrete can be improved by adding steel fiber. The previous study was mainly concentrated on steel fiber reinforced self compacting concrete. The steel fiber selected mainly concentrated in the length of 15~35mm, the length and slenderness ratio of 40~65 and the volume content usually not more than 1.5%., although the strength of the self compacting concrete was stronger than that of the ordinary steel fiber. The degree and toughness are improved to a certain extent, but the increase in the range is limited, and the ordinary self compacting concrete with the same strength grade can be prepared by adjusting the mix ratio. In addition, when the volume of the fiber is more than 1.5%, the dispersion of the fiber becomes worse and the mixing is difficult to be mixed, and the flow property is difficult to achieve self compacting, and the material is difficult to achieve self compacting. It is difficult to realize the continuous improvement of basic performance. Based on the strengthening mechanism of fracture mechanics, this paper puts forward a research method of rigid fiber modified cement based composite on the premise of satisfying the working property of self compacting concrete, and realizes the high admixture of steel fiber which is difficult to be realized by the traditional steel fiber self compacting concrete, and obtains a high strength. The high admixture of high admixture and high tenacity steel fiber self compacting concrete (SFRSCC), and to carry out the fracture performance test for the defect sensitivity of high strength properties, that is, under the condition of the initial crack in the high strength material, its high strength will not cause the defect sensitivity to be doubled. On the basis of the performance test, the static fracture performance of the three point bending notch trabecula was studied. The following work was carried out: (1) the working performance of the SFRSCC mixture based on the principle of fracture mechanics was good. When the volume of steel fiber volume reached 6%, the collapse expansion of the self compacting concrete mixture was S P reaches more than 600mm, and the steel fiber is uniformly distributed in the mixture without obvious aggregate accumulation. The anti segregation performance is excellent, the sieve residual rate is 1.3%. for 3 x 40mm steel bar gap, when the volume content is 0~3.0%, the good H2/H1 can reach more than 90%. When the volume content is 4.5%~6.0%, there will be a slight clogging phenomenon. (2) and C40, C50 Compared with the base self compacting concrete, the basic mechanical performance index increases with the increase of the volume of fiber volume. When the volume of fiber volume reaches 6%, the compressive strength of SFRSCC cube in group C40 (A group) is increased by 111.4%, the flexural strength is raised by 214.2%, the splitting tensile strength is increased by 133.2%, the elastic modulus of compression is increased by 13.1%, the flexural modulus is increased by 9.3%, and the initial crack strength is strong. The equivalent bending strength is raised by 217.1%, the equivalent bending strength is increased by 1083.3%, the flexural toughness is 300%, the compressive strength of the SFRSCC cube in group C50 (B group) is increased by 73%, the flexural strength is raised by 143.2%, the splitting tensile strength is increased by 173.6%, the compression modulus is raised by 16.5%, the flexural modulus is raised by 9.8%, the initial crack strength is increased by 125%, the equivalent bending strength is increased 1080.3%, the bending strength is 1080.3%, bending. The fracture performance test of the flexural toughness ratio (264.7%.) three point bending notched trabecula shows that the effective crack height of C40 group (A group) is increased by 51.8%, the fracture toughness increases by 193.7%, the crack toughness increases by 139.6% and the instability toughness increases 195.7%, and the instability toughness increases by 195.7%. The point maximum displacement is increased by 1002.4%, the fracture energy gain is higher than the average 23.0.C50 group (B group), the effective crack height of SFRSCC is increased by 102.6%, the fracture toughness increases by 236.5%, the crack toughness increases by 98.1%, the instability toughness increases averaging the maximum displacement of the 285.6%. loading point and the 1071.1%. fracture energy gain ratio is 23.27. as the average fiber. As the layer is more than 60mm, with the increase of the thickness of the fiber layer, the effective crack length increases slowly and tends to stable, reaching the height of the 1/3 beam section (including the length of the pre crack). The fracture toughness values also tend to be stable in the P-CMOD curve and load displacement curve of the.SFRSCC specimen, and the curve of the self compacting concrete is rapidly under the peak load. .SFRSCC not only has nonlinear elastic phase, but also has a long plastic stage after reaching the peak load. The curve slows down slowly, the crack growth time is long, the crack tip opening displacement increases obviously and has high toughness characteristics. (4) the fracture toughness value obtained by using the ANSYS finite element analysis software and experimental study The fracture toughness values are consistent with the increase of the thickness of the fiber layer, and the accuracy of the fracture toughness of the notched trabecula is verified. In summary, compared with the ordinary self compacting concrete, the high volume rate steel fiber self compacting concrete has a good working performance and good mechanic performance, which has a broad application prospect.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528
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相关期刊论文 前3条
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2 陈春珍;张金喜;陈炜林;金珊珊;李建军;;自密实混凝土配合比设计方法适用性的研究[J];混凝土;2009年12期
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