摘 要

钢管混凝土是一种在钢管内灌入混凝土而形成的组合材料。随着钢管中核心混凝土强度的提高，组合材料的整体刚度和承载能力增强，可增大桥梁的跨度。随着国家“十三五规划”对西部基础交通建设的大力扶持，需采用机制砂制备超高强钢管混凝土，以满足自然资源匮乏西部山区建设一批跨径更大的钢管混凝土拱桥的迫切需要。

现有钢管混凝土研究强度等级普遍在C80以下，采用机制砂制备C120自密实补偿收缩超高强钢管混凝土，因其胶材用量高、水胶比低，机制砂粒型不良，石粉含量高，存在工作性能不良，难以满足钢管混凝土泵送顶升施工；高胶凝材料用量与低水胶比的特点使得普通膨胀剂难以实现钢管混凝土膨胀性能与强度发展匹配，难以形成紧密套箍。针对以上问题，本研究依托四川省交通厅科技计划项目“超高强自密实微膨胀钢管混凝土研究与应用”和川藏高速公路工程，开展了利用机制砂制备超高强钢管混凝土的设计与性能研究，取得的主要成果如下：

1、基于混凝土密实骨料堆积原理和富余浆体理论，对超高强钢管混凝土的配合比进行理论设计，系统研究了混凝土配合比参数（胶凝材料用量、水胶比、砂率、矿物掺和料、膨胀剂、纤维等）对钢管混凝土工作性能、力学性能及体积稳定性能的影响规律：确定C120超高强混凝土的配合比为胶凝材料750kg/m³，粉煤灰微珠170kg/m³，硅灰75kg/m³，膨胀剂25kg/m³，钢纤维25kg/m³，机制砂737kg/m³，石子1060kg/m³。

2、采用人工砂制备超高强混凝土，国家标准《公路桥涵施工技术规范》JTG TF50-2011对混凝土用机制砂制备C60以上强度等级混凝土中的石粉含量要求控制在5%。本项目在配合比优化的基础上：提出外加剂应选用低含气量、超分散降粘、高保塑型外加剂；矿物掺和料选用粉煤灰微珠和硅灰复合的高活性粘度调整材料；并掺入一定的短细镀铜钢纤维，改善超高强钢管混凝土的脆性和韧性。三种技术措施协同提升混凝土性能，制备出了高石粉含量（＞7%）机制砂超高强钢管混凝土。配制的C120超高强钢管混凝土性能达到初始坍落/扩展度：260/680mm，2h坍落度损失＜10mm，含气量2.0% ，28d抗压强度达到135.5Mpa 。

1. 研究了减水剂、硅灰、石粉、膨胀剂掺量和水胶比对超高强钢管混凝土水化放热的影响：聚羧酸减水剂对胶凝浆体水化诱导期具有延长效果；低水胶比下，随着水胶比的增大，水化放热峰值略微延后；随着硅灰掺量的增加，浆体水化加速期的起始时间和放热峰出现的时间提前，3d水化放热量明显上升，表明硅灰在早期促进了胶凝材料的水化；随着HCSA型膨胀剂掺量的提高，浆体3d水化放热量上升。

关键词：高强度，自密实，机制砂，钢管混凝土

Abstract

Concrete is a kind of steel pipe filled with concrete and the formation of composite materials. With the increase of the strength of the core concrete in the steel pipe, the overall stiffness and load carrying capacity of the composite material can increase the span of the bridge. With the national "13th Five-Year Plan" on the western infrastructure construction of the strong support, the need to use the system of sand preparation of ultra-high strength concrete-filled steel pipe to meet the lack of natural resources in the western mountains to build a number of larger concrete-filled steel pipe arch bridge urgent needs.The existing strength of concrete-filled steel tube is generally below C80, and the ultra-high strength steel tube concrete (C100 ~ C120) is prepared by mechanism sand. Because of its high amount of gluing, low water-cement ratio, uneven sand granularity, high content of stone powder The performance of the high concrete material and the low water-cement ratio make it difficult for the ordinary expansion agent to realize the expansion performance of the concrete-filled steel tube and the strength development match. It is difficult to form a tight hoop. In view of the above problems, this research has carried on the research and the research on the preparation of super high strength steel tube concrete by using the mechanism sand by relying on the research and application of the "ultra high strength self-compacting micro-expanded concrete-filled steel tube" project and the Sichuan-Tibet expressway project of the Sichuan Provincial Department of Communications Science and Technology Program, The main results achieved are as follows:

1、Based on the principle of concrete aggregate accumulation and the theory of excess slurry, the mixing ratio of ultra-high strength concrete-filled steel tube is designed, and the concrete mix ratio (amount of cementitious material, water-cement ratio, sand rate, mineral blending The mechanical properties and the volume stability of the concrete-filled steel tube were determined. The ratio of C120 ultra-high-strength concrete was 750kg/m³, 170kg /m³of fly ash, 75kg /m³of silica fume and 75kg/m³ of foam, Agent 25kg/m³, steel fiber 25kg/m³, machine sand 737kg/m³, stone 1060kg/m³.

     2、 the use of artificial sand preparation of ultra-high strength concrete, the national standard "highway bridge and culvert construction technical specifications" JTG TF50-2011 on the use of concrete sand preparation C60 above the strength level of concrete powder content requirements in control of 5%. The project is based on the optimization of the mix: the admixture should be selected with low gas content, super-dispersed viscosity, high-plastic-type admixture; mineral admixture selection of fly ash beads and silica fume composite high activity viscosity adjustment material And the incorporation of certain short and thin copper-plated steel fiber to improve the brittleness and toughness of ultra-high strength concrete filled steel tube. Three kinds of technical measures to enhance the performance of concrete, prepared a high stone content (gt; 7%) mechanism of ultra-high strength steel tube concrete. The performance of C120 ultra-high strength concrete-filled steel tube reached 260.68mm, 2h slump loss lt;10mm, gas content 2.0%, 28d compressive strength reached 135.5Mpa.

3、The effects of superplasticizer, silica fume, stone powder, swelling agent and water-cement ratio on the hydration and exotherm of ultra-high strength concrete-filled steel tube are studied. The polycarboxylate superplasticizer has the effect of prolonging the hydration induction period of cement paste With the increase of the amount of silica fume, the onset time and exothermic peak of the hydration acceleration period of the slurry increased with the increase of the hydration ratio. The hydrothermal exotherm of 3d increased obviously, indicating that silica fume promoted the hydration of cementitious material in the early stage. With the increase of HCSA type expansion agent, the heat release of slurry 3d was increased.

.Key Words:High strength, self-compacting, machine sand,Concrete - filled steel tube

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