【作者】 朱晶；

【导师】 郑文忠；

【作者基本信息】 哈尔滨工业大学 ， 结构工程， 2014， 博士

【摘要】 目前，粘贴碳纤维布加固技术，已被纳入国家标准《混凝土结构加固设计规范》（GB50367-2006）和行业标准《碳纤维片材加固混凝土结构技术规程》（CECS146：2003）。碳纤维丝在绝氧条件下具有良好的耐高温性能，其强度在1000℃以内不随温度升高而降低。加固所用的常规环氧树脂胶的玻璃态转化温度Tg仅为60℃~82℃，其燃点为600℃。由于火灾是一种高频灾种，火灾发生时环境温度高达数百度至上千度，这严重制约了粘贴碳纤维布加固技术的发展。鉴于耐高温环氧树脂胶价格昂贵，且在粘贴碳纤维布过程中需在高温环境中进行，难以大规模推广应用，研发耐高温的无机胶凝材料成为行业的一种迫切需求。同时也可考虑耐高温无机胶凝材料替代混凝土，用于高温环境的工程建设。从相关文献了解到地聚物具有良好的耐高温性能，定性判断碱矿渣胶凝材料（AASCM）应具有与地聚物类似的性能。因此，我们以AASCM作为一个着力点，开展研究工作。（1）尝试进行了粒化高炉矿渣与钾水玻璃，粒化高炉矿渣与氢氧化钠，粒化高炉矿渣与水泥和少量碳酸钠，粒化高炉矿渣和粉煤灰分别与钾水玻璃、氢氧化钠、水泥和少量碳酸钠等六种方案试配，获得了AASCM两种较优配比，即以矿渣为原料，模数Ms=1.0的钾水玻璃为碱性激发剂，水玻璃用量占矿渣质量的12%，用水量分别占矿渣质量的35%和42%的两种配比。按优选配比配制的AASCM养护龄期为28d时，当用水量占矿渣质量35%时40mm×40mm×160mm胶砂件抗压强度为90.16MPa，边长70.7mm的立方体试件抗压强度为71.75MPa，70.7mm×70.7mm×228mm棱柱体试件轴心抗压强度为48.44MPa，哑铃型试件抗拉强度为3.47MPa。当用水量占矿渣质量42%时40mm×40mm×160mm胶砂件抗压强度为80.88MPa，边长70.7mm的立方体试件抗压强度为64.53MPa，70.7mm×70.7mm×228mm棱柱体试件轴心抗压强度为44.90MPa，哑铃型试件抗拉强度为3.24MPa。AASCM强度相对较高，单方造价约合330元，价格相对较低。两种较优配比中用水量占矿渣质量42%时AASCM工作性能较好。因此，选择用水量占矿渣质量42%配比的AASCM为后续研究对象。（2）为考察AASCM的常温下力学性能，完成了60个40mm×40mm×160mm胶砂件、60个边长为70.7mm的立方体、60个70.7mm×70.7mm×228mm棱柱体的抗压试验，完成了60个40mm×40mm×160mm试件的抗折试验，完成了60个哑铃型试件的抗拉试验，完成了60个边长为70.7mm立方体试件的劈拉试验。AASCM胶砂件抗压强度最高可达121.18MPa，边长为70.7mm立方体抗压强度最高可达96.43MPa，轴心抗压强度最高可达59.86MPa，抗折强度最高可达16.56MPa，抗拉强度最高可达4.45MPa，劈拉强度最高可达4.15MPa。通过对36个70.7mm×70.7mm×228mm的棱柱体试件进行单轴抗压试验，得到了AASCM受压应力-应变全曲线方程。对比分析可知，AASCM受压应力-应变曲线方程上升段与普通混凝土相似，均为二次抛物线形式，AASCM考虑应变梯度影响的下降段呈斜直线形式。通过采用SEM扫描电镜和XRD衍射分析技术，确定了AASCM的水化产物为水化硅酸钙凝胶、水滑石和水化铝酸四钙等非晶质物相。（3）为对比粘贴效果，采用双剪试验方法对90个用AASCM在混凝土表面粘贴纤维布试件（边长为100mm的混凝土立方体试块，两对面粘贴宽度为70mm，长为100mm的纤维布条带），进行常温双剪试验，获得了与胶层毗邻混凝土撕裂剥离的破坏形式，双剪试件的面内剪切强度在1.09~1.61MPa之间，与常规环氧树脂胶基本持平。通过在160mm×160mm×1000mm混凝土棱柱体两对面粘贴宽70mm，长120mm至300mm，相邻试件粘贴长度相差20mm碳纤维布条带的20个试件粘结锚固性能试验，量测了在各级荷载下碳纤维布与混凝土间剪应力的分布及有效粘结长度，获得了碳纤维布被拉断的同时混凝土被撕裂剥离时的碳纤维布的粘贴长度（即锚固长度），拟合得到了常温下碳纤维布有效粘结长度和锚固长度的计算公式。有效粘结长度计算公式考虑了破坏荷载，碳纤维布轴向刚度bfEftf和碳纤维布加载端滑移量的影响；锚固长度计算公式考虑了碳纤维布抗拉强度，计算厚度以及碳纤维布与混凝土间粘结应力的影响。（4）为考察AASCM高温下和高温后力学性能，完成了96个40mm×40mm×160mm胶砂件和96个边长为70.7mm立方体在100℃~800℃高温下和高温后抗压试验，完成了96个40mm×40mm×160mm试件在100℃~800℃高温下和高温后的抗折试验，完成了96个哑铃型试件在100℃~800℃高温下和高温后的抗拉试验。试验结果表明，在600℃高温下和600℃高温后，AASCM胶砂件抗压强度分别为常温时的81.5%和103.5%，AASCM边长70.7mm立方体抗压强度分别为常温时的85.2%和105.5%，AASCM试件抗折强度分别为常温时的44.6%和52.5%，AASCM哑铃型试件抗拉强度分别为常温时的40.1%和48.3%。在800℃高温下和800℃高温后，AASCM立方体抗压强度分别为常温时的61.3%和66.7%。相同尺寸和养护条件下的水泥石立方体抗压强度分别为常温时抗压强度的33%和42%，证明AASCM的耐高温性能明显优于水泥石。通过回归分析，拟合得到AASCM的抗压强度、抗折强度和抗拉强度等各项力学指标随温度变化的计算公式。可知在20℃~200℃高温下，胶砂件和立方体抗压强度随温度升高而降低；200℃~500℃时，抗压强度有所回升，500℃~800℃时，抗压强度随温度升高再次降低。在20℃~400℃高温后，胶砂件和立方体抗压强度随温度升高而增大；400℃~800℃高温后，抗压强度随温度升高而降低。在100℃~800℃高温下和100℃~800℃高温后，40mm×40mm×160mm试件的抗折强度和哑铃型试件的抗拉强度均随温度升高而降低。对比分析可知，高温下AASCM各项力学指标比高温后的略低。采用SEM扫描电镜和XRD衍射分析技术，揭示了AASCM在600℃~800℃之间时，其水化产物—水化硅酸钙凝胶逐渐分解，并伴有镁黄长石生成，物相组成由非晶相转变为晶相，这是AASCM高温力学性能下降的根本原因。（5）为考察高温下和高温后用AASCM作胶粘剂和密封绝氧层时碳纤维布与混凝土间的粘结锚固性能，通过在160mm×160mm×1500mm棱柱体两对面粘贴宽70mm，长225mm至400mm，相邻试件粘贴长度相差25mm碳纤维布条带的20个试件在100℃~500℃高温下的双剪试验，呈现出粘结破坏（混凝土被撕裂剥离，或部分混凝土被撕裂剥离部分胶层滑脱）但碳纤维布未被拉断，碳纤维布被拉断但未发生粘结破坏以及碳纤维布被拉断的同时发生粘结破坏。获得了高温下试件的破坏荷载和锚固长度，拟合得到高温下碳纤维布锚固长度计算公式。可知20℃~100℃高温下，碳纤维布锚固长度随温度升高而增加；100℃~500℃时，锚固长度随温度升高而降低。为考察高温后的粘结锚固性能，通过在160mm×160mm×1500mm棱柱体两对面粘贴宽70mm，长200mm至340mm，相邻试件粘贴长度相差20mm碳纤维布条带的20个试件和长350mm至500mm，相邻试件粘贴长度相差25mm碳纤维布条带的20个试件在100℃~500℃高温后的双剪试验，呈现出粘结破坏但碳纤维布未被拉断，碳纤维布被拉断但未发生粘结破坏以及碳纤维布被拉断的同时发生粘结破坏等破坏形式。在前20个试件中量测了在各级荷载下碳纤维布与混凝土间剪应力的分布和有效粘结长度，获得了高温后相关试件的破坏荷载、有效粘结长度和锚固长度实测值，拟合得到高温后碳纤维布有效粘结长度计算公式和锚固长度计算公式。更多还原

【Abstract】 Currently, the strengthening techniques with carbon fiber sheets have been incorporated into national standard “Design code for strengthening concrete structure”(GB50367-2006) and industry standard “Technical specification for strengthening concrete structures with carbon fiber reinforced polymer laminate”(CECS146：2003). Carbon fiber sheet has good high-temperature resistance at1000℃or less in anaerobic conditions, and its strength does not decrease with increasing temperature. But the glass transition temperature (Tg) of conventional epoxy resin adhesive used in strengthening is only60℃~82℃, and its ignition point is600℃. Because the fire is a high-frequency disaster, and the ambient temperature is up to several hundred degrees to thousands of degrees when the fire broke out, which has seriously hampered the development of the strengthening technique with carbon fiber sheets. View of the high-temperature resistance epoxy resin adhesives with expensive price and the process of pasting carbon fiber sheets required in the high temperature environment, it is difficult to large-scale promote and apply high-temperature resistance epoxy resin adhesives in the strengthening techniques with carbon fiber sheets. Designation and development the high-temperature resistance inorganic cementitious materials become an urgent need for the industry. In addition, the high-temperature resistance inorganic cementitious materials may also be considered to substitute for concrete applied to the construction of high-temperature environments. It is learned from the relevant literatures that the geopolymer has good high temperature performance, and it is qualitative judged that Alkali-Activated Slag Cementitious Material (AASCM) should have similar performance with geopolymer. Therefore, AASCM is chosen as a focal point to carry out research work.（1）Six kinds of mix schemes were attempted, such as ground granulated blast furnace slag and potassium silicate, ground granulated blast furnace slag and sodium hydroxide，ground granulated blast furnace slag and cement and a small amount of sodium carbonate，slag and fly ash and potassium silicate, slag and fly ash and sodium hydroxide, slag and fly ash and cement and a small amount of sodium carbonate. Two better mix proportions of AASCM were gotten, namely, slag is used as raw material, the potassium silicate with the modulus Ms=1.0is used as alkaline activator, the dosage of potassium silicate accounts for12%of the slag mass, the dosages of water account for35%and42%of the slag mass, respectively. When the better mix proportion with the dosage of water accounting for35%of the slag mass is cured for28d, the compressive strength of cement-mortar specimen in size of40mm×40mm×160mm is90.16MPa, and the compressive strength of cubic specimen in size of70.7mm×70.7mm×70.7mm is71.75MPa, and the compressive strength of prism specimen in size of70.7mm×70.7mm×228mm is48.44MPa, and the tensile strength of dumbbell specimen is3.47MPa. When the better mix proportion with the dosage of water accounting for42%of the slag mass is cured for28d, the compressive strength of cement-mortar specimen in size of40mm×40mm×160mm is80.88MPa, and the compressive strength of cubic specimen in size of70.7mm×70.7mm×70.7mm is64.53MPa, and the compressive strength of prism specimen in size of70.7mm×70.7mm×228mm is44.90MPa, and the tensile strength of dumbbell specimen is3.24MPa. AASCM has relatively high strength, The price of AASCM is about330yuan per cubic meter, so its price is relatively low. The better mix proportion of AASCM with the dosage of water accounting for42%of the slag mass has better working performance. Hence, the better mix proportion of AASCM with the dosage of water accounting for42%of the slag mass is chosen for subsequent applied research object.（2）In order to investigate the mechanical properties of AASCM at room temperature, the compression tests about60cement-mortar specimens in size of40mm×40mm×160mm and60cubic specimens in size of70.7mm×70.7mm×70.7mm and60prism specimens in size of70.7mm×70.7mm×228mm were completed, the flexural tests about60cement-mortar specimens in size of40mm×40mm×160mm were completed, the tensile tests about60dumbbell specimens were completed, and the splitting tensile tests about60cubic specimens in size of70.7mm×70.7mm×70.7mm were completed. The highest compressive strength of cement-mortar specimens is121.18MPa, and the highest compressive strength of cubic specimens is96.43MPa, and the highest axial compressive strength of specimens is59.86MPa, and the highest flexural strength of specimens is16.56MPa, and the highest tensile strength of dumbbell specimens is4.45MPa, and the highest splitting tensile strength of cubic specimens is4.15MPa. The uniaxial compression tests about36prism specimens in size of70.7mm×70.7mm×228mm were completed, and the compressive stress-strain curve equation of AASCM is gotten. Comparative analysis shows that, the ascending part of the compressive stress-strain curve equation of AASCM is similar to that of ordinary concrete, they are both quadratic parabola. The descending part of the compressive stress-strain curve equation of AASCM is oblique line form, which has considered strain gradient effects. By using SEM and XRD analysis technique, the amorphous phases calcium silicate hydrate gel, hydrotalcite and tetracalcium aluminate hydrate were determined as the hydration products of AASCM.（3）In order to contrast pasting effects,90concrete cubic specimens were strengthened with fiber sheets bonded with AASCM on the concrete surface (Two opposite sides of concrete cubic specimens in size of100mm×100mm×100mm were strengthened with70mm width and100mm length fiber strips), and double-shear tests of90specimens were completed by double-shear test methods at room temperature. The failure modes that the concrete adjacent adhesive layer was torn and stripped were obtained, the interfacial shear strength of double-shear specimens is1.09~1.61MPa, and the strengthening effects of AASCM are comparable to that of conventional epoxy resin adhesive.20concrete prism specimens in size of160mm×160mm×1000mm were strengthened on two opposite sides with70mm width,120mm to300mm length carbon fiber strips, and the carbon fiber strips of adjacent specimens had20mm length difference. By the bond anchorage properties tests, the distribution of shear stress between carbon fiber sheets and concrete at all levels of loading and effective bond length were measured, the bond lengths during carbon fiber sheets are pulled off at the same time when the concrete is torn and stripped were obtained (ie anchorage length), the calculated formulas of effective bond length and anchorage length were obtained by fitting. The effects of failure load, the effects of axial stiffness of carbon fiber sheets bfEftf and the effects of loaded end slip were considered in calculated formula of effective bond length. The effects of tensile strength and calculated thickness of carbon fiber sheets, and the effects of bond stress between carbon fiber sheets and concrete were considered in calculated formula of anchorage length.（4）In order to investigate the mechanical properties of AASCM at high temperature and after high temperature, the compression tests about96cement-mortar specimens in size of40mm×40mm×160mm and96cubic specimens in size of70.7mm×70.7mm×70.7mm were completed at100℃~800℃and after100℃~800℃, the flexural tests about96cement-mortar specimens in size of40mm×40mm×160mm were completed at100℃~800℃and after100℃~800℃high temperature, the tensile tests about96dumbbell specimens were completed at100℃~800℃and after100℃~800℃high temperature. Experimental results show that the compressive strengths of cement-mortar specimens at600℃and after600℃are81.5%and103.5%of compressive strength at room temperature, respectively; the compressive strengths of cubic specimens at600℃and after600℃are85.2%and105.5%of compressive strength at room temperature, respectively; the flexural strengths of specimens at600℃and after600℃are44.6%and52.5%of flexural strength at room temperature, respectively; the tensile strengths of dumbbell specimens at600℃and after600℃are40.1%and48.3%of tensile strength at room temperature, respectively; the compressive strengths of cubic specimens at800℃and after800℃are41.3%and66.7%of compressive strength at room temperature, respectively. The AASCM and Ordinary Portland Cement (OPC) were prepared in same size of70.7mm×70.7mm×70.7mm at same curing conditions, the compressive strengths of cubic specimens of OPC at800℃and after800℃are41.3%and66.7%of compressive strength of OPC at room temperature, respectively. It is proven that AASCM has superior high-temperature resistance than OPC. By regression analysis, the calculated formulas about compressive strength, flexural strength and tensile strength and other mechanical indexes variation with temperature were fit. It is seen that the compressive strengths of cement-mortar specimens and cubic specimens decrease with increasing temperature at20℃~200℃, the compressive strengths rebound at200℃~500℃, the compressive strengths decrease with increasing temperature at500℃~800℃again. The compressive strengths of cement-mortar specimens and cubic specimens increase with increasing temperature at20℃~400℃, the compressive strengths decrease with increasing temperature at400℃~800℃. The tensile strengths of dumbbell specimens and the flexural strengths of specimens in size of40mm×40mm×160mm decrease with increasing temperature at100℃~800℃and after100℃~800℃. Comparison analysis shows that the mechanical indexes of AASCM at high temperature are slightly lower than that of AASCM after high temperature. By using SEM and XRD analysis technique, it is revealed that the hydration product calcium silicate hydrate gradual decomposes and akermanite generates between600℃~800℃, and the phase composition translates from amorphous phase to crystalline phase, which is the root causes of mechanical properties of AASCM decline.（5）In order to investigate the bond-anchorage properties between carbon fiber sheets and concrete using AASCM as adhesive and anaerobic sealing layer at high temperature and after high temperature,20concrete specimens in size of160mm×160mm×1500mm were strengthened on two opposite sides with70mm width,225mm to400mm length carbon fiber strips, and the carbon fiber strips of adjacent specimens had25mm length difference. By double-shear tests at100℃~500℃, the bond failure (concrete is torn and stripped, or some concrete is torn and stripped and some adhesive layer slips) is shown but carbon fiber sheets are not pulled off, carbon fiber sheets are pulled off but bond failure is not shown, carbon fiber sheets are pulled off at the same time when the bond failure is shown and so on. The failure loads and anchorage lengths were measured, and the calculated formulas of anchorage length were obtained by fitting at high temperature. It is seen that the anchorage lengths of carbon fiber sheets increase with increasing temperature at20℃~100℃, the anchorage lengths of carbon fiber sheets decrease with increasing temperature at100℃~500℃. In order to investigate bond-anchorage properties after high temperature,20concrete prism specimens in size of160mm×160mm×1500mm were strengthened on two opposite sides with70mm width,200mm to340mm length carbon fiber strips, and the carbon fiber strips of adjacent specimens had20mm length difference; and20concrete prism specimens in size of160mm×160mm×1500mm were strengthened on two opposite sides with70mm width,350mm to500mm length carbon fiber strips, and the carbon fiber strips of adjacent specimens had25mm length difference. By double-shear tests after100℃~500℃, the bond failure is shown but carbon fiber sheets are not pulled off, carbon fiber sheets are pulled off but bond failure is not shown, carbon fiber sheets are pulled off at the same time when the bond failure is shown. The distribution of shear stress between carbon fiber sheets and concrete at all levels of loading and effective bond length were measured from first20specimens. The failure loads of related specimens, effective bond length and anchorage length measured values after high temperature were obtained. The calculated formulas of effective bond length and anchorage length were obtained by fitting after high temperature.更多还原