矿物掺合料对混凝土氯离子渗透扩散性研究

研究了不同种类、不同掺量的矿物掺合料对混凝土氯离子渗透性的影响,试验结果显示:单掺矿物掺合料(磨细粉煤灰、矿渣、硅灰)改善混凝土抗氯离子渗透能力,且改善效果硅灰最佳,磨细粉煤灰其次,矿渣最差.从机理上分析,矿物掺合料的火山灰效应改善了混凝土中水泥石与集料之间的薄弱界面,降低孔隙率,使孔细化,同时生成更多低碱度的C-S-H凝胶增加混凝土的Cl-固化能力,从而提高了混凝土抗氯离子渗透能力.     

免压蒸预应力离心桩用C80高强混凝土抗氯离子渗透性能研究

为探索蒸汽养护对采用水泥-硅灰-矿渣粉复合胶凝材料的C80高强混凝土渗透性的影响规律,研究了不同养护条件下(蒸汽养护和标准养护)C80高强混凝土抗氯离子渗透性能(6h电通量和氯离子迁移系数),并分析了不同蒸汽养护恒温静停时间对复合胶凝材料水化程度的影响。结果表明,蒸汽养护能有效提高预应力离心桩用C80高强混凝土早期强度;标准养护下的预应力离心桩用C80高强混凝土抗氯离子渗透性能要优于蒸汽养护,且矿物掺合料的合理复掺可明显改善其氯离子抗渗透性能;电通量和扩散系数之间均存在一定的线性相关性,标养和80℃蒸养4h的要优于80℃蒸养3h和5h,80℃蒸养5h的最差。     

纤维碱矿渣混凝土抗氯离子渗透性能研究

制备碱矿渣和普通硅酸盐水泥两种系列的混凝土,对比分析聚丙烯纤维及粉煤灰对这两种体系混凝土渗透性能的影响规律,结果表明:随着龄期的延长,氯离子渗透系数均呈降低的趋势,单掺纤维或粉煤灰并不能提高碱矿渣混凝土的抗氯离子渗透能力;粉煤灰与纤维复掺后,碱矿渣混凝土的抗氯离子渗透能力仍低于纯碱矿渣混凝土,即二者复掺亦不能提高碱矿渣混凝土的抗氯离子渗透能力。     

粉煤灰掺量对混凝土抗氯离子渗透性能的影响

研究分析了粉煤灰掺量对混凝土抗氯离子渗透性的影响,并进行了电镜、X衍射和压汞测孔微观分析.结果表明:粉煤灰掺量对混凝土抗氯离子渗透性的影响随龄期不同而不同:7 d龄期时,随着粉煤灰掺量逐渐增加,混凝土的抗氯离子渗透性能逐渐降低;28 d、56 d龄期时,粉煤灰掺量小于40%时,随着粉煤灰掺量的增加混凝土的抗氯离子渗透性能逐渐增强,掺量超过40%后,电通量值有所增大.因此.40%的粉煤灰掺量是混凝土抗氯离子渗透的极限点.     

利用钢渣作掺合料及骨料的高强混凝土试验

为提高钢渣的利用率,利用钢渣与矿渣作掺合料、钢渣作骨料制备成钢渣砂替代碎石,制备钢渣高强混凝土。通过正交试验研究了水灰比、砂率、钢渣砂掺量、掺合料掺量 ４种因素对钢渣混凝土工作性能、强度的影响,得出了钢渣混凝土最适宜配合比。采用电通量法研究了最适宜配比钢渣混凝土的氯离子渗透性,其较基准混凝土要好。通过 ＳＥＭ照片对最适宜配合比钢渣混凝土 ３、２８ｄ的微观结构进行了分析,水化产物较基准混凝土密实。钢渣、矿渣等应用到混凝土中不仅具有环保节能的效果,还能改善混凝土的性能,具有良好的经济和社会效益。     

中低强度火山灰混凝土抗氯离子渗透性能试验研究

通过混凝土56天电通量试验,探讨多种因素对中低强度火山灰混凝土抗氯离子渗透性能的影响。研究表明：中低强度火山灰混凝土电通量与火山灰掺量相关性不明显,与混凝土强度亦无必然联系;一定单方胶凝材料总量下,火山灰混凝土电通量随水胶比的增大而增大。减小电通量的关键是控制水胶比,减小单方胶凝材料总量,也能使电通量降低;引气剂对中低强度混凝土抗氯离子渗透性能有较大的负面影响,引气量越高,抗氯离子渗透性能越差。     

矿物功能材料对混凝土氯离子渗透性的影响

在单因素影响方案的基础上 ,研究了多种磨细工业废渣及天然矿物材料的不同组合与叠加对混凝土氯离子渗透性的影响。通过试验研究和理论分析证实了硅灰与偏高岭土、粉煤灰、矿渣之间存在着“超复合叠加效应”,为合理选择矿物功能材料的种类及掺配方式 ,特别是偏高岭土的合理应用提供了技术思路 ,实现了矿物功能材料在提高混凝土抗氯离子渗透性方面的性能优化与降低成本的双重效用     

矿物掺合料对自密实混凝土基本性能的影响

为探讨粉煤灰、硅灰掺量对自密实混凝土工作性能和力学性能的影响, 对单掺粉煤灰自密实混凝土和复掺粉煤灰硅灰自密实混凝土进行了工作性能测试、抗压强度和抗折强度试验。结果表明: 粉煤灰和硅灰的掺入可以提高水泥浆体的流动性, 改善自密实混凝土的填充性、间隙通过能力和抗离析性能;3d龄期时,自密实混凝土的抗压强度和抗折强度随粉煤灰掺量增大均呈逐渐下降的趋势; 28d龄期时,自密实混凝土抗压强度和抗折强度随粉煤灰掺量增大均呈先增后减的趋势; 粉煤灰掺量为30%、硅灰掺量为4%时, 复掺粉煤灰硅灰自密实混凝土工作性能达到最优, 复掺粉煤灰硅灰自密实混凝土28d 龄期抗压强度和抗折强度达到峰值55.60 和8.08 MPa, 并建立了自密实混凝土抗折强度和抗压强度之间的线性回归关系模型为fcf =8.9507+0. 3078fcu 。     

再生混凝土抗氯离子渗透性能试验研究

改变再生粗骨料掺量、粉煤灰掺量、水胶比等参数,研究不同配合比对再生混凝土抗氯离子渗透能力的影响规律。试验结果表明,降低水胶比对再生混凝土抗氯离子渗透性能有利;再生混凝土氯离子迁移系数随着再生粗骨料替代率的增大而增大,抗氯离子渗透性能下降。掺加粉煤灰可以改善再生混凝土抗氯离子渗透性能,对于早龄期再生混凝土粉煤灰掺量在10%~20%之间为宜。     

再生骨料混凝土的抗氯离子渗透性试验研究

氯离子侵蚀引起钢筋锈蚀是导致混凝土结构耐久性降低甚至结构破坏的一个主要原因，同样再生骨料混凝土的抗氧离子渗透性直接关系到结构的安全和工程应用的耐久性。鉴于此，用ASTM C1202法对掺入粉煤灰、矿渣等微细矿物掺合料和加入高效减水荆的再生骨料混凝土以及天然骨料的氯离子渗透性进行了对比试验。试验结果表明粉煤灰、矿粉等矿物掺合料可以有效地改善再生骨料混凝土的氯离子渗透性，且随着强度的提高养护龄期的增长，再生骨料混凝土的抗氯离子渗透性增强，试验结果表明虽然再生骨料混凝土的抗氯离子渗透性较天然骨料混凝土差，但仍具有很好的抗氯离子渗透性。     

INITIAL BINDING CAPACTIES OF CHLORIDE ION OF COMPONENTS IN HIGH-PERFORMANCE CONCRETE

An investigation is reported on the influence of different components of high performance concrete (HPC) on the initial binding capacities (IBC) of chloride ion. The testing results demonstrate that cement has the largest IBC, and the relative binding ratio is as high as 30% of total ion amount. Among the mineral admixtures, fly ash has the largest IBC of chloride ion. The IBC of silica fume is about 14.4% ,which is smaller than that of fly ash. The IBC of refined ground blast-furnace slag (microslag) is abnormal due to the influence of sulfate ion contained. The addition of superplasticizer and corrosion inhibitor containing calcium nitrite weakens the IBC of mixtures. The fluidity and pore-filling effect of mineral admixtures are studied with paste samples with W/C ratio of 0.3. The influence mechanism of various components in high-performance concrete in IBC is studied further through SEM and Mercury Instrusion Porosimetry tests with paste samples at the age of 3 days.     

Grey clustering theory to assess the effect of mineral admixtures on the cyclic sulfate resistance of concrete

Concrete specimens made with ordinary portland cement or ordinary portland cement incorporating fly ash with the replacement of 10% or 20%, ground blast furnace slag with the replacement of 15% or 30%, or 15% fly ash and 15% ground blast furnace slag were made and exposed to a cyclic sulfate environment. Concrete properties including relative dynamic elastic modulus, chloride ion diffusion coefficient, compressive strength and flexural strength were measured. Effect of mineral admixtures on the cyclic sulfate resistance of concrete was assessed based on the grey clustering theory. The experimental results indicate that the cyclic sulfate resistance of concrete incorporating ground blast furnace slag belongs to the higher grey grade, which exhibits that it possesses excellent cyclic sulfate resistance. With increasing addition of fly ash, the cyclic sulfate resistance of concrete changes from the medium grey grade to the lower grey grade, which shows that incorporation of fly ash is disadvantageous for the cyclic sulfate resistance of concrete.     

掺合料、早强剂对冻融混凝土Cl^-扩散系数的影响

目的研究粉煤灰、矿粉、掺硫酸钠粉煤灰、掺硫酸钠矿粉混凝土冻融循环后Cl^-扩散系数,解决混凝土冻融循环后的内部结构损伤问题．方法采用慢冻法冻融、NEL法测试冻融循环后混凝土Cl^-扩散系数．结果掺入粉煤灰的质量分数低于30％时,掺入矿粉的质量分数低于40％时,经100次冻融循环后混凝土Cl^-扩散系数均低于基准混凝土．经冻融循环后,掺硫酸钠矿物掺合料的混凝土在一定的矿物掺合料掺量范围内,混凝土Cl^-扩散系数低于基准混凝土．经冻融循环后,掺硫酸钠矿物掺合料的混凝土Cl^-扩散系数高于未掺硫酸钠的矿物掺合料混凝土．结论掺粉煤灰混凝土、掺矿粉混凝土的抗冻性好坏取决于矿物掺合料掺量范围．掺硫酸钠粉煤灰混凝土、掺硫酸钠矿粉混凝土,在一定矿物掺合料的掺量范围内,混凝土抗冻性好于基准混凝土．但是硫酸钠的加入使得混凝土抗冻性比未掺硫酸钠混凝土抗冻性差．     

Influence of Mineral Admixtures on the Permeability of Lightweight Aggregate Concrete

The permeability of lightweight aggregate concrete was studied. Some efforts were taken to increase the resistarwe of lightweight aggregate concrete (LC) to water penetration by using the mineral admixtures of fiy ash, granulated blast furmwe slag or silica fume. Accelerated chloride penetrability test and liquid atmosphere press method were used to study the anti-permeability, of lightweight aggregate concrete. The experimental results show that fly ash, granulated blast furnace slag and silica fume can decrease the permeability of lightweight aggregate concrete, but the effect of granulated blast furnace slag is poor. According to the SEM and pore structure analyzing results, an interface self- reinforcing effect model was presented and the reinforced mechanism of mineral mixture on LC was discussed according to the model described by authors.     

地下水强酸盐复合腐蚀环境下不同矿物掺合料对水泥砂浆耐腐蚀性能的影响

模拟了贵州地区地下水强酸盐复合腐蚀环境,系统研究了粉煤灰、矿渣粉和硅灰3种矿物掺合料单掺与复掺对水泥砂浆耐腐蚀性能,如耐蚀系数、质量变化率、氯离子相对扩散系数的影响规律,并探讨了地下水强酸盐复合腐蚀环境下水泥砂浆的腐蚀机理。结果表明,与基准砂浆相比,单掺与复掺矿物掺合料均提高了砂浆的耐蚀系数,降低了砂浆后期氯离子相对扩散系数,但增大了砂浆质量损失率。这3项指标从不同角度反映了地下水复合腐蚀环境下水泥砂浆的耐腐蚀性能。     

二次高温养护对高强混凝土抗Cl^-渗透性的影响

利用氯离子快速渗透法（RCM）研究了普通蒸汽养护后（80℃,0.1 MPa）再进行压蒸（180℃,1 MPa）养护,即二次高温养护,对不同胶凝材料体系的高强混凝土抗Cl-渗透性的影响。结果表明：对于纯水泥混凝土,与标养相比,＂蒸养-压蒸＂养护使混凝土抗Cl-渗透性能劣化。掺入粉煤灰、矿粉以及硅灰以等比例取代水泥时,＂蒸养-压蒸＂都较为充分地激发了上述混合材的火山灰活性,但不同掺合料对＂蒸养-压蒸＂后高强混凝土抗Cl-渗透性能影响差别较大。XRD和SEM研究表明上述结果的产生与高温下水化产物的种类和分布有关。     

Grey Clustering Theory to Assess the Effect of Mineral Admixtures on the Cyclic Sulfate Resistance of Concrete

Concrete specimens made with ordinary portland cement or ordinary portland cement incorporating fly ash with the replacement of 10% or 20%, ground blast furnace slag with the replacement of 15% or 30%, or 15% fly ash and 15% ground blast furnace slag were made and exposed to a cyclic sulfate environment. Concrete properties including relative dynamic elastic modulus, chloride ion diffusion coefficient, compressive strength and flexural strength were measured. Effect of mineral admixtures on the cyclic sulfa...     

Effect of glass powder on chloride ion transport and alkali-aggregate reaction expansion of lightweight aggregate concrete

The effects of glass powder on the strength development, chloride permeability and potential alkali-aggregate reaction expansion of lightweight aggregate concrete were investigated. Ground blast furnace slag, coal fly ash and silica fume were used as reference materials. The replacement of cement with 25% glass powder slightly decreases the strengthes at 7 and 28 d, but shows no effect on 90 d’s. Silica fume is very effective in improving both the strength and chloride penetration resistance, while ground glass powder is much more effective than blast furnace slag and fly ash in improving chloride penetration resistance of the concrete. When expanded shale or clay is used as coarse aggregate, the concrete containing glass powder does not exhibit deleterious expansion even if alkali-reactive sand is used as fine aggregate of the concrete.