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通过对比脱硝粉煤灰与普通粉煤灰应用于混凝土的工作性能、力学性能及耐久性能等的差异,探索脱硝粉煤灰在混凝土中的应用技术。研究结果表明:掺脱硝粉煤灰的混凝土拌合物性能与掺普通粉煤灰的混凝土基本相当;早期抗压强度略低于掺普通粉煤灰的混凝土,3d、7d抗压强度分别降低0%~14.6%、0%~7.7%;长期抗压强度及耐久性能略高于掺普通粉煤灰的混凝土。建议在实际工程应用中谨慎控制脱硝粉煤灰掺量。 相似文献
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《粉煤灰》2016,(4)
通过对比脱硝粉煤灰与普通粉煤灰应用于水泥、混凝土的性能差异及其与减水剂的相容性等,探索脱硝粉煤灰资源化利用于建材的应用技术。研究结果表明:萘系减水剂、聚羧酸减水剂均可用于掺脱硝粉煤灰的水泥-粉煤灰体系,且聚羧酸减水剂与该体系的相容性更好;掺脱硝粉煤灰的水泥比掺普通粉煤灰的水泥的凝结时间缩短20~25 min,3 d抗压强度下降3.2%~9.3%,3 d抗折强度下降1.5%~13.2%。掺脱硝粉煤灰的混凝土与掺普通粉煤灰的混凝土拌合物性能相近,其7 d、28 d抗压强度比掺普通粉煤灰的混凝土降低12.6%、6.1%。建议在实际工程应用中限制掺入量上限或结合现场验证试验后谨慎使用。 相似文献
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研究了掺合料复掺(矿渣∶粉煤灰=2∶1)、单掺矿渣、单掺粉煤灰对硫铝酸盐水泥基混凝土强度、抗渗性、抗冻性的影响,并与相同水灰比下掺合料复掺对普通硅酸盐水泥基混凝土对应性能的影响进行对比。结果表明:在硫铝酸盐水泥基混凝土中,掺合料的加入使混凝土的早期和后期强度都明显降低,抗渗性稍微降低,抗冻性明显降低,且掺量越高,其强度、抗渗性、抗冻性降低越明显;但复掺时的效果比单掺时的效果好,粉煤灰的效果最差;而在普通硅酸盐水泥基混凝土中,掺合料的加入使混凝土的早期强度降低,但后期强度超过空白样的强度,抗渗性、抗冻性明显提高,但是,在无掺合料时其抗渗性、抗冻性大大低于相同水灰比下硫铝酸盐水泥基混凝土的抗渗性、抗冻性。 相似文献
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通过掺加粉煤灰和偏高岭土制备高强混凝土,研究了其在400℃、600℃、800℃、1000℃高温热处理后的力学性能变化,并与相同强度等级的混凝土进行对比,分析其在高温混凝土领域的应用优势.试验结果表明:普通高强混凝土经600℃热处理后,表观裂纹已经非常明显,而掺粉煤灰和偏高岭土的高强混凝土表观破坏温度为800℃;掺粉煤灰与偏高领土高强混凝土的高温力学性能出现先增长后迅速降低的现象,抗压强度最大值达到125.2 MPa,而普通高强混凝土高温处理后力学性能不断下降;普通高强混凝土随着热处理温度升高,浆体中的水化产物硅钙石、氢氧化钙不断分解,结构劣化严重,而掺粉煤灰和偏高岭土后浆体中会形成大量的耐高温相,而此过程会改善浆体中产生的部分结构缺陷,大幅度延缓力学性能退化,在1000℃热处理后浆体向陶瓷转变;掺粉煤灰和偏高领土的高强混凝土与相同强度等级的混凝土相比,在高温领域内的有着更加明显的优势,应用前景广阔. 相似文献
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高掺量粉煤灰混凝土强度发展潜力 总被引:2,自引:0,他引:2
测定了粉煤灰火山灰的反应率;估算了粉煤灰火山灰反应所需的最小水泥用量[或Ca(OH)2量];研究了高掺量粉煤灰混凝土的长期强度增长趋势。试验结果表明:粉煤灰的火山灰反应程度极其有限,极限火山灰反应率不大于20%;高掺量粉煤灰混凝土不会存在所谓“贫钙”问题;与普通混凝土相比,高掺量粉煤灰混凝土具有更强的后期强度增长趋势。 相似文献
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A multiscale micromechanics-hydration model for the early-age elastic properties of cement-based materials 总被引:3,自引:0,他引:3
The E-modulus of early age cement-based materials, and more importantly, its evolution in time, is one of the most critical material-to-structural design parameters affecting the likelihood of early-age concrete cracking. This paper addresses the problem by means of a multistep micromechanics approach that starts at the nanolevel of the C-S-H matrix, where two types of C-S-H develop in the course of hydration. For the purpose of homogenization, the volume fractions of the different phases are required, which are determined by means of an advanced kinetics model of the four main hydration reactions of ordinary portland cement (OPC). The proposed model predicts with high accuracy the aging elasticity of cement-based materials, with a minimum intrinsic material properties (same for all cement-based materials), and 11 mix-design specific model parameters that can be easily obtained from the cement and concrete suppliers. By way of application, it is shown that the model provides a quantitative means to determine (1) the solid percolation threshold from micromechanics theory, (2) the effect of inclusions on the elastic stiffening curve, and (3) the development of the Poisson's ratio at early ages. The model also suggests the existence of a critical water-to-cement ratio below which the solid phase percolates at the onset of hydration. The development of Poisson's ratio at early ages is found to be characterized by a water-dominated material response as long as the water phase is continuous, and then by a solid-dominated material response beyond the solid percolation threshold. These model-based results are consistent with experimental values for cement paste, mortar, and concrete found in the open literature. 相似文献
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Mixture-proportioning of high-performance concrete 总被引:6,自引:0,他引:6
The paper presents a new approach to design concrete mixtures. It is based upon a set of models relating composition and engineering properties of concrete, to be implemented into software, linked with a material database. The principles underlying the various models are summarized, most of which focus on the granular structure of fresh/hardened concrete. A global approach to concrete is promoted, where performance specifications can be formulated in terms of fresh concrete (yield stress, plastic viscosity, slump and air content), hardening concrete (adiabatic temperature rise and autogenous shrinkage) and hardened concrete (compressive strength at any age, tensile strength, elastic modulus, creep and shrinkage). This approach is illustrated through the design of a special high-shrinkage high-performance concrete (HPC) for road application. To date, durability is lacking in the model and requires further research. 相似文献
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《Fuel》2006,85(12-13):1944-1949
High-volume fly ash (HVFA) concrete is an economical and durable option for structural as well as general concreting purposes, if properly controlled ashes are employed. The aim of this study was to investigate the possibility of the use of three types of Turkish fly ashes from different sources in cost effective high-volume fly ash concrete production. For this purpose HVFA concrete mixtures were prepared by substituting 40, 50, 60 and 70% of cement by fly ash. The mechanical properties and material costs of mixtures were compared with conventional concrete at the same strength grade at 28 days. It should be noted that as an additional benefit, the long-term strength development and durability advantageous of HVFA concrete is not taken into consideration in cost analysis. Results showed that for structural applications a technically suitable and cost effective HVFA concrete can only be produced by using the fly ashes within the limits of specific chemical and physical properties. It may be possible to use other fly ashes with rehabilitation and pre-process, which may reduce the economical feasibility of fly ash usage. 相似文献
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本文针对涤纶短纤维是特殊“混合物”的特点 ,结合涤纶短纤维标准样品的使用 ,讨论了不同定值方案的适用情况 ,并具体分析了由单值标准偏差计算的单值统计容许区间和由平均值计算的平均值统计容许区间的使用效果 ,结果表明 ,由标准值和单值统计容许区间的定值方式最适合于涤纶短纤维标准样品 相似文献
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通过试验研究了再生混凝土作为北方满族民居建造材料的可行性。研究重点:再生骨料的物理性质测定、再生混凝土基本力学性能试验,以及粉煤灰、聚丙烯纤维以及附加水对其力学性能的影响。通过试验得到,再生混凝土立方体抗压强度最高应力达37.1 MPa、轴心抗压强度平均应力28.4 MPa、静力受压弹性模量平均应力22 300 MPa、抗折强度平均应力3.8 MPa、劈裂抗拉强度平均应力1.68 MPa。结果表明:在再生混凝土中加入粉煤灰和聚丙烯纤维都对立方体抗压强度有所提高,但附加水的加入对立方体抗压强度产生了降低作用。整体来说,再生混凝土各方面的力学指标都能满足一定的强度要求。因此可以作为北方满族民居的建设材料。 相似文献
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普通混凝土具有许多优点,但其脆性大、易产生开裂,这将导致外界化学介质向内部扩散的速度加快,使建筑结构的使用寿命大幅度降低.加入聚乙烯醇纤维是解决这一问题的一种有效途径,并且能够显著改善水泥基材料的性能.论文介绍了聚乙烯醇纤维增强水泥基复合材料的国内外研究现状、动力学特性以及自愈合情况,探讨了该材料的微观设计理论,介绍了其应用,并对聚乙烯醇纤维增强水泥基复合材料研究进行了展望. 相似文献
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在实验原材料质量条件下,按相关标准试验方法测试单掺高钙粉煤灰(简称高钙灰)和复掺高钙灰以及钢渣的混凝土的凝结时间、安定性、化学收缩率以及抗压抗折强度,以研究高钙灰与钢渣在混凝土中的应用。结果表明:(1)高钙灰的掺入改善了胶砂的工作性,降低了标准稠度用水量,廷缓了胶材的初终凝时间;随着其掺量的增加,标准稠度用水量降低.初凝和终凝时间延长。(2)在取代50%的水泥条件下,高钙灰与钢渣复合比单掺高钙灰的抗折抗压强度效果好,而且高钙灰和钢渣掺量之间根据设计要求不同存在着最佳掺量配比。(3)高钙灰与钢渣取代50%的水泥时,分别采用生石灰和磷石膏进行活性激发.效果显著。 相似文献