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在自密实轻骨料混凝土基础之上掺入钢纤维配制出自密实钢纤维轻骨料混凝土,分析了自密实钢纤维轻骨料混凝土的抗压强度、抗拉强度等主要力学性能以及收缩、抗碳化等耐久性能,并与普通骨料自密实混凝土进行对比分析。探讨了钢纤维对于改善自密实轻骨料混凝土损伤所起的作用及其机理。结果表明:掺入钢纤维后自密实轻骨料混凝土的抗压强度增大,劈拉强度明显提高,收缩及抗碳化能力也有明显改善。与普通骨料混凝土相比,自密实钢纤维轻骨料混凝土初始裂缝的产生与发展得到有效抑制。 相似文献
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为了保证自密实轻骨料混凝土(Self-compacting lightweight concrete,SCLC)在实际工程中的安全运用,本文分别对强度为C40和C50的自密实轻骨料混凝土试件进行了高温爆裂试验。通过测定混凝土试验前后的质量、超声波速、抗压强度和抗折强度,研究了自密实轻骨料混凝土的高温性能,并和同强度的普通混凝土、轻骨料混凝土和自密实混凝土的高温性能进行了对比。结果表明,自密实轻骨料混凝土比普通混凝土易爆裂,质量损失较大,但是高温后的超声波速和残余强度损失均小于普通混凝土。 相似文献
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自密实混凝土浇筑成型后发生离析会对力学性能和耐久性能产生不同程度的危害,这一问题决定了自密实混凝土在满足施工性能的同时必须具有足够的稳定性。而自密实混凝土高流动性、高填充性及高间隙通过性等优异的工作性能特征,又决定了其拌合物的稳定性高度敏感。从静态稳定性和动态稳定性两方面分别阐述了自密实混凝土的稳定性机理,探讨了自密实混凝土静态稳定性和动态稳定性的表征方法,从配合比参数、拌合物流变性能、施工工艺等方面讨论了影响自密实混凝土稳定性的因素,提出了自密实混凝土稳定性的研究前景。 相似文献
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自密实高强混凝土框架结构的抗震性能试验研究 总被引:4,自引:0,他引:4
为了保证自密实高强混凝土框架结构在抗震地区应用的安全性,采用MTS伺服加载系统进行了二榀单层单跨框架在拟静力荷载作用下的抗震性能试验研究.在混凝土强度相近、配筋与构件尺寸一样的情况下,对比分析自密实高强混凝土框架与普通高强混凝土框架的抗震性能.在试验中观测了自密实混凝土和普通混凝土框架的裂缝开展情况、破坏过程、结构的荷载-位移滞回曲线、钢筋与混凝土应变等,对自密实混凝土框架结构抗震性能的分析研究可为自密实混凝土框架结构的工程应用提供设计参考. 相似文献
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《工程力学》2010,(12)
通过14组56根带切口自密实混凝土梁三点弯曲试验,研究不同掺量的钢纤维、聚丙烯腈纤维、钢纤维与聚丙烯腈纤维组成的混杂纤维对自密实混凝土断裂能的影响规律。试验中制作了未掺纤维且强度相近的自密实混凝土伴随试件,用以对比并计算断裂能增益比。结果表明:钢纤维能显著提高自密实混凝土的断裂能,随着钢纤维掺量的增加,其断裂能呈线性增加;聚丙烯腈纤维有利于自密实混凝土断裂能的提高,但影响较小,且非线性增加;在钢纤维体积率不变情况下,聚丙烯腈纤维有利于混杂纤维自密实混凝土断裂能的提高,但也非线性增加。在分析试验结果的基础上,提出了以混凝土抗压强度、骨料最大粒径、纤维影响系数为主要因素的纤维自密实混凝土断裂能计算模型,经过对比表明,计算模型具有良好精度。 相似文献
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林英红 《中国新技术新产品》2009,(24):77-77
近年来自密实混凝土得到了大量应用,自密实混凝土指新拌混凝土具有高流动度而不离析、不泌水和高均匀性,能在不经振捣或少振捣的情况下自流平整并自动通过钢筋间隙充满模具,达到充分密实和获得最佳性能的混凝土。自密实混凝土因其有十分良好的工作性、力学性能与耐久性,而广泛应用于浇筑量大、浇筑深度深或浇筑高度大、钢筋密集、有特殊形状等混凝土工程中。目前,自密实混凝土已经成为高性能混凝土的一个重要研究方向之一。本文着重探讨骨料对混凝土性能的影响。 相似文献
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G. Prokopski 《Journal of Materials Science》1991,26(23):6352-6356
The influence of the water/cement ratio on fracture toughness of ordinary concrete has been investigated. The stress intensity
factorK
IIc and fracture energyJ
IIc has been tested (Mode II, shearing). The concrete structure was examined by SEM and the influence of water/cement ratio on
concrete cracking has been established. 相似文献
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This study presents the fresh properties of concrete with supplementary cementitious materials (SCM) and recycled concrete aggregates (RCA), with emphasis on the feasibility of using high volumes of fly ash (FA) in RCA concrete. For this purpose, two mix families (0% coarse RCA and 100% coarse RCA) were produced, both with and without superplasticizers (SP). The coarse natural aggregates (NA) were replaced with coarse RCA at 0% and 100%, respectively. For each of the mentioned families, three incorporation levels (0%, 50% and 100%) of fine RCA were used with 0%, 30% and 60% of FA, resulting in 28 compositions. Each mix was tested in the fresh state by means of slump, density and air content. The results of this study show that RCA decreased the slump of concrete mixes, but the required water content can be minimized by incorporation FA. Regardless of the water absorption of the aggregates, for a given fine RCA incorporation ratio and the same ratio of FA, no increase in water content is required to obtain the same target slump as in the reference concrete. On the other hand, for a given coarse RCA incorporation ratio, a five times lower FA ratio is enough to obtain the same target slump as in the reference concrete. Air voids in concrete mixes were more affected by the shape of the aggregates than by their water absorption. The air content of concrete mixes increased as the incorporation levels of FA and RCA increased. However, in comparison with the individual effects, the air content decreased by combining the incorporation of both FA and RCA. Moreover, the rate of reduction in fresh density by increasing the incorporation of RCA and FA was similar in concrete mixes with and without SP. 相似文献
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《Cement and Concrete Composites》2003,25(3):357-361
This paper presents the results on investigations made into a concrete containing cement rich in granulated blast furnace slag (57%). Whereas slag cement concretes have proved successful in structures subjected to chemical attack, their use in structures subjected to freezing and de-icing salt attack is a problem of numerous investigations. The results concerning water/cement ratio and air content in concrete mixtures are presented in this paper. The effect of polypropylene microfibre addition to the concrete was also analysed. The research shows that air entraining the concrete mix up to the level of 5–6% guarantees obtaining high resistance to the action of de-icing agents, even at relatively high values of water/cement ratio. Apart the air content, the addition of microfibre to the concrete mixture was highly effective. For these samples scaling was the lowest. Phase composition investigations confirm that calcite and aragonite (as the carbonation products) were present on the surface of concrete. 相似文献
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The cement hydration equation was used to determine the influence of the water to cement ratio, W/C, on the compressive strength of concrete up to the end of the hydration age. Using the hydration equation, the equations of the compressive strength of concrete were derived for five values of the ratio W/C equal to 0.50, 0.55, 0.60, 0.65, and 0.70. The curves of variation of the compressive strength versus the W/C ratio for the hydration age of 7, 28, 90 and 5475 days were drawn. Based on these curves a thorough study of the influence of the W/C ratio on the compressive strength of concrete was undertaken. 相似文献
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Abdulrahman M. Alhozaimy 《Cement and Concrete Composites》2009,31(7):470-473
Slump loss of concrete is very important in construction practice particularly with ready-mixed concrete. It is believed that slump loss occurs due to reduction of mixing water caused by aggregate absorption, evaporation, and cement hydration. In this study, the effect of absorption of limestone aggregates on the effective w/c ratio and on the strength and slump loss of concrete was investigated. It was found that the absorption of dry aggregates in all concrete mixes considered in this study occurred mainly in the first 15 min after the start of mixing and diminished substantially thereafter. The rate of slump loss of concrete was almost identical for mixes with dry and wet aggregates, even when setting time was extended. The results indicated that limestone aggregates used in this study with an absorption capacity of 1.3–1.9% by weight can absorb about 75% of their absorption capacity when mixed in concrete. The remaining 25% will add to the free water, thus increasing the effective w/c ratio. This phenomenon was demonstrated by the increased initial slump and decreased compressive strength of mixes with dry aggregates compared to those with wet aggregates. 相似文献
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采用双层钢筋混凝土试件,研究水与水泥的质量比、氯离子含量和保护层厚度对硅酸盐水泥混凝土电化学脱盐的影响,通过测定混凝土不同深度处氯离子含量的变化,分析脱盐效率随时间的变化趋势;探讨电化学脱盐后混凝土力学性能和微观产物的变化。结果表明,混凝土各部位氯离子的脱除效率与混凝土的密实性、氯离子的浓度梯度和混凝土中的电场强度密切相关;混凝土的电化学脱盐效率随着水与水泥质量比的增加和保护层厚度的减小而提高;初始氯离子的含量对脱盐效率的影响应考虑氯离子的浓度梯度和通电量而定;电化学脱盐技术可降低混凝土中氯离子的含量,进而提高钢筋混凝土的耐久性。 相似文献
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文章从粉煤灰掺量、水胶比、砂率及混凝土含气量等几方面入手,着重对C50梁体混凝土的弹模及lOd强度进行检测,配制出了满足设计和施工要求的高性能梁体混凝土配合比,对以后铁路工程梁体配合比设计有很好的借鉴意义。 相似文献
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