共查询到19条相似文献,搜索用时 500 毫秒
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北方跨海长桥对混凝土性能要求很高,超塑化剂的使用很好地解决了高性能混凝土的低水胶比和低用水量与良好工作性之间的矛盾.详细分析了该类塑化剂对混凝土工作性、匀质性、体积稳定性和耐久性的影响,阐述了塑化剂应用中存在的对产品性能认识不足、原材料不稳定引起的混凝土性能降低以及施工工艺不匹配的问题.提出应严格控制由羧酸系超塑化剂引入混凝土的气泡量,限制使用通过引气来提高减水率的塑化剂产品,尽快规范高性能混凝土的施工工艺. 相似文献
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介绍JM-PCA(Ⅰ)的羧酸类梳型接枝共聚物超塑化剂的性能特点及其高性能混凝土的应用。该聚合物在混凝土中掺量很低(水泥用量的0.15%~0.3%)的情况下,不但有很高的减水率,而且具有优异的流动性保持能力,新拌混凝土坍落度1h都是增加的。 相似文献
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减水剂又称塑化剂,能使混凝土拌合物在相同的工作性下,减少单位用水量。混凝土中掺入适量的减水剂,可在保持新拌混凝土工作性不变的情况下,显著地降低水灰比,或在水灰比不变的条件下,大大改善混凝土的工作性,从而提高混凝土的强度,改善混凝土抗冻、抗渗、收缩等一系列性能。掺减水剂后,混凝土的减水率一般为10%左右,但若掺高效减水剂,则减水率可高达20~30%。为了区别于普通减水剂,高效减水剂又称为超塑化剂。 相似文献
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氨基磺酸系高效减水剂的合成及应用特性 总被引:6,自引:0,他引:6
本文介绍了氨基磺酸系高效减水剂的合成基本路线及合成产物的分子特点,通过水泥净浆和混凝土试验研究了新型高效减水剂的特性。结果表明,氨基磺酸系高效减水剂具有突出的减水增强效果,在低掺量水平时即具有较大的减水率,掺量较高(≥0 75%)时,不仅具有更高的减水率,且自身即具有延缓坍落度损失的功能,但单掺使用时易导致粘聚性和保水性不良,与粉煤灰、矿渣、硅灰等复掺时,拌合物和易性很好,特别适合与粉煤灰、矿渣、硅灰等复掺使用配制泵送、自流平、高强高性能混凝土。 相似文献
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介绍JM—PCA(I)的羧酸类梳型接枝共聚物超塑化剂的性能特点及其高性能混凝土的应用。该聚合物在混凝土中掺量很低(水泥用量的0.15%~0.3%)的情况下,不但有很高的减水率,而且具有优异的流动性保持能力,新拌混凝土坍落度1h都是增加的。 相似文献
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一种聚羧酸系高效减水剂的试验研究 总被引:1,自引:0,他引:1
主要研究以烯丙醇聚氧乙烯醚、丙烯酸、马来酸酐和甲基丙烯磺酸钠为主要原料的聚羧酸系减水剂的合成工艺,探讨了影响减水剂性能的各种因素,得到最佳工艺条件,并对减水剂的性能进行测试。结果表明,该聚羧酸减水剂具有低掺量、高分散性、高减水率等特点。在掺量为0.25%时,初始水泥净浆流动度达310 mm,减水率高达30.5%,混凝土的抗压强度得到大幅度的提高,适宜配制高性能混凝土。 相似文献
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Construction system using prefabricated concrete elements with vacuum insulation panels. Prefabricated concrete elements with vacuum insulation panels (VIPs) have been developed with a thickness of 27 cm and a thermal transmission coefficient (U‐value) of only 0.15 W/m2K. Various strategies have been developed to safely integrate the VIPs and reduce thermal bridges in the prefabricated conrete element. The practicability of the elements has been put to the test in a demonstration house in Ravensburg/Germany. 相似文献
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Internal curing (IC) is an effective method for improving performance of low W/C – low permeability concretes because they require additional water to hydrate the cementitious materials. Conventional concretes, on the other hand, contain enough water to hydrate the cementitious materials, but are frequently not properly cured, allowing drying and compromising strength gain and durability. The aim of this investigation is to assess the effect of IC as a complement to traditional curing in relatively high W/C concretes (W/C above 0.42) under drying conditions. Degree of hydration, compressive strength, and permeability were measured in concretes with IC and without IC. Results show that even under drying conditions, mixtures with IC exhibit 16% higher hydration, 19% higher compressive strength, and 30% lower permeability than their counterparts with no IC. This suggests that IC can be very useful for improving performance in concrete mixtures with relatively high W/C under poor curing conditions. 相似文献
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Mamdouh T. Ghannam 《国际自然能源杂志》2016,37(1):24-28
The addition of water dispersed phase into the diesel continuous phase will lead to the formation of water-in-diesel (W/D) emulsion, which significantly reduces the pollution level of NOx and particulate matters in the diesel engines. The study of the rheological properties of stable W/D emulsions is important to understand the flow characteristics of these emulsions. Pure diesel fuel and three samples of W/D emulsions (10%, 20%, and 30% by volume water) were examined. Pure diesel fuel exhibits a Newtonian profile since its viscosity remains constant with the shear rate. All W/D emulsions display higher viscosity than diesel fuel with non-Newtonian flow behaviour of yield pseudoplastic response. The viscosity of the W/D emulsions decreases with the shear rate and water addition. The flow behaviour of pure diesel fuel can be described by the Power law model. The Casson model very sufficiently fits the flow behaviour of different W/D emulsions. 相似文献
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基于最优化方法,给出使用同轴双圆柱流变仪来获取胶凝材料浆体的Bingham流变参数的途径;探究五种矿物掺合料(粉煤灰、矿渣粉、硅灰、石英粉、粉煤灰微珠)和两种化学外加剂(减水剂与引气剂)对胶凝材料浆体流变参数的影响。研究结果表明:矿物掺合料等体积替代水泥相对于等质量替代水泥,对降低浆体的屈服应力和塑性黏度有利。粉煤灰可降低浆体的屈服应力和塑性黏度;矿渣粉和石英粉可降低高水胶比浆体的屈服应力和塑性黏度,但增大低水胶比浆体的屈服应力和塑性黏度;硅灰可显著提升浆体的屈服应力;粉煤灰微珠可降低浆体的塑性黏度但增大其屈服应力。减水剂可降低浆体的屈服应力和塑性黏度;引气剂可降低浆体的塑性黏度。矿物掺合料和化学外加剂对胶凝材料浆体的Bingham流变参数的影响,取决于水胶比、矿物掺合料或化学外加剂的掺量、矿物掺合料颗粒粒径、粒形和水化活性等因素,因此使得胶凝材料浆体的流变参数随着矿物掺合料和化学外加剂种类和掺量的变化,表现出非线性特征。 相似文献
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《Construction and Building Materials》2005,19(8):612-618
A class-F fly ash was used in making masonry mortars suitable for brick joints and for plastering. The mortars were made of a locally produced mixed cement and fly ash at 20% and 40% cement replacement with and without the addition of an air entraining agent/plasticiser. The testing programme includes the determination of water demand, relations between water-to-binder ratio and flow, setting time, air content, water retention, compressive strength and flexural strength.The obtained results suggest that fairly coarse grade class-F fly ash can be incorporated into mortars as replacement of the mixed cement for joint and plastering. The main concern is the low water retention which would be minimized by using a better grade/finer fly ash or by incorporation of plasticiser. Mixed cement containing 20–40% fly ash can be used to make Type N or Type S mortars. Furthermore, relations between flow values and water to binder ratio (W/B) of the mixed cement containing fly ash are developed as a practical aid for selection and formulation of mortar for brick construction and rendering/plastering. 相似文献