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为研究水工混凝土材料在冻融循环与盐侵蚀耦合作用下构件性能演变规律,选取不同引气剂掺量(0、0.005%、0.01%)的早期受冻试件,置于质量分数为3.5%氯化钠+5%硫酸钠复合溶液内进行冻融循环试验,并基于核磁共振技术(NMR)—分形理论,构建混凝土孔体积分形维数与试件抗压强度间的耦联关系。结果表明,在混凝土材料中适量加入引气剂,可有效提高盐冻作用下构件的弹性模量、抗压强度等力学性能,并可改善孔结构,提高抗冻性;核磁共振测试的混凝土孔体积分形维数随着冻融循环次数的增加逐渐减小,表明引气剂的加入可改变初始状态下混凝土内部孔隙结构,且随着引气剂掺量的增加效果更为明显;结合分形理论建立的孔体积分形维数与抗压强度关联模型,发现分形维数DMAX与抗压强度的最佳函数关系近似指数函数,回归系数R2均大于0.85,拟合效果良好,可为混凝土结构的耐久性评估提供参考。 相似文献
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《水电能源科学》2021,39(10):152-155,163
为了研究低水胶比条件下多元复合胶凝材料的水化反应规律及影响因素,设置梯度结构低水胶比,采用等温量热法、化学结合水量法,分别研究水胶比和矿物掺合料掺量对水泥-矿渣-粉煤灰三元复合胶凝体系水化放热、水化程度的影响。结果表明,与较高水胶比体系不同,水胶比为0.20~0.30时,降低水胶比均会增大样品的最大放热速率;水胶比为0.25、0.30时,复掺矿渣-粉煤灰会延长加速期持续时间,复掺40%时加速期持续时间最长,且体系第二放热峰出现的时间也有所延迟,但进一步降低水胶比至0.20,复掺矿渣-粉煤灰则会使第二放热峰出现时间略有提前,加速期持续时间随复掺量的增加而缩短;水胶比为0.20、0.30时,复掺掺量为30%的复合体系反应程度最大,水胶比为0.25时,复掺掺量为40%的复合体系反应程度最大,且低水胶比条件下硬化浆体的反应程度与水胶比几乎呈线性关系。 相似文献
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为了研究粉煤灰掺量对抗冲磨混凝土性能的影响,使用4种掺量粉煤灰配合比(20%、30%、40%、50%),通过水下钢球法、高速水下钢球法、旋转射流法、抗空蚀试验、温度-应力法,对抗冲磨混凝土的性能进行试验研究。结果表明,同强度等级设计时,增加粉煤灰掺量,早龄期混凝土的抗压强度无明显降低,轴拉强度略降,弹模明显降低,这对早期抗裂有利;随着龄期增加,粉煤灰掺量高的混凝土后期强度增幅明显;粉煤灰掺量增加后,混凝土表面抗悬移质冲刷强度降低,但抗推移质冲磨强度未见明显下降或提高;抗空蚀强度整体上随掺量增加而提高;粉煤灰可以明显改善混凝土的抗裂性能,以90 d为设计龄期时,最佳掺量为40%。 相似文献
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根据坝体碾压混凝土性能指标和施工要求,利用单因素试验研究了坝体不同标号三级配混凝土的
粗细骨料组合、粉煤灰掺量、水胶比和砂率,并采用绝对体积法给出了施工配合比。试验结果表明,当
采用玄武岩与灰岩为粗细骨料组合、大石∶中石∶小石为35∶35∶30、砂率为32%、用水量为88 kg/m3、
粉煤灰掺量为50%时,能满足C25、C20和C15坝体碾压混凝土各项性能指标和施工要求。 相似文献
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为了减少秸秆、粉煤灰的堆积处理污染,选用秸秆-粉煤灰混凝土砌块作为研究对象,比较分析不同组分的混凝土砌块的物理抗压属性及导热性能。砌块的强度要求为C20。结果表明:将油菜秸秆掺入混凝土时,掺入秸秆的质量比例为1%、2%、3%的情况下,与普通硅酸盐混凝土相比,秸秆混凝土砌块的导热系数分别降低41.7%、47.8%、57.2%。对秸秆混凝土正交试验结果进行综合分析,得到满足C20强度的节能最优组合为秸秆材料为芝麻、秸秆掺量为2%、粉煤灰掺量为10%、水胶比为0.45,测试其抗压强度为20.12 MPa,导热系数为0.466 W/(m·K)。 相似文献
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针对沙漠砂混凝土坍落度小、强度低的缺点,通过双掺法掺加机制砂和高性能减水剂来改善沙漠砂级配、提高混凝土和易性,制备了一系列坍落度较大、强度较高的沙漠砂混凝土,并对比分析了沙漠砂混凝土与同配合比的天然中砂混凝土的坍落度、抗压强度,验证了双掺法制备的沙漠砂混凝土的优良性能。另外,为减少水泥用量,将粉煤灰替代部分水泥,采用同时掺加粉煤灰、机制砂、高性能减水剂的三掺法制备了沙漠砂混凝土,通过试验表明,利用三掺法制备水泥用量少、强度较高、坍落度较大的沙漠砂混凝土具有可行性。 相似文献
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磷酸钾镁水泥(MKPC)是一种基于酸碱反应而凝结硬化的新型胶凝材料,掺人工砂可改变其砂浆强度、表观特征和体积稳定性。利用不同人工砂掺量砂浆强度试验,研究了人工砂掺量对MKPC砂浆抗折性能和抗压性能的影响;运用X射线衍射物相分析方法(XRD)与电镜扫描方法(SEM)分析了MKPC砂浆表面的微观特征;利用对比试验分析了人工砂对MKPC砂浆体积稳定性影响。结果表明,人工砂掺量为50%的MKPC砂浆硬化体抗折强度、抗压强度最高;结构致密、界面结构完善;表现出微膨胀性,最大膨胀率为普通砂浆最大收缩率的1/6,体积稳定性良好。 相似文献
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针对水工混凝土中大面积麻面、蜂窝、孔洞等缺陷,在试件中凿除缺陷混凝土并使其形成深度和形状都相同的方形凹槽,采用正交法设计比原混凝土小一级配、强度高一等级的膨胀纤维混凝土进行修补。试验分析了不同粉煤灰掺量、纤维膨胀剂掺量、减水剂掺量和砂率对膨胀纤维混凝土抗压强度、劈裂抗拉强度和静力抗压弹性模量的影响程度,推荐出最佳配合比,并对比了原状、带缺陷和经修补后的混凝土力学性能。结果表明,纤维膨胀剂掺量是影响其抗压强度、劈裂抗拉强度和静力抗压弹性模量的最重要因素,修补后的混凝土在强度方面效果较好。 相似文献
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Satish Kumar Amanpreet Singh Hemant Kumar 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2018,40(24):2967-2973
Presently, fly ash–water slurry is transported to ash disposal site at very low solid concentration of approximately 15–20% (by weight), resulting in huge water and energy wastage which leads to several environmental and health problem. The production of a large amount of the toxic metal elements in the ash disposal system of the thermal power plants can pose negative environmental effects on human health and on plants. In the present study, an attempt has been made to investigate the leaching characteristics of fly ash at higher concentrations. The bottom ash was taken as an additive in the proportion of 10, 20, and 30% (by weight) to enhance the leaching characteristics of fly ash. The solid concentration of fly ash suspension was taken in the range of 40 to 60% (by weight). The addition of additive helps to reduce the tracing metal concentration of fly ash. Leaching experiment data show that leachate concentration of all tracing elements present in fly ash reduced maximum with 20% addition of bottom ash (by weight). The present study helps to improve the ash disposal system of the thermal power plant and to minimize the environmental impact. 相似文献
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1025t h煤粉炉在满负荷下燃用高钙低硫的神木煤时,其自身固硫率高达27%~33%。在入炉的矿物灰和钙成分中,60%左右形成飞灰,只有不到10%形成炉底渣。在入炉硫分中,70%左右以气态SO2形式随烟气排放,只有不到10%以固态形式富集于飞灰中,不到1%固定于炉底渣中。XRD定性分析表明:飞灰中因高温熔融形成的玻璃状非晶相含量比底渣中高出许多,并含有自身固硫产物CaSO4和未反应的CaO晶相。在炉底渣中并未发现CaSO4或CaO晶相,但新生成了大量的钠长石晶相。图2表7参4 相似文献
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Sangeet K. Jha Lal C. Ram 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2016,38(11):1661-1669
In India, the major source of energy is thermal power plants that contribute about 70% of the total energy requirement and produce a huge amount of fly ash per year. The fly ash and pond ash collected from the Ramagundam Super Thermal Power Station, India, were mixed with soil at different doses, 50, 100, and 200 t ha?1 separately to compare their impact on crop yield and soil characteristics. Ash application had a beneficial effect on the crop yield, apart from reduction in the required doses of chemical fertilizers by half of the recommended doses. Addition of ash resulted in a significant increase in the contents of N, P, K, S, Ca, Mg, and micro-nutrients in maize and groundnut crop produce. The uptake of toxic trace elements (Cu, Zn, Mn, Fe, Pb, and Ni) was below the threshold levels. The residual effect of ash on crop yield and the nutrient composition of the subsequent maize and groundnut crops was also significant. The overall beneficial effect of ash could be attributed to the improvement in the soil. The results indicated that both the ashes could be applied safely for reclamation of uncultivated wastelands and pond ash is found to be better than the fly ash. 相似文献
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Growth of ash deposits when wood was co-fired with coal was visually investigated in a 300 kW pilot-scale furnace. For comparison, combustion of pure coal was also conducted. A total of 10% and 20% wood were mixed with coal. The thickness and heat flux were obtained. The collected ash deposits and fly ash were characterized by a series of analysis methods to determine the physical and mineral properties. Their relationships were also revealed. Results showed that co-firing of coal with wood dramatically increased the ash deposition propensity. During the coal combustion, shedding of ash deposit occurred and the maximum deposit thickness was 15.33 mm. A deposit thickness of up to 27.02 mm was achieved for 10% wood, and the thickness increased to 34.20 mm for 20% wood. The variation in heat flux with deposit thickness substantially changed when wood was co-fired. A significant change was also observed in the mineral composition of ash deposit with the increase in wood ratio. The proportion of anorthite increased because that of lime in fly ash increased with wood ratio. In addition, the mean diameter of fly ash particles increased as wood ratio increased. 相似文献
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利用热天平实验研究了飞灰碳厦其入炉煤的反应性,从理论上分析了飞灰回燃对CFB锅炉燃烧效率的影响,并通过工业试验测试了回燃飞灰量对锅炉返料器运行温度、飞灰的粒度分布及其含碳量、锅炉燃烧效率及其它运行参数的影响。研究表明,燃烧福建无烟煤CFB锅炉飞灰碳的反应性高于其对应入炉煤。回燃飞灰的含碳量、回燃飞灰量与入炉煤量的比值等参数对锅炉燃烧效率有重要影响。采取飞灰回燃技术有利于降低飞灰含碳、降低返料器运行温度和提高锅炉燃烧效率,但当回燃飞灰量较大时会影响锅炉的稳定运行。 相似文献