共查询到20条相似文献,搜索用时 203 毫秒
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以聚羧酸减水剂对3D打印砂浆性能的影响为目标,选定和保持流动度基本不变,调整减水剂掺量和用水量,研究减水剂掺量对3D打印砂浆性能的影响。结果表明,随着减水剂掺量的增大,用水量降低,流动度经时损失降低,堆叠性降低,打印性能先变好后变差,强度增加,且性能变化较大或发生转折时的掺量与最大减水率对应的掺量有关。3D打印砂浆的减水剂最佳掺量不同于普通混凝土,综合考虑宜选中低掺量。 相似文献
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通过测试流动度和由Bingham流变模型拟合所得的流变参数,研究了未掺与掺聚羧酸减水剂(TX50)两种条件下含泥量对水泥浆体流变性能的影响因素及其规律.结果表明:含泥量对水泥浆体塑性黏度的影响程度明显大于其对流动度的影响;水灰比与未掺减水剂的水泥浆体的流动度、塑性黏度、屈服应力分别呈线性关系、幂函数关系、指数关系;减水... 相似文献
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研究了石材加工产生的废石粉替代部分水泥对3D打印水泥砂浆性能的影响.结果表明:总体上,随着废石粉掺量的增加,砂浆的流动度降低,静态屈服应力提高,但凝结时间变化不明显;通过调整减水剂掺量可以改善废石粉对3D打印水泥砂浆流动性和可建造性的不利影响;废石粉的掺入对3D打印水泥砂浆的力学性能和层间界面黏结强度不利. 相似文献
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采用赫切尔-巴尔克模型拟合流变曲线,研究了含水率、外加剂(聚羧酸减水剂和季铵盐型表面活性剂)对建筑渣土泥浆在不同静置时间下流变性能的影响,并阐明了外加剂的作用机理.结果表明:随着含水率的增大,建筑渣土泥浆的流变性能参数均减小;随着2种外加剂掺量的增大,建筑渣土泥浆的初始表观黏度和塑性黏度先增大后减小;建筑渣土泥浆的屈服应力随着季铵盐型表面活性剂掺量的增加而一直增大,随着聚羧酸减水剂掺量的增大先增大后减小,相同掺量下聚羧酸减水剂的作用效果更好;外加剂分子间的排斥力与黏土对外加剂的吸附力两者之间的主导作用决定建筑渣土泥浆的流变性能. 相似文献
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《Soils and Foundations》2014,54(5):955-966
The failure of a sloping ground due to static liquefaction occurs when the shear stress applied by a monotonic triggering load exceeds the undrained yield (peak) shear strength of the saturated liquefiable cohesionless soil. Current practices for determining the in-situ undrained yield strength for grounds subjected to static shear stress rely on either a suite of costly laboratory tests on undisturbed field samples or empirical correlations based on in-situ penetration tests, which fail to account for the effect of soil dilatancy in decreasing the degree of strain-softening and the brittleness of cohesionless soils with an increasing penetration resistance. In this study, the effect of soil dilatancy on the static liquefaction failure of cohesionless soils is characterized by an empirical relationship between the soil brittleness index and the undrained yield strength from a database of 813 laboratory shear tests collected from the past literature. The application of this relationship for estimating the static liquefaction-triggering strength of cohesionless soils under sloping ground conditions is validated by comparing several cases of liquefaction flow failures. Finally, a procedure is briefly demonstrated for evaluating the triggering of static liquefaction in a dyke to the north of Wachusett Dam and Duncan Dam which incorporates the dilatancy behavior of cohesionless soils in a semi-empirical procedure based on in-situ penetration tests. 相似文献
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Although the buildability of building designs has not been commonly taken as an important parameter in design quality assessment, previous studies have linked buildability to time, cost, quality and safety performance in many ways. Based on this observation, the question arises of how buildability can be benchmarked and which aspects of project performance can be improved. After identifying available benchmarking tools, the relative correlations are investigated between different buildability attributes and construction performance in terms of time, cost, quality and safety. Based on a questionnaire survey, it was found that construction time performance has strong positive correlations with buildability in the design of external wall elements, simplicity of assembly and installation considerations, while other design attributes affect cost, quality and safety performance to varying degrees. With this understanding, it is postulated that best practice can be promoted among design teams for enhancing buildability, which would in turn raise project performance. Three experienced practitioners have been interviewed for verifying the practicality of buildability benchmarking. As an incentive to improve buildability, benchmarking would help construction stakeholders reap their desired benefits by focusing on the related design attributes in the pre‐construction stage, particularly for functionally oriented buildings. 相似文献
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Luciano Senff Pedro A. Barbetta Wellington L. Repette Dachamir Hotza Helena Paiva Victor M. Ferreira João A. Labrincha 《Construction and Building Materials》2009,23(10):3107-3111
This paper reports the effects of distinct contents of silica fume (SF), superplasticizer (SP) and water/binder ratio (W/B) in mortars. Samples with SF (0–10 wt%), SP (1.0–1.2 wt%) and W/B ratio (0.30–0.35) were produced. Flow table test and rheometry were used as parameters to formulate mortars by means of a factorial design experiment. Setting time, water absorption, apparent porosity and compressive strength of mortars at 28 days were also determined. Mortar formulations with lower fluidity are restricting when a rheometer was used. For higher torques, adjustments with the regressive equation of the Bingham model are less accurate, since the flow behavior is less constant. On the other hand, mortars with higher fluidity it is limited by spread test. The spread value on flow table test is more related to yield stress than to plastic viscosity. The design experiments identified the main factors (SF, SP and W/B) and their interactions for all properties on the fresh and hardened state, showing that experimental design with multiple regression equations is an appropriate tool to be applied in this case. Water content was the controlling parameter for practically all properties studied. 相似文献
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廖绍华 《混凝土与水泥制品》2021,(2):27-31
研究了水泥用量、絮凝剂掺量、砂率对海水拌和珊瑚砂水下不分散混凝土性能的影响.结果表明:珊瑚砂水下不分散混凝土单位用水量为235~283 kg/m3时,砂率对单位用水量的影响最为显著,用水量随砂率增加而增大;水泥用量为400~490 kg/m3时,28 d抗压强度在26~39 MPa之间,可配制C20~C30水下不分散混... 相似文献
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为了实现对消火栓状态的实时监测,掌握其水压、流量、温度的数据信息,研制了消火栓监测仪,对数据传输信号强度与消火栓状态实时监测方法进行分析与研究。分析基于NBIoT网络传输的消火栓监测仪在多种空间情形下的信号强度。对市政消火栓进行实时监测,从动压与静压两方面分析其水压变化趋势。分析阀门状态、探测周期对流量监测的影响。结合当地气温验证供水管网内水源温度监测的准确性。实验结果表明:消火栓监测仪数据传输可靠,压力在0~400
kPa 范围内监测准确、流量在0.2~25 L/s 范围内测量灵敏、温度监测数据与当地气温相符,满足消火栓状态实时监测需求。 相似文献
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饱水砂岩动态强度的SHPB试验研究 总被引:2,自引:1,他引:1
采用改进的φ75mm杆径SHPB试验装置,对长径比为0.5的开阳磷矿砂岩进行自然风干和饱水状态下的冲击压缩试验,对比INSTRON材料试验机的静载试验结果表明:冲击载荷作用下饱水砂岩的应力–应变关系不同于其静态应力–应变关系,中应变率加载条件下饱水砂岩动态强度与风干砂岩的动态强度相近,这与静载条件下饱水砂岩强度降低的结果相反;风干砂岩动态屈服应力与其静态相近,饱水砂岩动态屈服应力比其静态下的结果提高近2倍,表现出比自然风干砂岩更强的应变率敏感性;水对砂岩动态破坏效果有影响,自然风干砂岩比饱水砂岩受冲击破坏更为严重;冲击载荷作用下,饱水砂岩动态强度应考虑其自由水黏度及Stefan效应的影响。 相似文献
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A new high quality steel material (SN) was developed by reducing the distribution at yield point. This steel material has
an advantage of having accurate yield strength compared to regular steel materials (SS and SM). Therefore, by using SN steel,
the collapse mechanism can be controlled as intended for design. SS, SM, and SN steel materials were tested, and variations
of yield strengths were investigated. The effect of having dispersed yield strength was investigated by conducting experiments
on 8 test specimens. Column to beam yield strength ratio was changed from intended column to beam yield strength ratio because
of the difference between the specified minimum yield stress and the actual yield strength of the steel materials, and it
affected the collapse mechanism and the overall behavior of the specimen. It was verified through static cyclic test and static
pushover analysis that the seismic performance of buildings designed using SS and SM steel could be decreased by as much as
20% compared to using SN steel. It is observed that the provision of upper bound limit on yield point in SN steel is effective
in securing seismic performance of steel buildings. 相似文献