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水泥砂浆塑性收缩开裂试验条件的研究 总被引:3,自引:6,他引:3
研究了约束状况,失水条件及试件厚度等因素对水泥砂浆塑性收缩开裂性能的影响。结果表明:(1)增加钢筋框中部约束或取消钢筋框均可减少砂浆塑性收缩开裂性能;底部凹凸状约束及面层铺设钢丝网可使砂浆塑性开裂有所减小,但不能消除塑性开裂现象;基本去除约束的准自由状态可使砂浆免除塑性收缩开裂。(2)失水条件对砂浆塑性收缩开裂有明显影响,灯与电网扇同时开启所形成的“风吹日晒”比单纯“风吹”、“日晒”更易于使砂浆塑性收缩开裂;加强抹面处理可使塑性收缩开裂减小,维持较长时间的洒水养护可消除塑性开裂现象。(3)增加试件厚度可减少砂浆的塑性收缩开裂,混凝土的抗塑性收缩开裂能力比砂浆强。 相似文献
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研究了养护温度、养护湿度和约束程度对补偿收缩砂浆抗压强度的影响规律,并对比分析了补偿收缩砂浆与基准砂浆在不同养护方式下抗压强度的差异性。结果表明:补偿收缩砂浆20℃标准温度养护下7 d抗压强度小于基准砂浆,随着养护温度的升高、养护龄期的延长或约束程度的增加,补偿收缩砂浆比基准砂浆具有更好的抗压强度。 相似文献
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研究废旧轮胎橡胶颗粒对砂浆物理、力学性能及收缩开裂性能的影响。试验结果表明:废橡胶颗粒的加入减少了拌和用水量,但不利于砂浆和易性的保持,使砂浆抗压抗折强度降低。但改善了砂浆韧性,有效抑制了砂浆的干燥收缩和早期塑性收缩开裂。 相似文献
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通过试验研究了高效减水剂种类以及在相同水灰比和相同流动度两种情况下聚羧酸系高效减水剂掺量对砂浆自收缩和干燥收缩的影响。结果表明:同水灰比、同流动度时,萘系和脂肪族减水剂增大砂浆收缩,聚羧酸系减水剂能降低砂浆收缩。同水灰比下,聚羧酸系减水剂掺量在0.6%~1.5%范围,砂浆自收缩随掺量增加变化不大,砂浆干燥收缩随掺量增加而增大。同流动度下,聚羧酸减水剂掺量在0.6%~1.5%范围,砂浆自收缩随掺量增加而增加,而砂浆干燥收缩随掺量增加而减小。 相似文献
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萘系高效减水剂对砂浆早期变形性能影响的研究 总被引:2,自引:0,他引:2
高效减水剂是高性能水泥基材料不可缺少的组分.早期收缩开裂是导致水泥基材料劣化的根本原因。本文采用多通道椭圆环收缩开裂测试手段、自由收缩和强度试验综合评价了萘系高效减水剂对水泥砂浆早期收缩开裂和强度的影响。结果表明.掺萘系高效减水剂延长了砂浆初始开裂时间.从而降低了砂浆的开裂敏感性。且高浓型比普通型更能有效地降低砂浆开裂敏感性。掺萘系高效减水剂增大了砂浆自由收缩值.砂浆自由收缩值都随着UNF掺量的增大而增大.且在同等掺量条件下.掺高浓型UNF砂浆的自由收缩值要比掺普通型UNF的略大。在干燥养护条件下.普通型UNF比高浓型UNF更能有效地提高砂浆的28d强度。 相似文献
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废石粉在商品砂浆中的应用研究 总被引:1,自引:0,他引:1
废石粉是石材加工过程中产生的废料,研究了废石粉部分取代砂用于水泥砂浆时,其掺量、温度、储存时间对预伴商品 砂浆稠度、凝结时间、收缩性、抗压强度等性能的影响。试验表明,废石粉部分取代砂,可以改善砂浆的和易性,减少砂浆收缩,提高抗压强度并有利施工。 相似文献
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掺高效减水剂水泥砂浆的早期开裂研究 总被引:9,自引:0,他引:9
采用多通道椭圆环收缩开裂试验、自由收缩试验和强度试验综合评价了萘系(UNF)、聚羧酸类(PC)高效减水剂对水泥砂浆体积稳定性及早期开裂的影响.结果表明,高效减水剂的掺入延长了水泥砂浆的初始开裂时间,从而降低了水泥砂浆的开裂敏感性.高效减水剂降低水泥砂浆开裂敏感性的效果为:聚羧酸类〉高浓型萘系〉普通型萘系.掺高效减水弃1均增大了水泥砂浆的自由收缩值,且水泥砂浆自由收缩值随着高效减水剂掺量的增加而增大.高效减水剂控制水泥砂浆体积稳定性的效果为:聚羧酸类〉普通型萘系〉高浓型萘系.聚羧酸类高效减水剂的掺入减小了水泥砂浆的最大裂纹宽度,而萘系高效减水剂的掺入则加快了水泥砂浆最大裂纹宽度的发展速度.在干燥养护条件下,掺聚羧酸类高效减水剂比掺萘系高效减水剂更能有效地提高水泥砂浆28d的强度. 相似文献
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《Construction and Building Materials》2007,21(11):2017-2022
The addition of superplasticizers is an important approach to prepare high performance cement-based materials. The effect of polynaphthalene series superplasticizer (PNS) and polycarboxylate type superplasticizer (PC) on early-age cracking and volume stability of cement-based materials was investigated by means of multi-channel ellipse ring shrinkage cracking test, free shrinkage and strength test. The general effect of PNS and PC is to increase initial cracking time of mortars, and decrease cracking sensitivity of mortars. As for decreasing cracking sensitivity of mortars, PC > H-UNF (high-thickness-type PNS) > C-UNF (common-thickness-type PNS). To incorporate superplasticizers is apparently to increases free shrinkage of mortars when keeping the constant W/B ratio and the content of cement pastes. As for the effect of controlling volume stability of mortars, PC > C-UNF > H-UNF. Maximum crack width of mortars with PC is lower, but the development rate of maximum crack width of mortars with H-UNF is faster in comparison with control mortars. Flexural and compressive strength of mortars and concretes at 28 days increased with increasing superplasticizer dosages under drying conditions. C-UNF was approximate to H-UNF, but PC was superior to PNS in the aspect of increasing strength of cement-based materials. 相似文献
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M. Katsioti D. Gkanis P. Pipilikaki A. Sakellariou A. Papathanasiou Ch. Teas E. Chaniotakis P. Moundoulas A. Moropoulou 《Construction and Building Materials》2009,23(5):1960-1965
In this work several specimens of mortars were prepared with the addition of 5% fly ash and 5% perlite and their mechanical properties and porosity were tested and compared to those of mortars with no additives (reference sample).Specifically, it was studied the influence that these additives have on the elastic modulus and porosity of the mortars.After conducting chemical, mineralogical and granulometric analysis of additives, a series of measurements were made in fresh and hardened mortars. In fresh mortars, measurements were conducted according to the EN1015-2/3/8 Standards concerning flow value, wet bulk density, air content, water demand and water retention.In hardened mortars, the measurements were made in the age of 28 days. The rate of carbonation and the formation of hydraulic phases were investigated using XRD, scanning electron microscopy (SEM) and thermal analysis (DTA–TGA). Porosity and pore size distribution of mortars were investigated by mercury intrusion porosimetry. Compressive and bending strength and adhesion were measured according to the EN1015-11/12 Standards. Finally, the Young’s elastic modulus was measured in cylindrical specimens sized 50/100 mm (diameter/height) according to ASTM C469-02 Standard.The results of the present study indicated a differentiation in the microstructure of the mortars that can be contributed to the use of different additives, such as fly ash and perlite. The three materials proved to be compatible in their mechanical behavior and appropriate for construction use.The modulus of elasticity value is related to the ratio of compressive to flexural strength and in particular, with the increase of the value of the ratio, the value of the Young’s modulus of elasticity increases. The development of the microstructure represents a major parameter to improve existing mortars and to formulate new mortars. 相似文献
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本文研究了掺两种聚合物干粉改性水泥砂浆的物理、力学性能。试验结果表明,经聚合物改性后的水泥砂浆保水性能大大改善,干燥收缩值降低,抗拉粘结强度大大提高,且砂浆具有良好的温度稳定性和环境适应性,从根本上解决了传统GKC墙体接缝材料通常所出现的易开裂、易渗水等质量问题。可作为GRC轻质隔墙板新型接缝材料加以推广。 相似文献
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影响道路水泥干缩率的几个因素 总被引:1,自引:0,他引:1
试验研究了道路水泥中各矿物组成以及掺加不同的混合材(如矿渣、粉煤灰、煤矸石、石膏等)对其干缩率的影响.结果表明,干缩率并不只是随C3A含量的增大而增大,它还与其他矿物含量有关,是各矿物共同作用的结果;在本文实验条件下,掺不同混合材的水泥干缩率不同,掺粉煤灰优于掺矿渣,而掺矿渣则又优于掺煤矸石.掺适量石膏可以补偿水泥的体积收缩,但石膏掺量过多又会影响水泥的安定性. 相似文献