剑麻纤维水泥混凝土性能试验研究

通过不同掺量剑麻纤维水泥混凝土物理性能力学性能试验,得出不同掺量剑麻纤维对水泥混凝土的工作性、含气量、抗压强度、劈裂抗拉强度、抗折强度、干缩值和抗冲击等性能影响的试验结果,从而获得剑麻纤维的最佳掺量范围,为进一步研究剑麻纤维水泥混凝土其它性能及应用提供参考.     

掺粉煤灰、硅粉的超短超细钢纤维超早强混凝土强度研究

本文在超短超细钢纤维超早强混凝土基础上,通过掺入粉煤灰、微硅粉等质量取代部分水泥的方式,考察其对超短超细钢纤维混凝土施工性、抗压及抗折强度的影响。研究结果表明,掺入粉煤灰可改善纤维混凝土的施工性,掺入硅粉则会造成施工性降低。掺入粉煤灰,会导致纤维混凝土的早期强度下降,但后期强度会有所提高。掺入硅粉,纤维混凝土的抗压、抗折强度总体上均随龄期呈增长趋势。采用粉煤灰与硅粉混掺时,超短超细钢纤维混凝土的后期抗折强度可获得最佳增强效果。     

微硅粉对纤维增强水泥耐久性影响的试验研究

研究了在纤维增强水泥中添加矿物细掺料微硅粉对其耐久性的影响.试验结果表明,微硅粉的掺入,明显改善了纤维增强水泥的抗反复冻融、抗反复湿热性能.分析了微硅粉对纤维增强水泥耐久性影响的作用机理及其孔结构的变化.     

纳米材料对水泥材料耐火性能的改良研究

为了改善建筑水泥墙板结构的耐火性能,利用纳米材料—微硅粉和碳纤维作为外掺料应用于改性研究。以标准砂与硅酸盐水泥质量比为2∶1制备试件,测试抗压强度、抗折强度、耐火性、干缩率并分析微观形貌。结果表明,微硅粉和碳纤维在提高水泥墙板材料抗压和抗折强度的同时,也改善了材料的耐火性能;双掺微硅粉和碳纤维含量为3%和2%的水泥墙体具有最优的耐火性能,燃烧试验后的质量损失为0.64%,比参照组烧失量降低了85%;从水泥基改性材料微观形貌发现,超细硅粉颗粒的填充效应是材料强度性能提升的主要原因,碳纤维的粘结作用和表面反应是耐火性能提高的主要原因。     

超细钢纤维增强粉煤灰水泥基材料的力学性能和干缩研究

研究了超细钢纤维增强粉煤灰水泥基材料在不同养护条件下的抗压、抗折强度发展,以及其干缩发展规律。试验结果表明:超细钢纤维增强粉煤灰水泥基材料标养28 d及蒸养3 d抗压强度最高可达到106.6和109.4 MPa,蒸养和水浴可提高水泥基材料早期强度。水泥基材料抗压强度随纤维掺量增加先轻微下降后增加,其抗折强度随钢纤维掺量增加而线性增加。钢纤维增强水泥基材料干缩与龄期符合指数函数关系,其15 d最大干缩值为0.000 521 mmmm,其3 d内的干缩应变均达到后期干缩应变的50%以上。钢纤维掺入水泥基材料干缩值最大降低了15.3%,且将干缩值趋于稳定的龄期提前;抗压强度及抗折强度随钢纤维的掺量增加,抗压强度增加值不超过25%,抗折强度最大增加接近50%。     

矿物掺和料对玄武岩纤维水泥砂浆强度发展的影响

研究了粉煤灰和硅灰对玄武岩纤维增强水泥基材料强度发展规律的影响,分析了粉煤灰和硅灰复掺对水泥砂浆中玄武岩纤维耐腐蚀性的影响.结果表明：玄武岩纤维对水泥基材料的早期抗折强度具有增强作用,后期增强效果下降,甚至会降低基体强度;粉煤灰和硅灰可显著延长玄武岩纤维对水泥砂浆抗折强度增强效果的时效.XRD图谱和显微结构分析表明,粉煤灰和硅灰复掺后降低了水泥基体中Ca(OH)2晶体的含量和玄武岩纤维的腐蚀程度,改善了玄武岩纤维和水泥基体之间的界面性质.     

纤维增强泡沫混凝土性能试验研究

以普通硅酸盐水泥为结合剂,用粉煤灰和微硅粉取代砂和部分水泥制备泡沫混凝土.探讨了微硅粉和聚丙烯纤维对表观密度为800~1 500 kg/m3的泡沫混凝土抗压强度、劈裂抗拉强度、收缩率的影响.结果表明:采用掺加微硅粉和聚丙烯纤维技术,可以制备出表观密度在800~1 500kg/m3,抗压强度达到10~50 MPa的高强泡沫混凝土;微硅粉和聚丙烯纤维能显著提高泡沫混凝土的抗压强度,且泡沫掺量越大,其增强效果越显著;掺入聚丙烯纤维后,泡沫混凝土的劈裂抗拉强度显著提高,干缩率明显下降.     

大理石粉对水泥基胶凝材料性能影响研究

研究了大理石粉对水泥基胶凝材料流动性、强度和干缩的影响。研究得出,大理石粉增加了水泥胶砂的流动性,大理石粉掺量越大其流动度越大。水泥胶砂1 d和3 d抗折和抗压强度随大理石粉掺量增加先增大后减小,大理石粉掺量为5%其抗折和抗压强度最大;水泥胶砂7、28、56 d抗折和抗压强度随大理石粉掺量增加而减小。水泥胶砂干缩随大理石粉掺量增加呈现先减小后增大的规律,大理石粉掺量为20%时其干缩最小。     

硫铝酸盐水泥熟料与磨细高炉矿渣粉复掺改性脱硫建筑石膏性能研究

研究了硫铝酸盐水泥熟料(SAC)与磨细高炉矿渣粉复掺改性对脱硫建筑石膏抗折强度、抗压强度、吸水率、饱水强度、绝干强度、软化系数的影响,并进行了微观分析.结果表明,SAC和磨细高炉矿渣粉掺量均为16％时,复掺改性脱硫建筑石膏的抗折强度、抗压强度、饱水强度、绝干强度、软化系数均明显提高,吸水率较低,微观结构中片状物体搭接效...     

聚乙烯醇纤维泡沫混凝土的性能试验

利用实验室自制的蛋白类发泡剂,以普通硅酸盐水泥为结合剂,制备了粉煤灰-水泥基泡沫混凝土。探讨了聚乙烯醇纤维不同长度、掺量对表观密度为700～800kg/m3的泡沫混凝土吸水率、抗压抗折强度、劈裂抗拉强度、收缩率的影响。结果表明,聚乙烯醇纤维可显著增强泡沫混凝土的抗折强度,当纤维长度为12mm、体积率为0.23%时,28d抗折强度增大了43.24%;纤维体积率0.08%时,纤维长度为6mm的泡沫混凝土抗压抗折强度最高。     

乳胶改性的碳纤维增强砂浆

本文介绍了乳胶改性对含有硅灰的碳纤维增强砂浆之性能特征的影响。在国外的研究中使用了两种苯乙烯-丁二烯乳胶。据观测,乳胶改性提高了胶结料与碳纤维的粘结力。乳胶改性的纤维水泥复合物同未改性者相比较,其吸水率和干缩率均降低了,而弯曲延性则提高了。乳胶改性的碳纤维增强砂浆具有较高的抗冻性,而且在耐酸性方面有明显提高。     

Effect of electric arc furnace dust on the properties of OPC and blended cement concretes

This paper presents results of a study conducted to evaluate the mechanical properties and durability characteristics of ordinary Portland cement (OPC) and blended cement (silica fume and fly ash) concrete specimens prepared with electric arc furnace dust (EAFD). Concrete specimens were prepared with and without EAFD. In the silica fume cement concrete, silica fume constituted 8% of the total cementitious material while fly ash cement concrete contained 30% fly ash. EAFD was added as 2% replacement of cement in the OPC concrete and 2% replacement of the total cementitious content in the blended cement concretes. Mechanical properties, such as compressive strength, drying shrinkage, initial and final setting time, and slump retention were determined. The durability characteristics were evaluated by measuring water absorption, chloride permeability, and reinforcement corrosion. The initial and final setting time and slump retention increased due to the incorporation of EAFD in both OPC and blended cement concretes. The drying shrinkage of EAFD cement concrete specimens was more than that of concrete specimens without EAFD. The incorporation of EAFD was beneficial to OPC concrete in terms of strength gain while such a gain was not noted in the blended cement concretes. However, the strength differential between the blended cement concretes with EAFD and the corresponding concretes without EAFD was not that significant. The water absorption and chloride permeability, however, decreased due to the incorporation of EAFD in both the OPC and blended cement concretes. The corrosion resistance of OPC and blended cement concrete specimens increased due to the addition of EAFD.     

矿物掺合料对硫铝酸盐水泥-普通硅酸盐水泥复合体系性能的影响

研究了矿粉、硅灰和粉煤灰3种矿物掺合料对硫铝酸盐水泥-普通硅酸盐水泥复合体系的标准稠度用水量、凝结时间、水化放热、胶砂抗折及抗压强度、砂浆干缩率、抗硫酸盐侵蚀性能和水化产物的影响。结果表明:随矿物掺合料掺量的增加,复合体系的标准稠度用水量增大,凝结时间延长;掺加矿物掺合料后水化放热峰出现时间延后,总水化放热量减少,其中掺加矿粉和硅灰的试件初期水化速率减慢程度较掺加粉煤灰试件更明显;3种矿物掺合料对复合体系强度的影响差别较大,掺加3%硅灰的试件3 d抗压强度增长较快;硅灰的掺加会使砂浆干缩率增大,矿粉、粉煤灰的掺加可以减小砂浆试件的干缩;矿物掺合料的掺加会提高胶砂试件抗硫酸盐侵蚀性能,掺粉煤灰的试件抗硫酸盐侵蚀性能最好。     

不同龄期下双掺矿物掺合料对GRC构件抗弯、抗冲击强度及抗渗性能的影响

针对实际工程应用中玻璃纤维增强水泥(GRC)试件存在表面微裂纹以及在潮湿环境下强度和韧性较低等问题,采用加速老化法(50 ℃热水加速老化)对双掺矿物掺合料以改性普通硅酸盐水泥为基材的GRC试件抗弯强度、抗冲击强度以及抗渗性能进行试验,并通过扫描电镜试验分析GRC试件玻璃纤维网格布表面的侵蚀情况。结果表明:无论是在50 ℃热水加速老化条件下还是在自然环境下,提高GRC试件抗冲击强度的最佳掺量(质量分数)为10%硅灰和20%偏高岭土; 双掺10%硅灰、20%粉煤灰以及双掺10%硅灰、20%偏高岭土能够显著提高GRC试件抗弯强度; 双掺20%粉煤灰、20%偏高岭土的GRC试件抗渗性能优异; 玻璃纤维网格布侵蚀程度与其宏观力学性能呈负相关; 掺入一定比例的矿物掺合料可以改善玻璃纤维网格布的抗侵蚀性能,同时改善界面区微观结构,对GRC试件的耐久性能有较大提升。     

高性能混凝土的自收缩性能研究

实验研究了混凝土干缩及自收缩性能，结果表明，高性能混凝土具有严重的自收缩现象，但整体的干缩与普通混凝土相似，掺入硅灰将将大高性能混凝土的自收缩。     

The effects of silica fume and polypropylene fibers on the impact resistance and mechanical properties of concrete

Impact resistance and strength performance of concrete mixtures with 0.36 and 0.46 water–cement ratios made with polypropylene and silica fume are examined. Polypropylene fiber with 12-mm length and four volume fractions of 0%, 0.2%, 0.3% and 0.5% are used. In pre-determined mixtures, silica fume is used as cement replacement material at 8% weight of cement. The results show that incorporating polypropylene fibers improves mechanical properties. The addition of silica fume facilitates the dispersion of fibers and improves the strength properties, particularly the impact resistance of concretes. It is shown that using 0.5% polypropylene fiber in the silica fume mixture increases compressive split tensile, and flexural strength, and especially the performance of concrete under impact loading.     

硅灰对铝酸盐水泥胶合剂性能影响的试验研究

通过引入硅灰来改善铝酸盐水泥后期强度倒缩的问题,采取内掺的方式,研究了硅灰掺量对铝酸盐水泥胶合剂性能的影响.结果表明:适宜掺量下,硅灰能大大改善铝酸盐水泥的工作性能、力学性能和收缩性能,当内掺8％硅灰时,其早期抗压强度虽低于空白组,但28 d抗压强度接近空白组,达到123.6 MPa,且56 d抗压强度持续提高至127...     

The effect of Persian Gulf tidal zone exposure on durability of mixes containing silica fume and blast furnace slag

In this research the performance of cement paste and concrete mixes incorporating 7% and 10% of silica fume (SF) as a cement replacement was investigated in three exposure conditions. The results showed that plain type II portland cement performed better than blended SF cement under cyclic wetting and drying conditions. Silica fume specimens under cyclic wetting and drying conditions in simulated seawater exhibited higher strength loss compared to plain type II portland cement where cured under potable water. In addition, the greater the silica fume amount used in the mixes, the more the capillary water absorption under tidal zone exposure or/and under wetting and drying simulation. Further, the ternary blended ground granulated blast furnace slag (GGBS) mix was the worst performing mix in all exposure conditions.     

Effect of environmental conditions on the properties of concretes with different cement types

The paper reports on the changes in properties of concretes with different cement types associated with environmental conditions. Three strength classes with three different cement types (ordinary portland cement PC 42.5 (CEM I 42.5), portland composite cements PKC-A 42.5 (CEM II/A-M 42.5) and PKC-B 32.5R (CEM II/B-M 32.5R)) were used in the study. Also, a mixture was prepared with PC 42.5 and silica fume (SF). The effects of variable ambient conditions on plastic shrinkage of fresh concrete and cement paste, compressive strength, modulus of elasticity, capillary absorption and drying shrinkage of hardened concrete were investigated. In contrast to PC 42.5 cement paste, plastic shrinkage cracks were observed in PKC-B 32.5 and PKC-A 42.5 pastes. Water absorption coefficients of all concretes stored in natural environment were higher at all ages as compared to coefficients of concretes kept in laboratory. Drying shrinkage values of concrete with SF, except the first week, were significantly lower than those of others. Although different behaviors for different cement types were observed, water–cement ratio was one of the dominating factors determining the behavior of concrete. This ratio should be lowered to improve the durability of concrete.