含盐陶粒混凝土的盐分释放特性及路用性能

为了探究含盐陶粒表面聚合物改性水泥净浆的盐分缓释性能和不同掺量含盐陶粒对混凝土路用性能的影响,通过电导率分析法和相关力学试验,对不同掺量的含盐陶粒混凝土盐分析出量及路用性能进行了分析.研究结果表明:聚合物改性水泥净浆具有良好的盐分缓释性能;含盐陶粒的蓄盐量受动水冲刷和含盐陶粒表面覆裹层材料的磨损影响较大;含盐陶粒混凝土较普通混凝土具有更好的抑冻性能,当含盐陶粒对骨料碎石的替代率为100%时,在-2℃的环境温度下,试件表面完全冻结所需时间延长至70 min,是普通混凝土的4.67倍;含盐陶粒的掺量对混凝土的力学性能和耐磨性能均存在一定影响.     

纤维掺量对聚丙烯粗纤维陶粒混凝土力学性能的影响

在2种轻混凝土基体（LC25,LC30）和3种纤维体积掺量（0.5％,1.0％,1.5％）基础上,对聚丙烯粗纤维陶粒混凝土力学性能进行了试验研究.结果表明：陶粒混凝土立方体抗压强度、劈裂抗拉强度、抗折强度随着纤维掺量的增大,都表现出先增加后降低的特性,并且都在纤维掺量为1％时获得最大强度;而抗冲击性能则随纤维掺量增大不断提高.在实际应用时,聚丙烯粗纤维掺量不宜超过1.0％.     

可融冰含盐陶粒混凝土分层度试验

为了保证含盐陶粒混凝土路面具有良好的除冰雪耐久性,消除含盐陶粒离析分层对混凝土性能的不利影响,采用分层度试验对影响含盐陶粒混凝土匀质性的因素进行了分析.结果表明:合理的砂率能有效提高混凝土拌合物中水泥砂浆的黏度,当砂率为36%时含盐陶粒混凝土的抗分层和抗离析性能最好;用粉煤灰替代部分水泥能降低水泥砂浆与含盐陶粒的密度差异,改善混凝土拌合物的工作性,有效减弱含盐陶粒的上浮;一定时长的振捣使得混凝土胶凝材料与水充分接触,混凝土拌合物的黏度系数明显提高,过度振捣会导致含盐陶粒大量上浮;优化材料组成,严格控制含盐陶粒混凝土的振捣时长,可以保证含盐陶粒的分布与集料替代比例的关系趋于一致.     

粉煤灰掺量对水工混凝土力学性能的影响

通过粉煤灰混凝土基本力学性能试验,分析了粉煤灰掺量、水灰比、龄期等因素对水工混凝土抗压强度、劈拉强度和抗压弹模的影响,探讨了粉煤灰对混凝土力学性能的影响机理.试验结果表明,随着粉煤灰掺量的增加,混凝土的早期强度有所降低,后期强度有明显提高.     

钢纤维掺量对橡胶混凝土力学性能影响

在10%橡胶掺量的橡胶混凝土中分别添加0.5%、1.0%、1.5%、2.0%(体积占比)的钢纤维,以此为试样进行复合材料的基本力学性能试验,包括立方体试块的抗压试验、动弹性模量试验、立方体劈裂抗拉试验以及四点弯曲抗折试验,探讨钢纤维体积占比和复合材料各方面力学性能之间的关系。通过实验数据分析及破坏形态观察,发现:随着钢纤维掺量的提高,复合材料的抗压强度、弹性模量、劈拉强度、抗折强度均有所提高,韧性也有所提高。     

陶粒预湿对混凝土力学性能影响研究

陶粒吸水返水特性对混凝土的力学性能有重要影响。文章采用两种不同程度的预湿陶粒配制混凝土,进行立方体抗压实验、立方体劈拉实验、长方体弹性模量试验。试验结果表明：陶粒的孔隙率大小直接影响着陶粒的预湿程度和吸水率,吸水率大的陶粒会导致混凝土实际水灰比增大,降低了混凝土抗压强度,但劈拉强度和弹性模量变化趋势却不尽相同。     

陶粒钢纤维混凝土流动性的试验研究

结构用陶粒混凝土属脆性材料,其强度越高,脆性越大,为改善其力学性质及韧性,常掺入钢纤维将其制成陶粒钢纤维混凝土。该试验研究了钢纤维掺量在０＠－２％变化条件下的陶粒钢纤维混凝土的流动性,探讨了水泥浆数量,水泥浆稠度,骨料最大粒少率及钢纤维掺量对陶粒纤维混凝土的影响。     

外掺物对水泥混凝土路面耐磨性的影响

水泥混凝土路面耐磨性是水泥混凝土路面的重要指标之一，提高混凝土路面的耐磨性能对保证路面的使用品质具有重要意义。文章着重研究了外掺物对水泥混凝土路面耐磨性的影响，并根据室内试验与319省道路段试验，得出通过外掺物的共同作用可使混凝土路面的耐磨性有较大提高，从而为设计，施工单位提供参考依据。     

以粉煤灰取代水泥对陶粒泡沫混凝土强度的影响

本证实用粉煤灰超量取代一定数量的水泥可以提高陶粒泡沫混凝土的强度，具有显的经济效益。     

The influence of oleic acid on the hydration and mechanical properties of portland cement

To investigate the effects of OA on the portland cement using oleic acid （OA） as grinding aid and the effects of OA on the portland cement, we characterized the different perfermances of the cement, discussed the characteristics of properties. The results reveal that the OA can reduce the water requirement of normal consistency. With the content of OA added, setting time was extended. The OA can significantly improve the rheological properties of cement-based materials, while the compressive strength decreases.     

The Influence of Free Water Content on Dielectric Properties of Alkali Active Slag Cement Paste

The dielectric performance of alkali activated slag （AAS） cement paste was investigated in the frequency range of 1 to 1000 MHz. The experimental results showed the unstable dielectric properties of harden paste were mostly influenced by the fraction of free water in paste or absorbed water from ambient, but not including hydration water and microstructure. The free water was completely eliminated by heat treatment at 105 ℃ about 4 hours, and then its dielectric loss was depressed; but with the exposure time in air increasing, the free water adsorption in ambient air made the dielectric property of harden cement paste to be bad. The temperature and relative humidity of environment was the key factors of free water adsorption; hence, if the influence of free water on dielectric constant was measured or eliminated, the cement-based materials may be applied in humidity sensitive materials or dielectric materials domains.     

高掺量粉煤灰混凝土力学性能随龄期发展研究

基于粉煤灰在混凝土工程中广泛应用的现状,结合粉煤灰混凝土力学性能随龄期发展较快的特点,考虑加载龄期和粉煤灰掺量等因素,开展试验研究不同掺量粉煤灰混凝土抗压强度和弹性模量随龄期发展的规律。研究结果表明,随着龄期的发展,粉煤灰混凝土的力学性能呈增长趋势,且随粉煤灰掺量的增加,这种增长趋势愈发明显。在对试验结果分析的基础上,讨论了粉煤灰在混凝土力学性能随龄期发展的机理。对高掺量粉煤灰在混凝土中的工程应用及结构设计等方面提出了建议。     

黄土状水泥土抗剪强度特性研究

为了探索水泥土加固技术对黄土地区的适宜性及可靠性,通过室内试验,对西北地区黄土中添加一定量水泥使其形成黄土状水泥土,研究黄土状水泥土含水量、掺入比、龄期等因素对其力学特性的影响.研究表明,黄土中掺入水泥搅拌后,土的性质得到改善,降低了土的含水量,提高了土的密实度及土的强度;同时,表明黄土状水泥土的水泥掺入比较大时,水泥土的强度随初始含水量增大而增大,但水泥掺入比较小时,只有在某一最优含水量下黄土状水泥土的强度可达到最大值.     

高温作用对大掺量粉煤灰混凝土力学性能影响

研究了高温作用对大掺量粉煤灰混凝土(HFCC)立方体力学性能的影响,探讨了不同加热温度、不同粉煤灰掺量与HFCC残余强度的关系.将粉煤灰掺量30%、40%和50%的混凝土立方体试块加热至250,450,550和650℃进行强度测试,并与素混凝土(不掺粉煤灰)试块进行对比.研究结果表明,随着温度升高,HFCC残余抗压、劈裂抗拉强度均出现明显退化,劈裂抗拉强度退化尤为明显;随着粉煤灰的掺入,粉煤灰掺量对强度退化率的影响具有复杂性:高温后HFCC抗压强度退化率均低于普通混凝土强度退化率;劈裂抗拉强度退化率除粉煤灰掺量30%外均低于普通混凝土退化率.在试验基础上建立HFCC高温后立方体残余抗压强度、残余劈裂抗拉强度与温度、粉煤灰掺量的定量关系,为高温后HFCC材料强度评估及修复提供依据.     

The mechanical properties of coastal soil treated with cement

The influences of cement type, cement content, and curing time on the unconfined compression strength （UCS） of soil-cement were investigated. The influence of groundwater on UCS of soil- cement was also studied. The experimental results indicate that the soil treated with high grade cement presents a higher UCS. Additionally, the UCS of soil-cement presents linearly increased with the cement content. A logarithm correlation between UCS and curing time presents to forecast the strength development. Compared with the UCS of samples immersed in distilled water, those immersed in groundwater oresent a hizher value.     

The Mechanical Properties of Polypropylene Fiber Reinforced Concrete

The compressive, shear strengths and abrasion-erosion resistance as well as flexural properties of two polypropyenc fiber reinforced concretes and the comparison with a steel fiber reinforced concrete were reported. The exprimental results show that a low content of polypropylene fiber (0.91 kg/m^3 of concrete ) slightly decreases the compressive and shear strengths, and appreciably increased the flexural strength, but obviously enhances the toughness index and fracture energy for the concrete with the same mix proportion, coasequently it plays a role of anti-cracking and improving toughness in concrete. Moreover, the polypropylene mesh fiber is better than the polypropylene monofilament fiber in improving flexaral strength and toughness of concrete, but the types of polypropylene fibers are inferior to steel fiber. All the polypropylene and steel fibers have no great beneficial effect on the abrasion-erosion resistance of concrete.     

Effect of graphene on mechanical properties of cement mortars

Functionalized graphene nano-sheets(FGN) of 0.01%-0.05%(mass fraction) were added to produce FGN-cement composites in the form of mortars. Flow properties, mechanical properties and microstructure of the cementitious material were then investigated. The results indicate that the addition of FGN decreases the fluidity slightly and improves mechanical properties of cement-based composites significantly. The highest strength is obtained with FGN content of 0.02% where the flexural strength and compressive strength at 28 days are 12.917 MPa and 52.42 MPa, respectively. Besides, scanning electron micrographs show that FGN can regulate formation of massive compact cross-linking structures and thermo gravimetric analysis indicates that FGN can accelerate the hydration reaction to increase the function of the composite effectively.