纤维复合胶粉改性混凝土的弹性模量与强度的相关性

通过正交试验研究分析了纤维、胶粉以及硅粉复合改性混凝土的抗压强度和弹性模量,分析了纤维复合胶粉改性混凝土抗压强度与弹性模量的关系。研究表明:聚丙烯纤维复合胶粉改性混凝土的抗压强度与弹性模量符合Ec=0.278fc+19.209线性关系,相关性十分显著;正交试验四个参数对混凝土的抗压强度和弹性模量的影响主次顺依次为胶粉掺量、硅粉掺量、纤维掺量、纤维长度,且胶粉能明显减小抗压强度和弹性模量;硅粉对混凝土抗压强度的增强效应在其掺量为2.5%时最佳。     

外掺硅粉混凝土早龄期强度及弹性模量试验研究

为了研究外掺硅粉混凝土早龄期的抗压强度及弹性模量,以不同硅粉掺量及时间龄期为变化参数,共设计并完了168个棱柱体试块的静力加载试验。观察了试件的破坏形态,获取了外掺硅粉混凝土早龄期抗压强度及变形等关键特征参数,揭示了外掺硅粉对混凝土早龄期强度和弹性模量影响的变化规律。研究结果表明:外掺硅粉可细化混凝土内部的孔结构,减少骨料与水胶体间的孔隙率,增加混凝土的密实度,从而有效提高混凝土的早期强度和弹性模量;当外掺硅粉掺量为1.4%对混凝土力学性能的提高最显著,其中3 d强度提高了35%,弹性模量提高了62.7%。     

添加粉煤灰和硅粉的路面高性能再生混凝土冻融特性试验研究

在分析影响混凝土冻融特性的主要影响因素的基础上,利用冻融循环试验,对比研究了普通混凝土、添加粉煤灰和硅粉的高性能混凝土及高性能再生混凝土的冻融特性。试验结果表明,外掺粉煤灰和硅粉能显著提高普通混凝土和再生混凝土的抗压强度,并显著改善其抗冻性能;添加粉煤灰和硅粉能有效提高再生混凝土的抗压强度,且高于相同配合比的普通混凝土,高性能再生混凝土的抗冻性能接近于普通混凝土,符合实际工程的需要;冻融循环前期的抗冻性能劣化较后期更为严重,建议加强早期的养护。     

高性能再生混凝土基本力学性能研究

对高性能天然和再生骨料混凝土进行了基本力学性能试验,测得了其立方体抗压强度、棱柱体轴心抗压强度、抗拉强度、弹性模量。试验结果表明：高性能再生骨料混凝土的上述四个力学性能指标数值均小于天然的,而且抗拉强度和弹性模量降低幅度更大;随强度等级提高,棱柱体轴心抗压强度和抗拉强度与立方体抗压强度之比却是逐渐增大,其脆性也就越大。建立了高性能混凝土与高性能再生混凝土弹性模量与立方体抗压强度之间的公式。     

硅粉高性能混凝土强度及抗氯离子渗透性能研究

文中主要对不同养护龄期及不同硅粉掺量对高性能混凝土抗压强度、抗拉强度、抗氯离子渗透性的影响进行研究。研究结果表明，混凝土的坍落度与硅粉掺量呈现负相关关系，且在高掺量硅粉时，混凝土的坍落度下降幅度增加；硅粉高性能混凝土抗压强度、抗拉强度及氯离子扩散系数均与养护龄期成正相关关系；混凝土力学性能与硅粉掺量呈现先正相关后负相关的关系，氯离子渗透系数与硅粉掺量呈现先负相关后正相关的关系；当硅粉掺量为5%时，混凝土的力学性能及耐久性能均达到最佳。     

复合胶凝材料对高性能膨胀混凝土力学性能的影响

结合试验研究,分析了水泥、粉煤灰、矿渣组成的多元复合胶凝材料对高性能膨胀混凝土强度以及弹性模量的影响.同时将国内外学者提出的高性能混凝土和高性能膨胀混凝土弹性模量的计算公式与试验数据进行了拟合分析,并研究了弹性模量和抗压强度的相关性.     

高性能混凝土抗冲磨性能试验研究

通过对掺硅灰和减水剂的高性能混凝土与普通混凝土的抗压强度与抗冲磨性能对比研究,表明硅粉高性能混凝土具有良好的抗冲磨性能。并且指出了一些影响混凝土抗冲磨性能的因素,同时也表明利用现有规范中的方法对混凝土的抗冲磨性能进行研究具有某些不足,应该对现有规范中的试验方法进行一些修改。     

拉会大桥高性能硅粉混凝土试验研究

对拉会大桥预应力混凝土连续刚构桥采用的C50高性能硅粉混凝土进行了试验研究,主要研究硅粉掺量对C50高性能混凝土的工作和易性、抗氯离子渗透和抗碳化的影响。试验结果表明:掺入适量硅粉有助于提高高性能混凝土和易性,同时对改善混凝土抗氯离子渗透和抗碳化等耐久性有显著作用。根据试验确定拉会大桥C50高性能混凝土硅粉掺量为5.66%,据此制备的混凝土各方面性能较优,能满足规范和设计要求。     

硅灰配制海工自密实高性能混凝土的研究

开展了复掺硅灰与矿渣粉海工自密实高性能混凝土的试验研究.试验结果表明,矿渣粉较大的海工自密实混凝土工作性较差,采用硅灰替代矿渣粉可改善海工自密实混凝土的工作性,在复掺硅灰和矿渣粉总掺量为70％,硅灰掺量5％的条件下,掺入55％～65％矿渣粉自密实混凝土具有较高的流动性、填充性、间隙通过性和抗离析性等工作性;28 d抗压强度大于50 MPa,56d的电通量小于1 000C,90d扩散系数小于1.5×10-12 m2/s,具有较高的抗压强度和抗氯盐侵蚀性能,满足海洋环境下抗氯盐侵蚀的质量要求.     

生态纤维对水工混凝土抗冲磨性能影响的试验研究

对掺加生态纤维、硅粉、粉煤灰和减水剂的高性能混凝土进行抗冲磨性能试验,结果表明生态纤维能够明显地提高混凝土的抗冲磨性能,对流动性和抗压强度有降低作用,但影响较小。     

聚丙烯腈纤维混凝土基本力学性能的试验研究

针对聚丙烯腈纤维混凝土的基本力学性能进行室内试验研究,研究纤维掺量与混凝土的轴压强度、劈拉强度、抗折强度以及弹性模量之间的关系。试验结果表明,与素混凝土相比,聚丙烯腈纤维混凝土的轴压强度、劈拉强度、抗折强度以及弹性模量均随纤维体积率的增加而提高,尤其是劈拉强度和抗折强度的提高幅度更大。此外,在低掺量的情况下,聚丙烯腈纤维混凝土存在一个最佳的纤维体积率。     

重复压应力作用下矿渣混凝土变形性能

采用WHY全自动应力试验机测量了最大压应力为轴心抗压强度8096重复5次时混凝土的变形。结果表明磨细矿渣对混凝土的变形性能有显著影响。磨细矿渣掺量从10％增加到30％时，混凝土28d抗压强度和静弹性模量随矿渣掺量增加而增加，最大变形随矿渣掺量增加而减小，矿渣掺量为10％和20％时，混凝土的残余变形略大于基准混凝土；矿渣掺量为40％时，28d抗压强度和静弹性模量低于基准混凝土，最大变形和残余变形均明显大于基准混凝土的变形。     

Silica fume admixture effect on the dynamic properties of concrete

The construction of concrete structures using silica fume (SF) additions is a common practice because it is well known that this pozzolanic material improves the compressive strength of concrete, among many other mechanical and physical properties. The response of a structure under dynamic actions is highly determined by the dynamic mechanical properties of its building material. In this work, it has been studied the influence of SF additions in quantities ranging from 0% to 15% of cement mass on the dynamic and static mechanical properties of concrete, such as: resonant frequencies, dynamic and static modulus of elasticity, damping ratio, compressive strength and flexural strength. The results prove that SF additions or replacements reduce both the dynamic modulus of elasticity and damping ratio of concrete. The dynamic elastic properties of concrete, with and without SF, present higher values than their static counterparts. These differences are smaller in concretes containing SF.     

钢纤维改善轻骨料混凝土力学性能的试验研究

研究了钢纤维掺量不同(体积分数分别为0,0.5%,1.0%,1.5%,2.0%)的钢纤维轻骨料混凝土(SFLWC)静态力学性能和自由落锤抗冲击性能,其中的静态力学性能包括立方体抗压强度、轴心抗压强度、劈裂抗拉强度、抗折初裂强度、抗折强度、静力受压弹性模量、抗折模量和弯曲韧性等.试验结果表明:掺入钢纤维能显著提高轻骨料混凝土的劈裂抗拉强度、抗折强度、弯曲韧性和抗冲击性能,但对轻骨料混凝土的抗压强度和弹性模量影响较小.另外,钢纤维的掺入提高了轻骨料混凝土的拉压比,很大程度上改善了轻骨料混凝土的脆性.     

Influence of supplementary cementitious materials on engineering properties of high strength concrete

The influence of supplementary cementitious materials (SCMs), namely silica fume, metakaolin, fly ash and ground granulated blast-furnace slag, on the engineering properties of high strength concrete (HSC) has been investigated in this study. Workability, compressive strength, elastic modulus, porosity and pore size distribution were assessed in order to quantify the effects of the different materials. The results show that the inclusion of the different SCMs has considerable influence on the workability of HSC. Silica fume and metakaolin significantly enhanced the strength of HSC. Fly ash reduced the early-age strength; however, it enhanced the long-term strength of the HSC. Likewise, ground granulated blast-furnace slag impaired the early-age strength, but marginally improved the long-term strength at low replacement levels. The general effect of the different SCMs on the elastic modulus of HSC is rather small compared to their effect on strength. There are good correlations between both static and dynamic moduli and compressive strength. The EC 2 and ACI 209 provide a good estimate of static modulus of elasticity from compressive strength, while the BS8110 gives a good estimate of static modulus of elasticity from dynamic modulus of HSC containing the different SCMs. Porosity and pore size were reduced with the addition of the different SCMs. The volume of mesopores in the ranges of <15 nm and 15 – 30 nm was notably increased for HSC containing SCMs, whereas the percentage of macropores was significantly reduced.     

冻融作用下混凝土性能的变化规律

通过试验研究不同强度的混凝土在冻融循环下其动弹性模量、静弹性模量和轴心抗压强度随冻融次数的变化规律,并结合理论分析,分析出冻融次数与混凝土梁的曲率、抗弯强度之间的关系。研究显示,冻融作用不仅使混凝土性能从材料层面产生劣化,并且进一步从结构角度上影响着混凝土建筑的使用功能,因此,有必要从材料和结构双方面对混凝土的受冻劣化标准进行规范。     

玻璃纤维与聚丙烯纤维混杂掺入活性粉末混凝土的力学性能

为了改善活性粉末混凝土的力学性能,采用了在活性粉末混凝土中混合掺加两种纤维的方法,即中等模量的耐碱玻璃纤维和低模量的聚丙烯纤维。本文通过两种纤维掺量的改变,研究二者混杂对活性粉末混凝土抗压强度、抗折强度力学性能的影响。从试验结果可以看出:两种纤维混杂后活性粉末混凝土的力学性能能够得到一定程度的改善。     

The effect of alkali reactivity on the mechanical properties of concrete

The effects of highly reactive aggregate, fused silica, and slowly reactive aggregate, Thames Valley sand, on the mechanical properties of concrete were investigated in this paper. The mechanical properties studied over a period of 12 months were the compressive strength, direct tensile strength, tensile splitting strength, flexural tensile strength (modulus of rupture), static modulus of elasticity and water absorption. The effects of both reactive aggregates on the mechanical properties of concrete were compared with that of sound concrete mix. The results presented in this investigation show that the effect of the reactive aggregates on the mechanical properties varies, depending on the type of reactive aggregate. From this study it appears that the direct tensile and static modulus of elasticity were the best indicators of reactivity.     

Estimation of the modulus of elasticity of slag concrete by using composite material models

In recent times, many researchers are attempting to predict the elastic properties of concrete by using previous work or composite models. In this study, it is aimed to apply composite material models to estimate the modulus of elasticity of slag concrete. The compressive strengths of wet cured slag concrete with different slag content and water to cement (w/c) ratios, are used in the calculation of the modulus of elasticity by using methods developed by previous works. The previous work model estimations are firstly assumed as the reference values of modulus of elasticity of slag concrete. Then, modulus of elasticity is also estimated by using composite models and compared to the reference modulus of elasticity. It is observed that composite models can also be employed to estimate the modulus of elasticity for slag concrete, using the assumptions of the moduli of elasticity cement and aggregate phases given in this study, where only the compressive strengths are determined by experimental tests.     

国外高性能混凝土的发展及其在复杂工程和超大型工程中的运用

高性能混凝土具有许多卓越的特性,但是其最重要的性能就是强度高。其高强度的产生是由于高性能混凝土内部所具有的特殊紧密矩阵所形成的。高性能混凝土的其它优良特性一般包括良好的延性和强度、收缩性;具有和普通混凝土相同的骨料但其弹性模量明显高于普通混凝土。高性能混凝土的弹性模量几乎可与铝相比较[1];非常好的不可渗透性,其不可渗透性低于自然界中的任意种类的岩石[2];卓越的抗磨损性,其抗磨损性可以与自然界中最坚硬的岩石相媲美[3];杰出的抗冻融循环性[4];非常低的徐变性[5]和较高的弯曲强度。本文将重点关注高性能混凝土运用其本身的卓越性能如高强度、硬度及延性而建造的复杂结构体系及超大型结构工程。同时在此文中还要展示运用高性能混凝土所带来的其它方面的益处。