Influence of dry and wet curing conditions on compressive strength of silica fume concrete

This paper reports a part of an ongoing laboratory investigation in which the compressive strength of silica fume concrete is studied under dry and wet curing conditions. In the study, a total of 48 concretes, including control Portland cement concrete and silica fume concrete, were produced with four different water–cement ratios (0.3, 0.4, 0.5, 0.6), three different cement dosages (350, 400, 450 kg/m³) and three partial silica fume replacement ratios (10%, 15%, 20%). A hyperplastisizer was used in concrete at various quantities to provide and keep a constant workability. Three cubic samples produced from fresh concrete were demoulded after a day; then, they were cured at 20±2 °C with 65% relative humidity (RH), and three other cubic samples were cured at 20±2 °C with 100% RH until the samples were used for compressive strength measurement at 28 days. The comparison was made on the basis of compressive strength between silica fume concrete and control Portland cement concrete. Silica fume concretes were also compared among themselves. The comparisons showed that compressive strength of silica fume concrete cured at 65% RH was influenced more than that of Portland cement concrete. It was found that the compressive strength of silica fume concrete cured at 65% RH was, at average, 13% lower than that of silica fume concrete cured at 100% RH. The increase in the water–cementitious material ratios makes the concrete more sensitive to dry curing conditions. The influence of dry curing conditions on silica fume concrete was marked as the replacement ratio of silica fume increased.     

关于使用硅粉混凝土进行桥面铺装的探讨

叙述了在混凝土中掺加硅粉,结合应用高效复合减水剂,不仅能减少单位水泥用量,而且可赋予混凝土较高的抗渗性能,掺加硅粉还可使混凝土强度对生产过程中变异因素敏感性降低,强度波动范围受到有效控制,结合工地实际情况,探讨了在桥面铺装混凝土中添加硅粉的可行性,并通过具体实验数据证明其合理性。     

硅粉粉煤灰混凝土的室内试验研究

结合具体的工程实例,通过试验对硅粉混凝土和硅粉粉煤灰混凝土的制备进行了研究,并对二者的经济性作了分析比较,得出硅粉粉煤灰混凝土较硅粉混凝土的坍落度高,且工程经济性与适用性强的结论。     

偏高岭土矿物掺和料应用性能研究

高岭土在适当的温度下煅烧 ,得到新型高活性混凝土偏高岭土 (KP)矿物掺和料 ,本文详细介绍了KP掺和料在新拌混凝土中的工作性能和硬化混凝土的增强性能 ,同时与硅灰做了对比。试验结果表明 ,偏高岭土是一种良好的矿物掺和料 ,各种性能与硅灰相近 ,完全可以替代硅灰在高性能混凝土中应用     

关于硅灰和高性能混凝土的一些思考

硅灰的商业化应用在美国已有25年的历史。在此期间,硅灰从一种处于研究阶段的材料演变成一种在混凝土中被广泛规定使用的组分。硅粉在被市场所接纳的时间,恰好是“高性能混凝土”一词产生的前夕,有充分的理由说明：最初的硅灰混凝土项目正是高性能混凝土的起源。本文简述了在美国市场中硅灰使用的发展历史;回顾了硅灰混凝土如何发展成为高性能混凝土;并总结了使用硅灰的适用场合、配合比、抹面和施工性能等方面的经验。     

硅灰、偏高岭土对无机人造石材强度的影响

硅灰和偏高岭土作为无机粘结材料掺入无机人造石中,不仅能替代部分水泥,还能改善无机人造石的强度。本文研究了不同掺量硅灰和偏高岭土对人造石材工作性能和力学性能的影响趋势。结果表明,利用偏高岭土和硅灰制备无机人造石会降低其工作性能,且偏高岭土对混合料工作性能的影响较硅灰略大;随着掺量的增加,强度呈先增大后降低趋势,在掺量为3%时,弯曲强度和压缩强度达到最大。同时,偏高岭土和硅灰对人造石的压缩强度影响显著,其中偏高岭土对人造石早期压缩强度影响更显著,其在对早期强度要求较高的工程中有一定的优势。     

凝聚态硅灰对低工作性混凝土强度发展历程的影响

在不同的水胶比条件下,考察了凝聚态硅灰对低工作性混凝土强度发展历程的影响.试验结果表明:在研究的水胶比范围内,凝聚态硅灰对低工作性混凝土强度的贡献主要是在后期,且随着水胶比的降低,其增强能力的发挥进一步推迟.     

钢渣粉硅灰混凝土的力学性能及耐久性研究

通过试验测试分析了钢渣粉单掺以及与硅灰二元复掺混凝土在不同配合比下的和易性、力学性能和耐久性能,并基于改性前后混凝土微观结构特征的测试分析揭示了钢渣粉单掺以及与硅灰二元复掺对混凝土材料的改性机理。试验研究结果表明:钢渣粉取代混凝土中水泥最适宜的比例是10%,此时混凝土的力学性能和耐久性能都得到有效的提高,掺量20%的钢渣混凝土与普通硅酸盐混凝土各项性能相近。钢渣粉与硅灰的二元复掺可以使混凝土的力学性能和耐久性得到显著提高。钢渣粉在混凝土中的作用有两个:一是作为活性胶凝材料发生水化反应,但其活性比水泥低;二是微集料效应,分散水泥颗粒填充混凝土的孔隙,提高混凝土的密实度。     

硅灰对高强混凝土强度影响的试验研究

在高强混凝土中掺入适量的硅灰,对提高混凝土的劈裂抗拉强度有非常明显的效果,也可在一定程度上增强混凝土的抗压强度和抗折强度.掺量低于或高于适量范围,对提高混凝土的强度作用很小.在实际工程混凝土中合理掺用硅灰,不仅可以提高混凝土的强度,而且变废为宝,改善环境,技术、经济和社会效益显著.     

硅粉在混凝土中的应用探讨

作者分析了硅粉在混凝土中的作用机理，以及硅粉对混凝土物理、力学性能的影响，从而指出在混凝土中掺入适量的硅粉，是一种所需投资较少且有明显效果的方法，并可带来良好的环境效益和社会效益。     

无硅灰C80高性能混凝土研究

本文在混凝土理论配合比的基础上，仅改变各掺合料的比例及总掺合料与水泥的比例关系，采用混凝土用中砂配制砂浆，探索了一条以砂浆流动性指导高强高性能混凝土配制的新方法，并应用该方法以290kg/m^3，42．5R普通硅酸盐水泥及粉煤灰、矿渣粉和沸石粉等矿物掺合料配制出28d强度为96MPa的无硅高性能混凝土。     

高强混凝土的断裂性能研究

由于混凝土强度越高,脆性越大,限制了混凝土材料的发展及应用,通过试验测量了采用不同掺合物配制的混凝土的断裂韧性、裂纹临界扩展载荷、临界裂纹尖端张开位移和混凝土特征长度,并进行对比分析了各高强混凝土的断裂性能,提出掺加适量的粉煤灰可以增强高强混凝土的韧性,同时也不会显著影响高强混凝土的强度.     

Optimization of early flexural strength of pavement concrete with silica fume and fly ash by the Taguchi method

In this study, an attempt has been made to optimize the early flexural strength of concrete pavement (CP) by using the Taguchi Method. The experiments were designed using an orthogonal array technique in L₁₆ array with four factors, namely, the water/cementitious ratio of 0.30, 0.35, 0.40 and 0.45, four different types of gradations with maximum aggregate size of 32?mm, fly ash (FA) 0%, 5%, 10%, 15% and silica fume (SF) 0%, 10%, 20% and 30% by weight of cement. The response data were analyzed using an analysis of variance (ANOVA) technique by the Taguchi method. According to the ANOVA table, water/cementitious ratio and SF content play significant roles for early flexural strength of CP. Moreover, the optimum conditions were found to be 0.35 water/cementitious ratio, gradation with minimum content of fine aggregates, 5% FA content and 0% SF content at 7 days curing. Maximum flexural strength of 5.31?MPa was achieved at the optimum conditions.     

混凝土孔结构的分类命名与高性能混凝土的孔结构种类

论述了混凝土孔结构的分类与命名方法;指出高性能混凝土的孔结构应该具有中密实、超密实和引气型三类,其中大规模使用的高性能混凝土孔结构应该是引气型的。     

高性能轻集料混凝土的强度及耐久性的研究

采用页岩陶粒，掺入硅灰和高效减水剂配制而成高性能轻集料混凝土。并研究了水泥用量、水灰比、硅灰掺量对强度的影响及其抗冻和抗渗性能。     

掺硅粉混凝土路用性能研究

分析了硅粉对混凝土作用机理，研究了掺硅粉路面混凝土的路用性能和施工工艺及技术经济性。结果表明，从抗折强度和经济性指标考虑，路面混凝土存在最佳硅粉掺量问题；与不掺硅粉路面混凝土相比，路面混凝土中按最佳掺量15～20kg／m^3掺入硅粉，能显著提高路面混凝土的路用性能和降低工程造价，如抗折强度提高10％、极限拉应变提高22％以上、压折比降低7％、耐磨性提高42％和抗冻性能提高近十倍、材料费用可节约11％左右，表明掺硅粉混凝土在路面工程中应用是可行的。     

硅灰和石英粉对活性粉末混凝土抗压强度贡献的分析

运用火山灰效应数值分析方法定量分析了硅灰和石英粉两种主要组分对RPC抗压强度贡献率、强度贡献数值以及两种组分的强度贡献指数。     

Effect of silica fume and steel fibers on some properties of high-strength concrete

The main disadvantage of high-strength concrete is its highly brittle behavior and this can beovercome by adding fibers to the concrete. This would also improve some other mechanical properties of high-strength concrete such as tensile strength and compressive strength. These properties are not very well established for high-strength steel-fiber reinforced concrete (HSFRC) yet. In this study the influence of silica fume on the properties of HSFRC were investigated by using silica fume of two different percentages and three different hooked-end fibers namely, 30/0.50, 60/0.80 and 50/0.60 length/diameter (mm/mm). Fibers were added to concrete in three different volume percentages of 0.5, 1.0 and 2.0 by volume of concrete. The results indicated that there is a linear function between splitting tensile strength (F_splt) and volume percentage of fibers (V_f) [i.e. F_plt = A(V_f) + B, where A and B are correlation coefficients] as well as between splitting tensile strength (F_splt) and compressive strength (F_c) of plain series A concrete [i.e. F_splt = C (√F_c) + D, where C and D are correlation coefficients]. These relations can describe the development of splitting tensile strength of HSFRC containing no silica fume, 5% silica fume and 10% silica fume by weight of cement. On the other hand, although silica fume has an effect on compressive strength, volume percentage and aspect ratio of steel fibers has little effect.     

Concretes with aggregates from demolition waste and silica fume. Materials and mechanical properties

The purpose of this paper is to provide new data related to the field of recycled concrete in Spain. In keeping with this, several procedures were established, on the basis of which conclusions have been drawn regarding the suitability or non-suitability of recycled aggregates in Spain. Standard tests were carried out to determine the density, water absorption, grading, shape index, flakiness index and fragmentation resistance.     

复掺粉煤灰和硅灰在自密实混凝土中的应用

复掺粉煤灰和硅灰应用到自密实混凝土中,可以增大新拌混凝土的流动性,改善离析泌水,增加混凝土硬化后的强度,提高其耐久性能。试验研究了粉煤灰的最佳掺量,以及几种矿物质掺合料复掺的复合效应。