掺粉煤灰塑性混凝土的配制技术研究

结合使用高效减水剂，塑性混凝土掺加适量粉煤灰，不仅可以使其具备良好的和易性与流动性，减少单位水泥用量，减轻温度控制负担，防止塑性混凝土防渗墙裂缝的发生，还能够增强塑性混凝土抵抗地下水溶盐的侵蚀作用。本文介绍了粉煤灰对塑性混凝土性能的影响，并且结合工程实例总结了掺粉煤灰塑性混凝土的配制技术及应用经验。     

粉煤灰和锰渣对混凝土0～24h收缩性能的影响

试验采用贵州特有的锰渣和粉煤灰为掺合料,探究其对混凝土0～24 h收缩性能的影响。试验表明:单掺情况下,粉煤灰掺量为30%,锰渣掺量为40%时,能有效抑制混凝土的塑性收缩;复掺粉煤灰、锰渣时,当粉煤灰掺量为二者总量的10%和14%时(掺和料占胶凝材料总量的20%),抑制作用最强;两种方法比较发现:无论是单掺还是复掺,对混凝土的塑性收缩都有一定的抑制作用,单掺锰渣的效果最好,复掺粉煤灰、锰渣次之,单掺粉煤灰最差。     

高掺量低品质粉煤灰混凝土碳化性能的试验研究

进行了掺加不同品质和掺量粉煤灰、复掺矿渣粉的粉煤灰混凝土的快速碳化试验研究。结果表明,低品质粉煤灰掺量越多,越不利于混凝土抗碳化性能;20%以下掺量时,混凝土碳化深度不会显著增加;48%掺量时,混凝土抗碳化性能明显降低;在混凝土中复掺矿渣粉可以大大改善粉煤灰混凝土的抗碳化性能。提出了复掺矿渣粉的高掺量低品质粉煤灰混凝土配合比设计方法,不仅对提高粉煤灰混凝土抗压强度有利,并且可大大改善其抗碳化性能。     

粉煤灰对混杂纤维混凝土力学与耐久性能的影响分析

将粉煤灰加入混凝土中可以有效消耗工业固体废弃物，保护环境。基于此，制备了不同粉煤灰掺量的混杂纤维混凝土样品，开展了立方体抗压强度、劈裂抗拉强度、碳化深度以及冻融循环后的相对动弹性模量和质量损失率测试，分析了混凝土力学与耐久性能随粉煤灰掺量的变化规律。研究结果表明：养护龄期小于14 d时混杂纤维混凝土的抗压强度随粉煤灰掺量的增大而减小，养护龄期大于14 d时抗压强度随粉煤灰掺量的增大而增大；60 d养护龄期和12%粉煤灰掺量的混凝土抗拉强度最大；碳化深度随粉煤灰掺量的增大而先减小后增大；粉煤灰掺量小于12%时，掺入粉煤灰的混杂纤维混凝土的抗冻性能要略优于素混杂纤维混凝土。     

大掺量粉煤灰对高架桥混凝土路面断裂性能影响试验研究

大掺量粉煤灰与混凝土水泥反应产生的凝胶可以改善混凝土粘接性能。为了确定粉煤灰掺量范围，将断裂度作为衡量混凝土断裂性能重要参数，根据混凝土在不稳定状态下的脆性断裂特征，对混凝土路面进行了断裂程度及应力分析，按照大掺量粉煤灰的混凝土界面粘接强度，分析拔出型、断裂型在显微镜下的断裂细微形态。结果表明，粉煤灰掺量为20%时，混凝土路面断裂正应力大于0.8 GPa,剪切应力大于1.5 GPa,混凝土路面抗压强度较大，混凝土路面抗断裂性能最好。随着粉煤灰掺量增加，混凝土路面抗断裂性能逐渐变差。     

引气粉煤灰混凝土抗冻融耐久性的研究

本文就粉煤灰不同掺量及与硅灰复掺对混凝土抗冻性能的影响进行了研究。通过试验论证了在固定新拌混凝土含气量的情况下。粉煤灰20％的掺量对粉煤灰抗冻性能的影响很小，粉煤灰与硅灰复掺对混凝土的抗冻性能不利。与基准组相比。随着掺合料掺量的增加，混凝土抗氧离子渗透系数降低，混凝土抗冻性能下降。     

粉煤灰掺量和细度对高强砼塑性开裂的影响

研究了粉煤灰掺量与细度对高强混凝土塑性开裂趋势的影响。试验结果表明:对于低水胶比的高强混凝土来说,随着粉煤灰掺量增大,其塑性收缩裂缝呈减少趋势;粉煤灰细度增大,塑性开裂并无增大趋势,反而有减小的作用。最后探讨了塑性开裂的机理。     

不同粉煤灰掺量混凝土的早期抗压与抗渗性能

试验研究了不同粉煤灰掺量混凝土的早期抗压强度和抗渗性能,结果表明,不同粉煤灰掺量的混凝土,其早期强度随粉煤灰掺量的增加降低越显著,28d时粉煤灰的掺量对混凝土强度的影响作用逐渐减弱;不同粉煤灰掺量混凝土的早期抗渗性能随粉煤灰掺量的增加降低也越明显,7d以后粉煤灰对混凝土抗渗性能的改善随粉煤灰掺量的增加而增强。     

I级粉煤灰混凝土的抗冻融性能

以往的概念是掺Ⅱ级粉煤灰后，随掺量的增大，会大幅度降低混凝土的抗冻融性能，但I级粉煤灰对混凝土的抗冻融性能将如何影响呢?我们比较了I级和Ⅱ级粉煤灰对混凝土抗冻性的影响，并分析了两者差异的原因。试验结果表明：在粉煤灰掺量相同时。混凝土达到相同引气量所用的引气剂掺量，Ⅱ级粉煤灰是I级的2～3倍。无论是I级或Ⅱ级粉煤灰，较低的水灰比和合适的含气量，是保证粉煤灰混凝土具有较高抗冻性能的决定性因素。相同条件下，I级粉煤灰混凝土的抗冻性能优于Ⅱ级粉煤灰混凝土的抗冻性能。     

高流动性大掺量粉煤灰混凝土耐久性试验研究

试验研究了早强剂掺量、水胶比和粉煤灰掺量对高流动性大掺量粉煤灰混凝土耐久性的影响。正交试验结果表明,高流动性大掺量粉煤灰混凝土抗渗性的最主要影响因素为粉煤灰掺量,其次为水胶比及早强剂;高流动性大掺量粉煤灰混凝土抗碳化性能和抗冻性能的最主要影响因素为粉煤灰掺量,其次为早强剂掺量及水胶比。通过正交设计可以得出满足混凝土耐久性的配合比设计方法。     

混凝土中粉煤灰工程效应的估算和分析

粉煤灰对混凝土工作性、强度发展和耐久性的影响,即取决于粉煤灰的材料品质,又取决于混凝土的组成结构。等工作性下,粉煤灰混凝土与基准混凝土的需水量比、28d强度比以及某项耐久性指标比值可以表征或定义混凝土中粉煤灰的一系列工程效应,即塑化效应、固化效应和免疫效应。本文就混凝土系统,提出了估算粉煤灰塑化效应和固化效应的方法,并运用粉煤灰工程效应的观点,初步探讨了双掺法中粉煤灰工程效应之间的相互关系。     

粉煤灰混凝土的势能化

根据势能的观点和混凝土工程性质的要求，给出混凝土中粉煤灰经化势，固化势和免疫势的定义，以及粉煤灰砂浆体或粉煤灰混凝土材料的协同工作特性的数学表达；通过图解的方法，对粉煤灰材料的质量等级以及粉煤灰混凝土双掺技术的应用进行了势能化的初步探讨。     

Utilising unprocessed low-lime coal fly ash in foamed concrete

This paper describes an extensive laboratory-based investigation into the use of unprocessed, run-of-station, low-lime fly ash in foamed concrete, as a replacement for sand. Foamed concrete with plastic densities ranging between 1000 and 1400 kg/m³ and cube strengths from 1 to 10 N/mm² were tested. It is shown that by using this type of fly ash in this way can significantly enhance many of the properties of foamed concrete, including rheology and compressive strength development, whilst providing almost complete immunity to sulfate attack. Given the high carbon content of this type of fly ash, however, it was found that there was a need to increase greatly the amount of foam required to achieve the specified design plastic density. However, given the relatively low cost of foam production, this is not likely to have significant implications for the use of material.     

Rheology of ordinary and low-impact environmental concretes

This study deals with the rheological properties of concrete mixtures incorporating various types of mineral additions as a partial replacement of cement in order to produce a low-impact environmental concrete. The control mixture contained only Portland cement as the binder, while the remaining mixtures incorporated binary cementitious blends of slag, limestone filler, and fly ash with different rates of replacement. After mixing, the plastic viscosity and yield stress of the concretes were evaluated at different slump values using a rheometer apparatus. The results showed that the type of mineral additions and the rate of substitution affect the rheological parameters of low-impact environmental concrete. Indeed, increasing the degree of substitution leads to an increase in the plastic viscosity of the concrete made with different types of additions used in this study.     

Properties of lightweight expanded polystyrene aggregate concretes containing fly ash

Lightweight concretes can be produced by replacing the normal aggregates in concrete or mortar either partially or fully, depending upon the requirements of density and strength levels. The present study covers the use of expanded polystyrene (EPS) beads as lightweight aggregate, both in concrete and mortar. The main aim of this programme is to study the mechanical properties of EPS concretes containing fly ash and compare the results with these in literature on concretes containing OPC alone as the binder. The effects of EPS aggregate on the green and hardened state characteristics of concretes containing fly ash were evaluated. The compressive strength of the EPS concretes containing fly ash show a continuous gain even up to 90 days, unlike that reported for OPC in literature. It was also found that the failure of these concretes both in compression and split tension was gradual as was observed earlier for the concretes containing plastic shredded aggregates. The stress-strain relations and the corresponding elastic modulus were also investigated.     

粉煤灰综合利用现状

随着煤炭资源利用量的增加,粉煤灰排放量呈现逐年增加趋势,根据灰色预测模型估计到2020年中国粉煤灰排放量将达到9亿t。如何利用好粉煤灰,减少环境污染,减少占地面积,增加工业产值等是普遍关注的问题。在对粉煤灰物理化学特性概述的基础上,对粉煤灰的综合利用进行了归类,并从农业（土壤改良、肥料）,建材（混凝土、砖块、水泥、砂浆、陶粒、泡沫玻璃、拒水粉等）,化学工业（提取铝元素、合成分子筛、橡塑复合材料、造纸）,环保（污水处理、烟气净化）等方面进行分类阐述,对粉煤灰的利用方向提出了建议。     

The effect of measuring procedure on the apparent rheological properties of self-compacting concrete

Torque versus time during testing of the rheological properties of fresh concrete has been investigated. The testing was performed in a BML viscometer and on a self-compacting concrete (w/c=0.45, 70% rapid hardening Portland cement, 3% silica fume, 27% fly ash, third generation superplasticizer). The relaxation period needed to obtain steady-state flow may affect the rheological properties estimated and should be taken into account in the selection of measuring procedures. Nonsteady state is likely to cause an overestimation of the plastic viscosity and an underestimation of the yield value. Furthermore, lack of steady state may explain the apparent shear-thickening behaviour of self-compacting concrete reported elsewhere.     

大掺量粉煤灰混凝土在污水池工程中的应用

通过大掺量粉煤友混凝土在污水池工程中的应用证明：粉煤灰的掺入可以改善混凝土的界面结构，提高混凝土的强度;大掺量粉煤灰混凝土特别适合大体积混凝土工程。大掺量粉煤灰混凝土的应用具有良好的经济效益和社会效益。     

基于粉煤灰掺量的砂浆塑性收缩开裂本构关系的研究

研究了粉煤灰掺量对于砂浆塑性收缩性能和塑性粘度的影响。试验表明,随着粉煤灰掺量的增加,砂浆抗裂指数增大,开裂所需时间增加,塑性粘度降低;建立了粉煤灰掺量与砂浆抗裂指数、开裂时间的本构关系,及掺加粉煤灰后砂浆塑性粘度与抗裂指数的本构关系。