一种低熟料矿渣硅酸盐水泥的早强促凝研究

针对低熟料矿渣硅酸盐水泥早期强度低、凝结时间长的问题,研究了外掺外加剂和复合方案对低熟料矿渣硅酸盐水泥凝结时间和抗压强度的影响,并通过Jade软件计算31.5°~32.5°水泥矿物C3S对应的XRD图谱积分面积,用以探讨其促凝早强机理。结果表明:外掺方案中,4%熟石灰外掺时可以提高早期强度和缩短凝结时间,0.03%三乙醇胺可以提高早期强度,0.6%A(早强剂)和0.4%C(促凝剂)复合时其早强促凝效果最为明显。复合方案中,3%半水石膏取代硬石膏时可以缩短凝结时间,但会引起强度降低,在此基础上外掺4%熟石灰可以弥补强度损失,但是早期强度增幅不大。细磨熟料和矿渣粉、3%半水石膏取代硬石膏、外掺4%熟石灰复合时可以较大幅度缩短凝结时间,3d抗压强度提高幅度在17%左右。     

用煤矸石配制速凝早强水泥

选用合适的煤矸石、硅、铝质原料与矿化剂等原材料,采用高铝高饱和比加复合矿化剂的配料方案及其合理的生产工艺,可配制出速凝早强水泥,达到双快—１５０特性水泥的技术性能指标。     

C-S-H凝胶产物的Ca/Si比对碱-骨料反应的影响

采用混凝土加速实验,对添加不同混合材试样的膨胀率和试样中生成的C-S-H凝胶产物进行了研究,测定了不同混合材对试样膨胀率的影响以及所生成的C-S-H凝胶的化学组成,进一步验证C-S-H凝胶的Ca/S i比对碱骨料反应(AAR)的影响。     

超早强高强胶凝材料的研究

在现有混凝土胶凝体系的基础上,选择硫铝酸盐水泥、硅酸盐水泥、复合矿物外加剂作为胶凝材料体系的主要组成部分,配以合适的外加剂,实现了胶凝材料早强、高强的性能。     

石膏品种和掺量对水泥促凝增强作用的影响

试验结果表明,石膏品种和掺量的改变对水泥的促凝增强作用产生较大影响。石膏掺量相同时,其效果依次为盐石膏≥磷石膏≥二水石膏≥硬石膏。石膏品种相同时,对水泥的促凝增强效果随石膏掺量的增大而提高,但掺量增至一定范围后,使用盐石膏、磷石膏、二水石膏的增强效果增幅呈下降趋势,而使用硬石膏则呈上升势头,并提出最佳石膏掺量。     

低Ca/Si比的C-S-H凝胶产物在抑制AAR中的作用

碱是混凝土发生碱-集料(AAR)反应的重要因素之一。许多资料报道低Ca/Si比的C-S-H凝胶对碱有强烈的吸附作用。从C-S-H凝胶的组成出发,指出低Ca/Si比的C-S-H凝胶在抑制AAR中的作用,解释了低Ca/Si的C-S-H凝胶对碱的吸附能力强的原因及其影响因素。为在实际工程应用中掺加混合材来抑制AAR反应,提高混凝土耐久性有重大指导意义。     

微集料对超速凝超早强水泥凝结硬化的作用

本实验研制的超速凝结早强水泥中的微集料掺加量高达１３％。实验表明，在该掺量下微集料有助于凝结时间的缩短，但使强度略有降低，本文讨论了其作用。微集料的细度是影响水泥性能的关键。     

用矿渣微粉配制高掺量早强矿渣水泥的研究

通过正交试验研究不同细度、掺量的矿渣微粉和熟料对渣水泥性能的影响。试验发现,影响矿渣水泥3d、28d强度的主次因素不同,3d强度主要受矿渣细度的影响,28d强度则主要受矿渣掺量影响。采用分别粉磨后混合的生产工艺,用一定细度的矿渣微粉可以生产出掺量较高、早强性能好的矿渣水泥。     

煤层气低温早强低密度水泥浆体系研究

利用水泥干混物堆积体积百分比最大化原理,选用以人工漂珠颗粒、G级水泥颗粒、粉煤灰颗粒以及矿渣颗粒构成4级颗粒填充结构体系,开发了一种适用于煤气层固井密度为1.40 g/cm3的低温早强低密度膨胀水泥浆体系,对材料的来源进行了优选,对外加剂的作用机理进行了分析.室内实验结果表明,该体系有良好的沉降稳定性,自由液为0,且流变性能良好,滤失量小于50 mL,稠化时间根据实际需要在120～ 300 min内可调,基本成直角稠化,中低温条件下水泥石24h早期抗压强度高于14 MPa,在90℃时的24h强度高达22.7 MPa,各项性能均满足作业要求.     

磷渣水泥专用助磨剂的应用研究

为了克服磷渣水泥凝结时间延长和早期强度降低的性能缺陷,本试验考察了在磷渣水泥中添加HY-CN-B助磨剂后水泥的各项物理和力学性能。结果表明,HY-CN-B助磨剂对磷渣水泥具有良好促凝增强效果。掺量为0.4%时,促凝增强效果最佳,初、终凝时间分别缩短30、90min,3d及28d抗压强度分别提高4.8MPa和7.9MPa。实际工业应用中可在保持水泥强度不变的情况下,有效提高磷渣掺量10%,降低熟料用量10%,提高磨机台时产量10%～15%,同时可使吨水泥生产成本降低10～15元,具有显著的经济效益和环保效益。     

水泥水化物晶胶比对水泥抗折性能的影响

通过在水泥中引入晶体源调整水化物晶胶比以提高水泥的抗折性能,测试了引入不同晶体源的水泥胶砂强度及脆性系数,确定用CA调整水泥石的晶胶比较为适宜。测定了不同CA掺量时水泥砂浆膨胀率及强度,对试验结果进行了分析,得出了CA的最佳掺量。     

The C-S-H gel of Portland cement mortars: Part I. The interpretation of energy-dispersive X-ray microanalyses from scanning electron microscopy, with some observations on C-S-H, AFm and AFt phase compositions

Scanning electron microscopy (SEM) microanalyses of the calcium-silicate-hydrate (C-S-H) gel in Portland cement pastes rarely represent single phases. Essential experimental requirements are summarised and new procedures for interpreting the data are described. These include, notably, plots of Si/Ca against other atom ratios, 3D plots to allow three such ratios to be correlated and solution of linear simultaneous equations to test and quantify hypotheses regarding the phases contributing to individual microanalyses. Application of these methods to the C-S-H gel of a 1-day-old mortar identified a phase with Al/Ca=0.67 and S/Ca=0.33, which we consider to be a highly substituted ettringite of probable composition C₆A₂S?₂H₃₄ or {Ca₆[Al(OH)₆]₂·24H₂O}(SO₄)₂[Al(OH)₄]₂. If this is true for Portland cements in general, it might explain observed discrepancies between observed and calculated aluminate concentrations in the pore solution. The C-S-H gel of a similar mortar aged 600 days contained unsubstituted ettringite and an AFm phase with S/Ca=0.125.     

Composition, morphology and nanostructure of C-S-H in white Portland cement pastes hydrated at 55 °C

The C-S-H present in water- and alkali-activated hardened pastes of white Portland cement hydrated at 55 °C has been characterized. The mean length of the aluminosilicate anions in the C-S-H was similar in both systems and increased with age. Inner product C-S-H generally had a fine scale, homogeneous morphology. Outer product C-S-H was generally fibrillar with water, and foil- or lath-like with alkali. There were some regions of C-S-H with coarse morphology. It was not possible to determine the chemical composition of C-S-H using the SEM; TEM-EDX was necessary. The C-S-H formed in the alkali-activated paste had a lower mean Ca/(Al + Si) ratio than that formed with water, which was offset by a larger quantity of calcium hydroxide. The potassium in the KOH-activated paste was present either within the C-S-H structure charge balancing the substitution of Al³⁺ for Si⁴⁺, or adsorbed on the C-S-H charge balancing sulfate ions.     

氧化钙对氯氧镁水泥低温凝结性能的影响

为了深入研究氯氧镁水泥低温凝结机理,进而改善和提高氯氧镁水泥在低温时的快硬性能,把氧化钙加入到氯氧镁水泥料浆中,通过搅拌、成型、恒温恒湿箱养护后测定其凝结时间及早期强度。结果表明：氧化钙加入后放出热量,引发氯氧镁水泥水化起始期反应的进行,有效缩短氯氧镁水泥的凝结时间。当氧化钙掺量为氧化镁质量的4%时,氧化镁活性为62.24%和72.01%时初凝时间分别由593 min缩短到146 min、由570 min缩短到126 min,终凝时间分别由673 min缩短到374 min、由641 min缩短到260 min,同时都提高了氯氧镁水泥的低温早期强度。     

Tobermorite/jennite- and tobermorite/calcium hydroxide-based models for the structure of C-S-H: applicability to hardened pastes of tricalcium silicate, β-dicalcium silicate, Portland cement, and blends of Portland cement with blast-furnace slag, metakaolin, or silica fume

The purpose of this article is to discuss the applicability of the tobermorite-jennite (T/J) and tobermorite-‘solid-solution’ calcium hydroxide (T/CH) viewpoints for the nanostructure of C-S-H present in real cement pastes. The discussion is facilitated by a consideration of the author's 1992 model, which includes formulations for both structural viewpoints; its relationship to other recent models is outlined. The structural details of the model are clearly illustrated with a number of schematic diagrams. Experimental observations on the nature of C-S-H present in a diverse range of cementitious systems are considered. In some systems, the data can only be accounted for on the T/CH structural viewpoint, whilst in others, both the T/CH and T/J viewpoints could apply. New data from transmission electron microscopy (TEM) are presented. The ‘inner product’ (Ip) C-S-H in relatively large grains of C₃S or alite appears to consist of small globular particles, which are ≈4-8 nm in size in pastes hydrated at 20 °C but smaller at elevated temperatures, ≈3-4 nm. Fibrils of ‘outer product’ (Op) C-S-H in C₃S or β-C₂S pastes appear to consist of aggregations of long thin particles that are about 3 nm in their smallest dimension and of variable length, ranging from a few nanometers to many tens of nanometers. The small size of these particles of C-S-H is likely to result in significant edge effects, which would seem to offer a reasonable explanation for the persistence of Q⁰(H) species. This would also explain why there is more Q⁰(H) at elevated temperatures, where the particles seem to be smaller, and apparently less in KOH-activated pastes, where the C-S-H has foil-like morphology. In blended cements, a reduction in the mean Ca/Si ratio of the C-S-H results in a change from fibrillar to a crumpled-foil morphology, which suggests strongly that as the Ca/Si ratio is reduced, a transition occurs from essentially one-dimensional growth of the C-S-H particles to two-dimensional; i.e., long thin particles to foils. Foil-like morphology is associated with T-based structure. The C-S-H present in small fully hydrated alite grains, which has high Ca/Si ratio, contains a less dense product with substantial porosity; its morphology is quite similar to the fine foil-like Op C-S-H that forms in water-activated neat slag pastes, which has a low Ca/Si ratio. It is thus plausible that the C-S-H in small alite grains is essentially T-based (and largely dimeric). Since entirely T-based C-S-H is likely to have different properties to C-S-H consisting largely of J-based structure, it is possible that the C-S-H in small fully reacted grains will have different properties to the C-S-H formed elsewhere in a paste; this could have important implications.     

磷渣细度和掺量对中热硅酸盐水泥物理性能的影响

研究了磷渣细度及掺量对中热硅酸盐水泥性能的影响。研究表明,随磷渣掺量增加,磷渣水泥的凝结时间明显延长;随磷渣细度增加,磷渣水泥的凝结时间先增大后减小;磷渣的掺入未给水泥安定性带来不良影响。在没有添加激发剂的情况下,要使磷渣水泥在施工性能和力学性能方面同时满足工程应用的需要,则有必要降低磷渣掺量至20％左右或更低。随磷渣细度的增加,磷渣水泥7d、14d后干缩率呈V形变化的趋势,且在14d后干缩基本恒定。通过XRD、SEM分析及对磷渣粉磨特性的分析研究了磷渣中热硅酸盐水泥的缓凝机理及强度变化规律。     

粉煤灰矿渣复合水泥强度协同效应的研究

研究了由粉煤灰、矿渣、钢渣与一定量熟料组成的粉煤灰矿渣复合水泥中各组分对水泥的强度协同效应以及影响协同效应的主要因素。并利用SEM和MIP等技术研究了粉煤灰矿渣复合水泥的水化硬化过程、水化产物相组成及硬化浆体结构,以此来论证各组分间协同效应的作用机理。研究结果表明:当各组分比例适当时,通过石膏和添加剂的有效作用,采取合理的粉磨工艺和制度,粉煤灰矿渣复合水泥各组分可以产生强度协同效应。     

纳米水化硅酸钙的制备及对水泥水化影响的研究进展

随着纳米技术的不断发展,纳米材料逐步开始应用于传统混凝土材料中,以提高混凝土的各项服役性能。纳米水化硅酸钙(纳米C-S-H)是一种新型的早强纳米复合材料,可通过晶核效应加快水泥早期水化速率,显著提高水泥基材料的早期力学性能,从而提高施工效率,满足特殊施工要求。本文系统总结了纳米C-S-H的制备方法,及纳米C-S-H对水泥基材料早期和长期性能的影响规律,探讨了其对于水泥水化过程和水化产物的影响机制,其中重点介绍了采用聚合物分散纳米颗粒制备的C-S-H/PCE(聚羧酸型减水剂,简称PCE)纳米复合材料。     

Effect of hydration temperature on the solubility behavior of Ca-, S-, Al-, and Si-bearing solid phases in Portland cement pastes

The concentrations of Ca, S, Al, Si, Na, and K in the pore solutions of ordinary Portland cement and white Portland cement pastes were measured during the first 28 d of curing at temperatures ranging from 5–50 °C. Saturation indices with respect to solid phases known to form in cement paste were calculated from a thermodynamic analysis of the elemental concentrations. Calculated saturation levels in the two types of paste were similar. The solubility behavior of Portlandite and gypsum at all curing temperatures was in agreement with previously reported behavior near room temperature. Saturation levels of both ettringite and monosulfate decreased with increasing curing temperature. The saturation level of ettringite was greater than that of monosulfate at lower curing temperatures, but at higher temperatures there was effectively no difference. The solubility behavior of C-S-H gel was investigated by applying an appropriate ion activity product (IAP) to the data. The IAP_CSH decreased gradually with hydration time, and at a given hydration time the IAP_CSH was lower at higher curing temperatures.