沸石炭火山灰活性的研究

用化学的，物理的和物化的方法证明，沸石凝灰岩中的沸石是热力学稳定的物质，硅酸盐水泥中碱度在常温下不足以破坏沸石的结构。沸石凝灰岩的火山灰活性来自凝灰岩中无定性的SiO2和Al2O3。含有结晶态沸石的凝灰岩之所以有比非晶态火山灰高的活性，是因为沸石特殊的结构所起的“水气交换”作用以及其晶体颗粒调节浆体中微结构的作用。沸石含量不同的沸石凝灰岩在水泥中的掺量以5％－20％为宜，合适的类型为钙型和钠型的斜发沸石凝灰岩或丝光沸石凝灰岩。     

利用天然沸石作水泥混合材的试验研究

一、前言天然沸石作为水泥混合材料,以往被划归在火山凝灰岩一类,称火山灰质混合材料。随着近代矿物学的研究和进展,发现沸石是火山凝灰岩在低温低压以及水(一般是碱性至中性水)的作用下蚀变脱玻而成的,其晶体十分细小,然而作为水泥混合材料却具有较高的水硬活性,是优质的水泥混合材料。国外使用火山凝灰岩作水泥混合材料已有多年历史,只是由于近年来检测技术和矿物学     

GB/T 12957-2005《用作水泥混合材料的工业废渣活性试验方法》标准介绍

0引言,用于水泥混合材料的工业废渣活性，对水泥及混凝土性能有很大影响，因而工业废渣活性评定试验方法对水泥的生产和使用至关重要。目前国际上评定用于水泥中的工业废渣活性尚无统一检测方法，当前英、法等国均采用国际标准ISO863：1990（E）《用于火山灰质水泥的火山灰活性试验方法》，而德国采用DIN51043—79《凝灰岩检验要求》，美国和日本则采用28d抗压强度活性指数评定工业废渣活性，且目前日本标准JISA6201：1999《用于混凝土中的粉煤灰》中水泥强度试验方法已改用国际标准ISO679：1989。     

用作混凝土掺合料的火山岩的组成与火山灰活性

采集江西火山岩区代表性硅质火山岩样品,用化学分析、岩相学和X射线衍射(XRD)方法研究其化学组成、矿物类型和结构构造,采取火山岩石粉水泥砂浆强度比测定其火山灰活性指数,通过统计方法讨论并揭示硅质火山岩主要性能与火山灰活性的关系。结果表明:火山岩样品(除个别外)28d火山灰活性指数≥65%,可作为水泥砂浆和混凝土用天然火山灰质材料;珍珠岩火山灰活性最高,这是其玻璃质比例甚高和富硅铝质高温型矿物所致;角砾状熔结凝灰岩含较多大砾状岩屑和低温型矿物致使火山灰活性较低。火山岩岩相学分析的基质含量与XRD分析的非晶态相含量在岩石性能及对火山灰活性影响方面一致。火山岩活性指数与非晶态含量、化学成分SiO2含量或化学成分SiO2+Al2O3含量的复相关性表现良好,可应用活性指数与这些岩石主要参数的拟合方程预测火山岩的火山灰活性指数,从而判断其是否具备用作混凝土掺合料的潜质。     

凝灰岩石粉掺量对活性粉末混凝土性能的影响

以0.14水胶比成型活性粉末混凝土(RPC)为基体,采用凝灰岩石粉取代部分胶凝材料制备RPC,研究凝灰岩石粉掺量对RPC抗压强度、抗折强度和微观结构的影响。结果表明：RPC的抗压强度、抗折强度随凝灰岩石粉掺量增加呈下降趋势。凝灰岩石粉在胶凝体系中发挥了一定的火山灰效应和填充效应,改善了RPC的微观结构;掺量为5%凝灰岩石粉掺制备的RPC能满足力学要求,28 d龄期的抗压强度为119 MPa,抗折强度为12.4 MPa,孔隙率最低,且界面区最密实;当凝灰岩石粉掺量超过5%后,对微观结构的改善效果有所下降,当凝灰岩石粉掺量超过20%时,已不利于RPC微观结构的改善。     

火山灰质材料取代矿渣制造碱矿渣水泥

用人工和天然火山灰质材料(如火山灰、粉煤灰和沸石)替代部分高炉矿渣制造碱矿渣水泥。研究了这些材料对碱矿渣水泥的强度、抗化学侵蚀性能以及抑制泛碱的作用。实验结果表明它们能降低碱矿渣水泥的强度,但对提高抗化学侵蚀性能以及抑制泛碱有明显效果。火山灰质材料的含量应限制在30%以内,适宜的碱激发剂用量为4～5%(按 Na_2O 计)。XRD 分析表明其主要水化产物为 CSH(B)。     

养护温度对凝灰岩基胶凝材料力学性能的影响机理

凝灰岩是经过火山喷出散落在地面,经过压结和水化胶结固化而形成的一种火山灰碎屑岩,具有一定的火山灰活性。本文研究养护温度对凝灰岩基胶凝材料力学性能的影响,并借助FTIR、TG、SEM和MIP等对凝灰岩基胶凝材料水化产物的微观结构进行分析。结果表明,提高养护温度对凝灰岩基胶凝材料的力学性能具有一定的增强作用,提高养护温度不仅能提高早期强度,还可以提高后期强度,凝灰岩基胶凝材料的最佳养护温度为50 ℃。提高养护温度后凝灰岩基胶凝材料中没有生成新的水化产物,AFt和C-S-H等水化产物含量增加,Ca(OH)₂的含量减少。提高养护温度有利于增加凝胶孔和过渡孔占比,细化孔径结构,降低孔隙率,提高基体结构的致密度。     

火山灰水泥助磨剂的研制

火山灰可以作为生产水泥用的一种混合材,但是由于其活性较低而决定了它在水泥中的掺量较少。为了更进一步提高火山石在水泥中的掺量、降低水泥中熟料的消耗,该公司研制出了一种高效火山灰A型、B型水泥助磨剂,并介绍了助磨剂的大磨试验情况。     

火山灰性试验方法—应用〈ISO/R863—1968〉的研究

检验水泥混合材的火山灰性,我国多采用20±3℃15次石灰吸收法。该法以混合材吸收石灰量的多少(毫克/克试样)来表示活性的大小,实际上不能完全反映出材料加入水泥中的性能。因为火山灰性的评价,对确定火山灰质量起重要作用。1977年我院制定用于水泥和混凝土中的粉煤灰标准时,曾采用过国际标准化组织推荐的测定火山灰水泥火山灰性的方法ISO/R863-1968(简称 ISO 法),效果较好。     

不同助磨剂对粉煤灰火山灰活性影响的研究

探讨不同助磨剂对粉煤灰不同时期火山灰活性的影响。结果表明:单掺适量的不同助磨剂可以不同程度地提高粉煤灰早期、中期与后期的火山灰活性,其中早期的激发作用效果最大,后期的激发作用效果最小。且随着粉磨时间的延长,各水泥试样的3d、7d及28d抗压强度比值均有明显的提高但增幅下降。其中,当三乙醇胺掺量为0.03%时其对粉煤灰早期火山灰活性的激发作用效果最大;当乙二醇掺量为0.06%时其对粉煤灰中期火山灰活性的激发作用效果最大;当丙三醇掺量为0.09%时其对粉煤灰后期火山灰活性的激发作用效果最大。     

Effect of large amounts of natural pozzolan addition on properties of blended cements

In this study, the effects of 35, 45, and 55 wt.% natural pozzolan addition on the properties of blended cement pastes and mortars were investigated. Blended cements with 450 m²/kg Blaine fineness were produced from a Turkish volcanic tuff in a laboratory mill by intergrinding portland cement clinker, natural pozzolan, and gypsum. The cements were tested for particle size distribution, setting time, heat of hydration, compressive strength, alkali-silica activity, and sulfate resistance. Cement pastes were tested by TGA for Ca(OH)₂ content and by XRD for the crystalline hydration products. The compressive strength of the mortars made with blended cements containing large amounts of natural pozzolan was lower than that of the portland cement at all tested ages up to 91 days. Blended cements containing large amounts of pozzolan exhibited much less expansion with respect to portland cement in accelerated alkali-silica test and in a 36-week sulfate immersion test.     

石灰石硅酸盐水泥的研究

研究了石灰石硅酸盐水泥中石灰石掺入量及水泥细度对水泥胶砂强度的影响。结果表明,该品种水泥的物理力学性能与普通硅酸盐水泥相似。通过微观分析,证实了石灰石硅酸盐水泥早期水化速度较快,具有早期强度较高的特点。     

Effect of lactic acid on the hydration of portland cement

Effect of lactic acid on the hydration of portland cement has been studied by employing various experimental techniques. Results indicate that lactic acid accelerates the hydration contrary to other α-hydroxy carboxylic acids which act as retarder. Electrical conductivity measurements give an indication that lactic acid forms a salt of calcium lactate during the interaction with calcium hydroxide. Zeta potential measurements give negative test regarding the adsorption of lactic acid portland cement surfaces. SEM photographs show that probably lactic acid accelerates the hydration by increasing the crystalline character of calcium hydroxide, which in turn accelerates the nucleation and growth of the hydration products.     

Application of Powers’ model to modern portland and portland limestone cement pastes

Powers’ model is a simple approach for estimating the relative volumes of hydration products, porosity, and chemical shrinkage present in portland cement paste as a function of its starting water‐to‐cement ratio (w/c) and current degree of hydration. It forms an important link between cement composition, microstructure, and performance, necessary for modeling cement‐based systems. Previous researchers have adapted Powers’ model for inert fillers to illustrate their effects on the hydration, porosity, and chemical shrinkage of blended cements; however, it is well‐documented that limestone is not, in fact, an inert filler, but rather participates in cement hydration through both chemical and physical processes. This research experimentally investigates the applicability of Powers’ model to modern portland cements containing up to 15% by mass finely divided limestone. The results demonstrate that the modified Powers’ model is insufficient for predicting the influence of finely divided limestone additions on the chemical shrinkage of both ordinary portland cement pastes and portland limestone cement pastes. Possible explanations for the discrepancy are discussed and a plausible source is proposed.     

氯化钠对掺磨细矿渣粉硅酸盐水泥基材料活性激发能力和结合方式影响的试验研究

通过在掺磨细矿渣粉配制的硅酸盐混合水泥中掺加0.5%～4%的氯化钠进行的试验研究表明,加入的氯离子约37%～64%与硅酸盐水泥和矿渣形成化学结合状态,24%～50%为游离状态,2%～10%为物理吸附状态;氯化钠掺量在1%以下时水泥石早期强度显著提高,具有明显的活性激发和早强作用;Cl-和SO2-4互相取代产生复合化合物3CaO·Al2O3·(1-xCaCl2·xCaSO4)·yH2O,其x值随水泥石中Cl-浓度的变化而变化.并且与C-S-H混合生长.     

Properties and structure of oil shale ash pastes. II: Mechanical properties and structure

Compressive strength, drying-shrinkage and expansion in water of oil shale ash pastes were studied and compared to the corresponding properties of portland cement paste. X-ray diffraction and some scanning electron microscopy runs were also included in the study. It was concluded that the structure and properties of the ash pastes can be described and explained by the same models which have been suggested for portland cement paste. The only exception was the total porosity of the ash paste which remained unchanged with time. A suitable modification in the structural model of the portland cement paste was suggested to allow for this specific behaviour.     

Test methods for determining potential alkali-silica reactivity in cements

The ASTM C227 test can be modified to develop performance tests for predicting potential alkali-silica reactivity of both portland and blended portland cements. The two methods of test investigated here differed mainly on the choice of the standard reactive aggregate, one using pyrex and the other a naturally occurring reactive silica. Low water/cement and aggregate/cement ratios were found helpful in accelerating expansion of mortar bars stored at 110F (43C). A 14-day test period was considered by the writers to be adequate for the evaluation of relative alkali-silica reactivity of a cement in the methods developed. Test data in 17 portland cements and 10 blended portland cements are reported to show that for this purpose performance tests may be more suitable than chemical specification limits.     

Diffusion of Cs+ and Cl− through sealing materials

The engineering or sealing materials is an integral part of a repository design system for the disposal by isolation of nuclear wastes in geologic media. Cement, concrete, zeolites and clay minerals are some of the promising candidate borehole plugging or sealing materials. In order to evaluate the efficacy of these sealing materials, Cs⁺ and Cl⁻ diffusion studies were conducted on thin cured discs or cement and cement admixtures with zeolite or montmorillonite or silica fume or blast furnace slag. The cement admixtures are superior to straight cement in retarding the migration of Cs⁺ and Cl⁻. The montmorillonite blended cement performs in an intermediate fashion when compared to the straight cement and zeolite or silica fume bearing cements. The diffusions of Cs⁺ and Cl⁻ appear to be related to the pore structure as well as the crystal structures of the phases added or subsequently formed during curing. These results tend to suggest that the addition of 10–20% silica fume or zeolite phase to the portland cement may be very advantageous in resisting the migration of Cs⁺ and, to some extent, Cl⁻ ions across cement pastes.     

自燃煤矸石配制混凝土的试验研究

采用正交试验的方法,研究了自燃煤矸石作为活性混合材料制备煤矸石硅酸盐水泥的可行性,并与煤矸砂、煤矸石共同配制了不同强度等级的混凝土.试验结果表明,阜新高德矿自燃煤矸石可以作为活性混合材料制备煤矸石硅酸盐水泥,且能够与煤矸石粗细集料共同制备C15～C40不同强度等级的混凝土.该混凝土无论是7d还是28 d的强度都好于普通硅酸盐水泥配制的天然集料混凝土,且吃渣量高达混凝土总质量的80％以上.采用煤矸石配制混凝土,不仅可实现固体废弃物的资源化,且缓解了当地缺少硬质石材的难题,具有经济、环保和社会三重效益.     

Phase-Resolved Strain Measurements in Hydrated Ordinary Portland Cement Using Synchrotron X-rays

X-ray diffraction methods developed for the determination of residual stress states in crystalline materials have been applied to study residual strains and strains because of mechanical loading of ordinary portland cement paste. Synchrotron X-rays were used to make in situ measurements of interplanar spacings in the calcium hydroxide (CH) phase of hydrated neat portland cement under uniaxial compression. The results indicate that strains on the order of 1/100 000 can be resolved providing an essentially new technique by which to measure the phase-resolved meso-scale mechanical behavior of cement under different loading conditions. Evaluation of these strain data in view of published elastic parameters for CH suggests that the CH carries a large fraction of the applied stress and that plastic interactions with the matrix are notable.