水泥水化放热与电阻率变化

测定了不同水泥的水化放热和电阻率变化,并做了电阻率变化率和放热速率的对比分析.研究发现:水泥水化1 d的电阻率随累计放热量的增加而增加;电阻率与放热速率随水化时间的变化均能独立地反映水泥水化进程;且水泥水化放热速率曲线的一些特征峰,如:溶解热峰、主教热峰,钙钒石转化峰等,在一定时间偏差范围内,均可在电阻率变化曲线上找到与之对应的突变点.水泥水化放热速率在诱导期达到极小值后先快速增长,再慢速增长,存在转折点,且电阻率变化率有相应峰值与其对应.     

化学合成高纯铝酸钙水泥的特性及应用

研究了化学合成高纯铝酸钙水泥的物理特 性,包括强度发展、凝结时间、水化结合水量和水化放 热特性,并与市售的以传统烧结法生产的水泥进行了 在典型耐火浇注料中的应用比较。结果表明:(1)化 学合成高纯铝酸钙水泥胶砂的强度发展快且充分,早 期强度高;(2)化学合成高纯铝酸钙水泥的水化放热 速率在水化2h时最大,放热快且放热量集中;(3)化 学合成高纯铝酸钙水泥的水化活性较高;(4)化学合 成纯铝酸钙水泥用于耐火浇注料中,浇注料表现出较 高的烘干强度,且浇注料的烧后强度等性能指标也与 用传统烧结水泥的大体相当。     

氧化硼对铝酸钙水泥水化性能的影响（英文）

对比研究了含与不含氧化硼对铝酸钙水泥水化行为的影响。通过测试水泥净浆的水化放热曲线,对比分析了铝酸钙水泥中的氧化硼杂质含量对水泥水化速率的影响,以及水泥水化时的电导率随养护时间的变化,阐述了该杂质对水泥溶解沉淀速率的影响。通过冷冻真空干燥的方法中止水泥水化,继而用X射线衍射和热重分析研究了上述两种水泥净浆的水化产物组成。用维卡仪测定了水泥砂浆的凝结时间,用跳桌法测定了水泥结合浇注料的流动值衰减。结果表明:铝酸钙水泥中的氧化硼杂质缩短了水泥的水化诱导期,加速了水泥水化形成大量沉淀的进程,从而促进了水泥的水化,缩短了砂浆的凝结时间,并加快了水泥结合浇注料的流动值衰减速度。     

粉煤灰-矿粉-水泥三元体系水化放热模型研究

通过直接法研究了在水泥中掺入不同掺量的粉煤灰和矿粉时样品的水化放热速率曲线,通过各样品的水化放热曲线研究粉煤灰-矿粉-水泥三元体系水化放热模型.通过试验实测结果与模型计算结果相比,两者最大误差为8.1％,最小误差仅为3.4％,发现胶凝材料的水化过程符合根据水泥水化建立的水化动力学模型.     

硫对铝酸盐水泥物相组成和浇注料性能的影响

为了研究煤中的硫含量对铝酸盐水泥的物相组成和浇注料性能的影响,选取以不同硫含量的煤为燃料煅烧的两种不同硫含量的CA-50铝酸盐水泥为研究对象,分析了煤中硫含量的增加对水泥熟料物相组成的影响,并用碳硫仪、XRD、SEM和EDS分析了原料和熟料中硫的含量和存在形式,比较了两种铝酸盐水泥结合浇注料的性能。结果表明:煤中硫含量的增加导致水泥中硫铝酸钙含量的增加,进而影响浇注料中水泥的水化过程,推迟了水化产物产生大量沉淀的时间,降低了最高放热温度,提高了24 h养护后的耐压强度。     

CFRC中分散剂甲基纤维素对水泥水化的影响

用直接测温、XRD、SEM及DTA等技术,系统研究了CFRC中分散剂甲基纤维素(MC)对水泥水化的水化热、初期产物与后期产物的影响.实验结果表明:添加质量为水泥干重0.5%的MC,水泥净浆出现了缓凝现象,其水化放热曲线的第二个放热峰被分割成两个放热峰,Ca(OH)2比C-S-H首先成核.在水泥净浆的后期水化中,MC并没有参与反应,其对水泥水化的最终产物没有影响,只作为一种高分子聚合物存在,增强了水泥石的强度.     

缓凝剂对氯氧镁水泥水化历程的影响

为了拓展氯氧镁水泥(MOC)的使用范围,研究了缓凝剂(柠檬酸、硼酸、葡萄糖酸钠)对氯氧镁水泥凝结时间、抗压强度、电阻率、水化热和耐水性的影响,同时采用X射线衍射仪分析了氯氧镁水泥改性后的水化产物。结果表明,掺入缓凝剂会延长氯氧镁水泥的凝结时间,当缓凝剂掺量达到0.75%(质量分数,下同)时,各组试样的28 d抗压强度较空白组分别下降了19.3%、16.7%和20.2%。缓凝剂的掺入降低了水泥浆体电阻率速率曲线和内部温度曲线的峰值,推迟了水化放热速率曲线第二峰值出现时间,即降低了氯氧镁水泥的水化速率,改善了氯氧镁水泥放热集中的现象。缓凝剂能提高氯氧镁水泥的耐水性,当硼酸掺量为0.75%时,软化系数可达到0.79。     

水泥基材料的水化动力学模型

介绍了水泥基材料的水化动力学模型.根据实验测定的水化放热数据,采用模型给出的积分和微分方程,对水泥基材料的水化反应中的3个基本过程即结晶成核与晶体生长(NG)、相边界反应(I)和扩散(D)进行了表征,得到反应速率常数K、反应级数n和表观活化能Ea等动力学参数以及各反应阶段的反应速率与反应度的关系.计算得到的各阶段的反应速率曲线能较好地分段模拟由量热实验得到的胶凝材料实际水化速率dα/dt曲线.观察3个阶段的相互关系,可对水泥基材料复杂的水化机理进行解释.水泥基材料的水化反应存在两种不同的历程:NG-I-D或NG-D.在水化初期NG是控制因素,随着水化程度提高,逐渐转由I或D控制反应.     

Na2SO4对煅烧煤矸石的激发效应

利用TG-DSC、XRD、等温量热计、SEM、Ca(OH)2含量测定等方法,比较研究了掺与不掺Na2SO4时煅烧煤矸石水泥早期水化过程中的Ca(OH)2含量、水化放热速率、水化产物及其形貌、浆体力学强度的差别,分析了Na2SO4对水泥早期水化过程中煅烧煤矸石的激发作用.结果表明,掺入Na2SO4后,水泥试样在水化减速期早期阶段的水化放热速率高,二次水化产物形成的时间早.这反映出Na2SO4对水泥中煅烧煤矸石有明显的激发效应.其外,水泥浆体试样中Ca(OH)2含量明显降低,水泥水化加速期延续的时间短,水化放热速率高;结果还表明,在水化早期,掺Na2SO4的煅烧煤矸石水泥有较多的CSH凝胶和AFt,较少的Ca(OH)2.     

山梨醇对硅酸盐水泥水化及混凝土性能影响

探究了山梨醇对硅酸盐水泥水化放热的影响和混凝土性能的影响。研究发现山梨醇具有降低水泥水化放热速率减小温峰的性能。当山梨醇掺量达到胶材的0.25%,能降低水化放热速率峰值42%。山梨醇会降低混凝土的早期强度,但是对后期混凝土的强度无影响。并进行了XRD和TG-DSC测试,发现山梨醇会减缓早期氢氧化钙的生成,从而达到降低水化放热速率的性能。     

Compatibility between ecocement produced from incinerator ash and reactive aggregates in ASR expansion of mortars

Recently, in Japan, two new-type hydraulic cements, high early strength type ecocement (HEC) and normal type ecocement (NEC), have been developed using incinerator ashes up to 50% of the raw materials. In this study, the compatibility of these ecocements with various types of reactive aggregates with respect to alkali-silica reaction (ASR) was studied. Ordinary Portland cement (OPC) and blast furnace slag cement (BFSC) were also used for a comparative study. Two types of the accelerated mortar bar expansion test, the JIS A1146 and the Danish methods, were used to clarify the expansion behavior of mortars made with the above cements. The influence of a combination of the chemical and mineralogical compositions of cement and the reactive components of aggregate on both the amount of ASR gel and the expansion rate of the mortar was also investigated. From the results, it was found that the expansion behaviors of mortars due to ASR varied significantly depending on a combination of both the mineralogical composition of cement and the reactive component of aggregate.     

Effects of Specific Surface Area and Impurities of Reactive Alumina on Properties of Corundum Based Castables

Effects of specific surface area and tiny amount of impurities of reactive alumina on the workability,sintering and high temperature mechanical strength of corundum based castables were investigated. The results show that the presence of reactive alumina with high specific surface area leads to accelerating of the hydration of calcium aluminate cement,thus shortening the working time and setting time of the castables,which can be ascribed that the critical energy barrier for stable nuclei of hydration products of cement can be reduced by the high specific surface area of reactive alumina. The sintering of the corundum based castables can be accelerated by the reactive alumina with high specific surface area and high amount of impurities, however, the reactive alumina with too high specific surface area and impurities can also lead to noticeable shrinkage of castables. In addition,high temperature mechanical strength of corundum based castables can be decreased by the higher amount of trace impurities of reactive alumina due to formation of lowmelting phase at high temperatures.     

Microstructural changes and evolutions of elastic properties versus temperature of alumina and alumina–magnesia refractory castables

This paper deals with the evolutions of thermo-mechanical properties of castable refractories versus temperature. The measured properties are mainly Young's modulus evaluated by a high temperature ultrasonic technique and thermal expansion followed by dilatometry. Materials are alumina-based low cement castables with a fraction of alumina eventually substituted by spinel or magnesia. The granularity of the different used raw materials is chosen by using a packing model, in order to reduce the final porosity in the hydrated state. The interpretation of results is carried out by considering the materials as composites, constituted of aggregates (size > 100 μm) into a matrix where most of chemical and phase transformations occur. By using two-phase analytical models, it is shown that the evolutions of thermo-elastic properties of castables can be qualitatively predicted from measurements performed in a matrix-equivalent simplified material. Moreover, considering the elastic properties after heat treatment, the castable with magnesia is comparable to the castable processed with synthetic spinel.     

Systemic analysis of MgO hydration effects on alumina–magnesia refractory castables

The use of magnesia sources with high specific surface area and small particle size in the Al₂O₃–MgO system can induce faster in situ spinel (MgAl₂O₄) formation in castable compositions, improving the slag corrosion resistance. However, the higher reactivity of these raw materials lead to an intensive brucite formation (followed by volumetric expansion), spoiling the castable's properties during the curing and drying steps. Considering these aspects, a systemic analysis of three magnesia sources (dead-burnt and caustic ones) was carried out in order to evaluate: (1) their hydration impact on the refractory castables properties, and (2) their bonding ability in cement-free compositions. Mechanical strength, thermogravimetric and Young's modulus tests were conducted during the castables’ curing and drying steps. According to the results, the elastic modulus measurement is an efficient tool to evaluate the magnesia hydration. The addition of proper amounts of calcium aluminate cement and/or silica fume to the castables can inhibit the crack formation and provide suitable mechanical properties. The results also show that under certain conditions, MgO can be used as a binder, replacing calcium aluminate cement and leading to a significant reduction in the castables costs with no drawbacks to their refractoriness.     

亚微米SiO2粉体对无水泥铁沟浇注料性能的影响

以致密刚玉、碳化硅等为主要原料，以w（SiO₂）=99.9%的亚微米SiO₂粉体(d₅₀=0.242μm)为结合剂，制备了一种新型无水泥铁沟浇注料。研究了亚微米SiO₂粉体加入量（质量分数分别为3%、4%、5%、6%、7%、8%、9%）对其性能的影响，并从亚微米SiO₂粉体的粒度分布、红外光谱等角度，分析探讨了亚微米SiO₂粉体的作用机制。结果表明：1)亚微米SiO₂粉体可以单独作为铁沟浇注料的结合剂制备出无水泥铁沟浇注料；2)相比传统铁沟浇注料，无水泥铁沟浇注料在加水量、高温抗折强度等方面取得突破性进展，亚微米SiO₂粉体的最佳加入量为4%～6%（w）。     

新型结合剂SioxX-Zero对喷煤管用无水泥浇注料显微结构和性能的影响

喷煤管是水泥回转窑的关键承力部位,长期承受高温熟料粉尘和气流的剧烈冲刷,需具备优异的高温力学性能。本工作分别以新型SioxX-Zero和传统铝酸钙水泥为结合剂,采用板状刚玉、α-Al₂O₃微粉和碳化硅等为主要原料,分别在1 100 ℃和1 400 ℃热处理3 h,制备了喷煤管用无水泥和低水泥结合Al₂O₃-SiC质浇注料,并研究了新型SioxX-Zero结合剂对浇注料显微结构、常规物理性能和高温力学性能的影响。结果表明:与传统铝酸钙水泥相比,SioxX-Zero能有效提高浇注料流动值和延缓流动值衰减,改善其施工性能。同时,含SioxX-Zero的Al₂O₃-SiC质浇注料中原位生成了数量较多、尺寸较大的针状莫来石,大幅改善了材料的常温抗折/耐压强度、高温抗折强度和高温耐磨性能。     

基于单纯重心型设计法的再生骨料砂浆 配合比设计

再生骨料干拌砂浆是一种绿色新型建筑材料，既解决建筑垃圾的利用问题，又减轻了建筑原材料的过度开采，降低碳排放，是材料工业可持续发展的必然趋势。本文采用单纯重心型设计法对再生骨料掺量、水灰比和水泥用量三个因素进行研究以优化再生骨料干拌砂浆的配合比，以稠度、2 h稠度损失率和抗压强度作为关键的性能评价指标。结果表明，单纯重心型设计法可用于优化再生骨料砂浆的配合比。在优化的配合比下，再生骨料砂浆的稠度、2 h稠度损失率和强度之间可以达到很好的平衡。     

Strength and shrinkage properties of mortar containing a nonstandard high-calcium fly ash

A laboratory study was undertaken to assess the compressive and flexural tensile strength and drying shrinkage properties of mortar mixtures containing high-calcium nonstandard Afsin-Elbistan fly ash (FA). Possibility of using Afsin-Elbistan FA in cement-based materials as shrinkage-reducing or compensation agent was also discussed. Five mortar mixtures including control Portland cement (PC) and FA mortar mixtures were prepared. FA replaced the cement on mass basis at the replacement ratios of 10%, 20%, 30% and 40%. Water-cementitious materials ratio was 0.4 for all mixtures. The mixtures were cured at 65% relative humidity and 20±2 °C. The compressive and flexural tensile strength and drying shrinkage values of the mortar mixtures were measured. The results show that Afsin-Elbistan FA reduced drying shrinkage of the mortar by 40%. Therefore, it was concluded that Afsin-Elbistan FA can be used as a shrinkage-reducing agent. The mortar containing 40% FA expanded. This indicates that Afsin-Elbistan FA may be utilized to compensate drying shrinkage of cement-based materials.     

如何驯服外墙装饰材料中的“野马”——装饰砂浆?

装饰砂浆是一种高性能、高装饰性、环保的建筑装饰材料,由于泛碱、开裂、色差等问题,约束了其在国内市场的发展。本文分析了装饰砂浆目前存在的技术难点与弊病,从产品定位出发,根据中涂砂浆与面层砂浆的性能特点,分别用硅酸盐水泥与高铝水泥作为凝胶材料,结合可分散乳胶粉与各类助剂对配方进行设计,结果表明:对装饰砂浆进行分类,区分产品性能特点,采用硅酸盐水泥作为中涂砂浆配方设计的主要凝胶材料,高铝水泥作为面层砂浆的主要凝胶材料,能有效控制装饰砂浆目前存在的问题。     

Fracture behavior and thermal shock resistance of alumina-spinel castables-Effect of added fused zirconia-alumina

This study aims to clarify the influence of fused zirconia-alumina (FZA) on the fracture behavior and thermal shock resistance (TSR) of alumina-spinel castables, and discover the relationship between toughness parameters and TSR. Alumina-spinel castables with different FZA contents (0, 2, 4, 6, 8, and 10 wt.%) were prepared using tabular alumina, fused spinel, calcium aluminate cement, ultrafine alumina powder, and FZA as raw materials. The fracture behavior and TSR of alumina-spinel castables were determined by a wedge splitting test (WST) and a water quenching test, respectively. The results show that the flexibility of alumina-spinel castables can be significantly enhanced by introducing FZA. With increasing FZA content, the load-displacement curves change from typical brittle fracture behavior to non-linear fracture behavior. The flexibility parameter (ratio of G_F/σ_NT) of the castables increases from 8.3 μm to 13.6 μm when FZA content increases from 0 wt.% to 10 wt.%. The flexibility improvement of castables containing FZA can be attributed to the formation of microcracks caused by the transformation of ZrO₂. The TSR of alumina-spinel castables can also be significantly improved by adding FZA. The ratio of residual cold modulus of rupture (CMOR) of the castables increases from 12.3% to 34.2% when FZA content increases from 0 wt.% to 10 wt.%. The improvement in TSR can be attributed to a decrease in the stored elastic energy and a subsequent increase in the specific fracture energy of the castables. Generally, alumina-spinel castables with non-linear fracture behavior have good thermal shock resistance. There is a significant correlation between the flexibility parameter (G_F/σ_NT ratio) and the ratio of residual CMOR; the correlation coefficient is 0.96.