水泥石脱水相结构特征及其再水化能力

将水泥石在不同温度进行低温煅烧,得到不同的脱水相物质,通过热重-差示扫描热分析、X射线衍射、红外光谱及29Si核磁共振等对水泥石在400,650℃及900℃的脱水相结构特征及其再水化性能、再水化产物的结构特征进行研究.结果表明:在400℃,由水化硅酸钙(C-S-H)凝胶脱水生成了无定形相,在650℃生成了不完全结晶的β-硅酸二钙(C2S),而900℃脱水相中存在结晶程度高的β-C2S.在再水化过程中,400℃和650℃脱水相水化生成了C-S-H凝胶,并且650℃脱水相的水化活性和水化产物聚合程度更高;900℃脱水相的水化活性极低,水化前后矿物结构特征几乎没有发生变化.     

C-S-H及C-S-H脱水相对水泥石结构改性的研究

以C-S-H及C-S-H脱水相作水泥水化物沉淀中心的品种。从理论上阐明了它们是具有较大介电常数、较小物理化学不均匀系数、高分散度的晶种物质,故具有优先吸附的界面效应及优先沉淀的结晶中心作用,可缓和原始矿物表面的高浓度的屏蔽效应及界面的近程析晶,使水化物分布均匀、结构致密,从而提高水泥石强度。C-S-H及C-S-H脱水相两者中,尤以后者作用更显著。     

丁苯橡胶对水泥水化过程及水泥石微观结构的影响

用多种实验手段研究了在普通硅酸盐水泥中掺入丁苯橡胶乳液对水泥水化过程的影响，并用扫描电镜分析了掺入丁苯橡胶后水泥石微观结构形态的改变，从而探讨了丁苯橡胶改善水泥石物理力学性能的机理。     

水化脱水相代石膏试验研究

本试验以粉煤灰和电石渣为主要原材料,加入外加剂,制成一种具有气硬性和水硬性的快凝胶结材料。旨在代替部分或全部建筑石膏生产建筑内墙砌块、内隔墙、装饰板等建筑制品,使石膏建筑制品的耐水性得以改善,为本地区提供一种廉价的新型墙体材料。     

环氧树脂乳液对油井水泥石水化过程和力学性能的影响

本文研究了无固化剂的环氧树脂水泥石,在70℃条件下的水化硬化过程,水化产物和宏观力学性能.结果表明,没有固化剂,在碱性环境和高温条件下,环氧树脂难以完全固化.环氧树脂延缓了水泥的水化过程,不会改变水泥的水化产物.未固化的环氧树脂以膜的形式存在于水泥石中,填充内部孔隙.掺加环氧树脂可提高水泥石的轴心抗压强度,降低其弹性模量,从而改善其使用性能.     

掺超细矿渣粉水泥石水化进程的试验研究

高掺量超细矿渣粉水泥石早期二次水化较慢，随后水化速度逐渐加快，1年后水化速度已接近空白样。而且由于超细矿渣粉的微集料填充效应和火山灰效应，提高了水泥石的密实度。     

丁苯橡胶对水泥化过程及水泥石微观结构的影响

用多种实验手段研究了在普通硅酸盐水泥中掺入丁苯橡胶乳液对水泥水化过程的影响，并用用扫描电镜分析了掺入了苯橡胶后水泥石微观结构形态的改变，从而探讨了丁苯橡胶改善水泥石物理力学性能的机理。     

活化煤矸石浆体脱水及其脱水相再水化研究

结合我国低热值煤应用的实际,研究了煤矸石-石灰-水预处理工艺及预处理浆体脱水和脱水相的再水化。以活化组份量表征煤矸石的预处理程度,用XRD、SEM、氮吸附、热分析法研究了预处理煤矸石水化相及脱水相的组成、脱水相的水化硬化过程。结果表明,预处理煤矸石在780℃和850℃左右脱水具有良好的水硬活性。为在低温条件下利用煤矸石生产胶凝材料提供了理论依据。     

抑制AlN微粉水化最佳热处理制度的研究

选用了3种不同粒径的AlN粉（d50分别为0.5μm、5μm和15μm）,通过TG分析和不同制度下的热处理以及测试其悬浊液的pH值变化,探讨了AlN粉的表面氧化热处理温度和保温时间对AlN水化性能的影响。结果表明：TG分析温度小于1000℃时,AlN的氧化增重均小于0.8%;当热处理温度为900℃、保温1h时,AlN的抗水化性能最好。     

Study on the high‐temperature behavior and rehydration characteristics of hardened cement paste

The high‐temperature behavior and rehydration characteristics of the hardened cement paste and their mechanisms have been studied in this paper. X‐ray diffraction and thermogravimetry are used to establish the effect of elevated temperatures on the mineralogical changes that occurred in the hardened cement paste. The change of microstructure was characterized by scanning electron microscopy. The results showed that with the temperature increased, the compressive strength of hardened cement paste first increased and then decreased. According to micromeasurements, at 400°C, the porosity and average pore diameter of hardened cement paste increased slightly, while at 800°C, the porosity and average pore diameter of hardened cement paste increased sharply. When hardened cement paste was cured after exposing to 400°C, its pore structure and phase composition had no change, while when hardened cement paste was cured after exposing to 800°C, there are new hydration products, and its pore structure may be finer, but it cannot fully recover to the original state. Copyright © 2014 John Wiley & Sons, Ltd.     

Rehydration activity of hydrated cement paste exposed to high temperature

Subjected to the wet surrounding, hydrated cement paste (HCP) exposed to high temperature may exhibit rehydration behavior. This paper presents the influence of the dehydration temperature and the initial water/cement ratio on the rehydration activity of dehydrated cement paste (DCP). Original HCPs were prepared with two water/cement ratios of 0.3 and 0.5, respectively, and cured under the fog‐spraying standard condition for 30thinspacedays. The DCP powders used were obtained by grinding dry HCP less than 75µm and then subjecting to different temperatures, up to 900^°C. The rehydration properties of DCP were evaluated by the required water for standard consistency, the setting time, the rehydrated compressive strength and the microstructure evolution. X‐ray diffraction (XRD) was employed to identify the crystalline phases before and after rehydration. Experimental results showed that the coupled rehydration effect from the dehydrated hydration products and the initially unhydrated cement determined the rehydration behavior of DCP. The rehydration of DCP strongly depended on the dehydration temperature and the water/cement ratio of the original HCP. Copyright © 2010 John Wiley & Sons, Ltd.     

微膨胀型中热水泥在三峡二阶段工程砼中的应用

三峡二阶段工程控制砼用水泥的MgO量为3.5％～5.0％,使砼具有自生体积微膨胀性质,以补偿砼硬化过程中的收缩应力,提高砼抗裂性。试样抽检和观测表明:用MgO量为3.5％～5.0％的微膨胀中热水泥配制砼,具有微膨胀性,最大膨胀量约55μm;一般半年至1年变形趋于稳定。2000年底对大坝砼裂缝调查统计是:无贯穿性裂缝,二类裂缝数为0.171条/万m3、三类裂缝数为0.048条/万m3,均低于三峡工程砼控制二类、三类裂缝数量≤0.5条/万m3要求,为确保三峡工程砼耐久性奠定了基础。     

煤矸石对硬化水泥浆体结构形成的影响

通过对硬化水泥浆体物理力学性能的检测,结合XRD和SEM分析,研究了不同掺量的煤矸石对硬化水泥浆体水化性能的影响。结果表明:随着煤矸石掺量的增加,水泥的标准稠度用水量增加,凝结时间缩短,抗压强度降低,熟料矿物的水化速率提高,水泥-煤矸石体系的水化速率降低。煤矸石掺量不同,水化模式亦不同。     

水泥净浆流动度与混凝土流变性能相关性试验

在工程试配C100自流平混凝土的同时,进行了水泥净浆流动度与混凝土流变性能相关性试验。结果表明,水泥净浆流动度与混凝土流变性能之间没有明显的相关关系;水泥净浆流动度损失率与混凝土保塌性之间也没有明显的相关关系。至少在超高强自流平混凝土的条件下,按GB/T8077—2000测定的水泥净浆流动度与混凝土流变性能的关系值得商榷。     

Influence of heat treatment on the corrosion of high speed steel

The corrosion behaviour of M2 high speed steel, as-received as well as heat-treated under different conditions, has been studied in 0.1 M KCl aqueous solution by corrosion potential measurements, Tafel curves and electrochemical impedance. Heat treatment leads to an increase of the corrosion resistance of high speed steel; the higher the tempering temperature after quenching, the higher the corrosion resistance of the steel. X-ray diffraction, energy dispersive X-ray analysis and scanning electron microscopy were also used to further understand the corrosion behaviour of the different samples. Based on these analyses, the microstructure of the different samples was correlated with their corrosion properties.     

高温处理对PAN基炭纤维热稳定性的影响

将2种PAN基炭纤维经3次2 500℃高温处理,研究了不同次数处理后炭纤维的晶格参数、灰分含量以及炭纤维在静态和流动空气中的热稳定性。结果表明高温处理能改善PAN基炭纤维的石墨微晶结构,减少灰分含量;随着高温处理次数的增加,炭纤维在静态空气和流动空气中的氧化失重率降低,热稳定性提高。     

Study on the hydration heat of binder paste in high-performance concrete

High-performance concrete (HPC) is a type of new concrete materials developed in the recent 10 years. Compared with normal strength concrete (NSC), HPC is made with lower water-binder ratio (W/B), larger dosage of superplasticizer and addition of different types of mineral admixtures. The objective of the article was to evaluate the effect of W/B, superplasticizer and mineral admixtures on the hydration heat of the binder paste in HPC. The testing results showed that the hydration heat reduced with the decrease of W/B of the binder paste. The total hydration heat did not decrease with the incorporation of superplasticizer containing retarding component, however, the hydration exothermic process was delayed. Mineral admixtures greatly reduced the hydration heat and the exothermic rate and prolonged the arrival time of the highest temperature, particularly when two or three types of mineral admixtures were added at the same time (double adding and triple adding). The influence of these three factors on hydration heat may counteract the deficiency of high hydration heat at early stage due to high cement content and high-strength cement usually used in HPC. This way, the influence of temperature stress is alleviated and the durability of concrete is enhanced.     

The effect of undrained heating on a fluid-saturated hardened cement paste

The effect of undrained heating on volume change and induced pore pressure increase is an important point to properly understand the behaviour and evaluate the integrity of an oil well cement sheath submitted to rapid temperature changes. This thermal pressurization of the pore fluid is due to the discrepancy between the thermal expansion coefficients of the pore fluid and of the solid matrix. The equations governing the undrained thermo-hydro-mechanical response of a porous material are presented and the effect of undrained heating is studied experimentally for a saturated hardened cement paste. The measured value of the thermal pressurization coefficient is equal to 0.6 MPa/°C. The drained and undrained thermal expansion coefficients of the hardened cement paste are also measured in the heating tests. The anomalous thermal behaviour of cement paste pore fluid is back analysed from the results of the undrained heating test.     

Two problems in refractory heat treatment

The various forms of refractory heat treatment are considered: drying, initial firing, and heat treatment proper. It is possible to mechanize the treatment completely starting with the molded refractories in ring tunnel ovens with single-row shrinkers. There is a discussion of stages and causes for unsatisfactory working in Russian ultrahigh-temperature shaft ovens for making superdense products from magnesium oxide. Translated from Novye Ogneupory, No. 4, pp. 106 – 108, April, 2009.