Specific surface of two hydrated cements differing in strength

Specific surface, S, of CSH-gel particles of disordered layered structure, was studied by water sorption/retention in two cement pastes differing in strength, i.e. C-33 (weaker) and C-43 (stronger), w/c=0.4. Hydration time in liquid phase was t _h=1 and 6 months, followed by hydration in water vapour either on increasing stepwise the relative humidity, RH=0.5→0.95→1.0 (WS) or on its lowering in an inverse order (WR). Specific surface was estimated from evaporable (sorbed) water content, EV (110°C), assuming a bi- and three-molecular sorbed water layer at RH=0.5 or 0.95, respectively (WS). On WR it was three- and three- to four-molecular (50 to 75%), respectively, causing a hysteresis of sorption isotherm. At RH=0.5 the S increased with cement strength from 146 m² g^-1 (C-33, 1 m) to 166 m² g^-1 (C-43, 1 m) and with hydration time to 163 (C-33, 6 m) and to 204 m² g^-1 (C-43, 6 m). At RH=1.0 (and 0.95), higher S-value were measured but these differences were smaller: S amounted to 190-200 m² g^-1 in C-33 (1 and 6 m) and 198-210 m² g-1 in C-43 (1 and 6 m). Thus no collapse occurred on air drying of paste C-43 (6 m). This revised version was published online in July 2006 with corrections to the Cover Date.     

Calorimetric studies of refractory corundum

Calorimetry has been used in the investigations of calcium aluminate materials produced as a binder for aluminate-corundum composites of high refractoriness. The kinetics and of hydration process was thus characterized and the optimum compositions of initial binders and cement-corundum refractory filler blends could be selected for further tests. The acceleration of heat evolution - the shortening of so-called induction period and relatively high heat output in the presence of corundum was observed. It means the acceleration of hydration process, that is early crystallisation of hydration products and subsequent further dissolution of initial anhydrous aluminate phases. In the presence of fine grained corundum particles these phenomena should be attributed to the nucleating effect of fine corundum particles. This revised version was published online in July 2006 with corrections to the Cover Date.     

Catalytic performance of cement clinker supported nickel catalyst in glycerol dry reforming

The paper reports the development of cement clinker-supported nickel （with metal loadings of 5 wt%, 10 wt%, 15 wt% and 20 wt%） catalysts for glycerol dry （CO2） reforming reaction. XRF results showed that CaO constituted 62.0% of cement clinker. The physicochemical characterization of the catalysts revealed 32-folds increment of BET surface area （SBET） with the addition of nickel metal into the cement clinker, which was also corroborated by FESEM images. Significantly, XRD results suggested different types of Ni oxides formation with Ni loading, whilst Ca3SiO5 and Ca2Al0.67Mn0.33FeO5 were the main crystallite species for pure cement clinker. Temperature-programmed reduction analysis yielded three domains of H2 reduction peaks, viz. centered at approximately 750 K referred to as type-Ⅰ peaks, another peaks at 820 K denoted as type-Ⅱ peaks and the highest reduction peaks, type-Ⅲ recorded at above 1000 K. 20 wt% Ni was found to be the best loading with the highest XG and H2 yield, whilst the lowest methanation activity. Syngas with lower H2/CO ratios （0.6 to 1.5） were readily produced from glycerol dry reforming at CO2-to-Glycerol feed ratio （CGR） of unity. Nonetheless, carbon deposit comprised of whisker type （Cv） and graphitic-like type （Cc） species were found to be in majority on 20 wt%Ni/CC catalysts.     

Reactivity of fly ash in cement paste studied by means of thermogravimetry and isothermal calorimetry

Four paste mixtures with varying replacement level of the cement content by fly ash have been studied. Due to fly ash, the acceleration period decreased and a third hydration peak was noticed with isothermal calorimetry. The total heat after 7 days increased with increasing fly ash content. From 1 to 7 days, thermogravimetry showed a higher chemically bound water and Ca(OH)₂-content for the pastes with fly ash. Between 7 and 14 days the calcium hydroxide started to be depleted due to the pozzolanic reaction. A unique relation was found between calcium hydroxide and total heat development.     

生态水泥

介绍了生态水泥的新概念,并对城市垃圾、污泥等废弃物的处理现状、生态水泥的生产工艺和国内外生态水泥的现状进行了论述.用城市垃圾和污泥来生产生态水泥拓宽了原材料来源,减少了天然资源的消耗,降低了水泥生产的成本,是一条很有前途的、有利于水泥工业可持续发展的途径.     

Improved Interfacial Bonding Strength and Reliability of Functionalized Graphene Oxide for Cement Reinforcement Applications

Poor bonding strength between nanomaterials and cement composites inevitably lead to the failure of reinforcement. Herein, a novel functionalization method for the fabrication of functionalized graphene oxide (FGO), which is capable of forming highly reliable covalent bonds with cement hydration products, and therefore, suitable for use as an efficient reinforcing agent for cement composites, is discussed. The bonding strength between cement and aggregates was improved more than 21 times with the reinforcement of FGO. The fabricated FGO also demonstrated many important features, including high reliability in cement pastes, good dispersibility, and efficient structural refinement of cement hydration products. With the incorporation of FGO, cement mortar samples demonstrated up to 40 % increased early and ultimate strength. Such results make the fast demolding and manufacture of light constructions become highly possible, and show strong advantages on improving productivity, saving cost, and reducing CO₂ emissions in practical applications.     

Theory of Microbial Carbonate Precipitation and Its Application in Restoration of Cement-based Materials Defects

Bacterial induced carbonate mineralization has been demonstrated as a new potential method for restoration of limestones in historic buildings and monuments. We claim here the formation of calcium carbonate was controlled by extracellular polymeric substances (EPS) isolated from Bacillus pasteurii. The process of crystallization nucleation was accelerated in the presence of cells and inhibited in the presence of EPS. The CaCO₃ film deposited on cement paste surface was about 100 µm after 7 d treatment. The results of various restoring methods showed that higher decrease of water absorption of cement paste was gained in brushing application in the presence of agar, which could maintain urease with high activity in long term compared to spraying method. The coefficient of capillary suction of cement paste treated with brushing method was reduced by 90%. Mixed media consisted of sands, urea, Ca²⁺ and concentrated biomass, was injected into artificial cracks of cement paste followed by continual nutrient supplement, and CaCO₃ particles were precipitated gradually between sands particles which were combined with cement matrix. The results showed that the compressive strength of recovered specimens was restored to 84%, which demonstrated that this kind of bio‐restoration method is effective in repairing surface defects of cement‐based materials.     

火焰原子吸收分光光度法测定水泥中的铁和锰的研究

对火焰原子吸收分光光度法定水泥中的铁和锰的方法进行了研究.结果表明,在选定的最佳仪器条件下,测定水泥中铁和锰的RSD分别为0.45％和2.68％,回收率分别为97.0％～99.0％和98.0％～102.0％,该法操作简单、测试快速、结果准确稳定.     

核磁共振法研究CH2=CHSi（OET）3的水化反应

高强水泥的生产近年来巳成为许多国家发展水泥生产的一个主要方向。在水泥中加入有机单体可以改善混凝土的质量,如加重量比为3％的有机硅烷偶联剂乙烯基三乙氧基硅烷CH_2=CHSi(OEt)_3(简称VTES)于水泥中,即可在较大程度上增加水泥石的强度。