Carbonation of low heat portland cement paste precured in water for different time

The carbonation technique was applied to accelerate the hydration of low heat portland cement （LHC）. Before carbonation, the demoulded pastes were precured in water for 0, 2, 7, and 21 d, respectively. The results show that precuring time in water strongly influences the carbonation process. The phenolphthalein test indicates that the paste precured in water for a shorter time is more quickly carbonated than that for a longer time. The content of calcium hydroxide increases with increasing the precuring time in water, whereas, the amount of absorbed carbon dioxide changes contrarily. Scanning electron microscope （SEM） observation shows that portlandite always fills up big air bubbles in the paste during precuring in water, and the mercury intrusion porosimetry （MIP） results show that there are less large capillary pores in the paste precured in water for a longer time. It is found that the paste without precuring in water has more carbon dioxide absorption during curing in carbon dioxide atmosphere, and its total pore volume decreases remarkably with an increase in the carbonation time than that precured in water. X-ray diffraction （XRD） and Brunauer-Emmett-Teller （BET） surface area analyses indicate that the carbonate products are vaterite and calcite; CxSHy formed from carbonation has low BET surface area in comparison with that of C-S-H formed from curing in water.     

Carbonation of low heat portland cement paste procured in water for different time

The carbonation technique was applied to accelerate the hydration of low heat portland cement (LHC). Before carbonation, the demoulded pastes were precured in water for 0, 2, 7, and 21 d, respectively. The results show that procuring time in water strongly influences the carbonation process. The phenolphthalein test indicates that the paste precured in water for a shorter time is more quickly carbonated than that for a longer time. The content of calcium hydroxide increases with increasing the procuring time in water, whereas, the amount of absorbed carbon dioxide changes contrarily. Scanning electron microscope (SEM) observation shows that portlandite always fills up big air bubbles in the paste during precuring in water, and the mercury intrusion porosimetry (MIP) results show that there are less large capillary pores in the paste precured in water for a longer time. It is found that the paste without precuring in water has more carbon dioxide absorption during curing in carbon dioxide atmosphere, and its total pore volume decreases remarkably with an increase in the carbonation time than that precured in water. X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) surface area analyses indicate that the carbonate products are vaterite and calcite; CxSHy,, formed from carbonation has low BET surface area in comparison with that of C-S-H formed from curing in water.     

铁尾矿对普通硅酸盐水泥易烧性的影响

应用ＸＲＤ,ＳＥＭ和化学分析等方法,对利用铁尾矿作原料烧制普通硅酸盐水泥的易烧性进行试验研究,结果表明,铁尾矿可改善水泥生料易烧性,降低烧成温度,铁尾矿在水泥中掺量必须适当,过多或过少对水泥生料易烧性有显著影响。     

高强度复合硅酸盐水泥的研制

研究了一种高强度复合硅酸盐水泥.利用矿渣和硅质渣制备一种高强度的复合硅酸盐水泥,探讨不同掺量对水泥性能的影响,获得水泥基材料性能的互补效应.研究混合材对复合水泥体系的化学成分与物理性能的影响.通过对试验数据的分析,获得最优的混合材配比方案.     

Morphology difference between the alkali activated cement and portland cement paste on multi-scale

The features of alkali activated slag（AAS） and portland cement （PC） were observed on multi-scale,the crack and fracture sections were observed with naked eyes,and SEM and AFM were used to study the structure morphology differences between PC and AAS on micrometer to nano meter scale.The experimental results indicated that the AAS paste had soil like fracture texture and it was composed of mainly C-S-H gel but lacks of crystals,and it had a very strong tendency to shrink and crack.AAS paste is much denser and more homogeneous than PC,and on the nano scale C-S-H nano particle in the AAS paste is much smaller and packs much denser than PC paste.     

Effect of calcium aluminate cement variety on the hydration of portland cement in blended system

Two kinds of CACs with different monocalcium aluminate（CA） contents were used in the PC/CAC（PAC） mixtures. Effects of CA and CACs on the properties of PAC were analyzed by setting times and the compressive strength tests, and also by means of calorimetry, XRD, DTA-TG and ESEM. The experimental results show that the compressive strength of the PAC mortars decreases with increasing content of CAC while it declines sharply with a higher content of CA in CAC. Compared with neat PC paste, the content of calcium hydroxide in hydrates of PAC paste decreases significantly, and the hydration time of PC is prominently prolonged. Additionally, the higher the content of CA in CAC, the more obviously the hydration of PC is delayed, confi rming that the CA phase in CAC plays an important role in the delay of PC hydration.     

低掺量水泥固化土的力学特性及微观结构

针对某滩涂淤泥,开展不同淤泥初始水的质量分数、不同水泥掺量的固化土无侧限抗压强度试验、一维压缩试验以及扫描电镜试验,研究低掺量水泥固化土的力学特性与微观结构特征,探讨其与常规掺量固化土的差异. 结果表明：分界水泥掺量、最低水泥掺量与淤泥初始水的质量分数的线性关系明显;与常规掺量固化土相比,低掺量固化土的强度增长明显较慢,压缩性降低较少;固结屈服应力随水泥掺量增加而增大,在较低掺量区,固结屈服应力与水泥掺量具有非线性关系;低掺量固化土屈服前、后的孔隙形态特征以及孔隙排列特征差异较大,当固结压力小于固结屈服应力时,孔隙未呈现出明显的定向性且排列较为混乱,当固结压力大于固结屈服应力时,随着荷载的增加,孔隙形状变得圆滑,复杂程度降低,孔隙排列逐渐趋向于有序.     

硅酸盐水泥水化动力学简化模型

为了更加清晰地阐明水灰比对硅酸盐水泥水化进程的影响,分析了硅酸盐水泥的水化动力学模型(Tomosawa模型,T模型),并将其简化为由传质过程、相界面反应和扩散过程所组成的简化T模型．结合化学结合水法测定水化程度,应用T模型及简化T模型对两种不同水灰比水泥浆体的水化动力学进行研究．结果表明:水泥水化动力学模型中的参数受水灰比的影响各异,其中与传质过程相关的参数几乎不受水灰比的影响;与相界面反应相关的参数受水灰比的影响较小;而与扩散系数相关的参数受水灰比影响显著．简化T模型可以较好地分段模拟水化速率随水化程度变化的总体趋势,且该趋势不受水灰比影响,但是相界面反应控制向扩散过程控制转变时的临界水化程度受到水灰比的影响,且随水灰比增加,临界水化程度增大．     

Influence of cellulose ethers on hydration products of portland cement

Cellulose ethers are widely used to mortar formulations,and it is significant to understand the interaction between cellulose ethers and cement pastes.FT-IR spectra,thermal analysis and SEM are used to investigate hydration products in the cement pastes modified by HEMC and HPMC in this article.The results show that the hydration products in modified cement pastes were finally identical with those in the unmodified cement paste,but the major hydration products,such as CH(calcium hydroxide),ettringite and C-...     

A binder of phosphogypsum-ground granulated blast furnace slag-ordinary portland cement

A new hydraulic cementitious binder was developed by mainly utilizing industrial byproducts phosphogypsum(PG)and ground granulated blast furnace slag(GGBFS)with small addition of ordinary portland cement(OPC).The hydration process and microstructure were studied by X-ray diffraction(XRD) and scanning electronic microscopy(SEM).OPC hydrated first at early age to form primarily C-S-H gel,ettringite and calcium hydroxide(CH).GGBFS activated by CH and sulfate ions hydrated continuously at later age,producing mo...     

Influence of sugar filter mud on formation of portland cement clinker

To explore the mechanisms of filter mud (FM) in the portland cement clinker formation, and to make effective use of FM in the cement production as lime-based raw materials, the influences of FM on the apparent activation energy of calcium carbonate decomposition, liquid phase amount, crystalline phase and tricalcium silicate polymorphism were investigated by TA, SEM and XRD. The experimental results show that FM can reduce apparent activation energy of calcium carbonate decomposition, and increase liquid phase amount. Appropriate FM replacement ratios are useful to promoting the C₃S formation and heightening the C₃S content. New phases of α-C₂S and C₂S·0.5Ca₃ (PO₄)₂ can be found in the clinkers while the ratios are above 15%. In addition, impurities in FM can induce the C₃S polymorph to transform.     

The influence of oleic acid on the hydration and mechanical properties of portland cement

To investigate the effects of OA on the portland cement using oleic acid （OA） as grinding aid and the effects of OA on the portland cement, we characterized the different perfermances of the cement, discussed the characteristics of properties. The results reveal that the OA can reduce the water requirement of normal consistency. With the content of OA added, setting time was extended. The OA can significantly improve the rheological properties of cement-based materials, while the compressive strength decreases.     

Effect of corrosive solutions on C-S-H microstructure in portland cement paste with fly ash

By means of ²⁹Si and ²⁷Al magic angle spinning nuclear magnetic resonance (MAS NMR) combined with deconvolution technique, X-ray diffraction (XRD), scanning electron microscopy (SEM) as well as energy dispersive X-ray system(EDX), the effect of 5 wt% corrosive solutions (viz. 5 wt% Na₂SO₄, MgSO₄, Na2SO4+NaCl and Na₂SO₄+NaCl+Na₂CO₃) on C-S-H microstructure in Portland cement containing 30 wt% fly ash was investigated.The results show that, in MgSO₄ solution, Mg²⁺ promotes the decalcification of C-S-H by SO ₄ ^2- ,increasing silicate tetrahedra polymerization and mean chain length (MCL) of C-S-H. However, the substituting degree of Al³⁺ for Si⁴⁺ (Al[4]/Si) in the paste does not change evidently. Effect of Na²SO⁴ solution on C-S-H is not significantly influenced by NaCl solution, while the MCL and Al[4]/Si of C-S-H in fly ashcement paste slightly change. However, the decalcification of C-S-H by SO ₄ ^2- and CO ₃ ^2- attack, as well as the activation of fly ash by SO ₄ ^2- attack will increase the MCL and Al[4]/Si, which are both higher than that under Na₂SO₄ corrosion, MgSO₄ or Na₂SO₄ +NaCl coordination corrosion.     

掺入普通硅酸盐水泥的粉煤灰地聚物混凝土力学性能与微观特征

既有研究表明,在粉煤灰地聚物混凝土（FGC）中掺入少量普通硅酸盐水泥颗粒,能够增强其在常温养护后的力学性能,但这个结果尚未与早期接受高温养护且不含普通硅酸盐水泥的FGC进行力学特征对比,以验证其可实用程度。为更加贴近实际工程需求,将不含水泥颗粒且接受热固化的FGC与含有少量水泥颗粒仅接受室温固化的FGC进行了包括泊松比在内的基本力学性能测试和比较。为了从微观机制上解释力学性能的测试结果,进行了包括SEM、EDS、XRD、FTIR、Micro-CT等的分析。结果表明：常温养护下含有少量水泥颗粒的FGC各项力学性能与不含水泥颗粒并接受热固化的FGC相近,临破坏前的试件横向应变与纵向应变之比均接近1.0,均有突出的横向变形能力;掺量8%的水泥颗粒在室温条件下对FGC聚合反应的促进效果接近FGC接受高温养护,在形成更为合理的微观孔隙结构方面,改进后的FGC在常温养护条件下优于高温养护FGC。     

铁尾矿配料的普通水泥熟料形成及其节能效果

研究不掺加铁尾矿、单掺铁尾矿及铁尾矿与矿化剂复掺时普通水泥熟料的形成过程 ,确定铁尾矿配料时熟料形成动力学特性 ,对不同配料的熟料形成的反应表观活化能和铁尾矿配料节能效果进行理论计算和分析     

Influence of the aggregate volume on the electrical resistivity and properties of portland cement concretes

The electrical resistivity of concretes with various aggregate volume fractions (V _a) of 0%–70% at water/cement (W/C) ratios of 0.4 and 0.5 during 1 day was monitored. It is found that the addition of normal aggregate to cement paste leads to a regular increase in concrete resistivity at each hydration stage and the electrical resistivity has a deeper increase for the lower W/C at a fixed aggregate volume fraction. The number of normalized resistivity (NR) of concrete to its paste matrix was introduced, which is only a function of aggregate volume fraction (V _a). The quantitative relationships give an alternative method for the prediction of aggregate volume in the concrete. A logarithmic relation is established between the elastic modulus of concrete at 7 days or 28 days and the electrical resistivity of concrete at 1 day. The equations are obtained, the compressive strength of concrete at 7 days or 28 days can be determined by the electrical resistivity of concrete at 1 day and the used aggregate content in the concrete. The quantitative relationships give a non-destructive test (NDT) method for prediction of concrete elastic modulus and compressive strength.     

Effect of Fine Steel Slag Powder on the Early Hydration Process of Portland Cement

1 IntroductionSteel slag is the waste residue of fluxing mineralsused in the process of steel producing. Its dischargeamount is about 10 % of the production of steel . Steelslag hasn’t been utilized widely and effectively in a longperiod of time[1]. Hundreds of million tons of steel slagare deposited,andthe amount is still increasing withtensof milliontons every year .The deposited steel slag occu-pies great amounts of farmlands and induces serious en-vironment problems . The main chemical c…     

变温下 Ba2＋对水泥浆体C－S－H微结构的影响

为从分子尺度优化C－S－H微结构提供理论依据,采用模拟大体积混凝土内部变温历程的养护制度,运用29 Si魔角旋转核磁共振（29 Si MAS NMR）结合去卷积技术,研究了变温条件下Ba（OH）2掺量为1.0％时对水泥浆体C－S－H微结构的影响规律。结果表明：在变温条件下掺加Ba（OH）2提高了水泥浆体中硅酸盐矿物水化程度,尤其在水化早期（3 d）时硅酸盐矿物水化程度增幅较大,进而使C－S－H结构中硅氧四面体二聚体数量增加,导致其C－S－H平均分子链长（MCL）显著低于纯水泥浆体,避免了纯水泥浆体在降温阶段出现C－S－H的MCL降低的现象。同时,掺加Ba（OH）2进一步降低了水泥浆体在变温过程下C－S－H中Al3＋取代Si4＋的程度。     

超细水泥注浆材料煤壁注浆加固试验研究

目前工作面煤壁注浆加固主要采用有机注浆材料,成本过高,普通水泥注浆材料在煤体中扩散性差,且与煤体黏接力小.将成本低廉的超细水泥注浆材料应用于煤壁注浆加固,研究了浆体黏度、凝结时间以及结石体强度等性能,并在山西晋煤集团赵庄煤业有限责任公司3305工作面撤架通道煤壁进行了注浆加固试验,结果发现,浆液凝结时间短,结石体强度达到9.6MPa,浆液扩散半径大于3 m,煤体黏接强度达到3.6MPa,证明超细水泥注浆材料可以在煤壁中良好渗透扩散,对控制煤壁片帮具有良好效果.