钙硅比对固硫灰蒸压混凝土性能的影响

固硫灰中CaO含量一般高于粉煤灰而SiO_2含量则低于粉煤灰,因此粉煤灰加气混凝土的钙硅比不宜直接用于固硫灰加气混凝土。改变燃煤灰渣和石灰的相对含量以调节蒸压混凝土的钙硅比,并研究钙硅比对水化产物、干密度、抗压强度及干燥收缩性能的影响。结果显示,干密度随钙硅比增大而增大;存在某一钙硅比使其抗压强度最高且干缩性能最小。当设计固硫灰蒸压混凝土配合比时,为达到较高的力学性能,其钙硅比应高于粉煤灰加气混凝土。     

硫铝酸盐复合水泥体系水化特征研究

通过正交试验研究了硫铝酸盐复合水泥中不同掺量的普通硅酸盐水泥、石膏、硅灰及粉煤灰对其强度、自收缩以及水化热的影响。结果表明:普通硅酸盐水泥及石膏的掺入显著改变了硫铝酸盐复合水泥水化进程,硅灰及粉煤灰是影响后期强度的主要因素;自收缩试验结果表明普通硅酸盐水泥和石膏是影响硫铝酸盐复合水泥水化早期自收缩的主要因素;水化热测试结果表明粉煤灰和普通硅酸盐水泥在水化前6 h起到显著作用,粉煤灰降低了水化放热,而普通硅酸盐水泥增加水化放热;硅灰及石膏对6~24 h水化放热影响显著。结合XRD及SEM测试结果,表明普通硅酸盐水泥和石膏的存在加速了硫铝酸盐复合水泥水化早期钙矾石生成,随着石膏浓度的下降,发生转晶(AFm),随着后期硫铝酸盐水泥中β-C₂S的水化以及硅灰、粉煤灰的火山灰反应产生C-S-H凝胶,使得体系致密化。     

改性石膏对磷渣混凝土强度激发作用的研究

本文通过实验手段,研究了改性石膏对磷渣混凝土强度的影响,并结合XRD、SEM分析改性石膏-磷渣混凝土水化产物的结晶形态和矿物组成。结果表明：在磷渣粉掺量相同的情况下,加入天然石膏、120℃烧石膏、550℃烧石膏激发剂后,水化产物主要是水化硅酸钙、钙矾石,因此,磷渣混凝土抗压强度有了不同程度的提高,其中外掺6%的550℃烧石膏作激发剂的磷渣混凝土抗压强度最大。     

半浸泡硫铝酸盐水泥混凝土蒸发区孔结构变化

硫铝酸盐水泥水化需水量大、水化速度快，凝结硬化后留下的大量未水化水泥在后期继续水化生成钙矾石，影响混凝土的孔结构变化和力学性能发展。用半浸泡方式模拟半掩埋混凝土实际工况，运用背散射电镜和核磁共振等微观测试手段，研究了水灰比为0.35、0.45和0.55的硫铝酸盐水泥混凝土半浸泡35 d、70 d和130 d后蒸发区孔结构和混凝土抗压强度变化规律，结果表明：水灰比为0.35和0.45的混凝土孔隙率呈现先增大后降低再增大的变化特点；水灰比为0.55的混凝土孔隙率呈现先降低后增大的变化特点。研究表明：硫铝酸盐水泥凝结硬化后水化生成的钙矾石会产生结晶膨胀和填充密实两种效应，共同影响硫铝酸盐水泥混凝土孔结构变化。     

大型蒸汽动能磨制备超细固硫灰的工艺

利用电厂温度为250℃、入口压力为0.25 MPa的过热蒸汽,采用LNSJ-350A型蒸汽动能磨对固硫灰渣进行超细加工。结果表明,制得的超细固硫灰平均粒径为4.42μm,产量为10.8 t/h,加工每吨固硫灰消耗蒸汽0.93 t,电耗为19.97 kW·h;以质量分数为10%的超细固硫灰为掺合料制备强度等级为32.5的复合硅酸盐水泥,其强度和安定性均符合国家的标准要求。     

掺固硫灰活性粉末混凝土的制备和性能

进行掺固硫灰活性粉末混凝土(RPC)配合比的正交设计试验,研究了养护制度对掺固硫灰RPC强度和收缩性能的影响以及固硫灰对RPC收缩性能的影响。结果表明:应用固硫灰、硅灰、高效减水剂、中级石英砂、P·O42.5R及湿热养护工艺,可配制出抗折强度26 MPa、抗压强度140 MPa的活性粉末混凝土;湿热养护可促进掺固硫灰RPC的水化,形成较致密的结构,其早期强度比标准养护高30 MPa左右,但高温使早期形成的AFt转变成AFm,故后期的强度有所倒缩;与标准养护相比,湿热养护促进掺固硫灰RPC的早期收缩,降低了其后期干缩,但总体收缩率仍大于标准养护;固硫灰的膨胀性特性可有效改善RPC自收缩大的缺点。     

超细镁渣微粉-水泥复合胶凝材料的性能及水化机理

镁合金被誉为“21世纪绿色工程金属结构材料”,我国皮江法炼镁所得镁渣规模庞大、亟待解决，制备建筑材料是消纳镁渣的重要渠道，但国内外相关研究屈指可数，且普遍以镁渣耦合其他固废及水泥制备复合胶凝材料为主，鲜有针对镁渣-水泥简单体系的细致研究，故镁渣水化及其对水泥水化的影响机制尚未明确。本工作通过探究超细镁渣微粉-水泥复合胶凝材料(MS-C)新拌浆体和硬化浆体的性能、组成及结构演化规律，分析超细镁渣微粉对MS-C水化进程的影响机制，进一步揭示镁渣-水泥的协同水化机理。镁渣中的硅酸二钙以低活性γ-C₂S为主，超细粉磨是发挥其填充效应的关键途径，掺入30%的超细镁渣粉使水泥中1 000 nm以上孔含量由7.98%降低至6.83%。在减水剂作用下，MS-C浆体的流动性随超细镁渣微粉掺量的增大而增大，在无减水剂时其作用相反。低掺量超细镁渣微粉的水化及弱胶凝作用可增大其填充效应对强度的贡献，并促进Ca(OH)₂和C-S-H凝胶的生成，使得低超细镁渣微粉掺量的MS-C获得优于纯水泥的28 d力学性能。本研究获得了超细镁渣微粉-水泥水化特性的基础结论，为提高镁渣...     

铅锌渣生态胶凝材料的制备及水化特性研究

铅锌冶炼渣经高温熔融,水淬急冷会形成玻璃形态物料,在碱性条件下具有一定的活性,可用于生产建材掺合料和胶凝材料。以铅锌渣为主原料,添加少量水氯镁石、钙基固废和水泥作为激发剂,成功制备了铅锌渣生态胶凝材料。通过电子万能试验机、X射线衍射仪(XRD)分析了胶凝材料的力学性能和水化产物特征;通过正交试验的方法研究了胶凝材料力学性能的变化;并通过扫描电镜(SEM)、傅里叶红外光谱(FT-IR)、压汞仪(MIP)等方法分析了胶凝材料水化产物的微观形貌及结构特征。结果表明,当水氯镁石掺量为3%(质量分数),固废总掺量为70%(质量分数),水灰比为0.4,钙基固废掺量为16%(质量分数)时,制备出的铅锌渣生态胶凝材料性能最优,其28 d抗压强度达到9.73 MPa,且水灰比为影响抗压强度的第一因素;XRD分析表明,胶凝材料发生了聚合反应,生成了-Si-O-Si-的结构;SEM分析表明,胶凝材料水化产物微观下呈现蜂窝状结构,这种结构激发了其潜在水化活性,提升了材料的力学性能;FT-IR分析表明,Si-O键逐渐聚合为Si-O-Si键,C-S-H中硅氧四面体聚合度增加;MIP分析表明,胶凝材料的孔径较小,硬化体结构密实,强度较大。     

稻壳灰-水泥胶凝体系的水化动力学模型

稻壳灰(RHA)是稻壳控制燃烧产生的高活性火山灰材料,广泛用作生产高性能混凝土的矿物掺合料。稻壳灰的加入对水泥水化有着复杂的影响,目前的模型并不能解释所有这些复杂的影响。通过考虑稻壳灰对复合胶凝体系的稀释效应、化学效应、稻壳灰多孔结构对于水的吸收和释放等因素,建立了RHA-水泥胶凝体系的水化动力学模型,并以水灰比、环境温度,RHA颗粒细度和掺量等为变化参数,通过模型计算与试验结果相比较,证明所建立的模型可较好地模拟含RHA-水泥胶凝体系的水化进程,可用于预测RHA-水泥胶凝体系的水化程度随龄期的变化规律。结果表明,RHA-水泥胶凝体系的水化程度与水灰比、环境温度和比表面积是成正比的关系。研究可为稻壳灰在水泥中的应用提供依据,同时达到提高水泥的经济性和节约资源的目的。     

固井水泥石孔隙结构演变及力学强度发展规律

本研究以水泥水化数值模拟模型HYMOSTRUC3D为基础,建立了固井水泥浆水化模型,获取了固井水泥石的CH含量和抗压强度,并分别与实验所得固井水泥石的CH含量和抗压强度进行对比,模拟结果与实验结果的偏差分别为0.7％～8.7％和0.5％～10.7％,结果吻合较好,验证了所建模型的准确性.然后,基于所建模型探究了水泥矿物成分(C3S、C2S、C3A和C4AF)、水化产物(C-S-H和CH)、孔隙率、孔径分布等随水灰比和水化龄期的变化关系,并在Para View中重建了水泥石三维微结构.此外,分别采用Ryshkewitch方程、Schiller方程和二次线性方程探讨了水泥石的抗压强度与总孔隙率、毛细孔隙率的变化关系.研究结果表明:(1)水泥水化过程中,固井水泥石的孔隙率逐渐减小,孔径分布逐渐变窄,抗压强度逐渐增大;随水灰比的增大,孔隙率相应增大,孔径分布范围变宽,抗压强度减小.(2)水泥石的抗压强度与总孔隙率、毛细孔隙率呈负相关,采用Ryshkewitch方程、Schiller方程和二次线性方程分别拟合水泥石的抗压强度与总孔隙率、毛细孔隙率的关系,拟合决定性系数R2分别为0.92、0.85、0.91和0.97、0.95、0.97.(3)相比于Schiller方程和二次线性方程,Ryshkewitch方程在研究水泥石抗压强度与总孔隙率、毛细孔隙率的关系时更具普适性,毛细孔隙率是决定抗压强度的主要因素.(4)可采用y=191.5e-0.074x开展固井水泥浆抗压强度发展和毛细孔隙率变化规律的预测和研究.     

脱硫石膏对大掺量粉煤灰-矿渣粉干混砂浆性能的影响

针对大掺量粉煤灰、矿渣粉导致干混砂浆早期强度和后期强度较低的问题,研究脱硫石膏对该干混砂浆性能的影响;采用X射线衍射、扫描电镜及孔结构分析等手段进行微观机理讨论。结果表明,在大掺量粉煤灰矿粉干混砂浆中掺加占胶凝材料总质量6%～8%的脱硫石膏,对和易性无不良影响,并可显著提高浆体的抗压强度及拉伸粘结强度,收缩率降低10%以上,并改善抗碳化能力,使砂浆体积更稳定;脱硫石膏对粉煤灰及矿渣粉起到激发硫酸盐和碱性的双重作用,并在一定程度上促进水泥水化;胶凝材料的水化产物改善砂浆浆体内部结构,使砂浆浆体中的孔隙大大减少。     

Effect of water curing conditions on the hydration degree and compressive strengths of fly ash–cement paste

This paper explains the effect of water curing condition on compressive strengths of fly ash–cement paste by quantitative data of hydration degree. Hydration of fly ash–cement paste was estimated by Rietveld analysis and selective dissolution. The result shows that the hydration degree of belite is affected by water curing conditions, more so than that of fly ash and alite. Fly ash still continues to hydrate even without an extra, external supply of water. The strong dependence of fly ash–cement concrete on curing conditions does not come from the hydration degree of fly ash, but rather comes from the hydration degree of cement, especially belite. When the water to binder ratio is low enough, the hydration of cement plus small hydration of fly ash are considered to be enough for adequate compressive strength at the beginning. Then, compressive strength of fly ash–cement paste becomes less sensitive to the water curing period.     

石膏对石灰石粉水泥基材料水化及硬化性能的影响

针对我国目前非荷载作用下混凝土严重开裂的问题,以"比表面积较低的水泥熟料-比表面积较高的掺合料-足够掺量的石膏"构成的胶凝材料体系为研究对象,通过水化热速率、X射线衍射(XRD)、扫描电子显微镜(SEM)、压汞法(MIP)及热重-差示扫描量热法(TG-DSC)等手段,研究石膏对石灰石粉水泥基材料水化及硬化体微结构的影响。结果表明,石灰石粉能够加速C3A与石膏作用生成钙矾石相,在足量石膏存在的条件下,能够阻碍钙矾石向低硫型硫铝酸钙转变;石灰石粉的掺入与石膏一起延缓了C3A的水化;在石灰石粉和足够石膏同时存在的情况下,C3A水化生成具有膨胀性的水化碳铝酸钙和高硫型硫铝酸钙,补偿了收缩,提高了水泥基材料的抗裂性能;熟料粗磨、掺合料细磨及较高石膏掺量的胶凝材料体系配制的C30和C50等级混凝土,强度能持续增大,从28d到180d,强度分别提高了36.7%和33.3%,混凝土结构紧密、孔隙率低、有害孔含量少。     

碱式硫酸镁水泥耐酸腐蚀性能研究

为了研究碱式硫酸镁水泥耐酸腐蚀性能,将不同配比的水泥试样分别在柠檬酸溶液及水中浸泡不同龄期,再进行质量变化测定及抗折强度和抗压强度试验。采用XRD与SEM技术分析不同配比水泥试样浸泡于两种溶液后的物相组成和显微形貌。结果表明,掺入的矿渣和粉煤灰对碱式硫酸镁水泥具有良好的密实填充作用,降低了水泥的孔隙率,有效阻止了侵蚀介质的进入,其耐酸腐蚀性能与未掺矿渣和粉煤灰的碱式硫酸镁水泥相比有明显提升,其中,掺矿渣的碱式硫酸镁水泥耐酸腐蚀性能更优。     

On the interaction of Class C fly ash with Portland cement–calcium sulfoaluminate cement binder

Shrinkage cracking in concrete is a widespread problem, especially in concrete structures with high surface-to-volume ratio such as bridge decks. Expansive cements based on calcium sulfoaluminate phase were developed to mitigate the shrinkage cracking of concrete. The compressive stress induced due to restrained expansion of concrete has been shown to counteract the tensile stress generated during drying shrinkage. This research attempts to address the differential behavior of fly ash type (i.e., Class C vs. Class F) on early-age expansion and hydration characteristics of ordinary Portland cement (OPC)–calcium sulfoaluminate (CSA) cement blend. It was observed earlier that the presence of Class C fly ash (CFA), unlike Class F fly ash, shortened the expansion duration of OPC–CSA cement blend, which was hypothesized to be correlated to early depletion of gypsum. This paper presents a detailed verification of the hypothesis. Addition of external gypsum to OPC–CSA–CFA blend led to simultaneous increase in expansion and disappearance of a shoulder peak in the calorimetric curve. Thermodynamic calculations using a geochemical modeling program (GEMS-PSI) revealed higher saturation levels of ettringite in presence of external gypsum, which led to higher crystallization stress, and thereby increased expansion.     

The hydration properties of pastes containing municipal solid waste incinerator fly ash slag

This study investigated the hydration properties of Type I, Type III and Type V cements, mixed with municipal solid waste incinerator fly ash, to produce slag-blended cement pastes. The setting time of slag-blended cement pastes that contained 40% slag showed significantly retardation the setting time compared to those with a 10% or even a 20% slag replacement. The compressive strength of slag-blended cement paste samples containing 10 and 20% of slag, varied from 95 to 110% that developed by the plain cement pastes at later stages. An increased blend ratio, due to the filling of pores by C-S-H formed during pozzolanic reaction tended to become more pronounced with time. This resulting densification and enhanced later strength was caused by the shifting of the gel pores. It was found that the degree of hydration was slow in early stages, but it increased with increasing curing time. The results indicated that it is feasible to use MSWI fly ash slag to replace up to 20% of the material with three types of ordinary Portland cement.     

Compressive strength and drying shrinkage of fly ash-bottom ash-silica fume multi-blended cement mortars

This paper studies the physical properties, compressive strength and drying shrinkage of multi-blended cement under different curing methods. Fly ash, ground bottom ash and undensified silica fume were used to replace part of cement up to 50% by weight. Specimens were cured in air at ambient temperature, water at 25, 40 and 60 °C, sealed with plastic sheeting for 28 days. The results show that absorption and volume of permeable pore space (voids) of blended cement mortars at 28 day under all curing methods tend to increase with increasing silica fume replacement. The compressive strength of blended cement with fly ash and bottom ash was lower than that of Portland cement control at all curing condition while blended cement with silica fume shows higher compressive strength. In addition, the compressive strength of specimens cured with water increased with increasing curing temperature. The drying shrinkage of all blended cement mortar cured in air was lower than that of Portland cement control while the drying shrinkage of blended cement mortar containing silica fume, cured with plastic sealed and water at 25 °C was higher than Portland cement control due to pore refinement and high autogenous shrinkage. However, the drying shrinkage of blended cement mortar containing SF cured with water at 60 °C was lower than that of Portland cement control due to lower autogenous shrinkage and the reduced microporosity of C–S–H.     

多因素对碱激发水泥-矿渣复合粉料强度影响的研究

本文主要研究石膏、温度、水泥掺量对碱激发水泥－矿渣复合粉料强度的影响。通过变换石膏掺量、养护温湿度、水泥掺量来分析其强度变化规律。研究结果表明，掺人石膏对强度有利，当石膏掺量6％时强度最高。养护温度越高，试件的强度越高。在矿渣中加入少量的水泥，强度随水泥掺量的增多而降低。在水泥组分增加到20％时，强度有增高的趋势，并且矿渣的最大掺量应控制在80％以下。     

矿物掺合料早期水化活性的测试和分析

本文采用环境扫描电子显微镜(ESEM)和热重-差热(TG-DTA)分析仪对磨细矿渣微粉、高钙粉煤灰、低钙粉煤灰的早期水化活性进行了系统测试和分析.理论和试验结果分析表明,掺合料取代水泥时,浆体早期抗压强度的提高取决于掺合料自身参与水化反应的速度和水化产物的数量.水化产物在掺合料颗粒表面沉积的速度和浆体中硅酸盐、铝酸盐水化产物的非蒸发水量随掺合料活性的提高而提高.掺合料活性按磨细矿渣微粉、高钙粉煤灰、低钙粉煤灰的顺序降低,将磨细矿渣微粉或高钙粉煤灰与低钙粉煤灰复合,可以克服低钙粉煤灰大掺量取代水泥时混凝土早期强度降低的缺陷,这是提高低钙粉煤灰在高强高性能混凝土中掺量的一个有效措施.     

Enhancing the performance of calcium sulfoaluminate blended cements with shrinkage reducing admixture or lightweight sand

This study investigates the effect of using shrinkage reducing admixture (SRA) or lightweight sand (LWS) on enhancing the performance of calcium sulfoaluminate (CSA) cement in combination with ordinary Portland cement (OPC). Of special interest is the efficacy of the SRA or LWS in modifying the expansion/shrinkage and compressive strength characteristics of OPC-CSA systems in the absence of adequate duration of water curing, which is critical for the expansive reaction of CSA cement and its ability to mitigate shrinkage. Hydration kinetics, autogenous and drying deformation, thermogravimetry, and scanning electron microscopy (SEM) are used to evaluate the effect of SRA or LWS on the performance of the OPC-CSA systems. Test results indicate that the OPC-CSA system can exhibit similar drying shrinkage to that of the plain OPC mixture when no moist curing is applied. In the presence of LWS or SRA, the OPC-CSA systems exhibited lower shrinkage or higher extent of expansion compared to the corresponding OPC-CSA mixture alone. This is attributed to delay of the drop in internal relative humidity and promoting hydration of the OPC-CSA system which can enhance the ettringite-generating potential of CSA cement. The use of LWS was found to be highly effective in enhancing compressive strength of OPC-CSA system. SEM results at 91 days confirm the higher density and lower porosity for the paste surrounding LWS particles compared to the corresponding mixture made without LWS. In the case of inadequate moist curing, the presence of LWS or SRA is shown to enhance the overall performance of OPC-CSA system. For a given overall desirability value of 0.65 determined by multi-objective optimization, the incorporation of 1% SRA or 10% LWS was found to enable the reduction the required period of moist curing from 6 days to 5 and 3 days, respectively.