微生物水泥基材料抗冻性和抗冲刷性

利用微生物水泥成功胶结高为50 cm,直径为5 cm的圆柱体砂柱。分别对其距离注射口不同位置处的砂柱进行抗压强度、冻融循环以及冲刷性实验。实验结果表明,微生物水泥砂柱随着远离菌液注射口,其抗压强度不断降低;微生物水泥胶结距离注射口0~30 cm处的砂柱抗冻性好,而超过30 cm,则抗冻性较差;微生物水泥胶结的50 cm高砂柱经0.5 h冲刷后,其不同部位均具有较好抗冲刷性。     

碳纳米管对水泥基材料热膨胀性能的影响

在水泥基中掺入不同比例的碳纳米管,制备出碳纳米管水泥基复合材料。测量其在室温~600℃的热膨胀性能,并根据DSC/TG、XRD图谱,孔径分布图和扫描电镜图从微观尺度分析其变化规律的机理。结果表明,从室温到150℃掺入各比例碳纳米管的水泥基复合材料热膨胀率变化趋势相似,热膨胀率为正值而出现微膨胀;150℃~590℃热膨胀率为负值且逐渐减小,试件持续收缩。当碳纳米管的掺量为水泥的0.3%时热膨胀曲线始终在其他掺量之下,热膨胀率达到最小值。这表明,碳纳米管掺量为0.3%的材料水化反应充分,产生大量的水化硅酸钙凝胶,收缩明显、密实度显著提高。掺入0.3%的碳纳米管可有效阻止供暖管道局部混凝土的膨胀,提高结构的耐久性。     

高稳定性超疏水水泥基材料涂层制备及性能研究

通过改性铜网复刻和SiO₂相结合共同作用构建水泥基材料微纳米粗糙表面,并采用十八胺接枝腐殖酸作为低表面能物质修饰该表面制备出高稳定性超疏水水泥基材料涂层。研究了涂层中掺入不同浓度SiO₂及改性铜网复刻对其疏水性能的影响,并测定出SiO₂掺入最佳浓度。此外,利用扫描电子显微镜(SEM)、X射线衍射(XRD)和傅里叶红外光谱仪(FT-IR)等对水泥基材料表面形貌结构及键合情况进行了表征,同时对超疏水水泥基材料的吸水性和涂层稳定性进行综合评估。结果表明,当SiO₂浓度为2.5%时,采用浸渍法处理改性铜网复刻过的水泥基材料表面接触角达到峰值158.6°,滚动角低至5.5°;吸水量下降73.5%。此后,经过反复30次胶带剥离表面测试以及刀刮测试涂层仍保持超疏水状态(接触角为150.2°,滚动角为8.2°),证实了该方法处理的涂层表面具有超疏水性以及良好的稳定性。     

碳基材料对水泥基材料性能的影响

水泥基复合材料凭借其原料丰富、价格低廉、生产工艺简单、强度高等优点,广泛应用于现代化工程建设.但是这种材料长久以来都有高脆性以及裂缝等一系列的问题.针对这些问题世界各国的研究人员都主要致力于改善水泥基材料的力学性能.但是在目前的情况下,现代建筑对水泥基材料提出了许多新的要求,不仅要有好的力学行为,还要具有尽可能多的附加功能.合适的功能填料的掺入不仅能够使得水泥基复合材料的力学性能和耐久性能得到提升,还能有效地调控水泥基材料的导电率、热导率等一系列其他功能.钢纤维、聚合物纤维和矿物纤维等是之前比较常见的功能掺料,这些材料依靠它们的强度和韧性可以用来改善材料的力学性能.但这些增强材料并不能在结构上改变水泥的水化产物,因此水泥基材料的高脆性及裂缝等问题依存在.而部分碳基材料在掺入到水泥基复合材料中以后可以对水泥基材料实现改性,不仅能从微观方面改变其结构,从而改善力学性能,还可以改善如导电性、导热性等性能.使水泥基复合材料能够尽可能地满足时代的要求.本文在近年来对多种不同的碳基材料掺杂水泥基复合材料研究的基础上,分别总结了不同碳基材料(碳纤维CF、碳黑CB、碳纳米管CNTs、石墨烯GR以及氧化石墨烯GO)对水泥基复合材料性能影响的基本原理,综述了近年来五种材料掺加在水泥基复合材料中的相关研究.此外,本文同时也对这些材料的复合掺入以及互相之间的改性掺入后的效果进行了简单总结,并且同时对水泥基复合材料的研究前景提出了一点看法.     

超细粉体对水泥基材料力学性能的影响

为了研究超细粉体在水泥基材料中的应用,对掺加不同活性超细粉体的水泥基试件进行了抗压强度和抗折强度的测试,讨论了矿粉A掺量、硅粉掺量、复掺矿粉A和硅粉对水泥基材料力学性能的影响。结论表明:活性超细粉体对水泥基试件的抗折和抗压强度有较大影响,尤其是硅粉能够很好地提高试件的抗折强度和抗压强度。通过SEM形貌分析,说明掺加的超细粉体能够与水泥基材料内部的不利成分Ca(OH)2发生二次水化反应,生成有利的C-S-H凝胶,有效改善水泥基材料的微观结构。     

水灰比对轻质水泥基泡沫材料性能的影响

通过物理引气法制备轻质水泥基泡沫材料,研究了水灰比对材料孔隙率、强度、导热系数及孔结构的影响。结果表明,孔隙率随着水灰比的增大而增大,但孔结构在水灰比大于0.9时劣化明显。材料抗压强度和导热系数受孔隙率和孔结构的综合影响。当水灰比由0.75增大至0.9时,"强度/表观密度"降低9.6%,导热系数减小25.6%。但当水灰比由0.9增大至0.95时,"强度/表观密度"降低幅度达到了18.5%,导热系数非但没有减小而是略有增大。通过SEM和Young-Laplace方程分析了水灰比对孔结构的影响规律,阐明了水灰比对水泥基泡沫材料性能的影响机理。     

微生物水泥基材料的红外光谱研究

微生物水泥是在节能减排大环境下而研发的一种新型生物水泥。利用X射线衍射(XRD)、透射电镜(TEM)和红外光谱(IR)分别对微生物水泥基材料的成分、形貌、微观结构进行了研究。TEM分析表明,微生物水泥基材料内部微观结构与化学法浇注的砂颗粒内部微观结构不同。微生物矿化形成的方解石可以胶结松散颗粒,而化学法形成的方解石与松散颗粒之间存在孔隙,不能胶结松散颗粒;IR分析表明,微生物水泥基材料中的Si—O键和C—O键频率均发生红移,而化学法浇注的砂颗粒中Si—O键和C—O键频率未发生改变,另外,化学法浇注的砂颗粒中Si—O键与单纯石英砂中的Si—O键频率相同。     

水泥基材料微结构演变及其传输性能的数值模拟

水泥基材料劣化的本质是由于侵蚀性介质通过传输通道进入材料内部生成腐蚀物质,从而对结构造成破坏.因此,结构耐久性与侵蚀介质在水泥基材料中的传输行为密切相关.已有的混凝土寿命预测模型和耐久性评估研究主要基于Fick和Darcy定律,本文从水泥基材料微结构出发,结合最新的国内外研究成果,对孔结构演变及其传输性能的数值模拟研究进展进行阐述,对促进结构耐久性的研究具有一定的指导意义.     

水泥品种对水泥基材料热膨胀性能影响的研究

针对不同品种水泥基材料在高温下体积稳定性问题,采用差示热膨胀仪对普通硅酸盐水泥、高铝水泥和硫铝酸盐水泥分别制成的水泥石的热膨胀性能进行了测试,并用DTA/TG对影响水泥石高温热性能的原因和机制进行了分析。结果表明:3种水泥石的热膨胀率均随着温度的升高先增加后显著降低,到达一定温度后趋于稳定。分析热膨胀随温度变化的规律获知,3种水泥在高温状态下应用时,高铝水泥体积稳定性最佳、硫铝酸盐水泥次之、普通硅酸盐水泥石最差。水泥石的热膨胀均是由其固相组分的受热膨胀与主要水化产物的脱水收缩共同作用的结果,而水泥品种不同,其水化产物中主要脱水组分截然不同。     

碳纳米管-碳纤维/水泥基材料微观结构和热电性能

研究了碳纳米管-碳纤维/水泥基材料的微观结构以及碳纳米管-碳纤维/水泥基材料升温与降温过程中的热电性能。实验结果表明,当水泥基材料中碳纳米管掺量较低时(碳纳米管掺量占水泥质量百分比不高于0.5%),碳纳米管能有效改善水泥基体性能,密实基体结构。在碳纤维水泥基材料中掺入碳纳米管能有效提高和改善复合材料热电性能;当碳纳米管掺量为水泥质量0.5%,水泥基材料热电势率最多能提高260%,达到22.6μV/℃。与此同时,碳纳米管掺入能增强热电效应中温差电动势与温差关系的线性规律和可逆性规律。     

无机胶凝成型活性炭的制备及性能研究

用水泥熟料作胶凝剂,探讨粉末活性炭的成型及性能。通过引入硅微粉与采取蒸压养护措施提高材料强度、缩短制备周期;用扫描电子显微镜(SEM)观察微观形貌,用抗压强度、碘吸附值、气孔率、吸水率、含炭量等指标评价试样的综合性能。研究结果表明,将70%(质量分数)活性炭粉末、25%(质量分数)水泥熟料粉末与5%(质量分数)硅微粉充分混合均匀后,造粒、成型,在195℃蒸压釜中养护6h,可制得性能良好的无机胶凝成型活性炭材料;试样的物理性能:碘吸附值为551.72mg/g,抗压强度为7.25MPa,炭含量为58.48%,气孔率为57.34%,吸水率为69.42%。     

硫铝酸盐水泥基胶凝材料的改性研究

根据结晶诱导、超细粉体、化学激发等效应,通过抗压强度测试、XRD、热重、SEM等分析手段对大掺量粉煤灰的硫铝酸盐水泥进行了研究。实验结果表明,引入增强组分M后,试块2h、3,7,28d最高抗压强度分别提高了140%,116%,80%和60%;钙矾石及铝胶生成量增多,体系变的更致密,2h就能达很高强度;M的引入,可能使钙矾石初始结晶度变差;随养护龄期的延长,钙矾石结晶度逐渐变好,M促使粉煤灰参与后续水化反应,使粉煤灰颗粒被水化物紧密包裹,体系变得更致密,试块后期强度变大。     

Influence of preparation method on the performance of ternary blended cements

This paper examined the feasibility of preparing high performance gap-graded blended cements by adding fine and coarse supplementary cementitious material (SCM) fractions into commercial Portland cement, and the efficiency of SCMs in gap-graded blended cements and interground blended cements were comparatively evaluated. The results show that the particle size distribution of gap-graded blended cements was much closer to a Fuller distribution, due to the intentional addition of fine and coarse SCMs, resulting in a higher initial packing density. As granulated blast furnace slag (GBFS) was mainly arranged in the fine fraction of the gap-graded blended cements, its efficiency was increased dramatically, contributing to 43.5% of the total measured hydration products. As a result, gap-graded blended cement pastes presented a homogeneous and dense microstructure due to “grain size refinement” and “pore size refinement”, therefore their setting times were decreased significantly, and both early and late strengths were increased remarkably in comparison to the interground blended cements investigated in this study.     

Developing high performance phosphogypsum-based cementitious materials for oil-well cementing through a step-by-step optimization method

In the present study, unprocessed phosphogypsum (PG), a byproduct generated by the phosphorus fertilizer industry, is mixed with conventional oil-well cement (CM) and ground-granulated blast-furnace slag (GGBFS or SG), along with other activators and admixtures (such as silica fume (SF), retarder (USZ), and fluid loss control additive (BXF200-L)), to form a PGS slurry for oil well cementing. The mix proportion was optimized step-by-step according to the key properties of hardened PGS slurry, such as compressive strength, linear expansion, porosity, and permeability. The results indicate that the optimized PGS slurry (PGS-optimal slurry), made with the neat PGS:SF:USZ:BXF200-L (by weight) = 100:6:0.4:2, w/c = 0.44, where the neat PGS is consisting of a ratio of PG:SG:CM = 50:20:30 (by weight), had met major technical requirements for oil well cementing operation. Advantageous over the hardened CM slurry, the hardened PGS-optimal slurry generates significant expansion during hydration, thus providing the hardened slurry with excellent shrinkage compensation capability. The hardened PGS-optimal slurry has lower porosity, especially lower amount of harmful pores (>100 nm), than the hardened CM slurry. Consequently, the hardened PGS-optimal slurry also displays much lower permeability.     

石粉对水泥-矿粉混凝土性能的影响

本文主要研究了石粉对水泥-矿粉混凝土的工作性、抗压强度、耐久性能(抗渗性能、抗碳化性能和抗冻性能)的影响,并利用孔结构微观分析对其进行了机理分析。研究表明:石粉应用于水泥-矿粉混凝土中,不仅可改善混凝土的工作性能,而且可提高混凝土的抗压强度,对混凝土的耐久性能(抗渗性能、抗碳化性能和抗冻性能)影响不大。     

含涤废弃织物增强水泥基透水砖的制备及表征

采用涤棉混纺(P/C)和涤纶(PE)废弃织物增强水泥基透水混凝土砖,分析织物含量和织物尺寸等因素对复合透水砖(CPB)抗压性能、透水性和保水性的影响。结果表明:随着织物掺加体积分数的增加,CPB的抗压强度、压缩韧性指数和所消耗能量先增大后减小,透水系数和保水系数增加;随着织物尺寸增大,CPB的抗压强度、透水系数和保水系数逐渐减小,压缩韧性指数增加,耗能变化幅度不大;在织物和纤维掺加量较小且掺加质量相同的条件下,与废弃织物CPB相比,再生纤维CPB的抗压强度较小,而压缩韧性指数、耗能和透水系数较大;当织物掺加体积分数≤2%时,涤棉复合透水砖(PC-CPB)的抗压强度优于涤纶复合透水砖(P-CPB),透水系数、保水系数和P-CPB接近,当织物掺加体积分数>2%时则相反,而PC-CPB的压缩韧性指数和耗能始终优于P-CPB;织物掺加体积分数为2%的3 mm×3 mm P/C织物所制备的CPB抗压强度为28.20 MPa,耗能为1097.55 N·m,透水系数为0.267 mm/s,保水系数为43.40 g/cm2,与普通透水砖相比,分别提高了21.8%、55.8%、115.3%和33.3%。      

Self-healing performance of aged cementitious composites

This study investigates the autogenous self-healing capability of one-year-old engineered cementitious composites (ECC) with different mineral admixtures to understand whether self-healing performance in late ages is similar to that of early ages. Sound and severely pre-cracked specimens were subjected to different environmental conditions including water, air, “CO₂-water,” and “CO₂-air” for one year plus 90 days of initial curing. Self-healing performance of ECC mixtures was assessed in terms of crack characteristics, electrical impedance testing, rapid chloride permeability testing and microstructural analysis. Laboratory findings showed that the presence of water is crucial for enhanced autogenous self-healing effectiveness, regardless of mixture composition. “CO₂-water” curing resulted in the best self-healing performance of all curing conditions, which was confirmed with results from different performance tests throughout the experimental study. By further curing specimens under “CO₂-water” (depending on the ECC mixture composition), cracks as wide as half a millimeter (458 μm) were easily closed by autogenous self-healing within only 30 days of further curing, and all cracks closed completely after 90 days. Because high levels of CO₂ emission are a global problem, the effectiveness of “CO₂-water” curing in closing microcracks of aged cementitious composites specimens through autogenous self-healing can help reduce the increasing pace of CO₂ release. The results of this study clearly suggest that late-age autogenous self-healing rates of ECC specimens can be significantly enhanced with proper further environmental conditioning and mixture design.     

亲水型功能化石墨烯的分散性及其对水泥基复合材料力学性能的影响

为了解决石墨烯纳米片在水泥基体中的分散问题,采用芳基重氮盐(F)对氧化石墨烯(GO)进行改性,制备了一种新型亲水型功能化石墨烯(FG).结果表明,FG在水溶剂中最大的分散浓度能够达到2.1mg/mL.FTIR、拉曼光谱和XPS结果表明F成功对石墨烯进行了表面改性.对比纯水泥基体材料,本文所制备的亲水型FG/水泥复合材料...     

Production of quasi-sulfoaluminate cementitious materials with electrolytic manganese residue

Electrolytic manganese residue (EMR) is a harmful solid industrial waste that comes from the electrolytic manganese industry and has rarely been recycled in large quantities. To consume as much EMR as possible, quasi-sulfoaluminate cementitious material (Q-SAC) was prepared by firing high amounts of EMR together with limestone and kaolin at approximately 1200 °C (∼50-100 °C lower than that of ordinary sulfoaluminate cement). The major crystalline phases of Q-SAC determined by XRD were calcium sulfoaluminate, dicalcium silicate and calcium sulfate. The final setting times of Q-SAC were less than half an hour. The early and long-term alkalinities of Q-SAC pastes were approximately 2 and 1 lower than those of OPC paste, respectively. The results also showed that Q-SAC prepared by mixing 10-40% of EMR can obtain compressive strength of 35-65 MPa at 56 days. When 5% of gypsum was added, the early and long-term strengths of Q-SAC were approximately 50% and 30% higher, respectively. The results showed that the use of EMR for Q-SAC production is a promising way to recycle EMR because of its low firing temperature and good mechanical performance.     

Properties of mortars produced with reactivated cementitious materials

The production of reactivated cementitious materials is an option for the recycling of hydrated-cement-rich fines discarded during recycled aggregate production. Reactivation is based on a thermal process where calcium silicate hydrates present in the fines decompose forming new hydraulic compounds. In the reported study, materials reactivated at temperatures between 660 °C and 940 °C were characterized using X-Ray diffraction and particle size analysis, and evaluated as binders using a central composite experiment to model the effects of reactivation temperature and reactivated material substitution level on the flowability, compressive strength and expansion of mortar mixtures. Reactivation temperature effects correlated with the relative concentration of reactive phases, particularly a stabilized form of alpha'-C₂S identified in the materials. Substitution effects depended on the supplementary material tested, and lacked significant interaction with reactivation temperature. In the region explored, mortars based on materials produced at 800 °C, 40% substituted by silica fume, achieved highest strength but lowest flowability.