丁苯乳液改性水泥混凝土弯曲性能研究

研究了丁苯乳液掺量对混凝土压折比、最大弯曲荷载挠度、弯曲韧性系数等弯曲性能的影响以及相互之间的关系。结果显示乳液掺量由0提高至60%时,混凝土的抗弯拉强度与弯曲韧性系数呈现先提高后降低的现象;当乳液掺量为17%时,混凝土的抗弯拉强度达到最大值7.54 MPa,而当乳液掺量为19%时,混凝土的弯曲韧性系数达到2.029;混凝土最大弯曲荷载对应挠度值随乳液掺量的增加则大致呈现线性增大的变化趋势;而压折比呈现先降低后升高的变化规律,在丁苯乳液掺量为19%时达到最小值。弯曲荷载-挠度曲线特征显示改性后混凝土弯曲变形能力随乳液掺量的增加而逐渐增强,综合考虑聚合物乳液的成本,建议丁苯乳液的最佳掺量为13%~15%。经过数据归纳分析,当乳液掺量≤21%时,压折比、最大荷载挠度随弯曲韧性系数的提高而分别呈指数降低、线性增加。     

镁氯胶凝材料复合改性的研究

在对磷酸、粉煤灰分别改性研究的基础上,采取磷酸、粉煤灰及苯丙乳液对镁氯胶凝材料耐水性进行复合改性。研究结果表明,同时掺入20%粉煤灰、1%磷酸及5%苯丙乳液,可有效提高5.1.8主晶相在水中的稳定性,提高材料的密实度和抗水性能;水泥石的软化系数及早期强度均得到显著提高,分别达到0.90和48.6MPa;浸水28d抗压强度衰减较小,保持64.4MPa的高水平。综合改性效果显著。     

玻璃纤维对磷酸镁水泥砂浆力学性能的增强作用及机理

添加不同体积比的玻璃纤维,按照一定比例配制玻璃纤维增强磷酸镁水泥。研究了玻璃纤维增强磷酸镁水泥的抗压强度、抗折强度以及耐水性,并采用电镜扫描的方法对其微观结构进行了观察。研究结果表明,玻璃纤维对磷酸镁水泥的抗压强度和抗折强度都有一定贡献,其中纤维的最佳体积掺量约为2.5%,但超过最佳掺量后,抗压和抗折强度都有所降低。另外,实验结果还表明,稍过量的玻璃纤维能够暂时"包裹"未反应基材,可能在浸水环境中发生又一轮反应,从而抵消因浸水造成的强度损失,这可能是一种改善磷酸镁水泥耐水性的新方法。此外,本工作提供了与实验结果一致的纤维增强机理的可能解释。     

复合改性氯氧镁水泥泡沫混凝土耐水性能与机理的研究

在磷酸、硬脂酸钙分别改性研究的基础上,采用磷酸、硬脂酸钙、苯丙乳液改性剂对氯氧镁水泥泡沫混凝土进行复合改性。结果表明,同时掺入1%磷酸和1%硬脂酸钙,氯氧镁水泥泡沫混凝土的综合改性效果好于单掺硬脂酸钙或磷酸改性。复掺1%的苯丙乳液,氯氧镁水泥泡沫混凝土的耐水性能及抗压强度进一步提升,软化系数达到0.83,3,7 d和泡水7 d后的抗压强度分别达到1.40,1.48和1.23 MPa,接近和好于空白样,综合复合改性效果优良。     

Influence of the water to cement ratio W/C on the compressive strength of concrete — An application of the cement hydration equation to concrete

The cement hydration equation was used to determine the influence of the water to cement ratio, W/C, on the compressive strength of concrete up to the end of the hydration age. Using the hydration equation, the equations of the compressive strength of concrete were derived for five values of the ratio W/C equal to 0.50, 0.55, 0.60, 0.65, and 0.70. The curves of variation of the compressive strength versus the W/C ratio for the hydration age of 7, 28, 90 and 5475 days were drawn. Based on these curves a thorough study of the influence of the W/C ratio on the compressive strength of concrete was undertaken.     

镁水泥混凝土中钢筋的电化学腐蚀研究

为解决分布在西部盐湖地区出现的煤矿矿区钢材腐蚀问题,结合煤矿矿区实际环境,采用实验、理论分析等方法研究了镁水泥混凝土中钢筋的腐蚀.采用CS350电化学工作站,研究镁水泥混凝土中钢筋的电化学腐蚀,结合SEM微观实验和EDS元素扫描结果,对镁水泥混凝土中裸露钢筋腐蚀状况进行描述.研究表明:美加力涂层钢筋状态良好,未出现腐蚀状态;锌美特涂层钢筋出现了低腐蚀现象;而裸露钢筋表面出现了严重腐蚀.钢筋涂层防腐蚀性美加力涂层较好,锌美特涂层次之;涂层钢筋虽然防腐效果不同,但对裸露钢筋的防腐蚀性能有明显有利影响.     

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...     

氯氧镁水泥对不饱和树脂的阻燃性能与阻燃机理研究

采用极限氧指数法、热重分析和烟密度测试法研究了氯氧镁水泥在不饱和树脂（UP）中的阻燃作用和阻燃机理。研究表明经偶联剂处理后的氯氧镁水泥对UP具有良好的阻燃抑烟效果，并通过增加UP在高温下的热稳定性和降低热失重速率等机理发挥阻燃作用：氯氧镁水泥含量在40％内对UP的力学性能影响较小，是一种新型的无机添加型阻燃剂。     

氯氧镁水泥对焚烧飞灰固化作用及影响因素

利用氯氧镁水泥对飞灰进行固化处理,研究了氯氧镁水泥对飞灰重金属离子的固化效果及影响因素。结果表明,氯氧镁水泥对飞灰固化存在一个最佳摩尔比,在最佳摩尔比条件下Pb浸出浓度最低,固化率达94%;随着活性氧化镁含量上升(由28.9%提高到60.56%),Pb浸出浓度显著降低,固化率提高23.9%,当活性氧化镁含量进一步增加时,Pb浸出浓度降低幅度减小;按摩尔比为10∶1,水灰比为0.3配制氯氧镁水泥,在掺量为20%的条件下,固化效果优于掺量为40%的P·O42.5水泥,且满足生活垃圾填埋标准的限值,具有很好的应用前景。     

Effect of aluminium phosphate as admixture on oxychloride cement

The effect of admixing of aluminium phosphate on oxychloride cement in the matrix has been investigated. It is shown that aluminium phosphate retards the setting process of the cement and improves water-tightness.     

秸秆/氯氧镁水泥无机轻质复合材料制备与性能

以氯氧镁水泥（MOC）为主料,H₂O₂为发泡剂,MnO₂为激发剂,硬脂酸钙为稳泡剂,聚丙烯酰胺为增稠剂,添加稻秸秆,制备出秸秆/MOC无机轻质复合材料。探讨了秸秆尺寸和添加量对秸秆在浆料中的分散性及对秸秆/MOC复合材料力学强度、韧性、抗裂性、吸水性的影响规律。结果表明,秸秆尺寸和添加量对秸秆在浆料中的分散性、强度有较大影响,当秸秆尺寸≤ 250 μm、秸秆与MOC的质量比为0.9%时,秸秆分散性最好,制得秸秆/MOC复合材料的压缩强度（11.26 MPa）、弯曲强度（3.97 MPa）最大,抗裂性最佳。SEM分析表明,未经处理的秸秆与基体间的胶结状况差,存在弱界面层,当掺入秸秆尺寸过大或添加量过多时,秸秆/MOC复合材料中单位体积内被引入了较多的弱界面胶合部分,进而影响了复合材料的整体性能。     

磷酸/聚合物复合改善氯氧镁水泥耐水性能与机理的研究

在磷酸、聚合物单一改性的基础上,采用磷酸与苯丙乳液、硅丙乳液分别对氯氧镁水泥进行复合耐水性能改性实验。结果表明,磷酸能够提高氯氧镁水泥体系的耐水性能,但对水泥有明显的缓凝作用;苯丙、硅丙等高分子聚合物乳液对氯氧镁水泥的耐水性能没有明显的改性效果;磷酸能够促进聚合物膜在水化产物表面的粘附与覆盖,形成复合耐水保护层,适量的苯丙或硅丙乳液与磷酸复合,对氯氧镁水泥耐水性改性效果远好于单掺磷酸或聚合物,且克服了磷酸缓凝和早期强度大幅下降的缺陷。     

On the mechanical properties of polymer Portland cement concrete

Abstract

In this paper, epoxy which is the most common type of polymer used by civil engineers, and polyester, which is cheaper than most other types of polymers, were utilized to produce Polymer Portland Cement Concrete (PPCC). A rich concrete mix was designed and then five different ratios of cement (0, 20, 40, 60 and 100%) were replaced by either epoxy or polyester, rendering five different mixes for each type of polymer. Three types of samples were cast, compacted and then cured for 28 days. The three types of samples are standard beams of size 150×150×600 mm, standard cubes and standard cylinders. One third of the specimens were tested at room temperature, while the rest of the specimens were heated in an oven for 24 hours. Specimens were heated to two temperature stations of 80°C and 150°C. Samples received for flexure, compression, split tension, and direct shear tests, using a specially manufactured apparatus that was used before and found to be effective. The variations of compressive strength, split tensile strength, direct shear strength, and flexural strength with different variables such as temperature, percentage of polymer and type of polymer were determined and assessed.     

不同温度处理对磷酸镁水泥性能的影响

对磷酸镁水泥在不同温度处理下的表观形貌、体积收缩率和抗压强度进行了研究,并通过XRD、SEM对各个温度阶段的物相及微观形貌进行了分析,利用TG-DSC研究了加热过程中的质量变化和所产生的热效应。结果表明,在200℃以下,磷酸镁水泥强度减小较大;在400～800℃之间,强度变化相对较小;在更高的温度下,由于烧结现象的出现,磷酸镁水泥的强度甚至有所增长;当温度达到1400℃,磷酸镁水泥的整体结构仍然保持完整,但体积则发生了较大的收缩。磷酸镁水泥具有良好的高温稳定性。     

Compressive stress-strain model for low-calcium fly ash-based geopolymer and heat-cured Portland cement concrete

This research focuses on elucidating the present knowledge gaps in geopolymer concrete's engineering properties, specifically its stress-strain behaviour. Geopolymer concrete (GPC) is an emerging alternative to ordinary Portland cement concrete (OPCC), and is produced via a polycondensation reaction between aluminosilicate source materials and an alkaline solution. As a relatively new material, many engineering properties of geopolymer concrete are still undetermined. In this paper, the compressive strength, modulus of elasticity and stress-strain behaviour of ambient and heat-cured GPC and OPCC have been studied experimentally. A total of 195 geopolymer concrete cylinders and 210 Portland cement concrete cylinders were tested for the above mentioned characteristics. Based on the experimental results, constitutive models describing the complete stress–strain behaviour in uniaxial compression have been developed for the low-calcium fly ash-based geopolymer concrete and the heat-cured Portland cement concrete.     

引气轻集料混凝土工作性和力学性能的研究

为配制高性能轻集料混凝土,研究了优质引气剂对大流动性轻集料混凝土的工作性及力学性能的影响规律.研究表明:引气剂对大流动性轻集料混凝土的坍落度的影响不大,对黏度影响较大;引气可减少离析、泌水及坍落度损失,明显改善轻集料混凝土拌合物的工作性能;一定范围内,引气对轻集料混凝土的力学性能有益;含气量小于5.5%时,抗压强度未降低,而是有所提高,提高幅度约3%～4%;含气量小于5.5%时,抗折强度提高,提高幅度约8%～10%.     

Laboratory study of larger sized aggregate in Portland cement concrete

A laboratory examination of the effects of coarse aggregate type and size on the mechanical properties of concrete is presented, in an effort to develop more cost-efficient mixes for pavements and other highway structures. Aggregate blending is used to generate the required coarse aggregate gradations. Six different concrete mixes are prepared, using three different coarse aggregate gradations, along with two different aggregate types, natural and crushed. Test results show that coarse aggregate properties often do not have a significant effect on the mechanical properties of concrete. When significant differences are observed, these are confounded by variability issues related to the testing protocols themselves, and by mineralogical distinctions among the various aggregate blends.     

Durability of concrete incorporating high-volume of low-calcium (ASTM Class F) fly ash

Research on structural concrete incorporating high volumes of low-calcium (ASTM Class F) fly ash has been in progress at CANMET since 1985. In this type of concrete, the cement content is kept at about 150 kg/m³. The water-to-cementitious materials ratio is of the order of 0·30, and fly ash varies from 54 to 58% of the total cementitious material. A large dosage of a superplasticizer is used to achieve high workability.

This paper presents data on the durability of this new type of concrete. The durability aspects considered are: freezing and thawing cycling; resistance to chloride ion permeability; and the expansion of concrete specimens when highly reactive aggregates are used in the concrete.

The investigations performed at CANMET indicate that concrete incorporating high volumes of low-calcium fly ash has excellent durability with regard to frost action, has very low permeability to chloride ions and shows no adverse expansion when highly reactive aggregates are incorporated into the concrete.     

橡胶混凝土的抗裂性能和弯曲变形性能

通过净浆、砂浆和混凝土3 个层面的试验研究, 探讨了橡胶混凝土的抗裂性能和弯曲变形特性。根据圆环试件的开裂时间, 对3 种水灰比( 0. 3, 0. 4, 0. 5) 水泥净浆中掺入不同体积含量橡胶颗粒( 10%, 15%, 20%,30% , 50%) 后的开裂敏感性进行了对比分析。结果表明, 在水泥净浆中掺入橡胶颗粒可以显著延缓试件的开裂时间, 提高抗裂性, 延缓时间随着橡胶颗粒掺量的增加和水灰比的增大而延长。弯曲试验考察了4 个橡胶颗粒体积含量( 8%, 16%, 21. 4%, 32%) 砂浆试件和3 个橡胶颗粒体积含量( 10%, 12. 5%, 15%) 混凝土试件的弯曲变形性能。结果表明, 含橡胶颗粒的砂浆试件和混凝土试件在弯曲过程中会产生明显的塑性变形, 试件不会在承受最大荷载时产生脆性断裂, 而是经过较大的塑性变形后延性破坏。与基准试件相比, 砂浆试件和混凝土试件破坏时的极限变形值均有大幅度提高。      

基于EIS研究镁水泥混凝土中涂层钢筋的耐腐蚀性

通过模拟室内自然状态、氯化镁溶液和水三种工作环境,采用CS350电化学工作站,结合理论与试验分析,对镁水泥混凝土涂层钢筋的交流阻抗谱进行研究。结果表明:通过对交流阻抗谱和涂层电阻的表征分析得出该涂层可以很好地保护镁水泥混凝土中的钢筋免受腐蚀。不同的混凝土保护层厚度对同时期的涂层电阻有一定的影响,涂层电阻的大小随保护层厚度增加而增加。从而得出该涂层对镁水泥钢筋混凝土中的钢筋起到很好的保护作用,进而解决镁水泥钢筋混凝土在盐渍土地区应用易受侵蚀的问题。