水泥细度对早龄期碾压混凝土综合抗裂性的影响(英文)

水泥水化热与比表面积和化学组成有关,但是相对于调整水泥的化学组成来说,通过减小水泥的比表面积来降低水泥水化热要容易得多。为了探索水泥比表面积与碾压混凝土抗裂性能的关系,采用相同熟料磨制了3种细度的水泥,研究了水泥细度对水化热、胶砂强度的影响,以及对混凝土的工作性、力学性能(抗压强度、抗拉强度和抗拉弹性模量)、极限拉伸值、绝热温升等性能的影响;同时,采用温度–应力试验机,评估了在100%约束和近似绝热条件下水泥细度对早龄期碾压混凝土综合抗裂性能的影响。结果表明:水化热与比表面积成线性关系,降低水泥比表面积是降低混凝土温升的有效、便捷的措施;粗磨水泥提高了碾压混凝土的工作性,降低了混凝土的抗压强度和弹性模量,但混凝土极限拉伸值没有明显变化;温度–应力试验表明,随着水泥比表面积的降低,混凝土第二零应力温度更低,粗磨水泥碾压混凝土综合抗裂风险更低。     

The effect of grinding process on mechanical properties and alkali–silica reaction resistance of fly ash incorporated cement mortars

The effect of fineness of fly ash on mechanical properties and alkali–silica reaction resistance of cement mortar mixtures incorporating fly ash has been investigated within the scope of this study. Blaine fineness of fly ash has been increased to 907 m²/kg from its original 290 m²/kg value by a ball mill. Test samples were prepared by replacing cement 20, 40 and 60%, with finer and coarser fly ashes and kept under standard and steam curing conditions until testing. Test results showed that grinding process improved the mechanical properties of all samples significantly. The beneficial effect of grinding fly ash, may increase utilization of this by-product in precast and ready-mix concrete industries. Incorporation of fly ash with different fineness values and ratios also decreased the expansions to harmless levels of cement mortars due to alkali–silica reaction.     

不同细度超细粉煤灰对砂浆及混凝土性能影响的研究

研究了经超细粉磨制备的三种不同细度的超细粉煤灰的基本性能,以及掺入这三种不同细度超细粉煤灰的水泥胶砂和混凝土试样的力学性能和混凝土拌合物的工作性能。结果表明,超细粉煤灰的活性随其细度的增加而提高。掺入超细粉煤灰可以有效改善混凝土拌合物的工作性能、胶砂试件和混凝土试件的力学性能,且超细粉煤灰的细度越细改善作用越明显。不使用硅灰,仅用超细粉煤灰和减水剂也可以配制出C80的高强混凝土。微观孔结构分析表明,掺入平均粒径为4μm的超细粉煤灰的混凝土小于20 nm的无害孔的孔体积明显大于掺入其他两种超细粉煤灰（2μm、6μm）的混凝土,这与CUFA4试样力学性能最佳的宏观试验结果一致。     

可再分散乳胶粉对水泥砂浆的改性作用

特细砂水泥砂浆一般都存在和易性差、抗裂性能低等缺陷,而可再分散乳胶粉具有改善水泥砂浆各项性能的优点.本文对可再分散乳胶粉对特细砂水泥砂浆的和易性、抗裂性、抗渗性以及粘结性等的影响进行研究,结果表明,可再分散乳胶粉掺量达到1.5％时,特细砂水泥砂浆的压折比最低达到2.49,此时粘结强度和抗裂强度的增加量分别达到49％和84％.     

苯丙乳液改性水泥修补砂浆的制备与性能研究

采用复配技术制备苯丙乳液改性水泥修补砂浆,并进行性能研究.探讨了聚合物乳液、偏高岭土、煅烧膨润土等外加剂对该砂浆物理性能的影响.结果表明:苯丙乳液的掺入虽然在一定程度上降低了砂浆的抗压强度,但显著改善了水泥砂浆的和易性和需水量.通过掺加偏高岭土或煅烧膨润土等火山灰活性掺合料可弥补砂浆力学性能的不足.     

Superplasticized portland cement: production and compressive strength of mortars and concrete

This paper deals with the effect of intergrinding different percentages of a naphthalene-based superplasticizer with Portland cement clinker and gypsum on the fineness of the product, and on the water requirement and the compressive strength of the mortars made with the superplasticized cement. The properties of the fresh and hardened concrete made with the superplasticized cements were also investigated. The results showed that the intergrinding of a given amount of a naphthalene-based superplasticizer with Portland clinker and gypsum reduced the grinding time required for obtaining the same Blaine fineness as that of the control Portland cement without the superplasticizer. The water requirement of the mortars made with the superplasticized cements was similar to that of the mortars made with the control Portland cements when the same amount of the superplasticizer was added at the mortar mixer; for a given grinding time and a Blaine fineness of 4500 cm²/g, the mortars made with the superplasticized cement had higher compressive strength than those made with the control Portland cement. For a given grinding time or Blaine fineness of cement ≥5000 cm²/g, the slump loss, air content stability, bleeding, autogenous temperature rise, setting times, and compressive strength of the concrete made with the superplasticized cements were generally comparable to those of the concrete made with the control Portland cements when the superplasticizer was added at the concrete mixer.     

磨细矿渣对高性能混凝土性能的影响1掺加磨细矿渣的砂浆试验

研究了矿渣的细度、掺量对水泥砂浆的强度和流动性的影响。结果表明：矿渣细度较小时,抗压强度随着掺量的增加而下降。当细度变大,强度随着掺量增加而下降的趋势变缓。细度超过一定值后,强度随着掺量的增加呈现上升趋势。同时,细度、掺量对早期（３ ｄ、７ ｄ）强度和后期（２８ ｄ）强度的影响也有差别。细度低于 ８００ ｍ ２ ／ｋｇ 的矿渣对砂浆的流动性影响不大,但细度高于 ８００ ｍ ２ ／ｋｇ的超细矿渣能够显著降低用水量。试验结果为研究矿渣在高性能混凝土中的应用提供了依据。     

Effect of Blaine fineness of recycling brick powder replacing cementitious materials in self compacting mortar

The present study aims to investigate the use of recycling brick powder (RBP) as a fractional replacement of cement in self compacting mortar. Cement was replaced by recycling brick powder in different proportions (0, 5, 10, 15 and 20%) by weight of cement. Three Blaine fineness (SSB) were used in this study (3900, 4300, and 5200 cm²/g). The experimental results showed that the substitution of cement by recycling brick powder with higher content (20%) decreases the workability of self compacting mortar (about 3%) and reduces its passing ability (about 30%). On the other hand, the increase of Blaine fineness of (RBP) led to improve the Fresh behaviour of mortars when the content of recycling brick powder kept constant. Mechanical performances of mortars in terms of compressive and tensile strength were improved by 13 and 105% respectively. Economically, the substitution of cement with 10% of brick powder gives a win of 10% of cement with an increase of 13% in compressive strength and 107% in tensile strength.     

基于不同粒径分布的低熟料矿渣水泥水化特征和孔结构特性

低熟料矿渣水泥(LSC)是一种水泥熟料用量低,主要由粒化高炉矿渣和石膏组成的水硬性胶凝材料.本文研究水泥不同粒径分布(对应比表面积分别为358 m2/kg、450 m2/kg和516 m2/kg)对低熟料矿渣水泥的抗压强度、电阻率和水化热、水化产物、孔结构的影响.结果表明,当比表面积从358 m2/kg增加到450 m2/kg可以提高低熟料矿渣水泥浆体的抗压强度,当从450 m2/kg增加至516 m2/kg时,强度提高甚微.低熟料矿渣水泥主要的水化产物是钙矾石和水化硅酸钙,增加水泥细度导致放热速率明显加快,电阻率变化曲线的下降段持续时间明显缩短,因而会产生更多的钙矾石.水泥细度增加,浆体的凝胶孔的体积分数增大,大孔减少,进一步提高浆体的密实度.     

助磨剂在钢渣复合水泥中的应用

研究通过掺加助磨剂粉磨钢渣的方法,提高钢渣微粉的细度和活性,达到高效利用钢渣目的.结果表明,随着钢渣掺量的增加,钢渣复合水泥的抗折强度呈先上升后下降趋势,掺量为30％时抗折强度最高.钢渣复合水泥的28 d抗压强度直线下降,3 d抗压强度先增加后再下降,30％掺量时强度最高,达4.75 MPa.结合实际经济效益,最终确定钢渣复合水泥的配比为熟料-65％、钢渣-30％、石膏-5％,助磨剂A掺量为0.1％时效果最好,相比无助磨剂的钢渣复合水泥,细度降低了49.0％,且28 d抗压强度提高了6 MPa.     

煤矸石机制砂细度模数对胶砂性能影响研究

为了将煤矸石作为机制砂合理应用,使用煤矸石机制砂,研究了煤矸石机制砂的基本性质,设计了两种水胶比,配制了8个细度模数,研究了不同水胶比下煤矸石机制砂的细度模数对胶砂性能的影响.研究表明:水灰比较低时,煤矸石机制砂的各项性能都相较于较高的水灰比都更好,尤其是在抗压强度方面.水灰比相同时,细度模数为2.7和2.8时胶砂的各...     

磷石膏粒径对湿拌砂浆性能及微观结构的影响研究

选取四种不同粒径磷石膏,分别与机制砂、水泥及外加剂混合制备了湿拌砂浆,考察了磷石膏粒径对砂浆工作性及力学性能的影响,并通过XRD、TG-DSC、MIP以及SEM测试探究了磷石膏粒径对湿拌砂浆水化产物及微观结构的影响机理。结果表明,随着磷石膏粒径增大,湿拌砂浆工作性及力学性能呈先增大后减小的趋势,当掺入30%(质量分数)粒径为53~106 μm的磷石膏时,湿拌砂浆稠度损失19%,保水率为90%,28 d抗压强度为10.7 MPa,14 d拉伸黏结强度为0.25 MPa,可满足抗压强度大于10 MPa的技术指标要求。随着磷石膏粒径增大,磷石膏中的共晶磷含量减少,水泥水化过程受抑制程度减弱,砂浆中水化硅酸钙(C-S-H)生成量增多,且在远离CaSO₄·2H₂O颗粒的区域有大量C-S-H出现。然而,砂浆硬化体的孔体积却呈先减小后增大的趋势,当掺入30%(质量分数)粒径为53~106 μm的磷石膏时,砂浆的孔体积最小,仅为0.130 9 mL/g。磷石膏粒径范围适宜控制在53~106 μm,此时湿拌砂浆具有良好的工作性及力学性能。     

少熟料磷渣水泥的研究

试验研究了少熟料磷渣水泥强度的影响因素,结果表明,复合外加剂四组分Ｎ、Ｇ,Ｓ,Ｆ的配比为３：４：５：４时,对少熟料磷渣水泥的抗压强度最有利,生产该水泥的适宜工艺参数为：外加剂掺量１２％￣１４％,水泥细度４００ｍ＾２／ｋｇ。混合粉磨有利于外加剂的均匀分散,从而有利于水泥强度的提高。测试了少熟料磷渣水泥的物理力学性能,孔结构性能,干缩性能和抗侵蚀性能,并与硅酸盐水泥进行了相应的对比。     

Properties of lightweight expanded polystyrene concrete reinforced with steel fiber

Expanded polystyrene (EPS) concrete is a lightweight, low strength material with good energy-absorbing characteristics. However, due to the light weight of EPS beads and their hydrophobic surface, EPS concrete is prone to segregation during casting, which results in poor workability and lower strength. In this study, a premix method similar to the ‘sand-wrapping’ technique was utilized to make EPS concrete. Its mechanical properties were investigated as well. The research showed that EPS concrete with a density of 800-1800 kg/m³ and a compressive strength of 10-25 MPa can be made by partially replacing coarse and fine aggregate by EPS beads. Fine silica fume greatly improved the bond between the EPS beads and cement paste and increased the compressive strength of EPS concrete. In addition, adding steel fiber significantly improved the drying shrinkage.     

矿物掺合料细度对水泥胶砂力学性能的火山灰效应

通过分析单掺矿粉、单掺不同磨细程度的粉煤灰及复掺粉煤灰和矿粉的胶砂早期强度的变化规律,得出粉煤灰的磨细程度及粉煤灰与矿粉的复掺比例会影响胶砂的早期强度。粉煤灰越细,越有利于提高胶砂早期强度,复合掺合料之间各成分的最佳配合比可以充分发挥各自的活性,从而提高胶砂早期力学性能。     

粉煤灰和矿渣微粉在水泥基材料中的复合效应研究

通过测定不同龄期的水泥净浆、砂浆和混凝土的力学强度以及水泥净浆的抗模拟酸雨侵蚀性能，探讨了在矿物掺合料总量为胶凝材料总量的40％时，单掺粉煤灰、单掺矿渣微粉以及粉煤灰与矿渣微粉双掺对水泥基材料性能的影响。试验结果表明：在本试验条件下，与基准试件相比，矿物掺合料的掺入可以显著改善水泥基材料的工作性能，但是在一定程度上会导致其力学性能的降低；同时双掺可以发挥出明显的“叠加效应”，但是“超叠加效应”不显著.     

助磨介质作用下旋窑熟料微细化过程及其效果评价

通过对助磨介质作用下不同粉磨细度的旋窑熟料所配制的硅酸盐水泥的物理性能检测,对助磨介质作用下旋窑熟料的微细化效果进行了评价。结果表明,对水泥熟料来说,早期的快速水化不一定能得到高强度的水泥,因此熟料微细化的评价要从水化性能和粉磨能耗上综合考虑,在实验中,旋窑熟料的最佳粉磨细度为5 000m2/g,而加入助磨剂可显著降低粉磨能耗,在达到同样效果时缩短25％的粉磨时间。     

掺粉煤灰水泥胶砂的正交试验研究

采用正交试验方法,研究了粉煤灰掺量、细度和Na2SO4掺量对水泥胶砂试块抗折、抗压强度影响规律。结果表明:粉煤灰掺量对水泥胶砂试块的7d抗折、抗压强度影响最显著;粉煤灰掺量和粉煤灰细度对28d抗折、抗压强度影响都比较显著;而Na2SO4掺量对7、28d抗折、抗压强度影响不大。     

不同细度水泥的水化特性及其对水泥砂浆自愈合性能的影响

研究了不同细度水泥的水化热、水化产物和力学性能,以及水泥细度和养护条件对预制裂缝的水泥砂浆强度恢复率和裂缝愈合的影响.结果表明:随着水泥比表面积增大,水泥水化放热量峰值越高,相同龄期下的水化程度越高;预制裂缝试块在自然养护、标准养护和水中养护90 d后的强度恢复率呈现出来相似的规律,均随着细度增加而逐渐减小;比表面积为254 m2/kg和407 m2/kg的水泥制成的砂浆试块,预制裂缝的初始最大宽度都为0.070 mm,前者水中养护90 d后裂缝基本愈合;而后者的裂缝愈合率只有57.1%.     

无氯复合助磨剂对复合水泥性能的影响

复配了4种无氯复合水泥助磨剂,研究了它们对复合水泥粉磨的助磨作用及其对水泥标准稠度用水量、凝结时间、胶砂强度等各项性能的影响。结果表明:该系列复合助磨剂提高了水泥比表面积,降低了45μm筛余值;不含Cl-,对水泥的性能无损害,且能提高水泥胶砂强度。其中,当FZ5以水泥质量0.1%掺加到熟料中,水泥3d、28d抗压强度分别提高32.2%和24.5%,使配制的混凝土强度提高了一个等级。