固体废弃物对水泥基饰面砂浆性能的影响

采用正交分析法研究了矿粉、钢渣粉和脱硫石膏(FGD)等固体废弃物对饰面砂浆性能的影响。在满足JC/T1024-2007《墙体饰面砂浆》标准的要求下,固体废弃物可以取代50%以上的水泥,减少泛碱源。最佳正交配比为矿粉、钢渣粉和脱硫石膏分别取代水泥用量的40%、10%和8%,制备出的饰面砂浆的抗折抗压强度、拉伸粘接强度、吸水量及抗泛碱性均较好。     

Durability performance potential and strength of blended Portland limestone cement concrete

This paper describes a study on the durability potential and strength of composite Portland-limestone cement (PLC) concrete mixtures blended with ground granulated blast furnace slag (GGBS) and/or fly ash (FA). Their performance was compared against ordinary Portland cement, plain PLC and Portland-slag cement concrete mixtures. Using the South African Durability Index approach, results indicate reductions in the penetrability of the composite PLC blends compared to the other mixtures. The durability indicators are chloride conductivity, gas (oxygen) permeability and water sorptivity. Compressive strength of the composite PLC mixtures containing both GGBS and FA showed competitive performance with the comparative mixtures, but FA blended PLC mixtures had diminished compressive strength values. The paper also presents considerations on the practical implications of using blended PLC concrete mixtures.     

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。     

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。     

Behavior of self compacting concrete containing ladle furnace slag and steel fiber reinforcement

Self compacting concrete mixtures with the use of ladle furnace slag as filler and steel fibers as reinforcement were produced and tested in the laboratory. Different contents of ladle furnace slag filler, ranging from 60 to 120 kg/m³, and steel fibers, ranging from 0% to 0.7%, were used. The different mixtures were tested in the fresh state for fluidity, passing ability and resistance to segregation and in the hardened state for compressive strength, fracture toughness, freeze-thawing resistance and chloride penetration resistance. The test results showed that ladle furnace slag can be used as filler for self compacting concrete, as adequate consistency and workability was achieved, while compressive strength and durability were improved. Ladle furnace slag can also be combined with steel fibers, which considerably increase fracture toughness, in order to produce a high performance self compacting concrete using a low-cost industrial by-product such as ladle furnace slag.     

碱矿渣陶粒混凝土砌块砌体受压本构关系

为考察碱矿渣陶粒混凝土砌块砌体的受压本构关系及基本力学性能,完成了126个用碱矿渣陶砂砂浆和碱矿渣陶粒混凝土砌块砌筑的砌体试件的轴心抗压试验。研究结果表明:当砌块抗压强度和砌筑砂浆抗压强度相同时,由于碱矿渣陶砂砂浆收缩大,该类砌体的峰值压应变、极限压应变均低于普通混凝土砌块砌体。建立了以砌体抗压强度、砌块抗压强度和砌筑砂浆抗压强度为自变量的这类新型砌体峰值压应变、极限压应变以及弹性模量计算公式。     

A study on durability properties of high-performance concretes incorporating high replacement levels of slag

This paper presents an experimental study of combined effects of curing method and high replacement levels of blast furnace slag on the mechanical and durability properties of high performance concrete. Two different curing methods were simulated as follows: wet cured (in water) and air cured (at 20°C and 65% RH). The concretes with slag were produced by partial substitution of cement with slag at varying amounts of 50–80%. The water to cementitious material ratio was maintained at 0.40 for all mixes. Properties that include compressive and splitting tensile strengths, water absorption by total immersion and by capillary rise, chloride penetration, and resistance of concrete against damage due to corrosion of the embedded reinforcement were measured at different ages up to 90 days. It was found that the incorporation of slag at 50% and above-replacement levels caused a reduction in strength, especially for the early age of air cured specimens. However, the strength increases with the presence of slag up to 60% replacement for the 90 day wet cured specimens. Test results also indicated that curing condition and replacement level had significant effects on the durability characteristics; in particular the most prominent effects were observed on slag blended cement concrete, which performed extremely well when the amount of slag used in the mixture increased up to 80%.     

Effects of gypsum and phosphoric acid on the properties of sodium silicate-based alkali-activated slag pastes

In this paper, the effects of gypsum and phosphoric acid on the properties of sodium silicate-based alkali-activated slag paste were examined. Alkali-activated slag is recognized as a good performing binder. However, it suffers from fast setting and drying shrinkage. Phosphoric acid has been used as a retarder and gypsum has been used as a drying-shrinkage inhibitor in previous studies. However, it is not known what will happen if one adds both of them to alkali-activated slag. In this study, the effects of gypsum and/or phosphoric acid on the compressive strength development, setting time and drying shrinkage of alkali-activated slag were examined. Experimental results indicated that adding gypsum shortened the setting time, and at the same age, the compressive strength reached a higher value when the amount of used gypsum is higher. Drying-shrinkage decreased when the amount of used gypsum increased; however, when 0.82 M phosphoric acid was added in the activator with gypsum the results were somewhat different. With added phosphoric acid, adding more gypsum shortened the setting time as well. The compressive strength of specimens with added gypsum was lower than that of control specimens under 28 days. Drying-shrinkage increased with phosphoric acid as the amount of used gypsum increased.     

Experimental assessment of flue gas desulfurization residues and basic oxygen furnace slag on fatigue and moisture resistance of HMA

Basic oxygen furnace (BOF) slag and flue gas desulfurization (FGD) residues both are industrial wastes. Research on using BOF slag as a novel aggregate and FGD residues as a filler in road construction has benefits both in environment and economics. The main objective of this research was to evaluate the effect of FGD residues and BOF slag on the fatigue performance and moisture resistance of asphalt mixtures. The fatigue performance of asphalt mixture was conducted by means of indirect tensile fatigue test. Stress loading control mode, with four stress levels (300, 400, 500 and 600 kPa), was used in this research. Statistic t‐test was adopted, and it had approved the positive effect of BOF slag and FGD residues on the fatigue lives of asphalt mixture. Moisture resistance of asphalt mixture was investigated by retained Marshall stability test and tensile strength ratio test. Research results indicate that BOF slag and FGD residues can improve the fatigue and moisture resistance, when the BOF slag and FGD residues based asphalt mixture was designed properly.     

High-volume natural volcanic pozzolan and limestone powder as partial replacements for portland cement in self-compacting and sustainable concrete

A laboratory study demonstrates that high volume, 45% by mass replacement of portland cement (OPC) with 30% finely-ground basaltic ash from Saudi Arabia (NP) and 15% limestone powder (LS) produces concrete with good workability, high 28-day compressive strength (39 MPa), excellent one year strength (57 MPa), and very high resistance to chloride penetration. Conventional OPC is produced by intergrinding 95% portland clinker and 5% gypsum, and its clinker factor (CF) thus equals 0.95. With 30% NP and 15% LS portland clinker replacement, the CF of the blended ternary PC equals 0.52 so that 48% CO₂ emissions could be avoided, while enhancing strength development and durability in the resulting self-compacting concrete (SCC). Petrographic and scanning electron microscopy (SEM) investigations of the crushed NP and finely-ground NP in the concretes provide new insights into the heterogeneous fine-scale cementitious hydration products associated with basaltic ash-portland cement reactions.     

The effect of elevated initial temperatures on durability index values of plain and corex slag concretes

The initial maximum placing temperature of concrete is usually limited by specifications, which might result in the concrete supplier having to implement cooling measures in hot climates. These limitations were originally based upon work that examined the influence of elevated temperature on the compressive strength of concrete. The question arises as to whether these limiting values are appropriate for the transport properties of concrete, which largely govern its durability. This was investigated using the durability index test approach developed in South Africa. It was found that, while there was on occasions a statistically significant influence on the test results at an elevated initial temperature of 37°C, this effect was usually of no practical importance. One exception was the gas permeability of corex slag concretes (relating to resistance to carbonation), which led to a decrease in performance at 37°C that was both statistically significant and of practical importance. Notwithstanding this, the results indicate that carbonation-induced corrosion is unlikely provided a cover of at least 30 mm is achieved.     

Synthesis,characterization and properties of calcium ferroaluminate belite cements produced with electric arc furnace steel slag as raw material

This study investigated the use of 10 (M1), 17 (M2) and 27 wt.% (M3) electric arc furnace steel slag (EAFS) as a raw material in the production of calcium ferroaluminate belite cement clinker, after firing at 1320 °C. The thermal behavior of the raw meals was studied by TG/DSC and XRD whereas for the analysis of the clinkers, XRD/QXRD, SEM/EDS and EPMA were employed. The resulting clinker was co-grinded with 5 and 20 wt.% Flue Gas Desulfurization (FGD) gypsum and the properties were determined by a series of tests in accordance to EN standards. The evolution of hydration was investigated by SEM and the development of compressive strength. The results revealed that the formed phases in the clinkers were C₂S, C₄AF and C₄A₃Ŝ. The main hydration products were ettringite, AFm and hydrogarnet. The leached Cr^VI was below 1 ppm in M3. Compressive strength in cements with 5 wt.% FGD gypsum was (in MPa): 18.3 for M1, 14.3 for M2 and 7.8 for M3 at 28 days, whereas for 20 wt.% FGD gypsum, the values were almost doubled.     

Application of high performance polypropylene fibers in concrete lining of water tunnels

In this study, the application of high performance polypropylene fibers (HPP fibers) in concrete lining of water tunnels, was investigated experimentally. A comparison between the behavior of steel fiber reinforced concrete and HPP fiber reinforced concrete with ordinary concrete is drawn. Advantages and shortcomings of HPP fibers used for concrete lining of water tunnels are also presented.The obtained results showed that the HPP fibers were not effective in compressive strength when compared to steel fibers, but the effects of HPP fibers on tensile strength, flexural strength, toughness and energy absorption of concrete were significant. Based on the results, the effects of HPP fibers on concrete characteristics such as the flexural toughness, concrete permeability and resistance to chloride penetration were higher than those of steel fibers. The results also showed that with application of HPP fibers, durability and serviceability of the concrete linings can be improved.     

铜渣粉作为混凝土掺合料的研究进展

铜渣是铜冶炼和精炼过程的副产物,以每产1 t铜副产2.2 t铜渣计算,2017年全球铜渣排放量达到了5 170万t。但目前的铜渣处理仍以堆放为主,不仅占用了大量土地,重金属成分对堆放地也造成了严重的环境污染。铜渣,特别是水淬铜渣中含有较多的玻璃体,用作混凝土掺合料可以替代粉煤灰和矿渣,解决某些地区掺合料紧缺的状况。本文归纳总结了铜渣粉对混凝土工作性、力学性能和耐久性的影响,分析了铜渣作为掺合料使用时的环境安全性,提出了铜渣作为掺合料使用应注意的问题,为铜渣粉在混凝土行业中规模化应用提供了参考。 近年的研究成果表明,水淬铜渣中的玻璃体含量高、活性更好,而缓冷铜渣的玻璃体含量虽低,但仍有一定的活性。由于存在活性低和重金属成分高的问题,铜渣粉对混凝土工作性、力学性能和耐久性的影响比矿渣、粉煤灰等常见掺合料复杂得多,阻碍了铜渣粉作为掺合料在混凝土中的应用。 虽然存在不同观点,但多数研究成果表明铜渣粉可起到降低放热量、改善工作性及减少用水量的作用,同时也会产生泌水率增加的问题。由于活性偏低、重金属成分较高,铜渣粉的缓凝作用明显,不过大掺量使用所引起的凝结时间延长问题在多数研究中是可控的。铜渣粉导致混凝土早期强度不足,可通过添加激发剂、提高细度、降低水灰比等方式予以缓解和控制。铜渣粉对混凝土强度的负面影响会随龄期延长逐渐减轻,甚至在一段时间后对强度有利。此外,铜渣粉还能提高混凝土弹性模量并减少收缩,对抗断裂性能也无明显不利影响。但以不同指标评价混凝土脆性时,铜渣粉的作用还存在较大的争议。由于可促使毛细孔隙等有害孔隙数量减少,铜渣粉可使混凝土的吸水速率和吸水量降低,从而使耐久性等级有所改善。除优化孔隙结构外,铜渣粉与Ca(OH)₂反应生成C-S-H凝胶,可改善过渡区,提高混凝土抗碳化、抗氯离子渗透性和抗硫酸盐侵蚀的能力。     

保水降温功能水泥混凝土铺面材料组成设计与性能研究

将水泥、粉煤灰和磨细高炉矿渣作为保水材料灌注于多孔水泥混凝土母体中,形成具有保水降温功能的铺面材料。分别提供了多孔水泥混凝土母体和保水材料的设计方法,并成型试件对保水铺面水泥混凝土材料的强度、降温效果和抗冻性进行了测试。实验结果表明设计的多孔水泥混凝土母体和保水材料均满足施工和功能要求,成型的保水降温功能水泥混凝土试件28d抗压强度和抗折强度分别能够达到27.7和38.2MPa;在最高气温为33℃的测试条件下,其表面最高温度比普通水泥混凝土降温7℃左右,但随着水分的减少降温效果变差;此外,冻融后保水降温水泥混凝土抗压强度会下降,但不明显。     

Compressive strength and durability properties of ceramic wastes based concrete

This paper presents an experimental study on the properties and on the durability of concrete containing ceramic wastes. Several concrete mixes possessing a target mean compressive strength of 30 MPa were prepared with 20% cement replacement by ceramic powder (W/B = 0.6). A concrete mix with ceramic sand and granite aggregates were also prepared as well as a concrete mix with natural sand and coarse ceramic aggregates (W/B = 0.5). The mechanical and durability performance of ceramic waste based concrete are assessed by means of mechanical tests, water performance, permeability, chloride diffusion and also accelerated aging tests. Results show that concrete with partial cement replacement by ceramic powder although it has minor strength loss possess increase durability performance. Results also shows that concrete mixtures with ceramic aggregates perform better than the control concrete mixtures concerning compressive strength, capillarity water absorption, oxygen permeability and chloride diffusion. The replacement of cement and aggregates in concrete by ceramic wastes will have major environmental benefits.     

Concrete durability presented by acceptable chloride level and chloride diffusion coefficient in concrete: 10-year results in marine site

Generally, concrete with high resistance to the marine environment should have high compressive strength, a low chloride diffusion coefficient (D _C), and a high acceptable chloride level (Ac). Considering all parameters simultaneously, this study evaluated the degree of fly ash concrete durability based on 10-year results in a marine site. Based on the concrete durability (Ac/D _C, as compared to cement concrete with a W/B ratio of 0.45) and compressive strength, the degree of concrete durability proposed in this study indicates that fly ash concretes with a W/B ratio of 0.45 and 15–35 wt % fly ash replacement exhibit high-quality performance in a marine site.     

活性掺合料对脱硫基粉刷石膏制品性能的影响

利用脱硫石膏生产建筑石膏已经成为当前解决固体排放物问题的有效途径。粉刷石膏在耐水性和力学性能等方面的弱点影响其使用范围。本文研究复合掺加不同含量的活性掺合料对石膏制品耐水性和力学性能的影响。研究表明,掺加水泥和矿渣的效果最好,其耐水性可以提高40%,力学性能提高48%。     

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。     

钢渣粗骨料混凝土单轴受压应力-应变关系试验研究

为探究钢渣粗骨料混凝土稳定性及其应力-应变关系全曲线,该文对包头某钢铁公司的钢渣粗骨料进行了浸水膨胀率试验及压蒸粉化率试验并测其f-CaO含量;完成了6组不同钢渣替代率下的立方体抗压试验及棱柱体单轴受压试验,分析其破坏形态及受力变形特征,建立钢渣粗骨料混凝土本构关系模型。研究表明:该文所选钢渣的f-CaO含量、浸水膨胀率、压蒸粉化率均符合现行规范规定,稳定性良好;钢渣粗骨料混凝土单轴抗压强度随钢渣掺量的增加而提高,并高于普通混凝土抗压强度,破坏呈现的脆性特征也更为显著;钢渣粗骨料混凝土棱柱体抗压强度与立方体抗压强度的比值相较于普通混凝土更高。根据过镇海本构模型及Wee模型,并引入钢渣粗骨料含量的修正系数,对钢渣粗骨料混凝土应力-应变关系采用分段式表达。该文提出应力-应变模型与试验结果拟合程度较好,可以更加全面的描述钢渣粗骨料混凝土的单轴受压力学行为。