微波辐照活化煤矸石-硅酸盐水泥体系试验研究

通过宏观试验和扫描电镜（SEM）微观测试分析技术研究了微波辐照活化煤矸石及掺量对硅酸盐水泥体系的细度、凝结时间、体积安定性、火山灰活性和强度等性能的影响，结果表明，大掺量微波辐照活化煤矸石对硅酸盐水泥体系各项技术性能无不良影响；微波辐照活化煤矸石硅酸盐水泥在水化硬化过程中有微膨胀，但体积安定性满足国家相关规范要求；在煤...     

微波辐照活化煤矸石-硅酸盐水泥体系试验研究

通过宏观试验和扫描电镜(SEM)微观测试分析技术研究了微波辐照活化煤矸石及掺量对硅酸盐水泥体系的细度、凝结时间、体积安定性、火山灰活性和强度等性能的影响,结果表明,大掺量微波辐照活化煤矸石对硅酸盐水泥体系各项技术性能无不良影响;微波辐照活化煤矸石硅酸盐水泥在水化硬化过程中有微膨胀,但体积安定性满足国家相关规范要求;在煤矸石中添加少量CaO利用微波技术可获得质地优良的水泥辅助性胶凝组分;与常规热活化煤矸石方法相比微波辐照活化煤矸石的节能和生产成本降低效果十分显著。     

机械粉磨对煤矸石质胶凝材料活性的影响

粉磨成不同细度的煅烧矸,与硅酸盐水泥熟料和二水石膏和标准砂按比例混合制得砂浆,测其28天力学性能。借助XRD光谱衍射和SEM扫描电镜手段,对不同细度的煤矸石进行微观分析研究。结果表明:随着煤矸石细度的增加,复合砂浆28天的力学性能呈先增大后减小的趋势。机械粉磨可以减小煤矸石颗粒的细度,并使煤矸石中非活性石英的结晶度降低,活性物质数量增加,提高煤矸石的胶凝活性。     

Ⅲ级粉煤灰掺量、细度对水泥强度发展的影响

为了开发和应用数量大、成分复杂、均匀性差且活性低的Ⅲ级粉煤灰,本文中通过对Ⅲ级粉煤灰的粉磨处理,研究了Ⅲ级粉煤灰的掺量、细度对硅酸盐水泥、普通水泥强度发展的影响。结果表明,为了更好地发挥粉煤灰的活性,Ⅲ级粉煤灰在配制硅酸盐水泥、普通水泥时存在一个合理的粉磨细度和适宜的掺量,当粉煤灰的掺量小于5%时,细度应控制在500m2/kg左右;当掺量为10%￣15%时,细应为600m2/kg左右。     

硫铝酸钙改性硅酸盐水泥应用研究进展

硫铝酸钙改性硅酸盐水泥熟料兼具硅酸盐水泥熟料和硫铝酸盐水泥熟料的优良性能,同时该种水泥熟料对粉煤灰等火山灰类材料具有超强的活性激发效果,这使得硫铝酸钙改性硅酸盐水泥具有广阔的应用前景。主要概括了硫铝酸盐改性硅酸盐水泥的性能及水化特性,综述了该种水泥与不同矿物掺合料的复合性能以及与化学外加剂的适应性,提出了硫铝酸钙改性硅酸盐水泥存在的问题及改善措施。     

KHM170型卧辊磨制备钢渣超细粉工业试验研究

基于KHM170型卧辊磨的钢渣超细粉制备终粉磨工业试验系统,在给定钢渣粉、矿渣粉、水泥熟料粉的质量和粒度范围内,进行用钢渣粉部分代替矿渣粉制作水泥混凝土的强度试验。结果表明,KHM卧辊磨终粉磨系统可以实现钢渣超细粉终粉磨,可用于以热焖渣、滚筒渣为原料制备钢渣微粉的工业化生产;矿渣粉中掺加质量分数不超过30%的钢渣粉,且在满足钢渣粉比表面积大于矿渣粉比表面积和水泥熟料粉比表面积时,可以作为优选的混合材料大量用于混凝土。     

卧式行星磨内物料的粉磨特性

利用自制卧式行星磨对钢渣及水泥熟料进行粉磨特性及粉磨动力学研究。结果表明,粉磨后物料都满足Rosin-Rammler-Bennet粒度分布规律,钢渣及水泥熟料粉磨过程都可用一级Kapur函数描述,钢渣的粉磨速率小于水泥熟料的;在实验条件下,相对于水泥熟料,钢渣破碎更多地表现为摩擦破碎方式;钢渣进料粒级对粉磨后所得到产品的概率影响较大,粉磨前可将钢渣预破碎至粒径为1.7 mm。     

混凝土中硅粉的作用机理

硅粉比表面积大,颗粒极细,其主要的化学式是SiO_2,硅粉中二氧化硅的含量越高,细度越细在碱性溶液中的活性就越大,其对混凝土的改性效果也就越好。硅粉能够改善硬化水泥浆体的微结构,具有很高的火山灰活性,通常使用其作为一种辅助性的胶凝材料;硅粉作为掺合料在混凝土中可以替代部分的水泥,并改善水泥颗粒粒径分布和级配。     

研磨体形状对水泥熟料破碎参数的影响

为探讨研磨体形状对破碎参数的影响,采用钢球和钢段两种形状研磨体对水泥熟料进行粉磨,通过对粉磨产物的筛分处理,分析其粒度分布情况,研究粉磨过程中粉磨动力学方程的表述形式,最后运用非线性拟合技术进行回归分析。结果表明:采用上述两种形状研磨体,水泥熟料的粉磨均遵循一级粉磨动力学方程。钢段的破碎速率高于钢球的破碎速率,钢段粉磨物料可以在较短时间内达到预定细度。进一步研究证实:破碎分布函数基本不受研磨体形状的影响,与进料粒度有关。     

新型高性能水泥基无收缩灌浆料的研制

研究了磷渣复合粉掺量与细度、集料、早强剂和膨胀剂等对水泥基灌浆料工作性、力学性能及体积稳定性的影响。研究表明磷渣复合粉有利于灌浆料工作性能及后期强度的提高,以特细砂为骨料,甲酸钙为早强剂,塑性膨胀剂同中后期膨胀剂HCSA与MgO复合使用,可制备出流动性能高,早期及后期强度高,微膨胀等优点的高性能水泥基无收缩灌浆料。     

An analysis of the properties of Portland limestone cements and concrete

In this paper the main factors affecting the properties of Portland limestone cements are discussed while the hydration behavior of limestone cements is examined. In addition, the intergrinding process, concerning the production of the limestone cements, is studied. Finally the properties and the behavior of limestone cement concrete as well as the corrosion behavior of limestone cement mortar are investigated. It is concluded that the fineness of clinker and limestone is strongly connected with the limestone content and the fineness of the cement. The limestone cements indicate satisfactory strength and generally demand less water than the relative pure cements. The limestone addition improves the clinker reactivity and the exploitation of its hydraulic potential. The Portland limestone cements indicate competitive concrete properties and improve the corrosion performance of the concrete.     

Combined effect of chemical nature and fineness of mineral powders on Portland cement hydration

This paper focuses on the influence of the chemical nature and the fineness of the fillers on the hydration process and on the compressive strength development. Four different types of fillers are considered in combination with Portland cement: quartzite filler, alumina filler, limestone filler, and silica fume. The study deals with blended mortars having a 0.45 water to powder (cement and filler) ratio with a 10% substitution of cement by filler. Quartzite fillers do not seem to accelerate the hydration process in a significant way. No positive effect is noticed on the strength development either. The presence of a fine inert alumina powder increases the rate of early hydration of Portland cement. The greater the fineness, the faster the rate of hydration heat development. This reactivity leads to an increase in the compressive strength at early age for mortar containing the finest alumina powders. In case of coarse alumina powder, no acceleration effect is obtained. Finely ground limestone (calcite) fillers promote heterogeneous nucleation of hydrates which significantly accelerates hydration. At early age, this also results in an increased mortar compressive strength in comparison with the control mortar. From the obtained results, it is clear that both chemical natures as well as fineness are important with regard to the accelerating effect of the hydration process. With increasing fineness, the accelerating effect increases. For powders with comparable fineness, it is clear that limestone powder has a more significant accelerating effect than silica fume and alumina filler. Quartzite filler seems to have no significant effect.     

钢渣细度和掺量对钢渣复合水泥力学性能的影响

为找出在钢渣复合水泥中钢渣的最佳细度和最佳掺量,从钢渣的粉磨时间、掺量、不同助磨剂的作用和水泥配比等方面研究钢渣细度及掺量对复合水泥力学性能的影响,分析各个影响因素的作用。结果表明,随着磨细钢渣粒度的减小,钢渣复合水泥的抗折、抗压强度会有不同程度的提高;磨细钢渣的掺量为10%和20%时,钢渣复合水泥的力学性能较好,抗折、抗压强度甚至超过纯水泥;当掺量为30%和40%时,复合水泥力学强度下降幅度较大,3 d抗折强度不符合国家标准规定。     

Some Engineering Properties of Limestone Concrete

In order to reduce energy consumption and CO₂ emission and increase production, cement manufacturers are blending or intergrinding mineral additives such as slag, natural pozzolans, sand, and limestone. The reduced cost of limestone is mainly due to energy savings by substitution of a portion of the calcined clinker with a small amount of limestone and to the presence of limestone deposits near cement kilns, and hence, reduced transportation costs. This paper reports on a preliminary study underway on the performance of limestone cement mortar and concrete. The effect of different levels of limestone cement replacement (0% to 35%) on physical and mechanical properties of cement mortar is reported, as well as the effect of fineness of both clinker and limestone. From the test results, it was found that it is possible to manufacture cement with limestone addition with comparable or superior performance to that of ordinary Portland cement, provided that proper limestone quality is selected with optimum content and the optimum levels of fineness of both limestone and clinker are used. However, further research is needed to determine long-term performance, especially in marine and hot environments.     

A study on the parameters affecting the properties of Portland limestone cements

In this paper the parameters affecting the properties of Portland limestone cements are investigated. Portland limestone cements of different fineness and limestone content have been produced by intergrinding clinker, gypsum and limestone. Two kinds of clinker of different chemical composition, mineralogical composition and strength development and three limestones, with different contents of calcite, dolomite, quartz and clay, have been used. It is concluded that the appropriate choice of the clinker quality, limestone quality, % limestone content and cement fineness can lead to the production of a limestone cement with the desired properties. Limestone cements, having up to 10% limestone content and fineness up to a limit value, develop almost the same compressive strength, as the corresponding pure cements. The limestone cements, generally have lower paste water demand than the relative pure cements and the water demand decrease is mainly affected by the clinker type and limestone quality. In any case the properties of the limestone cements are affected by the interaction of the two components rather than their individual properties.     

Efficient utilization of cementitious materials to produce sustainable blended cement

To achieve sustainable development of cement industry, cementitious efficiency of different cement clinker and supplementary cementitious materials (SCMs) fractions, in terms of hydration process and strength contribution ratio, was characterized. The results show that blast furnace slag and steel slag should preferably be arranged in fine fractions due to their desirable hydration processes and high strength contribution ratios. Cement clinker should be positioned in intermediate fraction (8–24 μm) due to its proper hydration process. Replacement of cement clinker by SCMs with low activity or inert fillers in coarse fractions was also suggested, because coarse cement clinker fractions gave very low hydration degrees and little strength contribution. Both early and late properties of gap-graded blended cements prepared can be comparable with or higher than those of Portland cement, indicating both cement clinker and SCMs were used more efficiently. These blended cements also give additional cost savings and reduced environmental impact.     

Micro-structural development of gap-graded blended cement pastes containing a high amount of supplementary cementitious materials

To clarify the strength improvement mechanism of gap-graded blended cements with a high amount of supplementary cementitious materials, phase composition of hardened gap-graded blended cement pastes was quantified, and compared with those of Portland cement paste and reference blended cement (prepared by co-grinding) paste. The results show that the gap-graded blended cement pastes containing only 25% cement clinker by mass have comparable amount of gel products and porosity with Portland cement paste at all tested ages. For gap-graded blended cement pastes, about 40% of the total gel products can be attributed to the hydration of fine blast furnace slag, and the main un-hydrated component is coarse fly ash, corresponding to un-hydrated cement clinker in Portland cement paste. Further, pore size refinement is much more pronounced in gap-graded blended cement pastes, attributing to high initial packing density of cement paste (grain size refinement) and significant hydration of BFS.     

Hydration and properties of sodium sulfate activated slag

Interest in alkali-activated slag as a construction material is increasing, primarily due to its environmentally friendly nature. Although strong alkaline activators, such as sodium hydroxide and sodium silicate solution, are preferred for high strength, none of them exists naturally and their manufacturing process is quite energy intensive. Whilst sodium sulfate (Na₂SO₄) can be obtained from natural resources, the early strength of Na₂SO₄ activated slag is usually low. In this paper, the effects of slag fineness and Na₂SO₄ dosage on strength, pH, hydration and microstructure were investigated and compared with those of a pure Portland cement (PC). Test results indicated that increasing the slag fineness is a more effective approach than increasing Na₂SO₄ dosage for increasing both the early and long-term strength of Na₂SO₄ activated slags. In addition, increasing the slag fineness can also increase the strength without increasing the pH of the hardened matrix, which is beneficial for immobilizing certain types of nuclear waste containing reactive metals and resins.     

磷渣对水泥物理力学性能的影响研究

本文研究了不同细度和不同掺量磷渣对水泥物理性能的影响。结果表明：磷渣具有一定的减水作用，降低需水量；磷渣细度越细，其强度越高；随着磷渣掺量增加，早期胶砂抗压和抗折强度逐渐下降。     

The effect of clinker and limestone quality on the gas permeability,water absorption and pore structure of limestone cement concrete

In this paper the effect of clinker and limestone quality on the air permeability, water absorption and pore structure of limestone cement concrete is investigated. Portland limestone cements of different fineness and limestone content have been produced by intergrinding clinker, gypsum and limestone. Two clinkers with different chemical composition, mineralogical composition and strength development as well as three limestones, differing by their calcite, dolomite, quartz and clay contents, have been used. It is shown that the clinker quality significantly affects the gas permeability and sorptivity of the limestone cement concrete. Limestone cements with high C₃A and alkalis content seem to be more appropriate for improving the permeability properties of concrete. In addition, the effect of the limestone quality on the concrete permeability is not well established. The pore size distribution and more specifically the mean pore size affects the gas permeability and the sorptivity of the concrete. Finally it is concluded that, depending on the clinker quality and the cement fineness, limestone cement concrete, with an optimum limestone content, can give lower gas permeability and water absorption rate as compared with pure cement concrete.