矿渣与涂层对混凝土抗氯离子侵蚀的影响

试验研究了不同掺量下单掺矿渣微粉、表面涂层材料(环氧树脂或聚合物水泥基防水材料)以及两者共同作用对混凝土抗氯离子侵蚀能力的影响,并分析了矿渣微粉改善混凝土抗氯离子渗透性能的机理。研究结果表明:矿渣微粉和表面涂层均可显著地提高混凝土的抗氯离子渗透能力;矿渣微粉的改善效果随着掺量的增加而增加;环氧树脂的作用效果比聚合物水泥基防水材料更明显;矿渣微粉与表面涂层材料结合使用效果更优;矿渣微粉的填充效应、对氢氧化钙的部分吸收以及对氯离子的初始固化能力是改善混凝土抗氯离子渗透性能的三个重要因素。     

矿渣微粉用作混凝土活性掺和料的研究

利用不同细度、不同掺量的矿渣微粉等量置换混凝土中的硅酸盐水泥,研究改变矿渣微粉的细度、掺量对混凝土性能的影响,优化矿渣微粉应用参数和使用效果。研究表明在本试验条件下,当矿渣细度控制在比表面积500m2/kg左右,掺量为20%～60%时,具有最佳的应用效果。     

抗海水腐蚀混凝土在电化厂工业盐罐池工程中的成功应用

电化厂的盐罐池由于经常受到饱和盐水的侵蚀 ,当采用普通混凝土时在较短时间内就因氯离子腐蚀而破坏。大掺量矿渣微粉抗海水腐蚀混凝土有优越的抗氯离子腐蚀性能 ,适用于受氯离子腐蚀的工程。通过对原材料和混凝土配合比的优选 ,将大掺量矿渣微粉抗海水腐蚀混凝土成功应用于江门市电化厂工业盐罐池工程中。     

矿渣微粉对水工混凝土抗氯离子渗透性影响的试验研究

渗透性是评定水工混凝土耐久性的一个重要指标,掺入矿渣微粉能够提高混凝土的致密性,改善混凝土对氯离子的渗透性。通过混凝土抗氯离子渗透性试验,研究了矿渣微粉掺量（0、15%、30%、45%）对高强（水胶比0.32）和普通（水胶比0.5）混凝土渗透性的影响规律。结果表明,降低水胶比,提高矿渣微粉掺量,能够显著提高混凝土抗氯离子的渗透性。相同水胶比,随着矿渣微粉掺量的增加,混凝土抗氯离子渗透性得到提高。水胶比越小,这种改善趋势越明显。     

水泥、矿渣微粉与减水剂相容性的实验研究

在大掺量矿渣微粉抗海水腐蚀混凝土中,必须使用大掺量矿渣微粉和高效减水剂。随着混凝土组分数量的增加,混凝土各种原材料之间的相容性问题也凸现出来。采用多种原材料进行的砂浆研究表明:水泥、矿渣微粉和高效减水剂之间存在相容性问题;可采用砂浆试件判断水泥、矿渣微粉和高效减水剂之间的相容性。     

硅砂粉与矿渣微粉复掺技术用于PHC管桩生产

设计研究了管桩生产用的混凝土配合比,将硅砂粉与矿渣微粉作为混凝土掺合料,在满足管桩生产要求前提下,以一定比例取代硅酸盐水泥,采用常压蒸汽养护和高压蒸汽养护,并测定了混凝土的脱模强度及高压蒸汽养护后的强度.试验结果表明,利用硅砂粉和矿渣微粉以一定比例复掺等量代替水泥生产PHC管桩是可行的,其中,复合掺合料的取代比例可达45%,硅砂粉和矿渣微粉的掺量分别为150 kg/m3、50 kg/m3,混凝土脱模及压蒸后的抗压强度分别为49.1MPa、89.0MPa,符合管桩国家标准要求.     

机械激发对钢渣矿渣微粉活性的影响

将比表面积为400、450、500 m2/kg的钢渣粉进行活性指数试验,并将比表面积为450 m2/kg的钢渣粉与400、450、500 m2/kg三种矿渣粉复合,研究钢渣矿渣复合微粉的活性。试验结果表明:比表面积为500 m2/kg的钢渣粉活性可达一级粉要求。钢渣和矿渣比表面积为450 m2/kg,钢渣掺量在复合微粉为20%~30%时,复合微粉活性可达到或接近S95级,可满足混凝土结构强度设计要求。同时,对复合微粉水化产物微观形貌进SEM观察,以判断复合微粉的水化情况。     

高温后纤维矿渣微粉混凝土抗压强度

通过纤维矿渣微粉混凝土高温后的抗压试验,分析了温度、矿渣微粉置换水泥率、纤维类别和掺量、混凝土基体强度等级等对混凝土高温后抗压强度的影响.结果表明:随着温度的升高,高温后纤维矿渣微粉混凝土的抗压强度以及高温后与常温下抗压强度比均不断降低,且400℃后降低幅度急增;矿渣微粉、钢纤维和聚丙烯纤维的掺入在不同程度上提高了高温后纤维矿渣微粉混凝土的抗压强度.在试验研究的基础上,建立了考虑温度、矿渣微粉置换水泥率、钢纤维体积分数和聚丙烯纤维掺量共同影响的高温后纤维矿渣微粉混凝土立方体抗压强度和轴心抗压强度的计算模型,为纤维混凝土结构的抗火设计及灾后处理提供了理论依据.     

基于矿渣微粉配制高性能混凝土试验研究

通过使用矿渣微粉等量替代混凝土中的普通硅酸盐水泥试验分析,研究矿渣微粉替代量对混凝土和易性和强度的影响,以及龄期对抗压强度和抗拉强度的影响。试验结果表明:矿渣微粉可以有效改善混凝土拌合物的保水性和黏聚性,提高混凝土的后期强度;低掺量(≤40%)矿渣微粉混凝土早期强度大于基准混凝土(掺量0);掺矿渣微粉混凝土的强度随着掺量的增加而降低。     

掺矿渣微粉轻质发泡复合硅钙板新技术研发

针对原有聚苯乙烯颗粒水泥夹心板容重偏大、干燥易收缩和接缝处易出现微裂纹的技术瓶颈问题,贵州瑞泰实业有限公司(以下简称瑞泰公司)与贵州大学联合攻关,通过实验室和中试试验研究,开展矿渣微粉掺量及增稳性能优化工作,在现有产品中掺入矿渣微粉,并引入气孔,同时,优化了聚苯颗粒添加量、水泥掺入比例、发泡剂掺量及养护时间等原料和工艺条件,共同研发了一种新型建筑墙板材料——掺矿渣微粉轻质发泡复合硅钙墙板.优化后产品主要物理性能优于国家标准,超过预期目标,具体为:面密度(90 mm厚)从82 kg/m2降到67 kg/m2,干燥收缩率从0.60 mm/m降到0.40 mm/m,矿渣微粉掺量达到56.6％.     

Effect of cement type on the resistance of concrete against chloride penetration

In chloride containing environment, chloride permeability of concrete is an important parameter affecting the service life of concrete structures. The primary objective of this experimental study was to study the effect of cement types on the resistance of concrete against chloride penetration for given compressive strength classes. These cements included two different types of granulated blast-furnace slag cement (CEM III/A 32.5N and CEM III/A 42.5N), a sulfate resisting cement (SRC 32.5), and a Portland cement blended with fly ash; all of which compared to an ordinary Portland cement (CEM I 42.5R). For each binder type, four concretes at different strength classes were produced and as a result 20 mixtures were obtained. Rapid chloride ion penetration tests according to ASTM C 1202 were conducted. In addition, electrical resistivity and capillary water absorption tests were carried out. In order to characterize the concrete quality, compressive strength of the specimens were also obtained. The test results clearly demonstrated that the blast-furnace slag cements have the highest resistance against chloride penetration, while the pure Portland cement and sulfate resisting cement have the lowest resistance. Concretes produced with the sulfate resisting cement had substantially higher capillary sorption compared to other mixtures. Test results confirmed the strong relationship between the chloride permeability and electrical resistivity.     

AgNO_3显色法判断氯离子渗透深度的影响因素

采用不同配合比混凝土试样进行非稳态电迁移(RCM,rapid chloride migration)试验,研究AgNO3显色法对判断氯离子渗透深度的影响.结果表明:相比实际的氯离子渗透边界,采用AgNO3显色法测量的氯离子渗透深度值偏小,用RCM法计算的快速氯离子扩散系数较实际结果小;氯离子显色边界浓度对其扩散系数计算值的影响较大,试验中不同边界浓度对氯离子扩散系数的影响可达20%以上;水泥基材料物相中Ca(OH)2的含量对氯离子边界浓度有较大影响,存在一定的函数关系,Ca(OH)2的含量越高,氯离子边界浓度越大;掺入粉煤灰后,氯离子显色的边界浓度减小,用AgNO3显色法测得的渗透深度相应增大,采用RCM测得的氯离子快速扩散系数偏大.     

Effect of W/C ratio on covering depth of fly ash concrete in marine environment

This investigation studied the effect of W/C ratio on covering depth required against the corrosion of embedded steel of fly ash concrete in marine environment up to 4-year exposure. Fly ash was used to partially replace Portland cement type I at 0%, 15%, 25%, 35%, and 50% by weight of cementitious material. Water to cementitious material ratios (W/C) of fly ash concretes were varied at 0.45, 0.55, and 0.65. The 200-mm concrete cube specimens were cast and steel bars with 12-mm diameter and 50 mm in length were inserted in the concrete with the covering depth of 10, 20, 50, and 75 mm. The specimens were cured in water for 28 days, and then placed to the tidal zone of marine environment in the Gulf of Thailand. Subsequently, the concrete specimens were tested for the compressive strength, chloride penetration profile and corrosion of embedded steel bar after being exposed to tidal zone for 2, 3, and 4 years. The results showed that the concrete mixed with Portland cement type I exhibited higher rate of the chloride penetration than the fly ash concrete. The chloride penetration of fly ash concrete was comparatively low and decreased with the increasing of fly ash content. The increase of fly ash replacement and the decrease of W/C ratio could reduce the covering depth required for the initial corrosion of the steel bar. Interestingly, fly ash concretes with 35% and 50% cement replacement and having W/C ratio of 0.65 provided better corrosion resistance at 4-year exposure than the control concrete with W/C ratio of 0.45. In addition, the covering depth of concrete with compressive strength of 30 MPa (W/C ratio of 0.65) could be reduced from 50 to 30 mm by the addition of fly ash up to 50%.     

Relationship between average pore diameter and chloride diffusivity in various concretes

Since concrete is a heterogeneous composite material which is composed of cement, aggregate, mineral admixture, and so on, the microstructure of concrete is very important to predict transport property associated with the durability of concrete. In this paper, 12 concrete specimens composed of six types of Portland and blended cements with water–binder ratios of 40% and 50% were manufactured to investigate the characteristics of capillary pores using mercury intrusion porosimetry technique and examine measurements of chloride diffusivity in concrete regard to electric potential. The average pore diameter of concretes decreased in the following order: (1) low heat cement, (2) ordinary Portland cement and sulfate resistant cement, (3) blended cement with 40% of slag, (4) blended cement with 60% of slag and, (5) ternary based cement. On the other hand, chloride diffusivity decreased in the following order: (1) low heat cement, (2) ordinary Portland cement and sulfate resistant cement, (4) blended cement with 40% of slag, (3) blended cement with 60% of slag and ternary based cement, indifferently from water–binder ratio. From the result of regression analysis, the chloride diffusivity increased with the average pore diameter presenting a very satisfactory correlation factor exceeding 0.91.     

Influence of fly ash fineness on the chloride penetration of concrete

In this paper, the resistance to chloride penetration of concrete containing fly ash of various finenesses was examined. Three different fly ash finenesses viz., original fly ash, 45% fine portion and 10% fine portion fly ashes were used for the study. Chloride resistance of concretes was evaluated using the measurement of the Coulomb charge as per ASTM C1202 and by determination of chloride ingress after different periods of exposure to 3% NaCl solution in full immersion and partial immersion modes. From the tests, it is found that the resistance to chloride penetration of concrete depends on the fineness of fly ash. The rapid chloride permeability test (ASTM C1202) clearly indicates that the Coulomb charge of concrete at the age of 28 days is significantly reduced with the incorporation of fly ash. The decrease is promoted with an increase in fly ash fineness. The immersion of cut cylinders in the 3% NaCl solution for 3 and 6 months confirm that the resistance of the chloride penetration of concrete increases with an incorporation with fly ash and with an increase in the fly ash fineness.     

High performance concrete containing lower slag amount: A complex view of mechanical and durability properties

A wide set of parameters of concrete containing 10% of ground granulated blast furnace slag as Portland cement replacement involving basic material characteristics, mechanical and fracture-mechanical properties, durability characteristics, hydric and thermal properties and chloride binding characteristics is determined and compared with the parameters of reference Portland cement concrete with otherwise the same composition. The experimental results show that the replacement of Portland cement by even such a low amount of ground granulated blast furnace slag as environmental more friendly and still valuable alternative binder either affects positively or at least does not worsen in a significant way the substantial properties of hardened concrete mix. The mechanical and fracture-mechanical properties are found to be very similar as compared to the reference mix, the liquid water transport parameters of the mix containing slag are significantly better, the basic durability characteristics such as the frost resistance and corrosion resistance similar and very good, the resistance against de-icing salts slightly worse. These findings may be significant for the future use of slag in the countries where its available amount is decreasing and its more efficient use as a binder than it was common to date can appear necessary.     

The effect of fineness on the properties of the blended cements incorporating ground granulated blast furnace slag and ground basaltic pumice

In this study, the effect of the fineness on the compressive strength, sodium sulfate resistance and the heat of hydration of the both blended and plain Portland cement (PPC) were investigated. The grinding time of both clinker and additives were also studied. The result indicated that ground basaltic pumice (GBP) and clinker had lower grindability compared to ground granulated blast furnace slag (GGBFS). Blended cement had higher strength values, particularly at later ages, compared to PPC for the same Blaine values. It was observed that the finer ground blended cement specimens had higher compressive strength, sodium sulfate resistance compared to the coarser blended cement and PPC. The heat of the hydration of blended cement was lower than the heat of hydration of PPC when the fineness was held constant.     

矿物掺合料与纤维双掺对混凝土抗渗性能的影响及工程应用

采用RCM氯离子扩散系数法和渗水高度法,研究了粉煤灰、矿粉、PVA纤维、纤维素纤维的掺入对混凝土抗渗性能的影响.试验结果表明,粉煤灰和矿粉的掺入能有效降低混凝土中氯离子扩散系数和渗水高度.在掺加矿物掺合料的基础上再掺入纤维混凝土的抗渗性能进一步提高,双掺对混凝土抗渗性能提高的复合效应明显.     

Studies on the aspects of chloride ion determination in different types of concrete under macro-cell corrosion conditions

In the present investigation various extraction methods have been carried out for the estimation of free chloride and total chloride contents in different types of concretes, namely ordinary Portland cement (OPC), Pozzolana Portland cement (PPC) and Portland slag cement (PSC). Macro-cell concrete specimens were cast and subjected to severe alternate wetting and drying cycles of 10-months exposure. Concrete core samples were collected from the above specimens under different depths, namely 20, 40 and 60 mm. Six extraction methods for determination of free chloride and two extraction methods for determination of total chlorides in concrete have been carried out. Boiling water method was found to be a suitable for the determination of free chloride contents in concrete. As the depth increases the amount of chloride ion decreases. Filtration method is found to be not suitable for the determination of chloride ion in concrete. There is no quick method for determining the chloride concentration in concrete either in the field or in laboratory. Water-soluble chloride alone is a good indicator of the concentration of chloride ion in concrete. ISE method appears to be most convenient but it requires lot of calibration before analysis.