钢渣粉性能优化及制备无熟料混凝土的试验研究

为提高固体废弃物综合利用率,通过钢渣分段除铁优化试验和钢渣粉对无熟料混凝土抗压强度影响试验,研究以钢渣-矿渣-脱硫石膏作为胶凝材料制备无熟料全固废混凝土。结果表明,经分段磁选可获得金属铁含量低于0.5%的高性能钢渣粉;当钢渣粉比表面积为640m~2/kg,m(钢渣)∶m(矿渣)=1∶2.5时,无熟料混凝土同时获得较优的3d和28d强度。XRD、TG-DSC、IR和FE-SEM分析表明,在脱硫石膏的激发作用下钢渣和矿渣可以相互促进水化,水化产物以AFt(钙矾石)和C-S-H(水化硅酸钙)凝胶为主。早期钢渣水化促进矿渣的解聚并结合脱硫石膏生成AFt网状结构,随着水化反应的进行胶凝体系生成的C-S-H凝胶充填于AFt网络中使硬化浆体结构致密从而保证强度的增长。     

玄武岩纤维增韧三元地质聚合物的制备

制备了玄武岩纤维强化增韧的碱激发粒化高炉矿渣-粉煤灰钢渣三元地质聚合物胶凝材料.当矿渣∶粉煤灰∶钢渣为7∶2∶1,玄武岩纤维掺量为0.6％(wt)时,所形成的地质聚合物表现出最佳力学性能,其抗折强度为10.8MPa,抗压强度为95.4MPa； XRD分析结果表明,玄武岩纤维的掺入对地质聚合物的物相无明显影响,SEM微观...     

钢渣激发脱硫石膏水硬性胶凝材料的研究

研究旨在开发一种以钢渣为碱性激发剂,以烟气脱硫石膏、矿渣粉为主要为原料的脱硫石膏水硬性胶凝材料。该胶凝体系3天抗折强度和抗压强度可达4.4 MPa和15.8 MPa;28天抗折强度和抗压强度可达9.4 MPa和50.7 MPa。其试样的强度随钢渣掺量的增加而增加,而钢渣含量一旦超过8%后,增长幅度变缓,甚至开始降低。XRD和SEM分析表明,脱硫石膏-矿渣-激发剂体系的水化产物主要是钙矾石和C-S-H凝胶。脱硫石膏在水化过程中一部分参与水化形成水化产物钙矾石,其余部分被水化产物所包裹起集料骨架作用。     

大掺量工业废渣激发制备钢渣复合胶凝材料的试验研究

在研究不同钢渣掺量胶凝体系稳定性的基础上,以40%的钢渣粉掺加15%矿渣粉、5%硅灰粉,采用自配复合激发剂成功地制备出早期抗折强度、抗压强度达到4.5MPa、18.8MPa且满足42.5强度等级的复合胶凝材料,通过其孔隙率及微观结构测试分析表明:钢渣复合胶凝材料水化产物致密,孔隙率低,后期抗压强度、抗折强度发展较好。     

钢渣激发脱硫石膏水硬性胶凝材料的研究

研究旨在开发一种以钢渣为碱性激发剂,以烟气脱硫石膏、矿渣粉为主要为原料的脱硫石膏水硬性胶凝材料。该胶凝体系3天抗折强度和抗压强度可达4.4 MPa和15.8 MPa;28天抗折强度和抗压强度可达9.4 MPa和50.7 MPa。其试样的强度随钢渣掺量的增加而增加,而钢渣含量一旦超过8%后,增长幅度变缓,甚至开始降低。XRD和SEM分析表明,脱硫石膏-矿渣-激发剂体系的水化产物主要是钙矾石和C-S-H凝胶。脱硫石膏在水化过程中一部分参与水化形成水化产物钙矾石,其余部分被水化产物所包裹起集料骨架作用。     

耐碱性玻璃纤维增强混凝土的制备及力学性能研究

采用ZrO_2含量为13.60%(质量分数)的耐碱性玻璃纤维和粉煤灰替换部分水泥制备了耐碱性玻璃纤维增强混凝土,研究了不同粉煤灰含量、玻璃纤维含量和水灰比对玻璃纤维增强混凝土(GRC)的耐老化性能的影响。结果表明,以W/B=0.35,粉煤灰含量(FA)/(C+FA)=40%,玻璃纤维含量2%(体积分数)制备的耐碱玻璃纤维增强混凝土抗压强度和抗弯强度以及干缩性能最好,抗压强度和抗弯强度分别为59.6和8.21 MPa;虽然掺入大量粉煤灰调节基体水化pH值,但是抗压实验断口形貌显示耐碱性玻璃纤维表面仍然受到腐蚀;通过自密实填料法制备的高粉煤灰含量自密实混凝土,其早期和后期的抗压强度和抗弯强度均表现优异,对高性能GRC复合材料的制备具有重要的指导意义。     

碱矿渣高性能混凝土冻融耐久性与损伤模型研究

采用矿渣、Na2SiO3和NaOH复合激发剂制备了高性能碱矿渣混凝土(Alakali-slag Concrete,ASC),通过冻融循环试验、扫描电镜和能谱分析测试,研究了ASC的冻融耐久性、微观结构、性能机理、冻融后内部损伤变量的变化规律及损伤模型。结果表明:ASC抗冻等级在F300以上,具有优异的抗冻融耐久性;ASC的水化产物主要为低Ca/Si比的C-S-H(Ⅰ)、碱性铝硅酸盐和沸石型矿物等,没有Ca(OH)2和过渡带,结构的密实性和均匀性好,抗压强度高达90MPa,因此ASC具有优异的抗冻性;以相对动弹模量为损伤变量建立了ASC冻融损伤模型,发现动弹模量衰减模型的拟合精度优于冻融累积损伤模型,幂函数模型比指数函数模型有更好的拟合精度和相关性,模型能够较好地反映ASC的冻融损伤规律和损伤程度。     

地聚合物混凝土抗冻性影响因素

通过调整地聚合物的氧化物SiO2/Al2 O3、Na2 O/Al2 O3和H2 O/Na2 O的物质的量比,利用碱激发偏高岭土制备不同强度等级的地聚合物混凝土.同时,用相同强度等级的普通硅酸盐水泥(OPC)混凝土作对比,评价地聚合物混凝土的抗冻性.结果表明:随着n(Na2O)/n(Al2O3)和n(H2 O)/n(Na2 O)增大,地聚合物混凝土的抗冻性降低;当n(SiO2)/n(Al2 O3)=3.3时,地聚合物混凝土的抗冻性最佳,冻融循环次数可达200.当地聚合物混凝土达到冻融极限时,相对动弹性模量损失较小,说明其冻融破坏的主要形式是表面脱落,而其内部结构破坏速率较OPC混凝土更慢.当抗压强度为30～50 MPa时,地聚合物混凝土抗冻性略优于OPC混凝土的抗冻性;但抗压强度在50～70 MPa时,OPC混凝土抗冻性远优于地聚合物混凝土抗冻性.此外,地聚合物混凝土具有较高水饱和系数,值均在0.85～0.95,说明地聚合物混凝土孔结构以开口孔为主.     

水泥和粉煤灰稳定钢渣-砼再生碎石路基混合料的制备及其性能

为减少对天然碎石的开采量，解决工业废渣和建筑固体废弃物大量堆积的问题，采用水泥和粉煤灰稳定钢渣-砼再生碎石制备路基混合料。在水泥和粉煤灰的掺量范围确定的情况下，通过干湿循环试验确定钢渣和砼再生碎石的较优质量比；当钢渣和砼再生碎石选取较优质量比时，通过三轴试验测试混合料的力学性能，进一步优化水泥和粉煤灰的质量分数；利用X射线衍射、扫描电子显微镜、能量色散X射线谱分析不同龄期制得的混合料的组成、微观结构及水化反应特征产物的变化规律，研究混合料的形成机制和强度影响因素。结果表明：当钢渣和砼再生碎石的质量比为3∶1时，制得的混合料的相对强度最高，失质量分数最小；当水泥掺入质量分数为5%、粉煤灰掺入质量分数为16%、钢渣和砼再生碎石的质量比为3∶1时，制得的混合料黏聚力最强，抗剪强度最大，力学性能较优；在水化早期掺入钢渣可增加钙矾石的生成量，提高制得的混合料的强度；制得的混合料的水化产物以水化硅酸钙、氢氧化钙和钙矾石为主；钙离子浓度的增加能增强制得的混合料的水化产物碱性，缩短硅酸钙水化物中的硅氧四面体链，降低制得的混合料的聚合度。     

钢渣矿渣基全固废胶凝材料的水化反应机理

以钢渣、矿渣和脱硫石膏为主要原料制备胶凝材料,使用XRD、IR、TG-DTA和SEM等手段探究胶凝材料的水化反应机理,研究了钢渣掺量对全固废混凝土强度的影响,以及胶凝材料浆体的p H值和代表性离子浓度的变化规律。结果表明,当原料质量比为m(钢渣):m(矿渣):m(石膏)=30:58:12时,全固废混凝土3 d、7 d和28 d可以获得较优的强度。随着反应龄期的增加胶凝材料水化溶液的pH值先减小后增大,Ca2+浓度和硅(铝)溶解物的早期浓度较低,后期浓度有所提高。在脱硫石膏的激发下钢渣和矿渣相互促进水化,水化产物以钙矾石(AFt)和水化硅酸钙(C-S-H)凝胶为主。在反应的后期,水化产物的数量迅速增加。针棒状的AFt晶体穿插在C-S-H凝胶内,使硬化浆体的结构更加致密。     

粉煤灰基矿聚材料骨料混合物的力学性能和耐久性

目前的研究表明,粉煤灰基矿聚材料骨料混合物在很多方面突现出比水泥更好的性能.该材料拟在水布垭面板堆石坝中应用,迫切需要对其力学性能及长期耐久性进行深入研究,为工程应用提供依据.本文主要采用三种胶凝材料用量的配合比,即100%矿聚材料、60%矿聚材料 40%水泥、100%水泥,通过立方体抗压、轴心抗拉、绝热温升、抗渗性、快速冻融等试验对比研究粉煤灰基矿聚材料骨料混合物的力学性能和耐久性,试图找出用于工程的最佳配比.结果表明,粉煤灰基矿聚材料骨料混合物和水泥混凝土相比,立方体抗压强度较大,轴心抗拉强度相近,绝热温升较小,抗渗性能较好,抗冻性能较差.     

矿物掺合料早期水化活性的测试和分析

本文采用环境扫描电子显微镜(ESEM)和热重-差热(TG-DTA)分析仪对磨细矿渣微粉、高钙粉煤灰、低钙粉煤灰的早期水化活性进行了系统测试和分析.理论和试验结果分析表明,掺合料取代水泥时,浆体早期抗压强度的提高取决于掺合料自身参与水化反应的速度和水化产物的数量.水化产物在掺合料颗粒表面沉积的速度和浆体中硅酸盐、铝酸盐水化产物的非蒸发水量随掺合料活性的提高而提高.掺合料活性按磨细矿渣微粉、高钙粉煤灰、低钙粉煤灰的顺序降低,将磨细矿渣微粉或高钙粉煤灰与低钙粉煤灰复合,可以克服低钙粉煤灰大掺量取代水泥时混凝土早期强度降低的缺陷,这是提高低钙粉煤灰在高强高性能混凝土中掺量的一个有效措施.     

Bond strength of reinforcing steel embedded in fly ash-based geopolymer concrete

Geopolymer concrete (GPC) is an emerging construction material that uses a by-product material such as fly ash as a complete substitute for cement. This paper evaluates the bond strength of fly ash based geopolymer concrete with reinforcing steel. Pull-out test in accordance with the ASTM A944 Standard was carried out on 24 geopolymer concrete and 24 ordinary Portland cement (OPC) concrete beam-end specimens, and the bond strengths of the two types of concrete were compared. The compressive strength of geopolymer concrete varied from 25 to 39 MPa. The other test parameters were concrete cover and bar diameter. The reinforcing steel was 20 mm and 24 mm diameter 500 MPa steel deformed bars. The concrete cover to bar diameter ratio varied from 1.71 to 3.62. Failure occurred with the splitting of concrete in the region bonded with the steel bar, in both geopolymer and OPC concrete specimens. Comparison of the test results shows that geopolymer concrete has higher bond strength than OPC concrete. This is because of the higher splitting tensile strength of geopolymer concrete than of OPC concrete of the same compressive strength. A comparison between the splitting tensile strengths of OPC and geopolymer concrete of compressive strengths ranging from 25 to 89 MPa shows that geopolymer concrete has higher splitting tensile strength than OPC concrete. This suggests that the existing analytical expressions for bond strength of OPC concrete can be conservatively used for calculation of bond strength of geopolymer concrete with reinforcing steel.     

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。     

Compressive strength and microstructure of fly ash based geopolymer blended with silica fume under thermal cycle

This work aims to reveal the effects of silica fume on properties of fly ash based geopolymer under thermal cycles. Geopolymer specimens were prepared by alkali activation of fly ash, which was partially replaced by silica fume at levels ranging from 0% to 30% with an interval of 10%, by mass. Microstructure, residual strength and mass loss of fly ash based geopolymer blended with silica fume before and after exposed to 7, 28 and 56 heat-cooling thermal cycles at different target temperatures of 200 °C, 400 °C and 800 °C were assessed and compared. The experimental results reveal that silica fume addition enhances strength development in geopolymer. Under thermal cycles, the compressive strength of geopolymer decreases, and the compressive strength loss, as well as the mass loss, increases with increasing target temperature. The strength loss is the same regardless of silica fume content after thermal cycles. Microstructure analysis uncovers that pore structure of geopolymer degrades after thermal cycles. The pores of geopolymer are refined by the addition of silica fume. The incorporation of silica fume optimizes the microstructure and improves the thermal resistance of geopolymer. Silica fume increases the strength of the geopolymer and even though the strength loss is the same, the strength after heat cycle exposure is still good.     

The effects of ground granulated blast-furnace slag blending with fly ash and activator content on the workability and strength properties of geopolymer concrete cured at ambient temperature

Inclusion of ground granulated blast-furnace slag (GGBFS) with class F fly-ash can have a significant effect on the setting and strength development of geopolymer binders when cured in ambient temperature. This paper evaluates the effect of different proportions of GGBFS and activator content on the workability and strength properties of fly ash based geopolymer concrete. In this study, GGBFS was added as 0%, 10% and 20% of the total binder with variable activator content (40% and 35%) and sodium silicate to sodium hydroxide ratio (1.5–2.5). Significant increase in strength and some decrease in the workability were observed in geopolymer concretes with higher GGBFS and lower sodium silicate to sodium hydroxide ratio in the mixtures. Similar to OPC concrete, development of tensile strength correlated well with the compressive strength of ambient-cured geopolymer concrete. The predictions of tensile strength from compressive strength of ambient-cured geopolymer concrete using the ACI 318 and AS 3600 codes tend to be similar to that for OPC concrete. The predictions are more conservative for heat-cured geopolymer concrete than for ambient-cured geopolymer concrete.     

碱式硫酸镁水泥耐酸腐蚀性能研究

为了研究碱式硫酸镁水泥耐酸腐蚀性能,将不同配比的水泥试样分别在柠檬酸溶液及水中浸泡不同龄期,再进行质量变化测定及抗折强度和抗压强度试验。采用XRD与SEM技术分析不同配比水泥试样浸泡于两种溶液后的物相组成和显微形貌。结果表明,掺入的矿渣和粉煤灰对碱式硫酸镁水泥具有良好的密实填充作用,降低了水泥的孔隙率,有效阻止了侵蚀介质的进入,其耐酸腐蚀性能与未掺矿渣和粉煤灰的碱式硫酸镁水泥相比有明显提升,其中,掺矿渣的碱式硫酸镁水泥耐酸腐蚀性能更优。     

Simulation of a temperature rise in concrete incorporating fly ash or slag

Granulated slag from metal industries and fly ash from the combustion of coal are among the industrial by-products and have been widely used as mineral admixtures in normal and high strength concrete. Due to the reaction between calcium hydroxide and fly ash or slag, compared with Portland cement, the hydration of concrete containing fly ash or slag is much more complex. In this paper, by considering the producing of calcium hydroxide in cement hydration and the consumption of it in the reaction of mineral admixtures, a numerical model is proposed to simulate the hydration of concrete containing fly ash or slag. The heat evolution rate of fly ash or slag blended concrete is determined from the contribution of both cement hydration and the reaction of mineral admixtures. Furthermore, a temperature rise in blended concrete is evaluated based on the degree of hydration of cement and mineral admixtures. The proposed model is verified with experimental data on the concrete with different water-to-cement ratios and mineral admixtures substitution ratios.     

碱激发改性矿粉/砒砂岩复合材料

为了实现砒砂岩的资源化利用,首先,通过碱激发法并掺入适量的矿粉将砒砂岩转变成了力学性能较好的改性矿粉/砒砂岩复合材料;然后,系统地研究了矿粉、碱激发剂掺量和龄期对改性矿粉/砒砂岩复合材料抗压强度和软化系数的影响;最后,利用SEM/EDS、FTIR和XRD分析了改性矿粉/砒砂岩复合材料的水化进程和碳化进程。结果表明:改性矿粉/砒砂岩复合材料的90d抗压强度和软化系数分别达到46.0 MPa和0.94,完全满足工程应用的需求;改性矿粉/砒砂岩复合材料主要的水化产物为C-S-H凝胶和地聚物胶体,且C-S-H凝胶存在比较严重的碳化现象;当矿粉和NaOH的掺量分别为20.0wt%和1.5wt%时,C-S-H凝胶的28d碳化率达30.1%,且碳化率随矿粉及NaOH掺量的增加而减小,但碳化率对强度几乎没有影响。改性矿粉/砒砂岩复合材料拥有良好的力学性能及耐水性。      

Influence of curing conditions on properties of high calcium fly ash geopolymer containing Portland cement as additive

This paper investigated the mechanical properties and microstructure of high calcium fly ash geopolymer containing ordinary Portland cement (OPC) as additive with different curing conditions. Fly ash (FA) was replaced with OPC at dosages of 0%, 5%, 10%, and 15% by weight of binders. Setting time and microstructure of geopolymer pastes, and flow, compressive strength, porosity and water absorption of geopolymer mortars were studied. Three curing methods viz., vapour-proof membrane curing, wet curing and temperature curing were used. The results showed that the use of OPC as additive improved the properties of high calcium fly ash geopolymer. The strength increased due to the formation of additional C–S–H and C–A–S–H gel. Curing methods also significantly affected the properties of geopolymers with OPC. Vapour-proof membrane curing and water curing resulted in additional OPC hydration and led to higher compressive strength. The temperature curing resulted in a high early compressive strength development.