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电石渣作为一种工业废渣,其碱度较高,综合利用率较低。为了解决过量的电石渣,利用电石渣的强碱性,研究了电石渣对矿渣胶凝体系的碱激发性能。利用电石渣碳化反应可生成碳酸钙的特性,探索了不同碳化制度对电石渣碱激发矿渣胶凝体系的性能影响规律。结果表明:大掺量电石渣对矿渣胶凝材料有很好的碱激发效果,生成大量的C-(A)-S-H凝胶,而复掺粉煤灰和偏高岭土胶凝体系性能最佳;电石渣-矿渣复合胶凝体系经过不同碳化制度处理后,胶凝体系力学性能有效提升;使用CO2气体作为外部碳化源,材料基体表层生成致密结构,基体力学性能提升;使用尿素作为内部碳化源,基体内部碳化均匀,胶凝体系力学性能提升。 相似文献
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碱激发镁渣胶凝材料的研究 总被引:1,自引:0,他引:1
通过改变碱掺量,碱激发剂种类,水玻璃的模数,研究了碱激发剂对镁渣复合胶凝材料性能的影响。表明加入一定的激发剂能显著提高了镁渣的活性,也提高了镁渣胶凝材料的性能;凝结时间随着碱掺量增加而变短,水玻璃的激发效果要优于KOH,NaOH;模数为1.2水玻璃在掺量为10%的激发作用最好,胶凝材料力学性能也最强。 相似文献
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为探究矿渣、粉煤灰及电石渣的资源化利用,以电石渣作为碱激发剂,研究了矿渣-粉煤灰复合胶凝材料的水化产物组成及强度特征。采用X射线衍射(XRD)、傅里叶变换红外光谱(FTIR)、热重-差示扫描热(TG-DSC)、扫描电子显微镜及能谱(SEM-EDS)等微观测试技术,分析了复合胶凝材料的晶体结构、热化学性质以及微观形貌等特性,研究了电石渣激发矿渣-粉煤灰复合胶凝材料的作用机制。结果表明:电石渣作为碱激发剂时能为矿渣-粉煤灰复合胶凝材料提供初始水化所需要的强碱环境,驱动矿渣和粉煤灰发生水化反应。随着矿渣掺量的增加,复合胶凝材料的强度发展呈先增加后减小的变化趋势,在粉煤灰与矿渣掺量质量配比为4∶6、外掺电石渣质量分数为4%时,复合材料浆体经4 d常温养护+32 h高温蒸汽养护后抗压强度达到25.9 MPa;矿渣-粉煤灰复合胶凝体系中水化产物分布不均,主要组成为水化硅酸钙、水化铝酸钙、水化硅铝酸钙等凝胶。电石渣作为矿渣-粉煤灰体系的碱激发剂使用时效果良好。 相似文献
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概述了碱激发胶凝材料的历史沿革、分类和碱矿渣-粉煤灰胶凝材料的研究进展。将碱激发体系由传统的中、高碱度范围延伸至低碱度范围,提出了碱激发矿渣-粉煤灰胶凝材料水化机理模型的分类方法,及其胶凝材料的定位、存在问题和今后的研究方向。 相似文献
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This paper presents the experimental results and prediction model for the autogenous shrinkage of concrete made with various water-to-cementitious materials ratios (w / cm) ranging from 0.27 to 0.42 and granulated blast-furnace slag (BFS) in the range of 0% to 50% by mass of the total cementitious materials. Test results showed that BFS concrete exhibited greater autogenous shrinkage than ordinary concrete with no BFS with the same w / cm, and that the higher the BFS content, the greater the autogenous shrinkage. At the same content of BFS, the increasing rate of autogenous shrinkage is affected by the w / cm; the lower the w / cm, the smaller the increasing rate of autogenous shrinkage. Based on the test results, a prediction model for autogenous shrinkage was proposed. In particular, an effective autogenous shrinkage that is a realistic shrinkage strain responsible for stress development was introduced in the model. It was determined by taking into account the characteristics of ultrasonic pulse velocity evolution in concrete. This prediction method for autogenous shrinkage may be effectively used to estimate the stress induced by autogenous shrinkage. 相似文献
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This paper presents results of a study on chemical acceleration of a neutral granulated blast-furnace slag activated using sodium carbonate. As strength development of alkali-activated slag cements containing neutral GBFS and sodium carbonate as activator at room temperature is known to be slow, three accelerators were investigated: sodium hydroxide, ordinary Portland cement and a combination of silica fume and slaked lime. In all cements, the main hydration product is C–(A)–S–H, but its structure varies between tobermorite and riversideite depending on the accelerator used. Calcite and gaylussite are present in all systems and they were formed due to either cation exchange reaction between the slag and the activator, or carbonation. With accelerators, compressive strength up to 15 MPa can be achieved within 24 h in comparison to 2.5 MPa after 48 h for a mix without an accelerator. 相似文献
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The influence of ground granulated blast-furnace slag (GGBS) chemical variability on phase formation in sodium hydroxide-activated GGBS pastes has been investigated using X-ray total scattering and subsequent pair distribution function (PDF) analysis. Crystalline phase identification based on reciprocal space analysis reveals that despite large chemical variations in the neat GGBSs the secondary reaction products are quite similar, with the majority of pastes containing a hydrotalcite-like phase. However, PDF analysis reveals considerable differences in short range atomic ordering of the main calcium-sodium aluminosilicate hydrate (C-(N)-A-S-H) gel phase in the pastes. Quantitative analysis of these local structural differences in conjunction with published PDF data identifies the important role calcium plays in dictating the atomic structure of disordered silicate-rich phases in cementitious materials. This study serves as a crucial step forward in linking GGBS chemistry with phase formation in alkali-activated GGBS pastes, revealing key information on the local structure of highly-disordered cementitious materials. 相似文献
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The morphology of outer-product (Op) C-S-H in 20-year-old slag-cement pastes appeared in most blends to be finer than at younger ages. The Ca/Si and Ca/(Si + Al) ratios of the Op C-S-H decreased with increasing slag content, and the Al/Si ratio increased. The Ca/Si ratio of C-S-H in the slag-containing pastes was lower at 20 years than at 14 months and the amount of Ca(OH)2 was reduced indicating that additional slag must have reacted. The mean aluminosilicate chain length of the C-S-H was very long in all the samples and would be expected to have increased with age. The TEM-EDX and NMR data are consistent with nanostructural models for C-S-H. The Mg/Al ratio of the Mg-Al layered double hydroxide phase (LDH) was lower at 20 years than at 14 months in all cases except for the neat slag paste; aluminium hydroxide-based structure might be interstratified with those of the Mg-Al LDH. 相似文献
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Study on the flexural fatigue performance and fractal mechanism of concrete with high proportions of ground granulated blast-furnace slag 总被引:1,自引:0,他引:1
Li-Ping Guo Wei Sun Ke-Ren Zheng Heng-Jian Chen Bo Liu 《Cement and Concrete Research》2007,37(2):242-250
The flexural fatigue performance of concretes with 50% and 80% proportions of ground granulated blast-furnace slag (ab. ggbs) by mass of total cementitious materials in concrete has been investigated. The effect of different proportions of ggbs on concrete fatigue performance was investigated by experiments and was estimated by the fractal theory from five aspects, i.e. the 1D fractal dimensions of critical surface cracks, the prediction area of fractured profiles, the ratios between the area of debonded coarse aggregates and the Euclidean area of fractured profile, fracture energy modified by fractal theory, and the brittleness index. In order to estimate these fractal parameters on-line, the grey model GM (1, 1) was employed. Those experimental and numerical results show that the brittleness of concrete is impaired by the incorporation of ggbs, which contribute to higher fracture energy and more complicated characteristics on fractured profiles of concrete. Therefore, potential hydration and pozzolanic effect of ggbs in matrix prolong the fatigue life of concrete comparing with those of concrete without them. The fractal theory and grey model are novel approaches to present quantitatively the flexural fatigue performance of concrete. 相似文献
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Marianne E. Gaze Michael A. Smith 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1978,28(11):687-698
One method proposed for utilisation of high-magnesia Portland cements involves the addition of active siliceous admixtures such as fly ash or ground granulated blastfurnace slag. This addition enables otherwise unsound cements to pass the ASTM autoclave test (C151–74a) for expansion of Portland cement. Cements were made from an OPC, magnesia (2 and 3%) and varying proportions (0–70%) of fly ash or ground granulated slag. The expansions of pastes made from the cements stored at 50°C were measured over periods of 3 and 4 years, respectively. The cements were also subjected to the ASTM autoclave test. The results of the autoclave test support the view that expansion in the autoclave is to some extent related to the strength of the matrix, and best results were obtained with CaO:SiO2 ratios of about 1.25 corresponding to formation of large quantities of 1.1 nm tobermorite. However, it has been shown that even a high strength matrix cannot stabilise too much free magnesia either in the autoclave or at 50°. Slag was less effective than fly ash in producing a reduction in autoclave expansion although results at 50° were comparable. This work on cements with added periclase suggests that the stabilisation of ‘normal’ high magnesia cements, in both the autoclave and under more normal conditions, with any practical level of stabiliser addition, will depend on factors such as the ‘blocking effect’ described by Rosa, and the dilution effects of stabiliser addition being sufficient to reduce the effective free magnesia content to the small amount which the strength of the matrix can control. 相似文献
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Sun-Jae Kim Seong-Gyu Seo Sang-Chul Jung 《Korean Journal of Chemical Engineering》2010,27(6):1901-1905
High purity nano silica was synthesized using acid treatment and surface modification from blast-furnace slag generated in the steel industry. Blast-furnace slag was treated with nitric acid to extract high-purity insoluble silica. Nano silica was then produced using filtration and surface modified by cation surfactant-Cetyltrimethyl Ammonium Bromide (CTAB). The Zeta potential of silica was tested under various alkaline conditions. Synthesized silica remained electronegative throughout the pH range tested and the number of hydroxyl groups existing on the silica surface was highest when the pH was 9. The size of silica particles was smallest when the modification temperature was 60 °C. The average size of silica particles modified with 3 wt% CTAB was 107.89 nm, while the average size of unmodified silica was 240.38 nm. After extracting silica, pH of the remaining solution was adjusted by adding CaO and then highpurity calcium nitrate crystals were extracted using solubility difference. It was found experimentally that enriching the solution to a high specific gravity (1.63–1.65) before crystallization is preferable for efficient calcium nitrate recovery. 相似文献
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A study on the alkali-aggregate reaction in high-strength concrete with particular respect to the ground granulated blast-furnace slag effect 总被引:1,自引:0,他引:1
Young-jin Kwon 《Cement and Concrete Research》2005,35(7):1305-1313
The alkali-aggregate reaction (AAR) in high-strength concrete and the effect of ground granulated blast-furnace slag (GGBFS) were studied in this paper. From the results of this study, following conclusions can be drawn:
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- In high-strength concrete, because of high alkali content, the possibility of alkali-aggregate reaction is much higher than conventional concrete.
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- The occurrence of large expansion can be prevented by using nonreactive aggregate, which has been judged according to the mortar bar and chemical method's as specified in JIS A 5308, in high-strength concrete.
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- The replacement of cement by 30% of blast-furnace slag and using low-alkali cement can prevent the alkali-aggregate reaction from causing large expansion in high-strength concrete.
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The strength development of mortars containing ground granulated blast-furnace slag (ggbs) and portland cement was investigated. Variables were the level of ggbs in the binder, water-binder ratio and curing temperature. All mortars gain strength more rapidly at higher temperatures and have a lower calculated ultimate strength. The early age strength is much more sensitive to temperature for higher levels of ground granulated blast-furnace slag. The calculated ultimate strength is affected to a similar degree for all ggbs levels and water-binder ratios, with only the curing temperature having a significant effect. Apparent activation energies were determined according to ASTM C1074 and were found to vary approximately linearly with ggbs level from 34 kJ/mol for portland cement mortars to around 60 kJ/mol for mortars containing 70% ggbs. The water-binder ratio appears to have little or no effect on the apparent activation energy. 相似文献