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1.
KH2PO4作为磷酸钾镁水泥主要原材料,与其性能直接相关。研究了KH2PO4粒度对磷酸钾镁水泥的流动性、凝结时间、抗压强度、粘接强度、水化浆体温度和孔隙率等方面的影响。结果表明,随着KH2PO4粒径的减小,磷酸钾镁水泥的凝结时间缩短,流动度先增加后减小;材料抗压强度和粘接强度逐渐增大,中位粒径为45μm时,3h抗压强度达32 MPa,1d粘接强度达4.3MPa;KH2PO4的粒度对磷酸钾镁水泥的水化热有较大影响,对于100mm×100 mm×100mm的试块,成型后中心最高温度逐渐升高,最高可达79.5℃;随着KH2PO4粒径降低,磷酸钾镁水泥的平均孔径降低,孔隙率降低,材料致密程度相应提高。同时,粒径的减小也明显减轻了磷酸钾镁水泥所存在的"泛霜"现象。 相似文献
2.
缓凝剂硼砂对磷酸镁水泥水化硬化特性的影响 总被引:3,自引:0,他引:3
为了探讨缓凝剂硼砂(B)对磷酸镁水泥(MPC)的作用机理,测试和分析了不同掺量硼砂(B)的磷酸镁水泥(MPC)浆体的凝结时间、pH值、体系温度以及硬化体的强度和微观结构。结果表明:硼砂在一定掺量范围内对磷酸镁水泥(MPC)浆体有较明显的吸热降温促进作用和调节pH值作用,两种作用均可减慢浆体的水化反应速度且进一步影响硬化体的微观结构形貌和强度。由此推论硼砂在磷酸镁水泥(MPC)浆体中,除在MgO表面形成保护膜外,还通过降低体系温度和调节浆体pH值进而减慢水化反应速度来延缓浆体的凝结,随着硼砂(B)掺量的变化,不同因素起主导作用。 相似文献
3.
EVA乳液对磷酸镁水泥性能的影响研究 总被引:3,自引:0,他引:3
选择原材料是改善磷酸镁水泥性能的重要方法,为扩大磷酸镁水泥的应用范围,对EVA乳液改性磷酸镁水泥进行研究,结果表明,EVA乳液的掺加对磷酸镁水泥的凝结时间与流动性影响小;磷酸镁水泥的抗压与抗折强度均随着EVA乳液掺量的增大,表现出先提高后降低的趋势,但存在不同的适宜掺量;EVA乳液显著增大磷酸镁水泥的粘结强度与断裂能;微观分析表明EVA乳液不改变磷酸镁水泥水化产物类型,但改变水化反应速度,影响水化产物形貌,其中MgNH4PO4·6H2O主要以柱状存在,并且结构更加致密。 相似文献
4.
利用磷酸镁水泥(Magnesium potassium phosphate cement,MPC)对模拟α-高放核废液(HLW)进行固化,研究温度对固化体力学性能、物相组成、微观形貌及核素Cs~+浸出率的影响。BET、XRD、SEM及AAS等测试结果表明,室温下MgO、KH2PO4与高放核废液反应形成致密结构;随着温度的升高,固化体脱水,400℃时孔道结构增多,平均孔径增大,抗压强度降低,Cs~+浸出率增加;温度继续升高,磷酸镁水泥烧结陶瓷化,平均孔径逐渐减小,抗压强度增大;900℃时固化体表现出良好的陶瓷结构特征,晶粒完全熔融,晶粒间没有明显界线,Cs~+的28d浸出率为7.21×10~(-6) g/(cm~2·d)。不同温度下高放核废液的磷酸镁水泥固化体核素Cs~+的浸出率均能达到玻璃固化体的性能要求,表明磷酸镁水泥用于固化高放核废液具有明显优势。 相似文献
5.
添加不同体积比的玻璃纤维,按照一定比例配制玻璃纤维增强磷酸镁水泥。研究了玻璃纤维增强磷酸镁水泥的抗压强度、抗折强度以及耐水性,并采用电镜扫描的方法对其微观结构进行了观察。研究结果表明,玻璃纤维对磷酸镁水泥的抗压强度和抗折强度都有一定贡献,其中纤维的最佳体积掺量约为2.5%,但超过最佳掺量后,抗压和抗折强度都有所降低。另外,实验结果还表明,稍过量的玻璃纤维能够暂时"包裹"未反应基材,可能在浸水环境中发生又一轮反应,从而抵消因浸水造成的强度损失,这可能是一种改善磷酸镁水泥耐水性的新方法。此外,本工作提供了与实验结果一致的纤维增强机理的可能解释。 相似文献
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通过磷酸镁水泥体系和普通水泥中的钢筋锈蚀的对比实验,利用电化学工作站,分析钢筋锈蚀过程中的开路电位和极化曲线,研究了磷酸镁水泥体系的钢筋锈蚀行为。同时利用光学显微镜观察了不同龄期的磷酸镁水泥中钢筋的锈蚀形貌。结合磷酸镁水泥水化过程中pH值的变化和极化曲线理论深究了磷酸镁水泥体系抗钢筋锈蚀能力的机理。研究表明,磷酸镁水泥具有很强的抗钢筋锈蚀能力。磷酸镁水泥体系中的钢筋锈蚀行为虽然存在,但是其发展非常缓慢。磷酸镁水泥pH值的变化以及弱碱环境中磷酸铵金属络合物的形成是磷酸镁水泥抗钢筋锈蚀能力的控制因素。 相似文献
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为开发磷酸钾镁水泥(MKPC)砂浆的喷涂和灌缝工艺,研究了不同矿物掺合料的自流平磷酸钾镁水泥砂浆力学性能、体积变形、水化温度和水稳定性及其影响规律.分析了水化产物的物相组成和微观形貌对磷酸钾镁水泥砂浆性能的影响及作用机理.研究结果表明:粉煤灰和偏高岭土由于其材料特性,不会降低MK P C砂浆的流动性,而硅灰比表面积过大,吸水量较多导致浆体流动性降低.偏高岭土活性较高可与磷酸盐发生反应生成磷酸铝类凝胶填补晶体间的孔隙,可显著提高抗压强度,但水化过程后期出现微膨胀使粘结抗折强度倒缩;掺硅灰的MK P C硬化浆体体积稳定性最佳,故粘结抗折强度最高.微观分析表明,矿物掺和料起到物理填充作用和作为活性成分参与水化反应以提高水化程度,可改变MK P C硬化浆体的晶体尺寸和微观形貌,使结构更加致密. 相似文献
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以十八烷(OC)为相变材料、膨胀石墨(EG)为支撑结构制备出OC质量含量为90%的十八烷/膨胀石墨复合相变储热材料( OC/EG-PCM).将OC/EG-PCM掺入到普通硅酸盐水泥中,制备出了相变材料质量含量分别为2%、5%、7%、10%的标准储热水泥立方体(70.7×70.7×70.7 mm3)和储热水泥板(10×100×l00 mm3),测量了储热水泥立方体的表观密度和抗压强度,以及储热水泥板的导热系数和储热性能.结果表明,随着OC/EG-PCM质量含量的增加,储热水泥立方体的表现密度和抗压强度逐渐下降,储热水泥板的导热系数也近似于线性减小,储热水泥板的上下表面温差则逐渐增大.当OC/EG-PCM的质量含量为10%时,储热水泥立方体的抗压强度大于10MPa,储热水泥板的上下表面温差大于4.0℃. 相似文献
12.
Hsu HC Kikuchi H Yen SK Nishiyama M 《Journal of materials science. Materials in medicine》2005,16(9):821-825
The properties of several different investments were investigated including phosphate bonded, magnesia bonded, and alumina cement investments.Measurements included the setting expansion, thermal expansion, and compressive strength of investments, as well as the tensile strength, elongation, Vickers hardness (VHN) and surface roughness of titanium castings. For phosphate bonded investment, the setting expansion after being mixed with its own mixing solution was 2.10%, which was larger than the other investments; the thermal expansion was −0.25% at 200 ^∘C, the compressive strength 14 and 5 MPa after heating. For titanium cast in phosphate bonded investment, the hardness on its top surface was 655 Hv, the tensile strength was 379 MPa, the elongation was 19.4%, and the surface roughness was 2.29 μ m. Athough the thermal expansion of phosphate bonded investment is small, the setting expansion is large enough to compensate for the shrinkage of titanium castings. As its thermal expansion at T ≥ 600∘C was constant and its heating-cooling cycle was almost reversible, these two properties can reduce the thermal shock and thus avoid cracking of the investment. 相似文献
13.
Hsu HC Kikuchi H Yen SK Nishiyama M 《Journal of materials science. Materials in medicine》2007,18(4):605-609
The properties of several different investments were investigated including phosphate bonded, magnesia bonded, and alumina
cement investments. Measurements included the setting expansion, thermal expansion, and compressive strength of investments,
as well as the tensile strength, elongation, Vickers hardness (VHN) and surface roughness of titanium castings. For phosphate
bonded investment, the setting expansion after being mixed with its own mixing solution was 2.10%, which was larger than the
other investments; the thermal expansion was −0.25% at 200°C, the compressive strength 14 and 5 MPa after heating. For titanium
cast in phosphate bonded investment, the hardness on its top surface was 655 Hv, the tensile strength was 379 MPa, the elongation
was 19.4%, and the surface roughness was 2.29 μm. Athough the thermal expansion of phosphate bonded investment is small, the setting expansion is large enough to compensate
for the shrinkage of titanium castings. As its thermal expansion at T ≥ 600°C was constant and its heating-cooling cycle was almost reversible, these two properties can reduce the thermal shock
and thus avoid cracking of the investment. 相似文献
14.
Residual strength properties of sodium silicate alkali activated slag paste exposed to elevated temperatures 总被引:1,自引:0,他引:1
The residual compressive strength behavior of alkali activated slag paste (AASP) after temperature exposures up to 1,200°C
was investigated. Strength loss of approximately 60% occurred between 100 and 200°C and a further strength loss in the order
of 30% at 800°C. Total loss of strength occurred at 1,200°C. Thermogravimetric studies (TGA/DTG) verified AASP contained no
Ca(OH)2 which governs the chemical mechanism of strength loss for ordinary Portland cement (OPC) and blended slag cement pastes.
However, the TGA results showed that AASP had a higher water loss than the other binders between 100 and 200°C and higher
thermal shrinkage as indicated by the dilatometry studies. The high thermal shrinkage led to a differential thermal shrinkage
gradient within the AASP and induced micro stresses and cracking which was more prominent for larger samples. Differential
thermal shrinkage caused by the higher thermal shrinkage of the AAS material was concluded as the mechanism which gives lower
residual strength in AASP compared to OPCP. 相似文献
15.
The present study describes the behaviour of concrete as well as fly ash concrete when subjected to varying number of high temperature heating cycles. A Concrete mix (1:2.37:2.98) with 340 kg/m3 cement and w/cm ratio 0.45 was prepared. Cement was replaced by varying percentages (0%, 20%, 40%, 50% and 60%) of fly ash by weight of cement. The concrete was subjected to a constant temperature of 200°C for 7, 14, 21 and 28 heating cycles. One heating cycle corresponds to 8 h heating and subsequent cooling in 24 h. Subsequently the effect of temperature on the properties of the concrete was investigated and compared with that of the properties of unheated concrete. The compressive strength of plain as well as fly ash concrete increased when it was subjected to thermal cyclic loads. Moreover, the compressive strength increased with an increase in number of heating cycles. Thermal conductivity of concrete was found to decrease with an increase in the fly ash content. 相似文献
16.
This paper studies the physical properties, compressive strength and drying shrinkage of multi-blended cement under different curing methods. Fly ash, ground bottom ash and undensified silica fume were used to replace part of cement up to 50% by weight. Specimens were cured in air at ambient temperature, water at 25, 40 and 60 °C, sealed with plastic sheeting for 28 days. The results show that absorption and volume of permeable pore space (voids) of blended cement mortars at 28 day under all curing methods tend to increase with increasing silica fume replacement. The compressive strength of blended cement with fly ash and bottom ash was lower than that of Portland cement control at all curing condition while blended cement with silica fume shows higher compressive strength. In addition, the compressive strength of specimens cured with water increased with increasing curing temperature. The drying shrinkage of all blended cement mortar cured in air was lower than that of Portland cement control while the drying shrinkage of blended cement mortar containing silica fume, cured with plastic sealed and water at 25 °C was higher than Portland cement control due to pore refinement and high autogenous shrinkage. However, the drying shrinkage of blended cement mortar containing SF cured with water at 60 °C was lower than that of Portland cement control due to lower autogenous shrinkage and the reduced microporosity of C–S–H. 相似文献
17.
M. P. Ginebra M. G. Boltong E. FernÁndez J. A. Planell F. C. M. Driessens 《Journal of materials science. Materials in medicine》1995,6(10):612-616
The effect of additives and temperature on setting time, swelling time and compressive strength of a previously developed apatitic calcium phosphate cement was investigated. Setting was faster at body temperature than at room temperature. Early contact with aqueous solutions resembling blood and other body fluids had no effect. Deliberate additions of soluble carbonates, pyrophosphate or magnesium salts to the cement powder retarded or even inhibited setting. However, additions of calcium pyrophosphate, -tertiary calcium phosphate or sintered hydroxyapatite to the cement powder in amounts up to 10% had no effect on the cement properties. Several organic substances were used as additives. They all retarded the setting and decreased the strength of the cement considerably. 相似文献
18.
为了研发水泥稳定碎石的无机类复合早强剂,首先将三乙醇胺、硫酸钠分别制成单掺早强剂,以不同比例加入混合料中,测试其1 d龄期下的抗压强度,从两种早强剂中分别选取强度提高最大的4个比例,平行相交混合,配制出16种配比的三乙醇胺-硫酸钠复合早强剂,将不同配比的复合早强剂添入水稳材料中,对比它们1 d的抗压强度,选择出3种表现最好的配比(CN 1.0%+NS 2.0%,CN 0.75%+NS 2.0%,CN 1.0%+NS 1.5%)继续后续实验。其次,研究上述3种配比的早强剂对水泥稳定碎石抗压强度、干缩应变、失水量、温缩应变的影响。结果表明,掺入自配复合早强剂后,对水泥稳定碎石各个龄期的强度均有提高作用,同时降低了混合料的失水量,干缩应变。当早强剂的配比为三乙醇胺1%加硫酸钠2%时,水泥的强度提高最为明显,收缩变形也最好,其在1 d、7 d和28 d龄期下的抗压强度分别提高66%、18%和16%,抗压强度与龄期的关系拟合为Y=A+B×ln(X+C)曲线,干缩应变、失水量也有所下降,温缩性能得到改善。故试验中配制的复合早强剂可以实现早强效果,并可提高水泥稳定碎石的抗收缩能力。 相似文献
19.
Moseke C Saratsis V Gbureck U 《Journal of materials science. Materials in medicine》2011,22(12):2591-2598
Up to now magnesium phosphate cements are mainly being utilized in wastewater treatment due to their adsorptive properties.
Recently they also have been shown to have a high potential as degradable biocements for application as replacement materials
for bone defects. In comparison to degradable calcium phosphate cements they have the advantage of setting at neutral pH,
which is favorable in biological environment. In this study two parameters of the cement composition, namely powder-to-liquid
ratio (PLR) and citrate content, were varied in order to optimize the injectability properties of the cement paste and the
mechanical properties of the reaction product. These properties were determined by means of testing setting time and temperature,
paste viscosity, and injectability as well as phase composition and compressive strength of the set cements. Best results
were obtained, when the cements were prepared with a PLR of 2.5 and a binder liquid consisting of an aqueous solution of 3 mol/l
diammonium hydrogen phosphate and 0.5 mol/l diammonium citrate. 相似文献
20.
In this study, the effect of incorporating shrinkage reducing admixtures (SRA) and/or wollastonite microfibers on the early-age shrinkage behavior and cracking potential of ultra-high performance concrete (UHPC) was explored. Wollastonite microfibers were added at rates of 0%, 4% and 12% as partial volume replacement for cement, while SRA was added at 1% and 2% by cement weight. Results show that the reinforcing effect induced by wollastonite microfibers mitigated the reduction in compressive strength induced by SRA. Addition of wollastonite microfibers to SRA mixtures did not impart a significant change in the measured free shrinkage strain, while it enhanced the cracking resistance compared to that of mixtures incorporating SRA alone. Moreover, adding wollastonite microfibers reduced the leaching of SRA from concrete under submerged conditions, thus leading to higher efficiency of SRA in reducing shrinkage. Partially replacing cement with natural wollastonite microfibers also leads to a reduction in the cement factor, which represents economic and environmental benefits. 相似文献