碱矿渣复合水泥--放射性废物固化基材力学性能的研究(二)

3 结果与讨论3.1 热活化高岭土掺量对强度的影响 C—S—H凝胶具有一定的离子吸附和交换能力,尤其在铝部分取代了硅之后。在碱矿渣水泥中掺入热活化高岭土来提高体系的铝含量,为该水泥浆体形成富铝、低碱C—S—H凝胶和沸石类水化产物提高了物质条件。热活化高岭土掺量对碱矿渣水泥强度的影响见图1(激发剂为工业水玻璃,模数为1.5,掺量为5％以Na_2O计,另加2％的工业Na_2CO_3,在相对湿度大于90％的湿空气中养护,下同)。     

模拟高旄生废物碱矿渣水泥基固化体的性能研究

研究了用初压成型和振动成型工艺制造的碱矿渣水泥固化体的某些性能。结果表明，用碱矿渣水泥基材料固化模拟高放射性废物是可行的。采用初压成型工艺制造的碱矿渣水泥固化体，２８ｄ抗夺强度达１１７．３ＭＰａ，孔隙率为９．６４％，且固化还具有良好的抗冲击性能和较好的核素浸出率。     

模拟高放射性废物碱矿渣水泥基固化体的性能研究

研究了用初压成型和振动成型工艺制造的碱矿渣水泥固化体的某些性能。结果表明，用碱矿渣水泥基材料固化模拟高放射性废物是可行的。采用初压成型工艺制造的碱矿渣水泥固化体，２８ｄ抗压强度达１１７．３ＭＰａ，孔隙率为９．６４％，且固化体还具有良好的抗冲击性能和较低的核素浸出率。     

水泥及其复合体系固化放射性核废物研究现状

水泥优良的物理化学性能使其在放射性废物固化领域应用广泛。介绍了水泥固化的机理和对水泥固化体的基本性能要求,并综述了硅酸盐水泥、碱激发胶凝材料、硫铝酸盐水泥和磷酸镁水泥在放射性废物固化领域的研究进展。对水泥基固化材料的发展具有一定的借鉴意义。     

模拟高放废物碱矿渣水泥固化体抗冲击性能的研究

研究了模拟高放废物碱矿渣水泥固化体的抗冲击性能。实验结果表明：固化体的固化工艺对其抗冲击性能有很大影响，水泥固化体的抗冲击性能优于玻璃固化体。     

水泥固化高放射性废物的研究进展

近十几年来，许多国家正在加速研究和开发高放射性废物的水泥固化技术，并取得了较大进展。本文主要对该课题的研究现状及核素离子的固化机理等方面进行了评述。     

高放废液碱矿渣水泥固化体中矿渣反应程度研究

出于安全的考虑，高诳废液碱矿渣水泥固化体应该具有较高的热力学稳定性，要求在一个不太长的时间内使处于介稳态的矿渣玻璃体完全水化转化为热力学稳定的水化产物。为此分别用水杨酸甲醇－丙酮萃取法和非蒸发水法估测碱矿渣水泥中的矿渣反应率，用非蒸发水法结合ＤＴＡ法估测固化体中的矿渣反应率。     

水泥固化高放射性废物的科学基础

与玻璃法、陶瓷法相比,水泥法具有原材料易得、工艺简单等优点。本文综述了国内外近几年来用水泥固化放射性废物的最新研究成果,并指出了用水泥来固化高放射性废物存在的问题及发展方向。     

放射性废物水泥固化的理论基础,研究现状及对水泥化学研究的思考

水泥具有优良的物理、化学及力学性能，是固化放射性废物的良好基体材料，本文概要介绍水泥作为固化材料的科学理论依据，以及固化处理方面的研究应用现状，并对水泥化学学科的发展提出初浅的认识。     

碱矿渣水泥固化模拟高放射性废液中Cs+的作用机理

研究了模拟高放射性废液在不同的预处理工艺条件下,加入NiSO4和K4[Fe(CN)6]后,碱矿渣水泥固化其废液中Cs+的作用机理,及其预处理工艺对废液中Cs+交换容量及固化体中Cs+浸出率的影响.实验表明废液在H1预处理工艺下,即在脱硝后,pH值为0.2时,按摩尔比n(Cs+)∶n(Ni2+)∶n([Fe(CN)6]4-)为1∶1∶1加入NiSO4和K4[Fe(CN)6],然后碱化至pH=12,采用GB7023-86方法,计算得到在25 ℃,第42 d的固化体中,Cs+浸出率为未经预处理的1/790,达到10-7cm@d-1.采用MCC-I方法,90 ℃,第28 d的固化体中,Cs+浸出率为未经预处理的1/385,也达到10-6 g@cm-2@d-1.并通过X射线衍射、扫描电镜及能谱分析、差热及热重分析等方法分析并验证了固化结果经H1预处理工艺后,废液中大部分Cs+与NiSO4, K4[Fe(CN)6]生成难溶固溶体Cs2Ni[Fe(CN)6]和Cs4Ni4[Fe(CN)6]3 而被固化体固封持留.     

(Micro)-structural comparison between geopolymers, alkali-activated slag cement and Portland cement

Concurrently to research conducted on ordinary Portland cement (PC), new types of binders were developed during the last decades. These are formed by alkali-activation of metakaolin or ground-granulated blast furnace slag (GGBFS) and are named, respectively, geopolymers (GP) or alkali-activated slag (AAS). Four different cementitious materials were synthesised: PC, AAS, GP, and a mix GP-AAS and fully compared about their compositions and (micro)-structures.

X-ray diffraction has revealed the presence of semi-crystalline CSH gel binding phase in PC while AAS, GP and GP-AAS are nearly amorphous. Progressive structural changes have been observed between the different samples by means of infrared spectroscopy, ²⁹Si and ²⁷Al magic-angle-spinning nuclear magnetic resonance spectroscopy: there is a polymerisation extent of the (alumino)-silicate framework from PC [SiQ¹ and SiQ² units] to AAS [SiQ² and SiQ²(1Al) units] and finally to GP [SiQ⁴(2Al) and SiQ⁴(3Al) units]. Scanning electron microscopy has shown that GP is a homogeneous matrix while the other materials are composites containing GGBFS grains surrounded by a binding matrix. Energy dispersive X-ray EDX analyses (line scans) have shown the absence of formation of any specific phase at the matrix-grains interfaces.     

石膏掺量对碱激发矿渣水泥砂浆性能的影响

研究了石膏掺量对碱矿渣水泥砂浆流动性、力学性能、干缩及水化性能的影响。结果表明,掺入1%～5%的石膏,碱激发矿渣水泥砂浆的流动度下降;石膏掺量在2%以内时,可提高砂浆的强度,但当掺量超过2%后,强度开始下降;石膏掺量在1%～5%范围内递增时,砂浆的干缩率随之降低。交流阻抗谱分析表明,在碱矿渣砂浆中掺入1%～5%的石膏时,Nyquist图形从30 min～1 d的非Randles图形逐渐过渡到3～28 d的准Randles曲线,表明砂浆内部的电化学反应与其水化反应相匹配,交流阻抗参数R_1、R_2在3 d后随着石膏掺量增大而增大,表明石膏在一定程度上促进了砂浆的水化。     

碱活性磷渣掺量对水泥浆体性能和结构的影响

本文研究了经混合碱激发活性的磷渣,以不同比例取代水泥制得碱激发矿渣水泥浆体的凝结性能和抗压强度,并用扫描电子显微镜观察其硬化浆体的微观结构。研究表明:随着碱活性磷渣掺量的增加,浆体的凝结时间延长,各龄期抗压强度均下降,其中早期强度降低幅度较大,后期强度降低不明显。当碱活性磷渣掺量为30%时,浆体28d强度和纯水泥浆体的最接近。碱活性磷渣的掺入能有效地改善硬化浆体水化后期的微观结构,主要起到活化作用。     

大体积浇注碱矿渣水泥中低放废液固化研究

用高掺量沸石碱矿渣水泥对模拟中低放废液进行大体积浇注固化,废物包容量(以硝酸盐计)为13 5%,水固比为0 34,水泥浆体具有良好的工作性。在去离子水中,固化体Cs+、Sr2+第42d浸出率(GB7023 86、25℃)为2 5×10-5、1 3×10-6cm·d-1,整个浸出周期累积浸出百分数为0 7%和0 2%;MCC 1P法90℃28dCs+、Sr2+浸出率为3 1×10-4、2 2×10-5g·cm-2·d-1,浸出百分数为3 5%、0 2%;150℃时为5 6×10-4、3 0×10-5g·cm-2·d-1,浸出百分数为6 2%、0 3%,在盐卤溶液中浸出率相差不大,表明固化体能有效地持留Cs+、Sr2+,其他性能均符合大体积浇注的要求。     

Comparison studies between cement and cement-kaolinite properties for incorporation of low-level radioactive wastes

Comparison between the properties of cement and cement mixed with 7.5% kaolinite was performed to choose the most suitable matrix to incorporate radio-active wastes. The cement-kaolinite mixtures were prepared as uncured, cured, and heated specimens. The physical properties of the cement-kaolinite mixture, namely density, porosity, and water absorption percent, were determined. Compressive strength, infrared spectra, thermal analysis, and the effect of gamma rays on the samples were studied. The studies were extended to the cement-kaolinite mixture in the presence of some chemical additives at different concentrations. Leachability of radioactive isotopes from the cement-kaolinite mixture was measured as a function of time. The physical and mechanical properties of cement were decreased in the presence of 7.5% kaolinite, whereas ¹³⁷Cs and ⁶⁰Co were less leached from the cement-kaolinite mixture.     

SHS of mineral-like ceramics for immobilization of radioactive nuclear wastes

Synthetic analogs of titanate ceramics (perovskite and zirconolite) designed for use as a matrix for immobilization of high-level nuclear fuel reprocessing wastes (HLW). Such ceramics have been prepared by SHS method from a mixture of titanate ceramics and non-radioactive model oxides. Synthesis conditions have been optimized. The synthesized low-porosity cylindrical compacts exhibited a high strength and low rate for leaching Cs, Sr, Y, Ce, and La in bidistilled water. The phase composition and microstructure of synthesized products have been characterized. The immobilization of Cs was found to be accompanied by a marked loss of this element. The text was submitted by the authors in English.     

Effect of blended inorganic salts containing negative hydration ions on hydration and properties of alkali-activated slag cement

Water glass (WG) is generally considered to be the most effective activator to prepare alkali-activated slag (AAS) cement in terms of strength and durability. However, the rapid setting and hardening of WG activated slag results in rapid loss of fluidity of AAS concrete mixture, which limits its engineering application. In the paper, the effect of blended inorganic salts containing negative hydration ions on the fluidity, setting time and mechanical strength of AAS cement was studied. The hydration process and hydration products were used to explore the action mechanism. Ba(NO₃)₂ greatly delayed the hydration of AAS cement. The four inorganic salts (KCl, KNO₃, KBr and NaCl) blended with a small amount of Ba(NO₃)₂ can improve both the initial fluidity and fluidity retention, and a wide setting time range can be obtained to meet engineering requirements. The compressive strength decreased with the increase of inorganic salts. The incorporation of inorganic salt did not change the composition of the main hydration products. Considering the fluidity required by construction, mechanical properties and the durability of structure, it is recommended to add 4%–5% KBr or KNO₃ blended with no more than 0.2% Ba(NO₃)₂ into AAS cement.     

Effect of geothermal waste on strength and microstructure of alkali-activated slag cement mortars

Mortars of blast furnace slag replaced with 10% of a geothermal silica waste were cured for 90 days. The binder was activated by 6 wt.% Na₂O equivalent of NaOH and water glass. The presence of the silica enhanced the formation of hydration products as shown by nonevaporable water (NEW) results. Backscattered electron images indicated that the microstructures of blended slag had less porosity than those of neat slag mortars and the interfacial zone between aggregate and hydration products was dense and of homogeneous composition similar to the matrix of hydration products. The main hydration products were C-S-H and for NaOH a hydrotalcite type phase was found as finely intermixed with the C-S-H.     

矿渣-钢渣复合水泥的性能研究

试验利用矿渣和钢渣作为配制复合水泥的辅助性胶凝材料,研究了矿渣、钢渣细度和复合比例对复合水泥强度的影响,并从颗粒堆积和复合胶凝效应的角度探讨了矿渣-钢渣在复合水泥中的作用机理。试验结果表明：在矿渣与钢渣组成的复合体系中,矿渣细度决定了复合水泥的强度,矿渣越细,复合水泥强度越高;在辅助性胶凝材料掺量一定的情况下,矿渣占的比例越高,复合水泥的强度越高;在适宜的复合比例下,用矿渣和钢渣混合配制的复合水泥28d抗压强度高于纯水泥的28d抗压强度。