Stoichiometry of Slag Hydration with Calcium Hydroxide

The stoichiometry of the reaction between ground granulated blast furnace slag (GGBFS) having an empirical formula of C_7.88S_7.39M₃A and calcium hydroxide (CH) was investigated. Scanning electron microscopy (SEM) was used to determine the slag consumption as well as the Ca/Si ratio in calcium silicate hydrate gel (C-S-H) products. A tentative stoichiometric ratio of 2.6 mol of CH consumed per mole of slag reacted was determined using two methods. By combining consumption data determined separately for slag and CH a molar stoichiometry of 2.79 was found. Similarly, by directly determining the Ca/Si ratio in the C-S-H gel product, a range for the molar stoichiometry between 1.65 and 3.42 was found. Finally, a comparison of the stoichiometry of the slag/CH reaction was made with slag/portland cement hydration. The basic features of both appear similar. In the C-S-H gel around slag grains, a calcium-to-silica ratio of 1.3 to 1.4 was found for both slag/CH and slag/cement systems.     

高炉铝酸钙炉渣浸出过程动力学

研究了高炉铝酸钙炉渣的浸出动力学,考察了搅拌强度、浸出反应温度、浸出剂初始浓度及炉渣粒度对浸出速率的影响. 结果表明,浸出过程符合一级反应的收缩未反应核模型,宏观动力学方程为1+2(1-xB)-3(1-xB)2/3= 1.108exp(-1906/T)t,表观活化能为15.84 kJ/mol,过程速率为固膜内扩散速率控制. 通过实验数据验证,表明所得模型能较好地描述炉渣的浸出过程.     

氢氧化钙对硫铝酸盐水泥-粉煤灰复合胶凝材料的水化影响

通过凝结时间、抗压强度和电阻率等分析手段,研究了Ca(OH)2对硫铝酸盐水泥-粉煤灰复合胶凝材料水化过程的影响.结果表明,掺入Ca(OH)2明显缩短了硫铝酸盐水泥-粉煤灰复合胶凝材料的凝结时间;当Ca(OH)2掺量为0.5%时,初凝时间最短,1 d、28 d强度均明显提高;当Ca(OH)2的掺量为2%时,28 d强度相比空白样提高了61.9%;掺入Ca(OH)2后,硫铝酸盐水泥-粉煤灰复合胶凝材料的1 d电阻率减小,随着Ca(OH)2掺量增大,电阻率逐渐减小,电阻率变化率极大值提前,说明Ca(OH)2加快了该复合胶凝材料的早期水化进程.XRD分析表明,掺入Ca(OH)2后,水化1 d时钙矾石的生成量增多,消耗无水硫铝酸钙的量增多;水化28 d时钙矾石的生成量相对变化较小,但强度明显增大,粉煤灰对硫铝酸盐水泥强度的贡献较为明显.     

氢氧化钙羰基化合成甲酸钙工艺研究

对氢氧化钙羰基化合成甲酸钙的工艺进行了初步研究,考察了温度、一氧化碳分压、不同添加剂和搅拌速率对反应速率的影响,实验结果表明,反应速率随着反应温度、一氧化碳分压、氢氧根浓度和搅拌速率的提高而提高,随着甲酸钙浓度的提高而降低,而甲酸钠和氮气的添加对反应速率几乎没有影响.     

水泥–矿渣复合胶凝材料中矿渣的水化特性

通过对不同矿渣掺量时水泥–矿渣复合胶凝材料中矿渣的反应程度、硬化浆体中Ca（OH）2含量以及水化硅酸钙（C–S–H）凝胶的Ca/Si比（Ca和Si的摩尔比）的测定,研究复合胶凝材料体系中矿渣的水化特性。结果表明：在水泥–矿渣复合胶凝材料中,矿渣掺量越大,矿渣反应程度越低,但矿渣掺量≤70%时,对矿渣的反应程度影响不大。高温养护可提高早期矿渣的反应程度,但阻碍其后期的进一步水化。矿渣早期水化生成外部水化产物时消耗一定的Ca（OH）2,使硬化浆体中Ca（OH）2含量降低,矿渣水化吸收Ca（OH）2中的Ca2＋,使生成的C–S–H凝胶的Ca/Si比降低较少;在水化后期,矿渣生成内部水化产物不再消耗较多的Ca（OH）2,使C–S–H凝胶的Ca/Si比降低相对较多,硬化浆体中Ca（OH）2含量有增加的趋势,保证硬化浆体的长期稳定性。     

氢氧化钙精制的新技术

本实验以草酸铵为主要原料对工业消石灰进行精制。同时测试了草酸铵用量对氢氧化钙的有效钙含量和产率的影响,测试了在不同pH条件下对氢氧化钙的有效钙含量和产率的影响,测试了不同加热温度对草酸钙分解温度的影响。结果表明,3％草酸铵溶液用量为436mL,pH范围为3．5～4．4,加热温度为1000℃时,氢氧化钙的有效钙含量和产率最高。     

A Trend to the Production of Calcium Hydroxide and Precipitated Calcium Carbonate with Defined Properties

In this paper, production of precipitated calcium carbonate (PCC) with required particle size and morphological structure, along with its dependence on technological parameters and the properties of Ca(OH)₂, is discussed. The effect of the reaction environment on the kinetics of CaO hydration and the formation of crystals in water suspension was established. A remarkable difference in the system's restoration ability after stirring was observed. The hydration process is initially controlled by a kinetic mechanism, followed by a diffusion‐controlled process. The dissolution speed of lime hydrated to suspension is eight times higher than that of lime hydrated to powder. Particles of hydrated lime appeared in various forms.     

Hydration Products and Reactivity of Blast-Furnace Slag Activated by Various Alkalis

Pastes of blast-furnace slag were cured for up to 90 d using sodium silicate (waterglass), NaOH, and three different mixtures of Na₂CO₃–Na₂SO₄–Ca(OH)₂ to activate reactions. The highest slag reactivity was observed for NaOH activation and the least for waterglass, although nonevaporable water indicated similar amounts of hydration products formed. The main hydration products found using X-ray diffractometry in all systems were calcium silicate hydrate (C-S-H) and a hydrotalcite-type phase. Microanalysis was performed on pastes activated using 50% Na₂CO₃·25% Na₂SO₄·25% Ca(OH)₂, NaOH, and waterglass; the chemical composition of the C-S-H in the waterglass case was different relative to the other two alkalis. For all alkaline agents used, the C-S-H seemed finely intermixed with a hydrotalcite-type phase of Mg/Al = 1.82, on average.     

Structure of Calcium Silicate Hydrates Formed in Alkaline-Activated Slag: Influence of the Type of Alkaline Activator

The influence of the alkaline activator (NaOH, waterglass, or Na₂CO₃) on the structure of the hydrated calcium silicate formed in alkali-activated slag (AAS) cement pastes has been investigated by FTIR, ²⁹Si and ²⁷Al magic-angle scattering nuclear magnetic resonance, and TEM/EDX techniques. In all cases, the main product formed after 7 d of activation, with activators giving an Na₂O concentration of 4%, is a semicrystalline calcium silicate hydrate with a dreierkette-type anion. In these structures, linear finite chains of silicate tetrahedra ( Q ² units) are linked to central Ca-O layers, and tetrahedral aluminum occupies bridging positions in the chains. The main chain length and the amount of aluminum incorporated in the tetrahedral chains depend on the activator used. The detection of Q ³ silicon entities in alkaline-activated slags is discussed in relation to the possible formation of cross-linked structures that may be responsible for increased flexural and compressive strengths in AAS mortars.     

氢氧化镁粉体的干燥动力学研究

采用以六水氯化镁为原料,氢氧化钠和氨水为混合沉淀剂的直接沉淀法,制备得到平均粒径约为2μm的氢氧化镁粉体。通过不同干燥介质温度和不同湿物料层厚度的干燥动力学实验,获得氢氧化镁粉体的干燥曲线和干燥速率曲线。采用Weibull函数模型,对实验数据进行拟合分析,得到氢氧化镁粉体的干燥动力学参数和干燥动力学方程,探讨干燥动力学参数的影响因素。研究结果表明,可以用Weibull函数模型来描述氢氧化镁粉体的干燥过程,尺度参数与干燥介质温度及物料层厚度有关,随着干燥介质温度的提高,或物料层厚度的降低,干燥速率增大,尺度参数减小,但形状参数变化不大。     

钙镁摩尔比对氢氧化钙碳化性能的影响

为提高矿物周碳效率,采用固体法碳化,在CO2质量分数为99.9％、压力为0.3 MPa、液固比为0.10、碳化时间为2.0h条件下,探讨了不同Ca与Mg摩尔比(Mr)对氢氧化钙和氢氧化镁混合物碳化质量增加率的影响.结果表明:当Mr为5时,碳化质量增加率达到最大值23.75％;加入氢氧化镁,可使碳化产物结构疏松、细化氢氧化钙的碳化产物,碳化程度提高;同条件下,氢氧化镁碳化程度远低于氢氧化钙的.     

X-ray Diffraction Investigations of Microstructure of Calcium Hydroxide Crystallites in the Interfacial Transition Zone of Concrete

This work presents theoretical and experimental X-ray diffractometry investigations of the morphology and deformation state of calcium hydroxide (Ca(OH)₂, CH) crystallites in the interfacial transition zone of concrete. Based on the developed theoretical approach, the distributions of CH crystallites and their coherent domains over strains and sizes are reconstructed. The average amounts of planar defects, cracks, and possible stacking faults within a CH crystallite are estimated. A comparative analysis is conducted for the morphology of CH texture depending on the type of aggregate particles (granite and smoky quartz) used.     

麦秸秆的氢氧化钙预处理及酶解试验研究

采用氢氧化钙对麦秸秆进行预处理,以酶解还原糖得率为目的,分别优化预处理及酶解条件。结果表明,氢氧化钙预处理麦秸秆的最佳条件是:Ca(OH)2添加量为0.06g/g(对秸秆),固液比为1:10,在120℃下反应时间为2h;最佳酶解条件是:温度50℃,pH4.8,纤维素酶17FPU/g(对秸秆),木聚糖酶160IU/g,在添加0.15g/g(对秸秆)Tween80条件下,酶解液中还原糖质量浓度为62.32g/L,酶解还原糖得率达85.23%。     

氢氧化镁纳米棒的热分析干燥动力学研究

在不同干燥介质温度（333～513K）和不同物料床层厚度（0．5～7mm）的恒定干燥条件下,得到氢氧化镁纳米棒的干燥曲线和干燥速率曲线。采用热分析动力学技术对干燥动力学实验数据进行处理后,得到氢氧化镁纳米棒的干燥微分机理函数为f（1-MR）=2MR（-MR）^1/2,干燥积分机理函数为g（1-Mg）=（-lnMR）^1/2,干燥方程为Mn=exp[-（kt）^2],干燥速率方程为-dMR/dt=2kMR（-lnMR）^1/2,干燥速率常数为k=Aexp[-Ea／RT]=Aexp[-Ev（1＋CLL）／RT];指前因子A=10．741min^-1,界面蒸发活化能Ev=10．671kJ/mol,经验常数CL=100．000m^-1。     

Formation Kinetics of Calcium Aluminates

The kinetics of formation of calcium aluminates was studied by firing the reaction mixes in the temperature range 12000° to 1460°C for reaction times from 15 to 360 min. Phases formed were determined by taking X-ray diffractograms of the samples. It was observed that all stable calcium aluminates were formed and that monocalcium aluminate (CA) grew with calcium dialuminate (CA₂) in a 1:2 reaction mix of CaO and Al₂O₃. CA reacted further with Al₂O₃ to form CA₂. The formation of CA₂ obeyed the rate law equation 1 - (1 - x )^1/3= Kt / r ². The activation energy for the system (140 kJ·mol⁻¹ (33.4 kcal · mol⁻¹)) was determined by the Arrhenius equation.     

钢渣粉对硫铝酸盐水泥水化过程的影响及热力学模拟

通过测试水泥浆体的凝结时间、抗压强度、电阻率,同时结合水化产物分析及热力学模拟,研究了不同掺量钢渣粉对硫铝酸盐水泥水化行为的影响规律。结果表明,随着钢渣粉质量掺量的增大,初凝时间呈先延长后缩短的趋势,且在掺量为20%时达到最大值。在28 d龄期内,掺入钢渣粉的水泥硬化浆体抗压强度均小于未掺入钢渣粉的硬化浆体,但在龄期达到60 d和90 d时,掺入40%钢渣粉试样的抗压强度均大于未掺入钢渣粉的试样。钢渣粉与硫铝酸盐水泥复合浆体的电阻率在水化初始阶段随着钢渣粉掺量的增大而增大,在水化后期(约3 h后)则随钢渣粉掺量的增大而减小。在1 d龄期内,钢渣粉掺量为40%的试样中的钢渣粉发生了水化反应,使得水泥浆体在减速期的水化速率最大。由热力学模拟结果可知：在钢渣粉掺量为40%的试样中,C₂S在10 h后开始进行水化反应,C₂ASH₈则在168 h后开始生成;当钢渣掺量大于15%时,随着钢渣粉掺量的增大,钙矾石和铝胶的生成量逐渐减少,C₂ASH₈的生成量逐渐增多。     

PE／铝酸酯偶联改性Ca（OH）2体系流变行为研究

从流变学角度出发，用动态流变行为和瞬态流变行为分析铝酸酯偶联改性的聚乙烯／氢氧化钙（PE／Ca（OH）2）体系，结果表明：以铝酸酯作为偶联剂，对Ca（OH）2具有一定的偶联改性作用，可以削弱PE复合材料中无机粒子团聚，Ca（OH）2在PE中的填充量30％是最适宜的。     

Kinetics of Tricalcium Aluminate and Tetracalcium Aluminoferrite Hydration in the Presence of Calcium Sulfate

Hydration reactions of C₃A and C₄AF with calcium sulfate hemihydrate and gypsum were investigated and the kinetics of the reactions compared. The rates of C₃A and C₄AF hydration, as determined by heat evolution, vary depending on whether the sulfate-containing reactant is gypsum or calcium sulfate hemihydrate. The following sequence of reactions involving C₄AF occurs when hemihydrate is the reactant: gypsum formation during the first hour, ettringite formation between 20 and 36 hours, and the conversion of ettringite to monosulfate over a period of about 12 hours. Monosulfate formation initiates prior to the complete consumption of gypsum. The onset of this conversion occurs at a shorter hydration time when hemihydrate is a reactant and the total amount of heat evolved is lower. The hydration reactions in saturated calcium hydroxide solution occur more slowly than those in water. Based on heat liberation, C₄AF reacts at a much higher rate than C₃A. Ettringite formation occurs during the first 8 to 9 days of C₃A hydration. Once the gypsum is consumed, ettringite converts to monosulfate during two additional days. Compared to gypsum, hemihydrate decreases the rates of hydration of both C₃A and C₄AF. The effects on the hydration characteristics of C₄AF are significant. The hydration of C₃A with gypsum in water, in saturated Ca(OH)₂ solution, and in 0.3 M NaOH solution were compared. Heat evolution is the lowest for hydration in 0.3 M NaOH. The onset of monosulfate formation occurs prior to the complete reaction between gypsum and C₃A in the NaOH solution.     

Characterization by Multinuclear High-Resolution NMR of Hydration Products in Activated Blast-Furnace Slag Pastes

The effect of activators on the hydration of granulated blast-furnace slag (gbfs) was studied through compressive strength measurements, ²⁹Si, ²⁷Al, and ²³Na high-resolution nuclear magnetic resonance, and X-ray diffraction. Four different activations containing sodium hydroxide, sodium silicate, and/or calcium hydroxide (CH) were considered, at fixed amounts of alkali: 5% Na₂O, 5% Na₂O-2.5% CH, 5% Na₂O-7.5% SiO₂, and 5% Na₂O-2.5% CH-7.5% SiO₂. Silicate-activated gbfs cements have greater compressive strength than Portland cements over the whole period of study (1 yr). Also, silicate-free activated gbfs cements have poorer mechanical strength than silicate-activated cements. In fact, substantial structural differences were observed between hydration products in both kinds of activations. In silicate-activated pastes there exists an intimate mixture of C-S-H layers and AFm-like arrangements containing Al in octahedral sites bonded to the silicate layers, originated either from phase intergrowths or from a high density of Ca-Al incorporation in the interlayer spaces of C-S-H. In pastes obtained from silicate-free activation of gbfs there is a better chemical and structural definition among C-S-H and calcium aluminate hydrate domains (AFm and hydrogarnet).