Effect of the type of superplasticizer on the properties of cementitious systems incorporating slag

Superplasticizers have become an integral ingredient in the formulation of concretes. After 40?years, their use and dosage remain uncertain due to variations in their compositions and those of cement. In addition, the substitution of cement by supplementary cementitious materials having different chemical compositions exacerbates the problem without counting the multiplicity of superplasticizers to choose from. The present work consists of a study of the rheological and mechanical properties of cementitious systems containing slag and various types of superplasticizers. The tests were carried out on pastes, mortars and concretes incorporating slag in partial cement replacement and four superplasticizers types, polynaphthalene sulphonate (PNS) and three polycarboxylates (PC). The results of this study demonstrate that the viscosity and the yield stress increase with the rate of incorporation of the slag. The air increases with the polycarboxylates but this effect is less perceptible in the presence of the slag. Polycarboxylates improve workability more than PNS. The use of polycarboxylates reduces the viscosity and the yield stress. The compressive strength of concretes containing slag is low at early age but high at long run. They exhibit good resistances to scaling. The permeability to chloride ions is considerably reduced in the presence of the slag independently of the type of superplasticizer, suggesting good durability of these concretes in potentially aggressive external environments.     

CO2辅助挤压对马铃薯渣可溶性膳食纤维的影响

以马铃薯渣为原料,研究CO2辅助挤压各工艺条件对马铃薯渣可溶性膳食纤维的影响。结合马铃薯渣颜色、持水力、持油力和膨胀力的变化,得出CO2辅助挤压最佳工艺参数为:CO2发生剂柠檬酸与碳酸氢钠添加质量比为1∶1、添加量30%(质量分数)、挤压温度185℃、物料含水量25%(质量分数)、螺杆转速170 r/min。在此工艺条件下,挤压所得马铃薯渣可溶性膳食纤维含量较高,色泽较好,水合特性得到较好地保持,可为马铃薯渣膳食纤维的改性提供参考。     

Influence of size-classified and slightly soluble mineral additives on hydration of tricalcium silicate

Early-age hydration of cement is enhanced by slightly soluble mineral additives (ie, fillers, such as quartz and limestone). However, few studies have attempted to systematically compare the effects of different fillers on cementitious hydration rates, and none have quantified such effects using fillers with comparable, size-classified particle size distributions (PSDs). This study examines the influence of size-classified fillers [ie, limestone (CaCO₃), quartz (SiO₂), corundum (Al₂O₃), and rutile (TiO₂)] on early-age hydration kinetics of tricalcium silicate (C₃S) using a combination of experimental methods, while also employing a modified phase boundary and nucleation and growth model. In prior studies, wherein fillers with broad PSDs were used, it has been reported that between quartz and limestone, the latter is a superior filler due to its ability to partake in anion-exchange reactions with C-S-H. Contrary to prior investigations, this study shows that when size-classified and area matched fillers are used—which, essentially, eliminate degrees of freedom associated with surface area and agglomeration of filler particulates—the filler effect of quartz is broadly similar to that of limestone as well as rutile. Results also show that unlike quartz, limestone, and rutile—which enhance C₃S hydration kinetics—corundum suppresses hydration of C₃S during the first several hours after mixing. Such deceleration in C₃S hydration kinetics is attributed to the adsorption of aluminate anions—released from corundum's dissolution—onto anhydrous particulates’ surfaces, which impedes both the dissolution of C₃S and heterogeneous nucleation of C-S-H.     

Preparation of CaO granules using the granulation method

ABSTRACT

Improving the hydration resistance of CaO particle in manufacturing and application of free CaO-containing materials has practical significance. In this study, CaO granules was made from Ca(OH)₂ particles, which were fabricated by the granulation method. The results showed that the hydration resistance of the CaO granules which was prepared under 1700?r?min^?1 was the best, the CaO granules was sintered well in calcination process, the shell of CaO granules was relatively dense, which improves the hydration resistance of CaO granules, and the rate of hydration weight increment was 0.58% after placed in the air for 20 days under a temperature of 10–14°C and a relative humidity of 57–81%.     

Thermodynamic parameters of amitriptyline hydrochloride–additives at cloud point: effects of the ethanol–water mixed media

Abstract

Addition of organic solvents is known to change the properties of amphiphiles through modification of bulk phase. Amitriptyline hydrochloride (AMT) is a tricyclic amphiphilic drug which is usually used as an antidepressant. In drug delivery, the cloud point (CP) of the drug is an important parameter. This article discusses the effects of ethanol–water (EtOH–WR) compositions on the energetic parameters, such as changes in Gibbs energy of clouding (Δ_sG⁰), enthalpy of clouding (Δ_sH⁰), and entropy of clouding (TΔ_sS⁰) of AMT-additive systems. Monovalent alkali halide salts, cationic conventional surfactants, and gemini surfactants were used as additives in the EtOH–WR mixed media whose compositions were varied between 0 and 15% (w/w). The Δ_sG⁰ values are positive for all the additives and the values decrease with the rise in mole fractions of the additives. The Δ_sH⁰ and TΔ_sS⁰ were noted to be positive except for KF in 15% EtOH–WR mixed media.     

大体积超高性能混凝土温控措施及施工监测

针对襄阳庞公大桥索塔钢混结合段大体积超高性能混凝土（UHPC）的性能要求，采用低水化热低收缩UHPC开展了室内绝热温升试验和大体积模型试验，研究了低水化热低收缩UHPC的水化放热规律。施工过程中采用加碎冰降温和覆盖保温泡沫板的措施，明显降低了UHPC拌和物的入模温度和结构内外温差，大大降低了大体积UHPC的开裂风险，拆模后外观良好无任何裂纹。     

Improvement in hydration resistance of CaO granules by addition of Zr(OH)4 and Al(OH)3

Improving the hydration resistance of CaO aggregates is the key to successful application of lime-based refractories in metallurgical industry. Additive Zr(OH)₄ and Al(OH)₃ were introduced in the preparation of CaO granules using granulation equipment and calcination method in this study. The results showed that the hydration resistance of CaO granules was improved significantly, especially for granules with 0.6 wt.% Zr(OH)₄ and 0.9 wt.% Al(OH)₃, respectively. The shell of CaO granules was relatively dense after calcination and the volume of open pores of CaO granules decreased from 3.56 × 10⁻² to 1.80 × 10⁻² cm³/g when additive was introduced. Zr(OH)₄ and Al(OH)₃ have the opposite effect on the closed porosity of CaO granules, the closed porosity of CaO granules was decreased with Zr(OH)₄ addition, but increased with Al(OH)₃ addition.     

马来酸三乙醇胺酯对水泥水化的影响

为克服三乙醇胺早强剂对水泥抗折强度和后期强度的影响,合成了马来酸三乙醇胺酯,并通过背散射电子成像(BSE)和BET分析,研究了马来酸三乙醇胺酯对水泥水化程度、C-S-H含量和水泥水化28 d分形维数的影响。结果表明:马来酸三乙醇胺酯可促进水泥水化尤其是水泥中硅酸盐相的水化;复掺马来酸三乙醇胺酯和聚羧酸减水剂,可显著提高水泥水化产物中C-S-H的含量;三乙醇胺降低了水泥石28 d的分形维数,马来酸三乙醇胺酯单掺及与聚羧酸减水剂复掺则使水泥石28 d的分形维数提高。由此可见,马来酸三乙醇胺酯作为增强型水泥早强剂具有广阔的应用前景。