国内外速凝剂添加装置简介

在喷射砼施工中,为获得较高的早期强度,在增加喷层厚度时,一般都在砼中加入一定量的速凝剂。目前国内大多用人工添加,这不仅增加了劳动强度,危害工人的健康,而且掺量也不易均匀,增大了砼强度的离散性。对此,不得不靠提高砼的标号来增加喷层强度,造成一定很费。国外对此很重视,研制并应用了各种各样的添加装置。近年来,国内也有两种速凝剂添加装置通过部级鉴定。现将国内外几种添加装置简介如下。 1.滚筒式添加装置 图1是瑞士阿利瓦公司研制的速凝剂添加装置。     

喷射混凝土用无碱液体速凝剂的制备及其 机理研究

采用常温滴加工艺,以纳米活性氧化铝和改性醇胺为主要原料制备了一种喷射混凝土用无碱液体速凝剂(AFL).通过贯入阻力研究了速凝剂应用于混凝土,其中早期硬化强度的发展对喷射混凝土回弹量的影响,并通过XRD和SEM微观特征研究,分析了不同类型速凝剂的作用机理.结果表明,无碱液体速凝剂AFL掺量为6％时,初终凝时间满足GB/T 35159—2017《喷射混凝土用速凝剂》检测要求,1 d抗压强度21.8 MPa,28 d抗压强度比111.8％,90 d抗压强度保留率110.4％,30 min内混凝土硬化强度高,应用于喷射混凝土中,隧道拱顶和侧墙的回弹率分别为13.4％ 和6.4％.     

对JC477《喷射混凝土用速凝剂》标准的几点看法

0前言JC477（喷射混凝土用速凝剂）标准（以下简称JC477标准）于1995年实施。本文根据多年来对速凝剂产品检验分析经验，对该标准中部分内容提出一些看法。11d抗压强度指标表1是JC477标准中掺速凝剂喷射混凝土的指标。通过对本地区A、B两家厂产品的检验和分析，我们认为表1中id抗压强度指标不能全面反应现场施工中掺加速凝剂对喷射混凝土id抗压强度增长情况的影响。为能准确客观地反应喷射混凝土用速凝剂产品质量特性，特别是能直观反应产品实际施工中的使用情况，我们认为在Jt477标准中应增加id抗压强度比。2对基准水泥的要成JCh77标…     

SL型液体低碱混凝土速凝剂的研究

本文介绍了一种低碱液体混凝土速凝剂，可用于喷射混凝土的湿喷工艺施工。作者对速凝剂的促凝效果、掺速凝剂的水泥浆体的强度发展以及该速凝剂对不同水泥的适应性进行了研究，并研究了温度变化对该速凝剂的促凝效果的影响。     

速凝剂掺量对水泥混凝土强度的影响初探

在隧道施工或者应急救险施工中中,速凝剂是不可或缺的材料,速凝剂能使混凝土快速的凝固,达到施工效果,但是速凝剂掺量的大小对混凝土强度的影响是巨大的,本文通过不同速凝剂掺量对水泥胶砂强度的影响来间接推定对混凝土强度的影响。     

“水泥-速凝剂-水”系统的水化反应特征及凝结硬化机理研究现状

速凝剂是喷射混凝土不可缺少的化学外加剂,但目前对速凝剂速凝及硬化作用机理方面的认识存在分歧和争议.本文从“水泥-速凝剂-水”系统的角度出发,综述分析了不同类型的速凝剂对“水泥-速凝剂-水”系统水化反应特征的影响和其快速凝结硬化的机理.明确了水化产物中的水化硫铝酸盐在充水孔隙中的快速形成是实现速凝的主要原因.高硫型水化硫铝酸钙(AFt)向低硫型水化硫铝酸钙(AFm)的晶型转化导致硬化浆体孔隙率增加,并延缓硅酸盐矿物的水化,是铝酸盐类速凝剂引起喷射混凝土后期强度降低的原因.水泥的化学组成对“水泥-速凝剂-水”系统的水化进程和凝结硬化具有重要的影响.喷射工艺的高剪切作用会加速AFm形成,抑制硅酸盐矿物的水化,对掺加碱性速凝剂的喷射混凝土强度发展有不利影响.     

掺矿渣水泥混凝土路用性能研究

为提高水泥路面强度和耐久性以适应西部地区的恶劣天气，进行了在普通水泥砼中掺入矿渣掺和料的砼性能试验．检测了掺矿渣水泥砼的路用性能，并阐述了其机理。试验数据和机理分析证明，掺入矿渣可以提高水泥砼的力学性能和耐久性能．砼的微观界面结构也得到了改善。矿渣水泥砼的各项路用性能随矿渣掺量的变化不同，当矿渣掺量为30％时。砼的力学性能和耐磨性能均高于其他掺量的砼。     

新拌湿喷混凝土内聚力测试与影响因素分析

新拌湿喷混凝土内聚力是决定湿喷混凝土一次喷射厚度的关键因素.设计直剪试验,采用正交试验方法分析了新拌湿喷混凝土内聚力影响因素,结果表明:新拌混凝土内聚力与流动性线性负相关性显著;影响新拌湿喷混凝土内聚力的因素排序为砂率＞速凝剂掺量＞粉煤灰掺量＞水胶比.砂率由50％增大到70％时,新拌混凝土内聚力逐渐降低;水灰比从0.4增大至0.5时,新拌混凝土内聚力先增大、后减小;粉煤灰掺量不超过20％时,可提高新拌混凝土内聚力;新拌混凝土内聚力随速凝剂掺量增大,超过最佳掺量后新拌混凝土内聚力增值微小.     

新型喷射混凝土速凝剂的研究进展

主要概述了喷射混凝土速凝剂的发展现状和典型的作用机理,同时,介绍了低减和无碱速凝剂、液体速凝剂、有机高分子复合速凝剂和矿物基速凝剂等新型喷射混凝土速凝剂的化学组成、性能特点和研究进展,并对新型喷射混凝土速凝剂的研究和发展趋势进行了展望.     

铁路隧道聚丙烯纤维喷射混凝土力学与耐久性能研究

聚丙烯纤维喷射混凝土在铁路隧道中得到了广泛的使用。因此,制备了聚丙烯纤维体积掺量分别为0、0.05%、0.10%、0.15%、0.20%和0.25%的喷射混凝土;开展了不同聚丙烯纤维体积掺量和养护龄期的混凝土抗压强度、抗折强度和抗拉强度测试,不同聚丙烯纤维体积掺量的抗渗性能测试,以及不同聚丙烯体积掺量和冻融循环次数的抗冻性能测试;分析了聚丙烯纤维掺量对喷射混凝土力学与耐久性能的影响规律。研究结果表明：聚丙烯纤维的加入能够提高铁路隧道喷射混凝土的拉压比,提高其抗裂以及抗震能力,聚丙烯纤维体积掺量为0.10%～0.20%时,铁路隧道喷射混凝土的抗压和抗折性能最佳;聚丙烯纤维体积掺量由0增加至0.10%时,铁路隧道喷射混凝土的渗水高度减小幅度最大,抗渗性价比最高;铁路隧道喷射混凝土抗冻性能最佳的聚丙烯纤维体积掺量为0.15%。     

闪蒸气相色谱-质谱联用法鉴定硫化胶中的常用促进剂种类

采用闪蒸气相色谱-质谱联用法鉴定硫化胶中常用的促进剂种类。结果表明:当特征反应产物仅有苯并噻唑基团时,促进剂为MBT或MBTS;当特征反应产物除苯并噻唑外,还有叔丁胺、环己胺或二环己胺基团时,可分别判定为促进剂TBBS,CBS,DCBS或其与促进剂MBT/MBTS共存。本方法采用裂解器直接进行硫化胶样品闪蒸,分析效率高,结果准确可靠。     

Effects of setting regulators on the efficiency of an inorganic acid based alkali-free accelerator reacting with a Portland cement

Today, in the field of underground constructions, alkali-free accelerators are commonly employed, during tunnel excavation, to allow flash concrete setting. In this way, the cementitious sprayed material can firmly bond to the tunnel walls, controlling the convergence (the tendency of the section to squeeze). Their efficiency may be related to many parameters like: cement type, setting regulator, concrete composition, working temperature. Nevertheless, the influence of such factors on the accelerator performance has not been clarified yet. The accelerator efficacy is evaluated by real spraying test in job site or, when only laboratory equipment are available, by measuring the final setting times of cement systems admixed with the accelerator. Several alkali-free flash setting admixtures are available on the market. They can be divided into two main categories both containing aluminium sulphate complexes stabilized either by inorganic acids or by organic acids. In this paper, the influence of different setting regulators on the performances of an inorganic acid based alkali-free accelerator was analysed. Portland cement samples were obtained by mixing clinker with gypsum, α-hemihydrate, β-hemihydrate or anhydrite. The setting regulator instantaneous dissolution rates were evaluated through conductivity measurements. The setting time of cement pastes with and without the accelerator was measured. It was found that the shorter the final setting time (therefore the more efficient is the accelerator) the lower the setting regulator instantaneous dissolution rate. In order to understand this phenomenon, a comparison was performed between accelerated cement paste samples containing the setting regulator with the highest (β-hemihydrate) and the lowest instantaneous dissolution rate (anhydrite). The analytical work included morphological (Environmental Scanning Electron Microscopy-Field Emission Gun — ESEM-FEG), crystal-chemical (X-Ray Powder Diffraction — XRD), physical-chemical (hydration temperature profile) and chemical (Induced Coupled Plasma-Atomic Emission Spectroscopy — ICP/AES) evaluations. The results revealed significant morphological differences among the investigated samples.     

A case history: Effect of moisture on the setting behaviour of a Portland cement reacting with an alkali-free accelerator

Flash setting accelerators are a class of admixtures commonly used for sprayed concrete during tunnel excavation. They allow an immediate set of concrete which can bind to the substrate without dangerous collapses. Such a coating layer prevents the section convergence that is its tendency to squeeze. The early strength development (till 1 h) of the sprayed concrete can be connected to the final set time of cement pastes admixed with the accelerator. The lower is the final set time, the higher should be the early strength. Two main methods are used to project concrete: wet and dry. Today, for safety reasons and to obtain more homogeneous concrete layers, the wet method is becoming more diffused. This technique requires the use of liquid flash setting accelerators which are pumped to a nozzle and immediately projected onto the rock wall. In the European market, two kinds of setting accelerators are mainly available: alkali-rich and alkali-free. Recently, for several reasons, the demand of alkali-free accelerators is growing very rapidly. They are water solutions of aluminium sulphate with a total alkali metal content (expressed as equivalent of Na₂O) lower than 1%. In order to develop new and more performing accelerators, several studies are in progress to elucidate their action mechanism and the factors affecting the setting of accelerated concretes.During an experimental study on the setting behaviour of several cement pastes reacting with an alkali-free accelerator, we found a cement showing, as time proceeded, a persistent setting time reduction. We discovered that the effect was connected to the cement exposure to the moisture. A mineralogical investigation performed on this particular cement revealed the presence of hemihydrate as setting regulator. In order to study the interaction between the alkali-free accelerator and this moist aged cement, some morphological (ESEM-FEG), crystal-chemical (XRD), physical-chemical (hydration temperature profile) and chemical (ICP) analyses on cement paste samples were carried out.This study showed a significant setting time reduction of cement paste samples admixed with an alkali-free accelerator when they are composed of a Portland cement containing β-hemihydrate that was previously exposed to moisture. Such an effect seems to be related to the reduction of the β-hemihydrate dissolution rate.     

绿色环保橡胶硫化配方研究

针对硫磺、促进剂M(2-巯基苯并噻唑)在橡胶制品加工中对环境的污染和对工人健康的危害，研究了硫磺、硫化剂DCP(过氧化二异丙苯)、硫化促进刑M、促进剂CZ(N-环己基-2-苯并噻唑次磺酰胺)在橡胶制品加工中的应用，从环保的角度进行了新的配方设计，并进行了性能测试。结果表明：同等务件下，生产相同的产品胶板，使用硫化剂DCP及促进剂CZ的制品综合性能要优于使用硫磺和促进刑M的制品，且有利于环保。     

基于变换变量的反应闪蒸过程计算

采用变换变量,浆发生多反应并伴有惰性组分的反应闪蒸过程模型变换为普通的非反应闪蒸模型。新模型避免了反应量的计算,将反应与相平衡结合计算的通用性好。用Ｎｅｗｔｏｎ－Ｒａｐｈｓｏｎ法模拟计算了甲醛－水溶液反应闪蒸及对二甲苯和邻二甲苯反应闪蒸分离过程。     

New Capabilities of Proton Radiography for Recording Fast Gas-Dynamic Processes

For about 15 years, studies of fast gas-dynamic processes have been conducted at the Logunov Institute of Experimental Physics (VNIIEF) of the Russian Federal Nuclear Center using the proton radiography system developed jointly with the Logunov Institute of High Energy Physics on the basis of a U-70 accelerator. The main advantages of flash proton radiography over widely used flash x-ray radiography are high spatial resolution, multiframe mode, transmission capability, dynamic range of recording, etc. In recent years, effort has continued to extend the capabilities of the proton radiography system by increasing the total time and recording field and supplementing it with additional diagnostic techniques and new explosion-proof chambers. This paper presents the results of studies that illustrate these capabilities.     

纯水静态闪蒸中液膜高度演变的实验研究

设计搭建了静态闪蒸实验台，利用高速摄影对不同过热度、节流孔板直径和闪蒸速率下纯水静态闪蒸过程中液膜高度的演变规律进行了实验研究。实验中过热度为7.0~32.5 K，节流孔板直径为5、10、20 mm，闪蒸速率为0.004~0.073 s^-1。通过液膜膨胀率来衡量和比较液膜高度的变化，液膜膨胀率是指闪蒸过程中液膜实时液位与初始液位的比值。结果表明：最大膨胀率随过热度或节流孔板直径的增大而增大；节流孔板直径一定时，闪蒸速率可通过改变过热度来调节，此时最大膨胀率随闪蒸速率的增大而减小；当过热度一定时，闪蒸速率可通过改变节流孔板直径来调节，此时最大膨胀率随闪蒸速率的增大而增大。最后，根据实验结果拟合得到过热度、闪蒸速率与最大膨胀率的实验关联式，其计算值与实验值吻合良好。本文研究结果对工业闪蒸设备小型化、紧凑化和精细控制提供了重要的实验依据。     

硫化体系对NBR/PCMO共混物性能的影响

研究不同硫化体系对NBR／氯化聚醚(PCMO)共混物性能的影响。试验结果表明，低硫高促硫化体系共混物硫化胶的耐热空气老化性能较好，复合硫化体系共混物硫化胶的压缩永久变形性能最佳；过氧化物硫化体系中硫化剂DCP用量为3．5份，甲基丙烯酸锌[Zn(MMA)2]／DCP硫化体系中Zn(MMA)2用量为10份、硫化剂DCP用量为     

复合硫化体系对ACM/NBR共混胶性能的影响

分别采用TCY/硫黄、3#硫化剂/硫黄/促进剂、皂/硫黄/促进剂3种复合硫化体系硫化ACM/NBR共混胶。研究不同复合硫化体系、TCY用量和硫黄用量对ACM/NBR共混胶硫化特性、力学性能、耐热老化性能、耐油性能和压缩永久变形性能的影响,结果表明,TCY/硫黄复合硫化体系硫化的ACM/NBR共混胶的综合性能优于3#硫化剂/硫黄/促进剂和皂/硫黄/促进剂复合硫化体系,当TCY/硫黄的用量为1.5/0.3份时,ACM/NBR共混胶具有良好的综合物理机械性能。     

经济器在工业冷冻系统中的应用

介绍了带经济器的螺杆式制冷压缩机系统的工作原理以及干式、闪发式、满液式经济器的特点,并通过运行数据,分析了不同蒸发温度下经济器对机组性能的影响。