蛇纹石石棉超细分散基础研究(一)

用扫描电镜及透射电镜研究了不同分散剂、不同水固比和分散剂用量对石棉纤维的分散效果。通过搅拌、球磨、超声波分散流程,对蛇纹石石棉进行了超细分散。结果表明,阴离子表面活性剂快T(二辛基磺化琥珀酸钠)对石棉纤维有十分良好的分散效果。分散剂用量为 20 %左右的分散效果较好,而且搅拌和球磨时间越长效果越好。经过搅拌、球磨、超声波振荡分散和沉淀静止,可得到纤维直径40~300nm的超细纤维。     

掺镍纤维的水泥基复合材料导电性能研究

以镍纤维作为导电介质掺合到水泥砂浆中制成水泥基复合材料,研究了纤维长径比、砂浆搅拌工艺、外加分散剂种类及用量和纤维掺量等因素对水泥基复合材料导电性能的影响,采用四探针测试仪和扫描电镜表征了复合材料的电导率和纤维的分散状态。实验结果表明:采用干混搅拌工艺、镍纤维的长径比为750、甲基纤维素(MC)分散剂掺量为0.4%时,镍纤维在水泥基复合材料中的分散效果最佳;在此工艺条件下,当镍纤维掺量为5.0%时,水泥基复合材料电导率最大,达2.65×10-3 s/cm。     

PDC改性分散剂的应用

ＰＤＳ分散剂可以将矿物棉、硅铝棉等纤维进行松解并均匀有效地分散在制浆体系中。使石棉和快Ｔ的用量减少７０％，而生产出来的复合硅酸盐保温毡较泡沫石棉成本低，绝热效果好，耐高温。代替４０％的快Ｔ生产泡沫石棉，对提高质量，降低成本也取得很好的效果。本文介绍了ＰＤＳ分散剂的机理和在泡沫石棉、复合硅酸盐毡中的应用。     

青海大柴旦石棉成浆性试验研究

本文对青海大柴旦石棉原矿进行了物理化学性能检测,选用磺化琥珀酸双-2-乙基己酯钠盐（快T）、甲基纤维素等表面活化剂对石棉进行表面改性,研究了改性剂种类、添加量、水棉比、浸泡时间等对其成浆性能的影响。试验表明：当水棉比为10∶1、石棉纤维浸泡时间为8h、快T用量为10%时,石棉成浆的粘度值为300mPa.s,成浆性能较好。     

测定石棉纤维抗拉强度的几种方法

石棉纤维的抗拉强度是决定其工业价值的一项重要指标。现介绍几种测定石棉纤维抗拉强度的方法如下。(一)对于手选棉,一般是取一束未变形的针状石棉,用两手将其折成90°角,然后伸直,再曲折伸直,重复10次,如纤维束折断,即表示石棉的挠曲和抗拉强度较低,不能承受机械加工;如纤维完好无损,则表示石棉纤维比较柔和,适于梳纺。对于机选棉,可取少量纤维,两手持其两端反复拉     

高强度无石棉绝热材料

近来,海外研制成功一种高强度无石棉绝热材料。该绝热材料不仅强度高、韧性好,而且耐热,极易于切割加工,由于不含石棉,也属于一种环保型材料。过去,绝热材料多数是掺石棉纤维或纸浆纤维制成。但它们具有以下缺点:掺石棉纤维,制品切割时产生大量石棉粉尘,危害健康;掺纸浆纤维,其力学强度低,尺寸收缩大,韧性差,加热时易龟裂。该绝热材料是用芳香族聚醚酰胺单纤维取代石棉或纸浆纤维,与纤维状硅灰石、水泥胶结料和硅酸质粉末配料,加入到含纤维分散剂的水中,混合、脱水、加压、蒸压而成,其基体由硅酸钙水化物构成。试验表明,该绝热材料密度为1.3…     

提高成型压力 降低长纤维石棉用量

在轰轰烈烈的增产节约运动中,我厂职工在党委领导下大力开展以“短、省、代”为主要内容的节约长纤维石棉活动,大胆地提高了石棉水泥加压板生产对单位面积的压力。经过实践不但保证和提高了产品质量,而且大大地降低了长纤维石棉的用量。我厂过去石棉水泥加压板所用石棉纤维配合比是:长纤维石棉占60%中纤维石棉占20%短纤维石棉占20%工艺操作是:制板机毛毯上料层的厚度为0.25—     

分散剂对水镁石纤维分散性能的影响及机理分析

采用5种分散剂、3种分散工艺,分别在水和水泥孔隙溶液中研究不同分散剂和分散工艺对水镁石纤维分散性能的影响,通过扫描电镜、沉降实验、Zeta电位以及粒径测试对水镁石纤维的分散效果进行了表征,分析了不同分散剂对水镁石纤维分散作用的影响机理。结果表明,聚羧酸减水剂配合超声波分散工艺对水镁石纤维在水泥中的分散效果更为突出,其主要原因是聚羧酸减水剂吸附在纤维表面,通过双电层效应和侧链的空间位阻双重作用,促使水镁石纤维在水溶液(或水泥孔隙溶液)中充分分散。     

聚合物纤维增强水泥的强度性能

广泛应用石棉纤维作为石棉水泥制品的增强材料已有很久的历史。由于高品位长纤维石棉资源的耗尽和石棉纤维对人体健康带来的隐患,近年来,人们十分期望发展能代替石棉纤维的代用纤维,代用纤维显示出很好的发展前景,聚合物纤维也被考虑为这样的代用纤维。本研究的目的是弄清聚合物纤维增强水泥强度性能。本论文中,用硅灰和减水剂使聚合物纤维在水泥砂浆中均匀分散。用聚酰胺、聚丙烯腈和聚乙烯醇纤维制备聚合物纤维增强水泥,其水灰比为30％、硅灰比为40％、减水剂用量为水泥重量的4％、纤维的体积含量为0,2.5,和5.0％。用聚合物纤维增强水泥制作棱柱体试件的尺寸为40×40×160mm,试件首先在温度20℃、相对湿度80％的湿空气中养护一天,然后在60℃水中养护六天。养护后的试件进行抗弯强度试验,记录弯曲荷载—挠度曲线以计算弯曲韧性及等效弯曲强度。将经抗弯试验破坏后的部分试件进行抗压强度试验,从试验结果得到的结论概括如下: (1)除聚乙烯醇纤维增强水泥以外,聚合物纤维增强水泥的强度性能如抗弯和抗压强度、弯曲韧性和等效弯曲强度随纤维含量的增加有显著的改善; (2)聚乙烯醇纤维增强材料对聚合物纤维增强水泥的强度性能几乎没有什么影响; (3)除聚乙烯醇纤维外,聚酰胺和聚丙烯腈等聚合物纤维可用作石棉纤维的代用纤维。     

石棉粒

石棉粒是用石棉纤维和粘结材料制成的,用于热水瓶胆镀银玻璃夹层中作为保温、隔热材料。现将其生产工艺简要介绍于后。1.原料(1)石棉:我厂用西康五级棉,经锺式破碎机锺击两次,使石棉纤维充分松解,再筛分除去杂质(处理后砂石含量应不超过1.5%),长短纤维合理搭配后使用(4～6毫米中长纤维含量应控制在20%左右,过少会影响制品结构松散而不结实)。     

碳纳米管的分散性及其增强水泥材料力学性能

碳纳米管(MWCNT)在水性体系及水泥基体中的分散性直接影响MWCNT增强水泥基复合材料(MCNTRC)的宏观性能。本文以萘系磺酸盐甲醛缩合物(FDN)、甲基纤维素(MC)、十六烷基三甲基溴化铵(CTAB)三种表面活性剂(SAA)单独或复合作为MWCNT的水性分散剂,探讨MWCNT的分散效果;借助物理超声波分散和化学CTAB分散,混合浇筑法制备了六组不同掺量MWCNT的MCNTRC,之后对MCNTRC试件的抗折及抗压强度测试,断口SEM观察和能谱分析。结果表明:只有CTAB在w(CTAB):w(MWCNT)为1~3范围时对MWCNT分散效果最好;少量的MWCNT可较好地分散于水泥基体中,并发挥一定的桥联增韧作用,MCNTRC的抗折、抗压强度最高可分别提高17.0%、28.3%;相应SEM图也显示MWCNT在基体中分布均匀,两者结合界面良好。     

Evaluation of mechanical performance of cement matrix composites with dispersed phases used in substitution to asbestos

Technologies used nowadays require the manufacturing and development of materials with unique properties and performance that can only be achieved by composites, which combine different materials. Because of the chemical and morphological characteristics of asbestos fiber and its efficient anchoring effect, the cement-asbestos composite was widely used in the civil construction up to the 1960s, when handling of this fiber started to be considered hazardous to human health. Since then, researches have been developed in order to obtain alternative products to asbestos. In this work, cement matrices reinforced with different phases were investigated as replacements to asbestos. This investigation was based on the correlation between apparent porosity and four-point flexural resistance. Wollastonite, polypropylene, rice shell ash, and vermiculite were evaluated as substitutes to asbestos.     

Performance of fiber reinforced asphalt concrete under environmental temperature and water effects

This paper studies the reinforcing effects and mechanisms of fibers for asphalt concrete (AC) mixtures under the environment temperature and water effects. Four typical fiber types – polyester, polyacrylonitrile, lignin and asbestos – are studied. Laboratory tests were conduct on the fiber reinforced AC (FRAC) to measure its strength, strain and fatigue behavior. Results show that fibers have significantly improved AC’s rutting resistance, fatigue life, and toughness. The flexural strength and ultimate flexural strain, and the split indirect tensile strength (SITS) at low temperature have also improved. The polymer fibers (polyester and polyacrylonitrile) have improved rutting resistance, fatigue life, and SITS more significantly than lignin and asbestos fibers, which may be primarily due to their greater networking function; while lignin and asbestos fibers result in greater flexural strength and ultimate flexural strain, which may be primarily due to their greater asphalt stabilization effect. However, fiber’s effect under the water freezing–thaw effect does not seem promising, and the SITS of FRAC with lignin and asbestos fibers even reduces to some extent under this effect. It is also found that a fiber content of 0.35% by mass of mixture achieves the optimum performance outputs of rutting resistance and SITS for polyester fiber.     

无石棉维纶纤维水泥板的工艺原理与特性

研究用高模量维纶纤维与改性维纶纤维代替石棉制造无石棉纤维水泥板。这两种纤维的弹性模量虽显著低于石棉,但与水泥基体间有较好的界面粘结,故仍起增强作用。探讨了用抄取法制作无石棉维纶纤维水泥板的工艺原理,其中主要有维纶纤维的均匀分散、减少过滤过程中水泥粒子的流失、控制纤维水泥浆的过滤速率、调正抄取机的工艺参数、板坯的补充加压,采取合宜的蒸养制度等。所制成的维纶纤维水泥板具有以下主要特性:(I)横、纵向抗折强度与弹性模量低于石棉水泥板,但变形能力高于后者。(2)抗冲击强度高于石棉水泥板。(3)容重低于石棉水泥板。(4)与石棉水泥板一样,具有较好的不透水性、抗冻性、不燃性、耐热水性与机械加工性。     

Effects of oil dispersants and oil emulsions on marine animals

The toxicities to marine animals of nine oil dispersants, three oil emulsions with Corexit and of a dispersion of Oman crude oil, have been studied in continuous flow aquarium systems at 96-h exposures followed by a recovery period in clean sea-water. New types of dispersants were found to be less toxic than older types and oil emulsions more toxic than dispersants alone or crude oil alone. Fishes and bivalves were found most sensitive. Crustaceans were the most resistant to dispersants but very susceptible to oil emulsions. The tolerance of different species was found to be related to their mode of life, more active species being more susceptible. Delayed mortality of bivalves increased their susceptibility if the recovery period was included. Effects on locomotory behaviour of fishes and crustaceans, breathing rate of fish, valve-closure of bivalves and byssal thread formation of common mussels have been demonstrated for both dispersants and oil emulsions. The general sequence of such effects was: increased activity; successively impaired activity; immobilization; and death. Recovery is good for fish and crustaceans but poor for bivalves due to the delayed effects. Ecological consequences of dispersants and oil pollution in the marine environment are discussed.     

高温对C80HPC抗压强度及超声波速的影响

对C80HPC试件进行抗压强度试验与超声检测,分析聚丙烯纤维掺量对HPC高温前后混凝土爆裂现象、质量损失、抗压强度、声速变化的影响和不同超声测试距离对混凝土超声速率的影响。结果表明：掺加PP纤维可以明显抑制高温爆裂对C80HPC的影响;C80HPC试件的抗压强度随受火温度的升高而降低,当受火温度在200~300 ℃时,掺聚丙烯纤维的C80HPC试件抗压强度有所反弹;随着温度的升高,C80HPC试件超声声速下降,随着测距的增加,超声声速下降,下降幅度不大,可以通过超声声速探测混凝土内部损伤缺陷。建立了C80HPC抗压强度、受火温度和超声声速的关系。     

Asbestos-free technology with new high toughness polypropylene (PP) fibers in air-cured Hatschek process

After almost 70 years of experience in the fiber–cement production in Brazil, Saint-Gobain Brasilit started the non-asbestos production using polyvinyl alcohol (PVA) fiber technology in 2002.Due to PVA costs and availability problems, efforts were done to develop a local high toughness polypropylene (PP) fiber, with improved frictional interface and better dispersion and affinity to Portland Cement matrix.In the last 5 years, more than 1.6 million tons of asbestos-free corrugated and flat sheets have been produced and commercialized representing about 200 million square meters.This paper reviews the alternative fibers for replacing asbestos and the reinforcing model in cement based products. It also presents the Brasilit high toughness polypropylene fibers properties, its manufacturing process and its mechanical performance and improved impact resistance behavior comparing to fiber–cement products available in the Brazilian market.     

高压旋喷桩在托换中的工程实践

旋喷桩加固地基是地基处理的一种有效方法.总结了几个旋喷桩加固已有建筑地基的工程实例,认为在旋喷桩加固黄土地基中,只要把握好几个关键的技术环节,特别是回灌工作这一环节,就能获得较好的加固效果.     

无损检测技术在钢纤维混凝土工程中的应用

结合厦门至昆明国家重点公路干线的建设,通过对一批不同龄期的C40钢纤维混凝土试件进行超声波检测及抗压强度的试验研究,对试验结果进行回归分析,建立了不同龄期钢纤维混凝土超声波声速与抗压强度之间的关系曲线。结果表明:超声波检测方法用于钢纤维混凝土无损检测是可行和适用的。     

混杂树脂改性防水胶泥的试验研究

在试验基础上 ,研究了不同组分 (包括增塑剂、混杂树脂、石棉绒、滑石粉等 )对煤焦油沥青性能的影响 ,并利用了废旧塑料 ,通过大量试验确定了防水胶泥的最佳配方和生产工艺、产品性能优良 ,提高了防水材料的粘结性、耐温性、低温柔性、抗老化性和对基层变形的适应性