不同类型高效减水剂对混凝土性能的影响

对比研究了3类不同高效减水剂配制的混凝土力学性能、工作性能及抗裂性。结果表明,用聚羧酸系高效减水剂配制的混凝土具有坍落度损失小、抗裂性能较好及抗压强度高等优点。因此,在配制高性能混凝土时,首先宜选用聚羧酸系高效减水剂。     

聚羧酸混凝土高效减水剂的合成和研究现状

介绍了用于混凝土的聚羧酸高效减水剂(PC)合成研究现状。按照支链和主链的连接方式,聚羧酸高效减水剂可分为两类,第一类为甲基丙烯酸和甲氧基聚乙二醇甲基丙烯酸酯类共聚物,第二类为马来酸酐和烯丙醇聚乙二醇醚类共聚物。同时介绍了合成聚羧酸高效减水剂的主要组分大分子单体的制备方法,聚合方法和合成结构控制方法。综合国内外研究成果简要介绍了影响聚羧酸混凝土高效减水剂的分子结构和性能的关系,分散机理,测试和表征方法等。引用文献17篇。     

自燃煤矸石掺合料与高效减水剂相容性研究

自燃煤矸石易粉磨,比表面积较大、吸附水较多、表面能较高,若不与具有表面活性的高效减水剂复掺,很容易形成絮凝结构,降低水泥浆的流动性,不仅不能满足预拌混凝土的泵送要求,也影响硬化混凝土强度.本文首先采用胶砂对比试验,分别将不同粉磨时间的自燃煤矸石粉30％取代水泥,以自燃煤矸石-水泥胶砂强度较高者确定粉磨时间;在此基础上,选择自燃煤矸石粉掺量、减水剂品种和掺量为影响因素,通过正交试验研究自燃煤矸石粉与两类不同减水剂的相容性.结果表明,自燃煤矸石作混凝土掺合料经济粉磨时间为4～6 min,与两类减水剂相容性程度为:聚羧酸系＞奈系.自燃煤矸石粉无论与哪类减水剂双掺,建议自燃煤矸石粉掺量≤15％,而聚羧酸系减水剂掺量≤0.43％,奈系减水剂掺量≤0.8％.     

梳型聚羧酸高效减水剂的合成和应用性能述评

介绍了梳型聚羧酸高效减水剂合成研究及对水泥应用上的高分散性能。梳型聚羧酸高效减水剂分为甲基丙烯酸类共聚物和马来酸酐类共聚物,介绍了合成梳型聚羧酸高效减水剂的主要组分大分子单体的制备、聚合和合成结构的控制方法。综合国内外的研究成果简要介绍了聚羧酸混凝土高效减水剂分子结构和性能的关系、测试和表征方法、对水泥颗粒的分散机理等。     

萘系和聚羧酸高效减水剂与几种不同水泥品种间的相容性问题(长期结果)(英文)

研究了水泥与减水剂的相容性。采用萘系(naphthalene,NSF)和聚羧酸(polycarboxylate-based,PCE)系两类高效减水剂,5批次的6种广泛分布于意大利不同区域的水泥为原料。通过改变高效减水剂的掺入量使拌和后的砂浆和混凝土具有恒定的工作性;通过测定拌合后1h内的流动度保持度以表征每种减水剂的工作性经时损失。还测定了砂浆和混凝土1,7d和28d的抗压强度。结果表明:与萘系高效减水剂相比,聚羧酸高效减水剂的减水效果和流动度保持性较好;萘系高效减水剂的作用几乎与水泥的品种及批次无关。混凝土的流变性能和力学性能与其砂浆的测试结果一致。     

聚羧酸减水剂对混凝土成本控制的研究

本文以混凝土为研究对象,站在成本管控的角度,围绕通过利用高性能减水剂聚羧酸进行混凝土拌合实现成本节约展开研究。首先,对减水剂、聚羧酸减水剂等相关概念进行了简单地概述,并结合相关数据对聚羧酸减水剂的性能优势从多个方面进行了详细介绍;其次,在分析混凝土成本构成的基础上,结合聚羧酸减水剂高性能优势,就聚羧酸减水剂对混凝土成本控制的影响进行了详细介绍;最后,聚羧酸减水剂在混凝土中应用过程中应注意的几点关键性问题进行了强调。并将聚羧酸减水剂视作混凝土成本控制以及质量保障的关键所在。     

水泥与聚羧酸型混凝土减水剂适应性实验研究

针对聚羧酸型混凝土减水剂的生产工艺和原料配比,进行了不同配比生产的水泥与聚羧酸型混凝土减水剂的适应性试验。结果表明:熟料C_3A含量低于8.0%以下时,其进一步降低对聚羧酸型混凝土减水剂适应性影响较小;在生产1.0‰掺量的水泥助磨剂时,醇胺类有机物制得的水泥助磨剂,均具有明显的提高水泥早期强度和后期强度的作用;工业盐加入助磨剂后对水泥与聚羧酸型混凝土减水剂的适应性影响不明显;水泥中立磨粉磨的矿粉掺加量为70.0%时水泥与聚羧酸型混凝土减水剂的适应性急剧变差;掺加石灰石、炉渣、粉煤灰后水泥与聚羧酸型混凝土减水剂的适应性会随着掺加量的增加逐渐变差。     

新型高效混凝土减水剂的研究进展

文章简要回顾了近年来的新型高效混凝土减水剂研究现状,阐述了包括多环芳烃、氨基磺酸、聚羧酸及改性木质素磺酸盐等几种主要类型的新型高效减水剂的合成技术、性能特点及应用现状,结合目前国内高效减水剂的研究现状,展望了高效减水剂的发展方向,认为开发减水率更高、性能更优异、经济性更好的新产品是今后高效混凝土减水剂发展的主要方向.     

碱对掺萘系减水剂混凝土的性能影响

本文以五种不同厂家生产的萘系减水剂为研究对象,研究了碱对混凝土流动性和抗压强度的影响,从液体表面张力角度说明了碱对混凝土性能提高的作用机理.研究表明,碱对萘系减水剂混凝土流动性和抗压强度都有提高,但对不同厂家生产的减水剂作用效果不同,碱对萘系减水剂作用效果是具有选择性的.同配比条件下,碱的掺入能降低混凝土综合成本.     

不同种类减水剂对泡沫混凝土性能影响研究

对不同水灰比、不同种类减水剂泡沫混凝土进行研究。在低水灰比情况下,水灰比越大,泡沫混凝土的性能越好。通过掺入减水剂、降低水灰比可以改善泡沫混凝土性能。     

三聚氰胺系高效减水剂的研究进展与展望

综述了三聚氰胺系高效减水剂的性能及合成工艺，介绍了该领域国内外研究发展现状。指出其研究发展方向是降低原料成本，优化合成反应的工艺，深入研究合成反应机理及其对混凝土的减水增强作用机理，为三聚氰胺系减水剂的应用提供依据。     

Synthesis and properties of water‐soluble sulfonated acetone–formaldehyde resin

Water‐soluble sulfonated acetone–formaldehyde (SAF) resins were synthesized by the reaction among acetone, formaldehyde, and sodium bisulfite. The factors affecting the properties of SAF resins and optimum conditions of preparation were investigated. The SAF resins prepared under proper conditions have good water solubility and high performance as a superplasticizer used in concrete. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3248–3250, 2004     

Water‐soluble sulfonated phenolic resins. III. Effects of degree of sulfonation and molecular weight on concrete workability

The effects of the degree of sulfonation (DS) and molecular weight (MW) of sulfonated phenolic resins (SPF) on the flow properties of cementitious materials were investigated. SPF resin was prepared from phenol, formaldehyde, and sodium bisulfite through a four‐step reaction. It was found that an increase in either DS or MW would enhance the dispersion effects in the system. The results indicate that the fluidity of cement pastes and the workability of concrete increased with higher DS until the resin was fully sulfonated. For resins with sufficient sulfonation, the performance of cementitious materials would increase with increasing MW. Apparently, resins with MW of about 3 × 10⁴ are most effective in promoting concrete properties in terms of workability and compressive strength. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1762–1766, 2000     

三聚氰胺系高效减水剂的研究及应用

本文详细综述了三聚氰胺系高效减水剂的性能及合成工艺，介绍了该领域国内外研究发展现状。三聚氰胺系高效减水剂能够明显改善混凝土的工作性能，具有高减水率，早强效果显著、引气性低，生产过程对环境污染少等特点，是一种具有较大发展前景的高效减水剂。但由于其原料之一三聚氰胺价格较高，生产工艺复杂，影响反应的参数众多，使其质量难以控制，产品稳定性差等．限制了其发展和应用。针对三聚氰胺系减水剂的不足，其研究发展方向是降低原料成本，优化合成反应的工艺，深入研究合成反应机理及其对混凝土的减水增强作用机理，为三聚氰胺系减水剂的应用提供理论依据。     

新型具有梳状结构的氨基高效减水剂的研究

磺化蜜胺甲醛树脂氨基高效减水剂(AS)分散能力强、减水率高、价格低,但易离析泌水,将氨基减水剂改造成梳状氨基高效减水剂(ASP)解决了该问题。     

Ion exchange resins from phenol/formaldehyde resin‐modified lignin

Phenol/formaldehyde resin, commonly sulfonated, is used as ion exchanger. Lignin, which is the phenolic polymer matrix in wood, was isolated from olive stone biomass by alkaline hydrolysis of weak ether bonds (Kraft lignin, KRL). It was then hydroxymethylated (KRLH) with an aqueous solution of formaldehyde. Novolac resin (N) was synthesized from phenol and formaldehyde under acidic conditions. KRL or KRLH was incorporated into phenol/formaldehyde during polymerization (N‐KRL, N‐KRLH). The products of polymerization (N, N‐KRL and N‐KRLH) were sulfonated with concentrated H₂SO₄ (1:3 w/w as typical proportion according to literature or 1:6 w/w as an excess of H₂SO₄) and then cross‐linked with formaldehyde. The different products were characterized by IR spectroscopy, swelling in ethanol, acetone and in an aqueous solution of 1 N NaOH. The ion‐exchange capacity, the moisture retention capacity and the titration curves of the sulfonated and cured products were determined. The ion‐exchange capacity and the uptake of metal ions (mainly Co²⁺ and Cu²⁺) detected by atomic absorption spectroscopy, on the sulfonated materials, prepared in an excess of H₂SO₄, is higher for N‐KRL and N‐KRLH than for N and it takes place at the same rate or faster. The latter shows a medium acidic behaviour according to the titration curves, in contrast with the sulfonated N‐KRLH and N‐KRL which show a strongly acidic behaviour. © 2001 Society of Chemical Industry     

Synthesis and the effects of water-soluble sulfonated acetone-formaldehyde resin on the properties of concrete

Water-soluble sulfonated acetone-formaldehyde (SAF) resins were synthesized by the reaction among acetone, formaldehyde, and sodium bisulfite. The surface activity of SAF resins and their performance in concrete were evaluated. The effect of molecular weight (MW) of synthesized SAF resins on the performance of the superplasticized concrete was determined. The results showed that the SAF resin has the potential to be developed as a superplasticizer used in concrete.     

Water-soluble sulfonated amino–formaldehyde resins. IV. Melamine–urea resins: Synthesis and properties

The factors affecting the preparation and the properties of sulfonated melamine urea–for-maldehyde resins were studied. The resins weresynthesized using a four-step procedure previously used in preparing sulfonated melamine formaldehyde resins. The melamine–urea resins required higher hydroxymethylation and condensation temperatures as the percentage of urea increased. The molecular weight distribution of the prepared resins revealed the formation of low molecular weight species in increasing amounts with higher percentages of urea. The effectiveness of the prepared resins as dispersants for concrete mixes was found to be lower than the pure melamine resins; however, it was possible to enhance them by raising the ratio of sulfonated groups in the resins.     

磺酸基邻苯二甲酰亚氨甲基酞菁铜的合成

酞菁类化合物能改善塑料制品的性能 ,提高其热稳定性。以苯酐、脲为原料进行固相反应合成了邻苯二甲酰亚胺 (N) ,进而与甲醛反应生成 N -羟甲基邻苯二甲酰亚胺 (H) ,然后经过硫酸和发烟硫酸磺化 ,生成了磺酸基邻苯二甲酰亚氨甲基酞菁酮 (S)。对于所合成的产物进行了结构认证 ,对合成条件也进行了优化。固相反应合成 N条件容易控制 ,节省了溶剂 ,避免了溶剂法带来的副反应以及后处理和副产品的分离 ,产率达到了 95 %。用甲醛法合成 H中 ,发现 p H为重要的参数 ,产率为 96% ,条件温和、稳定。合成 S时 ,发烟硫酸的量和反应温度是影响产率的关键因素     

Synthesis,characterization, and metal adsorption properties of tannin–phenol–formaldehyde resins produced using tannin from dried fruit of Terminalia chebula (Aralu)

In this study, tannin extracted from Terminalia chebula (Aralu) was used to produce tannin–phenol–formaldehyde resins. They were produced to obtain resins with different tannin to phenol ratio in an attempt to optimize the ion exchange capacities of resins produced. The resins made were sulfonated to improve their properties further. Bivalent cations, such as Zn²⁺, Pb²⁺, Ca²⁺, Mg²⁺, and Cu²⁺, were used to estimate the adsorption properties of both unsulfonated and sulfonated resins. The glass transitions of representative resins were estimated using differential scanning calorimeter thermograms. Fourier transform infrared spectroscopic analysis was used to gauge changes on resins by sulfonation and adsorption of cations. The glass transition values of unsulfonated, sulfonated, and metal‐adsorbed sulfonated resins showed a similar increasing trend with the increase of phenol content in the resin. The glass transition temperature values reach a plateau beyond the tannin/phenol ratio of 1 : 0.5, indicating the formation of large molar masses facilitating entanglements beyond that ratio. The phenol ratio of 1 : 0.5 has shown the highest adsorption capacity for all the metal ions used. The highest adsorption capacity was shown for sulfonated tannin–phenol–formaldehyde resin with the tannin/phenol ratio of 1 : 0.5 for Pb²⁺, which is 0.610 meq/g. The adsorption equilibrium data obtained using the column technique were found fitting Freundlich isotherm. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010