预应力钢筒混凝土管砂浆保护层在水污染环境下的腐蚀与防护措施

胡浙安

【摘要】预应力钢筒混凝土管水泥砂浆保护层对管体起到防腐与保护作用，但在水污染环境日益严峻的形势下，仅仅依靠制作致密水泥砂浆保护层的防腐措施是不完善的，还应从改善水泥砂浆原材料组成着手，提高水泥砂浆自身的抗腐蚀性能和抗渗透能力，才能有效阻止有害物质的侵入。

【关键词】PCCP 保护层 防腐

Abstract: The cement-mortar coating of prestressed concrete cylinder pipe(PCCP) is adopted to the anti-corrosion and protection of PCCP. But in the increasingly serious condition of water pollution, it is imperfect to rely solely on the cement-mortar coating to prevent corrosion. Improving the composition of its raw materials of cement-mortar to raise the anti-corrosion and anti-infiltration ability can effectively prevent the encroachment of harmful substances

Key words: PCCP; coating; anti-corrosion

中图分类号：TU37 文献标识码：A 文章编号：

The Anti-corrosion and Protection Measures of the Cement-mortar Coating of Prestressed Concrete Cylinder Pipe in Water Pollution

HU Zhe-an

(Jinhua Polytechnic, Jinhua 321000, China)

Abstract: The cement-mortar coating of prestressed concrete cylinder pipe(PCCP) is adopted to the anti-corrosion and protection of PCCP. But in the increasingly serious condition of water pollution, it is imperfect to rely solely on the cement-mortar coating to prevent corrosion. Improving the composition of its raw materials of cement-mortar to raise the anti-corrosion and anti-infiltration ability can effectively prevent the encroachment of harmful substances

Key words: PCCP; coating; anti-corrosion

The Anti-corrosion and Protection Measures of the Cement-mortar Coating of Prestressed Concrete Cylinder Pipe in Water Pollution

The Anti-corrosion and Protection Measures of the Cement-mortar Coating of Prestressed Concrete Cylinder Pipe in Water Pollution

HU Zhe-an

(Jinhua Polytechnic, Jinhua 321000, China)

Abstract: The cement-mortar coating of prestressed concrete cylinder pipe(PCCP) is adopted to the anti-corrosion and protection of PCCP. But in the increasingly serious condition of water pollution, it is imperfect to rely solely on the cement-mortar coating to prevent corrosion. Improving the composition of its raw materials of cement-mortar to raise the anti-corrosion and anti-infiltration ability can effectively prevent the encroachment of harmful substances

Key words: PCCP; coating; anti-corrosion

预应力钢筒混凝土管砂浆保护层在水污染环境下的腐蚀与防护措施

The Anti-corrosion and Protection Measures of the Cement-mortar Coating of Prestressed Concrete Cylinder Pipe in Water Pollution

HU Zhe-an

(Jinhua Polytechnic, Jinhua 321000, China)

Abstract: The cement-mortar coating of prestressed concrete cylinder pipe(PCCP) is adopted to the anti-corrosion and protection of PCCP. But in the increasingly serious condition of water pollution, it is imperfect to rely solely on the cement-mortar coating to prevent corrosion. Improving the composition of its raw materials of cement-mortar to raise the anti-corrosion and anti-infiltration ability can effectively prevent the encroachment of harmful substances

Key words: PCCP; coating; anti-corrosion

The Anti-corrosion and Protection Measures of the Cement-mortar Coating of Prestressed Concrete Cylinder Pipe in Water Pollution

HU Zhe-an

(Jinhua Polytechnic, Jinhua 321000, China)

Abstract: The cement-mortar coating of prestressed concrete cylinder pipe(PCCP) is adopted to the anti-corrosion and protection of PCCP. But in the increasingly serious condition of water pollution, it is imperfect to rely solely on the cement-mortar coating to prevent corrosion. Improving the composition of its raw materials of cement-mortar to raise the anti-corrosion and anti-infiltration ability can effectively prevent the encroachment of harmful substances

Key words: PCCP; coating; anti-corrosion

The Anti-corrosion and Protection Measures of the Cement-mortar Coating of Prestressed Concrete Cylinder Pipe in Water Pollution

HU Zhe-an

(Jinhua Polytechnic, Jinhua 321000, China)

Abstract: The cement-mortar coating of prestressed concrete cylinder pipe(PCCP) is adopted to the anti-corrosion and protection of PCCP. But in the increasingly serious condition of water pollution, it is imperfect to rely solely on the cement-mortar coating to prevent corrosion. Improving the composition of its raw materials of cement-mortar to raise the anti-corrosion and anti-infiltration ability can effectively prevent the encroachment of harmful substances

Key words: PCCP; coating; anti-corrosion

The Anti-corrosion and Protection Measures of the Cement-mortar Coating of Prestressed Concrete Cylinder Pipe in Water Pollution

HU Zhe-an

(Jinhua Polytechnic, Jinhua 321000, China)

Abstract: The cement-mortar coating of prestressed concrete cylinder pipe(PCCP) is adopted to the anti-corrosion and protection of PCCP. But in the increasingly serious condition of water pollution, it is imperfect to rely solely on the cement-mortar coating to prevent corrosion. Improving the composition of its raw materials of cement-mortar to raise the anti-corrosion and anti-infiltration ability can effectively prevent the encroachment of harmful substances

Key words: PCCP; coating; anti-corrosion

1水污染環境现状分析

水污染是指水体因某种物质的介入，而导致其化学、物理、生物等方面特性的改变，从而影响水的有效利用，危害人体健康或者破坏生态环境，造成水质恶化的现象。水污染来源有三个方面： 一是生产性污染：如工业生产形成的三废(废水、废气、废渣)，农业生产造成农药残留（杀虫剂、除草剂等）。二是生活性污染：如垃圾、污水、粪尿等生活废弃物。 三是其他污染：如放射性废弃物和飘尘等。 在环境污染造成的经济损失中, 水污染的损失是大头。据央视《新闻1+1》报道，2011 年我国环境污染所造成的损失达2万多亿，占GDP 比重超6%，其中对建筑、特别是钢筋混凝土的腐蚀破坏所造成的危害与损失, 是重要组成部分。著名结构耐久性专家梅塔( P.K.Mehta) 教授，在总结世界50 年混凝土耐久性状况时说：“钢筋腐蚀是钢筋混凝土结构破坏的主要原因” [1]。可以说我国水环境污染, 已经成为影响以基础设施为主体的混凝土耐久性的重要因素之一。

2PCCP管砂浆保护层的制作与作用

预应力钢筒混凝土管（又称PCCP管）、SYG型预应力混凝土管（又称三阶段管）均采用管芯缠丝工艺，其水泥砂浆保护层是在管芯上缠绕环向预应力钢丝后采用辊射法、喷涂法或其他有效方式制作的。混凝土输水管（管芯缠丝工艺）生产时，在缠丝过程中要喷一层水泥净浆，这层水泥净浆将钢丝紧紧包裹，使钢丝钝化；缠丝后辊射砂浆保护层，辊射的同时再喷一层水泥净浆，这样使钢丝完全处于高碱性环境中，在砂浆硬化前钢丝表面可形成一层具有钝化作用的氧化铁保护膜，能起到有效的防腐作用。水泥砂浆保护层的制作不仅为管道中的预应力钢丝提供了碱环境，而且在很大程度上保护预应力钢筒混凝土管本身的结构强度，具有一定的防腐与保护的作用。

3输水管外保护层腐蚀机理

输水管外保护层结构的腐蚀包括水泥砂浆的腐蚀破坏和预应力钢丝的腐蚀。因输水管所处的环境不同，水的酸碱度(pH)及有害物质对保护层水泥砂浆及包裹在其内的预应力钢丝的侵蚀和破坏也不同。

3.1水的酸碱度(pH)与腐蚀性

由于保护层水泥砂浆和管芯混凝土中含有一定数量的氢氧化钙, 因此具有强碱性(pH≥12.5) ,使其内的预应力钢丝及钢筒的表面产生一层以致密的氧化物Fe3O4为主的钝化膜,对预应力钢丝及钢筒起到较好的保护作用。但是，当PCCP 管道处于酸性、含腐蚀性CO2 及其它腐蚀环境时，所有酸性水都能“中和”保护层水泥砂浆和管芯混凝土中的碱, 从而损害保护层水泥砂浆的防护作用，同时也破坏钢筋的钝化状态、促进钢筋腐蚀。表1是一个综合结果, 可作参考。

表1 水的pH与腐蚀性分级(对钢筋混凝土)

3.2水中有害离子的腐蚀作用与分级标准

对钢筋混凝土有腐蚀破坏作用的盐类, 主要有氯盐、硫酸盐、镁盐、铵(氨) 盐等。不同的盐类，对水泥砂浆（混凝土）及预应力钢丝（钢筒）的腐蚀方式和程度有所不同。

①氯盐的电化学腐蚀。

氯盐(氯离子Cl- )主要是腐蚀混凝土中的钢筋。 腐蚀性的水溶液中含有大量的Cl－，当其量超过临界值时，便会透过水泥砂浆保护层到达并吸附于预应力钢丝的表面，使钢丝周围的pH值迅速降到4以下，破坏钢丝表面的钝化保护膜，露出铁基体，与尚完好的钝化膜区域之间构成电位差，形成“腐蚀电池”，在孔隙中水和氧气的作用下很快产生破坏性的铁锈( Fe2O3·nH2O晶体) 。据资料报道，美国在最近的50年中敷设使用的预应力钢筒混凝土管道已发生了多起管道破坏事故，而且大多数的破坏是由外部环境对预应力钢丝腐蚀所致[2]。

②硫酸盐的化学膨胀侵蚀。

硫酸盐(SO42-)主要破坏混凝土, 同时也腐蚀钢筋。环境水中的SO42-进入混凝土内部，与水泥的固相发生化学反应，生成难溶的盐矿物类-钙矾石和二水石膏，然后吸收大量的水而体积膨胀，造成混凝土的破坏。当溶液中SO42-浓度较低时，其反应式为：

3CaO·Al2O3·13H2O+ 2Ca(OH)2+Na2SO4+20H2O=3CaO·Al2O3·3CaSO4·31H2O+ 6NaOH

反应产物水化硫铝酸钙含有较多的结晶体，体积比水化铝酸钙增加2.5 倍以上。当溶液中硫酸根离子浓度较高时，其反应式为：

Ca(OH)2 + SO42- →CaSO4 +OH-

以上反应物的体积膨胀可达1～2倍,且所生成的CaSO4可进一步与混凝土中的铝酸三钙起反应,产生含更多结晶水的大分子产物,体积又会增加2倍左右。

③可溶性盐的的物理膨胀侵蚀

一是盐结晶膨胀。镁盐、铵盐、硫酸盐等可溶性盐类，随环境水渗入混凝土内部的毛细孔、微孔内，当水分蒸发时，浓度提高，盐就会结晶出来，盐结晶生长过程发生体积膨胀，使混凝土膨胀或粉化、脱落。二是盐的晶变膨胀。硫酸盐和氯盐，随着温度的变化，可能发生晶变或含不同的结晶水，因而体积也随之变化。其中，硫酸钠的晶变体积可膨胀3倍多。如果盐深入混凝土内发生晶变，就会引起混凝土结构的破坏。另外， Mg2+ 、NH4+会置换水泥水化物Ca(OH)2中的钙, 产生的CaCl2 易溶于水, 置换产生的Mg(OH)2松软无粘结力, 使混凝土丧失强度。

表2列出了分级标准( 参考) , 应该指出, 这是对通常水的腐蚀分级。污染水的成分是复杂的, 有机物分解的产物、重金属离子等, 也可能腐蚀钢筋混凝土。

表2 水中有害离子的腐蚀分级标准（对钢筋混凝土)

4输水管保护层防护措施

由上述分析可知，保护层水泥砂浆的腐蚀是由水或腐蚀性的水溶液渗入水泥砂浆内部造成的。PCCP 管道在运行过程中，当处于酸性、含腐蚀性CO2 及其它腐蚀环境时，土壤和地下水中的腐蚀性介质会侵入保护层和混凝土层，抵达钢丝和钢筒表面，侵入的腐蚀性介质会破坏钢丝钝化层而引起腐蚀，造成钢丝断裂而影响管道的机械强度，严重时会出现爆管的情况。为增强PCCP 管水泥砂浆保护层对环境水中有害物质的抵御能力，有学者提出采用低水灰比和添加专用外加剂改善砂浆性能，以保证砂浆层对环境有害成分形成一道有效的屏障。然而，砂浆层的屏障效果不理想，受污染环境水中的Cl-、SO42-在物理、化学膨胀及电化学腐蚀等的作用下，能渗入水泥砂浆层到达预应力钢丝表面，降低钢丝周围的pH，破坏钢丝表面的钝化保护膜引起钢丝腐蚀。因此，仅仅依靠制作致密水泥砂浆保护层的防腐措施是不完善的，还应从改善水泥砂浆原材料组成着手，提高水泥砂浆自身的抗腐蚀性能和抗渗透能力，以阻止有害物质的侵入。另外，还可在水泥砂浆表面上增设防腐隔离层以进一步减少或抵御环境中的有害物质进入砂浆内，并对砂浆层自身进行保护。

4.1粉煤灰防腐水泥砂浆

在PCCP管保护层水泥砂浆中,大量（等量取代50%～70%）掺入粉煤灰后,不仅能改善水泥砂浆的工作性能，还可有效地提高水泥砂浆在硫酸盐和氯盐等水污染环境中的耐蚀系数。其作用机理可归纳如下：

① 粉煤灰属于火山灰质混合材料，可降低水泥中的C3A 和C3S 的含量， 相当于在水泥砂浆中所用的胶结材料是低C3A 和低C3S 的水泥。

② 粉煤灰由于经过机械磨细活化, 优化了粉煤灰的颗粒度分布和颗粒级配，改善了颗粒的表面形貌，其火山灰反应活性得到了显著的提高。能与水泥水化过程中产生的Ca（OH）2发生化学反应，生成C-S-H 凝胶，对硬化体结构中毛细孔的起到填充作用，提高水泥砂浆的强度。

③ Ca（OH）2的消除将减轻其膨胀危害，强度的提高则能限制其膨胀。C-S-H 凝胶的产生使结构致密，降低了SO42-渗透进水泥砂浆保护层的能力。

4.2粉煤灰防腐聚酯砂浆

粉煤灰防腐聚酯砂浆是用聚酯树脂为粘结剂, 用粉煤灰中漂珠做粉料, 配以砂子调制而成。砂浆的硬化是通过在树脂中加人引发剂、促进剂和助促进剂来完成的。

① 性能特点

粉煤灰防腐聚酯砂浆在常温甚至低温下都能快速硬化, 在空气中或在水中也能快速硬化成型。用漂珠做聚酯砂浆的粉料，可以大大降低聚酯砂浆的收缩率，其收缩率仅为普通聚酯砂浆收缩率的1%，从而使粉煤灰聚酯砂浆具有良好的机械性能、防腐性能、施工性能及较低的成本。

② 性能指标

其主要性能指标见表3。

表3 粉煤灰防腐聚酯砂浆力学及防腐蚀性能

4.3环氧煤沥青涂料外防腐

为了增强管道的防腐能力，提高管道工程的安全性和耐久性，维持PCCP 管50年或更长的使用寿命，在管道外壁加涂防腐涂层是十分必要和可行的[3]。从国内常用的防腐涂料，如环氧煤沥青涂料、聚脲涂料、聚氨酯涂料和橡胶涂料的对比试验结果看，环氧煤沥青涂料耐化学介质侵蚀能力最好[4]，成为PCCP 外壁防腐采用的优选材料。

① 性能特点

环氧煤沥青防腐涂料综合了环氧树脂和煤沥青的优点，同时利用煤焦油沥青进行改性，结构上互为穿插，形成互穿网络，使防腐层具有优异的抗化学介质腐蚀性和渗透性，良好的物理机械性能，以及优异的电绝缘性、抗水渗透性等优良性能。

② PCCP外防腐的制作

防腐涂料的涂装施工可采用刷涂、滚涂、空气喷涂和高压无气喷涂等方法。宜根据涂装场所的条件、被涂物形状大小、涂料品种及设计要求等，选择合适的涂装方法。

③ 工程实例

广州市西江引水工程，是国内第三大引水工程，于2010年9月完工通水。全线主管使用PCCP（预应力钢筒混凝土管）和钢管两种，在70多公里的管廊中，PCCP管就走了53公里，PCCP 管外壁采用环氧煤沥青进行防腐，防腐层设计平均干膜厚度为500 μm。

参考文献

[1]Mehta P K, Burrows R W. Building durable structuresin the 21st centur y[R] .Concrete International,March, 2001.57～63.

[2]余洪方．预应力钢筒混凝土管道的腐蚀与控制[J]．混凝土与水泥制品.2000（3）：28

[3]孙绍平,王贯明,韩扬.  预应力钢筒混凝土管(PCCP)耐久性探讨[J]. 特种结构. 2005(03)

[4]杜建伟等.盐碱地区埋地PCCP外防腐涂料的筛选研究[J]. 给水排水.2011(05)

The Anti-corrosion and Protection Measures of the Cement-mortar Coating of Prestressed Concrete Cylinder Pipe in Water Pollution

HU Zhe-an

(Jinhua Polytechnic, Jinhua 321000, China)

Abstract: The cement-mortar coating of prestressed concrete cylinder pipe(PCCP) is adopted to the anti-corrosion and protection of PCCP. But in the increasingly serious condition of water pollution, it is imperfect to rely solely on the cement-mortar coating to prevent corrosion. Improving the composition of its raw materials of cement-mortar to raise the anti-corrosion and anti-infiltration ability can effectively prevent the encroachment of harmful substances

Key words: PCCP; coating; anti-corrosion

预应力钢筒混凝土管（Prestressed concrete cylinder pipe）水泥砂浆保护层对管体起到防腐与保护作用，但在水污染环境日益严峻的形势下，仅仅依靠制作致密水泥砂浆保护层的防腐措施是不完善的，还The Anti-corrosion and Protection Measures of the Cement-mortar Coating of Prestressed Concrete Cylinder Pipe in Water Pollution

HU Zhe-an

(Jinhua Polytechnic, Jinhua 321000, China)

Abstract: The cement-mortar coating of prestressed concrete cylinder pipe(PCCP) is adopted to the anti-corrosion and protection of PCCP. But in the increasingly serious condition of water pollution, it is imperfect to rely solely on the cement-mortar coating to prevent corrosion. Improving the composition of its raw materials of cement-mortar to raise the anti-corrosion and anti-infiltration ability can effectively prevent the encroachment of harmful substances

Key words: PCCP; coating; anti-corrosion

The Anti-corrosion and Protection Measures of the Cement-mortar Coating of Prestressed Concrete Cylinder Pipe in Water Pollution

HU Zhe-an

(Jinhua Polytechnic, Jinhua 321000, China)

Abstract: The cement-mortar coating of prestressed concrete cylinder pipe(PCCP) is adopted to the anti-corrosion and protection of PCCP. But in the increasingly serious condition of water pollution, it is imperfect to rely solely on the cement-mortar coating to prevent corrosion. Improving the composition of its raw materials of cement-mortar to raise the anti-corrosion and anti-infiltration ability can effectively prevent the encroachment of harmful substances

Key words: PCCP; coating; anti-corrosion

The Anti-corrosion and Protection Measures of the Cement-mortar Coating of Prestressed Concrete Cylinder Pipe in Water Pollution

HU Zhe-an

(Jinhua Polytechnic, Jinhua 321000, China)

Abstract: The cement-mortar coating of prestressed concrete cylinder pipe(PCCP) is adopted to the anti-corrosion and protection of PCCP. But in the increasingly serious condition of water pollution, it is imperfect to rely solely on the cement-mortar coating to prevent corrosion. Improving the composition of its raw materials of cement-mortar to raise the anti-corrosion and anti-infiltration ability can effectively prevent the encroachment of harmful substances

Key words: PCCP; coating; anti-corrosion

The Anti-corrosion and Protection Measures of the Cement-mortar Coating of Prestressed Concrete Cylinder Pipe in Water Pollution

HU Zhe-an

(Jinhua Polytechnic, Jinhua 321000, China)

Abstract: The cement-mortar coating of prestressed concrete cylinder pipe(PCCP) is adopted to the anti-corrosion and protection of PCCP. But in the increasingly serious condition of water pollution, it is imperfect to rely solely on the cement-mortar coating to prevent corrosion. Improving the composition of its raw materials of cement-mortar to raise the anti-corrosion and anti-infiltration ability can effectively prevent the encroachment of harmful substances

Key words: PCCP; coating; anti-corrosion