天然沸石对碱-骨料反应的抑制及其机理

Effect and Mechanism of Natural Zeolite for Preventing Expansion due to Alkali-Aggregate Reaction

以30％的天然沸石、65％的水泥熟料及5％的石膏共同磨细以后,得到沸石水泥(Z.C),其碱的总含量为1.42％(K_2O1.58％,Na_2O0.38％)。用NaOH调整水泥中碱的总含量到1.82％,以硬玻璃及古铜辉石安山岩为活性骨料和石英砂为非活性骨料,按砂浆棒方法测定碱-骨料反应的膨胀。Z.C与硬玻璃的砂浆棒膨胀值仅0.004％(28d龄期)及-0.003％(90d龄期),而波特兰水泥(总含碱量0.62％)与上述同一活性骨料的砂浆棒试验,其膨胀值是0.599％(90d龄期)。而Z.C与非活性骨料石英砂的砂浆棒膨胀值,在28d与90d龄期分别是-0.003％和-0.004％。也就是说,Z.C与活性骨料配制混凝土,不用担心由于碱-骨料反应而造成破坏。在本研究中发现天然沸石能通过离子交换而吸收碱离子,这是Z.C能抑制碱-骨料反应的原因。

The effect of natural zeolite on preventing expansion due to alkali- aggregate reaction (AAR) and its mechanism are investigaed.The Portland cement with 30% of natural zeolite by mass is called zeolite cement (Z. C). The total alkalicontent in it is 1. 42% (K2O 1. 58% , Na2O 0. 38%). The alkali content is raised to 1. 82% by addingNaOH in the mortar. Hard glass is used as the reactive aggregate and sand as the non-reactive aggregate. The mortar bar method is used to determine the expansion due to AAR.The expansion of the mortar bar with Z. C and the reactive hard glass was 0. 004%(28d) and-0. 003%(90d). Using the Portland cement for the dam (0. 62% total alkli) gave an expansion of 0. 599%(90d). And, for the mortar bars with Z. C and non-reactive sand the expansion was-0. 003% (28d) and -0. 004%(90d) respectively. Thus, it is assured that there will be no damage from AAR when the concrete is made of Z. C with reactive aggregate.In the experiment, it is found that the natural zeolite can absorb the alkali ions by ion exchange, so that the AAR can be controlled.