土壤聚合物和水泥砂浆的碱-硅反应

Investigation on ASR of Geopolymer Mortar and Cement Mortar with Mineral Admixtures

为了比较分析土壤聚合物和含有矿物掺合料的水泥砂浆的碱-硅反应(ASR)问题。参照我国水工混凝土标准DL/T5151-2001和ASTM C 441-97进行了抑制骨料碱活性效能的试验。试验结果表明:掺加矿物掺合料能够有效地抑制ASR。当5%硅粉、20%粉煤灰和40%磨细矿渣共同掺入砂浆时,90d的膨胀率仅有0.13%,即降低了81.9%。对加压挤出的硬化水泥浆体孔溶液进行化学分析,发现矿物掺合料的加入降低了孔溶液中钾、钠离子和氢氧根离子的浓度,这是减少ASR危害的根本原因。土壤聚合物是一种无定形的无机材料,由偏高岭土、硅粉在高碱条件下制得。土壤聚合物的碱含量很高,达到12.1%,但土壤聚合物砂浆没有产生任何膨胀,其原因是土壤聚合物中没有充足的游离碱与活性骨料反应,因此不会产生危害性ASR。

The alkali-silica reaction （ASR） of geopolymer mortar and cement mortar with mineral admixtures was experimentally compared, the test methods used were ASTM C 441-97 and DL/T 5151-2001. The results prove that mineral admixtures can effectively restrain ASR, when three kinds of mineral admixtures, i.e. silica fume, fly ash, and ground granulated blast-furnace slag （GGBS）, were used together, a compound effect was brought abont and which will be more effective to restrain ASR, e.g. reducing mortar expansion 81.9% at 90 days. Chemical analysis of the pore solution shows that mineral admixtures reduce the concentrations of hydroxyl, potassium and sodium ions. so that the damages fiom ASR were decreased. And the geopolymer, an amorphous inorganic material, was prepared with metakaolin and silica fume in the condition of high pH. Geopolymer mortar did not generate any expansion even with alkali contents as high as 12.1%. The reason was that there was no enough free alkali to react with active aggregates in geopolymer.