两类典型碱活性岩石试体在碱溶液中的膨胀行为

为确定以Spratt硅质灰岩(SL岩石)和Pittsburg泥质白云质灰岩(PL岩石)为代表的两类典型碱活性岩石试体在碱性环境中的膨胀来源和发展评定岩石碱活性的方法,研究了不同条件下SL和PL岩石在砂浆和混凝土中的膨胀行为.研究结果表明:SL岩石在砂浆和混凝土中均呈高ASR膨胀性,尽管其中的少量白云石可发生去白云石化反应;决定PL岩石高膨胀性的机制是ACR,与传统的ASR有本质不同,尽管其中含有的少量微晶石英可参与与碱的反应并可能对岩石的膨胀有一定贡献.采用能保持岩石微观结构构造特征的颗粒尺寸是正确评估PL岩石碱活性的关键.利用ASR和ACR对粉煤灰等混合材及含锂化合物的不同响应,特别是LiOH的抑制ASR膨胀和引发ACR膨胀的双重效应,在实验室可以快速区别同时含有白云石和石英的灰岩类集料的活性来源.

Expansion Behavior of Two Kinds of Typical Alkali Reactive Rocks Specimen in Alkaline Solutions

Expansion behaviors of Spratt siliceous(SL)limestone and Pittsburg argillaceous dolomite-bearing(PL) limestone from Canada in Accelerated Mortar Bar(Test(AMBT)),Concrete Prism Test(CPT) and Concrete Microbar Test were studied. There are significant differences between the two rocks in the expansion behavior in different tests and in responses to the addition of sufficient amount of fly ash and LiOH,which are effective measures in controlling ASR expansion.SL limestone shows high expansion in both the AMBT and the CPT.By 30% replacement of cement with fly ash and LiOH the expansion of concrete microbar with SL limestone is reduced significantly.SL limestone is a high alkali-silica reactive limestone although the small amount of dolomite it contains might involve in reaction with alkali.PL limestone shows high and rapid expansion in the CPT,but little expansion in the AMBT.Fly ash and LiOH have no significant effect on controlling expansion of concrete microbar with PL limestone.ACR(alkali-carbonate reaction),which is very different from ASR(alkali-silica reaction),is the determining factor leading to the high expansion of PL limestone although the small amount of quartz it contains might involve in reaction with alkali and possibly contributes to the final expansion.It is critically important to use coarse particles that can maintain its original texture characteristics for proper evaluation of the alkali reactivity of PL limestone.The ASR and ACR in dolomite-bearing limestones could be classified in laboratory by using the different responses of ASR and ACR to fly ash and lithium chemicals,especially the duplex effect of LiOH on ASR and ACR.