碳化混凝土硫酸镁盐结晶破坏微观分析
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摘要
在恒温恒湿环境[温度(20±1)℃,相对湿度(60±5)%]条件下,对掺30%粉煤灰的混凝土试件(FA30,水灰比为0.45)和水灰比为0.55的混凝土试件(PC0.55)快速碳化20 d与未快速碳化的混凝土试件半浸泡在10%硫酸镁溶液中,浸泡150 d后混凝土试件水分蒸发区的破坏形貌、强度损失率及其微观进行分析。结果表明:碳化是混凝土蒸发区发生硫酸镁结晶的前提,碳化深度越大,混凝土破坏越严重。掺加粉煤灰的FA30比PC0.55更易碳化,强度损失率越大;快速碳化20d后,FA30碳化深度为15.4 mm,强度损失率为42.2%,PC0.55碳化深度为9.3 mm,强度损失率为20.5%。经过150 d浸泡后,未快速碳化的FA30的水分蒸发区表层10 mm也被碳化,试件出现了硫酸镁盐结晶破坏,强度损失率为22%,PC0.55水分蒸发区碳化不明显,强度没有损失。
The accelerated carbonation for 20-d concrete and non-carbonated concrete specimens were partially immersed in 10%MgSO_4 solution under constant conditions(i.e., T(20±1)℃, relative humidity(60±5)% and 150 d). The results show that concrete carbonation is the precondition of occurrence of MgSO_4 crystallization in the evaporation zone of concrete and larger carbonation depth causes severer concrete scaling. The carbonation depth of concrete with fly ash(FA) of 30% and a water to binder ratio of 0.55(FA30) is 15.4 mm, and that of the concrete with a water to Portland cement(PC) ratio of 0.55(PC0.55) is 9.3 mm after 20-d accelerated carbonation, and the compressive strength loss rates of FA30 and PC0.55 are 42.2% and 20.5% after 150-d partial immersion in MgSO_4 solution. For the non-carbonated FA30, the carbonation depth of evaporation zone of concrete specimen is approximately 10 mm after 150-d exposure, resulting in the compressive strength loss of 22%. However, the non-carbonated PC0.55 concrete does not show clear carbonation depth in the evaporation zone after 150-d exposure, and there is little compressive strength loss.
The accelerated carbonation for 20-d concrete and non-carbonated concrete specimens were partially immersed in 10%MgSO_4 solution under constant conditions(i.e., T(20±1)℃, relative humidity(60±5)% and 150 d). The results show that concrete carbonation is the precondition of occurrence of MgSO_4 crystallization in the evaporation zone of concrete and larger carbonation depth causes severer concrete scaling. The carbonation depth of concrete with fly ash(FA) of 30% and a water to binder ratio of 0.55(FA30) is 15.4 mm, and that of the concrete with a water to Portland cement(PC) ratio of 0.55(PC0.55) is 9.3 mm after 20-d accelerated carbonation, and the compressive strength loss rates of FA30 and PC0.55 are 42.2% and 20.5% after 150-d partial immersion in MgSO_4 solution. For the non-carbonated FA30, the carbonation depth of evaporation zone of concrete specimen is approximately 10 mm after 150-d exposure, resulting in the compressive strength loss of 22%. However, the non-carbonated PC0.55 concrete does not show clear carbonation depth in the evaporation zone after 150-d exposure, and there is little compressive strength loss.
引文
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[16]RUIZ-AGUDO E,MEES F,JACOBS P,et al.The role of saline solution properties on porous limestone salt weathering by magnesium and sodium sulfates[J].Environ Geol,2007,52(2):305-317.
[17]PEL L,HUININK H,KOPINGA K.Efflorescence pathway diagram:Understanding salt weathering[J].Constr Build Mater,2004,18(5):309-313.
[18]LIU Z,DENG D,et al.Chemical sulfate attack performance of partially exposed cement and cement+fly ash paste[J],Constr,Build,Mater,2012,28(1):230-237.
[2]HAYNES H,BASSUONI M T.Physical salt attack on concrete.Concrete International 2011,33(11):38-42.
[3]MICHAEL STEIGER,Crystal growth in porous materials-I:The crystallization pressure of large crystals[J].J Cryst Growth,2005,282(3/4):455-469.
[4]邓德华,刘赞群,GEERT D S.关于“混凝土硫酸盐结晶破坏”理论的研究进展[J].硅酸盐学报,2012,40(2):175-185.DENG Dehua,LIU Zanqun,GEERT D S,et al.J Chin Ceram Soc,2012,40(2):175-185.
[5]刘赞群,邓德华,Geert D S,等.“混凝土硫酸盐结晶破坏”微观分析(I)-水泥净浆[J].硅酸盐学报,2012,40(2):186-193.LIU Zanqun,DENG Dehua,GEERT D S,et al.J Chin Ceram Soc,2012,40(2):186-193.
[6]刘赞群,邓德华,Geert D S,等.“混凝土硫酸盐结晶破坏”微观分析(Ⅱ)-混凝土[J].硅酸盐学报,2012,40(5):631-637.LIU Zanqun,DENG Dehua,GEERT D S,et al.J Chin Ceram Soc,2012,40(5):631-637.
[7]刘赞群,李湘宁,邓德华,等.硫酸铝盐水泥与硅酸盐水泥净浆水分蒸发区硫酸盐破坏对比[J].硅酸盐学报,2016,44(8):1181-1185.LIU Zanqun,LI Xiangning,DENG Dehua,et al.J Chin Ceram Soc,2016,44(8):1181-1185.
[8]LIU Z,LI X,DENG D,et al.The role of Ca(OH)2 in sulfate salt weathering of ordinary concrete[J].Constr Build Mater,2016,123:127-134.
[9]LIU Z,LI X,DENG D,G De SCHUTTER,et al.The damage of calcium sulfoaluminate cement paste partially immersed in MgSO_4solution[J].Mater Struct,2016,49:719-727.
[10]刘赞群,候乐,邓德华,等.硫铝酸盐水泥净浆半浸泡碳酸钠溶液的破坏研究[J].硅酸盐学报,2017,45(5):639-643.LIU Zanqun,HOU Le,DENG Dehua,et al.J Chin Ceram Soc,2017,45(5):639-643.
[11]YOSHIDA N,MATSUNAMI Y,NAGAYAMA M.Salt weathering in residential concrete foundations exposed to sulfate-bearing ground[J].J Adv Concr Technol,2010,8(2):121-134.
[12]LIU Z,ZHANG F,DENG D,et al.Physical sulfate attack on concrete lining-A field case analysis[J].Case Studies Const Mater,2017(6):206-212.
[13]刘赞群,侯乐,邓德华,等.碳化混凝土硫酸钠盐结晶破坏研究[J]硅酸盐学报.2017,45(11):1610-1617.LIU Zanqun,HOU Le,DENG Dehua,et al.J Chin Ceram Soc,2017,45(11):1610-1617.
[14]SKALNY J P,ODLER I,MARCHAND J.Sulfate Attack on Concrete[M].Spon,London,2001:2.
[15]GEORGE W SCHERER.Crystallization in Pores[J].Cem Concr Res,1999,29(8):1348-1358.
[16]RUIZ-AGUDO E,MEES F,JACOBS P,et al.The role of saline solution properties on porous limestone salt weathering by magnesium and sodium sulfates[J].Environ Geol,2007,52(2):305-317.
[17]PEL L,HUININK H,KOPINGA K.Efflorescence pathway diagram:Understanding salt weathering[J].Constr Build Mater,2004,18(5):309-313.
[18]LIU Z,DENG D,et al.Chemical sulfate attack performance of partially exposed cement and cement+fly ash paste[J],Constr,Build,Mater,2012,28(1):230-237.