引气剂对硫铝酸盐水泥混凝土硫酸盐结晶破坏的影响
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摘要
引气剂是常用于混凝土冻融破坏中提高混凝土抗冻性能的一种化学外加剂,其作用机理是在混凝土搅拌过程中引入大量气泡来改变混凝土的孔隙结构,从而降低冻融破坏中的结冰压力。混凝土的物理结晶破坏在破坏机理上与冻融破坏相似,都是混凝土孔隙中的液体在温度或湿度发生改变后形态发生改变从而挤压孔壁进而引起破坏,因此,从原理上看,引气剂的加入应该也能缓解混凝土的物理结晶破坏。本课题组在恒温、恒湿(温度(18±1)℃,相对湿度(50±5)%)的环境下,分别将掺入0?、0.5?引气剂的硫铝酸盐水泥混凝土试件(w/c=0.45)半浸泡在10%硫酸钠溶液中,对浸泡35 d、70 d、130 d后混凝土水分蒸发区的破坏形貌、强度和质量损失率及其孔径孔隙变化进行分析,从而探究引气剂对混凝土物理结晶破坏的影响。结果表明:掺入引气剂后,改变了混凝土的孔径分布及孔隙形状,从而可以降低盐结晶破坏压力的影响,提高硫铝酸盐水泥混凝土抵抗硫酸钠盐结晶破坏的能力。
Air-entraining agent is a chemical admixture used to improve frost resistance of concrete in concrete freeze-thaw damage. The mechanism of action is to introduce a large number of bubbles in the concrete mixing process to change the pore structure of the concrete and then reduce the icing pressure in the freeze-thaw damage. The physical crystallization damage of concrete is similar to the freeze-thaw damage in the failure mechanism. It is the change of the shape of the liquid in the pores of the concrete after the temperature or humidity changes. Therefore, in theory, the addition of air entraining agent should also alleviate the physical crystallization damage of concrete.So,in the environment of constant temperature and humidity(temperature(18±1) ℃, relative humidity(50±5)%), sulphoaluminate cement concrete specimens with 0?, 0.5? air entraining agent were partially immersed in 10% sodium sulphate solution.The deformation morphology of concrete moisture evaporation zone, strength and mass loss rate and pore diameter change were analyzed after immersion for 35 d, 70 d and 130 d,in order to explore the effect of air entraining agent on the physical crystallization damage of concrete.The results show that the incorporation of air entraining agent will change the pore size distribution and pore shape of concrete. The proper amount of air entraining agent can improve the sulfate resistance of sulphoaluminate cement concrete, however, when the air entraining agent is excessively mixed, the concrete specimens became softer, which in turn leads to more severe strength loss.
Air-entraining agent is a chemical admixture used to improve frost resistance of concrete in concrete freeze-thaw damage. The mechanism of action is to introduce a large number of bubbles in the concrete mixing process to change the pore structure of the concrete and then reduce the icing pressure in the freeze-thaw damage. The physical crystallization damage of concrete is similar to the freeze-thaw damage in the failure mechanism. It is the change of the shape of the liquid in the pores of the concrete after the temperature or humidity changes. Therefore, in theory, the addition of air entraining agent should also alleviate the physical crystallization damage of concrete.So,in the environment of constant temperature and humidity(temperature(18±1) ℃, relative humidity(50±5)%), sulphoaluminate cement concrete specimens with 0?, 0.5? air entraining agent were partially immersed in 10% sodium sulphate solution.The deformation morphology of concrete moisture evaporation zone, strength and mass loss rate and pore diameter change were analyzed after immersion for 35 d, 70 d and 130 d,in order to explore the effect of air entraining agent on the physical crystallization damage of concrete.The results show that the incorporation of air entraining agent will change the pore size distribution and pore shape of concrete. The proper amount of air entraining agent can improve the sulfate resistance of sulphoaluminate cement concrete, however, when the air entraining agent is excessively mixed, the concrete specimens became softer, which in turn leads to more severe strength loss.
引文
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19 Scherer G W.Cement & Concrete Research,2004,34(9),1613.
20 Benavente D,Cueto N,Martínez-Martínez J,et al.Environmental Geology,2007,52(2),215.
2 Rivas T,Alvarez E,Mosquera M J,et al.Construction & Building Materials,2010,24(5),766.
3 Benavente D,Cura M A G D,Fort R,et al.Engineering Geology,2004,74(1-2),113.
4 Espinosa-Marzal R M,Scherer G W.Environmental Earth Sciences,2009,56(3-4),605.
5 张永存,李青宁.混凝土,2015(3),31.
6 张士萍,邓敏,吴建华,等.武汉理工大学学报,2008,30(6),56.
7 Stark D.Portland Cement Association,Skokie,Illinois,USA,2002,pp.28.
8 邓德华,刘赞群,Geert D S.硅酸盐学报,2012,40(2),175.
9 刘赞群,候乐,邓德华,等.硅酸盐学报,2017,45(11),1621.
10 刘赞群,胡文龙,邓德华,等.硅酸盐学报,2018,46(5),663.
11 刘赞群,李湘宁,邓德华,等.硅酸盐学报,2016,44(8),1173.
12 Yang C C,Cho S W,Wang L C.Materials Chemistry and Physics,2006,100(2-3),203.
13 Scherer G W.In:International Rilem Tc 186-ISA Workshop and Internal Sulfate Attack and Delayed Ettringite Formation.Villars,Switzerland,2002.
14 Benavente D,et al.Journal of Crystal Growth,2004,260(3-4),532.
15 Steiger,M .Journal of Crystal Growth,2005,282(3-4),455.
16 Cultrone G,Russo L G,Calabrò C,et al.Environmental Geology,2008,54(6),1271.
17 Espinosa R M,Franke L,Deckelmann G.Construction & Building Materials,2008,22(7),1350.
18 Ruedrich J,Siegesmund S.Environmental Geology,2007,52(2),225.
19 Scherer G W.Cement & Concrete Research,2004,34(9),1613.
20 Benavente D,Cueto N,Martínez-Martínez J,et al.Environmental Geology,2007,52(2),215.