高活性MgO对低温氯氧镁水泥物相及性能的影响
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摘要
环境温度和氧化镁活性对氯氧镁水泥(MOC)的水化产物形成有重要的影响。对不同温度(5～20℃)MOC水化产物变化的研究表明,当制备和养护温度低于15℃时,MOC水化产物开始出现3相[3Mg(OH)2·MgCl_2·8H_2O],温度越低,MOC中3相的相对含量越高,而在MOC材料中起强度作用的5相[5Mg(OH)_2·MgCl_2·8H_2O]的相对含量越低,导致低温制备MOC材料早期强度明显降低。提高MgO的活性可以促进低温MOC水化相选择性生成单一的5相,温度越低,生成单一5相的所需MgO的活性越高。同时发现,当利用高活性MgO代替一定比例菱苦土为原料时,MOC低温水化反应速率会明显加快,水化产物选择性生成单一的5相,MOC抗压强度尤其是早期强度明显提高。
The environment temperature and magnesium oxide activity have important influences on the formation of hydrated products of magnesium oxychloride cement(MOC). Based on the MOC hydrate phase change at different temperatures(i.e.,5-20 ℃), the MOC hydration product begins to appear 3-phase substance(i.e., 3 Mg(OH)_2·MgCl_2·8 H_2O) when the curing temperature is lower than 15 ℃. The lower the temperature is, the higher the relative content of 3-phase substance in MOC, and the lower the relative content of 5-phase substance(i.e., 5 Mg(OH)_2·MgCl_2·8 H_2O) will be. This affects the strength of MOC materials, leading to a significant reduction in the early strength of MOC materials prepared at a low temperature. Increasing the activity of MgO can promote the selective formation of a single 5-phase substance by the hydration phase of MOC at a low temperature. A lower temperature gives a higher activity of MgO needed to generate a single 5-phase substance. Also, the hydration reaction rate of MOC accelerates at a low temperature, and the hydration products selectively generate a single 5-phase substance, and the compressive strength of MOC increases, especially the early strength, when MOC is prepared by replacing a certain proportion of magnesia with a high activity MgO.
The environment temperature and magnesium oxide activity have important influences on the formation of hydrated products of magnesium oxychloride cement(MOC). Based on the MOC hydrate phase change at different temperatures(i.e.,5-20 ℃), the MOC hydration product begins to appear 3-phase substance(i.e., 3 Mg(OH)_2·MgCl_2·8 H_2O) when the curing temperature is lower than 15 ℃. The lower the temperature is, the higher the relative content of 3-phase substance in MOC, and the lower the relative content of 5-phase substance(i.e., 5 Mg(OH)_2·MgCl_2·8 H_2O) will be. This affects the strength of MOC materials, leading to a significant reduction in the early strength of MOC materials prepared at a low temperature. Increasing the activity of MgO can promote the selective formation of a single 5-phase substance by the hydration phase of MOC at a low temperature. A lower temperature gives a higher activity of MgO needed to generate a single 5-phase substance. Also, the hydration reaction rate of MOC accelerates at a low temperature, and the hydration products selectively generate a single 5-phase substance, and the compressive strength of MOC increases, especially the early strength, when MOC is prepared by replacing a certain proportion of magnesia with a high activity MgO.
引文
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[26]URWONGSE L,SORRELL C A.The System MgO-MgCl2?H2O at23℃[J].J Am Ceram Soc,2010,63:501?504.
[27]MARAVELAKI KALAITZAKI P,MORAITOU G.Sorel's cement mortars:Decay susceptibility and effect on Pentelic marble[J].Cem Concr Res,1999,29(12):1929?1935.
[28]HE P P,CHI S P,TSANG D C W.Comparison of glass powder and pulverized fuel ash for improving the water resistance of magnesium oxychloride cement[J].Cem Concr Compos,2018,86:98?109.
[2]LI Z,CHAU C K.Influence of molar ratios on properties of magnesium oxychloride cement[J].Cem Concr Res,2007,37(6):866?870.
[3]LI Y,YU H,ZHENG L,et al.Compressive strength of fly ash magnesium oxychloride cement containing granite wastes[J].Constr Build Mater,2013,38(1):1?7.
[4]LIU Z,BALONIS M,HUANG J,et al.The influence of composition and temperature on hydrated phase assemblages in magnesium oxychloride cements[J].J Am Ceram Soc,2017,100(7):3246?3261.
[5]CHAU C K,LI Z.Microstructures of magnesium oxychloride[J].Mater Struct,2008,41(5):853?862.
[6]LIU Z,WANG S,HUANG J,et al.Experimental investigation on the properties and microstructure of magnesium oxychloride cement prepared with caustic magnesite and dolomite[J].Constr Build Mater,2015,85:247?255.
[7]HE P,CHI S P,TSANG D C W.Effect of pulverized fuel ash and CO2,curing on the water resistance of magnesium oxychloride cement(MOC)[J].Cem Concr Res,2017,97:115?122.
[8]XU B,MA H,HU C,et al.Influence of curing regimes on mechanical properties of magnesium oxychloride cement-based composites[J].Constr Build Mater,2016,102:613-619.
[9]TAN Y,LIU Y,GROVER L.Effect of phosphoric acid on the properties of magnesium oxychloride cement as a biomaterial[J].Cem Concr Res,2014,56:69?74.
[10]HU C,XU B,MA H,et al.Micromechanical investigation of magnesium oxychloride cement paste[J].Constr Build Mater,2016,105:496?502.
[11]SGLAVO V M,CONCIA,CECCATO R,et al.Influence of curing temperature on the evolution of magnesium oxychloride cement[J].JMater Sci,2011,46(20):6726?6733.
[12]ZHANG X,GE S,WANG H,et al.Effect of 5-phase seed crystal on the mechanical properties and microstructure of magnesium oxychloride cement[J].Constr Build Mater,2017,150:409?417.
[13]COLE W F,DEMEDIUK T.X-Ray,thermal,and Dehydration studies on Magnesium oxychlorides[J].Australian J Chem,1955,8:234?251.
[14]MATKOVIC B,POPOVIC S,ROGIC V,et al.Reaction products in magnesium oxychloride cement pastes.System MgO?MgCl2?H2O[J].J Am Ceram Soc,1977,60:504?507.
[15]文静,余红发,吴成友,等.氯氧镁水泥水化历程的影响因素及水化动力学[J].硅酸盐学报,2013,41(5):588?596.WEN J,YU H,WU C,et al.J Chin Ceram Soc,2013,41(5):588?596
[16]BIRCHAL V S S,ROCHA S D F,CIMINELLI V S T.The effect of magnesite calcination conditions on magnesia hydration[J].Miner Eng,2000,13(14):1629?1633.
[17]WANG C Y,DU Z M,CONG X M,et al.Thermal decomposition of alkali magnesium carbonate[J].Appl Chem Eng,2008,37(6):657?660.
[18]QIN Z Y,QIN L H,ZHANG L M,et al.Study of thermal decomposition of alkali magnesium carbonate by XRD,TG,DSCand FTIR methods[J].Non-metallic Ore,2012,35(4):52?53.
[19]DONG J M,YU H F,ZHANG L M.Study on experimental conditions of hydration methods of determining active magnesium oxide content[J].J Salt Lake Res,2010,18(1):38?41
[20]SANDELL E B,KOLTHOFF I M.Textbook of Quantitative Inorganic Analysis[M].New York:Macmillan Co.,1952:548.
[21]WU C,CHEN W,ZHANG H,et al.The hydration mechanism and performance of Modified magnesium oxysulfate cement by tartaric acid[J].Constr Build Mater,2017,144:516?524.
[22]JCPDS-Joint Committee on Powder Diffraction Standards-PDFPowder Diffraction File.
[23]CHAU C K,LI Z.Accelerated Reactivity assessment of light burnt magnesium oxide[J].J Am Ceram Soc,2010,91(5):1640?1645.
[24]DENG D,ZHANG C.The formation mechanism of the hydrate phases in magnesium oxychloride cement[J].Cem Concr Res,1999,29(9):1365?1371.
[25]ALTINER M,YILDIRIM M.Study of using dolomite as starting material resource to produce magnesium oxychloride cement[J].JAdv Concr Technol,2017,15(6):269-277.
[26]URWONGSE L,SORRELL C A.The System MgO-MgCl2?H2O at23℃[J].J Am Ceram Soc,2010,63:501?504.
[27]MARAVELAKI KALAITZAKI P,MORAITOU G.Sorel's cement mortars:Decay susceptibility and effect on Pentelic marble[J].Cem Concr Res,1999,29(12):1929?1935.
[28]HE P P,CHI S P,TSANG D C W.Comparison of glass powder and pulverized fuel ash for improving the water resistance of magnesium oxychloride cement[J].Cem Concr Compos,2018,86:98?109.