养护方式对活性氧化镁水泥水化硬化性能的影响

Effects of Curing Methods on Hydration-Hardening Performance of Reactive MgO Cement

活性氧化镁水泥(RMC)由MgO与水和CO_(2)反应而凝结硬化,是一种近年来备受关注的新型胶凝材料。RMC样品水化、碳化过程受养护方式和含水率影响显著,本文对比研究了标准养护((20±1)℃、95%相对湿度)、水养((20±1)℃)和碳化养护((20±3)℃、70%相对湿度、20%(体积分数)CO_(2))对水灰比为0.5、0.6、0.7的RMC的性能的影响,探究了其水化、碳化反应产物物相种类、含量及微观形貌特征。结果表明,在标准养护和水养条件下,反应3 d时各水灰比样品中MgO剩余含量为10%~15%(质量分数),反应14 d时MgO几乎没有剩余。当水灰比为0.6时,标准养护和水养14 d时净浆抗压强度分别为7.7和3.2 MPa。碳化养护下净浆强度优于标准养护和水养下净浆(3 d时三者抗压强度分别为16.19、0.42和0.43 MPa,14 d时分别为22.34、7.46和7.23 MPa);定量分析结果显示,各水灰比净浆碳化养护产物主要是MgCO_(3)·3H_(2)O,水灰比为0.6时,样品中MgCO_(3)·3H_(2)O生成量比水灰比为0.5和0.7样品高12.12%和11.29%,这些针棒状MgCO_(3)·3H_(2)O相互搭接形成致密结构是该样品宏观抗压强度最优的主要原因。

Reactive MgO cement(RMC),which undergoes hardening through the reaction of MgO with water and CO_(2),is a novel cementitious material that has gained significant attention in recent years.The hydration and carbonation processes of RMC samples are significantly affected by the curing method and water content.This work compared the effects of standard curing((20±1)℃,95%relative humidity),water curing((20±1)℃),and carbonation curing((20±3)℃,70%relative humidity,20%(volume fraction)CO_(2))on the properties of RMC with water-cement ratio(w/c)of 0.5,0.6,and 0.7,respectively.The types and content of the phases of the hydration and carbonation reaction products as well as their micro-morphological characteristics were investigated.The results show that the residual content of MgO in samples is 10%~15%(mass fraction)at 3 d and disappears at 14 d under standard curing and water curing.When w/c is 0.6,the compressive strength of paste reaches 7.7 and 3.2 MPa at 14 d under standard curing and water curing,respectively.The strength of paste under carbonation curing is superior to that under standard curing and water curing(3 d compressive strength,16.19,0.42,and 0.43 MPa,14 d compressive strength,22.34,7.46 and 7.23 MPa).The quantitative analysis results show that the carbonation product is mainly MgCO_(3)·3H 2O.When w/c is 0.6,the content of MgCO_(3)·3H 2O is 12.12%and 11.29%higher than that of samples with w/c=0.5 and 0.7.The main reason for the optimal compressive strength could lies in that these needle-rod MgCO_(3)·3H 2O are bonded to each other form a dense microstructure.