地聚物混凝土干燥收缩性能及活性氧化镁补偿收缩研究

Drying Shrinkage Performance of Geopolymer Concrete and Shrinkage Compensation of Active MgO

制备粉煤灰-矿渣基地聚物混凝土,并进行地聚物混凝土28 d抗压强度和干燥收缩测试,探究分析活性氧化镁含量、水玻璃模数、碱当量和矿渣含量对其抗压强度和干燥收缩的影响机理。结果表明:随着活性氧化镁掺量增大,地聚物混凝土28 d抗压强度下降,干燥收缩变形显著减小;与0%(质量分数,下同)活性氧化镁混凝土相比,掺量为3%、6%和9%时混凝土28 d抗压强度分别下降8.0%、8.2%和18.2%,干燥收缩分别减小21.5%、26.4%和38.2%,此外,当活性氧化镁掺量为3%和6%时,不仅有效补偿了干燥收缩,且抗压强度损失较小;随着水玻璃模数升高,地聚物混凝土28 d抗压强度和干燥收缩变形增大;随着碱当量升高,地聚物混凝土28 d抗压强度下降、干燥收缩变形增大;随着矿渣含量增加,地聚物混凝土28 d抗压强度增大、干燥收缩变形减小。综合考虑抗压强度及收缩的要求,建议实际应用中选择高活性、大掺量氧化镁,掺量宜控制在3%~6%。

A fly ash-slag-based geopolymer concrete was prepared,and the influence mechanism of active magnesia content,sodium silicate modulus,alkali equivalent and slag content on the compressive strength and drying shrinkage was explored and analyzed through 28 d compressive strength and drying shrinkage tests.The results show that with an increase of the active magnesia content,the 28 d compressive strength of the geopolymer concrete decreases,while the drying shrinkage deformation significantly diminishes.Compared with concrete specimen with 0%(mass fraction,the same bellow)active magnesium oxide content,concrete specimens with 3%,6% and 9% magnesium oxide show a decrease of 8.0%,8.2% and 18.2% in 28 d compressive strength,and a decrease of 21.5%,26.4% and 38.2% in drying shrinkage,respectively.In addition,when the content of active magnesium oxide is 3% and 6%,it not only effectively compensates for drying shrinkage,but also reduces the loss of compressive strength.As the sodium silicate modulus increases,the 28 d compressive strength and drying shrinkage deformation of the geopolymer concrete increase.With higher alkali equivalent,the 28 d compressive strength of the geopolymer concrete decreases while the drying shrinkage deformation increases.With an increase in slag content,the 28 d compressive strength of the geopolymer concrete increases,and the drying shrinkage deformation decreases.Taking into consideration the requirements for both compressive strength and shrinkage,it is recommended that in practical applications,highly active magnesia be chosen with a content range of 3% to 6%.