机制砂中细粉MB值对混凝土性能影响规律的研究

Study on the Influence Law of MB Value of Microfines in Manufactured Sand on Concrete Performances

机制砂中的细粉含量和亚甲蓝(MB)值显著影响混凝土的性能.将机制砂中细粉含量固定为10%,研究了细粉MB值在1.3~20 g/kg范围变化对C30和C60机制砂混凝土工作性、抗压强度、抗氯离子渗透性、抗冻性和干缩性能的影响规律,并通过XRD和TG-DSC测试了掺不同MB值细粉的水泥的水化产物.结果表明:细粉MB值的增大,提高了配制等坍落度混凝土所需的用水量(W/C变化)或减水剂掺量(W/C不变).W/C变化时,细粉MB值的增大显著劣化了混凝土的各项性能;W/C不变时,细粉MB值的增大同样会降低抗冻性、增大干缩,在MB值超过10,7 g/kg后降低C30、C60混凝土的抗压强度和抗氯离子渗透性,石粉MB值对C60混凝土性能的影响程度高于C30混凝土.MB值超过7 g/kg的细粉对水泥水化有阻碍作用而减少水化产物量.

Fine powder content and methylene blue(MB)value in machine-made sand significantly affect the performance of concrete.The content of fine powder in machine-made sand was fixed at 10%,and the influence of MB value of fine powder in the range of 1.3~20 g/kg on workability,compressive strength,chloride ion permeability resistance,frost resistance and drying shrinkage of C30 and C60 machine-made sand concrete was studied.The hydration products of cement mixed with fine powders with different MB values were tested by XRD and TG-DSC.The results show that with the increase of MB value of fine powder,the amount of water(W/C change)or the amount of water reducer(W/C unchanged)needed to prepare equal slump concrete is increased.When W/C changes,the increase of MB value of fine powder significantly deteriorates the properties of concrete.When W/C is constant,the increase of MB value of fine powder will also reduce frost resistance and increase dry shrinkage.When MB value exceeds 10,7g/kg,the compressive strength and chloride ion permeability resistance of C30 and C60 concrete will be reduced,and the MB value of stone powder has a greater influence on the performance of C60 concrete than that of C30 concrete.Fine powder with MB value exceeding 7 g/kg can hinder cement hydration and reduce the amount of hydration products.