粉煤灰对LC15全轻混凝土性能及浆体流变性影响研究

Effects of Fly Ash on Properties of LC15 Lightweight Concrete and Rheological Properties of the Pastes

研究了不同粉煤灰掺量(10%～40%)对LC15级全轻混凝土工作性、干表观密度、抗压强度及其浆体流变性能的影响。试验结果表明:粉煤灰可有效提高轻骨料混凝土的工作性,但在低掺量时易引起轻骨料混凝土黏聚性及扩展度的下降;掺入粉煤灰可显著降低轻骨料混凝土的干表观密度,当掺量超过10%时会降低其28 d抗压强度,但在20%掺量条件下,56 d抗压强度保持与基准组相当;掺入粉煤灰使轻骨料混凝土浆体屈服应力及塑性黏度下降,其中,塑性黏度下降可能是造成轻骨料混凝土黏聚性下降的原因之一。

The workability, drying apparent density, compressive strength and paste rheological properties of LC15 lightweight concrete incorporating 10% ~40% fly ash are investigated. The results shows that the addition of fly ash can effectively improve the workability of lightweight concrete, however, the cohesiveness and slump flow of lightweight concrete may decrease at a lower fly ash content. In addition, the drying apparent density of the lightweight concrete decreases becasuse of the addition of fly ash. When the dosage of fly ash exceeds 10%, its 28 d compressive strength decreases, but the 56 d compressive strength of sample with 20% fly ash is comparable to that of the reference group.Moreover, the addition of fly ash decreases the yield stress of pastes in lightweight concrete and the decreasing plastic viscosity may be responsible for the decreasing cohesiveness of lightweight concrete.