低水胶比下粉煤灰砂浆的等强机理分析及预测

Analysis and Prediction of Equal Strength Mechanism of Fly Ash Mortar under Low Water-Binder Ratio

在低水胶比下研究砂浆抗压、抗折强度,探究粉煤灰替代率、水胶比对砂浆抗压、抗折强度的影响程度及规律,揭示等强机理,建立砂浆强度预测模型。结果表明:粉煤灰替代率高于50%时,水胶比的降低对其抗压、抗折强度的提升尤为明显。粉煤灰替代率在30%~70%、水胶比在0.32~0.24区间变化时,若要维持砂浆28d抗压强度一致(误差范围为10%以内),粉煤灰替代率每增加20%,水胶比应降低0.04。在三种低水胶比下,粉煤灰替代率高于50%时,若继续增加粉煤灰替代率将会导致砂浆抗折强度的明显下降。另外,根据响应面分析法拟合出砂浆强度、水胶比、粉煤灰替代率三者的关系模型,并得到砂浆28d龄期等抗压、抗折强度预测曲线。模型中砂浆抗压强度峰值在粉煤灰替代率为20%左右时出现。

Under the low water-binder ratio(W/B), compressive strength and flexural strength of mortar were studied. The influence degree of substitution level of fly ash and water-binder ratio on mortar compressive strength and flexural strength were explored. The mechanism of equivalent strength was revealed and prediction model of mortar strength was established. The results show that when substitution level of fly ash is higher than 50%, the decrease of water-binder ratio is particularly obvious on the improvement of compressive strength and flexural strength.When substitution level of fly ash is 30%-70% and water-binder ratio is between 0.32 and 0.24, in order to make the mortar 28 d compressive strength equal(the strength error range is 10%), the substitution level of fly ash is increased by 20% and water-binder ratio should be reduced by 0.04 correspondingly. Under the three low water-binder ratios, if substitution level of fly ash is higher than 50% and continues to increase, the flexural strength of the mortar will decrease significantly. In addition, according to the response surface analysis, the relational models of mortar strength, water-binder ratio and substitution level of fly ash were fitted, and the prediction curves of 28 d equal compressive and flexural strength of mortar were obtained. The peak of compressive strength of the mortar in the model appears when the substitution level of fly ash is about 20%.