高温作用下粉煤灰再生混凝土损伤演化规律与损伤特性

Damage evolution law and damage characteristics of fly ash recycled concrete under high temperature

以粉煤灰、氢氧化钠、矿渣、硅酸钠等为原料,对高温作用下粉煤灰再生混凝土损伤演化规律与损伤特性进行了研究。结果表明:在粉煤灰掺量相同时,随着温度的升高,试件残余抗压强度比逐渐降低。在自然冷却下,经455℃、655℃高温作用后,粉煤灰掺量在25%、15%混凝土的残余抗压强度有所增加,比常温下分别提高6.73%、32.68%。掺量为35%的混凝土,255℃时抗压强度低于常温。在掺量为45%、55%时,强度比掺量为0的明显小。在自然冷却下,残余抗压强度很明显要高于喷洒冷却下的强度,通过对自然冷却和喷淋冷却两种状态下的残余抗压强度进行检测,前者是后者的1.716倍。除常温和455℃外,普通混凝土峰值应力要大于相应粉煤灰混凝土峰值应力。在同一温度下,各种粉煤灰掺量混凝土的声速值及回弹值随粉煤灰掺量的增大逐渐变小。在喷淋冷却、自然冷却下,粉煤灰混凝土声速值及回弹值所受影响较小。

Using fly ash,sodium hydroxide,slag and sodium silicate as raw materials,the damage evolution law and damage characteristics of fly ash recycled concrete under high temperature are studied,and the results show that when the fly ash content is the same,the residual compressive strength ratio of the specimen gradually decreases with the increase of temperature.Under the natural cooling,after the high temperature of 455 ℃ and 655 ℃,the residual compressive strength of fly ash content in 25% and 15% concrete increased,which was 6.73% and 32.68% higher than that at room temperature,respectively.The concrete with a content of 35% has a compressive strength lower than that at room temperature at 255 ℃.When the dosage is 45% and 55%,the strength is significantly smaller than the 0 dosage.Under natural cooling,the residual compressive strength is generally higher than that under spray cooling,and the residual compressive strength under natural cooling is 1.716 times the maximum strength under spray cooling.In addition to room temperature and 455 ℃,the peak stress of ordinary concrete is greater than the peak stress of corresponding fly ash concrete.At the same temperature,the sound velocity value and rebound value of various fly ash content concrete gradually decrease with the increase of fly ash content.Under spray cooling and natural cooling,the sound velocity value and rebound value of fly ash concrete are less affected.