养护温度和粉煤灰对补偿收缩混凝土膨胀效能的影响

研究了养护温度和粉煤灰掺量对补偿收缩混凝土的膨胀效能和强度的影响。结果表明：20、40℃养护时混凝土的各龄期强度均匀增长;60℃养护能极大地促进早期强度增长,后期强度增长缓慢。粉煤灰在不同养护温度下对混凝土的早期强度发展都有抑制作用;长期高温养护后,粉煤灰活性逐渐显现,显著促进混凝土的强度增长,且粉煤灰掺量越大,混凝土强度增幅越大。硫铝酸钙–氧化钙类膨胀剂的膨胀效能发挥对温度非常敏感,养护温度越高,膨胀剂的水化速度越快,膨胀作用发挥越早;适量掺加粉煤灰有利于膨胀效能的发挥,掺量越大,膨胀随温度增长的增幅越大。大掺量粉煤灰补偿收缩混凝土的强度发展和限制膨胀率的温度敏感性均很高。

Effects of Curing Temperature and Fly Ash on the Expansion Efficiency of Shrinkage-Compensating Concrete

The restrained expansion rate and compressive strength of shrinkage-compensating concrete were determined to investigate the effects of curing temperature and fly ash dosage on the expansion efficiency.The results show that the compressive strengths of concrete at different ages develop evenly in curing at 20 ℃ and 40℃,and the substantial strength gain can be achieved at early ages and the rate of strength gain is quite slow at later ages in curing at 60 ℃.Although fly ash can be activated at a high temperature,the addition of fly ash still impede the strength development at different temperatures at early ages.However,fly ash can highly improve the strength and the strength gain grows with a greater amount of fly ash in a longer curing at high temperatures.Temperature has a significant impact on the expansion efficiency of HCSA expansive agent.The elevated temperature can accelerate the hydration of expansive agent and thus increase the expansion of concrete at early ages.A proper amount of fly ash can also improve the concrete expansion.The expansion gain of concrete due to the increase of temperature increases with increasing the amount of fly ash.The expansion and strength development of shrinkage-compensating concrete with a greater amount of fly ash can be affected by temperature.