集料的石膏含量对混凝土性能的影响

Effect of the Content of Gypsum in Aggregates on the Performance of Concretes

研究了集料中石膏碎石和石膏砂的含量对混凝土膨胀率、抗压强度和超声脉冲速率的影响,分析了掺石膏集料混凝土的微观结构。研究结果表明,石膏碎石替代部分粗集料时,石膏碎石引入的SO_3含量小于等于集料总量的1.5%时混凝土的变形、抗压强度和超声脉冲速率未受到显著影响,当石膏碎石引入的SO_3含量大于等于集料总量的3%时混凝土150 d时的抗压强度明显降低。石膏砂代替细集料时石膏砂引入的SO_3含量大于等于1.5%时混凝土会发生较大的膨胀,抗压强度显著降低。靠近石膏的浆体内产生大量钙矾石使得浆体发生开裂,并使得石膏集料与浆体脱开。

The effect of the content of gypsum-bearing crushed rocks and sands in aggregates on the deformation,compressive strength, speed of ultrasonic wave of concretes were investigated. The microstructures of the concretes were examined with SEM. It was found that gypsum used as coarse aggregate has little effect on deformation,compressive strength and speed of ultrasonic wave of concretes when the SO3 content of aggregates derived from crushed gypsum is less than 1. 5% by weight. Significant loss of strength would occur if the SO3 content of aggregates supplied by crushed gypsum exceeds 3% by weight. When SO3 content of the aggregates derived from sandy gypsum is more than 1. 5%,concretes expand. As a result,the strength of concretes decrease significantly after 150 d. Massive ettringite crystals formed near gypsum particles cause the cement pastes to expand or even crack.