矿物掺合料对道路水泥混凝土塑性开裂和抗冻耐久性影响的研究

Study on the Effect of Mineral Admixture on Plastic Cracking and Frost Resistance Durability of Road Cement Concrete

抗裂性和抗冻性是影响道路水泥混凝土性能的重要因素,为比较粉煤灰、硅灰、矿渣微粉等矿物掺合料对道路水泥混凝土塑性开裂和抗冻耐久性的影响,采用平板法、电通量法和慢冻法,测定了矿物掺合料混凝土的塑性开裂时间、条数、面积,氯离子扩散系数和相对动弹模量。结果表明,矿物掺合料可加速或延缓混凝土塑性裂缝的发生时间,掺量与平均开裂面积、单位面积上的开裂面积呈正相关,但与裂缝条数无显著相关性;矿物掺合料可有效降低混凝土的氯离子扩散系数,但掺量超过20%后,降低速率有所减缓;矿物掺合料改善混凝土抗冻耐久性的作用在冻融后期愈发明显。掺量适宜时,3种掺合料均可达到相似作用效果,过量后相对动弹模量均呈下降趋势,冻融后期的下降更加显著。

Crack resistance and frost resistance are important factors affecting the performance of road concrete. In order to compare the effects of mineral admixtures such as fly ash, silica fume and slag powder on the plastic cracking and frost resistance durability of cement concrete, the plastic cracking time, number and area of cracks, Cl^- diffusion coefficient and relative dynamic modulus of mineral admixture concrete was determined by the flat plate method, electric flux method and slow freezing method. The results show that: mineral admixture can accelerate or delay the occurrence time of plastic cracks in concrete. The amount of doping is positively correlated with the average cracking area and the cracking area per unit area, but there is no significant correlation with the number of cracks. Mineral admixtures can effectively reduce the Cl^- diffusion coefficient of concrete. However, after the dosage exceeds 20%, the rate of decrease is slowed down. The effect of mineral admixtures on improving the frost resistance durability of concrete has become more apparent in the late stage of freezing and thawing. When the dosage is appropriate, the three admixtures can achieve similar effects. After the excess, the relative dynamic elastic modulus shows a downward trend, and the decline in the late freeze-thaw period is more significant.