用电阻率法研究新拌混凝土的早期凝结和硬化

测定和分析了新拌混凝土早期水化期间电阻率发展的特性。根据电阻率曲线和其微分曲线上的特征点将混凝土的水化分为：溶解期、凝结期、硬化前期和硬化的减速期。提出从电阻率发展微分曲线第1峰值特征点查找混凝土终凝时间和推算初凝时间的方法。结果表明：电阻率法得到的初凝时间和终凝时间与贯入阻力法测试得到的凝结时间有良好的相关性。比较了纯水泥混凝土和掺粉煤灰混凝土的电阻率发展特性和强度特性。结果显示：掺粉煤灰混凝土的早期强度随粉煤灰掺量的增加呈下降趋势，同龄期样品的电阻率也有相同的下降趋势。

EARLY SETTING AND HARDENING PROCESS OF YOUNG CONCRETE USING THE RESISTIVITY MEASUREMENT

The process of hydrating young concrete was studied based on the critical points of electrical resistivity and its differential curves.The electrical resistivity curve was identified to divide the hydration process into four periods: dissolution,setting,initial hardening,and hardening deceleration.A method to obtain concrete setting time based on electrical resistivity results was introduced. The results show that the electrical resistivity and penetration methods have strong correlation in determining setting time.The electrical resistivity and strength development between the control concrete and fly ash concrete were compared.The results show that the strength and bulk resistivity of concrete at an early age decrease with the increase of(amount) of fly ash replacement.