【作者】 曾晓辉；

【导师】 隋同波；

【作者基本信息】 中国建筑材料科学研究总院 ， 材料学， 2007， 硕士

【摘要】 早龄期水泥混凝土研究有特别的意义,但其多变性和复杂性让研究者感到棘手,因此新的研究方法不断的被开发。无电极电阻率仪法（简称电阻率法）是近年来开发的一种方法,具有无损检测法的优点,可从物理、化学等角度观察、研究早龄期水泥混凝土的性能变化,有很好的前景。在本论文中,首先用电阻率法研究了水泥的水化,并阐述了水泥水化电阻率-时间曲线的意义,然后在水泥水化研究的基础上,用电阻率法测定水泥的凝结时间、快速检验水泥的强度以及研究减水剂与水泥的作用。研究表明水泥水化电阻率-时间曲线很好地描述了水泥的水化进程,根据电阻率-时间曲线和电阻率-时间微分曲线的变化规律,可将水泥水化划分为溶解期、诱导期、加速期和减速期四个阶段。XRD、DSC/TG等方法被用来分析水化不同龄期样品的物相组成、Ca（OH）₂含量,结果表明诱导期后浆体电阻率与水泥的Ca（OH）₂含量呈线性关系,电阻率变化反映了水化程度变化;诱导期的开始伴随着电阻率的突然上升和Ca²⁺浓度的突然减少,样品的DSC/TG分析表明存在某种水化物在411℃吸热失重,该水化物包裹可能导致了诱导期的出现;电阻率-时间微分曲线在加速中期的峰与AFt转化为AFm有关;研究还发现水化电阻率时间-微分曲线与放热曲线有很好的对应性。可以用电阻率最小值ρmin和电阻率最小值对应时间Tmin测定硅酸盐水泥的凝结时间,电阻率法与维卡仪法测得的结果线性相关,相关性系数R²达0.9以上。测定了不同种类、不同级别水泥水化24小时电阻率ρ24h和28天强度R28d,结果表明二者线性相关,相关性系数R为0.85,电阻率法可用来预测水泥的强度,与现行标准方法相比,电阻率法具有简单、适应性好、自动化程度高、准确度高等优点。研究发现掺FDN减水剂浆体的初始电阻率-掺量曲线由典型的“L”型（Langmuir型）和“S”型曲线复合而成,“L”型曲线反映了颗粒对减水剂的Langmuir吸附,而“S”型反映了减水剂的溶解电离作用,初始流动度实验表明,掺FDN减水剂浆体良好的流动度是减水剂吸附和溶解综合作用的结果。而掺木钙减水剂浆体初始电阻率-掺量曲线的变化转折点对应掺量与其临界掺量表现出惊人的一致,电阻率法可以用来测定木钙减水剂的临界掺量。研究还发现当FDN掺量高于最大初始电阻率对应的掺量时,水化电阻率-时间曲线有了明显的变化,这可能因为当掺量高于最大初始电阻率对应掺量时,大量减水剂溶解于溶液中,对水化物Ca（OH）₂等的过饱和度、成核、结晶等产生影响。更多还原

【Abstract】 Behavior of early age hydration of cement and concrete research is of special significance, but its complexity make researchers feel arduous to do it well, so new methods are continually invented. Electrodless Cement and Concrete Resistivity Tests （abbr. CCR） is a new method invented in recent years, it has virtues of NDT （Non-Destructive Test）, and can observe and research the early age cement and concrete not only from a physical standpoint but also from a chemical standpoint. In this paper, firstly, CCR was used to research the cement hydration and the resistivity curve was expatiated; then with the results of the hydration research, setting time determination and cement strength prediction were conducted; finally, CCR was also used to research the interaction of cement and plasticizer.Results show that the resistivity curve can describe the hydration course well, based on the resistivity curve and derivate curve of resistivity, the hydration course of Portland cement can be divided into four periods, they are the dissolution period , induction period, accelerating period and decelerating period.XRD and DSC/TG and other methods were used to analysis the mineral composing and Ca（OH）₂ content. Results show that resistivity and content of Ca（OH）₂ have a linear relationship after entered into induction period, so the resistivity reflects the hydration degree. The peak of derivate curve of resistivity appearing in the accelerating period is caused by the transformation of AFt to AFm. Induction period begins with a sharp rise of resistivity and a sudden decrease of Ca²⁺ concentration, DSC/TG analysis indicated that some substances were absorbing heat and losing weight at temperature of 411℃, encapsulation effect of hydration products may caused the induction period. It is clear that the derivate curve of resistivity have a good relationship with the curve of hydration heat rate, for both of them belong to the rate category.Results also show thatρ_min, minimum of resistivity, and T_m in, time of minimum resistivity, can be used for testing cement setting time, and the setting time tested by CCR method have a relationship with the setting time tested by Vicat method, the pertinence coefficient is higher than 0.9. Various kinds and classes of cements’resistivity hydrated for 24 hours and their 28-day compressive strength were tested. Results show good linear relationship between 24-hour resistivity and 28-day compressive strength, and CCR method can thus be used for accelerated strength testing.When a naphthalene-based super-plasticizer FDN was used to research the interaction of plasticizer and cement, it is found that the curve of initial resistivity versus dosage was compounded by a“L”type curve and a“S”type curve, the“L”type curve reflects the adsorption effect and the“S”type curve reflects the dissolving and ionization effects. The fluidity experiments proved that the best fluidity of slurry with FDN were caused by both adsorption effect and dissolving effect. It is amazing that when the Calcium Lignin Sulfonate was used to be a plasticizer, the dosage of the largest initial resistivity is equal to dosage of the best fluidity. This result means that the resistivity method can be used to test the saturated dosage of Calcium Lignin Sulfonate. It is also found that when the dosage is larger than the dosage of the largest initial resistivity, the resistivity curve of hydration was fundamentally changed, it may because when the plasticizer dissolved in solution, it may affects the hydration products’solubility, nuclear formation and crystallization.更多还原