Transitional thermal creep of early age concrete
Transitional thermal creep of early age concrete
复制标题
DOI：
10.1061/(asce)0733-9399(1999)125:4(458
复制
发表时间：
1999-04-01
期刊：
影响因子：
--
通讯作者：
Hansen, PF
中科院分区：
文献类型：
--
作者：
Hauggaard, AB;Damkilde, L;Hansen, PF
硬化混凝土的徐变和温度/水效应之间的耦合是众所周知的。温度或含水量的水平和时间梯度都会影响蠕变性能。在早期混凝土中，由于水化作用而产生的内部干燥和热发展增加了这些耦合的效果。本文的目的是建立一个考虑过渡温度效应的混凝土徐变数学模型。该模型适用于早期混凝土和硬化混凝土。在模型中的材料性能的发展被假定为取决于水化过程和热激活的水的微观结构。热激活被假定为支配的阿克里乌斯原理，和激活能的粘度的水被发现适用于实验数据的分析。温度的变化会在微观结构中产生不平衡，称为微预应力，这会降低混凝土的刚度并增加徐变率。老化材料以增量方式建模，反映了水化过程，其中新的水泥凝胶层在无应力状态下固化并为材料增加刚度。早期和硬化混凝土的徐变无论是在不同的恒定温度水平或不同的温度历史的实验结果的分析说明了该模型。
Couplings between creep of hardened concrete and temperature/water effects are well-known. Both the level and the gradients in time of temperature or water content influence the creep properties. In early age concrete the internal drying and the heat development due to hydration increase the effect of these couplings. The purpose of this work is to set up a mathematical model for creep of concrete that includes the transitional thermal effect. The model governs both early age concrete and hardened concrete. The development of the material properties in the model is assumed to depend on the hydration process and the thermal activation of water in the microstructure. The thermal activation is assumed to be governed by the Arrhenius principle, and the activation energy of the viscosity of water is found applicable in the analysis of the experimental data. Changes in temperature create an imbalance in the microstructure termed the microprestresses, which reduce the stiffness of the concrete and increase the creep rate. The aging material is modeled in an incremental way reflecting the hydration process in which new layers of cement gel solidify in a stress free state and add stiffness to the material. Analysis of experimental results for creep of early age and hardened concrete either at different constant temperature levels or for varying temperature histories illustrate the model.