【作者】 王军；

【导师】 马保国；

【作者基本信息】 武汉理工大学 ， 建筑材料与工程， 2011， 博士

【摘要】 目前,在混凝土中引入相变材料实现对混凝土的温度控制,以避免温度变化对混凝土的破坏,已经成为了一个新的研究课题。相变材料具有蓄热特性,在温度升高至相变点时产生相变吸收热量,而当温度降低至相变点时亦可以相变放出热量,因此可用于抑制大体积混凝土的水化热温升速率,有效地控制混凝土内部的温度变化。论文在已有的研究成果的基础上,建立了相变控温混凝土的绝热温升模型,并提出了相变控温混凝土的基本理论。针对几种相变材料对水泥水化历程的控温作用进行了研究,并对其控温性能进行了评价。分别开发了一种P-水泥相变粗集料和一种R-P相变细集料,并研究分析了相变陶粒、P-水泥相变集料和R-PA对混凝土工作性能、力学性能和耐久性能的影响,并通过ANSYS软件,模拟计算了普通混凝土和相变控温混凝土的温度场和温度应力。主要创新性成果如下：1.根据水泥水化放热规律,分析了普通混凝土内部温度的变化,建立了相变控温混凝土的绝热温升模型,提出了相变控温混凝土的基本理论,并利用ANSYS软件,模拟计算了普通混凝土和相变控温混凝土的温度场和温度应力。(1)建立了相变控温混凝土的绝热温升模型,将温升过程分成三段,形成以下绝热温升模拟计算公式：(2)利用相变控温混凝土的绝热温升模型,通过ANSYS软件模拟计算得到,相变控温混凝土P-C10中心点的最高温度比普通混凝土P-C0中心点的最高温度约低3.8℃,且P-C10中心点温峰值比P-C0延迟3～4h。(3)普通混凝土和相变控温混凝土在计算模型的温度边界及约束边界条件下,最大温度梯度与最大温度应力均出现在模型长边方向上,P-C0的100号节点温度应力最大值比P-C10同节点约大2.2MPa(拉应力)；P-C0的172号节点温度应力最小值比P-C10同节点约小1.1MPa(压应力)。2.开发设计了一种混凝土水化温升测试仪,研究了一级相变材料、二级相变材料和矿物掺合料对水泥混凝土水化温升的控温效果,论证了利用相变材料作为控温材料的可行性。(1)设计的混凝土水化温升测试仪与传统绝热温升仪相比具有更好的可操作性,可进行多通道同步测试,增加了试验的可对比性。(2)在一级相变控温体系G-C体系、Y-C体系、Z-C体系、Pa-C体系和Pb-C体系中,10%掺量下削峰效应和延迟效应最好的是Pb-C体系,降温幅度为28.5%,最高温度到达时间tmax延缓9.8h;削峰效应最差的是Z-C体系,降温幅度为1.8%；石蜡类相变材料与有机酸类相变材料相比具有较好的削峰效应和延迟效应。(3)在二级相变控温体系中,以Pb为高温相变材料,当Pa作为低温相变材料时,其削峰作用最优；当有机酸作为低温相变材料时,相变点越低,体系的削峰作用越好；Pa2-Pb8、Y2-Pb8和G2-Pb8体系的降温幅度分别为18.2%、10%和14%。3.分别制备了相变陶粒和开发了一种P-水泥相变集料作为混凝土粗集料,研究了相变粗集料对水泥混凝土的控温能力；将相变粗集料取代部分粗集料配制相变控温混凝土并进行热循环养护,研究了相变控温混凝土的物理力学性能和耐久性能。(1)采用真空吸附法制备了三种相变陶粒,其粒径在5～20mm范围内,吸附率分别为9.9%、17.9%和31.3%；根据球-壳结构模型,采用定量常温包覆法制备了P-水泥相变集料,粒径在5～10mm范围内,包覆率达到30%以上。制备的相变粗集料均对水泥水化具有较好的削峰和延迟效应,且单位体积的P-水泥相变集料削峰和延迟效应优于相变陶粒。(2)相变控温混凝土中P净掺量为胶凝材料质量的10%时,相变陶粒混凝土抗压强度较普通混凝土低,P-水泥相变集料混凝土抗压强度与普通混凝土相当；经过热循环后,相变控温混凝土抗碳化和抗氯离子渗透性能提高,P-水泥相变集料混凝土的体积稳定性优于普通混凝土。4.利用R的多孔性,开发了一种R封装P的技术,通过表面改性技术制备了一种细集料R-PA,提高了其与混凝土的工作适应性,研究了R-PA对水泥水化温升和水化进程的影响,以及R-PA对混凝土的力学性能和耐久性能的影响。(1)利用工业R和P制备了R-PC,并采用石灰石粉对其进行表面改性制备了R-PA。R-PA中P的质量比为35%左右。R-PA在混凝土中分布比较均匀,相变控温混凝土的和易性较好。(2)R-PC可使水泥浆体的类抛物线形温升曲线开口变大,有明显的削峰和延迟效应,有效地控制了水泥水化的温升速率。(3)从R-PA相变控温混凝土的强度规律来看,R-PA的掺量在P净掺量为胶凝材料质量的10%时是可行的。R-PA对混凝土的强度带来一定的损失,且相变控温混凝土中P的净掺量为胶凝材料质量的20%时的强度较P净掺量为10%时低；在标准养护和热循环下,R-PA相变控温混凝土的强度波动不明显,具有较强的可设计性。(4)R-PA明显地减小了混凝土因温升和温降时所产生的体积变化,提高了混凝土抗渗性,尤其在经过高温养护后,R-PA混凝土的抗渗性大幅提高。更多还原

【Abstract】 At present, it’s become a new research that phase change materials (PCMs) were put in concrete to control temperature in order to avoid the concrete destruction of temperature changes. PCM has regenerative property, when environment temperature increased to phase transition point, heat can be absorbed by PCM and when the environment temperature decreased below phase transition temperature, heat can be released by the PCM, so the PCM can be used controlling temperature rise rate of hydration in mass concrete in order to avoid temperature damage in concrete.Base on the research of predecessors, a model of controlling the adiabatic temperature rise of concrete was established in this study, and the basic theory of phase change temperature self-control concrete was proposed. Temperature control effect of several phase change on cement hydration process was studied, and the temperature control performance was evaluated.P-C phase change aggregate and R-P phase change aggregate were developed and the influences of ceramiste aggregate, P-C phase change aggregate and R-P phase change aggregate on workability, mechanical performances and durability of concrete were researched. The temperature field and thermal stress were calculated by ANSYS.Through research, the following results were achieved:1. According to law of cement hydration, ordinary concrete internal temperature changes was analyzed, adiabatic temperature rise model of phase change concrete was established, new ideas to control the temperature with phase change materials was proposed in this paper. The temperature field and thermal stress were calculated by ANSYS.(1) Adiabatic temperature rise model of phase change concrete was established, temperature rising process was divided into three segments, and the simulation calculation formula of adiabatic temperature rise model was as follows: (2) According to adiabatic temperature rise model of phase change concrete, it’s calculated by ANSYS that the highest center temperature of the phase change concrete was lower 3.8℃than the highest center temperature of the ordinary concrete, and the peak of the center temperature of phase change concrete was delayed 3-4 hours than the basic concrete.(3) In the temperature boundary and constraints boundary condition of the model, the maximum thermal gradient and maximum thermal stress of ordinary concrete and phase change concrete appeared in the long side direction of the model. The maximum stress of the 100th node of the basic concrete was 2.2MPa larger (tensile stress) than the stress of the same node of the phase change concrete, the minimum stress of the 172nd node of the basic concrete was 1.1MPa less (pressure stress) than the stress of the same node of the phase change concrete.2. Concrete Hydration Temperature Tester was designed. Single-phase change system, dual-phase change system and mineral admixtures were used in temperature control technology of hydration temperature concrete. The feasibility of using PCMs as temperature control materials was demonstrated.(1) Concrete hydration temperature tester, which provides a better test method for traditional one, has better maneuverability compareing with adiabatic temperature rise of concrete.(2) Paraffin b-PCMs had the best cutting-peak and delaying-peak effect in Single-phase change system including G-C system, Y-C system, Z-C system, Pa-C system and Pb-C system, cutting-peak temperature range was 28.5%, tmax was 9.8h. Z-C had the worst cutting-peak and delaying-peak effect, cutting-peak temperature range was 1.8%. Paraffin-PCMs had a better cutting-peak and delaying-peak effect than organic acid-PCMs. (3) When Pb was used as high temperature PCM in dual-phase change system, Pa had better cutting-peak effect than organic acid as low temperature PCM, the lower transformation temperature of onganic acid-PCM was, the better the cutting-peak effect was. The cutting-peak temperature range of Pa2-Pb8, Y2-Pb8 and G2-Pb8 was 18.2%,10% and 14%.3. Phase change ceramisite and P-cement phase change aggregate were prepared as Concrete coarse aggregate. Tempareture control capaility of phase change coarse aggregate were studied, the influences of phase change ceramisite on mechanical propertities and durabilities of concrete were analysized under standard curing and thermal cycling conditions.(1) Three kinds of ceramisite were selected to prepare phase change ceramisite with content of 9.9%、17.9% and 31.3% using vacuum absorption, the size of ceramisite was in 5～20mm range. P-cement phase change aggregate with content of 30% was prepared by simulating the ball shell structure, the size of aggregate was in 5～10 mm range. There was certain of peak cutting and delaying effect of phase change coarse aggregate on hydration temperature rise of cement, and effect of P-cement phase change aggregate was better than phase change ceramisite.(2) When the ratio of P was 10% in phase change, the compressive strength of phase change ceramisite was lower than ordinary concrete, and the compressive strength of P-cement phase change aggregate was roughly the same. Under high temperature cycling condition, the carbonation resistance and the chloride penetration resistance of phase change concrete increased, volume stability of P-cement phase change aggregate was better than ordinary concrete.4. Utilizing industrial rice husk ash, via the Composites Preparation Technology and Surface Modification Technology prepared phase change fine aggregates of R-PA, the technology of P capsulation by hush ash was developed. The workability between R-PA and concrete was enhanced. The influences of phase change ceramisite on mechanical propertities and durabilities of concrete are analysized under standard curing and thermal cycling conditions.(1) R-PC was prepared by industrial rice husk ash and P, and the limestone powder wrapped up on it to prepare R-PA. The ratio of P in R-PA was about 35%. R-PC bonded tightly, the workability of cement paste and fresh concrete was well good.(2) R-PA could make the temperature rise curve of cement pastes larger openings, and had significant effect of cooling clipping, effectively controlled the temperature rise rate of hydration of cement pastes. (3) Considering compressive strength of concrete, it’s reasonable that ratio of P in gelled material was 10%. R-PA resulting in the loss of concrete strength to some extent, and the strength of phase concrete was lower when the relatively net content of paraffin was 20% of the binding materials mass than 10%. In standard curing conditions and high temperature curing conditions, the 28d strength of phase change concrete is good stability.(4) R-PA significantly reduced the changes of concrete volume generated due to temperature rise and drop, improved the impermeability of concrete remarkably, especially, he impermeability is perfectly good in high temperature curing condition.更多还原