硫铝酸盐水泥混凝土早期收缩及调控研究

发布时间：2018-05-03 12:47

本文选题：硫铝酸盐水泥混凝土 + 收缩　；参考：《清华大学》2015年硕士论文

【摘要】：硫铝酸盐水泥混凝土作为高早强、低能耗、低碳排放、耐腐蚀的新型混凝土,与普通混凝土一样,存在早期收缩引发开裂的问题。本文以硫铝酸盐水泥混凝土为研究对象,旨在研究其早期收缩与内部湿度发展规律,深入探索降低硫铝酸盐水泥混凝土早期收缩并提高其抗裂性的具体办法。研究首先设计了低、中、高强三个系列硫铝酸盐水泥混凝土的配合比,测定了各类混凝土典型龄期的抗压强度与弹性模量等基本力学性能。然后,基于等温量热试验,确定了各系列硫铝酸盐水泥混凝土的最终水化度,并根据绝热温升试验确定了各类硫铝酸盐水泥混凝土水化度随龄期的发展规律。在上述研究基础上,通过试验测定了密封和干燥条件下三个系列硫铝酸盐水泥混凝土的收缩以及内部相对湿度随着时间的变化。硫铝酸盐水泥混凝土收缩发展呈两阶段模式,即先期的收缩快速增长阶段与随后的缓慢发展阶段,在收缩快速增长阶段,硫铝酸盐水泥混凝土可以在2小时内达到硅酸盐水泥混凝土2天的收缩值。而在收缩缓慢发展阶段,硫铝酸盐水泥混凝土收缩增长速率明显低于硅酸盐水泥混凝土,使用硫铝酸盐水泥可以显著降低混凝土的干燥收缩。针对硫铝酸盐水泥混凝土早期收缩,研究了预吸水轻骨料对其的调控作用。研究中测定了内养护及普通低、中、高强硫铝酸盐水泥混凝土密封和干燥条件下早期收缩和内部相对湿度的发展。预吸水轻骨料内养护可以减小硫铝酸盐水泥混凝土的自收缩,强度越高,降低效果越明显;同时,内养护无法减小表面干燥引发的收缩。由混凝土板的湿度场试验研究发现,预吸水轻骨料内养护能够延长硫铝酸盐水泥混凝土的湿度饱和期,强度越高,延长效果越明显;同时,内养护能提升硫铝酸盐水泥混凝土的整体湿度水平。基于钢环约束试验,对普通和内养护的低强、中强、高强硫铝酸盐水泥混凝土的抗裂性进行验证,试验结果表明高强硫铝酸盐水泥混凝土相对于高强硅酸盐水泥混凝土具有更好的抗裂性。内养护可以有效地提高硫铝酸盐水泥混凝土的早期抗裂性。最后在试验研究基础上,建立了适用于硫铝酸盐水泥混凝土早期收缩预测的两阶段模型和考虑了水泥水化耗水、水分扩散、初始水分分布的湿度场计算模型。上述模型可以较好地模拟不同强度等级内养护与普通硫铝酸盐水泥混凝土早期收缩和内部湿度的发展规律。
[Abstract]:As a new type of concrete with high early strength, low energy consumption, low carbon emission and corrosion resistance, sulphoaluminate cement concrete, like ordinary concrete, has the problem of cracking caused by early shrinkage. This paper takes sulphoaluminate cement concrete as the research object, aims to study its early shrinkage and the development law of internal humidity, and to explore the concrete method to reduce the early shrinkage and improve the crack resistance of sulphoaluminate cement concrete. In this paper, the mixture ratio of three series of sulphoaluminate cement concrete of low, medium and high strength is designed firstly, and the basic mechanical properties such as compressive strength and elastic modulus of concrete of typical age are measured. Then, based on the isothermal calorimetry test, the final hydration degree of each series of sulphoaluminate cement concrete is determined, and the development law of hydration degree with age of various sulphoaluminate cement concrete is determined according to the adiabatic temperature rise test. On the basis of the above research, the shrinkage of three series sulphoaluminate cement concrete under sealed and dry conditions and the change of internal relative humidity with time were measured. The shrinkage development of sulphoaluminate cement concrete shows a two-stage pattern, that is, the rapid growth stage of shrinkage and the stage of slow development later, in the stage of rapid growth of shrinkage, Sulphoaluminate cement concrete can reach the shrinkage value of Portland cement concrete in 2 hours. At the stage of slow development of shrinkage, the shrinkage growth rate of sulphoaluminate cement concrete is obviously lower than that of Portland cement concrete, and the drying shrinkage of concrete can be significantly reduced by using sulphoaluminate cement. Aiming at the early shrinkage of sulphoaluminate cement concrete, the effect of pre-absorbent lightweight aggregate on it is studied. The development of early shrinkage and internal relative humidity of low, medium and high strength sulphoaluminate cement concrete under sealing and drying conditions were measured. The internal curing of pre-absorbent lightweight aggregate can reduce the self-shrinkage of sulphoaluminate cement concrete, and the higher the strength, the more obvious the reduction effect is, meanwhile, the internal curing can not reduce the shrinkage caused by surface drying. Based on the humidity field test of concrete slabs, it is found that the moisture saturation period of sulphoaluminate cement concrete can be prolonged by curing in pre-absorbent lightweight aggregate, and the higher the strength, the more obvious the prolongation effect is. Internal curing can improve the overall humidity level of sulphoaluminate cement concrete. Based on the confined test of steel ring, the crack resistance of ordinary and internal curing low, medium and high strength sulphoaluminate cement concrete is verified. The test results show that high strength sulphoaluminate cement concrete has better crack resistance than high strength Portland cement concrete. Internal curing can effectively improve the early crack resistance of sulphoaluminate cement concrete. Finally, based on the experimental study, a two-stage model suitable for early shrinkage prediction of sulphoaluminate cement concrete and a moisture field calculation model considering cement hydration water consumption, water diffusion and initial moisture distribution are established. The above model can well simulate the development of curing in different strength grades and the early shrinkage and internal humidity of ordinary sulphoaluminate cement concrete.
【学位授予单位】：清华大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528

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