内养护对自密实混凝土收缩及渗透性的影响
发布时间：2019-03-13 13:34
【摘要】：因具有无需振捣而密实成型的技术优势,自密实混凝土(SCC)在建筑业中的工程应用获得显著增长。与普通混凝土相比,SCC通常含有较高的细骨料含量、浆体体积和高效减水剂掺量。因此,SCC会产生比普通混凝土更高的收缩值,从而具有较高的开裂敏感性。内养护的应用可有效降低混凝土的自收缩。多孔内养护材料的存在将会改变SCC的流变性、力学性能和耐久性等方面的性能。本文使用轻质砂(LWS)和高吸水性树脂(SAP)作为内养护材料。实验中使用的轻骨料为吸水率、粒型及力学性质等属性均不相同两种轻质砂(LWS A和B),SAP则为吸水性相近的三种不同粒径的聚丙烯酸类树脂。主要研究内养护材料对SCC的流变性、抗压强度、自收缩、干燥收缩、吸水率、抗碳化和抗氯离子渗透性能等性能的影响。研究结果表明新拌砂浆中内养护剂的吸水和释水特性及其掺量对砂浆流变性的影响均取决于混合物中自由水的可用性;内养护剂掺量和额外水的增加,使砂浆中可用的自由水含量明显提高,从而达到保持砂浆工作性的目的。SAP的粒径将会影响其在砂浆中的吸水和释水动力特性;当内养护水含量相同时,粒径较大的SAP,开始吸水缓慢,随后将在整个实验的过程中持续吸水,从而导致砂浆塑性黏度的明显增加。与水泥浆基体及其与骨料之间的界面过渡区(ITZ)相比,替代天然河砂的饱水轻骨料是SCC中最薄弱的部分,其体积掺量和属性决定了SCC的抗压强度。当水泥基体水化程度提高的增强效果能够弥补SAP孔的减弱效果时,掺入饱水SAP的SCC抗压强度可与控制组保持相近;SCC的抗压强度随着吸水SAP粒径的增大而有所减小。饱水轻质砂的引入降低了SCC早期自收缩,且取代量的增加对SCC早期自收缩改善效果明显;轻骨料A对SCC早期自收缩的改善效果好于轻骨料B;预浸轻骨料的引入对SCC干燥收缩的改善均无明显效果。随着SAP掺量和内养护水引入量的提高,SCC早期自收缩逐渐降低;粒径为75-125μm的SAP的掺入对SCC的早期自收缩及干燥收缩降低效果最明显。内养护材料和额外水的引入提高了水泥基体的水化程度,使混凝土的密实性增加;另一方面,SCC的总孔隙率增加,使得混凝土的抗渗透性下降。
[Abstract]:The engineering application of self-compacting concrete (SCC) in construction industry has been greatly increased due to its technical advantage of compacting without vibration. Compared with ordinary concrete, SCC usually contains higher fine aggregate content, slurry volume and superplasticizer content. Therefore, SCC can produce higher shrinkage value than ordinary concrete, so it has higher cracking sensitivity. The application of internal curing can effectively reduce the autogenous shrinkage of concrete. The existence of porous internal curing materials will change the rheological properties, mechanical properties and durability of SCC. In this paper, light sand (LWS) and super absorbent resin (SAP) were used as internal curing materials. The light aggregate used in the experiment is water absorption, particle shape and mechanical properties are different. Two kinds of light sand, (LWS A and B), SAP, are three kinds of polyacrylic acid resins with similar water absorption. The effects of internal curing materials on the rheological properties, compressive strength, autogenous shrinkage, drying shrinkage, water absorption, carbonation resistance and chloride permeation resistance of SCC were studied. The results show that the characteristics of water absorption and release of the internal curing agent in fresh mortar and the influence of the amount of admixture on the rheological property of mortar depend on the availability of free water in the mixture. The content of free water in mortar increases obviously with the increase of the content of internal curing agent and extra water, so as to maintain the workability of mortar. The particle size of SAP will affect the dynamic characteristics of water absorption and water release in mortar. When the internal curing water content is the same, the larger particle size of SAP, begins to absorb water slowly, and then will continue to absorb water during the whole experiment process, which leads to the obvious increase of mortar plastic viscosity. Compared with (ITZ), the saturated lightweight aggregate, which replaces natural river sand, is the weakest part of SCC, and its volume content and properties determine the compressive strength of SCC. The compressive strength of SCC mixed with saturated SAP was similar to that of the control group, and the compressive strength of SCC decreased with the increase of the size of absorbent SAP when the hydration degree of the cement matrix was increased to make up for the weakening effect of SAP hole. The introduction of saturated light sand reduced the early self-shrinkage of SCC, and the improvement of early self-shrinkage of SCC was obvious with the increase of substitution amount, and the improvement effect of lightweight aggregate A on the early self-shrinkage of SCC was better than that of light aggregate B, and that of light aggregate A was better than that of light weight aggregate B. The introduction of pre-impregnated lightweight aggregate has no obvious effect on the drying shrinkage of SCC. The early autogenous shrinkage of SCC gradually decreased with the increase of SAP content and the amount of water in internal curing, and the effect of 75-125 渭 m SAP incorporation on the early self-shrinkage and drying shrinkage of SCC was the most obvious. With the introduction of internal curing materials and extra water, the hydration degree of cement matrix is improved and the density of concrete is increased, on the other hand, the total porosity of SCC increases and the anti-permeability of concrete decreases.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528
本文编号：2439430
[Abstract]:The engineering application of self-compacting concrete (SCC) in construction industry has been greatly increased due to its technical advantage of compacting without vibration. Compared with ordinary concrete, SCC usually contains higher fine aggregate content, slurry volume and superplasticizer content. Therefore, SCC can produce higher shrinkage value than ordinary concrete, so it has higher cracking sensitivity. The application of internal curing can effectively reduce the autogenous shrinkage of concrete. The existence of porous internal curing materials will change the rheological properties, mechanical properties and durability of SCC. In this paper, light sand (LWS) and super absorbent resin (SAP) were used as internal curing materials. The light aggregate used in the experiment is water absorption, particle shape and mechanical properties are different. Two kinds of light sand, (LWS A and B), SAP, are three kinds of polyacrylic acid resins with similar water absorption. The effects of internal curing materials on the rheological properties, compressive strength, autogenous shrinkage, drying shrinkage, water absorption, carbonation resistance and chloride permeation resistance of SCC were studied. The results show that the characteristics of water absorption and release of the internal curing agent in fresh mortar and the influence of the amount of admixture on the rheological property of mortar depend on the availability of free water in the mixture. The content of free water in mortar increases obviously with the increase of the content of internal curing agent and extra water, so as to maintain the workability of mortar. The particle size of SAP will affect the dynamic characteristics of water absorption and water release in mortar. When the internal curing water content is the same, the larger particle size of SAP, begins to absorb water slowly, and then will continue to absorb water during the whole experiment process, which leads to the obvious increase of mortar plastic viscosity. Compared with (ITZ), the saturated lightweight aggregate, which replaces natural river sand, is the weakest part of SCC, and its volume content and properties determine the compressive strength of SCC. The compressive strength of SCC mixed with saturated SAP was similar to that of the control group, and the compressive strength of SCC decreased with the increase of the size of absorbent SAP when the hydration degree of the cement matrix was increased to make up for the weakening effect of SAP hole. The introduction of saturated light sand reduced the early self-shrinkage of SCC, and the improvement of early self-shrinkage of SCC was obvious with the increase of substitution amount, and the improvement effect of lightweight aggregate A on the early self-shrinkage of SCC was better than that of light aggregate B, and that of light aggregate A was better than that of light weight aggregate B. The introduction of pre-impregnated lightweight aggregate has no obvious effect on the drying shrinkage of SCC. The early autogenous shrinkage of SCC gradually decreased with the increase of SAP content and the amount of water in internal curing, and the effect of 75-125 渭 m SAP incorporation on the early self-shrinkage and drying shrinkage of SCC was the most obvious. With the introduction of internal curing materials and extra water, the hydration degree of cement matrix is improved and the density of concrete is increased, on the other hand, the total porosity of SCC increases and the anti-permeability of concrete decreases.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528
【参考文献】
相关期刊论文 前3条
1 孔祥明;张珍林;;高吸水性树脂对高强混凝土浆体孔结构的影响[J];硅酸盐学报;2013年11期
2 黄政宇;王嘉;;高吸水性树脂对超高性能混凝土性能的影响[J];硅酸盐通报;2012年03期
3 Farhad ASLANI;Shami NEJADI;;Shrinkage behavior of self-compacting concrete[J];Journal of Zhejiang University-Science A(Applied Physics & Engineering);2012年06期
，本文编号：2439430
本文链接：https://www.wllwen.com/jingjilunwen/jianzhujingjilunwen/2439430.html
