基于水灰比修正方法研究SAP内养护作用机理

发布时间：2018-06-07 12:21

本文选题：砂浆 + 高吸水树脂　；参考：《北京交通大学》2017年硕士论文

【摘要】：高吸水树脂(Super Absorbent Polymer,SAP)内养护是一种常用的混凝土材料内养护方法。现有研究认为SAP内养护能够改善混凝土材料的多方面性能,包括降低早期收缩、减少开裂、提高强度、增加流动度等。SAP通过在混凝土内部释放水分,提高浆体早期硬化过程和长期服役过程中的内部湿度,达到从内部养护混凝土的效果。然而,SAP不仅在混凝土养护阶段会释放养护水分,在拌和期间也会与浆体进行水分交换,这一过程会造成浆体水灰比的改变,混凝土收缩、强度、流动度等性能也随之发生变化。现有研究往往将水灰比变化的影响结果计入内养护的作用效果中,难以准确分析真实的内养护作用机理,导致现有研究评价SAP的内养护效果时出现大量分歧。本论文针对这一问题,基于水灰比的修正方法研究SAP的内养护真实的作用效果。通过流动度平衡试验精确测量出SAP在不同水灰比净浆中的吸水量,对不同SAP掺量下浆体的真实水灰比进行修正;通过材料强度、水分含量、自收缩、水化热试验,在排除SAP改变浆体水灰比作用的基础上,探讨真实的SAP内养护作用对不同水灰比砂浆力学性能、收缩性能、水化进程的影响机理。主要工作和结论如下:(1)进行了净浆流动度试验,准确测量了 SAP在不同水灰比浆体中的吸水量,分析了水灰比、掺加方式、SAP粒径对其在浆体中的真实吸水量的影响规律。结果表明:不论干掺还是预湿,SAP与浆体的水分交换在5min之内基本完成,且随着水灰比的增加,SAP的吸水率逐渐增大;干掺SAP的吸水率要大于预湿;小粒径SAP的吸水率高于大粒径SAP。(2)进行了四个水灰比砂浆的自收缩和含水率试验,分析了水灰比、SAP掺量和粒径对浆体自收缩和水分含量的影响规律。结果表明:SAP能有效减小不同水灰比砂浆的自收缩,在最佳掺量下的减缩效果都在80%以上;对于0.21和0.26水灰比的砂浆试件,SAP掺量越大减缩效果越好;对于0.31和0.36水灰比的砂浆试件,当SAP掺量超过0.2%时,继续提高SAP掺量减缩效果不再增加。SAP主要在3d内释放出水分,提高砂浆的水分含量,降低自收缩的发展速率。SAP掺量相同时,水灰比越低,自干燥越严重,所需的内养护水分也就越多,所以低水灰比的砂浆对内养护的需求和依赖更大。SAP粒径对自收缩和含水率的影响较小。(3)进行了四个水灰比砂浆的强度和水化热试验,分析了水灰比、SAP掺量和粒径对强度和水化进程的影响规律。结果表明:大部分情况下,掺入SAP会降低混凝土的力学性能,且SAP掺量越高,抗压、抗折强度降低越显著;但对于低水灰比的浆体,适量的SAP可能提高材料强度;在排除水灰比变化对水化进程的影响之后发现,SAP对水泥水化进程的影响较小;SAP掺量相同时,浆体的水灰比越低,SAP内养护对水化进程的促进作用越明显,对强度的降低程度也越小;大粒径SAP对水泥水化的促进作用略微优于小粒径SAP,因而大粒径SAP对强度的降低作用略小于小粒径SAP。
[Abstract]:The maintenance of high water absorbent resin (Super Absorbent Polymer, SAP) is a common curing method for concrete materials. Existing research holds that the internal curing of SAP can improve the properties of concrete materials, including reducing early shrinkage, reducing cracking, increasing strength, increasing flow degree and so on,.SAP can release water by releasing water in concrete and improve slurry. The internal humidity of the early hardening process and the long service process can achieve the effect of curing the concrete from the interior. However, SAP will not only release the moisture of the concrete during the concrete curing period, but also exchange the water with the slurry during the mixing period. This process will cause the change of the water cement ratio of the slurry, the shrinkage, strength, and the fluidity of concrete. The existing research often takes the effect of the change of water cement ratio into the effect of internal maintenance, and it is difficult to accurately analyze the true internal curing mechanism, which leads to a large number of differences when the existing research and evaluation of the internal curing effect of SAP. This paper studies the internal maintenance of SAP based on the modified method of water cement ratio. Through the flow balance test, the water absorption of SAP in different water cement ratio is accurately measured, and the real water cement ratio of the slurry under different SAP content is corrected. On the basis of the material strength, water content, autogenous shrinkage, hydration heat test, and the effect of removing the water cement ratio of the SAP to the slurry, the real SAP is discussed. The effect of curing on the mechanical properties, shrinkage properties and hydration process of different cement mortar with different water cement ratio is studied. The main work and conclusion are as follows: (1) the water absorption of SAP in different water cement slurry is measured accurately, and the effect of water cement ratio, additive formula and SAP particle size on the real water absorption in the slurry is analyzed. The results show that water exchange between SAP and slurry is basically completed within 5min, regardless of dry or pre wetting, and with the increase of water cement ratio, the water absorption of SAP increases gradually, and the water absorption of dry doped SAP is greater than that of pre wetting; the water absorption of SAP with small particle size is higher than that of large particle size SAP. (2), and the self shrinkage and moisture content of water cement mortar are tested. The effects of water cement ratio, SAP content and particle size on the autogenous shrinkage and water content of the slurry are analyzed. The results show that SAP can effectively reduce the self shrinkage of different water cement mortar, and the reduction effect is more than 80% under the best dosage; for the mortar specimens with 0.21 and 0.26 water cement ratio, the greater the SAP content is, the better the shrinkage effect is, and for 0.31 and 0.36 water ash. When the ratio of mortar is more than 0.2%, when the content of SAP is more than 0.2%, the decreasing effect of SAP content will no longer increase the water content of.SAP mainly in 3D, increase the moisture content of the mortar and reduce the development rate of the self shrinkage, the lower the.SAP content, the lower the water cement ratio, the more serious the moisture content in the internal curing, and the sand with low water cement ratio. The demand and dependence on the internal curing of the slurry is greater than the effect of the.SAP particle size on the autogenous shrinkage and water content. (3) the strength and hydration heat test of four cement mortar are carried out. The effects of water cement ratio, SAP content and particle size on the strength and hydration process are analyzed. The results show that the mechanical properties of concrete will be reduced by adding SAP in large part of the case. The higher the SAP content, the more significant the compression and flexural strength decrease; but for the slurry with low water cement ratio, a proper amount of SAP may improve the strength of the material. After removing the effect of the change of water cement ratio on the hydration process, the effect of SAP on the hydration process of cement is less; at the same time, the water cement ratio of the slurry is lower, and the process of curing in SAP is the process of hydration. The more obvious the promotion effect is, the smaller the degree of strength reduction is, the larger particle size SAP has a slightly better effect on cement hydration than the small particle size SAP, so the effect of the large particle size SAP on the strength is slightly less than the small size SAP..
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528

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