盐卤腐蚀环境中纳米SiO_2对混凝土性能的影响
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摘要
对冻融循环和干湿循环分别与盐卤溶液浸泡的共同作用下,纳米SiO_2(Nano-SiO_2,NS)改性混凝土的耐久性能进行了试验研究,并且通过XRD对各条件作用下的试样进行了物相分析。研究结果表明:随着NS掺量的增加,标准条件养护下的混凝土抗压强度、抗盐卤-冻融和抗盐卤-干湿循环性能均呈现先增大后减小的变化,NS掺量为2%时,混凝土56 d抗压强度提高了27%,盐卤-冻融循环300次与盐卤-干湿循环70次后,混凝土的抗压强度和质量较基准试样分别提高了17%、1. 6%和22%、5. 1%;氯离子渗透系数随NS掺量增加逐渐减小,NS掺量为2%时,混凝土的氯离子渗透系数较基准试样降低了55%,当NS掺量超过2%时,氯离子渗透系数变化不明显;掺入NS的试样,经盐卤-冻融循环与盐卤-干湿循环作用后,石膏和钙矾石以及其他的腐蚀产物含量较基准试样明显降低。综合以上,掺入NS能够提高混凝土耐久性能,且NS的合适掺量为2%。
The durability of nano-SiO_2( NS) modified concrete was studied under the combined action of freeze-thaw cycles and dry-wet cycles with bittern respectively,XRD was used to analyze the samples under various conditions. The results prove that: with the increase of NS content,the compressive strength,freeze-thaw and dry-wet cycles resistance performance of concrete under standard condition maintenance showed the change of first increasing and then decreasing; when the NS content is 2%,the56 d compressive strength of concrete increases by 27%,freeze-thaw cycles with bittern 300 times and dry-wet cycles with bittern 70 times,the compressive strength and the quality of concrete increased by17%,1. 6% and 22% and 5. 1% respectively compared with the benchmark sample. Chloride ion permeability coefficient decreaseswith the increase of NS content. When the NS content is 2%,the chloride ion permeability of concrete is 55% lower than that of the benchmark sample,the NS content exceeds 2%,the chloride ion permeability coefficient of variation is not obvious. The contents of gypsum,ettringite and other corrosion products were significantly lower than those of the benchmark sample after the freeze-thaw cycles and dry-wet cycles with bittern of the NS samples. Above all,adding NS can improve the durability of concrete,and the appropriate amount of NS is 2%.
The durability of nano-SiO_2( NS) modified concrete was studied under the combined action of freeze-thaw cycles and dry-wet cycles with bittern respectively,XRD was used to analyze the samples under various conditions. The results prove that: with the increase of NS content,the compressive strength,freeze-thaw and dry-wet cycles resistance performance of concrete under standard condition maintenance showed the change of first increasing and then decreasing; when the NS content is 2%,the56 d compressive strength of concrete increases by 27%,freeze-thaw cycles with bittern 300 times and dry-wet cycles with bittern 70 times,the compressive strength and the quality of concrete increased by17%,1. 6% and 22% and 5. 1% respectively compared with the benchmark sample. Chloride ion permeability coefficient decreaseswith the increase of NS content. When the NS content is 2%,the chloride ion permeability of concrete is 55% lower than that of the benchmark sample,the NS content exceeds 2%,the chloride ion permeability coefficient of variation is not obvious. The contents of gypsum,ettringite and other corrosion products were significantly lower than those of the benchmark sample after the freeze-thaw cycles and dry-wet cycles with bittern of the NS samples. Above all,adding NS can improve the durability of concrete,and the appropriate amount of NS is 2%.
引文
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[11] Quercia G,Spiesz P,Hüsken G,et al. SCC modification by use of amorphous nano-silica[J]. Cement and Concrete Composites,2014,45(1):69-81.
[12] Salemi N,Behfarnia K. Effect of nano-particles on durability of fiber-reinforced concrete pavement[J]. Construction&Building Materials,2013,48(11):934-941.
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[14] Tobón J I,PayáJ,Restrepo O J. Study of durability of portland cement mortars blended with silica nanoparticles[J]. Construction&Building Materials,2015,80:92-97.
[2]张立明,余红发,何忠茂.盐湖地区混凝土的氯离子扩散性[J].中南大学学报(自然科学版),2011,42(6):1752-1755.
[3] Dong R,Ma B,He X. Sulfate attack on concrete in an Inland salt lake environment[J]. Journal of China University of Geosciences,2006,17(4):342-348.
[4] Pasupathy K,Berndt M,Sanjayan J,et al. Durability of low calcium fly ash based geopolymer concrete culvert in a saline environment[J].Cement&Concrete Research,2017,100:297-310.
[5]洪雷,唐晓东.冻融循环及龄期对混凝土氯离子渗透性的影响[J].建筑材料学报,2011,14(2):254-256.
[6]陈剑毅,胡明玉,肖烨,等.复杂环境下矿物掺合料混凝土的耐久性研究[J].硅酸盐通报,2011,30(3):639-644.
[7]郑晓宁,刁波,孙洋,等.混合侵蚀与冻融循环作用下混凝土力学性能劣化机理研究[J].建筑结构学报,2010,31(2):111-116.
[8] Alkaysi M,El-Tawil S,Liu Z,et al. Effects of ssilica powder and cement type on durability of ultra-high performance concrete(UHPC)[C].International Interactive Symposium on Uhpc,2016.
[9]余红发,孙伟,王甲春,等.盐湖地区混凝土的长期腐蚀产物与腐蚀机理[J].硅酸盐学报,2003,31(5):434-440.
[10] Bashar S,Mohammed,Mohd S L,et al. Properties of nano-silica pervious concrete[J]. Case Studies in Construction Materials,2018,8:409-422.
[11] Quercia G,Spiesz P,Hüsken G,et al. SCC modification by use of amorphous nano-silica[J]. Cement and Concrete Composites,2014,45(1):69-81.
[12] Salemi N,Behfarnia K. Effect of nano-particles on durability of fiber-reinforced concrete pavement[J]. Construction&Building Materials,2013,48(11):934-941.
[13] Arel H,Thomas B S. The effects of nano-and micro-particle additives on the durability and mechanical properties of mortars exposed to internal and external sulfate attacks[J]. Results in Physics,2017,7:843-851.
[14] Tobón J I,PayáJ,Restrepo O J. Study of durability of portland cement mortars blended with silica nanoparticles[J]. Construction&Building Materials,2015,80:92-97.