废弃砖再生骨料在混凝土中的应用研究

发布时间：2018-01-03 04:41

本文关键词：废弃砖再生骨料在混凝土中的应用研究　出处：《安徽建筑大学》2015年硕士论文　论文类型：学位论文

【摘要】：再生混凝土是新型绿色材料,有效解决了建筑垃圾回收利用问题。目前,混凝土的耐久性问题越来越受到关注,研究内容不断深入,研究领域不断延伸,而再生混凝土由于再生骨料的加入,耐久性问题研究变的更为复杂,耐久性机理分析也更加困难。本试验研究的是以碎砖作为再生粗骨料的再生混凝土耐久性能。试验中,碎砖骨料取代率为30%,Ⅰ级粉煤灰和减水剂掺量分别为10%和1.5%,采用C40混凝土的配合比。由于再生碎砖骨料吸水性强,需要调整单位用水量,本试验中额外用水量为10%。试验中,先检验再生混凝土28d抗压、抗折强度,测试了再生混凝土的动弹性模量,并与相同配合比的天然碎石混凝土进行了对比。在了解碎砖骨料再生混凝土力学性能的基础上,研究了碎砖骨料再生混凝土的耐久性能和内部孔隙结构,试验结果如下:30%碎砖再生骨料替代天然碎石,再生混凝土的强度变化比较明显,抗压、抗折强度降低幅度分别为13.47%和4.38%,抗压强度衰减速度比抗折强度快,动弹性模量降低了,降低幅度达到11.18%。再生混凝土强度虽然有所降低,但是超出试验配制强度C40,平均值达到53.78MPa。与相同配比的天然碎石骨料混凝土相比,掺加30%碎砖骨料的再生混凝土的耐久性能略有差异。收缩性能方面,再生混凝土3d龄期的收缩应变达到690×10-6,比普通混凝土高46.8%,收缩较大。同时,发现掺加碎砖骨料的再生混凝土的平均渗水高度达到15mm,比普通混凝土高25%,而空气渗透系数干态情况下达到0.058×10-12m2,湿态情况下达到0.032×10-12m2,均比普通混凝土高50%以上。掺加碎砖骨料的再生混凝土抗氯离子渗透性能也相对较差,DRCM达到9.37×10-12m2/s,比普通混凝土高86.1%。但是在抗硫酸盐侵蚀性能方面,20次硫酸盐干湿循环后,再生混凝土的质量未出现衰减,且相对动弹性模量保持在98%以上,即掺加碎砖骨料的再生混凝土抗硫酸侵蚀性能几乎没有影响。不仅如此,碎砖骨料再生混凝土抗碳化性能和抗冻性能均较好。其中,再生混凝土28d碳化深度为0mm,250次冻融循环后,再生混凝土的质量损失率只有0.8%,相对动弹性模量保持在71.1%以上,试件未破坏。研究了再生混凝土硬化后的气孔结构,结果发现:再生混凝土内部的平均孔径达到0.065mm,气泡间距系数达到0.093mm,仅比普通混凝土的平均孔径和气泡间距系数分别高0.025mm以及0.005mm。由此可见,再生混凝土的气泡间距系数也较小,所以抗冻性能较好。再生混凝土耐久性研究尚处在初级阶段,有大量需要解决的问题。如何将实验室中的试验结果与实际环境中的耐久性损伤联系起来,如何将再生混凝土的宏观性能和微观机理结合起来等问题还需要进一步的研究。有关再生混凝土的耐久性标准还不完善,需要完善的标准来规范和指导来再生混凝土的耐久性设计和使用过程中的维护以及使用寿命的评估。
[Abstract]:Recycled concrete is a new kind of green material, which effectively solves the problem of recycling construction waste. At present, the durability of concrete has been paid more and more attention. However, due to the addition of recycled aggregate, the durability of recycled concrete becomes more complex. Durability mechanism analysis is also more difficult. In this experiment, the durability of recycled concrete with broken brick as recycled coarse aggregate is studied. In the test, the replacement ratio of broken brick aggregate is 30%. The mixing amount of grade I fly ash and water reducer is 10% and 1.5 respectively. The mixture ratio of C40 concrete is adopted. Because of the strong water absorption of recycled broken brick aggregate, it is necessary to adjust the unit water consumption. In this experiment, the additional water consumption is 10. In the test, the compressive and flexural strength of recycled concrete is first tested for 28 days, and the dynamic elastic modulus of recycled concrete is tested. On the basis of understanding the mechanical properties of recycled concrete of broken brick aggregate, the durability and internal pore structure of recycled concrete of broken brick aggregate are studied. The test results are as follows: the recycled aggregate of 30% broken brick replaces the natural crushed stone. The strength of recycled concrete changes obviously, the reduction of compressive strength and flexural strength are 13.47% and 4.38% respectively. The attenuation speed of compressive strength is faster than that of flexural strength, and the dynamic elastic modulus is reduced to 11.18%. Although the strength of recycled concrete has been reduced, the strength of recycled concrete is higher than that of experimental compounding strength C40. The average value is 53.78 MPA. Compared with the same proportion of natural crushed stone aggregate concrete, the durability of recycled concrete mixed with 30% crushed brick aggregate is slightly different. The shrinkage strain of recycled concrete is 690 脳 10 ~ (-6), which is 46.8% higher than that of ordinary concrete. It is found that the average seepage height of recycled concrete mixed with crushed brick aggregate is 15 mm, which is 25% higher than that of ordinary concrete, while the air permeability coefficient is 0.058 脳 10 ~ (-12) m ~ 2 in dry state. In wet condition, 0.032 脳 10 ~ (-12) m ~ (2), which is more than 50% higher than that of ordinary concrete, and the permeability of recycled concrete mixed with crushed brick aggregate is also relatively poor. The DRCM reached 9.37 脳 10 ~ (-12) m ~ (2 / s), 86.1 times higher than that of ordinary concrete. The mass of recycled concrete is not attenuated, and the relative dynamic modulus of elasticity is kept above 98%, that is, the sulfuric acid corrosion resistance of recycled concrete with crushed brick aggregate has little effect on it. The carbonation resistance and freezing resistance of recycled concrete of broken brick aggregate are good, among them, the carbonation depth of recycled concrete is 0 mm / 250 times after freezing and thawing cycle for 28 days. The mass loss rate of recycled concrete is only 0. 8 and the relative dynamic modulus of elasticity remains above 71.1%. The pore structure of recycled concrete after hardening is studied. The results show that the average aperture of recycled concrete is 0.065 mm and the coefficient of bubble spacing is 0.093 mm. The average pore diameter and bubble spacing coefficient of recycled concrete are only 0.025 mm and 0.005 mm higher than that of ordinary concrete. Therefore, the durability of recycled concrete is still in the primary stage, there are a lot of problems to be solved. How to link the test results in the laboratory with the durability damage in the actual environment. How to combine the macro performance and micro mechanism of recycled concrete needs further research. The durability standard of recycled concrete is not perfect. Perfect standards are needed to standardize and guide the durability design and maintenance of recycled concrete and to evaluate its service life.
【学位授予单位】：安徽建筑大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528

【参考文献】