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二次再生混凝土力学性能研究

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为推进再生混凝土二次循环利用,研究二次再生粗骨料取代率对二次再生混凝土力学性能的影响,制备了取代率为 0、20%、40%、60%、80%、100%共 6组试件,测其坍落度、抗压强度、劈裂抗拉强度、抗压变形,并结合扫描电镜进行孔结构及微观研究分析.结果表明:随着二次再生粗骨料取代率的增加,坍落度逐渐降低,全取代时降幅达到最大 100 mm;孔结构分析表明随着二次再生粗骨料取代率的增加,试块中小孔占比逐渐减小,大孔占比逐渐增加,混凝土中孔体积逐渐增加,造成混凝土结构不密实,其次造成试块中骨料占比逐渐减少,老化砂浆和气泡占比逐渐增加,不利于强度发展;二次再生混凝土整体上满足 C35 强度要求,随取代率的提高整体强度呈下降趋势,整体变形呈上升的趋势,除骨料压碎指标较大有关外,结合孔结构分析与二次再生混凝土中骨料占比逐渐减少老化砂浆和气泡占比逐渐增加有关,使试块强度降低且更容易发生变形;二次再生混凝土的微观结构观察证实了对试块抗压强度、抗压变形的宏观实测数据及原因分析;结合宏观实测数据及微观结构观察,二次再生混凝土的应用具有一定可行性.
Study on mechanical properties of secondary recycled concrete
In order to promote the secondary recycling of recycled concrete,the effect of secondary recycled coarse aggregate replacement rate on the mechanical properties of secondary recycled concrete was studied.Six groups of specimens with replacement rates of 0,20%,40%,60%,80%and 100%were prepared.The slump,compressive strength,splitting tensile strength and compressive deformation were measured,and the pore structure and microstructure were analyzed by scanning electron microscopy.The results show that with the increase of the replacement rate of the secondary recycled coarse aggregate,the slump gradually decreases,and the maximum decrease reaches 100 mm when the secondary recycled coarse aggregate is completely replaced.The analysis of pore structure shows that with the increase of the replacement rate of secondary recycled coarse aggregate,the proportion of small pores in the test block gradually decreases,the proportion of large pores gradually increases,and the volume of pores in the concrete gradually increases,resulting in the uncompacted concrete structure.Secondly,the proportion of aggregate in the test block gradually decreases,and the proportion of aging mortar and bubbles gradually increases,which is not conducive to the development of strength.The secondary recycled concrete generally meets the C35 strength requirements.With the increase of the replacement rate,the overall strength shows a downward trend,and the overall deformation shows an upward trend.In addition to the large aggregate crushing index,the pore structure analysis is related to the gradual decrease of the aggregate ratio in the secondary recycled concrete and the gradual increase of the proportion of aging mortar and bubbles,which reduces the strength of the test block and makes it more prone to deformation.The microstructure observation of secondary recycled concrete confirms the macroscopic measured data and cause analysis of the compressive strength and compressive deformation of the test block.Combined with the macroscopic measured data and microstructure observation,the application of secondary recycled concrete is feasible.

secondary recycled concretestrengthpore structureSEM

张玉栋、谢龙、张富钧、张佳帅、曹颖卓、高玉增

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河北建筑工程学院 河北省土木工程诊断、改造与抗灾重点实验室,河北 张家口 075000

二次再生混凝土 强度 孔结构 扫描电镜

国家自然科学基金青年基金河北省教育厅青年基金项目河北省高等学校科学技术研究项目

U1334209QN2020191Z2018203

2024

混凝土
中国建筑东北设计研究院有限公司

混凝土

CSTPCD北大核心
影响因子:0.844
ISSN:1002-3550
年,卷(期):2024.(7)