【作者】 王辉；

【导师】 吴波；

【作者基本信息】 华南理工大学 ， 土木工程， 2021， 硕士

【摘要】 在结构构件中同时采用废混凝土和工程渣土,可显著提升建筑固废的循环利用率,但由此对构件长期性能的影响有待研究。为此,本文同时采用再生块体、再生粗骨料以及源于冲洪积土的水洗砂,制备了再生块体/骨料混凝土,试验研究了该类素混凝土和配筋混凝土的受压徐变性能。主要工作及成果如下:1、开展了1组新混凝土(再生骨料混凝土)试件、1组废旧混凝土试件、4组再生块体/骨料混凝土试件的受压徐变试验,考察了再生块体、再生粗骨料、荷载比、源于冲洪积土的水洗砂等因素对试件徐变性能的影响。研究表明:(1)再生块体/骨料混凝土的徐变度明显大于废旧混凝土,同时也较新混凝土有所偏大;当荷载比不超过0.4时,再生块体/骨料混凝土的徐变变形近似与荷载比成正比;(2)随着新混凝土中再生粗骨料取代率从30%升至50%,再生块体/骨料混凝土的徐变度有所增大,但将新混凝土中天然河砂全部采用水洗砂替代,对再生块体/骨料混凝土的徐变性能几乎没有影响;(3)总体上看,再生块体/骨料混凝土的徐变度大于再生块体混凝土,而与再生骨料混凝土接近。2、基于二相材料模型,修正提出了再生块体/骨料混凝土的弹性模量和徐变预测方法,且从工程实际出发,建议了再生块体/骨料混凝土的徐变简化预测模型。研究表明:(1)无论采用Reuss模型还是Voigt模型,再生块体/骨料混凝土的弹性模量计算结果都大于实测结果,而修正后的Counto模型对该类混凝土弹性模量的预测效果相对较好;(2)修正后基于AAEM法的Counto模型可较好地预测再生块体/骨料混凝土的徐变度;(3)实际工程中无法分别获知新、旧混凝土的徐变响应时,采用本文建议的经两阶段改进的多系数徐变模型,可较好地预测再生块体/骨料混凝土的徐变行为。3、开展了2组配筋新混凝土试件和5组配筋再生块体/骨料混凝土试件的受压徐变试验,考察了配筋率、再生块体、再生粗骨料、荷载比、源于冲洪积土的水洗砂等因素对配筋试件徐变性能的影响。研究表明:(1)纵向配筋对再生块体/骨料混凝土的非持荷变形(主要是收缩变形)具有抑制作用,随着配筋率增大,该抑制作用增强;相较不配筋情况,配筋再生块体/骨料混凝土的徐变更快趋于稳定;(2)总体来看,加入再生块体后配筋试件的徐变度有所增加,但增幅在15%以内;施加荷载相近时,随着配筋率增大,配筋再生块体/骨料混凝土的徐变随之减小;(3)纵向配筋之后,新混凝土中再生粗骨料取代率上升对再生块体/骨料混凝土徐变的不利影响有所改善;(4)将新混凝土中天然河砂全部采用水洗砂替代,对配筋再生块体/骨料混凝土的徐变性能几乎无影响。更多还原

【Abstract】 The use of demolished concrete and excavated soils in structural members can significantly improve the utilization ratio of construction and demolished waste,but its impact on the long-term performance of structural members should be clarified.In this dissertation,recycled lump/aggregate concrete(RLAC)was prepared by simultaneously adopting demolished concrete lumps(DCLs),recycled coarse aggregates(RCAs)and wet-sieving sand from alluvial-diluvial soil.The compressive creep behaviors of RLAC and reinforced RLAC were investigated.The main work and achievements are summarized as follows:1.Experimental study on compressive creep behavior of 1 group of new concrete(recycled aggregate concrete)specimens,1 group of demolished concrete specimens,and 4groups of RLAC specimens was conducted.Influences of the DCLs,RCAs,the stress level,and the wet-sieving sand from alluvial-diluvial soil on the specimens’ creep behavior have been investigated.It can be found that:(1)The specific creep of RLAC is obviously larger than that of demolished concrete,and is also larger than that of new concrete;when the stress level is less than 0.4,the assumption of linear creep is acceptable for the RLAC.(2)As the replacement ratio of RCAs in new concrete increases from 30% to 50%,the specific creep of RLAC increases somewhat.However,the full replacement of alluvial-diluvial soil to river sand has ignorable influences on the creep behavior.(3)On the whole,the specific creep of RLAC is greater than that of recycled lump concrete(RLC),but close to that of recycled aggregate concrete(RAC).2.Based on the two-phase material model,methods for predicting the elastic modulus and creep of RLAC were proposed.Besides,a simplified prediction model for creep of RLAC was suggested in the view of actual application.The findings show that:(1)Predicted values of elastic modulus of RLAC,which are calculated by the Reuss model or the Voigt model,are both lower than the test results,and the Counto model has a better prediction on the elastic modulus of such kind of concrete.(2)The modified Counto model based on the AAEM method can precisely predict the specific creep of RLAC.(3)If the creep response of new concrete and demolished concrete cannot be obtained respectively in actual application,the creep behavior of RLAC can be well predicted by using the two-stage improved multi-coefficient creep model proposed in this paper.3.Creep tests of 2 groups of reinforced new concrete specimens,5 groups of reinforced RLAC specimens were investigated,and the effects of replacement ratio of DCLs and RCAs,stress level,reinforcement ratio and replacement ratio of wet-sieving sand were examined.Test results show that:(1)Longitudinal reinforcement has a restrained effect on the load-independent deformation(mainly govened by shrinkage deformation)of RLAC,and the restrained effect increases with the increase of reinforcement ratio.Compared with unreinforced concrete,the creep of reinforced RLAC tends to be stable earlier.(2)In general,the specific creep of reinforced specimens increases with the utilization of DCLs,but the increasing amplitude is within 15%.When the subjected load is comparable,the creep of reinforced RLAC decreases with the increase of reinforcement ratio.(3)After longitudinal reinforcing,the negative effect due to the increase of the RCAs replacement ratio on the creep behaviors of RLAC is diminished to some extent.(4)The impact on creep behaviors of reinforced RLAC could be neglected when the river sand in RLAC is fully replaced by wet-sieving sand from alluvial-diluvial soil.更多还原