再生混凝土改性及配合比设计研究
发布时间：2018-10-16 12:11
【摘要】：建筑垃圾尤其是其中的废弃混凝土越来越多,已经困扰着城市的发展。将废弃混凝土作为骨料来源实现再生利用,可有效解决其作为垃圾处置导致的占地、污染环境等问题,又可缓解天然骨料资源短缺的局面,还可避免因开采山石而造成的自然生态环境破坏。再生骨料应用于混凝土,首先要解决再生混凝土的配制问题,其关键是配合比设计。一般地,由于再生骨料质量比天然骨料差,导致配制出的同强度等级的再生混凝土质量劣于普通混凝土,因此对再生骨料和再生混凝土进行性能优化具有重要的意义。本文主要基于试验研究的方法,并结合理论分析,对再生混凝土的强度影响因素、配合比设计及其改性进行了较为深入的研究;研究了再生混凝土的细观组成和结构,基于数值仿真方法模拟了其压缩破坏过程,对其破坏机理和特征进行了探讨。主要工作及结论如下:对影响再生混凝土抗压和劈拉强度的主要因素:水灰比、水泥强度等级、砂率、骨料最大粒径、骨料级配、养护龄期进行了试验研究。结果表明:水灰比控制在0.45±0.05是比较合适的,低于此值则再生混凝土工作性差,高于此值则强度将急剧下降;砂率为35%时抗压强度最高;再生骨料最大粒径为20mm时抗压和劈拉强度都最高;根据最大密度曲线确定的再生骨料级配下的混凝土抗压和劈拉强度最高;随着养护龄期的增长,水灰比越小,抗压和劈拉强度增长速率越大;90d强度比28d强度均有较大幅度的增长;抗压和劈拉强度均与灰水比大致呈线性关系;90d抗压强度比普通混凝土低约10%。基于7d强度建立了再生混凝土抗压强度增长的预测公式。建立了再生粗骨料吸水量、(单位体积)附加用水量等同其质量、吸水率、含水率的关系;确定了再生粗骨料混凝土和全再生骨料混凝土抗压强度与灰水比之间的关系及这两种混凝土强度计算中的骨料系数;提出了基于附加用水量的再生混凝土配合比设计步骤和方法及“有效水灰比”和“名义水灰比”的概念。为优化再生混凝土性能,分别从制备工艺和强化方法两方面出发进行了研究。制备工艺的研究结果表明:二次搅拌工艺不但能提高再生混凝土的抗压和劈拉强度,还能改善其工作性能,且强度离散性小,是制备再生混凝土的一种较好的工艺,比目前广泛应用的普通工艺好。强化再生混凝土性能方面,采用了:(1)钢纤维和粉煤灰(增强工作性)强化再生混凝土;(2)DSP和RPC浆液强化再生骨料;(3)DSP和RPC浆液强化再生混凝土等三种方法。结果表明:(1)以上三种方法均能较好地实现强化再生混凝土的抗压和劈拉强度的目标;(2)对钢纤维(粉煤灰)强化再生混凝土而言,钢纤维掺量越大强度越高,但其工作性大大降低,需要粉煤灰来增强流动性,但粉煤灰取代率不宜过高,建议小于10%,否则强度会有大幅度下降;(3)DSP和RPC浆液强化再生骨料均能显著提高再生骨料的强度;(4)DSP和RPC浆液强化再生混凝土,均能显著提高再生混凝土的强度。混凝土的宏观性能是由其细微观结构决定的,通过SEM观察分析了再生混凝土和普通混凝土在细观组成、砂浆内部结构和界面结构上的特征,提出了改善再生混凝土界面性能的方法和途径。采用随机算法,建立了再生混凝土细观模型,对其单轴压缩破坏过程进行了数值模拟。探讨了再生粗骨料取代率、新砂浆强度、老砂浆强度和界面过渡区强度对再生混凝土压缩性能的影响。讨论了再生粗骨料取代率为100%情况下,新砂浆、老砂浆、新界面和老界面的相对强度对再生混凝土单轴压缩破坏特征的影响;结果表明:压缩破坏均先从最薄弱的界面处开始;当老界面强度相对最低时,则再生混凝土的抗压性能最好;当新界面强度相对最低时,则再生混凝土的抗压性能最差;因此,在配制再生混凝土时要尽量提高新砂浆和新界面的强度。
[Abstract]:The construction waste, especially the waste concrete in it, is becoming more and more and has been bothering the development of the city. the waste concrete is used as the source of the aggregate to realize the regeneration and utilization so as to effectively solve the problems of land occupation, environmental pollution and the like caused by waste disposal, can alleviate the situation of shortage of natural aggregate resources, and can also avoid the natural ecological environment damage caused by the mining of the rock. Recycled aggregate is applied to concrete. Firstly, it is necessary to solve the preparation problem of recycled concrete, and its key is to mix proportion design. Generally, because the quality of recycled aggregate is worse than that of natural aggregate, the quality of recycled concrete with the same strength grade is inferior to that of ordinary concrete, so it is of great significance to optimize the performance of recycled aggregate and recycled concrete. Based on the method of experimental research and combined with the theoretical analysis, the influence factors on the strength of recycled concrete are studied deeply, and the microstructure and structure of recycled concrete are studied. Based on the numerical simulation method, the compression failure process is simulated, and its failure mechanism and characteristics are discussed. The main work and conclusions are as follows: The main factors influencing the compressive strength and tensile strength of recycled concrete are as follows: cement ratio, cement strength grade, sand ratio, maximum aggregate size of aggregate, aggregate gradation and curing age. The results show that the compressive strength and the tensile strength of the recycled aggregate are the highest when the maximum particle size of the recycled aggregate is 20 mm, the compressive strength and the tensile strength of the recycled aggregate are the highest when compared with the value of 0. 45 and 0. 05. The compressive strength and tensile strength of concrete are the highest according to the maximum density curve. With the increase of curing age, the smaller the tensile strength, the higher the compressive strength and the tensile strength increase, and the 90d strength has a higher strength than the 28d strength. The compressive strength and tensile strength are generally linear with ash-water ratio; 90d compressive strength is about 10% lower than that of ordinary concrete. The prediction formula of compressive strength growth of recycled concrete was established based on 7d strength. The relationship between the water absorption and water absorption and water content of recycled coarse aggregate is established. The relationship between the compressive strength and ash-water ratio of recycled coarse aggregate concrete and all-recycled aggregate concrete and the aggregate coefficient in the calculation of these two concrete strength are determined. The design steps and methods of regeneration concrete mixing ratio based on additional water consumption and the concept of 鈥渆ffective anti-inflammatory agent鈥，
本文编号：2274314
[Abstract]:The construction waste, especially the waste concrete in it, is becoming more and more and has been bothering the development of the city. the waste concrete is used as the source of the aggregate to realize the regeneration and utilization so as to effectively solve the problems of land occupation, environmental pollution and the like caused by waste disposal, can alleviate the situation of shortage of natural aggregate resources, and can also avoid the natural ecological environment damage caused by the mining of the rock. Recycled aggregate is applied to concrete. Firstly, it is necessary to solve the preparation problem of recycled concrete, and its key is to mix proportion design. Generally, because the quality of recycled aggregate is worse than that of natural aggregate, the quality of recycled concrete with the same strength grade is inferior to that of ordinary concrete, so it is of great significance to optimize the performance of recycled aggregate and recycled concrete. Based on the method of experimental research and combined with the theoretical analysis, the influence factors on the strength of recycled concrete are studied deeply, and the microstructure and structure of recycled concrete are studied. Based on the numerical simulation method, the compression failure process is simulated, and its failure mechanism and characteristics are discussed. The main work and conclusions are as follows: The main factors influencing the compressive strength and tensile strength of recycled concrete are as follows: cement ratio, cement strength grade, sand ratio, maximum aggregate size of aggregate, aggregate gradation and curing age. The results show that the compressive strength and the tensile strength of the recycled aggregate are the highest when the maximum particle size of the recycled aggregate is 20 mm, the compressive strength and the tensile strength of the recycled aggregate are the highest when compared with the value of 0. 45 and 0. 05. The compressive strength and tensile strength of concrete are the highest according to the maximum density curve. With the increase of curing age, the smaller the tensile strength, the higher the compressive strength and the tensile strength increase, and the 90d strength has a higher strength than the 28d strength. The compressive strength and tensile strength are generally linear with ash-water ratio; 90d compressive strength is about 10% lower than that of ordinary concrete. The prediction formula of compressive strength growth of recycled concrete was established based on 7d strength. The relationship between the water absorption and water absorption and water content of recycled coarse aggregate is established. The relationship between the compressive strength and ash-water ratio of recycled coarse aggregate concrete and all-recycled aggregate concrete and the aggregate coefficient in the calculation of these two concrete strength are determined. The design steps and methods of regeneration concrete mixing ratio based on additional water consumption and the concept of 鈥渆ffective anti-inflammatory agent鈥，
本文编号：2274314
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