scholarly journals Experimental Study on a Prediction Model of the Shrinkage and Creep of Recycled Aggregate Concrete

2019 ◽  
Vol 9 (20) ◽  
pp. 4322 ◽  
Author(s):  
Lv ◽  
Liu ◽  
Zhu ◽  
Bai ◽  
Qi
Keyword(s):  
Substitution Rate ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Creep Model ◽  
Aggregate Concrete ◽  
Ordinary Concrete ◽  
Group I ◽  
Significant Difference ◽  
Shrinkage And Creep ◽  
Group Ii

The significant difference between recycled aggregate and natural aggregate is the content of the attached mortar layer. With the increase of the replacement rate of recycled aggregate, the shrinkage and creep of recycled aggregate concrete is significantly increased. In this paper, 180-day shrinkage and creep tests of recycled aggregate concrete with different water–cement ratios were designed in order to analyze the effect of the substitution rate and water–cement ratio on shrinkage and creep properties. The results show that the shrinkage strain of recycled aggregate concrete with a substitution rate of 50% and 100% at 180 days is 26% and 48% higher than that of ordinary concrete, respectively, and the growth of group II is 22% and 47%, respectively. When the load was 180 days old, the creep coefficient of recycled aggregate concrete with a substitution rate of 50% and 100% in group I increased by 19.6% and 39.6%, respectively compared with ordinary concrete, and group II increased by 23.6% and 44.3%, respectively. Based on the difference of adhering mortar content, the creeping increase coefficient and shrinkage increase coefficient of the attached mortar were proposed, and a shrinkage and creep model of recycled aggregate concrete was established. When compared with the experimental results, the model calculation results met the accuracy requirements.

scholarly journals Discrete Element Mesoscale Modeling of Recycled Lump Concrete under Axial Compression

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3140 ◽  
Author(s):  
Yong Yu ◽  
Bo Wu
Keyword(s):  
Mechanical Properties ◽  
Axial Compression ◽  
Discrete Element ◽  
Relative Strength ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Aggregate Concrete ◽  
Ordinary Concrete ◽  
Coarse Aggregates ◽  
Spatial Locations

In the past decade, directly reusing large pieces of coarsely crushed concrete (referred to as demolished concrete lumps or DCLs) with fresh concrete in new construction was demonstrated as an efficient technique for the recycling of waste concrete. Previous studies investigated the mechanical properties of recycled lump concrete (RLC) containing different sizes of DCLs; however, for actual application of this kind of concrete, little information is known about the influence of the spatial locations of DCLs and coarse aggregates on the concrete strength. Moreover, the mechanical responses of such a concrete containing various shapes of DCLs are also not well illustrated. To add knowledge related to these topics, two-dimensional mesoscale simulations of RLC containing DCLs under axial compression were performed using the discrete element method. The main variables of interest were the relative strength of the new and old concrete, the distribution of the lumps and other coarse aggregates, and the shape of the lumps. In addition, the differences in compression behavior between RLC and recycled aggregate concrete were also predicted. The numerical results indicate that the influence tendency of the spatial locations of DCLs and coarse aggregate pieces on the compressive stress–strain curves for RLC is similar to that of the locations of coarse aggregates for ordinary concrete. The strength variability of RLC is generally higher than that of ordinary concrete, regardless of the relative strength of the new and old concrete included; however, variability has no monotonic trend with an increase in the lump replacement ratio. The mechanical properties of RLC in compression are little influenced by the geometric shape of DCLs as long as the ratio of the length of their long axis to short axis is smaller than 2.0. The compressive strength and elastic modulus of RLC are always superior to those of recycled aggregate concrete designed with a conventional mixing method.

On Construction Wastes Recycling and its Economy

2013 ◽  
Vol 567 ◽  
pp. 119-122
Author(s):  
Yue Qin Tang
Keyword(s):  
High Performance ◽  
Drying Shrinkage ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Bleeding Rate ◽  
Aggregate Concrete ◽  
Ordinary Concrete ◽  
Easy Bleeding ◽  
Large Water ◽  
Water Absorbability

This paper addresses problems of aggregate concrete of construction wastes, which were featured as large water absorption, quick slump loss, as well as easy bleeding and low strength of concrete. A comparative analysis by experiment between recycled aggregate concrete and ordinary concrete was made on aspects of water absorbability, compressive strength, slump loss, bleeding rate, drying shrinkage and economic efficiency. It has found possible to preparing the recycled aggregate concrete of high performance through the prewetting recycled aggregate. It is concluded that construction wastes can be recycled by obtaining the optimum mole of preparing recycled aggregate concrete of construction wastes and evaluating their reliability on cost-lefficiency and mechanic capability，thus, it also recycled the limited resources and solve some environment problems.

Application of Molten Slag Fine Aggregate Concrete Using Superplasticizer

2006 ◽  
Vol 302-303 ◽  
pp. 329-338
Author(s):  
Shuzo Otsuka ◽  
Yoshihisa Nakata ◽  
Takeshi Saito ◽  
Hiroki Takahashi ◽  
Keishi Tobinai ◽  
...  
Keyword(s):  
Molten Slag ◽  
Full Scale ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Hardened Concrete ◽  
Fine Aggregate ◽  
Aggregate Concrete ◽  
Significant Difference

With increasing number of melting-solidification plants for the domestic wastes and incineration ashes, the resulting molten slag is now expected as a recycled aggregate for concrete in Japan, while application examples until now are limited to non-loadbearing pre-cast concrete and concrete secondary products. This study deals with a full-scale application of molten slag recycled fine aggregate. Starting with the inspection of monthly variations in quality of molten slag fine aggregate in a plant, construction of a full-scale structure was attempted using the recycled aggregate concrete with a superplasticizer. During construction, pumpability of the recycled concrete was examined and the quality of hardened concrete in the structure was evaluated. It was shown that quality variation of the molten slag fine aggregate during eight months was sufficiently small, and pumpability as well as concrete quality in structure showed no significant difference with those of the ordinary concrete.

Experimental Research on Seismic Behaviour of Low-Carbon Construction Materials RAC Frame Columns

2011 ◽  
Vol 194-196 ◽  
pp. 1958-1961
Author(s):  
Chao Liu ◽  
Guo Liang Bai ◽  
Hong Jin Zhao
Keyword(s):  
Failure Process ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Low Carbon ◽  
Replacement Rate ◽  
Seismic Behaviour ◽  
Aggregate Concrete ◽  
Ordinary Concrete ◽  
Concrete Frame ◽  
Seismic Behaviors

A comparative study is conducted on the seismic behaviors of three recycled aggregate concrete (RAC) frame columns under low cyclic load. The recycled aggregate replacement rate is 0%, 50%, 100% respectively. The mechanical characteristics, failure mode, hysteresis loops, ductility and consumption characteristics of frame columns with different recycled aggregate replacement rate and same axial compression ratio are analyzed in this paper comparatively. The rule characteristics between ordinary concrete and recycled aggregate concrete frame columns are found. The result indicates that failure process of recycled aggregate concrete frame columns is similar to that of ordinary concrete. The seismic behaviors of recycled aggregate concrete frame columns, including the ductility etc., still meet the related requirements of earthquake-resistance designing. So it is concluded in this paper that the recycled aggregate concrete can be applied in concrete structures. Because of its properties are certain deficiencies, some tectonic measures must be enhanced.

Review of Long-Term Deformation of Recycled Coarse and Fine Aggregate Concrete

2013 ◽  
Vol 448-453 ◽  
pp. 734-737
Author(s):  
Jun Li Luo ◽  
Zhi Sheng Xu ◽  
Di Zhao
Keyword(s):  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Quality Level ◽  
Fine Aggregate ◽  
Aggregate Concrete ◽  
Recycled Fine Aggregate ◽  
Deformation Properties ◽  
Shrinkage And Creep ◽  
Creep And Shrinkage

Due to long test cycle, high cost and the complex factors, the long-term deformation properties (such as creep and shrinkage) of recycled aggregate concrete (short for RAC) are rarely reported so far. However this property is essential to fully understanding and widely applying the RAC. Base on investigation on plenty of research results of the long-term deformation of RAC, this paper systematically analyzed the effect of recycled coarse aggregate (C-RA) and recycled fine aggregate (F-RA) on creep and shrinkage performance of concrete. The analysis shows that not only the replacement proportion but also the quality level of recycle aggregate (RA) affect the shrinkage and creep properties of RAC. This outcome could serve as a basis for further research.

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