Development, production, and control of a high replacement rate recycled concrete

2019 ◽  
pp. 299-309
Author(s):  
S. Favre ◽  
G. Noworyta ◽  
T. Sedran
Keyword(s):  
Recycled Concrete ◽  
Replacement Rate ◽  
And Control

Recirculation versus flow-through rainbow trout laboratory Flavobacterium columnare challenge

2020 ◽  
Vol 139 ◽  
pp. 213-221
Author(s):  
C Birkett ◽  
R Lipscomb ◽  
T Moreland ◽  
T Leeds ◽  
JP Evenhuis
Keyword(s):  
Rainbow Trout ◽  
Environmental Parameters ◽  
Cumulative Effects ◽  
Flavobacterium Columnare ◽  
Replacement Rate ◽  
Bacterial Concentration ◽  
Water Replacement ◽  
Dose Concentration ◽  
Flow Through ◽  
And Control

Flavobacterium columnare immersion challenges are affected by water-related environmental parameters and thus are difficult to reproduce. Whereas these challenges are typically conducted using flow-through systems, use of a recirculating challenge system to control environmental parameters may improve reproducibility. We compared mortality, bacterial concentration, and environmental parameters between flow-through and recirculating immersion challenge systems under laboratory conditions using 20 rainbow trout families. Despite identical dose concentration (1:75 dilution), duration of challenge, lot of fish, and temperature, average mortality in the recirculating system (42%) was lower (p < 0.01) compared to the flow-through system (77%), and there was low correlation (r = 0.24) of family mortality. Mean days to death (3.25 vs. 2.99 d) and aquaria-to-aquaria variation (9.6 vs. 10.4%) in the recirculating and flow-through systems, respectively, did not differ (p ≥ 0.30). Despite 10-fold lower water replacement rate in the recirculating (0.4 exchanges h-1) compared to flow-through system (4 exchanges h-1), differences in bacterial concentration between the 2 systems were modest (≤0.6 orders of magnitude) and inconsistent throughout the 21 d challenge. Compared to the flow-through system, dissolved oxygen during the 1 h exposure and pH were greater (p ≤ 0.02), and calcium and hardness were lower (p ≤ 0.03), in the recirculating system. Although this study was not designed to test effects of specific environmental parameters on mortality, it demonstrates that the cumulative effects of these parameters result in poor reproducibility. A recirculating immersion challenge model may be warranted to empirically identify and control environmental parameters affecting mortality and thus may serve as a more repeatable laboratory challenge model.

Study on the Mechanical Properties and Frost Resistance of Recycled Concrete Prepared by Village Construction Wastes

2011 ◽  
Vol 418-420 ◽  
pp. 406-410
Author(s):  
Jun Liu ◽  
Yao Li ◽  
Dan Dan Hong ◽  
Yu Liu
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Frost Resistance ◽  
Cement Mortar ◽  
Strength Loss ◽  
Recycled Concrete ◽  
Recycled Aggregate ◽  
Replacement Rate ◽  
Concrete Mechanical Properties ◽  
Better Than

Abstract. Recycled aggregate—rural building material wastes pretreated by cement mortar—are applied into concrete with different replacement rates: 0, 25%, 50%, 75%, and 100%. Results from measurements of compressive strength, cleavage tensile strength, mass loss after fast freeze-thaw cycles, and compressive strength loss indicate that a different recycled aggregate replacement rate certainly influences concrete mechanical properties and frost resistance. Recycled aggregate replacement rates less than 75% performs better than common concrete. Data from the 100% replacement rate is worse than that of rates less than 75% but still satisfy the general demands of GB standard on C30 concrete.

Finite Element Analysis of High Strength Recycled Concrete Beam Flexural Properties

2015 ◽  
Vol 730 ◽  
pp. 11-14 ◽  
Author(s):  
Hai Long Zhang ◽  
Chang Chun Pei
Keyword(s):  
Finite Element Analysis ◽  
Concrete Beam ◽  
Coarse Aggregate ◽  
High Strength ◽  
Recycled Concrete ◽  
Replacement Rate ◽  
Element Analysis ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Recycled Coarse Aggregate

By ANSYS finite element analysis we study the impact-span moment and deflection of high strength recycled concrete beam in state of initial cracking and yield with different water-cement ratio and recycled coarse aggregate replacement rate. The results showed that: 1With the increase of water-cement ratio and recycled coarse aggregate replacement rate, the deflection is on the rise. 2With the increase of recycled coarse aggregate replacement rate, the yield moment has a slight upward trend. And with the increase of water-cement ratio and recycled coarse aggregate replacement rate, the span deflection at the state of yield has a growing trend.

The Study of Field Effect through Uniaxial Compression Experiment on Marine Recycled Concrete Specimen Based on DPDM Technique

2012 ◽  
Vol 446-449 ◽  
pp. 1735-1742
Author(s):  
Wen Bai Liu ◽  
Chao Shen ◽  
Xia Li ◽  
Hong Ming Jiang
Keyword(s):  
Uniaxial Compression ◽  
Field Effect ◽  
Strain Curve ◽  
Heterogeneous Material ◽  
Concrete Specimen ◽  
Middle Part ◽  
Recycled Concrete ◽  
Recycled Aggregate ◽  
Replacement Rate ◽  
Compression Resistance

Recycled concrete is a kind of composite heterogeneous material. Through the uniaxial compression experiment on recycled concrete specimen, the corresponding stress-strain curve is depicted with the major variables of replacement rate of recycled aggregate and time of corrosion by seawater, and the analysis of compression resistance capacity of recycled concrete sample is carried out by comparing common samples with those after the process of vacuum pumping. According to the results of comparison, the process of vacuum pumping can raise the strength of concrete by 9% to 22% and the lowering speed of compression resistance capacity rises as replacement rate of recycled aggregate goes up after the same corrosion period. The compression resistance capacity of the concrete specimen with replacement rate of 60% descends 50% to 80% faster than the sample with 30% of rate. DPDM technique is used to analyze deformation field, displacement field and strain field of concrete specimen during the process of uniaxial compression. As shown in the images from the experiment, the cracks develop from the bottom and both edges towards the middle part along the direction of loading until some of them run through the cube with the failure of the overall specimen while the stress reaches the peak, the displacement amount decreases from bottom to top and from both edges to center and the greatest strain concentration scatters around the bottom of the specimen while the strain of 62% appears around the peak stress of 33-36MPa. This paper puts forward constructive references and guidance for the application of recycled concrete in marine engineering on the basis of the study of field effect through uniaxial compression experiment based on DPDM technique.

Experimental Study on Mechanical Properties of Recycled Concrete Specimens of Marine Engineering

2011 ◽  
Vol 71-78 ◽  
pp. 331-337
Author(s):  
Wen Bai Liu ◽  
Xia Li
Keyword(s):  
Mechanical Properties ◽  
Experimental Study ◽  
Engineering Application ◽  
Recycled Concrete ◽  
Recycled Aggregate ◽  
Replacement Rate ◽  
Replacement Ratio ◽  
Ordinary Concrete ◽  
Seawater Corrosion ◽  
Marine Engineering

Mechanical properties of recycled concrete under different conditions were studied in this paper. Based on three kinds of replacement percentage of recycled aggregate and four kinds of seawater corrosion conditions, the experimental study of mechanical properties of recycled concrete specimens corroded by seawater and produced under vacuum conditions were conducted, and compared with that of ordinary concrete specimens. Testing results show that compressive strength of recycled concrete decreases with the increase of both the replacement rate of recycled aggregate and the corrosion time by seawater, with the maximum reduce value is 17.96% and 24.52%; Vacuum conditions effectively improve the strength of recycled concrete, improved value is 1.03-1.19 times of the same replacement ratio of recycled aggregate, and 1.00-1.16 times of the ordinary concrete. It provides the reference for marine engineering application of recycled concrete.

Performance of Rigid Pavements Containing Recycled Concrete Aggregates

1997 ◽  
Vol 1574 (1) ◽  
pp. 89-98 ◽  
Author(s):  
Gregory D. Cuttell ◽  
Mark B. Snyder ◽  
Julie M. Vandenbossche ◽  
Monty J. Wade
Keyword(s):  
Recycled Concrete ◽  
Clear Correlation ◽  
Concrete Aggregate ◽  
Portland Cement Concrete ◽  
Recycled Concrete Aggregates ◽  
State Highway ◽  
Rigid Pavements ◽  
Field Investigations ◽  
State Highway Agencies ◽  
And Control

State highway agencies in Connecticut, Kansas, Minnesota, Wisconsin, and Wyoming have successfully designed and constructed rigid pavements containing recycled concrete aggregate (RCA). Success has been attributed in part to the minimization of old mortar content in the RCA during recycling processes, thereby controlling the total mortar content of the new portland cement concrete (PCC) mixture, or to the achievement of higher-than-expected compressive strengths through adjustments in mix proportions, or both. There was no clear correlation between mortar content and cracking distresses in field investigations, although one project did exhibit significantly more slab cracking in the recycled pavement than in the corresponding control pavement. The increased cracking may have been due to the large differences in total mortar content between the recycled and control sections. In general, the recycled PCC pavements considered in this study have performed comparably with their conventional PCC pavement counterparts, including the recycled pavements that incorporated RCA derived from concrete affected by D-cracking and alkali-silica reactivity (ASR). There is, however, evidence of small amounts of localized recurrent ASR in the recycled Wyoming pavement. Whether this reactivity will eventually develop into widespread distress remains to be seen.

scholarly journals Compressive Strength Study on the Freeze-thaw Resistance of Recycled Aggregate Concrete Members

2017 ◽  
Vol 11 (1) ◽  
pp. 270-280 ◽  
Author(s):  
Haicheng Niu ◽  
Yonggui Wang ◽  
Xianggang Zhang ◽  
Xiaojing Yin
Keyword(s):  
Compressive Strength ◽  
Mass Loss ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Fine Aggregate ◽  
Replacement Rate ◽  
Aggregate Concrete ◽  
Freeze Thaw ◽  
Surface Scaling

Introduction: Freeze-thaw resistance of recycled aggregate concrete with partial or total replacement of recycled aggregate compared with that of natural aggregate concrete was investigated in this paper. Method: Ninety specimens were fabricated to study the influence of different recycled aggregate replacement ratios on the surface scaling, mass loss, and residual compressive strength after 100 freeze-thaw cycles. Results: The experiment results indicate that the type of recycled aggregate and its replacement ratio have significant effects on the freeze-thaw performance. The cubic compressive strength of recycled aggregate concrete is overall slightly lower than that of normal concrete. After 100 freeze-thaw cycles, the compressive strength decreases and the reduction extent increases with increasing replacement rate of recycled aggregate. The surface scaling of reinforced recycled concrete prisms tends to be more severe with the increase of freeze-thaw cycles. Conclusion: Furthermore, a notable rise in mass loss and the bearing capacity loss is also found as the substitution ratio increases. Under the same replacement rate, recycled fine aggregate causes more negative effects on the freeze-thaw resistance than recycled coarse aggregate.

scholarly journals Durability of concrete containing aggregate produced from recycled concrete affected by alkali-silica reaction

2021 ◽  
Author(s):  
Chris Christidis
Keyword(s):  
Coarse Aggregate ◽  
High Reactivity ◽  
Recycled Concrete ◽  
Alkali Silica Reaction ◽  
Concrete Aggregate ◽  
Freezing And Thawing ◽  
Salt Scaling ◽  
And Control ◽  
Minimal Information ◽  
Durability Of Concrete

Minimal information is available on the durability of concrete containing demolished concrete as an aggregate. The purpose of this study was to: investigate and control the reactivity of recycled concrete aggregate (RCA) produced from concrete that was suffering from alkali silica reaction (ASR); and investigate other durability issues of concrete containing RCA with emphasis on salt scaling and freezing & thawing. It was deduced that the RCA produced from ASR-affected concrete caused expansion when used in new concrete as an aggregate. This high reactivity of the tested RCA was attributable to its relatively high alkalis and calcium contents. Furthermore, a greater amount of SCM was required to reduce expansion compared to concrete containing raw natural reactive aggregate. In terms of freezing and thawing and salt scaling, concrete containing coarse RCA at a 100% replacement level of coarse aggregate showed lower durability compared to concrete made with natural coarse aggregate.

scholarly journals Capillary Water Absorption Characteristics of Recycled Concrete in Freeze-Thaw Environment

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Qianhui Xiao ◽  
Xiaolin Liu ◽  
Jisheng Qiu ◽  
Yangyang Li
Keyword(s):  
Prediction Model ◽  
Water Absorption ◽  
Coarse Aggregate ◽  
Recycled Concrete ◽  
Capillary Water ◽  
Replacement Rate ◽  
Capillary Water Absorption ◽  
Freeze Thaw ◽  
Recycled Coarse Aggregate ◽  
Absorption Characteristics

In order to study the capillary water absorption characteristics of recycled concrete (RAC) with different replacement rates of recycled coarse aggregate (0, 20%, 40%, and 60%) in freeze-thaw environment, the standard test method of measuring the water absorption of hydraulic cement concrete (ASTM C1585-13) was adopted, and the influence mechanism of freeze-thaw cycle and replacement rate of recycled coarse aggregate on the capillary water absorption of RAC was analyzed, and a prediction model of initial capillary water absorption of RAC in freeze-thaw environment was established. The results show that when the freeze-thaw environment is the same, the greater the replacement rate of recycled coarse aggregate, the greater the cumulative water absorption of RAC, the faster the initial capillary water absorption, and the stronger the capillary water absorption; when the freeze-thaw environment is different, the more the freeze-thaw cycles, the greater the cumulative water absorption of RAC with the same replacement rate of recycled coarse aggregate, the faster the initial capillary water absorption, and the stronger the capillary water absorption. The prediction model of RAC initial capillary water absorption established by regression analysis has high accuracy, which can be used to predict RAC capillary water absorption performance and provide theoretical basis for the research of RAC frost resistance durability.

Experimental Study on Flexural Property of Reinforced Concrete Beams with Recycled Aggregate of Construction Waste

2012 ◽  
Vol 517 ◽  
pp. 601-605
Author(s):  
Zhao Hua Du ◽  
Tong Hao ◽  
Li Xin Liu
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beams ◽  
Recycled Concrete ◽  
Reinforced Concrete Beams ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Flexural Property ◽  
Test Results ◽  
Replacement Rate ◽  
Construction Waste

This paper presents the test results of 6 reinforced concrete beams with recycled aggregates of construction waste under flexure, the beams were made of two strength grade concrete of and with different recycled aggregate replacement rate. The results indicate: the ultimate bearing capacity of recycled concrete beams with natural aggregate concrete beams are almost the same, and can meet the requirements of chinese code; The cracking resistance of the reinforced recycled concrete beams is slightly less than that of the beams with natural aggregates, the influence of recycled aggregate replacement rate to cracking resistance is not obvious. Recycled concrete beam crack load the calculated value is greater than the measured value, should carry out the theoretical value adjustment. Reinforced concrete beams is one of concrete structures, its the most common and most important component, Study of flexural property of reinforced concrete for recycled concrete structure component in the popularization and application to have the important significance [. This paper presents the test results of 6 reinforced concrete beams with recycled aggregates of construction waste under flexure, the beams were made of two strength grade concrete of C30 and C40 and with different recycled aggregate replacement rate of 0%, 50% and 70%. These results may be as a reference for the application of the concrete with recycled aggregates of construction waste in engineering [2,3,.

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