scholarly journals Engineering and Manufacturing Technology of Green Epoxy Resin Coatings Modified with Recycled Fine Aggregates

2021 ◽  
Author(s):  
Kamil Krzywiński ◽  
Łukasz Sadowski ◽  
Damian Stefaniuk ◽  
Aleksei Obrosov ◽  
Sabine Weiß
Keyword(s):  
Mechanical Properties ◽  
Epoxy Resin ◽  
Construction And Demolition Waste ◽  
Fine Aggregate ◽  
Micro Computed Tomography ◽  
Demolition Waste ◽  
Replacement Ratio ◽  
Recycled Fine Aggregate ◽  
Fine Aggregates ◽  
Computed Tomography Scanning

AbstractNowadays, the recycled fine aggregate sourced from construction and demolition waste is not frequently used in manufacturing of epoxy resin coatings. Therefore, the main novelty of the article is to prepare green epoxy resin coatings modified with recycled fine aggregate in a replacement ratio of natural fine aggregate ranged from 20 to 100%. The microstructural properties of the aggregates and epoxy resin were analyzed using micro-computed tomography, scanning electron microscopy and nanoindentation. The macroscopic mechanical properties were examined using pull-off strength tests. The highest improvement of the mechanical properties was observed for epoxy resin coatings modified with 20% of natural fine aggregate and 80% of recycled fine aggregate. It has been found that even 100% of natural fine aggregate can be successfully replaced using the recycled fine aggregate with consequent improvement of the pull-off strength of analyzed epoxy resin coatings. In order to confirm the assumptions resulting from the conducted research, an original analytical and numerical failure model proved the superior behavior of modified coating was developed.

Influence of Recycled Aggregate on the Rheological Behavior of Cement Mortar

2014 ◽  
Vol 600 ◽  
pp. 297-307 ◽  
Author(s):  
Paulo Roberto Lopes Lima ◽  
Romildo Dias Toledo Filho ◽  
Otávio da Fonseca Martins Gomes
Keyword(s):  
Yield Stress ◽  
Plastic Viscosity ◽  
Construction And Demolition Waste ◽  
Recycled Aggregate ◽  
Fine Aggregate ◽  
Demolition Waste ◽  
Cement Ratio ◽  
Recycled Fine Aggregate ◽  
Fine Aggregates ◽  
Physical Tests

In this work it was studied the influence of recycled fine aggregate obtained from construction and demolition waste (CDW) on the rheological properties of Portland cement mortars. The CDW was initially separate in their main constituents (mortar, ceramic and concrete debris) at the laboratory and then grinded separately to the sand size in order to generate more homogeneous fine aggregates. The characterization of the natural and recycled sands was carried out through physical tests, X-ray diffraction, scanning electron microscopy (SEM), and image analysis (shape and texture description parameters). A conventional mortar and three mortars containing recycled sands were produced with a sand/cement ratio of 4 and consistency index of 255±5 mm. The consistency was kept constant by ranging the water-cement ratio from 0.58 to 1.14. The rheological study was performed using a rotating viscometer to obtain torque-rotation ratio and to calculate the yield stress and plastic viscosity. The results indicate that the presence of recycled aggregate causes a lowering of both yield stress and plastic viscosity with respect to the mortar containing natural aggregate.

The Properties of Fine Recycled Aggregate Concrete Containing Recycled Bricks from Construction and Demolition Waste

2018 ◽  
Vol 760 ◽  
pp. 193-198 ◽  
Author(s):  
Kristina Fořtová ◽  
Tereza Pavlů
Keyword(s):  
Recycled Aggregate Concrete ◽  
Construction And Demolition Waste ◽  
Recycled Aggregate ◽  
Partial Replacement ◽  
Fine Aggregate ◽  
Demolition Waste ◽  
Natural Sand ◽  
Aggregate Concrete ◽  
Freeze Thaw ◽  
Recycled Fine Aggregate

This paper presents research results of recycled fine aggregate concrete testing. The main aim of this contribution is verification of properties of fine aggregate concrete with partial replacement of fine natural aggregate by recycled masonry aggregate originated from construction and demolition waste. The influence of partial replacement of natural sand to mechanical properties and freeze-thaw resistance is described. The compressive strength and flexural strength were tested at the age of 28 and 60 days and after 25, 50, 75 and 100 freeze-thaw cycles. Partial replacement of natural sand was 0, 25 and 50 % for all these tests. Prismatic specimens were examined.

scholarly journals Bond Behavior Between Recycled Concrete Containing CDW and Different Types of Steel Bars

2021 ◽  
Vol 4 (2) ◽  
Author(s):  
Carine N. S. Reis ◽  
Paulo R. L. Lima ◽  
Mônica B. Leite
Keyword(s):  
Recycled Concrete ◽  
Construction And Demolition Waste ◽  
Recycled Aggregate ◽  
Fine Aggregate ◽  
Demolition Waste ◽  
Conventional Concrete ◽  
Recycled Fine Aggregate ◽  
Steel Bar ◽  
Internal Forces ◽  
Steel Rebars

The operation of reinforced concrete structures is directly associated with the adhesion between the steel bar and the concrete, which allows the internal forces to be transferred to the reinforcement during the process of loading the structural elements. The modification of the concrete composition, with the introduction of recycled aggregate from construction and demolition waste (CDW), affects the steel-concrete interface and can modify the bonding stress, which is also influenced by the type and diameter of the bar used. In this work, the influence of the recycled fine aggregate (RFA) and types of steel bar on the steel-concrete bond was experimentally evaluated using the pullout test. Conventional concrete and recycled concrete, with RFA replacement level of 25%, were produced. Two types of steel rebars (i.e.,plain and deformed) with  diameters of 10.0 and 16.0mm were considered in this paper. The results indicate a reduction in the adhesion stress with the introduction of recycled aggregate, but this trend is influenced by the diameter of the bar used. The use of ribbed bars modifies the stress bon-slip behavior, with an increase in the average bond strength, which is also observed with the reduction of the diameter of the bar.

scholarly journals Preliminary Analysis of the Use of Construction Waste to Replace Conventional Aggregates in Concrete

Buildings ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 81
Author(s):  
Fernando A. N. Silva ◽  
João M. P. Q. Delgado ◽  
António C. Azevedo ◽  
António G. B. Lima ◽  
Castorina S. Vieira
Keyword(s):  
Compressive Strength ◽  
Coarse Aggregate ◽  
Recycled Aggregate Concrete ◽  
Construction And Demolition Waste ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Fine Aggregate ◽  
Demolition Waste ◽  
Fine Aggregates ◽  
Mechanical Strengths

This work aims to study the influence of using construction and demolition waste in the replacement of coarse and fine aggregate to produce recycled aggregate concrete (RAC). A moderate compressive strength concrete made with usual fine and coarse aggregate was used as a benchmark material. Compressive and split tensile tests were performed using 120 cylindrical concrete specimens with 150 mm diameter and 300 mm length. Four-point flexural tests in reinforced beams made with conventional concrete and RAC were performed. The results obtained showed that the use of recycled fine aggregates, in both percentages of substitution investigated—50% and 100%— did not generate any deleterious influence on the values of compressive strength and split tensile strength of the RACs produced. Tin fact, the mechanical strengths of RACs produced with recycled fine aggregate were equal or higher than those from the reference concrete. The same behavior was not observed, however, when the recycled coarse aggregate was used. For this case, decreases in concrete mechanical strengths were observed, especially in compressive strength, with values around 35% lower when compared to the reference concrete. Tensile mechanical tests results confirmed the excellent behavior of all RACs made with replacement of usual fine aggregates by recycled. Bending tests performed in reinforced RAC beams had as objective to evaluate the deformation profile of the beams. The obtained results showed that RAC beams with full replacement of usual fine aggregate by the recycled aggregates have presented little changes in the global behavior, an aspect that encourages its use.

scholarly journals Time-Dependent Shrinkage Model for Recycled Fine Aggregate Thermal Insulation Concrete

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5581
Author(s):  
Xuhang Zang ◽  
Pinghua Zhu ◽  
Chunhong Chen ◽  
Xiancui Yan ◽  
Xinjie Wang
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Thermal Insulation ◽  
Shrinkage Strain ◽  
Time Dependent ◽  
Recycled Aggregate ◽  
Fine Aggregate ◽  
Replacement Ratio ◽  
Recycled Fine Aggregate ◽  
Total Shrinkage

In this study, the shrinkage performance of recycled aggregate thermal insulation concrete (RATIC) with added glazed hollow beads (GHB) was investigated and a time-dependent shrinkage model was proposed. Two types of recycled fine aggregate (RFA) were used to replace natural fine aggregate in RATIC: RFA from waste concrete (RFA1) and waste clay brick (RFA2). Besides, the mechanical properties and thermal insulation performance of RATIC were also studied. Results showed that the pozzolanic reaction caused by RFA2 effectively improved the mechanical properties of RATIC; 75% was the optimal replacement ratio of RATIC prepared by RFA2. Added RFA decreased the thermal conductivity of thermal insulation concrete (TIC). The total shrinkage strain of RATIC increased with the increase of the replacement ratio of RFA. The 150d total shrinkage of RATIC prepared by RFA1 was 1.46 times that of TIC and the 150d total shrinkage of RATIC prepared by RFA2 was 1.23 times. The addition of GHBs led to the increase of early total shrinkage strain of concrete. Under the combined action of the higher elastic modulus of RFA2 and the pozzolanic components contained in RFA2, the total shrinkage strain of RATIC prepared by RFA2 with the same replacement ratio was smaller than that of RATIC prepared by RFA1. For example, the final total shrinkage strain of RATIC prepared by RFA2 at 100% replacement ratio was about 18.6% less than that of RATIC prepared by RFA1. A time-dependent shrinkage model considering the influence of the elastic modulus of RFA and the addition of GHB on the total shrinkage of RATIC was proposed and validated by the experimental results.

Stress-Strain Behavior of Mortar Mixtures Containing Construction and Demolition Waste as Fine Aggregate

2014 ◽  
Vol 634 ◽  
pp. 300-306 ◽  
Author(s):  
Juliana C. Ferreira ◽  
Thiago M. Grabois ◽  
Gabrielle C.S. Calcado ◽  
Romildo D. Toledo Filho
Keyword(s):  
Mechanical Response ◽  
Construction And Demolition Waste ◽  
University Hospital ◽  
Recycled Aggregate ◽  
Fine Aggregate ◽  
Demolition Waste ◽  
Stress Strain ◽  
Natural Sand ◽  
Strain Behavior ◽  
Recycled Fine Aggregate

In this paper it was investigated how the use of recycled fine aggregate influences the stress-strain behavior of mortar mixtures with different strengths. The mix design composition of the studied mortars, expressed by mass, were 1:2:0.45, 1:4:0.68 and 1:6:1.05 (cement: sand: water/cement ratio). The substitution percentages by mass of the natural aggregate by recycled aggregate were 15, 25 and 50%. The recycled aggregate had a grain size distribution comparable to that of natural sand and was obtained by grinding the waste produced by the partial demolition of UFRJ’s University Hospital. The mortars were evaluated under uniaxial compressive strength test after 28 days of curing. The results indicated that for the two higher strength classes the substitution rates affects its mechanical response by decreasing the strength. Besides, for the lower strength class the recycled aggregate could promote an increase of strength in the case of 25% of replacement.

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