Percentage Of Recycled Concrete Aggregate Research Articles

Analysing the Influence of Recycled Concrete Aggregate and Expanded Perlite on Mortar Performance

With population growth and rapid urbanisation leading to excessive waste generation in the construction sector and the scarcity of natural resources, such as natural fine aggregates, the demand for recycled alternatives has increased. In exploring the potential of recycled materials for construction materials, the present study investigated the performance of recycled concrete aggregate (RCA) and expanded perlite in mortar as a partial replacement for fine aggregates. Different percentages of RCA and expanded perlite were used. A consistent percentage of perlite was used: 0%, 10%, 15%, 20%, 25%, 30% and 35%. The RCA and expanded perlite were then mixed with other materials such as cement, water and fine aggregate. Flowability, compressive strength and flexural strength tests were carried out. It was found that a 90% replacement of RCA for each increasing percentage of perlite in the mortar mix resulted in a significant reduction in flow diameter. The compressive and flexural strength of the mortar increased with age. However, the flexural strength of the control mortar, which contained neither RCA nor perlite, consistently exceeded that of the mortar with these additives. The results provide valuable insights for the production of new materials in the construction industry, for waste management and for lightweight yet durable construction solutions.

Fatigue and stiffness characteristics of asphalt mixtures made of recycled aggregates

This research studies the stiffness characteristics and fatigue life of several asphalt mixtures made of recycled glass, reclaimed asphalt pavement (RAP), and recycled concrete aggregate (RCA). Experiments were carried out at 5–35 °C, loading frequencies of 0.1–20 Hz, and at two microstrain levels of 200 and 400 µm/m. To date, the effect of extensive parametric combinations of loadings, microstrain levels, and temperatures on asphalt mixtures made entirely of recycled materials (RM) has not been undertaken. The findings exhibited superior stiffness characteristics and improved fatigue life of some RM mixtures compared to control mixtures. The next step of this study included the optimization of three existing fatigue life prediction models. In addition, a prediction model was developed based on nominal maximum aggregate size (NMAS), percentage of RCA, and percentage of RAP in the asphalt mixture. The optimized models resulted in a much higher coefficient of determination (R2) and P-value (likelihood) in the statistical T-test compared to the existing prediction models utilized in this study. The developed model yielded R2 values close to 0.99 between measured and predicted fatigue life, indicating an enhanced accuracy in the prediction. Comparison of the estimated dissipation energy of mixtures supported and validated the fatigue testing outcomes.

PREDICTION OF THE COMPRESSIVE STRENGTH OF ENVIRONMENTALLY FRIENDLY CONCRETE USING ARTIFICIAL NEURAL NETWORK

The paper evaluated the possibility of using artificial neural network models for predicting the compressive strength (Fc) of concretes with the addition of recycled concrete aggregate (RCA). The artificial neural network (ANN) approaches were used for three variable processes modeling (cement content in the range of 250 to 400 kg/m3, percentage of recycled concrete aggregate from 25% to 100% and the ratios of water contents 0.45 to 0.6). The results indicate that the compressive strength of recycled concrete at 3, 7 and 28 days is strongly influenced by the cement content, %RCA and the ratios of water contents. It is found that the compressive strength at 3, 7 and 28 days decreases when increasing RCA from 25% to 100%. The obtained MLP and RBF networks are characterized by satisfactory capacity for prediction of the compressive strength of concretes with recycled concrete aggregate (RCA) addition. The results in statistical terms; correlation coefficient (R) reveals that the both ANN approaches are powerful tools for the prediction of the compressive strength.

An Experimental Study of Granular Material Using Recycled Concrete Waste for Pavement Roadbed Construction

Rapid worldwide urbanization and drastic population growth have increased the demand for new road construction, which will cause a substantial amount of natural resources such as aggregates to be consumed. The use of recycled concrete aggregate could be one of the possible ways to offset the aggregate shortage problem and reduce environmental pollution. This paper reports an experimental study of unbound granular material using recycled concrete aggregate for pavement subbase construction. Five percentages of recycled concrete aggregate obtained from two different sources with an originally designed compressive strength of 20–30 MPa as well as 31–40 MPa at three particle size levels, i.e., coarse, fine, and extra fine, were tested for their properties, i.e., the optimum moisture content density, Californian bearing ratio, and resilient modulus. A characterization of the resilient modulus of the mixes under complex stress conditions was performed. The characterized modulus model was used in the nonlinear analysis of the pavement structure under traffic loading using KENALYER software. Consequently, the two critical responses, i.e., the tensile strain at the bottom of the asphalt layer and the vertical compressive strain at the top of the subgrade, were computed and compared for the pavement structures with varying types and percentages of recycled concrete aggregate used in the subbase layer.

Structured soil mixture for solving deformation issue in GeoBarrier System

The GeoBarrier System (GBS) is designed to improve the urban sustainability with the planting bags within it. The GeoBarrier System (GBS) is a man-made 3-layered cover system comprising an exposed vegetative layer combined with hidden 2-layered unsaturated covered system, which harnesses the distinct difference in unsaturated hydraulic properties between a non-cohesive fine-grained layer and a coarse-grained layer. Previous research works indicated that GBS could be used as an earth retaining structure and slope stabilization system against rainfall-induced slope failures. However, the differential settlement was observed along the approved soil mixture (ASM) geobag layers in the previous study. The objective of this project is to investigate the appropriate modification of ASM layers in order to reduce the deformation of planting GeoBags. The research works involved the mixing of ASM with different percentages of recycled concrete aggregate (RCA) (called structured soil mixture or SSM) to improve the modulus elasticity of ASM layer within the planting geobag. The scope of this study includes the laboratory experiments for saturated and unsaturated soil characterization, numerical analyses and loading tests. The results indicated that the soil mixture with a ratio of 50% ASM and 50% coarse RCA can be used to provide improved resistance to deformation of GBS.

Comparative life cycle assessment of warm mix asphalt with recycled concrete aggregates: A Colombian case study

Abstract This paper presents the results of a comparative life cycle assessment undertaken to compare the potential environmental impacts associated with the use of Recycled Concrete Aggregate (RCA) as a partial replacement of natural aggregates in the production of Warm Mix Asphalt (WMA), with those of a conventional Hot Mix Asphalt (HMA). Laboratory testing results were used as inputs in a pavement design software with the purpose of designing several pavement structures with different percentages of RCA and according to the typical Colombian pavement design conditions. Primary data was collected from several companies in the northern region of Colombia. The SimaPro 8.4.0 software was used for modeling the processes analyzed in the case study and all the life cycle inputs and outputs related to the functional unit were characterized during the life cycle impact assessment (LCIA) phase into potential impacts according to the impact assessment methodology TRACI v.2.1. The LCIA results of the case study showed that the use of WMA with RCA as a replacement of coarse natural aggregates leads to a deterioration of the environmental profile of the pavement structures.

Bond Strength of HYSD Bars and SCC with and without Recycled Aggregate-An Experimental Study

Self Compacting Concrete (SCC) has become inevitable in the current scenario of construction of large and complex structures with heavy reinforcement and complicated shapes. Using normal concrete in such situation may often result in inadequate compaction, affecting performance and long-term durability of structures. In addition, the use of Recycled Concrete Aggregate (RCA) is gaining importance throughout the globe due to the depleting sources of natural aggregate and disposal problem of demolished waste. There is a little work done on the behaviour of SCC with RCA. Therefore, a comprehensive experimental investigation on bond strength and modes of failure of Self Compacting Concrete (SCC) with and without Recycled Concrete Aggregate (RCA) was carried out and the results are presented. The variables studied include grade of concrete (M20, M40 and M60), Percentage of RCA (0% to 100%), diameter of bar (10, 12 and 16) and percentage embedment length. All specimens were tested by conducting pull out test on UTM after 28 days of curing. The bond strength was found to vary with the increase in diameter and the failure mode was observed to change from rod pull out to splitting or rod fracture with increase in percentage of embedment length. The experimental results were compared with the theoretical bond strengths using the authors’ formula and the formulae suggested by earlier researchers.

Self-consolidating concrete using recycled concrete aggregate and high volume of fly ash, and slag

This paper studies the effect of using recycled concrete aggregate (RCA) on the properties of self-consolidating concrete (SCC). Twenty concrete mixtures with different mixtures of fly ash (FA), slag (S) and RCA were developed and tested. The mixtures were sorted into five categories, with constant water to cementitious materials (w/c) ratio of 0.38, based on their RCA content: 0, 25, 50, 75, and 100% of natural coarse aggregate (NCA) replaced by RCA. The results showed that as the percentage of RCA (0–100%) has increased in the mixes replacing NCA; the compressive strengths of the concrete mixes has decreased at 3, 14, and 28days, and the tensile strengths decreased at 28days. Moreover, the partial replacement of cement by (SCMs) had an adverse effect on the 28-days-compressive strength; however, it increased the resistance to chloride permeability. Moreover, several mixes have met the minimum Illinois Department of Transportation compressive strength requirements.

Optimization and influence of parameter affecting the compressive strength of geopolymer concrete containing recycled concrete aggregate: using full factorial design approach

There are several parameters that influence the properties of geopolymer concrete, which contains recycled concrete aggregate as the coarse aggregate. In the present study, the vital parameters affecting the compressive strength of geopolymer concrete containing recycled concrete aggregate are analyzedby varying four parameters with two levels using full factorial design in statistical software Minitab® 17. The objective of the present work is to gain an idea on the optimization, main parameter effects, their interactions and the predicted response of the model generated using factorial design. The parameters such as molarity of sodium hydroxide (8M and 12M), curing time (6hrs and 24 hrs), curing temperature (60°C and 90°C) and percentage of recycled concrete aggregate (0% and 100%) are considered. The results show that the curing time, molarity of sodium hydroxide and curing temperature were the orderly significant parameters and the percentage of Recycled concrete aggregate (RCA) was statistically insignificant in the production of geopolymer concrete. Thus, it may be noticeable that the RCA content had negligible effect on the compressive strength of geopolymer concrete. The expected responses from the generated model showed a satisfactory and rational agreement to the experimental data with the R2 value of 97.70%. Thus, geopolymer concrete comprising recycled concrete aggregate can solve the major social and environmental concerns such as the depletion of the naturally available aggregate sources and disposal of construction and demolition waste into the landfill.

SELF COMPACTING CONCRETE (SCC) AS GREEN CONCRETE WITH RECYCLED CONCRETE AGGREGATES (RCA) – AN EXPERIMENTAL STUDY

The construction industry has become one of the main sources of environmental pollution due to the emission of carbon monoxide and other pollutants during the production of construction materials and operation of construction equipment. Self-compacting concrete (SCC) provides a healthier working environment by avoiding noise pollution, emission of smoke and vibrations during construction. Also, the depleting sources of natural aggregate (NA) and disposal problem of demolished waste have prompted the researchers to take up studies& investigations on the use of Recycled Concrete Aggregate (RCA) in structural concrete. Thus, SCC with RCA has more significant environmental related advantages in comparison to the vibrated concrete. This paper presents experimental results of investigations carried out on SCC of grade M20 with RCA designed on the basis of modified NAN-SU mix design and the workability tests performed in this research were as per The European (EFNARC) Guidelines for Self Compacting Concrete (SCC) Specification to arrive at the SCC mix proportions. Workability and hardened state properties of Self-compacting concrete (SCC) with various percentages of RCA as partial replacement of natural aggregates (NA) (0%, 25%, 50% 75% & 100%) were studied. The results have indicated that the natural aggregate can be replaced completely with the RCA for low strength concrete with more or less 10% deviation in strength which can be compensated by proper designing of mix.

Evaluating Recycled Concrete Aggregate as Hot Mix Asphalt Aggregate

Abstract The use of recycled concrete aggregate (RCA) in asphalt mix is a sustainable construction practice, provided that the addition of RCA does not adversely affect the performance of the asphalt mix. In this study, the effects of RCA on the performance behavior of hot mix asphalt (HMA) were examined. The mixes were produced by blending RCA with virgin aggregate at six different percentages (0 %, 20 %, 40 %, 60 %, 80 %, and 100 %). The mix design results indicate that the RCA is highly absorptive, and that as the percentage of RCA in the mix increases, the optimum asphalt content increases significantly. In terms of performance behavior, the addition of RCA to the HMA mix reduced the modulus, resistance to rutting, fatigue, thermal cracking, and resistance to moisture damage of the asphalt mix. Considering the performance behavior and the need for a higher asphalt content, the use of RCA as HMA aggregate is not recommended, even though all the RCA mixes met the volumetric requirements. More important, the findings in this study indicate that the absorbed asphalt might play a significant role at high temperatures, likely because of expansion of the asphalt.

Experimental Investigation on Recycled Aggregate as Partial Replacement on Natural Aggregate

In construction industry and in urban areas, many concrete structures like buildings, bridges and roads are razed after a period of time into their service life for purpose of replacement and also due to natural disasters like earthquakes, cyclones and man made disasters like war and bombing. Due to increasing construction activities and infrastructure development works the sources of basic construction materials are depleting. It is becoming increasingly difficult to obtain good quality aggregate at reasonable prize. The increase in cost is mainly due to the cost of transportation and availability of only few quarries. Considering the present situation one of the alternate solutions would be to reuse the demolished concrete. This work deals with an experimental investigation on the effectiveness of replacement of natural aggregates by recycled aggregates in different percentages like 0%, 5%, 15%, 25%, 35%, 45%, 55%, 65%, 75%, 85% and 95% on the strength characteristics of concrete. Experiments were carried out to determine compressive uplifting tensile and flexural strength of concrete with different percentage of recycled concrete aggregate and to compare them with those of concrete made with conventional course aggregate.