IMPROVING THERMAL AND MECHANIC PERFORMANCE OF SUSTAINABLE LIGHTWEIGHT CONCRETE FACADE PANELS IN TERMS OF AGGREGATE TYPE

Durability properties evaluation of self-compacting concrete prepared with waste fine and coarse recycled concrete aggregates

Treated recycled coarse aggregate concrete: A new mixture proportioning method based on packing densities

The construction industry is showing an increasing interest in the integration of Recycled Aggregate (RA) into concrete as a substitute for natural coarse aggregate, whether in full or in part, with the aim of reducing dependence on virgin aggregate. This shift seeks to alleviate the environmental impact associated with the extraction of aggregates from natural resources and address the environmental challenges related to concrete waste. However, there is limited research on concurrently replacing both natural fine and coarse aggregate in concrete. This study investigates the effects of substituting natural aggregates with recycled aggregate concrete, specifically using 100% recycled coarse aggregate in combination with 10% recycled fine aggregate, and further examines the influence of steel fibres on the resulting mix. Replacing natural aggregates with recycled aggregates (100% coarse, 10% fine) leads to an increase in slump value, indicating enhanced workability. However, the addition of steel fibres reduces the slump by 21.12% to 33.33%, reflecting the impact of fibre reinforcement on the mix’s flow characteristics. Mechanical testing reveals that the use of recycled aggregates alone generally reduces concrete strength. Specifically, the replacement leads to reductions in compressive strength, split tensile strength, and flexural strength by 48.19%, 76.53%, and 71.96%, respectively, at 28 days. Importantly, incorporating steel fibres into the recycled aggregate concrete mitigates this strength loss, enhancing compressive strength, split tensile strength, and flexural strength by 16.51%, 6.12%, and 7.55% at the 28-day. These findings demonstrate that steel fibres effectively reinforce recycled aggregate concrete, compensating for strength reductions and improving overall performance.

With diminishing natural aggregate resources and increasing environmental protection efforts, the use of recycled fine aggregate is a more sustainable approach, although challenges persist in achieving comparable mechanical properties. Exploration into the incorporation of steel fibers with recycled aggregate has led to the development of steel-fiber-reinforced recycled aggregate concrete. This study investigates the shrinkage performance and compressive constitutive relationship of steel fiber recycled concrete with different steel fibers and recycled aggregate dosages. Initially, based on different replacement rates of recycled coarse aggregate and different volume contents of steel fiber, experimental results demonstrate that as the replacement rate of recycled coarse aggregate increases, shrinkage also increases, while the addition of steel fiber can mitigate this effect. An empirical shrinkage model for steel fiber recycled concrete under natural curing conditions is also proposed. Subsequently, based on the uniaxial compression test, findings indicate that with an increasing replacement rate of recycled fine aggregate, the peak stress and elastic modulus of concrete decrease, accompanied by an increase in peak strain, and the addition of steel fiber limits concrete crack development and enhances its brittleness while the peak stress and strain of recycled fine aggregate concrete are enhanced. However, the steel fiber volume percentage has a negligible effect on the elastic modulus. A constitutive relationship for concrete considering the effects of recycled fine aggregate and steel fiber is also proposed. This finding provides foundational support for the influence patterns of steel fiber dosage and recycled aggregate ratio on the mechanical properties of steel fiber recycled concrete.

An excessive extraction of natural resources for aggregate in concrete mix can caused an environmental degradation.  According to Indonesia ministry of industry in 2017, the use of cement is predicted will reach 84,96 million tons, that can affected the use of aggregate for concrete mix are quadruplet to 250 – 350 million tons. Opimally, the use of recycled material is green method that can reduce an excessive extraction of natural aggregates and keep an environmental sustain. The aim of this study is to obtain recycled aggregate concrete compressive strength and examine recycled aggregate concrete quality in days 3, 7, 28, 35, and 90 along with a proposal of the use of recycled aggregate concrete as a building construction material. This research used experimental method of SNI 03-2834-2002 the standard of normal concrete mix design for f’c 25 MPa then built five types of concrete mix of REC B, REC C, REC D, REC E, and REC F with every types of concrete has four sample are used for compressive strength test. The fine recycled paving block aggregate (RPA) were used partially to substituted a fine recycled brick aggregate (RBA) at 0%, 25%, 50%, 75%, and 100% by weigth. The result of this study showed the mixed concrete REC D with RCA 100%, RPA 50% and RBA 50% in 28 days is generate highest compressive strength than other recycle aggregates concrete mixes. Compressive strength at 28 days in a mix codes REC B, REC C, REC D, REC E and REC F are 18,12 MPa; 18,36 MPa; 19,35 MPa;16,69 MPa; and 16,39 MPa. The results show that it is feasible to replace a natural aggregate entirely by recycled aggregates. With compressive strength over 17 MPa at 28 days, mix codes REC B, REC C and REC D are recommended to use the recycled aggregate concrete for structure of residential buildings but mix codes REC E and REC F aren’t recommended and only allowed for non-structural concrete such as separate wall (SNI 8140:2016). Based on SNI 03-0691-1996 about solid brick concrete (paving block), recycle aggregate concrete with mix code of REC B, REC C, and REC D are able to use on paving block with B quality such as parking lot. While, recycled aggregate concrete with mix code of REC E and REC F are able to use on paving block with C and D quality which used for pedestrian, garden and other use.Â

The properties of recycled fine aggregate(RFA) from waste recycled aggregate concrete (RAC) were determined. In this study, five series of parental concrete mixtures using natural coarse and fine aggregates were prepared, which had the same target slump value from 35mm to 50mm and different compressive strengths ranging from 25MPa to 60 MPa. These concretes were used as recycled aggregates to prepare RACs with a compressive target strength of 30MPa. After that, these RACs were used as secondly recycled aggregates to produce RACs with the same compressive target strength of 30MPa. The physical properties of RFAs including apparent density, compacted bulk density and water absorption were tested. At the same time, fineness modulus of natural fine aggregates and RAFs were calculated and their mineral compositions were analyzed. The results showed that RAFs from waste RACs were not adequate to structural concrete alone because they belonged to coarse tape and their mineral compositions were adverse to the best growth of strength of RACs.

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.

Properties of self-compacting concrete prepared with coarse and fine recycled concrete aggregates

One-third of the total waste generated in the world is construction and demolition waste. Reducing the life cycle of building materials includes increasing their recycling and reuse by using recycled aggregates. By preventing, the need to open new aggregate quarries and reducing the amount of construction waste dumped into landfills, the use of recycled concrete aggregate in drum compacted concrete protects the environment. Four samples of PRCC were prepared for testing (compressive strength, tensile strength, flexural strength, density, water absorption, porosity) as the reference mix and (10, 15, and 20%) of fine recycled concrete aggregate as a partial replacement for fine natural aggregate by volume. The mix is designed according to (ACI 327-15) with the specified cylinder compressive strength (28 MPa). The results showed a decrease in mechanical properties with an increase in partial replacement compared to the reference mixture and an increase in water absorption and porosity at 28 days. This is because old cement mortar on the surfaces of fine recycled concrete aggregates leads to higher porosity and water absorption than fine natural aggregates. At 90 days, results improved slightly. This is due to the non-aqueous cement in the recycled fine concrete aggregate.

Concrete based on recycled aggregates – Recycling and environmental analysis: A case study of paris’ region

Influence of rice husk–bark ash on mechanical properties of concrete containing high amount of recycled aggregates

A large amount of waste concrete generates an environmental problem due to demolition of old concrete structures. To solve this problem, it is necessary to collect recycled aggregate from waste concrete. The conventional recycling technique of recycled aggregate from waste concrete does not indicate a significant quality to be re-used for making a new concrete. We proposed new techniques to produce high grade recycled aggregate by heating-grinding (H-G) method and heating-grinding-acid (H-G-A) method. To ensure the quality of the concrete made from recycled coarse aggregate concrete, the non-destructive evaluation was conducted in this research. High grade recycled aggregate concrete were prepared in advanced using two methods mentioned earlier. Then, new concrete specimens were produced using those types of recycled aggregate concrete. After 28 days curing time, rebound hammer test and ultrasonic pulse velocity test were performed on recycled coarse aggregate concrete to examine the surface hardness and ultrasonic wave velocity of the concrete. Almost similar quality to natural coarse aggregate in terms of density, water absorption, sieve analysis achieved by both H-G recycled coarse aggregate and H-G-A recycled coarse aggregate. However, the surface hardness and ultrasonic wave velocity of H-G-A recycled coarse aggregate concrete is better than those of H-G recycled coarse aggregate concrete. That acid solvent enables to dismantle the cement paste from aggregate surface more effectively, so this types of recycled aggregate shows a better performance than the other one. Continued delamination reduces pores in the interfacial transition zone resulting better bonding mechanism between new cement paste and recycled aggregate surface.

A systematic comparison of performance of recycled concrete fine aggregates with other alternative fine aggregates: An approach to find a sustainable alternative to river sand

The original concrete to be used for the production of recycled aggregate is basically composed of the original aggregate and the original mortar, and, if the original aggregate has sound properties, the quality of the recycled aggregate depends on the property of the original mortar to a large extent. In addition, it is said that the degree of deterioration in the quality of the recycled fine aggregate is larger than that of the recycled coarse aggregate. Therefore, when the recycled fine aggregate or the concrete prepared using it is applied to the structural concrete, it becomes imperative to make a proper estimation of the effects of the properties of the original mortar as to their qualities prior to setting various mix design conditions. From this point of view, this paper presents a series of experiments which analyze recycled fine aggregate and recycled aggregate concrete as given below. 1. 12 types of original concrete were prepared using 3 types of original aggregate having different strengths, shapes and surface characteristics, and changing the water-cement ratio of the original mortar in 4 levels of 35%, 45%, 55% and 65%, respectively. Then, 16 types ofrecycled fine aggregate were made by manufacturing the prepared original concrete using 2 types of crushing methods. 2. The amounts of the original mortar contained in 16 types of recycled fine aggregate were estimated, and the tests on their various physical properties were carried out to clarify the relationship between them. 3. From among the above-mentioned 16 types of recycled fine aggregate, 6 types, which were made using the same type of original aggregate and the original mortar of different strengths, and by different methods to crush the original concrete, were selected. Using these 6 types of recycled fine aggregate, 48 types of recycled concrete having a different replacement ratio of recycled fine aggregate and a different water-cement ratio of concrete were produced to investigate the effects of the amount of the original mortar contained in each recycled fine aggregate and its properties on the quality of the recycled aggregate concrete. Much valuable information regarding useful results pertaining to the mix design of the recycled aggregate concrete to be produced using the recycled fine aggregate was obtained through these experiments and the analysis described above.

Creep model of concrete with recycled coarse and fine aggregates that accounts for creep development trend difference between recycled and natural aggregate concrete