Recycled Concrete Block Research Articles

Shear performance investigation of recycled concrete load-bearing blocks for sustainable masonry

PurposeRecycled concrete is an economical and environmentally friendly green material. The shear performance of recycled concrete load-bearing masonry is studied, which is great of significance for its promotion and application and also has great significance for the sustainable development of energy materials.Design/methodology/approachIn total, 30 new load-bearing block masonry samples of self-insulating recycled concrete are subjected to pure shear tests, and 42 samples are tested subjected to shear-compression composite shear tests. According to the axial design compression ratio, the test is separated into seven working conditions (0.1–0.8).FindingsAccording to the test results, the recommended formula for the average shear strength along the joint section of recycled concrete block masonry is given, which can be used as a reference for engineering design. The measured shear-compression correlation curves of recycled concrete block masonry are drawn, and the proposed limits of three shear-compression failure characteristics are given. The recommended formula for the average shear strength of masonry under the theory of shear-friction with variable friction coefficient is given, providing a valuable reference for the formulation of relevant specifications and practical engineering design.Originality/valueSimulated elastoplastic analysis and finite element modeling on the specimens are performed to verify the test results.

Leaching performance of concrete eco-blocks: Towards zero-waste in precast concrete plants

This work presents a case study of waste incorporation, where precast concrete block rejects were reincorporated into the production of new recycled concrete blocks which stands for a technically and environmentally viable alternative to natural aggregates. This study therefore evaluated the technical feasibility, first, and the leaching performance, after, of recycled vibro-compacted dry mixed concrete blocks using different percentages of substitution of recycled aggregates (RA) coming from precast concrete block rejects in order to identify those that presented a better technical performance. According to the results, concrete blocks with a 20% of RA incorporation presented an optimum physic-mechanical behaviour. The environmental evaluation based on leaching tests was carried out to identify the most conflictive elements legally regulated according to their pollutant release levels and investigate their different release mechanisms. The leaching study performed in concrete monoliths showed that in blocks with 20% of RA incorporation: Mo, Cr, and sulphate anions presented a higher mobility during the diffusion leaching tests; Sb and Cu presented an average mobility; Ba and Zn exhibited lower mobility levels and their corresponding release mechanisms for each of them. However, the limits for pollutant release in construction materials in a monolithic state were not surpassed by far.

Study on the properties variation of recycled concrete paving block containing multiple waste materials

Waste materials are widely used in concrete products, but the properties variation of concrete products containing multiple recycled materials have not been well studied. This research aims to thoroughly investigate the properties, including compressive strength, tensile splitting strength, water absorption, slip resistance and abrasion resistance of concrete paving blocks by replacing the natural aggregates with recycled concrete coarse aggregate (RCCA), crushed glass (CG), recycled concrete fine aggregate (RCFA) and ground granulated blast furnace slag (GGBS). Orthogonal experimental designs were adopted, and microstructure analyses were conducted to reveal the underlying mechanisms. Results demonstrate that RCCA significantly degraded the tensile splitting strength, water absorption, and abrasion resistance of the block containing multiple recycled materials, but CG hardly affected the tested properties. RCFA had an adverse effect on all five blocks’ properties and was proved to have a highly negative impact on blocks’ tensile splitting strength and water absorption. At an optimal replacement level, GGBS was able to improve the compressive strength, tensile splitting strength, and water absorption properties. Furthermore, not only the limit replacement levels of the waste materials in the particular block were investigated, but also two optimal replacement levels for the concrete blocks that contained multiple waste materials were tested and verified successfully: 1. 20 % for RCCA, 0 % for RCFA, and 30 % for GGBS; 2. 20 % for CG, 0 % for RCFA, and 30 % for GGBS. A series of index equations were first derived in this research, which can be used as effective methods to predict the properties of concrete blocks containing multiple waste materials in future studies.

Mechanical and Thermal Properties of RCB Masonry Containing Three Rows of Holes

In order to promote and apply the structures of the recycled concrete block (RCB) masonry, the thermal and mechanical properties of the recycled concrete specimens were tested in this study. The RCB can meet load‐bearing and seismic requirements and was prepared through experiments. Concurrently, the mechanical property experiment was conducted on the RCB masonry, and then its failure process and mode were discussed. In addition, a thermal property test was completed on the RCB wall, and the difference in the thermal properties of single‐row hole, three‐row hole, and solid blocks was analyzed by theoretical calculations. The results indicated that the mechanical properties of the RCB masonry were basically the same as those of the natural concrete block masonry, and they have good compressive stability. The calculation formulas of the compressive and shear strengths of the natural concrete block masonry are applicable to the RCB masonry. The RCB masonry containing three rows of holes owns more outstanding thermal property than natural concrete block masonry and satisfies the requirements for related codes.

Shaking table experiment of a recycled concrete block masonry building structure with a ‘self-contained’ structural system

This paper proposed a ‘self-contained’ structural system for structural columns and ring beams and used recycled concrete blocks (RCBs) as wall materials. Based on this design concept, a full-scale model of a new masonry building structure was established. The Castaic wave, the Taft wave, and an artificial wave were sequentially input to the shaking table, and the effects of different ground motions on the structural model were simulated. The changes in the natural frequency and damping ratio of the test model and the acceleration, displacement, and strain responses of the structure were studied under different seismic wave excitations. Finally, the overall seismic resistance of the model was determined. The results showed that the ‘self-contained’ structure system exhibited excellent cooperative performance. Moreover, the test model can fully meet the degree-7 seismic fortification requirements, in which the damage sustained from small earthquakes is not substantial, the damage sustained from moderate earthquakes can be repaired, and the damage sustained from large earthquakes does not cause structural failure. The results showed that RCBs can replace ordinary concrete blocks in practical engineering projects. However, the construction measures for the door and window openings should be strengthened in actual projects.

Study on Mechanical Properties of Recycled Concrete Block Mixed with Coal Gangue and Plant Fiber

In this paper, the recycled aggregates of waste coal gangue and waste concrete crushed by a crusher are used as coarse aggregates, mixed with plant fibers. By changing the mixing rate of plant fibers and coal gangue, the mix design of plant fiber recycled concrete and experiment. According to the compressive strength values of 7d, 14d and 28d concrete, the optimal mix ratio is selected. Correct the calculated value of the compressive strength bearing capacity according to the specific strength value of the plant fiber concrete and ordinary concrete obtained by the test, and obtain the correction coefficient k. According to the best mix ratio, the plant fiber recycled concrete hollow block was designed, and its compressive strength was analyzed by ANSYS finite element. In this paper, the recycled aggregates of waste coal gangue and waste concrete crushed by a crusher are used as coarse aggregates, mixed with plant fibers.

Investigation some properties of recycled lightweight concrete blocks as a fine aggregate in mortar under elevated temperature

The main objective of this study is to assess the effect of utilizing waste material (lightweight concrete blocks) as partial replacing of fine aggregate. To do so, seven mix designs were utilized to prepare 168 mortar specimens (84 cubes and 84 prism) with the replacement ratios of 10% and 20% waste material fine aggregate instead of traditional sand at different temperatures of 24 ᵒC, 200 ᵒC, 400 ᵒC, and 600 ᵒC. The combination of two type waste material together in one mixture (waste lightweight concrete blocks with waste clay bricks or waste lightweight concrete blocks with waste glass) was tested with and without fiber (1% polypropylene fiber by volume). The physico-mechanical properties of mortar specimens involving flow rate, fresh density, weight loss, compressive strength, flexural strength and water absorption were determined. The hardened tests were implemented at age of 28 days. The results demonstrated fresh density experienced a decrease when utilizing recycled materials especially waste lightweight concrete block at 20%. Compressive strength showed improving with replacing normal sand by waste materials and that enhancing was clear at high temperatures. The specimens that utilized waste lightweight concrete block with waste glass aggregate illustrated clearly reduction in water absorption comparing with control mix at different temperatures.

Sustainable Masonry Made from Recycled Aggregates: LCA Case Study

For a sustainable building industry, reusable construction with a low demand for primary resources is needed. Moreover, if we want to reduce the amount of construction and demolition waste, construction with recycled aggregate should be considered. To investigate the environmental impacts of such concrete construction, life cycle assessment (LCA) was used to compare the following types of concrete construction: Reusable blocks with recycled brick aggregate, reusable blocks with recycled concrete, reusable blocks with natural aggregate, and regular concrete wall. Firstly, the properties of new concrete with recycled aggregate were measured, such as physical, mechanical, and thermal properties. Then, different constructions were designed and assessed using the method of Institute of Environmental Sciences (CML2001) and the method of National Institute for Public Health and the Environment (ReCiPe 2016) as characterization methods. Unsurprisingly, the regular concrete wall had a higher impact on most of the impact categories, e.g., 113 kg CO2 eq. (in the first scenario, using CML2001). In accordance with the circular principles, the reusability of blocks and recycling of aggregate are the main factors that affect the environmental impact of the constructions. Thus, the global warming potential (GWP) of construction with reusable recycled concrete blocks was only 53 kg CO2 eq. (in the second scenario). Moreover, we show differences in the results of CML2001 and ReCiPe 2016, e.g., in the Photochemical Oxidant Creation category.

Experimental Investigation on Compressive Properties and Carbon Emission Assessment of Concrete Hollow Block Masonry Incorporating Recycled Concrete Aggregates

In this paper, the compressive strength experiment for three groups of recycled aggregate concrete (RAC) specimens with different replacement ratios of recycled aggregate (0%, 50%, 100%) was carried out. The mechanism of the block and mortar properties on the compressive strength of block masonry was investigated by means of a static loading test. The formula for calculating the compressive strength of a recycled concrete block was obtained based on experimental data. Moreover, the global warming potential (GWP) of recycled aggregate concrete (RAC) block masonry was evaluated by life cycle assessment (LCA) methodology. The feasibility for application of RAC block masonry was discussed combined with environmental impact data analysis. The results show that the strength of RAC blocks is the principal element affecting the compressive strength of block masonry, and the strength of mortar also has a certain impact for the compressive of RAC block masonry; the sub-coefficient of material performance should be enhancive appropriately for ensuring the construction quality of RAC block masonry; the total GWP of RAC block is lower than that of natural aggregate concrete (NAC) block. The environmental benefits of the promotion and application of RAC block masonry are inspiring.

Experimental Study on the Seismic Performance of Recycled Concrete Hollow Block Masonry Walls

This paper aims to manufacture recycled concrete hollow block (RCHB) which can be used for the masonry structure with seismic requirements. Five RCHB masonry walls were tested under cyclic loading to evaluate the effect of the axial compression stress, aspect ratio, and the materials of structural columns on the seismic performance. Based on the test results, the failure pattern, hysteresis curves, lateral drift, ductility, stiffness degradation, and the energy dissipation of the specimens were analyzed in detail. The results showed that with the increase of aspect ratios, the ductility of RCHB masonry walls increased, but the horizontal bearing capacity and energy dissipation of RCHB masonry walls decreased. With the increase of compressive stress, the bearing capacity and energy dissipation performance of RCHB masonry walls were improved, and the stiffness degraded slowly. The results also demonstrated that the RCHB masonry walls with structural columns, depending on whether the structural columns were prepared by ordinary concrete or recycled concrete, could increase the bearing capacity, ductility, and energy dissipation of specimens. The research confirmed that RCHB masonry walls could meet the seismic requirements through thoughtful design. Therefore, this study provided a new cleaner production for the utilization of construction waste resources.

Recycled concrete blocks used as coarse aggregate in the floor of rural facilities

No Brasil o descarte inadequado de resíduos da construção civil em áreas de transição entre o urbano e rural tem resultado em danos aos mananciais, sendo comum entradas e saídas de cidades e povoados rurais serem utilizados como depósitos irregulares de entulhos. Pesquisas sobre o tema “reuso de resíduos da construção” estão evidenciadas nos dias atuais visando o desenvolvimento sustentável do meio rural. Posto isto, este estudo verificou a viabilidade do uso de resíduos de blocos de concreto como agregado graúdo em novos pisos de concreto de construções rurais. Inicialmente o material reciclado foi caracterizado por sua distribuição granulométrica e massa específica. Depois elaborou-se traços de concreto, sendo o de referência (R0) sem bloco triturado, R25 (250 kg/m3 de bloco triturado), R50 (490 kg/m3 de bloco triturado) e R75 (721 kg/m3 de bloco triturado), fixando-se o volume de cimento. As amostras foram caracterizadas no estado fresco pelo ensaio de abatimento do tronco de cone e estado endurecido pelos ensaios de compressão simples e absorção de água. Ao final verificou-se que o concreto R25 têm condição de ser utilizado em pisos de instalações para produção animal, pisos para pedestres e pisos de moradias térreas, sem fins estruturais.

Analysis of the Effect of Substitution Rate on the Mechanical Properties of Recycled Concrete Hollow Block

In this paper, to study the compressive and flexural properties of recycled concrete hollow blocks, the quality substitution rate of recycled fine aggregates is taken as a variable parameter, and four kinds of substitution rates are designed, which are 0%, 30%, 60%, and 100%. At the same time, one kind of recycled coarse and fine aggregates is designed, and the quality substitution rate is 100%. 110 specimens of MU10 and MU7.5 strength grades are tested for compressive and flexural strength. The failure process and morphology of the specimens are observed to obtain compressive and flexural strength. Based on the test data, the relationship between compressive and flexural strength of recycled fine aggregates with different replacement ratios is analyzed in detail. The main findings are that experiment results show the compressive and flexural strength decrease with the increase of substitution rate of recycled fine aggregates under the same other conditions. The work of the paper is a new reform for the source of raw materials for wall materials, and it is a new way for the reuse of concrete garbage and has important environmental protection significance and engineering practical significance for building energy saving.

Reuse of construction and demolished concrete waste by producing affordable high strength concrete block

The issue of achieving sustainable environment is highlighted in different national and international strategic documents, such as Rwanda Viosion 2020, EDPRS II and MDGs. Rwanda on its track towards achieving sustainable environment, is still experiencing some challenges like Environmental degradation for the search of aggregates, energy for extraction of natural aggregates and difficulties in finding dumping sites for demolitions and construction wastes. Therefore, all those problems have created the need for developing a new source of construction materials.The idea of recycling of C&D concrete wastes aims at finding solution to the environment degradation caused by damped demolished wastes as well as producing affordable high strength concrete blocks. This research investigated the availability of C&D concrete wastes and it was discovered that up to 33.33% of C&D waste came from concrete structures while more than 23.75% of people confirmed to have been involved in demolition works more than three times a year.The research was done by collecting sample composed of C&D concrete wastes at construction site of BPR headquarter where they demolished the existed building for construction of a new multistory building in kigali city and the sample was crushed, batched and mixed with a proportion of 1:3 and 1:5 as stated by Rwanda Bureau of Standards and manufactured new concrete blocks. The research performed on series of concrete blocks: 2 series each made of different proportions of cement for recycled concrete blocks, and one serie of reference blocks made of natural aggregates. Compressive strength test gave an average of 5.13N/mm2 for recycled concrete block, which fulfills requirement of Rwanda Bureau of standards for hollow concrete blocks and which is 0.87 times the compressive strength of an ordinary block tested under same conditions. Finally, the cost effectiveness showed that the new recycled concrete block will be affordable by reducing at 15.6% of cost for that one made of natural aggregates.Keywords: Concrete wastes, Recycled concrete block, Mechanical properties, Cost effectiveness and Environmental protection

The Experimental Study on the Frost Resistance of Different Recycled Coarse Aggregate Replacement Rate of Recycled Concrete

The different recycled coarse aggregate replacement rate of recycled concrete blocks are exposed to different times of freeze-thaw cycles in fresh water and concentration of 3.5% sodium chloride solution respectively, then the loss of mass and relative dynamic modulus are calculated. The influences of recycled coarse aggregate replacement rate of recycled concrete on the frost resistance are analysed. The research results show that the frost resistance of recycled concrete in the replacement rate of 30% performs the worst, and the effect of freezing thawing in sodium chloride solution on the performance of recycled concrete is worse than that in fresh water.

Experimental study on shear behaviour of recycled concrete hollow block masonry

To study the shear behavior of recycled concrete block masonry with three rows of holes, the experiments were carried out on the type 240 specimens. The results showed that the shear damage mode of recycled concrete block masonry was brittle failure; the majority of destroy was double shear; the shear pin could greatly improve the shear strength; the influences of block type and intensity level on shear strength were small; the shear strength was mainly determined by the strength of mortar, and the shear strength increased with the increasing of the strength of mortar. The influence of difference of block material on the shear strength coefficient of variation was small, but the coefficient of variation was easily influenced by the water absorption, the construction quality. Considering the influence of the construction quality, the expressions on shear strength average value, standard value and design value were modified.

Study on thermal properties of recycled aggregate concrete and recycled concrete blocks

This paper investigated the thermal properties of recycled aggregate concrete (RAC) and recycled concrete block. Considering the effect of four factors, an orthogonal test was conducted to study the thermal conductivity of RAC. The thermal conductivities of large particle recycled aggregate concrete (LRC) and recycled brick concrete (RbC) were also tested at different replacement ratio of recycled aggregate. By defining an influence coefficient c, the effect of recycled concrete aggregate (RCA) on thermal conductivity of RAC was better explained. A modified formula was also proposed to calculate the thermal conductivity of RAC based on that of normal concrete. The thermal resistance of recycled concrete block was calculated, and an experiment on the heat transfer coefficient of recycled concrete block wall in practical engineering was conducted. The study shows that the recycled coarse aggregate has the greatest influence on thermal conductivity of RAC. There is a significant linear relationship between the influence coefficient c and the thermal conductivity of RAC. The results calculated from modified formula for thermal conductivity of RAC agreed basically with the test results.

Development of Load-Bearing Thermal Insulation Recycled Concrete Block and Research on its Thermal Performance

A new kind of 310mm thick load-bearing thermal insulation block utilizing construction waste as coarse aggregate was developed and produced. Internal thermal bridge is reduced by special design of holes pattern and cut off by mal-posed thermal insulation layer arrangement. By testing heat transfer coefficient of four kinds of masonry walls, different aggregate type, masonry unit type and insulation material which affect thermal performance of masonry were studied. Results show that heat transfer coefficient of walls with recycled aggregates is lower than that with natural aggregates under the same condition. By filling thermal insulation material in block holes, heat transfer coefficient is dramatically lowered. Among four types of masonry walls, heat transfer coefficient of 310mm thick load-bearing block wall with recycled aggregate is the lowest, and its thermal insulation performance is the best.

Low Cycle Test Research on Seismic Performance of Recycled Concrete Block Wall

The use of concrete aggregate from earthquake damaged building to make blocks which needed for post-disaster reconstruction has brought the social, environmental, economic and other benefits, at the same time respond to the basic state policy of low carbon energy saving. At home and abroad currently focused on the materials properties of recycled aggregate and recycled concrete block basic physical mechanics to study, but research for the material block wall structure performance is less, the research for the wall shear strength and anti-seismic performance of this kind of wall is of great significance. Based on the recycled concrete aggregate from Mianyang, Sichuan where is disaster area to make three hole hollow block wall (no reinforcement) to perform low cycle experiment, collecting four samples, and achieved anti-seismic indicators such as the hysteresis curves, skeleton curves of recycled concrete block wall, analyzes the influence of the axial pressure, the loading method on seismic performance of block wall.

Study on the Basic Mechanical Properties of Recycled Concrete Hollow Block Masonry

By the experimental studying on the basic mechanical properties of recycled concrete hollow block masonry, the compressive and shear behavior of recycled aggregate concrete hollow block masonry under different mortar strength were analyzed. Research indicated that the compressive and shear behavior of recycled aggregate concrete hollow block masonry was similar to that of ordinary concrete hollow block masonry. The normal formula was recommended to calculate the compressive strength of the masonry. The shear strength of the masonry was affected by the mortar strength. The shear strength calculation formula of recycled concrete hollow block masonry was proposed according to the formula of masonry design code. The calculating results were in good agreement with the test results.

Orthogonal Design Choices Recycled Concrete Load-Bearing Hollow Block

Study four factors - water consumption , water-cement ratio , recycled fine aggregate replacement ratio of recycled coarse aggregate replacement rate - affect the regularity of the load-bearing hollow block compressive strength of recycled concrete by orthogonal test method , the test showed that , water consumption factors affect the compressive strength of recycled concrete block design with than the emphasis on the control of water consumption . Under the test conditions , the optimum mixture ratio of recycled concrete load-bearing block : water consumption of 160 kg / m 3 , the water cement ratio 0.45 , recycled fine aggregate replacement ratio of 30% recycled coarse aggregate replacement ratio of 30% .