Partial Replacement Of Natural Aggregate Research Articles

Concrete manufactured with crushed asphalt as partial replacement of natural aggregates

The paper focuses on the reuse of crushed asphalt (GA) as a partial replacement (up to 20%) of natural aggregates for concrete manufacture. Addition of GA aggregates produced a positive effect on workability loss. The GA mixes, however, showed a significant tendency to bleed and segregate at the highest replacement percentage applied. GA led to a decrease of compressive strength in concrete (with respect to that of the reference concrete) up to 50% due to the weakness of the cement paste / recycled aggregate interface. To compensate for this negative effect, a reduction of w/c for the GA concretes was necessary. A decrease of w/c allowed the GA concretes to show drying shrinkage values substantially similar to those of reference concrete with the same cement factor. The experimental results confirmed the possibility of partial substitution (max. 15%) of natural aggregates with crushed asphalt for making concrete.

Electric arc furnace granulated slag for sustainable concrete

This paper deals with the use of industrial by-products from electric arc furnace (EAF) granulated slag for the partial replacement of natural aggregates commonly used to manufacture concrete. Three different gradings of EAF granulated slag were considered. The rheological and mechanical properties of concrete manufactured with a partial replacement of natural aggregates with slag were determined. Dry shrinkage of hardened concrete was evaluated. Results indicated that the maximum percentage of natural aggregate that can be replaced with EAF granulated slag is about 15% in order to limit the superplasticizer dosage required to attain the same workability class of the reference concrete mix at the end of the mixing procedure. The higher the percentage of granulated slag was, the higher the density, the elastic modulus in compression and the compressive strength of the concrete were. Dry shrinkage of the concrete increased by adding a greater amount of EAF granulated slag.

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EXPERIMENTAL RESEARCH OF PRECAST CONCRETE FLOOR BLOCKS WITH IMPROVED RESISTANCE TO HIGH TEMPERATURE

The paper presents possibility of usage of crushed clay bricks and roof tiles as an aggregate for concrete in precast concrete floor blocks. According to literature review, concrete with crushed brick and roof tiles as an aggregate has better thermal properties than regular concrete with natural aggregate. Applicability of concrete mixture for precast concrete blocks was tested regarding the requirements set in HRN EN 15037-2 Precast Concrete products – Beam and block floor systems – Part 2: Concrete blocks. Precast concrete blocks with crushed bricks and roof tiles were made and their mechanical properties after exposure to high temperature were tested. Based on experimental results, conclusions are made about usage of crushed bricks and roof tiles as partial replacement of natural aggregate in concrete for precast concrete blocks with improved resistance to high temperatures.

Properties of Concrete with Partial Replacement of Natural Aggregate by Recycled Concrete Aggregates from Precast Production

Recycled concrete aggregates (RCA) can be used as a replacement of natural aggregates for a concrete production to save natural sources and also to decrease amount of demolition waste which has to be landfilled. Precast production generates some percentage of defected elements which are carted off and recycled with other demolition waste. In this study defected elements are separately recycled into RCA with beneficial properties and used directly into new mixtures for precast elements. Results from testing of RCA and application into new concrete mixtures are presented. It was proved that the replacement of raw aggregates by RCA up to 20% has no negative influence on physico-mechanical properties of concrete.

Influence of Incorporating Construction Building Demolition as Recycled Aggregate on Concrete Behavior

Because of increasing waste production and public concerns about the environment, it is desirable to recycle materials from construction and building demolition. This study aimed to find a technique for producing recycled aggregate concrete obtained from construction and building demolition waste. Laboratory trials were conducted to investigate the possibility of using recycled aggregate from different sources in Iraq, as a partial replacement of both coarse and fine natural aggregates or one of them. Recycled aggregate consists of crushed concrete (CC) or acombination of crushed brick (CB) and crushed concrete (CC). The aggregate in concrete was replaced with 10%, 20%, 30% and 50% by weight of crushedconcrete (CC) or crushed brick (CB) and crushed concrete CC. Some of mechanical properties of recycled aggregate concrete as compared to those of conventional normal aggregate concrete are studied. Compressive strength and the splitting tensile strength were determined after curing for 7, 28, and 90 days while density was determined after28 days.From these results, it is reasonable to assume that the use of recycled concrete aggregate does not jeopardize the mechanical properties of concretefor replacement ratios up to 50%. The concrete prepared with the crushed concrete only as a partial replacement of natural aggregate achieved the highest strength values at 7, 28and 90 days. The results suggested that an aggregate that contains 50% recycled aggregate is optimum for producing recycled aggregate concrete The test results showed that the replacement of coarse or fine natural aggregate by recycled brick aggregate at the levels of 10,20,30 and 50% had little effect on the compressive strength of the specimens.

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.

Electric arc furnace slag as natural aggregate replacement in concrete production

Recycled materials in the building industry represent an attractive alternative to the consumption of natural resources. The paper shows results obtained by adding electric arc furnace slag (EAFs) as partial replacement of natural aggregates in concrete production. EAFs determines a significant increase in the compressive strength of concrete while it does not seem to affect the bending strength and drying shrinkage of cement mixtures. The concrete durability was approached by a careful chemical analysis and microstructural investigation of EAFs. The tendency to deteriorate seems negligible due to a low presence of amorphous and expansive compounds leading to an increase in volume. Moreover, the metals released, compared with the national legislation requirements, meet environmental standards.

Laboratory investigation of carbonated BOF slag used as partial replacement of natural aggregate in cement mortars

Direct mineral carbonation produces a material rich in carbonates and with reduced quantities of free oxides. The aim of this work was to show that such materials can be used in the construction domain. Basic Oxygen Furnace (BOF) slag from the steelmaking process has been traditionally seen as unfit for bounded applications due to its propensity to swelling, resulting from hydration of its high free lime content. Here, BOF slag was crushed to suitable particle sizes, carbonated in an aqueous solution of carbonic acid, and utilized to replace 50% of natural sand aggregate in cement mortars. The mechanical and chemical properties of these mortars were compared to mortars containing non-carbonated slags, and a standard cement mortar as a reference. Tests were conducted to determine mortar paste consistency and soundness, and cured mortar compressive strength and leaching tendencies. The results showed a satisfactory performance for all considered aspects (comparable with the reference) of the mortar sample containing 37.5 wt% (1.5 in 4 parts solids) carbonated BOF slag of <0.5 mm particle size.

Recycled aggregate concrete for nearly zero-energy buildings

This paper examines the possibility of using crushed brick and recycled concrete as a partial replacement of natural aggregates in a production of prefabricated wall panels used for constructing nearly zero-energy buildings. Replacement ratios of natural aggregates by 40%, 50% and 60% were investigated. Mechanical, durability and thermal properties of recycled aggregate concrete were tested. The test results indicate the possibility of manufacturing concrete with recycled concrete aggregates and recycled brick aggregates, which can find wide use in the building construction process. In addition, energy efficiency and sustainability parameters of recycled aggregate concrete can be coupled with an exigent need to improve energy performance of the building stock in the European Union and neighbouring countries. It is shown in this paper that around 46% of embodied energy and around 39% of embodied carbon per panel can be saved for a life span of 50 years, compared to conventional structural concrete insulated panels.

Optimisation of concrete mixtures made with crushed clay bricks and roof tiles

The main purpose of this paper is to show the possible applicability of concrete made using partial replacement of natural aggregate with crushed bricks and roof tiles in load-bearing structures. In total, 62 different concrete mixtures with crushed bricks and roof tiles were made based on Box–Behnken design and experimentally tested. The selection of acceptable concrete mixtures was chosen according to experimental results and mathematical models of required properties (density, slump, compressive strength, tensile strength and modulus of elasticity). An optimal concrete mixture for a precast concrete beam and block floor system was chosen according to multi-criteria decision process. The applicability of concrete mixtures for precast concrete block and beam floor systems was tested regarding the requirements set out in standards HRN EN 15037-1:2008 and HRN EN 15037-2:2009.

Influence of silica fume on mechanical and physical properties of recycled aggregate concrete

Several studies related to sustainable concrete construction have encouraged development of composite binders, involving Portland cement, industrial by-products, and concrete mixes with partial replacement of natural aggregate with recycled aggregate. In this paper, the effects of incorporating silica fume (SF) in the concrete mix design to improve the quality of recycled aggregates in concrete are presented. Portland cement was replaced with SF at 0%, 5% and 10%. Specimens were manufactured by replacing natural aggregates with recycled aggregates. Two size fractions (4/12mm and 8/22mm) as recycled aggregates were used and four series of concrete mixtures were produced. In all concrete mixtures, a constant water/binder ratio at 0.50 was used and concrete mixtures with a target initial slump of S4 class (16–21cm) were prepared. Concrete properties were evaluated by means of compressive strength, tensile splitting strength, water absorption and ultrasonic pulse velocity and it was found that, using 10% SF as a cement replacement for recycled aggregate concretes enhanced the mechanical and physical properties of concrete. At all the test ages the tensile splitting strength gain of the natural aggregate concrete mixture (NA) with and without SF was higher than that of the recycled concrete mixtures. Continuous and significant improvement in the tensile splitting strength of recycled aggregate concretes incorporating SF was observed. Similar to compressive strength test results, concrete incorporating 10% SF and containing 4/12mm fraction recycled aggregates showed better performance among recycled aggregate concretes.

Possibilities of Recycled Concrete Aggregate in Cement-Based Flowscreed

This paper presents some test-results of using fine recycled concrete as a partial replacement of natural aggregates in cement-based flowscreed. Special attention is given to describing and studying rheological characteristics and mechanical properties of cement-based flowscreed. Experimental results indicate that it is possible to prepare flowscreed with partial replacement of natural aggregates by recycled aggregates and obtain a quality that meets the requirements. This study was partially connected to the research-project RecyFlowscreed [1].

On the reliability of reusing bottom ash from municipal solid waste incineration as aggregate in concrete

The present work concerns an experimental investigation on the use of residues derived from fluidized bed incinerators as aggregates for concrete. Concrete mixtures were obtained from conventional mix designs used in the production of unreinforced precast elements by partial replacement of natural aggregates with recycled components. The characterization was performed by means of physical and mechanical tests according to the prescriptions of the Italian technical code for construction, with special attention to the probabilistic evaluation of the compressive strength and an investigation of the tensile behavior of the considered specimens. The simplified statistical analysis shows that mixtures containing recycled aggregates may achieve characteristic values of the compressive strength that are very close to the performance of conventional mix designs that are commonly used in the investigated applications. The average compressive strength and the material reliability, i.e., the scattering of results, of concretes containing recycled aggregates are both comparable with those of the reference concrete. Conversely, an investigation on the tensile strength points out a lower performance for mix designs including recycled aggregates. In both cases, the adoption of 42.5R cement is found to remarkably improve experimental results, i.e., to reduce the gap between the performance of concretes containing recycled aggregates and the reference concrete.

Lightweight Concrete Incorporating Waste Expanded Polystyrene

This paper covers the results of an experimental investigation on mechanical and durability properties of concrete containing waste polystyrene based lightweight aggregate called Stabilised Polystyrene (SPS) as a partial replacement of natural aggregates. The properties investigated in this paper were water absorption by capillary action and total absorption, compressive strength and ultrasonic pulse velocity (UPV). The composite aggregate was formed with 80% waste polystyrene which was shredded to different sizes, 10% of a natural additive to improve the resistance to segregation and 10% Portland cement. The natural fine aggregate were replaced with 0%, 30%, 60% and 100% (by volume) of SPS. There was an increasing in water absorption and a decreasing in compressive strength and UPV with the increase in SPS aggregate content in concrete.

High Temperature Testing of Cement Mortar Containing MSWI Bottom Ash

High temperature testing of cement mortar containing bottom ash (BA) generated by municipal solid waste incineration (MSWI) as partial replacement of natural aggregate is presented in the paper. The measurements of mechanical properties, bulk density, matrix density, and total open porosity are performed on samples exposed to the temperatures of 20°C to 1000°C. TGA analysis is performed as well. Finally, the studied samples are analyzed by IR spectroscopy in order to evaluate TGA data. The obtained results indicate a comparable performance of the mortar modified by BA with the reference material.

Recycled plastic aggregate in mortars composition: Effect on physical and mechanical properties

In this paper artificial aggregates based on recycled plastic materials, mostly polyolefin and polyethylene terephthalate waste, were used as partial replacement of natural aggregates for manufacturing hydraulic mortars. In particular, different amounts (10–50% by weight) of siliceous sand were substituted by the same weight of the above plastic waste, to obtain six mortars with different composition. The influence of plastic addition on physical and mechanical properties (density, porosity, compressive and flexural behavior and water vapour permeability) was studied. Moreover the thermal conductivity of the obtained mortars was evaluated.Recycled plastic substitution enhances the open porosity, causing a decrease in flexural and compressive strength, with an increase in water vapour permeability. Nevertheless, the presence of plastic aggregate leads to a significant reduction in thermal conductivity, which improves the thermal insulation performances of the mortar.For this reason the addition of recycled plastic aggregate in the manufacturing of hydraulic mortars can be considered a way to reduce the growing environmental impact of polymers and, at the same time, it allows the development of increasingly eco-sustainable building materials.

Production of Concrete Blocks with Residues for Civil Construction

The Construction is recognized as one of the most important activities for the economic and social development, and on the other hand, behaves also as a major generator of environmental impacts, either by consumption of natural resources, the modification of the landscape or the generation of construction and demolition waste (CDW). Investing in an implementation of managed clean and healthy in the area of CDW is essential for the environment and for the economy of the cities, who are spending less resources on the collection, cleaning of drains and treatment of diseases. Nowadays, the amount of waste generated is considered large, occupying much space in landfills, and its transportation, depending on the volume and weight, is quite expensive. Recycling and reuse of these wastes are extremely important to control and mitigate environmental problems, as well as produce various materials value-added. Over 90% of waste can be recycled, reused and transformed into aggregates with characteristics very similar to the original product, thus creating environmentally friendly products such as sand, gravel, pebbles. This research concerns the study of the properties of concrete containing CDW, aiming its use in the manufacture of concrete blocks to seal without structural function. Blocks have been molded with partial replacement of natural aggregates by recycled aggregates and later were performed tests of compressive strength in accordance with the standards to prove the technical feasibility of the material for the trait studied.

Using ceramic wastes from tile industry as a partial substitute of natural aggregates in hot mix asphalt binder courses

The technical feasibility of using recycled ceramic aggregates as a partial replacement of natural aggregates in hot mix asphalt was investigated. Recycled ceramic aggregates were obtained crushing stoneware and porcelain tile wastes from the ceramic industry. Both natural and recycled aggregates were characterized by suitability tests to be utilized in bituminous mixtures. Asphalt concrete binder course mixtures were designed through the Marshall method and the European CE marking standards. The mixtures were produced in both laboratory and asphalt plant, evaluating the influence of real production and scale factors. The addition of recycled ceramic aggregates increased binder, filler and air void contents, as well as the resistance to plastic deformation and the retained indirect tensile resistance after immersion. Nonetheless, worse moisture susceptibility with compressive strength and worse values of Marshall stability and deformation were observed. Up to 30% of natural aggregates were replaced by recycled ceramic aggregates with good mechanical conditions according to Spanish specifications. The main conclusion was that hot bituminous mixtures with a reasonable addition of recycled ceramic aggregates can satisfy binder course performance requirements for medium-low volume roads.

Recycled Aggregate Concrete with Fluorescent Waste Glass and Coal/Wood Ash Concrete Wastes

Consumption of natural aggregate as the largest concrete component is constantly and rapidly increasing with the increase in the production and utilization of concrete. Recycled aggregate is a valuable resource as replacement for virgin aggregate in concrete. In present study is investigated the approach of optimized utilization of concrete aggregate wastes (CAW) in concrete. The produced concrete cube specimens with fluorescent waste glass powder/suspension and fly/wood ash after determination of their mechanical properties are recycled and used as partial replacement of natural aggregates in recycled aggregate concrete (RAC). Therefore, it helps to convert waste product with determined properties into recourse and potentially to reduce the amount of waste disposed and preserve natural resources. The mechanical properties of recycled aggregate concrete are discussed from the point of the potential of its utilization in structural concrete. DOI: http://dx.doi.org/10.5755/j01.sace.1.1.2615