Replacement Of Conventional Aggregate Research Articles

Microconcretos autoadensáveis contendo resíduo de rocha ornamental e resíduo de poliestireno expandido: influência das relações filler/cimento e agregados leves/convencionais

Abstract Eco-efficient self-compacting micro concretes with partial replacement of Portland cement by ornamental stone waste (OSW) and replacement of conventional aggregates by expanded polystyrene waste were addressed in this study. A base mixture was obtained using a particle packing method, and replacement fractions followed a second-order composite experimental design. The mixtures’ rheological, physical, mechanical and eco-efficiency parameters were evaluated and discussed. As expected, the incorporation of residues reduced the mechanical strength, and mixtures with high incorporation of lightweight aggregates tended to segregate. However, OSW has been shown to increase workability and decrease viscosity, contributing to control segregation due to the reduced amount of water required without impairing the fluidity of the mix. At the same time, the lightweight aggregate decreased both the density of the mixtures and the viscosity. The interaction of the residue with the lightweight aggregate proved promising in obtaining more eco-efficient lightweight microconcretes.

Investigation of Lightweight and Green Concrete Characteristics Using Coconut Shell Aggregate as a Replacement for Conventional Aggregates

Investigation of Lightweight and Green Concrete Characteristics Using Coconut Shell Aggregate as a Replacement for Conventional Aggregates

Analysis of concrete characteristics with the incorporation of construction waste aggregates

In order to reuse civil construction materials, research is carried out to obtain an efficient recycled concrete, promoting sustainability. The objective of this work is to compare the compressive strengths of the concrete specimen, with conventional and recycled aggregates, as well as the influence of granulometry on the strength and physical properties of the aggregates. For this purpose, aggregates from civil construction waste were incorporated into the concrete, replacing part of the coarse aggregates. Specimens were made with the following replacement percentages: 0%, 5%, 10%, and 15%, for multiple comparisons. The control group had no replacement of conventional aggregates by recycled ones (0%). The following tests were carried out: granulometric, density, water absorption, compressive strength, and slump test. Recycled concrete presents itself as a viable option in non-structural concretes, presenting greater efficiency in the compressive strength test at granulometry of 4.75 – 9.50 mm, with 15% incorporation.

EFFECTS OF USING PALM KERNEL SHELL AND SPIKELET FIBERS AS COARSE AGGREGATE FOR LIGHTWEIGHT CONCRETE

Agricultural and Industrial wastes have created waste management and pollution problems. The replacement of conventional ingredients in concrete production would reduce construction cost and proper waste management. The percentages of spikelet fibers in the composites were 0%, 0.25%, 0.5%, 0.75% and 1%. Concrete cubes and rectangular bricks of sizes 150mm x 150mm x 150mm and 40mm x 40mm x 160mm respectively with different percentages of spikelet fibers cured and tested after 7 and 28 days. The flexural strength, compressive strength, Density, slump workability, rate of water absorption and grain size were analyzed. It results that palm kernel shells was well graded and a good replacement for conventional aggregates. The density and compressive strength after 28 days curing were within the range 1645 to 1749kg/m3 and 15.35 to 19.21kg/m3 respectively. It was observed that slump workability reduced while compressive strength, water absorption, density and flexural strength increases proportionately with fiber contents.

Physical and Mechanical Characteristics of Sustainable Concrete Comprising Industrial Waste Materials as a Replacement of Conventional Aggregate

In a sustainable approach, it is essential to reduce waste materials for improving the urban environmental performance leads to development in the livable, sustainable, and greener city. In pursuit of this goal, iron lathe waste was used in this study as a replacement of fine aggregate to produce sustainable concrete. Iron lathe waste is generally a waste material from the lathe machine, which is abundantly available to an extent. These waste materials may lead to environmental and health concerns. Therefore, the main goal of this study is to experimentally examine the physio-mechanical characteristics of sustainable concrete incorporating lathe iron waste. The lathe iron waste dusts (LIWD) were used as a partial replacement of fine aggregate in different levels by weight (5%, 10%, 15%, and 20%) to fabricate the sustainable concrete. The mechanical and physical properties of sustainable concrete were investigated by conducting tests, such as workability, ultrasonic pulse velocity, compressive strength, splitting tensile strength, and flexural strength to investigate the properties of the alternative concrete comparing with that of conventional concrete. The experimental results showed that the LIWD significantly enhanced the tensile, flexural, and compressive strength of the concrete up to 13%, 19%, and 38%, respectively. Therefore, LIWD can potentially improve the serviceability of the structural elements.

Influence of GGBS- based Geopolymer Aggregate on Compressive Strength of Concrete

Concrete is the most widely used building component in the world due to its versatility, low cost and durability. Most common coarse aggregate used in the construction are stones which is obtained from quarry. The demand for coarse aggregate in the construction industry has consequently increased due to the extensive use of natural resources. It has necessitated research into alternative materials of construction. This research aims to find the alternate material for coarse aggregate by using Ground Granulated Blast furnace Slag (GGBS) clinker and to determine the hardened properties of non-conventional concrete in M20 Grade. The aggregate utilized in this work is an Eco friendly material, which replace the conventional coarse aggregate to preserve the depletion of natural resources. It is abundantly available than the conventional aggregate and reduce pollution. This paper focuses on investigating characteristics of concrete with replacement of coarse aggregate by GGBS Clinker. This study deals with the GGBS clinker advantages and limitations in concrete. The usage of GGBS clinker serves as a replacement of conventional aggregate to reduce the depletion of conventional building materials. It serves as an Eco friendly way of utilizing the by- product without dumping it on ground.

A new formulation for strength characteristics of steel slag aggregate concrete using an artificial intelligence-based approach

Steel slag, an industrial reject from the steel rolling process, has been identified as one of the suitable, environmentally friendly materials for concrete production. Given that the coarse aggregate portion represents about 70% of concrete constituents, other economic approaches have been found in the use of alternative materials such as steel slag in concrete. Unfortunately, a standard framework for its application is still lacking. Therefore, this study proposed functional model equations for the determination of strength properties (compression and splitting tensile) of steel slag aggregate concrete (SSAC), using gene expression programming (GEP). The study, in the experimental phase, utilized steel slag as a partial replacement of crushed rock, in steps 20%, 40%, 60%, 80%, and 100%, respectively. The predictor variables included in the analysis were cement, sand, granite, steel slag, water/cement ratio, and curing regime (age). For the model development, 60-75% of the dataset was used as the training set, while the remaining data was used for testing the model. Empirical results illustrate that steel aggregate could be used up to 100% replacement of conventional aggregate, while also yielding comparable results as the latter. The GEP-based functional relations were tested statistically. The minimum absolute percentage error (MAPE), and root mean square error (RMSE) for compressive strength are 6.9 and 1.4, and 12.52 and 0.91 for the train and test datasets, respectively. With the consistency of both the training and testing datasets, the model has shown a strong capacity to predict the strength properties of SSAC. The results showed that the proposed model equations are reliably suitable for estimating SSAC strength properties. The GEP-based formula is relatively simple and useful for pre-design applications.

Effects of Partial Replacement of Coarse Aggregates with Reclaimed Rubber on the Mechanical Properties of Hardened Concrete

<p>The replacement of conventional aggregates with alternate materials like Reclaimed Rubber (RR) results in reduction of self-weight and compressive strength of concrete. This reduction in self-weight further decreases the dead load which contributes towards contraction in size of concrete members and reinforcement requirements. This diminution in compressive strength is compensated by replacing cement with supplementary materials like Silica Fume, Fly Ash or GGBS. This research focuses on the effects of partial replacement of cement and coarse aggregates with Silica Fume (SF) and Reclaimed Rubber (RR) respectively in the concrete mix. Concrete mix was prepared for M20 grade by replacing cement and coarse aggregates with SF and RR respectively for cube and cylinder samples. A base study has been carried out through compression and split tension tests by partially replacing cement with SF in 3 percent increments up to 24 percent. Maximum compressive strength of 19.6N/mm<sup>2</sup>, 24.2N/mm<sup>2</sup> and 32.5N/mm<sup>2</sup> was obtained at 12% replacement of cement with SF by weight while testing specimens after 7, 14 and 28 days of curing. Maximum strength of 2.4N/mm<sup>2</sup>, 2.9N/mm<sup>2</sup> and 3.1N/mm<sup>2</sup> was obtained during split tension tests conducted after 7, 14 and 28 days of curing period. Further compression and tension tests were conducted replacing cement with 12%SF along with various proportions of RR replacing coarse aggregates after different curing periods. Experiments reveal that a combination of 12%SF and 9%RR replacement produces maximum compressive strength of 19.2N/mm<sup>2</sup>, 23.1N/mm<sup>2</sup> and 29.4N/mm<sup>2</sup> after curing the samples for 7, 14 and 28 days respectively. The tensile strength decreases as the rubber content is increased in the concrete mix along with optimum SF when compared with normal mix.</p>

Structural Behavior of Reinforced Concrete One-Way Slabs Cast with Self-Compacting Concrete Containing Recycled Concrete as Coarse Aggregate

This work deals with the effect of using Recycled Concrete Aggregate (RCA) as a partial replacement of coarse aggregate in Self-Compacting Concrete (SCC), on the structural behavior (flexure and shear) of reinforced concrete one-way slabs. To the authors’ knowledge, this study is one of limited studies concerning the behavior of recycled aggregate concrete one-way slabs subjected to line loading with significant replacement of conventional aggregates by recycled concrete aggregate (up to 75 %). Three replacement ratios were considered 25 %, 50 % and, 75 %. The mixes (with natural stone coarse aggregate, NCA) have an averaged compressive strength of (Fcu = 42 MPa) at the age of 28 days with a tolerance of (± 1.5 MPa). While, the mixes (with RCA) have an averaged compressive strength of (38.5, 36.5 and 34 MPa) for the three replacement ratios respectively, at the age of 28 days with a tolerance of (± 2 MPa). All the slabs were cast with length of (1600 mm), width of (600 mm), while the thickness was variable. For this purpose, sixteen reinforced concrete one-way slabs were cast and divided into five groups (G1 to G5). Different parameters that affect the behavior of one-way slabs were studied and include type of failure, replacement ratios of NCA by RCA, amount of main reinforcement, thickness and locations of line loadings along the span. Hardened concrete specimens results show that the compressive strength Fcu, tensile strength Ft, modulus of rupture Fr and modulus of elasticity E were decreased as the RCA replacement increased. The experimental results of slabs show that the ultimate capacity of slabs decreased as the RCA replacement increased, the deflection and strain increase as the RCA replacement increases and the crack width increases as the RCA replacement increases. From the results of ultimate capacity, cracking load and moment, deflections, crack width and pattern and concrete surface strains, it can be concluded that the recycled concrete aggregate can be used as a partial replacement of natural coarse aggregate to produce self-compacting concrete mixes. Also, the behavior of one way slabs cast with SCC containing RCA is acceptable.

Recycling steel slag from municipal wastewater treatment plants into concrete applications – A step towards circular economy

Municipal wastewater is a major source of the release of phosphorus into the marine environment, and its excessive release could negatively impact marine flora and fauna. In this study, steel slag a by-product from steel industry was used to remove phosphorus content from the municipal wastewater. The Langmuir isotherm model revealed a maximum adsorption capacity of 3.8 mg phosphate/g of steelmaking slag. The results showed that the phosphate removal efficiency of granular slag was about 90%. The wastewater contained a significant amount of iron and manganese content that was filtered out by the slag granules. X-ray fluorescence and x-ray diffraction analysis show that the wastewater treatment process changes the chemical phase composition of slag in addition to the absorption/adsorption of various chemicals within its pore structure. To recycle this waste slag after the water treatment process, that significantly altered its chemical and mineralogical composition, it was used in concrete as a replacement of conventional coarse aggregates. The results show that the treated slag aggregates provide compressive strength improvement of 32.5% and 18% at 7 days and 8.2 and 16.8% improvement at 28 days compared to that of raw slag and conventional aggregates, respectively. In addition, due to the pozzolanic nature of slag both the raw and treated slag aggregates showed a seamless monolithic bond at the interfacial transition zone between the slag and the cement matrix. This study demonstrates that the waste slag generated from the wastewater treatment process has a great potential to be used as a replacement of conventional aggregates in concrete applications.

Study on the reinforced manhole cover slab using coconut shell aggregate concrete

Abstract In this study, two sets of manhole cover slabs were cast; one set with conventional concrete and the other set with coconut shell aggregate concrete. In both the cases, in one set 10 mm steel reinforcements were used and in the other sets 12 mm steel reinforcements were used. These manhole covers were produced and tested as per IS 12592: 2002. In both the concrete, along with conventional materials and coconut shell, steel fibers and micro silica were used to reach the specification required for the manhole cover slab. As per IS 12592:2002, a size of 600 × 600 × 100 mm and light duty grade of manhole cover slab were selected and studied. Test parameters such as workability of mixes, density of mixes, settlement limits at test load, crack formation, ultimate load and settlements at ultimate load results were discussed and presented. It is observed that the settlement at the time of test load on both conventional and coconut shell aggregate concrete manhole cover slabs were well within the limit specified by IS 12592: 2002. In both the cases, there was no formation of cracks at the time of sustaining test load as per IS 12592:2002. Load factors against ultimate failure were more than 4 in all the cases and hence, coconut shell aggregate concrete can be used for the production of manhole cover slabs. Test results and performance of coconut shell aggregate concrete manhole cover slabs encourage the use of coconut shell as an aggregate as the replacement of conventional aggregate in the production of manhole covers.

Pre-Soaked Lightweight Aggregates as Additives for Internal Curing of High-Strength Concretes

Abstract Self-desiccation and autogenous shrinkage of high-strength concretes is one of their drawbacks which cannot be readily accommodated by conventional curing. The concept of internal curing using lightweight soaked aggregates, to provide internal reservoirs of water which enable uniform curing of the whole cross-section, has been advanced by several groups. The present study is intended to develop this approach further, by optimizing the porosity and size of the aggregates to enable successful internal curing with only a small amount of aggregates, which could be viewed as additives rather than bulk replacement of conventional aggregates. The approach taken was to increase the porosity of the aggregates and reduce their size, to obtain a system with numerous internal reservoirs of sufficiently small spacing to allow water to be readily discharged from the aggregate and transported over the whole range of the matrix. It was shown that aggregates with porosities of about 50% by volume, a size of a few millimeters, and contents of less than 50 kg/m3 could provide full elimination of autogenous shrinkage in concretes having w/cm as low as 0.25, with only a small affect on strength. The parameters controlling the efficiency of the aggregates were assessed, indicating that their pore structure is the most important one, and that water from within the aggregates can be readily transported into the matrix to a distance of few millimeters.