Influence of Design Parameters on Fresh Properties of Self-Compacting Concrete with Recycled Aggregate—A Review

[EN] This article presents an overview of the bibliographic picture of the design parameter’s influence on the mix proportion of self-compacting concrete with recycled aggregate. Design parameters like water-cement ratio, water to paste ratio, and percentage of superplasticizers are considered in this review. Standardization and recent research on the usage of recycled aggregates in self-compacting concrete (SCC) exploit its significance in the construction sector. The usage of recycled aggregate not only resolves the negative impacts on the environment but also prevents the usage of natural resources. Furthermore, it is necessary to understand the recycled aggregate property’s role in a mixed design and SCC properties. Design parameters are not only influenced by a mix design but also play a key role in SCC’s fresh properties. Hence, in this overview, properties of SCC ingredients, calculation of design parameters in mix design, the effect of design parameters on fresh concrete properties, and the evolution of fresh concrete properties are studied.S

Effect of pores on the mechanical and durability properties on high strength recycled fine aggregate mortar

[EN] Larger consumption of natural fine aggregates (NFA) leads to an increase in cost, energy, and negative environmental impact. On the contrary, the larger production of construction waste results in the generation of recycled fine aggregate (RFA), which requires safe disposal. The aim of study, is to the hunt for such alternatives, compares the mortar mechanical and durability properties with and without RFA. High strength mortar specimens were produced with mix proportion as 1:3 using RFA as partial replacement for NFA as 0%, 25%, 50% and 100%. The mechanical and durability performance of all specimens was assessed in the terms of compressive strength, flexural strength, water absorption and mercury intrusion porosimetry. Mechanical performance is confirmed by microscopic studies. The main results display that the mortar with 25% of RFA, performed better, which are related to pore structures and their distribution. It is noted that the, pores also increase with the increase in RFA content. The effect of pores on the strength and their relationships are assessed.SIAuthor wish to thank for the supports and guidance given by faculties from University of Leon, Leon, Spain and Coimbatore Institute of Technology, Coimbatore, Indi

Estudio de la mejora de la durabilidad de hormigones reciclados con biopolímeros

Una de las mayores preocupaciones que surgen al trabajar con hormigónes reciclados es la de saber cómo garantizar su durabilidad para que sea tan buena como la del hormigón convencional. ¿Es posible hacerlo sin utilizar productos químicos insostenibles?En este estudio se han ensayado varios biopolímeros, considerados como productos naturales respetuosos con el medio ambiente. Los biopolímeros fueron obtenidos en la Universidad Nova de Lisboa (Portugal) mediante un proceso de generación de polihidroxialcanoatos (PHA) utilizando cultivos microbianos mixtos que han actuado sobre biomasa residual procedente de extracto de pino y glicerol. El ensayo, que se llevó a cabo en la Universidad de León, consistió en recubrir con los biopolímeros la cara superior de varias probetas cúbicas de hormigón y evaluar posteriormente la mejora de la durabilidad que los biotratamientos desarrollaban, efecto que se cuantificó mediante el ensayo de absorción de una gota de agua. Las probetas analizadas procedían de dos tipos de hormigón: un hormigón reciclado con 50% de árido grueso natural sustituido por árido reciclado mixto cerámico procedente de residuos de construcción y demolición, y un segundo hormigón, equivalente al anterior, pero en el que se sustituye además el cemento convencional por cemento reciclado. Este cemento reciclado es 75% cemento Portland y 25 % de residuo cerámico. Los resultados mostraron que hay una significativa disminución de la absorción de agua en el hormigón biotratado, siendo notablemente superior en las muestras de hormigón con cemento reciclado

Pre-Saturation Technique of the Recycled Aggregates: Solution to the Water Absorption Drawback in the Recycled Concrete Manufacture

The replacement of natural aggregates by recycled aggregates in the concrete manufacturing has been spreading worldwide as a recycling method to counteract the large amount of construction and demolition waste. Although legislation in this field is still not well developed, many investigations demonstrate the possibilities of success of this trend given that concrete with satisfactory mechanical and durability properties could be achieved. However, recycled aggregates present a low quality compared to natural aggregates, the water absorption being their main drawback. When used untreated in concrete mix, the recycled aggregate absorb part of the water initially calculated for the cement hydration, which will adversely affect some characteristics of the recycled concrete. This article seeks to demonstrate that the technique of pre-saturation is able to solve the aforementioned problem. In order to do so, the water absorption of the aggregates was tested to determine the necessary period of soaking to bring the recycled aggregates into a state of suitable humidity for their incorporation into the mixture. Moreover, several concrete mixes were made with different replacement percentages of natural aggregate and various periods of pre-saturation. The consistency and compressive strength of the concrete mixes were tested to verify the feasibility of the proposed technique

Effect of Design Parameters on Compressive and Split Tensile Strength of Self-Compacting Concrete with Recycled Aggregate: An Overview

One of the prime objectives of this review is to understand the role of design parameters on the mechanical properties (Compressive and split tensile strength) of Self-Compacting Concrete (SCC) with recycled aggregates (Recycled Coarse Aggregates (RCA) and Recycled Fine Aggregates (RFA)). The design parameters considered for review are Water to Cement (W/C) ratio, Water to Binder (W/B) ratio, Total Aggregates to Cement (TA/C) ratio, Fine Aggregate to Coarse Aggregate (FA/CA) ratio, Water to Solid (W/S) ratio in percentage, superplasticizer (SP) content (kg/cu.m), replacement percentage of RCA, and replacement percentage of RFA. It is observed that with respect to different grades of SCC, designed parameters affect the mechanical properties of SCC with recycled aggregates

Performance of graphene oxide as a water-repellent coating nanomaterial to extend the service life of concrete structures

Surface treatments help to protect the built heritage against damage (environmental, accidental, etc.), reducing repair and restitution costs and increasing the useful life of building materials. The use of nanomaterials is currently the most important field of research in surface treatment technology for the preservation of building materials and, more specifically, to improve their durability and prevent their deterioration, extending their useful life. This paper studies the influence of a graphene oxide (GO) suspension as a surface treatment on the properties of concrete. The results indicate that, at best, surface treatment with GO can decrease both the water absorption and capillary absorption of concrete by about 15 %. The increase in the amount of GO deposited as a surface treatment leads to a further reduction in concrete water absorption. It is shown that, at best, GO coating also reduces water penetration at low and high pressures by approximately 20 % and 60 %, respectively. In addition, scanning electron microscopy analysis shows that GO surface treatment facilitates the hydration process and densifies the concrete microstructure. A simple aqueous suspension of GO is revealed as a tool with a high potential to protect concrete surfaces in a fast and cost-effective way, thanks to the easy application by spraying and the small amount of material needed to obtain great results

Paving with Precast Concrete Made with Recycled Mixed Ceramic Aggregates: A Viable Technical Option for the Valorization of Construction and Demolition Wastes (CDW)

This research aimed to prove the feasibility of producing two types of precast elements widely used in construction, such as curbstones and paving blocks, using recycled concrete made with a 50% substitution of the natural gravel by recycled mixed aggregates with a significant ceramic content (>30%). In order to prove the quality of such mass concrete recycled precast elements, two different mixes were used: the first one was a conventional concrete mix provided by Prefabricados de Hormigón Pavimentos Páramo S.L., one of the collaborating companies in this study, and the other was a mixture in which wt 50% of the natural coarse aggregates were substituted for recycled mixed aggregates ceramic (RMAc). This recycled aggregate is a heterogeneous mixture of unbound aggregates, concrete, ceramic, etc., used as a secondary recycled aggregate and commonly produced in a lot of recycling plants in many European countries. This material was supplied by Tecnología y Reciclado S.L., the other collaborating company. Both mixtures were representative in order to establish the comparative behavior between them, taking into account that smaller percentages of replacement of the natural with recycled aggregates will also produce good results. This percentage of substitution represents a high saving of natural resources (gravel) and maintains a balanced behavior of the recycled concrete, so this new material can be considered to be a viable and reliable option for precast mass concrete paving elements. The characterization of the recycled precast elements, covering mechanical, microstructural, and durability properties, showed mostly similar behavior when compared to the analogous industrially-produced pieces made with conventional concrete

Re-use of construction and demolition residues and industrial wastes for the elaboration or recycled eco-efficient concretes

Production of residues from industries and construction and demolition sectors has increased during last years. The total amount of debris produced according to different estimations reaches values close to 42 million tonnes yr1. Much of this waste has been thrown to landfill, without considering its potential for reuse, recycling or valuation. The aim of this research is to describe some of the physical and mechanical properties of different laboratory-mixed concretes, using various proportions of additional materials recovered from industrial waste and demolition rubble. The added materials are included either as admixtures (forestry residues, cork dust, steel fibre) or in partial substitution of natural aggregates (wire from electrical residues, tyre rubber, white ceramic, sanitary porcelain or shale). The laboratory tests have followed the standard EN protocols. Assay results were variable according to the nature of the material added to the mix: organic materials and shale, despite the steel fibre reinforcement, reduce the compression strength, but are suitable for the manufacture of lightweight concrete for agricultural pavements, with certain flexion resistance and a relatively good behaviour to impact. The substitution of natural aggregates with ceramic and porcelain wastes produces a significant increase in compression resistance, making them suitable for the manufacture of concrete with characteristic resistances above 40 MPa, which can be used both for structures or other agricultural elements: separators, feeders, slat floors. As a conclusion can be stated the possibility of reuse these wastes for the production of structural or non-structural concrete, with different applications in agricultural engineering.La producción de residuos industriales y los procedentes del sector de la construcción y demolición se han incrementado en los últimos años, hasta alcanzar valores cercanos a los 42 millones de toneladas año1. Gran parte de estos residuos han ido a parar a vertedero, sin considerar sus posibilidades de reutilización. Los trabajos desarrollados en este artículo tienen por objeto conocer las propiedades físicas y mecánicas de varios hormigones elaborados en laboratorio, añadiéndoles diversas proporciones de residuos industriales y escombros. Estos materiales son incluidos bien como adiciones (residuos forestales, polvo de corcho, polvo de corcho+fibra de acero) o bien en sustitución parcial de los áridos naturales utilizados en la dosificación (residuo de cable eléctrico, restos de neumáticos, cerámica blanca y sanitaria o pizarra). Para la elaboración de hormigones se han seguido los protocolos de la normativa EN. Los resultados de los ensayos son variables en función del material incorporado: los materiales orgánicos y la pizarra, a pesar del refuerzo de fibra de acero reducen la resistencia a compresión, pero son adecuados para la elaboración de hormigones ligeros para pavimentos agropecuarios, ya que mantienen cierta resistencia a la flexión y un buen comportamiento al impacto. La inclusión de cerámica y residuos de porcelana produce aumentos apreciables de la resistencia a la compresión, lo que les hace adecuados para la elaboración de hormigones con resistencias superiores a los 40 MPa, que pueden ser utilizados tanto para estructuras como para otros elementos del ámbito agropecuario: separadores, comederos, suelos, enrejillados, etc

Evaluation of Mechanical Characteristics of Cement Mortar with Fine Recycled Concrete Aggregates (FRCA)

© 2021 by the authors.One of the growing demands in concrete manufacture is the availability of natural fine aggregates, which account for 35% to 45% of the total concrete. An alternative method of disposal of fine recycled concrete aggregates (FRCA) generated from demolition and construction waste (C&DW) is their usage in mortar and the development of recycled mortar. The main aim of this research work is to evaluate the viability of incorporating FRCA from urban C&DW for the manufacture of cement-based mortars. Simple processing techniques like washing and sieving are adopted to improve the FRCA quality. Physical and chemical characterization of ingredients is carried out. In total four mixes of 1:3 (cement: sand) mortar with partial replacement of normalized sand with FRCA (0%, 25%, 50%, and 100%) are evaluated for mechanical properties. Water to cement ratio for all four mortar mixes are determined by fixed consistency. Mechanical and physical properties like density, compressive strength, and flexural strength are studied for various curing periods, and the result is that the optimum usage of FRCA is 25% based on a 90-day curing period.This work has been financially supported by the Spanish Ministry of Economy and Competitiveness through the research project grant BIA2017-83526-R.Peer reviewe