76 research outputs found
Quality Assessment of Mixed and Ceramic Recycled Aggregates from Construction and Demolition Wastes in the Concrete Manufacture According to the Spanish Standard
[EN] Construction and demolition waste (CDW) constitutes an increasingly significant
problem in society due to the volume generated, rendering sustainable management and
disposal problematic. The aim of this study is to identify a possible reuse option in the
concrete manufacturing for recycled aggregates with a significant ceramic content: mixed
recycled aggregates (MixRA) and ceramic recycled aggregates (CerRA). In order to do so,
several tests are conducted in accordance with the Spanish Code on Structural Concrete
(EHE-08) to determine the composition in weight and physic-mechanical characteristics
(particle size distributions, fine content, sand equivalent, density, water absorption,
flakiness index, and resistance to fragmentation) of the samples for the partial inclusion of
the recycled aggregates in concrete mixes. The results of these tests clearly support the
hypothesis that this type of material may be suitable for such partial replacements if simple
pretreatment is carried out. Furthermore, this measure of reuse is in line with European,
national, and regional policies on sustainable development, and presents a solution to the
environmental problem caused by the generation of CDW
Influence of the use of External Carbon Fiber Reinforcement on the Flexural Behavior of Prismatic Concrete Test Specimens. An Application for Repairing of Deteriorated Agricultural Structures
This manuscript reports a study of the capacity of polymer composites to increase flexural
strength in concrete. The polymer composites reinforced with carbon fiber and bonded with epoxy
adhesive were used in prismatic test specimens of mass concrete corresponding to two different
morphologies. The aim was to simulate the restoration of deteriorating concrete agricultural structures
in order to explore the viability of this alternative against replacing them. An increase was found in
the strength of the elements tested, with a higher strength being observed in those test specimens
presenting a modified geometry.NOThis research was funded by SPANISH MINISTER OF ECONOMY AND COMPETITIVENESS, grant number BIA2017-83526RThe authors acknowledge the technical support and material used for experiments donated by Sika Grou
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 techS
Recycling Aggregates for Self-Compacting Concrete Production: A Feasible Option
[EN] The use of construction and demolition wastes (C&DW) is a trending future option for
the sustainability of construction. In this context, a number of works deal with the use of recycled
concrete aggregates to produce concrete for structural and non-structural purposes. Nowadays, an
important number of C&DW management plants in the European Union (EU) and other countries
have developed robust protocols to obtain high-quality coarse recycled aggregates that comply with
different European standards in order to be used to produce new concrete. The development of
self-compacting concrete (SCC) is another way to boost the sustainability of construction, due to the
important reduction of energy employed. Using recycled aggregates is a relatively recent scientific
area, however, studies on this material in the manufacture of self-compacting concrete have proven
the feasibility thereof for conventional structural elements as well as high-performance and complex
structural elements, densely reinforced structures, difficult-to-access formwork and difficult-to-vibrate
elements. This paper presents an original study on the use of coarse recycled concrete aggregate
(CRA) to obtain self-compacting concrete. Concrete with substitution ratios of 20%, 50% and 100%
are compared with a control concrete. The purpose of this comparison is to check the influence of
CRA on fresh SCC as well as its physical and mechanical properties. The parameters studied are
material characterization, self-compactability, compressive strength, and tensile and flexural strength
of the resulting concrete. The results conclude that it is feasible to use CRA for SCC production with
minimal losses in the characteristics
Re-use of construction and demolition residues and industrial wastes for the elaboration or recycled eco-efficient concretes
[EN] 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 yr
–1
. 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 engineerin
Effect of Design Parameters on Compressive and Split Tensile Strength of Self-Compacting Concrete with Recycled Aggregate: An Overview
[EN] 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
Self-healing concrete with recycled aggregates
[EN] The higher water absorption of recycled aggregates is the main drawback which hinders the reuse of this secondary material, limiting its acceptance in the construction market. This study proposes the microbially induced carbonate precipitation (by using Bacillus sphaericus) to improve the quality of mixed and ceramic recycled aggregates. This precipitation has contributed to a weight increase and has unleashed a waterproofing response, most effectively on the roughest particle surfaces. High ceramic content aggregates profited from a greater biodeposition, leading to a remaining amount of precipitates is more deeply fixed in cementitious materials. The pore-filling effect was detected by SEM, supporting the waterproofing result. The use of biotreated aggregates led to more fluid recycled concrete consistencies when the same amount of mixing water was used. Without water adjustments in the concrete mixture, the presence of calcium carbonate lessened long-term compressive strength, although strength development was accelerated, with higher early-age (7 days) values than observed for concrete bearing untreated recycled aggregate
Biodegradable Polymers on Cementitious Materials
[EN] Nowadays the sustainability and safety requirements of structures inspire the study of new
self-healing materials and preventive repair methods on cementitious elements. To achieve this
undertaking, this research replaces widely employed synthetic polymers by biodegradable ones as
consolidants and water-repellents, and assesses the protection and consolidation effect of biopolymers
(obtained by using waste biomass of mixed microbial cultures from polyhydroxyalkanoates production
processes) as eco-friendly healing agents by analysing the water absorption of two kind of materials.
The first group of samples are cement mortar specimens whose external surface has been treated with
biopolymer products and subsequently evaluated by water drop absorption test. The second group of
samples are cement mortar specimens formulated with biopolymer products included in its mixing water
and later the waterproofing efficiency is analysed by capillary water absorption tests. The water
absorption behaviour of both kind of samples shows a potential improvement of cementitious elements
durability, since water absorption results have decreased for treated samples in comparison with
untreated one
Biodegradable polymers on cementitious materials
PTDC/EPH-PAT/4684/2014 IF/01054/2014/CP1224/CT0005 UID/QUI/50006/2019 UID/Multi/04378/2019 POCI-01-0145-FEDER-007728Nowadays the sustainability and safety requirements of structures inspire the study of new self healing materials and preventive repair methods on cementitious elements. To achieve this undertaking, this research replaces widely employed synthetic polymers by biodegradable ones as consolidants and water-repellents, and assesses the protection and consolidation effect of biopolymers (obtained by using waste biomass of mixed microbial cultures from polyhydroxyalkanoates production processes) as eco-friendly healing agents by analysing the water absorption of two kind of materials. The first group of samples are cement mortar specimens whose external surface has been treated with biopolymer products and subsequently evaluated by water drop absorption test. The second group of samples are cement mortar specimens formulated with biopolymer products included in its mixing water and later the waterproofing efficiency is analysed by capillary water absorption tests. The water absorption behaviour of both kind of samples shows a potential improvement of cementitious elements durability, since water absorption results have decreased for treated samples in comparison with untreated ones.authorsversionpublishe
Biodegradable Polymers on Cementitious Materials
[EN] Nowadays the sustainability and safety requirements of structures inspire the study of new
self-healing materials and preventive repair methods on cementitious elements. To achieve this
undertaking, this research replaces widely employed synthetic polymers by biodegradable ones as
consolidants and water-repellents, and assesses the protection and consolidation effect of biopolymers
(obtained by using waste biomass of mixed microbial cultures from polyhydroxyalkanoates production
processes) as eco-friendly healing agents by analysing the water absorption of two kind of materials.
The first group of samples are cement mortar specimens whose external surface has been treated with
biopolymer products and subsequently evaluated by water drop absorption test. The second group of
samples are cement mortar specimens formulated with biopolymer products included in its mixing water
and later the waterproofing efficiency is analysed by capillary water absorption tests. The water
absorption behaviour of both kind of samples shows a potential improvement of cementitious elements
durability, since water absorption results have decreased for treated samples in comparison with
untreated one
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