scholarly journals Influence of Pozzolan, Slag and Recycled Aggregates on the Mechanical and Durability Properties of Low Cement Concrete

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4173
Author(s):  
Eliana Soldado ◽  
Ana Antunes ◽  
Hugo Costa ◽  
Ricardo do do Carmo ◽  
Eduardo Júlio
Keyword(s):  
Fly Ash ◽  
Mechanical Performance ◽  
Concrete Surface ◽  
Recycled Aggregates ◽  
Partial Replacement ◽  
Natural Pozzolans ◽  
Durability Properties ◽  
Chloride Attack ◽  
Natural Aggregates ◽  
Reduction Of Co2

The sustainability of the construction sector demands the reduction of CO2 emissions. The optimization of the amount of cement in concrete can be achieved either by partially replacing it by additions or by reducing the binder content. The present work aims at optimizing the properties of concrete used in the production of reinforced concrete poles for electrical distribution lines, combining the maximization of compactness with the partial replacement of cement by fly ash, natural pozzolans, and electric furnace slags. Natural aggregates were also partially replaced by recycled ones in mixtures with fly ash. Two types of concrete were studied: a fresh molded one with a dry consistency and a formwork molded one with a plastic consistency. The following properties were characterized: mechanical properties (flexural, tensile splitting, and compressive strengths, as well as Young’s modulus) and durability properties (capillary water absorption, water penetration depth under pressure, resistance to carbonation, chloride migration, and concrete surface resistivity). The service life of structures was estimated, taking the deterioration of reinforcement induced by concrete carbonation or chloride attack into account. Results revealed that mixtures with fly ash exhibit higher mechanical performance and mixtures with fly ash or pozzolans reveal much higher durability results than the full Portland cement-based mixtures.

scholarly journals Mortars with CDW Recycled Aggregates Submitted to High Levels of CO2

2021 ◽  
Vol 6 (11) ◽  
pp. 159
Author(s):  
Ricardo Infante Gomes ◽  
David Bastos ◽  
Catarina Brazão Farinha ◽  
Cinthia Maia Pederneiras ◽  
Rosário Veiga ◽  
...  
Keyword(s):  
Large Scale ◽  
Mechanical Performance ◽  
Construction Materials ◽  
Environmental Benefits ◽  
Recycled Aggregates ◽  
Construction And Demolition Wastes ◽  
Short Period ◽  
Natural Aggregates ◽  
Cement Factories ◽  
Made In

Construction and demolition wastes (CDW) are generated at a large scale and have a diversified potential in the construction sector. The replacement of natural aggregates (NA) with CDW recycled aggregates (RA) in construction materials, such as mortars, has several environmental benefits, such as the reduction in the natural resources used in these products and simultaneous prevention of waste landfill. Complementarily, CDW have the potential to capture CO2 since some of their components may carbonate, which also contributes to a decrease in global warming potential. The main objective of this research is to evaluate the influence of the exposure of CDW RA to CO2 produced in cement factories and its effect on mortars. Several mortars were developed with a volumetric ratio of 1:4 (cement: aggregate), with NA (reference mortar), CDW RA and CDW RA exposed to high levels of CO2 (CRA). The two types of waste aggregate were incorporated, replacing NA at 50% and 100% (in volume). The mortars with NA and non-carbonated RA and CRA from CDW were analysed, accounting for their performance in the fresh and hardened states in terms of workability, mechanical behaviour and water absorption by capillarity. It was concluded that mortars with CDW (both CRA and non-carbonated RA) generally present a good performance for non-structural purposes, although they suffer a moderate decrease in mechanical performance when NA is replaced with RA. Additionally, small improvements were found in the performance of the aggregates and mortars with CRA subjected to a CO2 curing for a short period (5 h), while a long carbonation period (5 d) led to a decrease in performance, contrary to the results obtained in the literature that indicate a significant increase in such characteristics. This difference could be because the literature focused on made-in-laboratory CDW aggregates, while, in this research, the wastes came from real demolition activities, and were thus older and more heterogeneous.

scholarly journals Effect of Fly Ash on the Compressive Strength of Green Concrete

2020 ◽  
Vol 10 (3) ◽  
pp. 5728-5731 ◽  
Author(s):  
S. A. Chandio ◽  
B. A. Memon ◽  
M. Oad ◽  
F. A. Chandio ◽  
M. U. Memon
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Recycled Aggregates ◽  
Waste Materials ◽  
Partial Replacement ◽  
Equal Proportion ◽  
Standard Size ◽  
Green Concrete ◽  
Coarse Aggregates ◽  
Management Issues

This research paper aims at investigating the effects of fly ash as cement replacement in green concrete made with partial replacement of conventional coarse aggregates with coarse aggregates from demolishing waste. Green concrete developed with waste materials is an active area of research as it helps in reducing the waste management issues and protecting the environment. Six concrete mixes were prepared using 1:2:4 ratio and demolishing waste was used in equal proportion with conventional aggregates, whereas fly ash was used from 0%-10% with an increment of 2.5%. The water-cement ratio used was equal to 0.5. Out of these mixes, one mix was prepared with all conventional aggregates and was used as the control, and one mix with 0% fly ash had only conventional and recycled aggregates. The slump test of all mixes was determined. A total of 18 cylinders of standard size were prepared and cured for 28 days. After curing the compressive strength of the specimens was evaluated under gradually increasing load until failure. It is observed that 5% replacement of cement with fly ash and 50% recycled aggregates gives better results. With this level of dosage of two waste materials, the reduction in compressive strength is about 11%.

scholarly journals Influence of Partial Replacement of Micro-Silica by Fly-Ash on Strength Properties of Reactive Powder Concrete

2020 ◽  
Vol 9 (3) ◽  
pp. 2932-2937
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Fly Ash ◽  
Mechanical Performance ◽  
Cementitious Materials ◽  
Partial Replacement ◽  
Reactive Powder Concrete ◽  
Experimental Investigations ◽  
Reactive Powder ◽  
Micro Silica

Reactive powder concrete (RPC) is the ultra-high strength concrete made by cementitious materials like silica fumes, cement etc. The coarse aggregates are completely replaced by quartz sand. Steel fibers which are optional are added to enhance the ductility. Market survey has shown that micro-silica is not so easily available and relatively costly. Therefore an attempt is made to experimentally investigate the reduction of micro-silica content by replacing it with fly-ash and mechanical properties of modified RPC are investigated. Experimental investigations show that compressive strength decreases gradually with addition of the fly ash. With 10 per cent replacement of micro silica, the flexural and tensile strength showed 40 and 46 per cent increase in the respective strength, though the decrease in the compressive strength was observed to be about 20 per cent. For further percentage of replacement, there was substantial drop in compressive, flexural as well as tensile strength. The experimental results thereby indicates that utilisation of fly-ash as a partial replacement to micro silica up to 10 per cent in RPC is feasible and shows quite acceptable mechanical performance with the advantage of utilisation of fly-ash in replacement of micro-silica.

Mechanical performance of engineered cementitious composites incorporating recycled glass powder

2020 ◽  
Vol 47 (12) ◽  
pp. 1311-1319 ◽  
Author(s):  
Adeyemi Adesina ◽  
Sreekanta Das
Keyword(s):  
Fly Ash ◽  
Power Plants ◽  
Glass Powder ◽  
Mechanical Performance ◽  
Partial Replacement ◽  
Cementitious Composite ◽  
Engineered Cementitious Composite ◽  
Recycled Glass ◽  
Alternative Materials ◽  
Coal Power Plants

Engineered cementitious composite (ECC) is conventionally made up of high content fly ash (FA) combined with Portland cement (PC) as a binder. However, the growing call for sustainability is leading to continuous decommissioning of various coal power plants around the world thereby limiting the supply of fly ash available for ECC production. Therefore, it is of high importance to find alternative materials that can be incorporated into ECC as a partial replacement of the conventional binders. This experimental investigation was carried out to investigate the feasibility of incorporating glass powder (GP) as binder into ECC mixtures. The mechanical performance in terms of its compressive, tensile, and flexural properties was evaluated. Results from this study showed that 25% FA can be replaced with GP without any significant reduction in the mechanical performance of ECC mixtures. Microstructural investigations of the mixtures incorporating GP show good bonding between the cementitious matrix and the fibres.

Mechanical Performance and Durability of Fly Ash Recycled Aggregate Concretes

2012 ◽  
Vol 538-541 ◽  
pp. 1568-1572
Author(s):  
Valeria Corinaldesi
Keyword(s):  
Fly Ash ◽  
Mechanical Performance ◽  
Point Of View ◽  
Recycled Concrete ◽  
Recycled Aggregate ◽  
Engineering Properties ◽  
Sustainable Construction ◽  
Reinforced Concrete Structure ◽  
Fly Ash Concrete ◽  
Natural Aggregates

According to the concept of sustainable development, the environmental load of a building must be evaluated throughout its life cycle, from design to construction, maintenance or repair, demolition, and rubble disposal. Therefore, from a holistic point of view, sustainable construction means designing a reinforced concrete structure with proper durability during a specified service life. This paper discusses the effect of partial and full replacement of natural aggregates by recycled concrete aggregates (RCA) in a fly ash concrete. Engineering properties and durability performance have been examined for mixtures designed with various proportions of the RCA by mass. Results obtained showed that the addition of RCA lowers concrete performance, but the combined use of RCA and fly ash could allow to achieve adequate engineering properties and durability.

scholarly journals Developing a Sustainable Concrete using Waste Glass and Rubber for Application in Precast Pedestrian Slabs

2021 ◽  
Vol 7 (5) ◽  
pp. 786-803
Author(s):  
Asish Seeboo ◽  
Chetanand Choollun
Keyword(s):  
Plain Concrete ◽  
Mean Value ◽  
Partial Replacement ◽  
Sustainable Concrete ◽  
Durability Properties ◽  
Static Modulus ◽  
Fine Glass ◽  
Pre Treatment ◽  
Natural Aggregates ◽  
Static Modulus Of Elasticity

In this piece of research, n attempt was made to produce a sustainable concrete with the partial replacement of both fine and coarse natural aggregates with two different non-biodegradable wastes. The selected wastes were fine glass and shredded rubber tires. Fine glass passing through 4.75 mm BS sieve was utilised for the partial replacement of fine natural aggregates. Coarse natural aggregates were partially replaced with shredded rubber passing through 20 mm sieve and retained on 6.30 mm sieve. Several mixes with varying % of fine glass but with a fixed 10 % of shredded rubber were tested. Optimum fine glass content was determined to be in the order of 20 %. The resulting concrete exhibited lower plastic and hardened densities (2040 and 2117 kg/m3 respectively) in comparison to normal plain concrete. The static modulus of elasticity was found to be 18.3 GPa (mean value), while the splitting tensile strength was 2.37 MPa. The flexural strength showed a significant increase of 20.3% compared to the control mix. The results concluded that the concrete thus produced is a viable means of disposing of such non-biodegradable wastes (rubber and glass), thus reducing the loads at landfills. This new genre of concrete was produced at a lower cost than normal concrete because of the very low pre-treatment costs of the recycled wastes used. Furthermore, the properties tend to indicate that the concrete could be applied where lower strength and high durability properties are warranted. Hence precast slabs were made from the new design concrete and were tested along a stretch of a highly trafficable pedestrian walkway on the University campus. The slabs were continuously monitored for defects such as cracks, broken corners and slabs for a period of 24 consecutive weeks. After the test period it was observed that only 4 out of the 80 precast slabs had hairline cracks. Hence concluding the enhanced durability properties of the new design concrete. Doi: 10.28991/cej-2021-03091690 Full Text: PDF

scholarly journals Investigative Study of Partial Replacement of Cement with Bio-Cement, Fly Ash and Natural Pozzolans

2021 ◽  
Vol 12 (1S) ◽  
pp. 432-436
Author(s):  
Dr.Sarvesh, Et. al.
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Main Property ◽  
Partial Replacement ◽  
Self Healing ◽  
Split Tensile Strength ◽  
Conventional Concrete ◽  
Quality Properties ◽  
Natural Pozzolans ◽  
The Impact

Concrete is usually a combination of cement, coarse particles (aggregates and Sand) and water. It is used to design and improve the infrastructures.It is used to design and improve the infrastructures. Concrete has many advantages and disadvantage. The main property that is characteristic to a concrete’s workability is its compressive strength. Only through this single test, one can judge if cementing has been done appropriately. Possible advancements for development include the use of non-traditional and creative materials, and the reuse of waste materials with a specific end goal to replenish the absence of specific assets and to discover alternative ways to monitor the Earth..This investigation concentrate on Compressive strength, flexural and split tensile strength of Conventional Concrete (CC) and Class C fly ash remains with bio-cement and natural pozzolans to consider the impact of bio-concrete with blend extents of 0%,0.25%,0.5%,1% and 1.5% on quality properties. Moreover, effective self-healing usually occurred due to the use of polymers, microorganism and additional cementing material. It is the key issue to find out the self-healing efficiency’s effect to sealing the crack width successfully. And good resistance was observed during the bacterial chemical process against the freeze and thaw attacks.

scholarly journals Evaluation of Eco-Efficient Concretes Produced with Fly Ash and Uncarbonated Recycled Aggregates

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7499
Author(s):  
Miren Etxeberria
Keyword(s):  
Fly Ash ◽  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Hardened Concrete ◽  
Conventional Concrete ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Carbonation Resistance ◽  
Chloride Resistance ◽  
Natural Aggregates

The fabrication of conventional concrete, as well as remains from demolition, has a high environmental impact. This paper assessed the eco-efficiency of concrete made with uncarbonated recycled concrete aggregates (RCA) and fly ash (FA). Two concrete series were produced with an effective water/cement ratio of 0.50 (Series 1) and 0.40 (Series 2). In both series, concretes were produced using 0% and 50% of RCA with 0%, 25% and 50% FA. After analysing the compressive strength, and carbonation and chloride resistance of those concretes, their eco-efficiency based on the binder intensity and CO2-eq intensity was assessed. We found that the use of 50% uncarbonated RCA improved the properties of concretes produced with FA with respect to using natural aggregates. The concrete made of 25% FA plus RCA was considered the most eco-efficient based on the tests of compressive, carbonation and chloride properties with the values of 4.1 kg CO2 m−3 MPa−1, 76.3 kg CO2 m−3 mm−1 year0.5 and 0.079 kg CO2 m−3 C−1, respectively. The uncarbonated RCA improved carbonation resistance, and FA improved chloride resistance. It can be concluded that the use of 50% un-carbonated RCA combined with FA considerably enhanced the properties of hardened concrete and their eco-efficiency with respect to concretes produced with natural aggregates.

MECHANICAL PERFORMANCE OF ROLLER COMPACTED RUBBERCRETE WITH DIFFERENT MINERAL FILLER

2017 ◽  
Vol 79 (6) ◽  
Author(s):  
Musa Adamu ◽  
Bashar S. Mohammed ◽  
Nasir Shafiq
Keyword(s):  
Fly Ash ◽  
Flexural Strength ◽  
Silica Fume ◽  
Mechanical Performance ◽  
Fine Sand ◽  
Crumb Rubber ◽  
Partial Replacement ◽  
Fine Aggregate ◽  
Mineral Filler ◽  
Scrap Tires

The rate of waste tire generation globally continues to escalate due to increase in vehicle usage. Scrap tires continue to pose serious environmental, health and aesthetic problems. Due limitation in the recycling of scrap tires, one of the most viable solution is to used crumb rubber from scrap tire as partial replacement to fine aggregate in concrete industry. This is rationalized as the production of concrete hit more than 3.8 billion cubic meters annually, therefore, it could provide a solution on conservation of natural aggregate and as well as improve properties of concrete. However, the major setback in the use of crumb rubber in concrete is loss in strength.  In this paper, crumb rubber was used to partially replaced fine aggregate at 0%, 10%, 20% and 30% by volume in roller compacted concrete for pavement applications to produce roller compacted rubbercrete (RCR) to improve its flexural strength and ductility. Several trials were done to achieve the combined grading as recommended by ACI 211.3R, and finally a combination of 55% fine aggregate, 40% coarse aggregate and 5% fine sand as mineral filler was used. In order to mitigate the effect of strength loss, silica fume and fly ash were used to replace natural fine sand as mineral fillers. The Results showed that fresh density, compressive, splitting and flexural strengths decreases with increase in partial replacement of fine aggregate with crumb rubber. However using silica fume as a mineral filler was successful in mitigating loss in compressive, tensile and flexural strengths for up to 20% crumb rubber replacement level, while fly ash as a mineral filler mitigated loss in strength for up to 10% crumb rubber compared natural fine sand mineral filler. The flexural strength was found to increase with 10% crumb rubber for all type of mineral filler

Mechanical Performance of Asphalt Mixtures with Natural Aggregates and Recycled Aggregates for Surface Course

2014 ◽  
Vol 600 ◽  
pp. 657-666 ◽  
Author(s):  
Vagner da Costa Marques ◽  
Bismak Oliveira de Queiroz ◽  
Diego Meira de Lacerda ◽  
Antônio Marcos de Araújo Gouveia ◽  
Ricardo Almeida de Melo
Keyword(s):  
Solid Waste ◽  
Environmental Impacts ◽  
Mechanical Performance ◽  
Waste Recycling ◽  
Asphalt Mixtures ◽  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Asphalt Mix ◽  
Natural Aggregates ◽  
Marshall Stability

The recycled aggregates of construction and demolition solid waste can be used on pavements to decrease environmental impacts in cities. Thus, this study aimed to compare the mechanical performance of asphaltic mixtures made with natural aggregates and concrete recycled aggregates for surface course of pavements. The materials were collected in an asphalt mixing plant and in a construction and demolition solid waste recycling plant located in João Pessoa/PB, Brazil. The Marshall asphalt mix design was chosen to determine optimum asphalt content and evaluate mechanical performance of asphaltic mixtures. The asphalt mixtures specimens were composed of natural aggregates, and afterwards of recycled aggregates with percent contents of 25, 50 and 100. The optimum asphalt contents were 5.7 and 7.5%, Marshall stability of 1,070 and 790 Kgf, flow of 6.2 and 5.7 mm for natural aggregate asphalt mixtures and asphalt mixtures with 25% recycled aggregates, respectively. Moreover, percent air voids and percent voids filled with asphalt met the Brazilian DNIT: ES 031/2006 specified standard. However, the asphalt mixtures with 50 and 100% recycled aggregates did not meet the specified standard. Therefore, it was concluded that the replacement of natural aggregates with 25% recycled concrete aggregates in asphalt mixtures can be technically viable to build asphalt surface course on pavements, besides lowering pavement costs and decreasing environmental impacts.

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