RECYCLED CONCRETE AGGREGATE (RCA) FOR THE USE IN CONSTRUCTION: GENERAL REVIEW (original) (raw)

Use of Recycled Concrete Aggregate in Construction: An Overview

– Recycled aggregates have germinated towards a valuable preference for virgin aggregates. RA is created from concrete rubble which has undergone years of services; the resulting RAC carries the weakness of lower density, higher water absorption & higher permeability that limit them to lower grade applications. In order to achieve the best ecology-to-quality ratio considering materials, befitting selections should be made. Concrete mix proportioning is enhanced in order to maximize the usage of C&D waste without the reduction of mechanical & enduringness properties. The experimental follow up were carried out by using detailed strength & durability related tests are explained here for different fusion of recycled aggregates with virgin aggregates. The compressive strength of RAC is found to be higher than the strength of virgin concrete. RAC is in proximity to virgin concrete in terms of split tensile strength, flexural strength and wet density. The slump of RAC is depressed and that can be regenerate by using full substituting of SSD RCA aggregates to the VA. At last it is confirmed that the use of RCA is likely a possible call for structural use. Index Terms-Recycled concrete aggregate (RCA), recycled aggregate (RA), saturated surface dry (SSD), coarse aggregate (CA), virgin (natural) aggregate (VA), C&D.

A Review Paper on Use of Recycled Concrete Aggregates in Concrete Manufacturing Process

Construction industry generates large amount construction & demolition waste. This waste may be in the form of debris & building materials such as broken bricks, mortar, concrete, steel. At the same time foundry industry also generates large amount of waste sand. The foundry sand is sand used for the formation of moulds essential in the casting process. After the completion of its usefulness, it is dumped in open areas or low laying areas.The waste from construction & demolition are also dumped in open land & low laying areas. This process disturbs the environment & pollutes the ground water (SayeedJaved, 1992). The reuse of this waste will not only reduce the cost of disposal along with land requirement but also be useful in environment by conserving the use of natural aggregate. Concrete is the world's second most consumed material after water, and its widespread use is the basis for urban development. It is estimated that 25 billion tonnes of concrete are manufactured each year. On the other hand over 1 billion tonnes of construction and demolition waste (C&DW) is generated every year worldwide. Crushed concrete is available nowadays in large quantities, which also results from the demolition of old structures and waste concrete from new structures. Every year, it is estimated that 2% to 10% (average of 5%) of the estimated ready mixed concrete produced is returned to the concrete plant which is also of great concern to dispose off. The use of the recycled aggregates created from construction and demolition waste in new construction has become more important over the last two decades. Waste minimization and reducing the burden on landfills is a global issue. Extensive research has been carried out worldwide on the use of recycled aggregate in concrete. This includes substantial research reports by WRAP4, NRMCA5 and RILEM6. Globally the concrete construction industry has taken a responsible attitude to ensuring its natural resources are not overexploited. The reuse of hardened concrete as aggregate is a proven technology-it can be crushed and reused as a partial replacement for natural aggregate in new concrete construction. Recycling construction waste is vital both in order to reduce the amount of open land needed for land filling and to reduce depletion of raw materials. Recycling or recovering concrete materials has two main advantages-it conserves the use of natural aggregate and the associated environmental costs of exploitation and transportation, and it preserves the use of landfill for materials which cannot be recycled. Many attempts to develop high-grade uses of construction waste, i.e., as aggregate for the manufacturing of new concrete, are made in last few decades. A decrease in the compressive strength was generally observed in all concretes in which the natural coarse aggregate was replaced with recycled aggregate prepared by the crushing of old concrete. In the current paper we are going to study the feasibility of Recycled Aggregate in concrete manufacturing when it is blended with different proportions of fly ash and admixtures. We are going to study strength characteristic of concrete made with optimum proportions of ingredients. The study will give idea for the effective use of waste concrete which benefits sustainable development by reducing the necessity of land required for dumping waste concrete. " II. LITERATURE REVIEW " They conducted an experimental investigation to study the mechanical as well as micro structural properties of recycled aggregate concrete (RAC) exposed to elevated temperature.

A Review Paper on Recycled Aggregate Concrete

2021

As we all know that natural resources are being depleted and are in a very limited amount, recycle of Construction & Demolition materials play a vital role in preventing these natural resources. There are various methods of recycling construction wastes which are being used throughout the world in the past decade. Waste concrete is the primary component which will replace the conventional concrete (Natural Aggregates). There are however some limitations in the use of RAC. This review paper focuses on the known benefits of both conventional and recycled aggregates. This technique will definitely reduce the construction cost and at the same time it protects the environment. The different properties of RAC affects the mix design and also the hardened properties of the resulting concrete, when the RAC which replaces the natural aggregates exceeds the limit (33%). This paper represents the evaluation of the different research paper on the topic of RAC. The study found that if we replace ...

Use of Recycled Concrete Aggregate in Construction

– Recycled aggregates comprised of crushed, graded inorganic particles processed from the materials that have been used in the constructions and demolition debris. This study aims to develop the best economic solution by use of that demolition debris as recycled aggregate in structural concrete to reduce the environmental impact, the main objective of this paper is to investigate the hardness properties of Recycled Aggregates & Recycled Concrete Aggregate including abrasion test, impact value test & water absorption test on aggregates while slump, compressive strength, tensile strength & modulus of elasticity on fresh & hard concrete, which will give a better understanding on the properties of concrete with recycled aggregates, as an substitute material to virgin coarse aggregate in structural concrete. To determining the above properties of the recycled aggregate by studying the influence of limited percentage of recycled aggregate in concrete. The Laboratory trials were conducted with the aggregate size of 10-20mm, there were total of six batches of two concrete mixes M30 with 0.42 w/c & M20 with 0.5 w/c, consist of 00%, 40% & 60% of recycled aggregate replacement. The workability of concrete will be decreased as the amount of recycled aggregate increased but in the end, is considerable in the mix as it is still under the limits. This was evaluated through standard slump test. For strength characteristics, the results showed a gradually decreasing in modulus of elasticity, tensile strength, compressive strength as the percentage of recycled aggregate used in the specimens increased but at last most of the results were satisfactory & under the limits.

ASSESSMENT OF RECYCLED CONCRETE AGGREGATE (RCA) USAGE IN CONCRETE

Recycling concrete is a significant step towards eco-friendly construction practices. The use of recycled concrete aggregates in new structures provides a sustainable development. Initially, recycling of demolition waste was first carried out after the Second World War in Germany and henceforth, there have been reduction in the quantity of construction and demolition waste; and at the same time, it lessened the depletion of natural resources by providing an alternative. There have been recorded cases of application of recycled aggregate(RA) in a large number of construction projects of many European, American, Russian and Asian countries. The test results of ductility and the stiffness of beams with RA are equal or higher than those with natural aggregate. However, concrete made with recycled concrete aggregates exhibits different engineering properties. This difference is mainly due to the attached mortar paste on recycled concrete particles. Recycled aggregates have been found to have high water absorption capacity, which affects various properties mainly mechanical performance of the resulting concrete mix. Based on previous research, this paper presents a comprehensive overview of the recycled concrete material characteristics and the effect of using recycled concrete material on the mechanical properties, the durability properties and structural performance of concrete so as to help relevant units and staffs in the practical work.