Properties of Concretes with Natural Aggregate Improved by RCA Addition

Abstract

We can observe the growing tendency of usage of recycled concrete aggregate (RCA). Changes in waste materials management rules will result in necessity of more common reutilization of materials from demolished concrete structures. Thus new fields of RCA application and new ways of its utilization in concrete manufacturing are still being looked for. Research presented in the paper has been conducted to examine two methods of improving poor gradation of natural aggregate (NA) using RCA. The NA that did not fulfill requirements of gradation had been chosen. It consisted of ca. 75% of 2-4 mm fraction. In the first method a part of NA was replaced with 2-16 fraction of RCA of low quality. In the second method also a part of NA was replaced this time with 4-8 mm and 8-16 mm fractions of good quality RCA. The amount of replacing fractions was precisely calculated in order to fit optimal gradation curve. Quality of the gradation was measured with so called gradation index. Mechanical properties of researched concretes was tested as well as some of their properties related to durability. It can be stated, on the basis of the results, that both methods improve most of the vital concrete properties.

The mechanical properties of brick containing recycled concrete aggregate and polyethylene terephthalate waste as sand replacement

“…Cement and sand bricks are a type of bricks that is commonly used in low and medium cost housing development and other commercial constructions in Malaysia since it is easy to produce and cheap [1]. However, there is an issue in producing these materials especially in developing areas where manufactures find it difficult to locate adequate sources of natural cement and aggregate supply [2][3].…”

Eggshell powder as partial cement replacement and its effect on the workability and compressive strength of concrete

“…Concrete is a man-made construction and building material which is comprised of binder (cement), aggregates (fine and coarse) and water. It has been estimated in a report that the concrete industry utilizes 1.5 billion, 20 billion and 0.8 billion tons of cement, aggregates and water respectively every year (Kubissa et al, 2015). Though cement plays a vital role in the manufacturing of concrete, it has risen environmental concerns.…”

Sand Cement Brick Containing Recycled Concrete Aggregate as Fine-Aggregate Replacement

“…Cement and sand brick is easy to make and inexpensive to produce [1]. However, an issue was production cost of sand cement brick using natural sources, especially in developing areas where manufacturers find it difficult to locate adequate sources of natural aggregate supply.…”

“…However, an issue was production cost of sand cement brick using natural sources, especially in developing areas where manufacturers find it difficult to locate adequate sources of natural aggregate supply. Therefore, the price of natural source such sand has increased, which in turn affected pricing of sand cement bricks [1][2]. Nowadays, many studies focus on the use of waste material in the production of brick concrete.…”

“…Concrete with RCA at 25% to 50% replacements of sand and aggregates presented sufficient tensile performance compared to normal strength concrete [9][10]. Wojciech et al [1] claimed that the higher tensile strength of mortar containing fine aggregate is due to the water absorption capacity which is develops a siginificant interfacial bonding between aggregate and matrix. Matias et al [10] mentioned that the increase in hardened strength is due to the rough surface of recycled fine aggregate which provides better adherence to concrete matrix.…”