Strength Of Coarse Aggregate Research Articles

Impact of Multiple Recycling on the Strength of Coarse Aggregate

Concrete structures are integral parts of modern civilization. Every year a huge amount of concrete waste is generated due to demolition of old concrete structures for replacing them with new high-rise buildings or other structures, which consequently, increasing the environmental loads. Recycling of demolished concrete is found to be an effective way for sustainable development which can also minimize the disposal problem associated with concrete waste. Recycling of demolished concrete to produce usable aggregate, therefore, has drawn attention of researchers in the field of concrete technology. However, most of the studies in this field are focused on 1st generation recycled aggregate. Effect of multiple recycling on the properties of aggregate is merely studied. In this study, the effect of multiple times recycling on aggregate strength is observed. Strength of aggregate is evaluated in laboratory by Aggregate Crushing Value (ACV) test and Aggregate Impact Value (AIV) test after each generation of recycling. The ACV and AIV values of 1st generation, 2nd generation and 3rd generation recycled aggregates are compared with the natural source aggregate. Strength degradation after each stage of recycling is recorded. In addition, the test results of 1st generation, 2nd generation and 3rd generation recycled aggregates are interpreted, investigated and compared with standard requirement to outline their corresponding applications. ACV value for natural aggregate is found to increase by 2.5% after 1st stage of recycling and it increased by 4.64% and 6.79% after 2nd and 3rd stage of recycling respectively. On the other hand, AIV value for natural aggregate is found to increase by 7.04% after 1st stage of recycling and it increased by 10.35% and 12.47% after 2nd and 3rd stage of recycling respectively. The study reveals that the strength of 1st generation recycled aggregates is quite similar to that of natural aggregate and can be used for concreting in general purposes. 2nd generation recycled aggregate cannot be used in the production of concrete in heavy duty floor but can successfully be used in concrete for wearing surface and 3rd generation recycled aggregates are too weak for road surfacing.

Investigating the Effects of Coarse Aggregate Physical Properties on Strength of C-25 Concrete

The strength of concrete mostly depends on the strength and properties of coarse aggregate since the major volume of concrete was covered by coarse aggregate. The physical properties of coarse aggregates do grossly affect the workability and structural performance of concrete. This study considered the effects of physical properties of coarse aggregate on properties of concrete and the difference in strength of concrete made from four different types of coarse aggregates namely crushed basalt, crushed marble, river graver and surface gravel which were collected from different areas near to Nekemte town. For each types of collected coarse aggregate their physical properties are determined by performing necessary laboratory tests to attain the objective of the study. For proportioning of concrete making materials the ACI concrete mix design was followed. Total of 36 cubes and 12 beam molds were casted for determination of compressive strength flexural strength of C-25 concrete made from the four aggregate samples. The results indicate physical properties and types of coarse aggregate have effects on the strength of concrete. The four coarse aggregate samples have different physical properties and produced concrete having different compressive and flexural strength. Thus, it concludes, the compressive and flexural strength of concrete was greatly influenced by the physical properties and strength of coarse aggregate.

A Review paper on the Effect of different types of coarse aggregate on Concrete

The strength of concrete mix is dependent on many parameters like cement type, coarse aggregate and the interface between aggregate and mortar. However, generally the coarse aggregate is treated as an inert material and only its physical properties like shape, size, water absorption and specific gravity are studied. Whereas, as we increase the quality of mortar mix, the strength of coarse aggregate also comes into picture. In case of high performance concrete, the type of coarse aggregate used has a great influence on the strength and elasticity modulus of concrete. For high strength concrete with compressive strength above 40 MPa, which are generally cast with water-cement ratio less than or equal to 0.4, the strength of mortar and the interfacial bond strength may be comparable to the strength of aggregate. This paper presents a comprehensive review of the past research work done on the effect of using different types of coarse aggregate on various properties of concrete mix like its compressive strength, tensile strength and elasticity modulus.

Recycled Aggregate Performance Experiment Study on Basis of Saturated Surface Dried Crush Value Index

Crush value index is a key parameter for measurement of coarse aggregate strength performance. In this paper the eight group of crush value index are tested for the recycled aggregate used of waste concrete which is gathered from three different remove construction plants. The experiment analysis result is shown that the crush value of recycled aggregate is greater 2.5 times than natural aggregate. Meanwhile, compared with air dried condition, the crush value index of saturated face dried condition is from 7.22% to18.2%. Furthermore the recycled aggregate can be suitable to make concrete requirement which compression strength grade is C35 and lower than C35 in China. In the experiment, comparative analysis is found that the RA-10 aggregate compressive strength is slightly from 2.06% to 8.7%. Those which are higher limit value of standard for test method of mechanical properties on ordinary concrete and the divergence are less than 10%. Consequently the recycled aggregate can be used for concrete, and its compressive strength is also fundamentally satisfied for requirement of concrete compressive strength.

Determination of the dividing strength and its relation to the concrete strength in lightweight aggregate concrete

As concrete is considered to be a composite material consisting of mortar and coarse aggregate, its strength depends on the mortar strength and coarse aggregate strength. During the strength development stage of a lightweight aggregate concrete, a critical condition, under which the type of stress distribution changes, occurs as the values of the modulus of elasticity of the lightweight aggregate and mortar become the same. The concrete strength corresponding to this instant is named ‘Dividing Strength (F G)’ by Weigler & Karl ( Stahlleichtbeton, 1972, pp. 38–43) [1]. A series of specimens consisting of 252 concrete cylinders (100φ × 200 mm) and 252 mortar cubes (50 × 50 × 50 mm) were made and subjected to compression tests. From the obtained mortar-concrete strength relationship, we were able to identify a dividing strength for a lightweight aggregate concrete made with a 0.4 water cement ratio. The test data also show that both particle density and particle sizes of lightweight aggregate are governing factors for the dividing strength. The concept of a dividing strength can be utilized to optimize a mix design for lightweight aggregate concrete. For instance, concrete that has a designed compressive strength much greater than its dividing strength may consume too much cement and resulting to wasteful cement consumption.

Synergetic roles of concrete ingredients in strength development

Concrete is basically a heterogeneous material made up of ingredients with distinct physical and mechanical properties. As a result, the presence of interphases is inevitable. In the processing of concrete, fresh and hardened states are the two distinct stages. In the fresh state, the presence of inert constituents in the cement mortar matrix only dilutes the overall potential of concrete to flow. In the hardened state the synergetics play a dominant role in strength development. When the strength of coarse aggregate is far higher than the strength levels for which the matrix or concrete is processed, interphase bonding plays a dominant role on the strength. When the matrix strength is comparable to that of the aggregate strength, in contrast, the concrete strength is affected by the aggregate strength. Besides these aspects, the effects of the size and the surface texture of coarse aggregates have also been analysed.

Estimation of Coarse Aggregate Strength in High-Strength Concrete

Estimation of Coarse Aggregate Strength in High-Strength Concrete