Evaluation of Hardened Property Variations in M25 And M30 Concrete with Different Types of Coarse Aggregates

This study aims to find out how the type and size of materials used in concrete impact its physical properties. In our experiment, we will use three types of aggregate material crushed and river aggregate in two different sizes: 20mm, and 10mm. We will mix these with regular cement to hold everything together. We will make concrete mixtures for two quality levels, M25 and M30, using each type and size of material. Next, we will test samples of these mixtures to see how much compressive strength they can handle after 7 and 28 days. Aggregates, which are often overlooked, play a crucial role in concrete, forming its foundation. These inert granular materials, including sand, gravel, and crushed stone, combine with water and a binding agent to create concrete. Knowledge of aggregate behaviour aids engineers in preparing concrete that satisfies definite requirements such as high strength, durability or sustainability. The results of these studies will help us understand how different types and sizes of aggregates influence the physical properties of concrete. By comparing these factors, we aim to determine the most suitable aggregate type and size for each concrete strength level.

Aggregates are crucial parts of concrete that affect both its physical properties and how well it works. These small pieces, such as sand, gravel, broken stone, and reused concrete, take up most of the space in concrete and help it to be strong enough to handle heavy weights and strong pressures. By filling in the space, aggregates reduce the amount of cement needed, making concrete cheaper to make without lowering its quality. The shape, size, and surface of the aggregates also affect how easy it is to work with concrete; particles that are well-mixed create a tight and interlocking structure that makes it easier to handle and place the concrete. The type of aggregates affects how long concrete lasts, because harder and more durable types increase its ability to withstand weather conditions like freeze-thaw cycles and exposure to chemicals. Additionally, aggregates play a role in how concrete handles heat and temperature changes. They manage the heat produced during the setting process and affect how the material reacts to temperature shifts. The way aggregates absorb and hold moisture influences the mix's water-to-cement ratio and the curing process, which is crucial for reaching the right level of strength. Moreover, aggregates determine the density and weight of concrete, offering options like lightweight and heavyweight versions for various applications. In summary, choosing the right aggregates and their amounts is crucial for achieving a mix that is strong, durability, workability, and cost-effectiveness, which is key to the performance and lifespan of concrete structures.

Abdullahi. M, (2013) [5]. The amount of water mixed with cement, how tightly the concrete is packed, and the characteristics of the rocks used, like their size, shape, and how strong they are, all affect how strong concrete can be when squished. Research shows that the kind of big rocks used in making concrete greatly affects its overall strength. Among all the rocks tested, basalt is the strongest, even stronger than limestone and gravel. A study by Wu et al. in 1997 found that concrete made with crushed quartzite was the strongest, followed by concrete made with river gravel and crushed granite. The number of rocks and how they are sized also affects the strength of the concrete, with crushed quartzite recommended for the strongest concrete. Theophilus Yisa Tsado (2013) [18]. Concrete, a widely used material, is composed of a mix of aggregates, cement, and water. The type of aggregates plays a crucial part in determining the properties of concrete. This review focuses on how the size of the coarse particles affects the strength of concrete, particularly its ability to withstand compression. The research looks at how three different types of rock aggregates affect concrete strength: volcanic rock (crushed granite), sedimentary rock (limestone), and metamorphic rock (marble). Crushed granite is found to be the strongest due to its toughness, with limestone being the next strongest, and marble being the least strong. The research also considers how the physical characteristics of the aggregates, such as the amount of empty space and the number of tiny holes, influence how much water the concrete can absorb and how long it lasts.

Cement

The research used a specific type of cement called ordinary Portland cement 53 grade, following the guidelines of IS: 12269 − 1987. The details about the cement's characteristics can be found Normal consistency 32%, Specific gravity 2.87, Initial setting time 42 minutes, Final setting time 178 Minutes, Fineness 1.8% and Soundness 1 mm.

Fine Aggregate

The sand used was river sand obtained locally, which was clean and did not contain any organic materials. It met the standards set by IS 383–1970. The characteristics of this sand, categorized as Zone-II, include a specific gravity of 2.63, water absorption of 1.7%, and a fineness modulus of 2.86, as detailed in Table 1.

Table 1: Sieve Analysis of Fine aggregate as per (IS CODE 383:1970 PART-I).

Coarse Aggregate

The large stones used in this study met the standards set by IS: 383–1970. We selected crushed, rough stones from a nearby MS Stone crusher, Himachal Pradesh, India for our experiment. We picked 20 mm stones that were clean and free from harmful substances. The findings for the aggregates are: a specific gravity of 2.7, water absorption of 0.8%, and a fineness modulus of 6.032 and 6.36 for 20mm, 10mm, (refer to Table 2,3).

Table 2: Sieve Analysis of 20mm Coarse aggregate as per (IS CODE 383:1970 PART-I).

Table 3: Sieve Analysis of 10mm Coarse aggregate as per (IS CODE 383:1970 PART-I).

Fly Ash

The fly ash used in this research was sourced from a single company, Mahavir Crusher and was stored carefully to maintain its quality. The characteristics of the fly ash match the standards set by the Indian Standard IS: 1727–1967, which can be specific gravity 2.32 and fineness modulus 1.54 (refer Table 4).

Table 4: Sieve Analysis of Fly Ash as per (IS CODE 383:1970 PART-I).

Admixtures

To improve the workability of the concrete mixes, we used an additive called Conplast SP 430 (DIS). Adding fibers and more fly ash typically makes concrete harder to work with. To ensure it can be used practically, we added the right number of admixtures to the mix. Here are the details for Conplast SP 430 (DIS): It's a brown liquid that you mix into the concrete. It has specific gravity between 1.20 and 1.22 when it's 30 degrees Celsius. You should use between 0.6 and 1.5 liters of this additive for every 100 kilograms of cement.

Water

The standard IS: 456 (2000) suggests that the water for mixing and curing concrete should be clean and free from anything that could damage the concrete or steel. The water should have a pH of at least 6 to keep the concrete strong and stable. In this research, we use tap water that meets these standards for both mixing and curing. Using this water helps the concrete mix to be of good quality and last longer, making sure it hardens correctly and stays strong for a long time. Good water quality is very important to prevent bad reactions that could weaken the concrete's structure.

Experimental Details

Mix Design

In concrete technology, creating a design mix means figuring out the right amounts of cement, water, and aggregates (both fine and coarse), along with any additives, to make concrete that has the qualities we want. This way, we ensure that the concrete mix meets the needed standards for strength, ease of use, long-lasting quality, and other performance criteria. To make a good mixture, we started by adding a special chemical that helps the concrete flow better. Then, we figured out how much of each ingredient to use, following the Code IS 10262 − 2019. We made two types of concrete, called M25, and M30 Grade, using coarse aggregate of different sizes and a mix of water and cement where there is less water than cement. Mix design proportion shown in Table 5 and Table 6 as per the code.

Table 5: Design Mix for M25 Grade.

Table 6: Design Mix for M30 Grade.

Test Specimens

First, the dry materials (cement, fine aggregate and Coarse aggregate) were mixed together for two minutes. Next, water and special chemicals were added, and the mixing continued for another two minutes. To make sure everything was mixed well, the whole process took no more than five minutes. After mixing, a tool that shakes like a needle was used to pack the material tightly before making the test pieces. After one day, the test pieces were taken out of their moulds and put into water tanks to stay there until it was time to test them, which could be either seven or twenty-eight days later.

Tests on Concrete

Workability Test: The ease of handling fresh concrete mixtures was studied using a slump test, which follows the guidelines of IS 1199–1959.

Compressive Strength: In this investigation, we look at 150x150x150mm cube samples following the rules of IS 516–1969. After being kept in water for 7 and 28 days, these cubes were taken out and compressed to see how strong they are. We tested all three cubes and used the average result as the main strength number.

Compressive Strength

The strength of concrete with grades M25 and M30 was checked after 7 and 28 days using two types of stones (10 mm and 20 mm). The findings show that how well the concrete works changes based on the type of concrete and the type and size of the stones used. For concrete with a grade of M30, the 20 mm crushed aggregate showed the highest compressive strength after 7 days, which was 28.13 MPa as shown in Table 7 and Figure 1. It also did well after 28 days, reaching a strength of 35.21 MPa. However, the highest strength after 28 days was achieved with 10 mm river gravel, which was 37.1 MPa, indicating that river gravel might provide better long-term strength for M30 concrete.

Figure 1: Compressive Strength for M30 Grade Concrete.

Table 7: Compressive Strength for M30 Grade Concrete.

In the case of M25 grade concrete, the 20 mm crushed aggregate performed excellently, especially after 28 days, when it reached the highest compressive strength of 38.31 MPa among all M25 samples as shown in Table 8 and Figure 2. Both 10 mm and 20 mm river gravel aggregates had lower compressive strengths compared to crushed aggregates, with 10 mm river gravel only reaching 28.24 MPa after 28 days.

Figure 2: Compressive Strength for M25 Grade Concrete.

Table 8: Compressive Strength for M25 Grade Concrete.

The study on how strong M25 and M30 concrete can get after being compression helps us understand how the type and size of rocks used in the concrete affect its strength.

Aggregate Types

Concrete made with crushed rocks usually becomes stronger for both M25 and M30 grades. This is very clear in M25 concrete, where the crushed rocks that are 20 mm in size made the concrete the strongest after 28 days (38.31 MPa). Rocks from rivers, though not as strong as crushed rocks in M25 concrete, have shown good results in M30 concrete, especially the 10 mm size rocks, which made the concrete the strongest after 28 days (37.1 MPa).

Aggregate Size

For both types of concrete, using 20 mm aggregates results in greater compressive strength compared to 10 mm aggregates, particularly when the aggregates are crushed. However, with M30 grade concrete, 10 mm river gravel showed increased strength after 28 days, indicating that smaller aggregate sizes might work better in certain conditions.

Concrete Grade

M30 grade concrete is stronger than M25, which makes it a good choice for projects that require more robust structural support. The type and size of aggregate used can significantly affect the final strength of the concrete. Crushed aggregates work well with M25, while river gravel might provide benefits for M30.

Author Contribution

A- wrote the main manuscript text and B- reviewed the manuscript.

Competing Interests

No competing interests reported.