The compressive strength of concrete is an important consideration when building with it. This indicator shows us how much weight concrete can support before cracking or deforming. Whether you’re a novice DIYer or a seasoned engineer, everyone involved in construction needs to understand compressive strength.

Thus, what is the true meaning of design compressive strength? In short, it’s the highest stress that concrete can withstand without compromising its structural integrity. In order to guarantee the safety and durability of structures such as buildings, bridges, and roads, this value is established by testing samples.

Selecting the appropriate mix for a given project is made easier when one is aware of the concrete’s compressive strength. Using the appropriate type of concrete can make all the difference in the long run, as different applications call for different strengths. Whether you’re building a skyscraper or pouring a driveway, knowing this indicator will help you make sure your project satisfies safety regulations and endures for many years.

To put it briefly, the design compressive strength of concrete is an important metric that affects how well a construction project performs overall. Understanding its importance will enable you to make decisions that result in safer, better structures.

One of the most important indicators used by engineers to assess how much load concrete can safely support without failing is the concrete’s design compressive strength. It is crucial to comprehend this strength in order to guarantee the longevity and safety of structures, including bridges and buildings. Buildings can be made stronger and more dependable by selecting the right mix and materials with the knowledge of the proper compressive strength. To put it briefly, this indicator is essential for guiding the design process and averting structural problems later on.

- Definitions
- Axial compression. Calculations and values
- Methods for determining strength using control samples of concrete
- Destructive testing of concrete
- Non-destructive testing
- Video on the topic
- Strength of Materials Tension-compression diagram (lecture)
- Axial p.-szh. statically indeterminate problems Lesson #6 Topic #1 Strength of materials
- OSK lecture 2. Reinforced concrete structures
- Strength of materials. Lecture: calculation of tensile and compressive strength
- Height of the compressed zone of concrete of bending elements
- Calculated resistance of foundation soils. Assessment of settlement of columnar foundations
- SF. Deformative properties of concrete – open webinar
- Monolithic floor. Calculation of bending

## Definitions

Its load-bearing capacity is primarily described by its strength. The compression limit, which is the maximum load limit at which sample failure happens, determines it. And when using it, this is the primary indicator that is considered.

The determined resistance serves as a gauge for the material’s resistance to loading effects. It is closely related to regulatory indicators of compression resistance and utilized in design calculations.

They only paid attention to material brands up until the 2000s, when they were recognized as a calculated indicator. However, as per recently released technical documents, each brand was given a new standard for adhering to sample compressive loads.

It was discovered in lab settings, approved by experts, and included in SP 52–101–2003. This technical document states that the axial compression normative resistance of the material is a compression class with 95% security. According to the condition, only 5% of the tested cases can deviate from the predetermined indicators, and it is carried out in 95% of them.

However, even this small percentage demonstrates how unreasonable the risk is when using average design indicators in design. Additionally, selecting the lowest value will result in an increase in the structure’s or product’s cross-section, which will have an impact on the excessive use of energy and financial resources.

The image below displays the standard resistance values as per SP 52-101-2003.

Tensile strength is another term that exists. This material can withstand much higher tensile loads by nature. For this reason, it is reinforced in foundations, thick floor screeds, and other products made of reinforced concrete.

The compression indicator is used first when computing. In theory, compressive static or dynamic effects are what cause heavy loads to be experienced by any product or structure. However, when designing, resistance to bending effects is taken into consideration. Use the class correspondence table in such situations.

Table 6.7 from SP 63.13330.2012 SNiP 52-01-2003 details the resistance grades to stretching and compression.

Type |
Concrete |
Normative resistance MPa, and design resistance for limit states of the second group and MPa, with a material class for compressive strength |
|||||||||||||||||||||

B1.5 | AT 2 | B2.5 | B3.5 | AT 5 | B7.5 | AT 10 | B12.5 | B15 | IN 20 | B25 | B30 | B35 | B40 | B45 | B50 | B55 | B60 | B70 | B80 | B90 | B100 | ||

Compression axial tension | Heavy, fine-grained and straining | — | — | — | 2.7 | 3.5 | 5.5 | 7.5 | 9.5 | eleven | 15 | 18.5 | 22 | 25.5 | 29 | 32 | 36 | 39.5 | 43 | 50 | 57 | 64 | 71 |

Easy | — | — | 1.9 | 2.7 | 3.5 | 5.5 | 7.5 | 9.5 | eleven | 15 | 18.5 | 22 | 25.5 | 29 | — | — | — | — | — | — | — | — | |

Cellular | 1.4 | 1.9 | 2.4 | 3.3 | 4.6 | 6.9 | 9.0 | 10.5 | 11.5 | — | — | — | — | — | — | — | — | — | — | — | — | — | |

Axial tension | Heavy, fine-grained and straining | — | — | — | 0.39 | 0.55 | 0.70 | 0.85 | 1.00 | 1.10 | 1.35 | 1.55 | 1.75 | 1.95 | 2.10 | 2.25 | 2.45 | 2.60 | 2.75 | 3.00 | 3.30 | 3.60 | 3.80 |

Light | — | — | 0.29 | 0.39 | 0.55 | 0.70 | 0.85 | 1.00 | 1.10 | 1.35 | 1.55 | 1.75 | 1.95 | 2.10 | — | — | – | – | – | – | – | – | |

Cellular | 0.22 | 0.26 | 0.31 | 0.41 | 0.55 | 0.63 | 0.89 | 1.00 | 1.05 | – | – | – | – | – | – | – | – | – | – | – | – |

The strength of the cut made during the coat determines the correlation indicators’ resistance to compression.

Note: The most widely used indicator in the material design is the B25 compression resistance.

## Axial compression. Calculations and values

It is important to remember that class (B) directly depends on its average strength R, MPa, when performing computations. As a result, the following equation is applied:

When t is the security class that is part of the design, B = R (1−tV) usually takes the value 0.95, correspondingly t = 1.64; V is the strength variation coefficient. 1 is a constant.

The average strength is determined by taking the standard coefficient V = 13.5% (0.135) and dividing the result by B / 0.778.

When various types of reinforced concrete structures are computed, it becomes a different story. The exact calculation of the zone’s boundary height is done with great care. It expresses the height at which the tensile reinforcement and the compressed material’s stresses simultaneously reach their maximum values prior to destruction. The section can only be deemed normally reinforced in this scenario.

As per SNiP 2.03.01–84, the zone formula for height is as follows:

In this instance, a specific product is utilized based on the relative height of this zone (table). Regulatory documents contain them, and computations can be made using the data. In essence, the material provided provided a brief explanation of the concepts of the compression zone and resistance to axial compression.

## Methods for determining strength using control samples of concrete

Now that we know a material’s resistance to compression, let’s look at the primary techniques for identifying this indicator.

### Destructive testing of concrete

Typically, compression testing is done on verified equipment in accredited construction laboratories. A press is the main tool you’ll need.

Test samples, a caliper, and accurate laboratory scales are also required. The latter are made ahead of time from the necessary batch. The typical form is a cube with 10 cm sides. Technical documents state that one batch uses three to five samples.

Suggestions. To ascertain whether the density, weight, and design grade of the material are in compliance, they must first be prepared by washing them to remove any dirt and then weighing them. You can determine the appropriate level of stability with 95% certainty if these values are normal.

When the press is turned on and the sample is positioned with its edges perfectly flat, testing can start. The ultimate compression is the highest load at which the sample started to degrade.

The results of testing each of the chosen samples are used to determine the average value. Whether or not the actual strength matches the standard and design values is determined by the final figure. It is then recorded in the log after that.

Gallery: the process of employing a press to conduct destructive testing.

The video in this post provides more thorough instructions for testing concrete samples.

### Non-destructive testing

In every construction production, regardless of the stage of construction, the prior method is required.

It is thought to be the most trustworthy:

- Designers and architects rely on the results of protocols, laboratory destructive studies, when constructing buildings and manufacturing reinforced concrete products.
- When it is not possible to determine the strength of samples by destructive method, or a repeated analysis of the characteristics is required after a certain time, special devices are used.
- They are necessary in order to test the material for compression directly on site. With one light press, they determine the numerical value and, if desired, other necessary characteristics concerning the homogeneity and compaction of the body of the material.
- There is a lot of similar equipment, but the most common in construction circles is the IPS – MG device of various modifications. It is easy to use, accurate and the price for it is quite affordable.

It is primarily utilized on building sites. Using the impact pulse method, this electronic meter lets you quickly determine the density, strength, and elastic-plastic properties. GOST 22690 allows for this method even though it is not a priority.

Suggestions. It is essential to select or prepare the surface before "shooting" concrete. It needs to be flawless, with an area of at least 100 cm 2 and free of dents, voids, cracks, and other imperfections. You must sand the surface if required.

The test program will determine how many sections are acceptable, but three at the very least. A volumetric reinforced concrete structure typically requires the average value of fifteen samples.

Since the control points must be at least 50 mm from the edge and 15 mm from each other, the exact number depends on the area. The spaces between the large cavities in the concrete body and the crushed stone granules are ideal.

The structure needs to be tested by:

- turn on the device, and it will immediately be in test mode;
- enter data on the material being tested;
- cock the lever on the "gun";
- press firmly perpendicular to the surface being tested and release the lever;
- the result will appear on the display, it is remembered for subsequent tests;
- after 15 tests, the average value is automatically displayed, if the number of "shoots" is less, then you can preview the average result in advance.

One advantage of this kind of device is that all of its data can be archived and saved on a computer. You can create a protocol and view past tests on a computer at any time.

What is Design Compressive Strength? |
It’s the maximum amount of load a concrete mix can withstand before failing. It’s usually measured in pounds per square inch (psi) or megapascals (MPa). |

Why is it Important? |
Knowing this strength helps engineers ensure that structures can support the loads they’ll face over their lifespan without cracking or collapsing. |

How is it Determined? |
Design compressive strength is calculated based on the concrete mix’s ingredients, ratios, and intended use, often using tests from standard samples. |

What Affects Compressive Strength? |
Factors like water-cement ratio, type of aggregate, curing time, and environmental conditions during setting can influence strength. |

Applications |
Used in buildings, bridges, roads, and any structure where durability and load-bearing are critical. |

Conclusion |
Design compressive strength is crucial for safety and performance, guiding how concrete is used in construction projects. |

Anyone working in engineering or construction needs to understand concrete’s design compressive strength. This measurement aids in figuring out the maximum load that a concrete structure can support before failing. It is more than just a figure; it is essential to guaranteeing the longevity and safety of structures like bridges and buildings.

A thorough understanding of this indicator enables designers and builders to choose the right materials and mixes with confidence. It assists them in building structures that satisfy particular needs without going over budget. Stated differently, finding the ideal compressive strength requires striking the correct mix between economy and performance.

In the end, any construction project’s long-term success is greatly dependent on the concrete’s design compressive strength. By concentrating on this crucial element, we can construct long-lasting, safer structures. Gaining an appreciation for this idea will help you better understand why concrete is such a fundamental building material, regardless of whether you’re a professional in the field or just an interested homeowner.

## Video on the topic

### Strength of Materials Tension-compression diagram (lecture)

### Axial p.-szh. statically indeterminate problems Lesson #6 Topic #1 Strength of materials

### OSK lecture 2. Reinforced concrete structures

### Strength of materials. Lecture: calculation of tensile and compressive strength

### Height of the compressed zone of concrete of bending elements

### Calculated resistance of foundation soils. Assessment of settlement of columnar foundations

### SF. Deformative properties of concrete – open webinar

### Monolithic floor. Calculation of bending

**Which aspect of concrete application are you most interested in?**