E-quiz On Concrete Technology

The specified full strength of concrete for IS 456:2000 is achieved at 28 days. This means that the concrete reaches its maximum strength after 28 days of curing. Curing is the process of maintaining the moisture and temperature conditions for the concrete to develop its full strength. While concrete gains strength rapidly in the initial days, it continues to gain strength slowly over time. Therefore, the 28th day is considered the standard time frame for determining the full strength of concrete according to IS 456:2000.

The slump cone test is used to determine the workability of a concrete mix. Workability refers to the ease with which the concrete can be mixed, placed, and compacted. The test involves filling a slump cone with fresh concrete, then removing the cone and measuring the slump or settlement of the concrete. This measurement gives an indication of the consistency and flowability of the concrete mix, which is important for ensuring proper placement and compaction during construction.

At 28 days of curing, concrete typically attains a strength of 90 to 95%. Curing is the process of maintaining adequate moisture and temperature conditions for the concrete to properly hydrate and gain strength. During this period, the chemical reactions between cement and water continue, resulting in the development of the desired strength. Generally, concrete reaches its maximum strength after 28 days of curing, and the range of 90 to 95% indicates that it has achieved a significant portion of its ultimate strength by this time.

The specified full strength of concrete for IS 456:2000 is achieved after 28 days. This means that the concrete reaches its maximum strength and durability after 28 days of curing and hardening. The strength of concrete gradually increases over time, and it is typically tested at different intervals such as 7 days, 14 days, 21 days, and 28 days to monitor its progress. However, the full strength is only achieved after 28 days of curing.

The standard size of a concrete cube for compressive strength test is 150 mm. This size is commonly used because it allows for a sufficient amount of concrete to be tested while still being manageable and easy to handle. Additionally, the 150 mm size provides a good balance between accuracy and practicality for conducting compressive strength tests on concrete samples.

Segregation in concrete refers to the separation of coarser particles of the mix, which leads to a lack of uniformity or non-homogeneity in the concrete. This can occur during the mixing, transportation, or placing of the concrete, causing the larger particles to settle or separate from the rest of the mix. This can result in areas of the concrete with a higher concentration of coarse particles, leading to a weaker and less durable structure.

The Vicat apparatus is used to determine the setting time of cement. It measures the consistency and stiffness of the cement paste as it hardens. The test involves placing a plunger on the cement sample and measuring the depth of penetration at different time intervals. The setting time is the time taken for the cement to harden and lose its plasticity. This test is important in construction to ensure that the cement sets within a specified time frame, allowing for proper curing and strength development.

The given answer, M400, is the correct answer because M400 refers to the concrete grade, which indicates the strength of the concrete. Ordinary concrete, which is typically used for general construction purposes, does not have the required strength to meet the specifications of M400 grade concrete. M400 grade concrete is typically used for specialized construction projects that require high strength and durability, such as in the construction of bridges or high-rise buildings.

The correct answer is 1 : 2 : 4 mix. This is because the M 15 grade of concrete requires a specific ratio of cement, sand, and aggregate. In this case, the ratio is 1 part cement, 2 parts sand, and 4 parts aggregate. This mix is commonly used for general construction purposes and provides a good balance of strength and workability.

According to Indian standard specifications, concrete is designated into 7 grades. This means that there are different classifications or categories for concrete based on its strength and quality. These grades help in ensuring that the concrete used in construction projects meets the required standards and can withstand the intended loads and stresses. The use of different grades allows for flexibility in choosing the appropriate concrete strength for different applications and structural requirements.

Di-calcium silicate (C2S) generates less heat of hydration. Heat of hydration is the heat released during the chemical reaction between water and cementitious materials in concrete. C2S is a component of cement and its hydration process releases less heat compared to other components like tricalcium silicate (C3S). This is beneficial in preventing excessive temperature rise during concrete curing, which can lead to thermal cracking and reduced durability of the structure.