For 7 days, no code specifies what should be the strength. Concrete continues to hydrate and to gain strength for years after it is poured. Introduction Predicting 28 Days Compressive Strength of Concrete from 7 Days Test Result 1. International Conference on Advances in Design and Construction of Structure - 2012 19-20 October 2012, Bangalore, India Predicting 28 Days Compressive Strength of Concrete from 7 Days Test Result Dr. Ahsanul Kabir Professor, Dept. cube size is 150x150x150, because it has been set as standard size, the value of compressive strength of which has been standardized at 28 days.We can also use 200mm cube, but you have to convert the compressive strength of 200mm cube to the equivalent of 150mm cube … IS:456–2000 clause 15 to 17. Computing the Compressive Strength of Concrete Cubes at (7 or 28 days) by Using a Multi Forms Program Nariman Yahya Othman Engineering College, Babylon University.

Because concrete compressive strength is at 99% in 28 days, it is very close to its final strength which could be in 1 or 2 years time. Concrete has versatile use in the construction practice. Concrete compressive strength does not depend on the full hydration of its cement particles but essentially on their closeness. There should a strength development with time at a reduced rate, and in general the strength at 7 days is about 65-75% of that at 28 days. Compressive Strength of Concrete at 7 days and 28 days. According to Wikipedia, Compressive Strength of concrete is defined as the Characteristic strength of 150mm size concrete cubes tested at 28 days. It is mandatory to test the concrete cylinders at the age of 28 days as per almost all building code requirements. f ck = Characteristic compressive strength in 28 days S = Standard Deviation 1.65 Not more 5% of the results falls below characteristic value 2.33 Not more 1% of the results falls below characteristic value . Why do we test at 7, 14 & 28 days? Labcrete vs Sitecrete Courtesy: Prof.Basheer, QUB, UK Compressive Strength of Concrete 16 18.5 Structure. What is compressive strength after 7 days and 14 days? 2.4 Hardened concrete 2.4.1 Compressive strength Compressive strength tests were conducted on cured cube specimen at 7, 28 and 56 days age using a compression testing machine of 200 tons capacity. Concrete gains strength due to the chemistry of the hydration of the cement. A: No, if they both are from the same mixture, 7 days concrete strength can’t be more than 28 days strength. CiteSeerX - Document Details (Isaac Councill, Lee Giles, Pradeep Teregowda): Abstract—Concrete structures are designed on the basis of 28 days cylinder crushing strength. f ck = Characteristic compressive strength in 28 days S = Standard Deviation 1.65 Not more 5% of the results falls below characteristic value 2.33 Not more 1% of the results falls below characteristic value . Average 28 days compressive strength of at least three 150 mm concrete cubes prepared with water proposed to be used shall not be less than 90% of average of strength of three similar concrete cubes prepared with distilled water. Fisrtly we need to know why the concrete get strong.

The cube can be tested after 3,7,14 and 28 days. Compressive Strength (N/mm 2) Avg.

Strength requirement and acceptance criteria is specified in IS 456 For 28 Days strength. Mainly it’s because of the concrete hydration reaction. 46 4.6 Failure of cylinder specimen during 7 and 28 days. PDF | On Jan 1, 2012, A. Kabir and others published Predicting 28 days compressive strength of concrete from 7 days test result | Find, read and cite all the research you need on ResearchGate

Concrete is a macro content with Sand, Cement, & Coarse aggregate as its micro-ingredient (Mix Ratio) and gains its 100% strength over time at the hardened state. This paper presents a simple mathematical model to predict the compressive strength of concrete at 28 day from early age (say 7 days) results. The design strength of the concrete normally represents its 28th day strength.

90% in only 14 days. Thus, it is clear that concrete gains its strength rapidly in the initial days after casting, i.e. PDF | On Jan 1, 2012, A. Kabir and others published Predicting 28 days compressive strength of concrete from 7 days test result | Find, read and cite all the research you need on ResearchGate