Title:
Early-age Concrete Strength Prediction by Maturity--Another Look
Author(s):
Francis A. Oluokun, Edwin G. Burdette, and J. Harold Deatheridge
Publication:
Materials Journal
Volume:
87
Issue:
6
Appears on pages(s):
565-572
Keywords:
age-strength relation; compressive strength; concretes; curing; heat of hydration; temperature; tests; Materials Research
DOI:
10.14359/2519
Date:
11/1/1990
Abstract:
Discusses the results of an investigation of the relationship between compressive strength development and maturity, particularly at early ages. Tests were carried out on three different concrete mixes with 28-day compressive strengths ranging approximately from 4000 to 9000 psi. Type I portland cement was used, and test specimens were the conventional standard moist-cured 6 x 12 in. concrete cylinders. Tests were performed at 6 and 12 hr and 1, 2, 3, 7, and 28 days. Plowman's equation, to which other compressive-strength prediction relations are related (at least in form), was found to be inaccurate at early ages, especially during the first 2 days after casting when maturity is low. Analyses of test results show that maturity can be used to predict compressive strength of concrete at early ages if the heat of hydration is duly incorporated into the evaluation of maturity at early ages. An alternate improved relation that incorporates the heat generated during hydration was formulated and proposed. Additionally, the relationship between the 7- and 28-day compressive strengths was investigated. Existing equations that relate 7-day to 28-day strength were evaluated and found to be inaccurate by as much as 13 percent. An alternate and more accurate relation than the existing relations was formulated and proposed.