Title:
Factors Affecting Concrete Performance and Challenges in Accounting for that
Author(s):
Obla
Publication:
Web Session
Volume:
ws_S23_Obla.pdf
Issue:
Appears on pages(s):
Keywords:
DOI:
Date:
4/2/2023
Abstract:
An average concrete plant (50,000 yd3/year production) uses 10 shipments of cement and 2 shipments of fly ash (25 tons) every week. Ingredient materials even if procured from the same source tend to vary leading to variable concrete performance. Past studies have shown that cement procured from a given source can cause a 1000 psi swing in 28-day concrete strength – all other parameters being the same! Add in the variation from the other supplementary cementitious materials, SCM, (i.e., fly ash, slag cement, etc.), and the 28-day concrete strength variation due to cementitious material variation can be even higher. The 28-day strength variation in projects for concrete of good quality (standard deviation < 500 psi) has been documented to be about 3000 psi. This includes variation due to material, manufacturing, and testing. Concrete strength variation has typically been addressed by adding a safety factor in terms of over-design to the 28-day specified strength. This presentation will discuss challenges in using models to predict performance and help reduce over-design.