Concrete Overstrength: Assessment of Field Strength Seeking Insights for Overdesign Optimization

Rodrigo Antunes

doi:10.3390/civileng3010004

Abstract

This study investigates the high contents of cementitious materials in Portland cement concrete and assesses the required (f’cr) and actual (σ) compressive strength of concrete specimens. A linear optimization technique identifies the required binder content to reach f’cr. Standard specifications have required concrete overdesign (OD) for decades, but few studies have evaluated the actual magnitude of OD from field data. The compressive strength of 958 cylinders prepared in the field represented 8200 m3 of ready-mixed concrete with 300 and 450 kg/m3 of cementitious are analyzed. The actual OD appears to be 7 to 21% higher than required. The required 28-day compressive strength of concrete was achieved in less than seven days. Therefore, the content of the cementitious materials could be reduced by 6 and 17% so that concrete could reach f’cr without cementitious overconsumption. Reducing cementitious content is recommended to improve construction quality and optimize resource utilization. Among the main reasons for this recommendation are the estimated substantial long-term savings, increased concrete durability and more rational use of natural resources required to build the structures.

Highlights

Silica sand will be used as fine aggregate (FA) and limestone grade 57 as coarse ag‐
Were and three at 28 days forfor every m delivered ered in most job sites, while some only cast specimens for days for contractual reasons
Dards can be abused, leading to environmental damage. This investigation was carried for ards can be abused, leading to environmental damage

Summary

Introduction

Concrete with lower cementitious content and more substitution of cementitious materials can decrease environmental impact while still reaching sufficient strength on time to avoid construction delays and last longer [1,2,3,4,5]. Overstrength caused by high cementitious content may induce concrete cracking. Pathologies can occur in a few pours, during the construction phase, or even many years after construction. When deficiencies in concrete are identified before the end of the construction phase, contractors often need to perform repairs. Such repairs usually are time-consuming, delaying construction completion and increasing costs

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Discussion

Conclusion