Maturity-Based Field Strength Predictions of Sustainable Concrete Using High-Volume Fly Ash as Supplementary Cementitious Material Sushant Upadhyaya, Ph.D., M.ASCE 1 ; Dimitrios Goulias, Ph.D. 2 ; and Karthik Obla, Ph.D., P.E. 3 Abstract: The use of fly ash in concrete has received significant attention during recent years, owing to environmental concerns regarding its disposal and to its potential use as a supplementary cementitious material owing to its ability to improve concrete performance. Although a fly ash content of less than 25% of the total cementitious content is routinely used in concrete, high-volume fly ash (HVFA) concrete is not commonly used because of perceived lower early age strengths. The objective of this research was to use maturity based modeling to demonstrate that the beneficial effects of high temperatures observed in structural elements such as slabs and concrete beams during the hydration process associated with the mass features of such elements may compensate for the slower rate of strength gain of fly ash concrete that is typically observed in standard laboratory cured cylinders. Match cured cylinders were used during this process to estimate the early age in-place strength of HVFA concrete and to confirm the predicted mature strengths. The results have shown that standard and field cured cylinder strengths underestimate the in-place concrete strength. High in-place temperatures owing to the mass characteristics of structural elements result in increased and satisfactory in-place early age strengths for construction, measured by match cured cylinders and pullout testing, and predicted by maturity modeling. DOI: 10.1061/(ASCE)MT.1943-5533.0001123. © 2014 American Society of Civil Engineers. Introduction After water, concrete is the most frequently used material in the world, with an estimated yearly production of 27 billion t world- wide. In the complex interaction between humanity and the envi- ronment, sustainability (i.e., the interaction between social and economic activities) and the use of sustainable materials have be- come increasingly important for enhancing resilience, defined by the Concrete Joint Sustainability Initiative (CJSI 2009) as “the community’ s capacity to provide viable continued use in the built environment through extended service life, and adaptive re-use. ” Concrete has a significant role in the sustainable environment. Historically, cement production has contributed approximately 5% of total CO 2 emissions and 3% of greenhouse gases (Jeffries 2009). The concrete industry has adopted significant steps toward reduc- ing emissions and greenhouse gases. Furthermore, concrete is con- sidered to be a sustainable building material because byproducts such as fly ash, slag cements, and silica fume are regularly used; a durable and long lasting material; has the ability to absorb and retain heat, reducing energy demand for buildings; better reflects solar radiation owing to its light color reflectivity; and has the abil- ity to filter contaminants to groundwater when used in pervious applications; additionally, and with current concrete recyclability trends, there is minimal landfilling (Balogh 2013). In 2012, 52 million t of fly ash were produced from the burning of coal in power plants [American Coal Ash Association (ACAA) 2012]. According to the ACAA, 45% of fly ash is currently ben- eficially utilized in various applications, with the remaining portion disposed typically in landfills. Approximately 61% of the benefi- cial fly ash was used in cement and concrete applications. Because ready mixed concrete represents the single largest market for fly ash, it can offer the largest potential for increased utilization of fly ash. According to the National Ready Mix Concrete Associa- tion (NRMCA), the estimated production of ready mixed concrete in the U.S. in 2012 was 220 million m 3 (290 million yd 3 ). Accord- ing to the NRMCA (Obla et al. 2012b), the average fly ash use in ready mixed concrete is 49 kg=m 3 (83 lb=yd 3 ). The survey re- ported that an extra 14 M tons of fly ash can be used every year in ready mixed concrete, which represents an increase in fly ash utilization of 71%, assuming the same production level as in 2012. The objective of this research was to use maturity based mod- eling to demonstrate that the beneficial effects of high in-place hy- dration effects observed in structural elements may compensate for the slower rate in the strength gain of fly ash concrete that is typ- ically observed in standard laboratory cured cylinders. The in-place strength of concrete in structures can be determined by monitoring the temperature–time history and estimating the in-place strength from precalibrated strength/maturity models. Maturity predictions are well established for conventional portland cement concrete, but not for high-volume fly ash (HVFA) concrete mixtures containing chemical admixtures. The Arrhenius and Nurse-Saul maturity func- tions are commonly used to establish the maturity index. The Ar- rhenius maturity function, which is considered to be more accurate (Carino 2004), was used in this research. This function requires the use of mixture-specific activation energy values for predictions of strength. The activation energy quantifies the temperature sensitiv- ity of the concrete mixture. 1 Senior Engineer, GeoConcepts Engineering, Inc., 19955 Highland Vista Dr., Suite 170, Ashburn, VA 20147. E-mail: SUpadhyaya@ GeoConcepts-Eng.Com 2 Associate Professor, Dept. of Civil and Environmental Engineering, Univ. of Maryland, College Park, MD 20742 (corresponding author). E-mail: dgoulias@umd.edu 3 Vice President, Technical Services, National Ready Mixed Concrete Association, Silver Spring, MD 20910. E-mail: KObla@nrmca.org Note. This manuscript was submitted on December 20, 2013; approved on May 7, 2014; published online on August 5, 2014. Discussion period open until January 5, 2015; separate discussions must be submitted for in- dividual papers. This paper is part of the Journal of Materials in Civil Engineering, © ASCE, ISSN 0899-1561/04014165(7)/$25.00. © ASCE 04014165-1 J. Mater. Civ. Eng. J. Mater. Civ. Eng., 2015, 27(5): 04014165 Downloaded from ascelibrary.org by University of Maryland on 03/05/23. Copyright ASCE. For personal use only; all rights reserved.