As the need for concrete with reduced environmental impacts becomes increasingly important, owners, designers, suppliers, and contractors face an array of innovative products that are coming to market that can contribute to more sustainable concrete. With new materials come concerns about how to incorporate them into specifications and designs, initial effects on concrete during mixing, placing, and finishing, long-term durability, and the environmental impacts of the new products themselves. This session will explore a range of new products including ground glass pozzolans, recycled plastic aggregates, recycled concrete aggregates, municipal solid waste aggregates, and low-carbon hydraulic cements.
Learning Objectives:
(1) Understand the benefits and challenges of using recycled materials in concrete;
(2) Understand how recycled materials affect both plastic and long-term properties of concrete;
(3) Understand how innovative binders including ground glass pozzolans and low-carbon hydraulic cements are produced;
(4) Understand the role of recycled materials and innovative binders in the concrete marketplace.
Flexural Testing of Rectangular Reinforced Concrete Beams with Extruded Plastic Coarse Aggregate Replacement
Presented By: Kimberly Kramer
Affiliation: Kansas State University
Description: Natural aggregates used in reinforced concrete are the most valuable non-fuel mineral resource, and growing concrete demand has surpassed their natural renewal rate. Recycled plastics present a potential alternative, reducing plastic waste while partially replacing natural aggregates. This study evaluates the structural behavior of reinforced concrete beams incorporating Plazrok, a recycled plastic coarse aggregate by Enviroplaz.
Three beam groups with 0%, 15%, and 30% coarse aggregate replacement (by volume) were tested in four-point bending. Each beam measured 150 × 250 mm (6 × 10 in.) with a clear span of 3.65 m (12 ft). Load-deflection responses were recorded using an actuator and LVDTs and compared to predictions from Branson’s (1965) and Bischoff’s (2005) effective moment of inertia equations. Experimental flexural strengths were also compared to nominal moment capacities based on common concrete stress-block assumptions.
While past studies on plastic aggregate concrete have focused mainly on material properties, this research contributes new insight into member-level flexural behavior with plastic coarse aggregate replacement, supporting its potential to reduce natural aggregate consumption and divert waste plastics from landfills and oceans.
Novel Lightweight Construction Aggregates Produced from Municipal Solid Waste
Presented By: Julie Buffenbarger
Affiliation: St Marys Cement
Description: One of the most significant challenges in waste management is the ever-increasing amount of municipal solid waste (MSW). Global waste production is soaring, driven by population growth, urbanization, and rising consumption. It is projected to increase to 3.8 billion metric tons by 2050. MSW has been conventionally used as an energy source through incineration; however, a circular economy approach not only promotes waste reuse and recycling but also offers a promising solution to reduce the massive extraction of raw materials, thereby inspiring the adoption of sustainable practices.
A newly patented technology represents a commercially viable solution to process organic and other MSW waste fractions through a novel hydrothermal treatment, while simultaneously overcoming barriers for acceptance as a lightweight aggregate. This methodology, which adopts circular economy principles in the construction industry, may slow the intensive exploitation of aggregates, which have become the most naturally extracted and consumed material in the world after water.
Ground Glass Pozzolans: From Recycled Glass to Concrete Binder
Presented By: Louis Grasso
Affiliation: Urban Mining Industries, LLC
Description: The United States produces approximately 20 million tons of glass annually of which approximately 11 million tons is used for containers, 5-6 million tons is plate glass, and 0.8 million tons is E-glass. While their chemistries differ, all three glass types can be cleaned, crushed, and ground for use as a pozzolan. By diverting post-consumer glass from landfills and using it as a pozzolan in concrete, we conserve landfill space and produce concrete that is less permeable, significantly lower in embodied carbon, and lighter in color than concrete made with ordinary portland cement. This session will explore the development of ground glass pozzolans, potential barriers to their adoption, and ways to overcome these barriers.
The Untapped Potential of Concrete Multi-Functionality in Decarbonizing the Built Environment
Presented By: Hessam AzariJafari
Affiliation: Massachusetts Institute of Technology
Description: While most decarbonization roadmaps for the built environment focus on reducing embodied emissions through carbon capture, material substitution, and recycling, they often overlook the transformative role of multi-functional concrete systems, where concrete performs beyond its structural functions. This presentation explores how integrating additional capabilities such as self-heating and energy storage into concrete can bridge the gap between embodied and operational carbon reductions. Two emerging examples of self-heating concrete pavements and electricity-storing concretes, in various contexts, will be discussed. The demonstrated cases and their role in lowering global warming impact illustrate how multi-functionality can extend concrete’s role from passive structure to active participant in energy and climate strategies. This is an opportunity largely absent from current sustainability frameworks and guidelines for the ACI community.
Using Recycled Concrete Aggregates Effectively in New Concrete Construction
Presented By: Greg McKinnon
Affiliation: Stoneway Concrete
Description: This session will provide a detailed overview of the current use and acceptance of Recycled Concrete Aggregate (RCA) in new concrete. Myths and misconceptions about RCA have created Roadblocks to its broader acceptance, often relegating recycled concrete to low-value functions like backfill and road base. There is a case to be made for challenging current specifications and regulations to drive broader acceptance of RCA in new concrete.