Sessions & Events


Please note: All sessions and events take place in Central Daylight Time: CDT (UTC-5).

H=Hyatt Regency Dallas; U=Union Station

Concrete with Recycled Materials, Part 2 of 2

Sunday, October 23, 2022  1:00 PM - 3:00 PM, H-Reunion C

Concrete is the world's most widely used construction material. Yet, the production of portland cement, an essential constituent of concrete, leads to greenhouse gas emissions into the atmosphere. The production of one ton of portland cement clinker releases approximately one ton of CO2 and other greenhouse gases. Environmental considerations have been a major thrust for the sustainable development of the cement and concrete industries. A sustainable concrete structure is designed and built to have a positive environmental footprint during its entire life cycle. Concrete is increasingly being considered as a sustainable material owing to its low inherent energy requirements and little associated waste. Not only is it made from some of the most plentiful resources on Earth, it can also be made with numerous recycled materials and by-products and is itself entirely recyclable. Emerging breakthroughs in concrete technology have allowed producing ultra-high-performance concrete requiring less raw materials, along with structures that are much more durable to reduce maintenance, repair, and reconstruction.
Learning Objectives:
(1) Demonstrate how to evaluate recycled concrete mixtures with various waste-by-product and recycled materials;
(2) Recognize many different types of testing that could be performed on new concrete mixtures produced with recycled materials;
(3) Explain various methods to design and validate the concrete produced by new recycled materials;
(4) Analyze emerging technologies in the concrete produced by recycled materials and its application in civil infrastructures.

This session has been AIA/ICC approved for 2 CEU/PDH credits.

Recycled Concrete Aggregate Composition Determined Using a Handheld XRF Device

Presented By: Tara Cavalline
Affiliation: University of North Carolina At Charlotte
Description: Use of recycled concrete aggregates (RCA) in lieu of natural aggregates improves the sustainability of the built environment. Primary barriers to increased use of RCA include its variable composition, including the residual mortar content (RMC), chemical composition, and its potential to contain contaminants which can negatively affect the properties of concrete or present environmental concerns. A rapid, economical method for estimating the RMC and providing chemical characterization of RCA would provide confidence to users in its suitability for use in new concrete or in unbound base or fill materials. In this study, a method was developed using a portable handheld x-ray fluorescence (PHXRF) device, which can be used to estimate the RMC and chemical composition of RCA. Models were developed based on reference tests (RMC test based on thermal shock method and chemical composition from Whole-rock analysis) to correlate PHXRF results to measured values. The PHXRF shows strong potential for estimating the RMC and chemical composition of RCA. Paired with locally calibrated reference samples, the proposed test method could be used in laboratory or field applications to better characterize RCA and increase its use in bound and unbound applications. Fostering the use of this technology could promote the use of RCA in concrete construction.

Mechanical Properties of Concrete Made with Chemically Treated Returned Concrete Aggregates

Presented By: Paul Horst Seiler
Affiliation: Master Builders Solutions
Description: According to the NRMCA returned concrete represents 2% - 10% of production and producers indicate that this number is growing. This represents an operational, financial, and environmental problem for concrete producers—and one that is not easily solved. Currently producers address this problem by fabricating concrete blocks, crushing hardened concrete, or land filling returned concrete. Being able to take returned concrete still on its plastic state, and transform it into a revenue stream without adversely affecting the environment by quickly transforming it into a usable raw material that can be sold independently and/or incorporated into future concrete production is a preferable solution The process to treat returned concrete is very simple. The steps are: 1) estimate the volume of the returned concrete, 2) add the returned concrete admixture treatment, 3) mix for about two minutes, 4) discharge the granulated material on the ground in piles that are about 12 inches (300 mm) in height, 5) flatten the piles sometime during the day of discharge, and 6) turn the flattened piles the next day and move the recycled concrete aggregates (RCA)h to the desired storage location to be sold and/or used in concrete production. This paper will discuss the process of fabricating the aggregates, optimal mix design proportioning to obtain good mechanical and durability properties as well as a brief economic analysis utilizing tools being developed by the NRMCA – National Ready Mix Concrete Association. (1) John Luciano is a Senior Scientist at Master Builders Solutions with over 40 years of experience in concrete and admixtures. (2) Steve Schaef is a Group Manager for the Engineering group at Master Builders Solutions with over 15 years of experience in concrete and admixtures (3) Paul H Seiler is the Technology Director at Master Builders Solutions with over 20 years of experience in concrete and admixtures.

Mitigation and Assessment of Alkali-Silica Reaction (ASR) in Eco-Efficient Concrete Incorporating Reactive Fine Recycled Concrete Aggregate (FRCA) Particles

Presented By: Carolina Londero
Affiliation: University of Ottawa
Description: In the current need of developing more sustainable construction, recycled concrete aggregates (RCA) emerge as an alternative to decrease the carbon footprint and the waste disposal of demolished concrete. Coarse and fine recycled aggregates can be produced from crushing processes of concrete demolition waste; however, concrete made with RCA has demonstrated unsatisfactory fresh and hardened properties including a decrease in the durability performance, mainly when incorporating the fine fraction (FRCA). Besides, the origin of the material consists of an important aspect since the concrete could have been subjected to past adversities such as alkali-silica reaction (ASR). ASR is one of the most harmful deterioration mechanisms affecting concrete, causing expressive damage and its demolition. There is a lack of understanding of mitigation ways of ASR in RCA concretes, especially in combination of supplementary cementitious materials (SCM) and when FRCA is incorporated, whose characterization and behavior represent a challenge for its use due to its physical characteristics and composition uncertain. Therefore, the research aims to investigate the use of SCM in the prevention of ASR-affected RCA, as well as to analyze the potential of further induced expansion and damage in concretes incorporating FRCA.

NanoCarbon Black in UHPC – Effect on Conductivity and Mechanical Properties

Presented By: Ahmed Omran
Affiliation: New Jersey Institute of Technology
Description: The emergence of multifunctional cement-based materials in the construction industry has the potential to shift the paradigm from strength-only performance to new functionalities enabled by electron conducting capabilities in one of the most material- and energy-intensive industry sectors worldwide. To enable such developments, we present results of an experimental investigation of the electrical conductivity and resistive (Joule) heating of UHPC–nanocarbon (nCB) composites. We found that the nCB inside the cement matrix creates a volumetric wiring enabling an electrical conductivity permeating a highly heterogeneous cement matrix starting at a given percolation dosage of the nCB. The study revealed that increasing the nCB dosage to achieve higher conductivity compromises the mechanical performance of the cement matrix and this should be optimized. An explanation for the mechanical performance loss was examined using XRD and the through determination of friction between matrix layers. Harvesting the benefits of electron conducting cement-based materials, such as resistive heating, electromagnetic shielding, and energy storage, will ultimately be beneficial for the achieving the sustainability in concrete industry. Given the global environmental footprint of concrete, the results open venues for the sustainable development of concrete for existing and emerging green technology applications.

An Experimental Study on Concrete Incorporating Wood Ash as Cement and Fine Aggregate Replacement

Presented By: Shahria Alam
Affiliation: University of British Columbia
Description: Concrete, the most used material on earth after water, contributes a great deal to the environment and the atmosphere. Concrete’s main ingredients are cement, sand and coarse aggregates. Cement alone is responsible for emitting a considerable amount of CO2, a total of 8% of the sum of the global greenhouse gas emissions. Sand and coarse aggregate are also using up the topsoil and need to be conserved being mother earth’s valuable resources. Replacing any of the ingredients with recycled waste material reduces the carbon footprint of a virgin concrete mix. Coal fly ash is such a material that is used in concrete as a supplementary cementitious material (SCM) for making concrete greener and more economic. However, coal industries being shut down for its pollution effect poses a new challenge in finding this most popular SCM in near future. Fly ash obtained from wood and lumber industries has a great potential for being a substitute for coal fly ash. The main challenge in using wood fly ash lies in the inconsistency of its properties for seasonal and source variations. Along with wood fly ash, wood bottom ash is a good option for being used as a replacement for sand. In this study, an experimental program was carried out to observe the fresh and mechanical properties of mortar and concrete using different percentages of wood fly ash and bottom ash as cement and sand replacement respectively. It was concluded that incorporating wood bottom ash did not have a significant effect on the properties of concrete, but a 30% replacement of cement with wood fly ash provided concrete with comparable compressive and tensile strength.

Development of an Eco-Friendly Glass Fiber Reinforced Concrete Using Recycled Glass as Sand Replacement

Presented By: Shahria Alam
Affiliation: University of British Columbia
Description: Concrete is the most widely used construction material on earth (30 billion tonnes used in 2021). Aggregates occupy most of its volume, nearly 60-90% of total concrete. However, aggregate production and transportation contribute to significant disturbance to the ecological system and depletion of natural resources. Hence, substituting the aggregates with waste and recycled components not only conserves natural resources but also lowers the carbon footprint of virgin concrete. Thus, this study investigates the applicability of using poraver, an aggregate made of 100% post-consumer recycled glass, for preparing lightweight glass fiber reinforced concrete (LWGFRC). In this experiemntal program, three types of concrete mixes were produced using 0%, 50%, and 100% poraver as sand replacement. The physical properties, such as density, water absorption, and porosity, the mechanical properties for example compressive strength, flexural strength, and splitting tensile strength, and the cyclic freeze thaw durability property were determined. Results of this study indicated that it is possible to produce GFRC with 30% less weight using poraver without compromising the mechanical and durability properties. Since GFRC is primarily used for architectural cladding panels, reducing its weight is further beneficial. This study provides a promising view to develop an eco-friendly and cost-effective LWGFRC using recycled glass as a sand replacement.

Upper Level Sponsors

Ash Grove
Controls Group
Euclid Chemical
Master Builders
ACI Northeast Texas Chapter

Please enter this 5 digit unlock code on the web page.