MINI SESSION: Impact of Aggregates' Usage and Gradation Towards Concrete Low Global Warming Potential

Tuesday, November 5, 2024  11:00 AM - 12:00 PM, 303

To highlight the impact of aggregates on the carbon footprint of concrete and to propose better ways to use aggregates towards low global warning potential and suitable long-term performance of concrete.

This session presents concrete durability related issues related to aggregates that could potentially harm the sustainability and long-term performance of critical infrastructure.

Learning Objectives:
(1) Understanding of the main durability related issues in concrete associated to aggregates;
(2) Knowledge of the current state of the art in methods to prevent those issues;
(3) Knowledge of new protocols proposed to diminish durability issues in concrete related to aggregates;
(4) Discussion on suitable pathways moving forward on the topic to decrease durability related issues associated to aggregates and increase sustainability of concrete construction.

Evaluating Damage Generation and Propagation of ASR Affected RCA Concrete

Presented By: Cassandra Trottier
Affiliation: University of Ottawa
Description: The use of recycled concrete aggregates (RCA) is gaining interest in the industry due to the pressure to adopt more sustainable practices; yet, concerns regarding the potential for further ASR damage in concrete made with RCA remain. In the current literature, the original extent of the ASR damage is often unknown when the concrete is crushed into RCA particles, therefore, inconsistencies regarding the potential for further ASR in concrete made with affected RCA are observed in the literature. RCA is a multi-phase material consisting of the original virgin aggregate (OVA) and residual mortar (RM), which is further divided into residual sand and cement paste. ASR may, therefore, originate from the reactive OVA or residual sand, and its extension into the cement paste depends on the extent of reaction/damage. This work evaluated the secondary damage generation and propagation in concrete made with RCA presenting two levels of initial damage (i.e., 0.05% and 0.30% of expansion, representing a concrete returned to the plant and demolished concrete, respectively) induced by either reactive coarse OVA or residual sand. A microscopic tool (i.e., Damage Rating Index - DRI) was used for the analysis, while distress features (i.e., cracks) were measured in counts per 100 cm2, length, width, and types of propagation to characterize the distinct damage patterns induced by various types of RCA affected by ASR.

Current State of the Discussion on Pyrrhotite in Concrete

Presented By: Jamison Langdon
Affiliation: Braun Intertec Corporation
Description: Recent legislative efforts to mitigate pyrrhotite in concrete are beginning to take shape in the form of limits on sulfide in the aggregates being used. A quick overview of some of those efforts will be presented as well as provide a bit of technical guidance on how and where pyrrhotite naturally occurs.

Influence of Coarse Aggregates Mineralogy on Long–Term Durability Properties of Optimized Concrete Mixes

Presented By: Shuyah Tani Ouoba
Affiliation: University of Arkansas
Description: As aggregates constitute more than 60% of concrete volume, their impact on concrete durability is significant. However, the aggregate component of concrete is generally thought of as inert filler. This study examines the influence of coarse aggregate mineralogy on long-term concrete properties such as drying shrinkage and bulk resistivity. Concrete mixtures were prepared according to the Arkansas Department of Transportation specifications using Type 1L cement; the cement content was progressively reduced, and fly ash was used. Aggregate gradation methods were employed to optimize mix proportions with reduced cement contents. Additionally, a new test procedure for assessing the potential for Alkali-Silica Reaction of Aggregates is compared to traditional test methods for the different species of aggregates considered.

TFHRC ASR Toolkit: Path Towards Validation with Field Concrete Mixes

Presented By: Chandni Balachandran
Affiliation:
Description: The effective management of alkali-silica reaction (ASR) calls for striking the balance between mitigating ASR risk and optimizing the usage of supplementary cementitious materials. The recently launched Transportation Pooled Fund Study, TPF 5(521), aims to validate a job mix-driven ASR management approach using the newly developed TFHRC ASR toolkit. The rationale behind this approach is that the ASR mitigation strategy chosen is dependent on the ASR risk associated with a particular mix design. This risk can be gauged based on the relationship between its alkali loading and the alkali threshold of the aggregate combination used in it. An overview of the scope of TPF 5(521) and the broad implications of job mix-driven ASR management will be discussed.