Existing testing and qualification methods for alternative cementitious materials (ACMs) are based on approaches originally developed for portland cement-based binder systems. However, due to distinct hydration and maturation rates, microstructures, and chemical compositions of many ACMs, historic testing methods may not accurately reflect their performance. This session will explore ongoing work to understand and tailor quality control, strength, and durability test methods to reflect the real world performance of alternative cements. By developing these methods, researchers and industry professionals aim to ensure that ACMs meet structural and durability requirements, allowing designers to confidently specify the use of these unique materials.
Learning Objectives:
(1) Describe how varying hydration chemistries and reaction rates impact the timing of test methods;
(2) Evaluate the impact of ACM chemistry and microstructure on use of traditional test methods;
(3) Identify best practices for assessing durability of ACM concrete materials;
(4) Discuss recommended adjustments to testing methods to more accurately reflect the real-world performance of ACMs.
Overcoming Challenges in Creep and Shrinkage Testing of Rapid Setting and Expansive CSA Cements
Presented By: Royce Floyd
Affiliation: The University of Oklahoma
Description: Calcium sulfoaluminate (CSA) cement is an alternative hydraulic cementitious material that can be formulated for rapid strength development or expansion to offset concrete shrinkage. CSA cement systems require more water for hydration than traditional portland cement, so careful curing is required to achieved optimum performance. This presentation presents results of an experimental program evaluating creep and shrinkage behavior of rapid setting belitic CSA and expansive CSA cement concretes intended for prestressed and self-stressing applications. Specific attention is given to the modifications in testing methods required to accurately capture early age behavior and the impact of curing on overall behavior under sustained compression loading.
The Development and Commercialization of Calcium Carbonate Cement
Presented By: Craig Hargis
Affiliation: Fortera
Description: Over the past three decades, calcium carbonate cement has been in development and is now being commercialized. This study presents the novel cement’s development timeline, strength development mechanism, mechanical performance, and durability. During development, many standardized tests were utilized. Often, the test protocols were effective as written; however, at times, beneficial modifications to the testing protocol were adopted to better reflect the cement’s unique properties or how the cement would be utilized in the field. Accordingly, ongoing efforts to update ASTM standards to accommodate alternative cementitious materials are outlined.
Field Testing and Continuous Monitoring of Rapid Set Concrete in the Field
Presented By: Julio Paniagua
Affiliation: CTS Cement Manufacturing
Description: Rapid Set CSA cement is an alternative cement that is well known for its ability to gain strength very rapidly. It has been widely used during the last couple of decades to develop high-performance concrete mixes designed to endure and perform in all types of weather environments and traffic closure requirements. Bridge, highways and airfields are part of critical infrastructure that cannot be closed for long periods and require high-performance mixes.
Field testing and concrete fresh properties remain being tested and evaluated based on specifications created decades ago for conventional portland cement concrete. Properties such as slump are not significantly important for fast-setting concrete mixes, as they might change in a matter of minutes. The need to cure and test strength at an early age also adds complexity to the technicians in charge of field preparation and testing of concrete samples.
The rapid changes in the properties of high-performance mixes require procedures to capture their evolution from time zero. This principle also applies to other performance-based mixes, such as shrinkage-compensating concretes. This presentation outlines best practices for testing fast-setting concrete in the field and discusses alternative testing procedures to capture performance properties, such as shrinkage and strength, from time zero.
Calcium Sulfoaluminate (CSA) Cement Curing for Optimal Hydration and Property Development
Presented By: Lisa Burris
Affiliation: Ohio State University
Description: Wet curing improves portland cement (PC) concrete durability and strength by increasing total hydration, densifying microstructure and decreasing concrete permeability. In general, wet curing is recommended for PC concrete curing until it gains >70% of the designed compressive strength, typically at least 7 days. Calcium sulfoaluminate (CSA) cement may allow for decreased curing time requirements due to its rapid hydration, hardening, and strength gain. This study investigated a variety of curing durations and curing solution compositions to understand their effects on CSA hydration, strength development, and shrinkage. The results demonstrate that curing for 2 days promotes adequate strength gain and completion of hydration reactions. However, utilization of limewater, as is allowed for curing of PC concrete samples taken for determination of concrete strengths resulted in significant reductions in the strength of CSA samples relative to those cured in 100% RH conditions. These results suggest that requirements for curing must be tailored to the specific binder systems utilized, and PC concrete requirements are often not relevant, and sometimes detrimental, to the quality of CSA-based concrete systems.
Freeze-Thaw Resistance of Alkali-Activated Materials
Presented By: Mehdi Khanzadeh Moradllo
Affiliation: Temple University
Description: Non-clinkered materials, such as alkali-activated (AA) systems, are potential alternatives to OPC to reduce CO2 emissions. AA systems can be formulated to display lower intrinsic permeability and discontinuous pore structures than OPC, permitting microstructural tuning to limit saturation. However, there are a limited number of studies concerning the freeze-thaw resistance of AA systems in cold environments. This study directly compares OPC and AA mixtures to determine the differences in freeze-thaw durability. This study implements thermomechanical analysis (TMA) to quantify the frost-induced damage in AA and OPC systems with micro-scale resolution. Additionally, water absorption, bulk electrical resistivity, and porosity measurements, along with microstructure characterization, were performed to relate the freeze-thaw performance to the microstructural and mass transport properties of AA systems.
CSA Cements - Strength and Durability Testing Considerations
Presented By: Cameron Murray
Affiliation: University of Arkansas
Description: This talk will detail some major differences between CSA cements and traditional portland cement-based materials and how these differences impact strength and durability testing. Results from strength tests such as compressive strength, modulus of elasticity, modulus of rupture, and splitting tension will be compared to portland cement results and code equations to discuss the major differences in performance especially related to age. Durability and dimensional stability testing will also be discussed including measuring restrained and unrestrained volume change and corrosion resistance of CSA cements. In particular, the early age performance and microstructure development of CSA cements poses challenges with applying traditional portland cement testing approaches. Some basic alterations or principles will be proposed to adjust the existing testing protocols to determine the properties of interest. Specifiers should be aware that the unique microstructure of CSA cement should be considered carefully when requiring tests for strength and durability properties.
Things to Consider When Fly Ash-Based Geopolymer Concrete is Being Utilized in Concrete Applications
Presented By: Lateef Assi
Affiliation: Terracon
Description: Development of sustainable construction materials has been the focus of research efforts worldwide in recent years. Concrete is a major construction material; hence, finding alternatives to ordinary Portland cement is of extreme importance due to high levels of carbon dioxide emissions associated with its manufacturing process. Several studies have shown that geopolymer concrete can not only replace conventional concrete partially but also has some mechanical and durability properties that exceed those of conventional concrete. However, several factors should be considered, including the selection of suitable materials and sources, the process of mixing, testing, and their applications. The presentation will show the best practices for raw materials selection, and explore the challenges in the mixing of geopolymer concrete and the safety concerns associated with it. Testing procedures adjustments will be presented, and the suitable applications for it.