This session will provide state-of-the-art discussion on the use of alternatives to portland cement, with a focus on processes for upscaling the use of alternative cements (ACMs) and understanding beneficial applications in which ACMs can be used in lieu of portland cement to create more durable, sustainable, and resilient concrete. The session targets both researchers working to advance understanding of ACMs and industry users (suppliers, producers, and owners) interested in applying ACM technology to their work.
(1) List several types of alternative cements and possible uses for these materials in construction infrastructure;
(2) Describe how construction with alternative cements, including effects from differences in setting, curing, and property development, differ from the standard OPC construction processes;
(3) Explain what challenges exist with regards to specifying use of alternative cements, and ensuring quality control of materials in the field;
(4) Evaluate if using an alternative cement would benefit a particular project or application.
This session has been approved by AIA and ICC for 2 PDHs (0.2 CEUs). Please note: You must attend the live session for the entire duration to receive credit. On-demand sessions do not qualify for PDH/CEU credit.
Reinforced Concrete Made with Belitic Calcium Sulfoaluminate Cement
Presented By: Cameron Murray
Affiliation: University of Arkansas
Description: Belitic calcium sulfoaluminate cement (BCSA) is a hydraulic, rapid-setting alternative to ordinary portland cement (OPC) with reduced energy demands and CO2 emissions. Currently, limited research exists regarding the structural performance and practical application of BCSA cement concrete, restricting its potential implementation. This talk will cover a study on the flexural performance and behavior of reinforced BCSA concrete beams. Overall, BCSA concrete had similar cracking and loading behavior to the OPC beams. Furthermore, BCSA cement concrete showed increased ductility when compared to OPC. Overall, the flexural strength of the BCSA cement concrete was higher than the control OPC concrete and the predicted flexural strength based on compressive strength, indicating the current flexural strength equations are applicable for BCSA reinforced concrete design. Additionally, the talk will include some lessons learned about designing concrete mixtures using BCSA cement including some data on the relationship between w/c and compressive strength and the relationship between retarder dosage and setting time.
Methods for Determining Converted Strength of Calcium Aluminate Cement Systems
Presented By: Matthew Adams
Affiliation: New Jersey Institute of Technology
Description: Calcium aluminate cement (CAC) is an alternative hydraulic cement that has a variety of specialized applications and uses, particularly in building chemistry and rapid repair applications. During hydration CAC undergoes a process known as conversion, during which metastable hydrates convert to denser stable hydrates. Since this happens after hardening of the cement matrix, the densification results in the formation of porosity and loss of strength. The rate at which conversion happens is temperature dependent and can take years to decades in standard outdoor conditions. Since the converted strength of the concrete systems will control the design of new concrete or concrete repair applications, determining when conversion has occurred and using accelerated methods for measuring the converted strength of CAC concrete are vital to ensure safety when using the material. Presented is a review of various methods of determining whether CAC concrete has undergone conversion, techniques for accelerated measurement of converted strength, and the impact of conversion on various properties. This presentation will help laboratory researchers, design engineers, testing agents, and contractors have a better understanding of the array of tools available for understanding conversion and converted strength in CAC concrete systems.
Calcium Aluminate Cement Concrete for Rapid Repair of Highway Infrastructure
Presented By: Jan Vosahlik
Description: A multi-year research project was carried out to characterize, evaluate and test calcium aluminate cement (CAC) concrete for rapid repairs. The primary objective of this study was to implement this alternative cementitious material into practice on the Illinois Tollways system. An assessment of previously constructed pavements utilizing CAC concrete was conducted, followed by several series of laboratory and field verification studies. Various aspects of CAC concrete were considered and investigated in this research program, including the effect of curing temperature and conversion, the use of latex, the use of shrinkage-reducing admixtures and saturated lightweight aggregate fines, and others. The conducted study showed that (1) the curing temperatures significantly affect both short- and long-term mechanical properties of CAC concrete; (2) latex is a very efficient component of the CAC concrete and can improve its durability; (3) traditional shrinkage-reducers do perform well in CAC concrete while the use of saturated lightweight aggregate can mitigate early-age volumetric instability; and (4) the use of polycarboxylate-based water reducers did negatively impact setting times while not improving workability to the expected degree. Ultimately, a performance-based specification was developed and implemented by the Illinois Tollway.
OPC-CSAB Blends for Durable Rapid Repair Applications
Presented By: Lisa Burris
Affiliation: Ohio State University
Description: Calcium Sulfoaluminate belite cements (CSAB) are known for their rapid setting and early strength development, two traits which are desirable for rapid repair applications and other construction processes where early strength generation is important. However, one of the demonstrated challenges associated with CSAB, when used as a 100% replacement of OPC in concrete mixtures, is its chloride penetration rates. Chloride ingress in CSAB cement matrices have been shown in the lab to progress at a order of magnitude greater rate than in OPC concrete, and could lead to rapid corrosion initiation in CSAB concrete placements. Thus, this work attempted to understand the effects of utilizing binary blends of OPC and CSAB cements to optimize properties for both materials for use in rapid repair applications - (accelerated setting time and strength gain for OPC mixtures without use of chloride accelerators, and increased chloride durability for CSA mixtures). Mixtures were created across a spectrum of CSA:OPC ratios to evaluate the ability of binary cement mixtures to ‘dial in’ desired properties in terms of setting times and early strength development, as well as to produce concrete with adequate resistance to chloride penetration. Results showed that CSAB reactions tended to dominate setting and early strength generation, and that CSAB + OPC mixtures generated greater long-term strengths compared to the 100% OPC concrete.
Accelerated and Non-Accelerated Carbonation in Alternative Cementitious Materials: Implications on Durability and Mechanical Properties
Presented By: Prasanth Alapati
Affiliation: Georgia Institute of Technology
Description: Understanding the rate and implications of carbonation on strength and durability in alternative cementitious materials (ACMs) is critical in designing and ‘green’ concretes for intended service lives. It is also important for understanding the potential of different concrete formulations for carbon sequestration. In this research, five commercially available ACMs including one calcium aluminate cements (CAC), one ternary blend of OPC, CAC and anhydrite (CACT), two calcium sulfoaluminate belite cements (CSA1 and CSA2), and one activated alumino-silicate binder (AA) were evaluated against one portland cement (OPC) under field and lab conditions; lab conditions included both ambient and accelerated carbonation exposures. Thermogravimetric analysis (TGA) and x-ray diffraction (XRD) techniques were used to understand the effect of accelerated carbonation on ACM paste composition. In addition, the carbonation front in concrete made with these ACMs was measured using phenolphthalein and rainbow indicators at regular intervals of exposure. Compressive strength of both carbonated and uncarbonated cement paste cubes made with these ACMs show the effects of carbonation on mechanical properties. The rate of carbonation in accelerated conditions in this CAC, CSA1, CSA2 and this AA systems were significantly higher than that of this CACT and OPC. The carbonation in the systems made with ACMs, especially these CSA1, CSA2, and AA results not only in a decrease in pH, which may lead to depassivation on embedded metal reinforcement, but is found to also cause decomposition of main strength giving hydration products. The effects of carbonation, including those on pore structure, will be discussed in more detail in the presentation.
Standardizing Corrosion Assessment Methods for Alternative Cementitious Systems
Presented By: Gokul Dev Vasudevan
Affiliation: Oregon State University