Alternative binders have received attentions in recent years to provide sustainable cementitious binders for construction with lesser CO2 emissions and better/equivalent service lifespans. Some are alkali activated cements (AAC), calcium Sulfoaluminate cements (CSC), carbonated cements (CC), calcium aluminate cements (CAC), and magnesium phosphate cements (MPC). This mini-session sponsored by ACI 242 Committee will present the recent advances in alterative cements for construction. The objective of the mini-session is to improve students/engineers/scientists’ knowledge in concrete industry by providing current knowledge, recent advances, and potential applications of alternative cements that can be used in construction.
(1) Recognize concrete sustainability and durability advantages of alternative cements;
(2) Summarize current knowledge of alternative cements technologies suitable for construction;
(3) Identify potential applications of alternative cements in the concrete industry;
(4) Review recent advances in the science and technologies of alternative cements.
Alkali Activated Fly Ash for Wellbore Construction and Abandonment Applications
Presented By: Maria Juenger
Affiliation: University of Texas at Austin
Description: Millions of wellbores are spread across the globe for purposes such as oil and gas production, storage, or CO2 sequestration. The use of cementing material is a key component, either for the cement sheath in the construction processes or for the cement plug for the abandonment process. Poor cementation could jeopardize the wellbore integrity and lead to leakage incidents. Such incidents represent both environmental and health hazards in addition to significant economic burdens. One of the main reasons of poor cementation is the contamination of the cementing material with oil-based or synthetic-based muds (OBM/SBM). In this presentation, we introduce alkali activated fly ash (AAFA) as an alternative cementing material for wellbore construction and abandonment applications. The effects of the contamination with OBM/SBM on the compressive strength, tensile strength, and bond strength with steel of the AAFA were studied and compared to ordinary portland cement (OPC). The results show that AAFA outperforms OPC when subjected to OBM/SBM contamination.
Performance of Calcium Aluminate Cementitious Materials in the Presence of Deicing Salt
Presented By: Yaghoob Farnam
Affiliation: Drexel University
Description: This talk will cover the performance of two cementitious systems exposed to sodium chloride salt and thermal cycling. The two systems consisted of an ordinary portland cement (OPC) and a calcium aluminate cement (CAC). Several experimental techniques were conducted to evaluate the performance of OPC, and CAC pastes exposed to different concentrations of sodium chloride (NaCl) solution and thermal cycling. X-ray powder diffraction was used to study the hydration products present in hydrated pastes. Low-temperature differential scanning calorimetry was used to detect phase changes and study potential chemical interactions between pastes and NaCl solutions. Longitudinal guarded comparative calorimeter equipped with acoustic emission was used to detect phase changes and damage development in pastes saturated with NaCl solutions during thermal cycling. Unlike OPC pastes that can chemically interact with NaCl solutions to form a destructive chemical phase change at temperatures range between 0 oC and 10 oC, CAC pastes showed no chemical interactions with NaCl solutions, mainly due to possessing different chemistry than the OPC. As a result, no damage associated with the chemical phase change was observed in CAC pastes, indicating that the CAC is more resistance to NaCl damage than the OPC.
Role of Nano-particles in the Property Development of Alkali Activated Fly Ash
Presented By: Sulapha Peethamparan
Affiliation: Clarkson University
Description: The role of nano-particles in the hydration kinetics, microstructural evolution, compressive strength development, and composition of the reaction product is determined. The nanoparticles used are nano-silica, kaolinite clay, and C-S-H coated kaolinite clay. They were substituted for fly ash at 1% and 2% dosages to compare the impact of the particle dosage on the properties of the activated fly ash paste. Two types of alkali activator solutions, sodium hydroxide and sodium silicates, are used. Of all the nanoparticles, 2% nano-silica showed the highest compressive strength at both early age and later age.
Structure-Directing Agents for Controlled Zeolitization in Alkali-Activated Cements
Presented By: Wil Srubar
Affiliation: University of Colorado Boulder
Description: Alkali-activated binders are a new class of alternative cements that predominantly consist of amorphous aluminosilicate gels (e.g., CASH, NASH, CNASH) and, depending on material precursors and curing conditions, crystalline zeolitic phases. The nucleation, growth, and thermodynamic stability of zeolites has been shown to affect short- and long-term mechanical and durability properties of alkali-activated cements (AACs). This presentation will highlight recent research aimed and understanding and controlling the nucleation, growth, and stability of zeolites using novel structure-directing agents that aid in the precipitation and stabilization of preferential zeolitic phases in metakaolin-based AACs.