- Award ID(s):
- Publication Date:
- NSF-PAR ID:
- Journal Name:
- MRS Bulletin
- Page Range or eLocation-ID:
- 680 to 686
- Sponsoring Org:
- National Science Foundation
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This study characterized and evaluated the use of reclaimed fly ash (RFA) and reclaimed ground bottom ash (GBA) as alternative sources of supplementary cementitious materials (SCMs) for the production of concrete mixtures. Conventional Class F fly ash (FA) was also evaluated for comparison. The effects of SCM content on fresh and hardened properties of concrete were investigated by replacing 10%, 20%, and 30% of cement by mass. Characterization results showed that all three ashes met ASTM C618 chemical requirements (i.e., sum of SiO 2 + Al 2 O 3 + Fe 2 O 3 , CaO, SO 3 , moisture content, and loss of ignition) and 7- and 28-days strength activity index (SAI) requirements for Class F FA. In addition, RFA exhibited slightly higher SAI at 28 days of curing, followed by GBA and FA. In relation to fresh concrete properties, FA increased the concrete slump compared with the control mixture, whereas RFA and GBA decreased the concrete slump. However, GBA produced more significant slump decrements than RFA, which was attributed to the irregular angular particles of GBA. Generally, all the coal ashes produced decrements in air content compared with the control mixture. Comparatively, among the three ashes, GBA exhibited the highest 28-more »
Options for recycling fiber composite polymer (FCP) materials are scarce, as these materials cannot be normally recycled and are toxic when improperly disposed. Additionally, reducing water usage is an increasing concern, as the concrete industry currently uses 10% of the world’s industrial water. Therefore, building upon our previous work, this research explores the use of polymer hybrid carbon and glass composite waste products as reinforcements in high-pressure compacted cement. Our material used nearly 70% less water during manufacturing and exhibited improved durability and salt corrosion resistance. Compression strength tests were performed on high-pressure compacted materials containing 6.0 wt% recycled admixtures before and after saltwater aging, and the results showed that the material retained 90% of its original compression strength after aging, as it contained fewer pores and cavities. Our experimental work was supplemented by molecular dynamics. Simulations, which indicated that the synergetic effects of compaction and FCP admixture addition slowed the diffusion of corrosive salt ions by an average of 84%. Thus, our high-pressure compacted cement material may be suitable for extended use in marine environments, while also reducing the amount of commercial fiber composite polymer waste material that is sent to the landfill.
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High-pressure compacted cement samples containing 6% recycled admixtures retained 90% of their compression strength after salt aging.
The high-pressure compaction method utilized 70% less water during specimen fabrication.
Machine learning enables prompt prediction of hydration kinetics of multicomponent cementitious systems
Carbonaceous (e.g., limestone) and aluminosilicate (e.g., calcined clay) mineral additives are routinely used to partially replace ordinary portland cement in concrete to alleviate its energy impact and carbon footprint. These mineral additives—depending on their physicochemical characteristics—alter the hydration behavior of cement; which, in turn, affects the evolution of microstructure of concrete, as well as the development of its properties (e.g., compressive strength). Numerical, reaction-kinetics models—e.g., phase boundary nucleation-and-growth models; which are based partly on theoretically-derived kinetic mechanisms, and partly on assumptions—are unable to produce a priori prediction of hydration kinetics of cement; especially in multicomponent systems, wherein chemical interactions among cement, water, and mineral additives occur concurrently. This paper introduces a machine learning-based methodology to enable prompt and high-fidelity prediction of time-dependent hydration kinetics of cement, both in plain and multicomponent (e.g., binary; and ternary) systems, using the system’s physicochemical characteristics as inputs. Based on a database comprising hydration kinetics profiles of 235 unique systems—encompassing 7 synthetic cements and three mineral additives with disparate physicochemical attributes—a random forests (RF) model was rigorously trained to establish the underlying composition-reactivity correlations. This training was subsequently leveraged by the RF model: to predict time-dependent hydration kinetics of cement in new, multicomponent systems;more »
A role for terpenoid cyclization in the atom economical polymerization of terpenoids with sulfur to yield durable compositesRenewably-sourced, recyclable materials that can replace or extend the service life of existing technologies are essential to accomplish humanity's quest for sustainable living. In this contribution, remeltable composites were prepared in a highly atom-economical reaction between plant-derived terpenoid alcohols (10 wt% citronellol, geraniol, or farnesol) and elemental sulfur (90 wt%). Investigation into the microstructures led to elucidation of a mechanism for terpenoid polyene cyclization initiated by sulfur-centered radicals. The formation of these cyclic structures contributes significantly to understanding the mechanical properties of the materials and the extent to which linear versus crosslinked network materials are formed. The terpenoid–sulfur composites can be thermally processed at low temperatures of 120 °C without loss of mechanical properties, and the farnesol–sulfur composite so processed exhibits compressive strength 70% higher than required of concrete for residential building. The terpenoid–sulfur composites also resist degradation by oxidizing acid under conditions that disintegrate many commercial composites and cements. In addition to being stronger and more chemically resistant than some commercial products, the terpenoid–sulfur composites can be used to improve the acid resistance of mineral-based Portland cement as well. These terpenoid–sulfur composites thus hold promise as elements of sustainable construction on their own or as additives to extend themore »
The impacts of biomineralization and oil contamination on the compressive strength of waste plastic-filled mortar
Researchers have made headway against challenges of increasing cement infrastructure and low plastic recycling rates by using waste plastic in cementitious materials. Past studies indicate that microbially induced calcium carbonate precipitation (MICP) to coat plastic in calcium carbonate may improve the strength. The objective of this study was to increase the amount of clean and contaminated waste plastic that can be added to mortar and to assess whether MICP treatment enhances the strength. The performance of plastic-filled mortar was investigated at 5%, 10%, and 20% volume replacement for cement. Untreated, clean plastics at a 20% cement replacement produced compressive strengths acceptable for several applications. However, a coating of MICP on clean waste plastic did not improve the strengths. At 10% replacement, both MICP treatment and washing of contaminated plastics recovered compressive strengths by approximately 28%, relative to mortar containing oil-coated plastics. By incorporating greater volumes of waste plastics into mortar, the sustainability of cementitious composites has the potential of being improved by the dual mechanisms of reduced cement production and repurposing plastic waste.