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Portland cement concrete, the most used manufactured material in the world, is a significant contributor to anthropogenic carbon dioxide (CO2) emissions. While strategies such as point-source CO2 capture, renewable fuels, alternative cements, and supplementary cementitious materials can yield substantial reductions in cement-related CO2 emissions, emerging biocement technologies based on the mechanisms of microbial biomineralization have the potential to radically transform the industry. In this work, we present a review and meta-analysis of the field of biomineralized building materials and their potential to improve the sustainability and durability of civil infrastructure. First, we review the mechanisms of microbial biomineralization, which underpin our discussion of current and emerging biomineralized material technologies and their applications within the construction industry. We conclude by highlighting the technical, economic, and environmental challenges that must be addressed before new, innovative biomineralized material technologies can scale beyond the laboratory.

At the intersection of synthetic biology and materials science, the field of engineered living materials (ELMs) has evolved into a new, standalone discipline. The fusion of bioengineering's design-build-test-learn approaches with classical materials science has yielded breakthrough innovations in the synthesis of complex, biologically active materials for functional applications in therapeutics, electronics, construction, and beyond. However, the transdisciplinary nature of the ELM field - and its rapid growth - has made holistic comprehension of achievements related to the tools, techniques, and applications of ELMs difficult across disciplines. To this end, this review proposes an emergent taxonomy of ELM research and uses the categorization to discuss current trends and state-of-the-art advancements, significant opportunities, and imminent challenges for scientists and engineers in the field.

The ability of an ice-binding protein (IBP) from Marinomonas primoryensis (MpIBP) to influence ice crystal growth and structure in nonphysiological pH environments was investigated in this work. The ability for MpIBP to retain ice interactivity under stressed environmental conditions was determined via (1) a modified splat assay to determine ice recrystallization inhibition (IRI) of polycrystalline ice and (2) nanoliter osmometry to evaluate the ability of MpIBP to dynamically shape the morphology of a single ice crystal. Circular dichroism (CD) was used to relate the IRI and DIS activity of MpIBP to secondary structure. The results illustrate that MpIBP secondary structure was stable between pH 6 and pH 10. It was found that MpIBP did not interact with ice at pH ≤ 4 or pH ≥ 13. At 6 ≤ pH ≥ 12 MpIBP exhibited a reduction in grain size of ice crystals as compared to control solutions and demonstrated dynamic ice shaping at 6 ≤ pH ≥ 10. The results substantiate that MpIBP retains some secondary structure and function in non-neutral pH environments; thereby, enabling its potential utility in nonphysiological materials science and engineering applications.

Summary Living building materials (LBMs) were engineered that are capable of both biological and structural functions. LBMs were created by inoculating an inert structural sand-hydrogel scaffold with Synechococcus sp. PCC 7002, a photosynthetic cyanobacterium. The scaffold provided structural support for Synechococcus, which toughened the hydrogel matrix via calcium carbonate biomineralization. Temperature and humidity switches were utilized to regulate the metabolic activity of the microorganisms and achieve three successive regenerations of viable LBMs from one parent generation. Microbial viability in LBMs maintained in at least 50% relative humidity for 30 days was 9%–14%, which far exceeded literature values of microorganisms encapsulated in cementitious materials for similar timeframes (0.1%–0.4%). While structural function was maximized at ultradesiccated conditions, prolonged dehydration compromised microbial viability. Despite this tradeoff in biological-structural function, LBMs represent a platform technology that leverages biology to impart novel sensing, responsive, and regenerative multifunctionality to structural materials for the built environment.

Microbial production of exogenous organic compounds is challenging as biosynthetic pathways are often complex and produce metabolites that are toxic to the hosts. Biogenic styrene is an example of this problem, which if addressed could result in a more sustainable supply of this important component of the plastics industry. In this study, we engineered Escherichia coli for the production of styrene. We systematically optimized the production capability by first screening different pathway expression levels in E. coli strains. We then further designed and constructed a transcription regulator library targeting 54 genes with 85,420 mutations, and tested this library for increased styrene resistance and production. A series of tolerant mutants not only exhibited improved styrene tolerance but also produced higher styrene concentrations compared to the parent strain. The best producing mutant, ST05 LexA_E45I, produced a 3.45-fold increase in styrene compared to the parent strain. The produced styrene was extracted via gas stripping into dodecane and used in a direct free radical synthesis of polystyrene.

We demonstrate for the first time that the morphology and nanomechanical properties of calcium carbonate (CaCO3) can be tailored by modulating the precipitation kinetics of ureolytic microorganisms through genetic engineering. Many engineering applications employ microorganisms to produce CaCO3. However, control over bacterial calcite morphology and material properties has not been demonstrated. We hypothesized that microorganisms genetically engineered for low urease activity would achieve larger calcite crystals with higher moduli. We compared precipitation kinetics, morphology, and nanomechanical properties for biogenic CaCO3 produced by two Escherichia coli (E. coli) strains that were engineered to display either high or low urease activity and the native producer Sporosarcina pasteurii. While all three microorganisms produced calcite, lower urease activity was associated with both slower initial calcium depletion rate and increased average calcite crystal size. Both calcite crystal size and nanoindentation moduli were also significantly higher for the low-urease activity E. coli compared with the high-urease activity E. coli. The relative resistance to inelastic deformation, measured via the ratio of nanoindentation hardness to modulus, was similar across microorganisms. These findings may enable design of novel advanced engineering materials where modulus is tailored to the application while resistance to irreversible deformation is not compromised.

Self-healing under multiple damage cycles is critical to the serviceability of concrete structures. This article explores crack closure and recovery of mechanical and permeability properties after multiple (i.e., three) damage cycles by comparing autogenous and bio-based self-healing in concrete using a combination of steel and PVA fibers, superabsorbent polymer (SAP), and bacteria immobilized in biochar. Swelling of SAP upon exposure to water and enhancement of hydration by curing action of SAP led to improved blocking and filling of cracks compared to a control (plain concrete); however, the effectiveness of autogenous crack closure (by only SAP or SAP plus fibers) was limited to narrow surface cracks ( 600 μm) and internal micro-cracks compared to that attained by the autogenous mechanism alone in control and concrete containing only SAP and fiber. Effectiveness of crack filling by immobilized spores in biochar was found to be consistently higher than concrete with directly added spores and SAP through all three cycles of damage and healing. Precipitation of calcium carbonate crystals in internal cracks and interfacial zones around PVA fiber and aggregate in concrete with biochar immobilized spores resulted in high recovery of strength and permeability compared to the autogenous healing mechanism in control and concrete with SAP and fiber. However, it was found that macro-voids formed by SAP with a larger average particle size and higher swelling capacities affected total permeability and permeability recovery after repeated healing. Overall, we conclude that cementitious systems with biochar-immobilized bacteria, SAP, and fibers can enhance self-healing and impart improved durability to concrete structures.

The compressive strength and selected fresh-state responses to incorporating acid-modified granular activated carbon (GAC) in cement mortars, were compared to physical cement behaviors associated with the incorporation of otherwise unmodified GAC and a commercial polycarboxylate superplasticizer. Specific surface area of unmodified and acidified GAC, porosity, pH at charge neutrality (pHPZC), and surface-associated functional groups were compared. Fresh- and hardened-state responses were observed, including slump, setting time, zeta potential, and compressive strength. Results suggest that substituting 1% of the fine aggregate mass with GAC particles that had been pre-treated in nitric acid, can improve compressive strength and workability of cement mortar.

Low-total-force contact resonance force microscopy (LTF-CRFM), an atomic force microscopy method, is introduced as a non-destructive means to quantify the local viscoelastic loss tangent (δ) of cellulose nanofibrils (CNFs). The method limits static and dynamic forces during measurement to minimize substrate and geometry effects and to reduce the potential for stress-induced CNF damage. LTF-CRFM uses Brownian motion to achieve the thermally-limited lowest dynamic force, while approaching adhesive pull-off to achieve the low static force. LTF-CRFM measurements were shown to generate analyzable data without evidence of nonlinear artifacts and without damage to the CNF over static forces ranging from 11.6 nN to 84.6 nN. The measured δ of CNFs was 0.015 ± 0.0094, which is the first reported δ measurement of an isolated CNF. Finally, LTF-CRFM successfully mapped δ along the length of CNFs to determine that kink defects along the CNF do not impart a local viscoelastic property change at the length scale of the measurement.

Concrete mixtures are complex material systems with a multitude of characteristics that decision-makers may deem important. These characteristics can include economic, environmental, mechanical, and durability-related properties of a concrete mixture. However, traditional concrete mixture design typically employs long-standing heuristics, which satisfy requirements for physical characteristics but are unable to minimize specific characteristics, such as the cost or carbon footprint of the concrete mixture. This work considers these performance characteristics by implementing simulation-optimization as a new paradigm for designing concrete mixtures. The utility of the simulation-optimization framework is tested for several concrete design case studies that simultaneously consider compressive strength, embodied carbon, service life, and cost. Results from these scenarios demonstrate that the local conditions of the case study dictate the most important parameters of the simulation-optimization (i.e., relative constituent costs, in situ service-life conditions). Out of all other parameters, constituent cost and service-life conditions impact the set of optimal concrete mixture designs in terms of the types and quantities of mixture ingredients that are utilized. We present a simulation-optimization framework that is demonstrated herein to be a holistic design tool that allows designers to quantify and visualize tradeoffs between critical concrete performance metrics. Such a tool can be used to precision-tailor low-carbon concrete mixtures to the exact preferences of the designer.

Floor space is a key variable used to understand the energy and material demands of buildings. Using recent data sets of building footprints, we employ a random forest regression model to estimate the total floor space (conditioned and unconditioned) of the North American building stock. Our estimate for total floor space in 2016 is 88033 (+15907/-21861) million m2, which is 2.9 times higher than current estimates from national statistics offices. We also show how floor space per capita (m2 cap-1) is not constant across the North American region, highlighting the heterogeneous nature of building stocks. As a critical variable in integrated assessment models to project energy and material demands, this result suggests that there is much more unconditioned floor space than previously realized. Furthermore, when estimating material stocks, flows, and associated embodied carbon emissions, total floor space per-capita estimates, such as those presented in this study, offer a more comprehensive approach in comparison to national statistics that do not capture unconditioned floor space. This result also calls for an investigation as to why there is such a vast difference between estimates of conditioned and total floor space.

Engineering design has drawn inspiration from naturally occurring structures to advance manufacturing processes and products, termed biomimetics. For example, the mantis shrimp, order Stomatopoda, is capable of producing one of the fastest appendage strikes in the world with marginal musculoskeletal displacement. The extreme speed of the mantis shrimp's raptorial appendage is due to the non-Euclidean hyperbolic paraboloid (i.e., saddle) shape within the dorsal region of the merus, which allows substantial energy storage through compression in the sagittal plane. Here, investigation of 3D printed synthetic geometries inspired by the mantis shrimp saddle geometry has revealed insights for elastic energy storage (i.e., spring-like) applications. Saddles composed of either a stiff or a flexible resin were investigated for spring response to explore the geometric effects. By modulating the saddle geometry and testing the spring response, it was found that, for the stiff resin, the spring constant was improved as the curvature of the contact and orthogonal faces were maximized and minimized, respectively. For the flexible resin, it was found that the spring constant increased by less than 250 N/mm as the saddle geometry changed, substantiating that the flexible component of mantis saddles does not contribute to energy storage capabilities. The geometries of two saddles from the mantis shrimp species Odontodactylus scyllarus were estimated and exhibited similar trends to manufactured saddles, suggesting that modulating saddle geometry can be used for tailored energy storage moduli in spatially constrained engineering applications.

We investigated the sulfuric acid resistance of low-calcium alkali-activated materials (i.e., geopolymers) supplemented with an iron mineral admixture (i.e., hematite). Geopolymers without and with 5% hematite were produced at two alkali contents (Na:Al = 0.86 and 1.39). Acid degradation reactions were comprehensibly studied through three replenishes of acid. Results demonstrate that hematite is chemically active upon acid exposure yielding a short-term increase in acid neutralization capacity. Prolonged acid resistance was enhanced in high alkali content formulations with hematite. Acid exposure revealed minimal changes to mineralogy, molecular structure, and micro-scale porosity in these samples, resulting in less dealumination and silicon leaching. Thus, results indicate that the acid buffering capacity of geopolymers, specifically at higher alkali content formulations, increases due to the addition of hematite. The increased buffering capacity leads to lower degrees of dealumination of the N-A-S-H cementitious binder. These results are important as they may help explain the increased acid durability of alkali-activated materials synthesized from industrial aluminosilicate precursors (e.g., slag, fly ash, lateritic clays) that may contain iron minerals.

High-performance building envelopes are designed to achieve target reductions in operational energy (OE). However, these wall assemblies often require initial, upfront investments in mater...

Experimental evidence of a new acid degradation mechanism in alkali-activated cements (AACs) micro-doped with copper (Cu) and cobalt (Co) is presented in this work. Cu and Co incorporation into binary metakaolin and basic oxygen furnace (BOF) slag-based AACs reduced bulk permeable porosity and acid penetration and retarded the formation of calcium sulfate phases upon exposure to acid. Analysis of microstructural evolution and elemental mobility using X-ray diffraction and electron microprobe analysis (EMPA) showed that Cu and Co doping was associated with major differences in AAC leaching patterns when exposed to sulfuric acid. Converging lines of evidence suggest that acid resistance is improved by the preferential mobilization of Cu and Co, along with other multivalent cations (i.e., magnesium), at the acid degradation front(s), stabilizing the AAC binder and inhibiting further deterioration.

Ureolytic bacteria (e.g., Sporosarcina pasteurii) can produce calcium carbonate (CaCO3). Tailoring the size and shape of biogenic CaCO3 may increase the range of useful applications for these crystals. However, wild type Sporosarcina pasteurii is difficult to genetically engineer, limiting control of the organism and its crystal precipitates. Therefore, we designed, constructed, and compared different urease operons and expression levels for CaCO3 production in engineered Escherichia coli strains. We quantified urease expression and calcium uptake and characterized CaCO3 crystal phase and morphology for 13 engineered strains. There was a weak relationship between urease expression and crystal size, suggesting that genes surrounding the urease gene cluster affect crystal size. However, when evaluating strains with a wider range of urease expression levels, there was a negative relationship between urease activity and polycrystal size (e.g., larger crystals with lower activity). The resulting range of cryst...

In this review, we present a meta-analysis of experimental data concerning chloride transport in alkali-activated cement (AAC) paste, mortar, and concrete. Sixty-six (66) studies were reviewed with a primary focus on measurement methodology, mixture design, and process-structure-property relationships related to microstructural development (i.e., porosity, pore size distribution), chloride diffusion, and chloride binding. In general, this review elucidates that aluminosilicate precursors with high amorphous contents and increased fineness that are activated with solutions of high alkalinity (Na:Al ≥ 0.75) and silica content (Si:Al ≥ 1.5) in combination with heat-curing (>40 °C) lead to microstructural characteristics (e.g., binder gel chemistries) that improve chloride durability, even though interactions between these factors are not well understood. Descriptive statistics of reported AAC paste porosities and AAC concrete chloride diffusion coefficients by aluminosilicate precursor (i.e., fly ash, slag, calcined clay, natural clay, binary blends) are presented, along with a summative discussion regarding new opportunities for advancing current scientific understanding of chloride transport in AACs.

The nanoscale hygromechanical behavior of lignin is presented in this work. Three atomic force microscopy experimental methods were used to correlate moisture sorption of lignin to its mechanical behavior. First, sorption isotherms were established using cantilever mass sensing and subsequently predicted using the Guggenheim–Anderson–de Boer model. The sorption isotherms of lignin particles followed a repeatable and cyclic trend reaching a maximum moisture content of ≈ 17% at ≈ 79% relative humidity (RH). Second, 3D nanomechanical contrast images were obtained using contact resonance force microscopy (CR-FM) to observe the hygromechanical response of lignin over three RH cycles. Finally, force volume mapping and the Hertz model were used to compute the elastic modulus of lignin as a function of moisture content. As RH increased, CR-FM measurements revealed initial topographical heterogeneity, as well as notable surface softening, especially in initially smooth domains. The average elastic modulus of the smooth domain decreased from 9.0 to 4.3 to 2.4 GPa as the moisture content increased from 0.024 to 9.1 to 17.3%, respectively. Cyclic measurements confirm that the elastic modulus of lignin rebounds upon moisture desorption.

A comprehensive review of optimization research concerning the design and proportioning of concrete mixtures is presented herein. Mixture design optimization is motivated by an ever-increasing need for designers and decision-makers to proportion concrete mixtures that satisfy multiple – oftentimes competing – performance requirements, including cost, workability, mechanical properties, durability, and environmental sustainability. In this review, we first discuss common mathematical problem formulations, decisions, objectives, and constraints pertaining to concrete mixture design optimization. Subsequently, we examine the types of models employed to approximate properties of concrete, which include a variety of linear combination, statistical, machine learning, and physics-based models that are required to optimize the proportions of a mixture. We then review and discuss computational methods used to optimize concrete mixtures in the context of surveyed literature. Finally, we highlight and discuss current trends and opportunities for advancing the field of concrete mixture design optimization in context of the current state of the art.

Life cycle assessment (LCA) is an emerging methodological tool used in building design and construction to quantify the environmental impacts of materials, components, and whole buildings. While calculation of embodied cradle-to-gate greenhouse gas (GHG) emissions is commonplace for ordinary portland cement (OPC) structural concrete elements in building-related LCAs, the carbon dioxide (CO2) sequestered by in situ carbonation of exposed OPC concrete is often neglected because the quantity of sequesterable CO2 is assumed trivial compared to the initial GHG emissions (kg CO2e) associated with their manufacture. Using a screening cradle-to-gate LCA and a previously developed and validated CO2 sequestration model for OPC concrete, this paper quantifies and compares estimates of the initial CO2e emissions to the CO2 sequestration potential of several OPC concrete elements at both finite (25 years) and infinite time intervals. The results demonstrate that, depending on cement type, compressive strength, structural geometry, and time, approximately 19%—a non-trivial sum—of initial CO2e emissions could be recoverable via CO2 sequestration for the concrete elements considered herein. Notably, however, concrete elements that sequester the most CO2 do not always result in the lowest net CO2e emissions.

Porosity and strength responses that result from the substitution of fine sand aggregate with similarly sized granular activated carbon (GAC) particles, were studied in cements commonly used in North America. In addition to changes in density and mechanical properties, pore structure responses were analyzed using mercury intrusion porosimetry (MIP). Increases in both compressive and tensile strength resulted from GAC incorporation, where sand replacement was 2% by mass or lower; porosity and critical pore entry diameter also decreased near this range (

Efficiency in maintaining indoor air quality is central to the operation of high-performance buildings. The purpose of this work was to investigate the effect of airflow velocities generated by a low-power annular, multi-orifice synthetic jet actuator (SJA) on the degradation rate of a model air pollutant, nitrogen dioxide (NO 2 ), by a photocatalytic surface. In this study, the active flow fields generated by the SJA were first characterized, and the effect of SJA-to-wall distance was analyzed as the airflow impinged on a wall of varying surface textures. Second, the impact of flow characteristics, namely surface velocity and velocity distribution, on the removal rates of NO 2 by the photocatalytic surface was investigated in a closed chamber. Results showed that a SJA-to-wall (L) distance of 315 mm had the greatest reduction (dampening) on peak airflow velocities. Also, the surface with the highest roughness used in this study resulted in increased turbulence at the wall surface. The use of the SJA enhanced the removal rate of NO 2 compared to passive (control) conditions. Increases in air velocity, however, did not monotonically enhance the removal rate of NO 2 . The highest removal rate ( k = 0.0013 min −1 ) was measured at L = 315 mm, where the highest velocity dampening was observed. It also corresponded to an average surface velocity of approximately 0.1 m/s across the photocatalytic surface.

A simple mathematical model that calculates the theoretical carbon sequestration potential of exposed ordinary portland cement (OPC) concrete is presented, validated, and implemented herein. OPC concrete sequesters non-trivial amounts of carbon dioxide (CO2) via carbonation – a chemical reaction between cement paste and atmospheric CO2. Formulated by the reaction chemistries of cement hydration and carbonation, the model accounts for cement type and content, exposure, time, and type and quantity of supplementary cementitious materials (SCMs). Once validated with data from literature, the model is implemented to investigate the effect of these factors and the influence of compressive strength and geometry, namely surface-area-to-volume (SA/V) ratio, on total carbon sequestration (kg CO2) of exposed concrete elements. Results demonstrate that (a) low tetracalcium aluminoferrite (C4AF) cements, (b) compressive strength, (c) high CO2 exposure, (d) no SCMs, (e) time, (f) high SA/V ratios, and (g) indoor environments enhance the in situ carbon sequestration of exposed OPC concrete.

This paper investigates the early-age dynamics of mineral formation in metakaolin-based alkali-activated cements. The effects of silica availability and alkali content on mineral formation were investigated via X-ray diffraction and solid-state 29 Si magic-angle spinning nuclear magnetic resonance spectroscopy at 2, 7, 14, and 28 days. Silica availability was controlled by using either liquid- (immediate) or solid-based (gradual) sodium silicate supplements. Mineral (zeolitic) and amorphous microstructural characteristics were correlated with observed changes in bulk physical properties, namely shrinkage, density, and porosity. Results demonstrate that, while alkali content controls the mineralization in immediately available silica systems, alkali content controls the silica availability in gradually available silica systems. Immediate silica availability generally leads to a more favorable mineral formation as demonstrated by correlated improvements in bulk physical properties.

This chapter presents an overview of the application of superabsorbent polymers (SAPs) from synthetic, biobased, and hybrid sources and expounds on their role in mitigating early- and late-age cracking in cement-based materials. Synthetic, petroleum-based SAPs have been applied for many years as an internal curing agent in low water-to-cement ratio concretes to reduce damage due to autogenous shrinkage. Due to recent demands for more renewable materials and concrete additives, SAPs from renewable resources have been increasingly researched, developed, and applied to mitigate early- and late-age cracking in concrete. This chapter surveys and discusses classes of natural polymers (i.e., polysaccharides and polypeptides) that have been used to create hybrid and biobased SAPs and those that merit further exploration for use in cementitious materials. In addition, the potential for expanding the utility of SAPs, namely, exploiting SAPs for late-age crack mitigation, imparting multiple functionalities, and standardizing methods of their use in concrete, are highlighted and discussed herein.

Transparent wood composites (TWCs) are a new class of light-transmitting wood-based materials composed of a delignified wood template that is infiltrated with a refractive- index-matched polymer resin. Recent research has focused primarily on the fabrication and characterization of single-ply TWCs. However, multi-ply composite laminates are of interest due to the mechanical advantages they impart compared to the single ply. In this work, 1- and 2-ply [0&deg, /90&deg, ] TWC laminates were fabricated using a delignified wood template (C) and an acetylated delignified wood template (AC). The optical and mechanical properties of resultant C and AC TWC laminates were determined using ultraviolet-visible spectroscopy (UV-Vis) and tensile testing (5&times, replicates), respectively. In addition, the ability of classical lamination plate theory and simple rule of mixtures to predict multi-ply tensile modulus and strength, respectively, from ply-level mechanical properties were investigated and are reported herein. Experimental results highlight tradeoffs that exist between the mechanical and optical responses of both unmodified and chemically modified TWCs. Template acetylation reduced the stiffness and strength in the 0&deg, fiber direction by 2.4 GPa and 58.9 MPa, respectively, compared to the unmodified samples. At high wavelengths of light (&gt, 515 nm), AC samples exhibited higher transmittance than the C samples. Above 687 nm, the 2-ply AC sample exhibited a higher transmittance than the 1-ply C sample, indicating that thickness-dependent optical constraints can be overcome with improved interfacial interactions. Finally, both predictive models were successful in predicting the elastic modulus and tensile strength response for the 2-ply C and AC samples.

The experimental and theoretical potential of using calcined waste eggshells (CWEs) to remove sulfate from sulfate-laden concrete mixing water was investigated in this work. Waste eggshells...

This work presents experimental evidence that confirms the potential for two specific zeolites, namely chabazite and faujasite (with a cage size ~2–13 Å), to adsorb small amounts of chloride from a synthetic alkali-activated cement (AAC) pore solution. Four synthetic zeolites were first exposed to a chlorinated AAC pore solution, two faujasite zeolites (i.e., FAU, X-13), chabazite (i.e., SSZ-13), and sodium-stabilized mordenite (i.e., Na-Mordenite). The mineralogy and chemical composition were subsequently investigated via X-ray diffraction (XRD) and both energy- and wavelength-dispersive X-ray spectroscopy (WDS), respectively. Upon exposure to a chlorinated AAC pore solution, FAU and SSZ-13 displayed changes to their diffraction patterns (i.e., peak shifting and broadening), characteristic of ion entrapment within zeolitic aluminosilicate frameworks. Elemental mapping with WDS confirmed the presence of small amounts of elemental chlorine. Results indicate that the chloride-bearing capacity of zeolites is likely dependent on both microstructural features (e.g., cage sizes) and chemical composition.