High-performance cementitious composites containing nanostructured carbon additives made from charred coal fines.

Carbon-based nanomaterials, such as carbon nanoplatelets, graphene oxide, and carbon quantum dots, have many possible end-use applications due to their ability to impart unique mechanical, electrical, thermal, and optical properties to cement composites. Despite this potential, these materials are rarely used in the construction industry due to high material costs and limited data on performance and durability. In this study, domestic coal is used to fabricate low-cost carbon nanomaterials that can be used economically in cement formulations. A range of chemical and physical processing approaches are employed to control the size, morphology, and chemical functionalization of the carbon nanomaterial, which improves its miscibility with cement formulations and its impact on mechanical properties and durability. At loadings of 0.01 to 0.07 wt.% of coal-derived carbon nanomaterial, the compressive and flexural strength of cement samples are enhanced by 24% and 23%, respectively, in comparison to neat cement. At loadings of 0.02 to 0.06 wt.%, the compressive and flexural strength of concrete composites increases by 28% and 21%, respectively, in comparison to neat samples. Additionally, the carbon nanomaterial additives studied in this work reduce cement porosity by 36%, permeability by 86%, and chloride penetration depth by 60%. These results illustrate that low-loadings of coal-derived carbon nanomaterial additives can improve the mechanical properties, durability, and corrosion resistance of cement composites.

Dataset documenting reaction-induced changes to five fractured foamed wellbore cement cores during CO2 fluid flow.

The integrity of wellbore cement is vital for the long-term success of applications such as enhanced oil recovery and carbon storage. Intact cemented well casings are crucial to preventing leakage and fluid migration, as well as maintaining safety of operations. To investigate the changes to fractures in foamed wellbore cement in a carbon storage scenario, four cores were fractured lengthwise and injected with deionized water at equilibrium with CO2. The experiment duration was five days for the first core and was increased for each successive test, with the final test lasting 20 days. The fractured cores were periodically imaged with a NorthStar M5000 Industrial Computed Tomography (CT) scanner, documenting the changes to the fracture during dissolution, as well as the reaction zone in the surrounding cement matrix. For two cores with the most robust reactions, the fracture and two reaction zones (proximal and distal to the fracture) were segmented from the raw CT data. They were quantified volumetrically and in the form of fracture aperture maps. A Local Cubic Law (LCL) modeling suite was used to map out localization of flow within the open portions of the fractures.

Parent Training for Dental Care in Underserved Children With Autism: A Randomized Controlled Trial.

OBJECTIVE: Children with autism spectrum disorder (ASD) have difficulty participating in dental care and experience significant unmet dental needs. We examined the efficacy of parent training (PT) for improving oral hygiene and oral health in underserved children with ASD. METHOD: Families of Medicaid-eligible children with ASD (ages 3-13 years, 85% boys, 62% with intellectual disability) reporting difficulty with dental care participated in a 6-month randomized controlled trial comparing PT (n = 60) with a psychoeducational dental toolkit (n = 59). Primary outcomes were parent-reported frequency of twice-daily toothbrushing and dentist-rated visible plaque. Secondary outcomes included parent-reported child behavior problems during home oral hygiene and dentist-rated caries. Dentists were blind to intervention assignment. Analyses were intention to treat. RESULTS: Retention was high at posttreatment (3 months, 93%) and 6-month follow-up (90%). Compared with the toolkit intervention, PT was associated with increased twice-daily toothbrushing at 3 (78% vs 55%, respectively; P < .001) and 6 (78% vs 62%; P = .002) months and a reduction in plaque at 3 months (intervention effect, -0.19; 95% confidence interval [CI], -0.36 to -0.02; P = .03) and child problem behaviors at 3 (-0.90; 95% CI, -1.52 to -0.28; P = .005) and 6 (-0.77; 95% CI, -1.39 to -0.14; P = .02) months. Comparatively fewer caries developed in children receiving the PT intervention over 3 months (ratio of rate ratios, 0.73; 95% CI, 0.54 to 0.99; P = .04). CONCLUSIONS: PT represents a promising approach for improving oral hygiene and oral health in underserved children with ASD at risk for dental problems.

Alteration of Fractured Foamed Cement Exposed to CO2-Saturated Water: Implications for Well Integrity.

Geologic CO2 storage (GCS) is a method to mitigate the adverse impact of global climate change. Potential leakage of CO2 from fractured cement at the wellbore poses a risk to the feasibility of GCS. Foamed cement is widely applied in deepwater wells where fragile geologic formations cannot support the weight of conventional cement. Thus, it is critical to know whether fractures in foamed cement self-seal in a similar manner as conventional cement systems. This study is the first to investigate the changes in physical and chemical attributes of foamed cement under dynamic flow conditions using CO2-saturated water. Self-sealing of fractures in the cement was observed at a solution flow rate of 0.1 mL/min and a pressure of 6.9 MPa. The formation of CaCO3 precipitates in pore spaces and fractures led to a decrease in permeability by 1 order of magnitude. The extents of self-sealing in foamed cement samples, specifically the 20 and 30% air volume formulations, were similar to that of conventional cements. We attribute this to the greater alteration depth in the foamed cement, which compensated for the reduced availability of Portlandite and higher initial porosity. The results can be used to evaluate the risk of leakage associated with foamed cement.