RESUMEN

Fly Ash (FA), an abundant by-product with no carbon footprint, is a potential stabilizer for enhancing the physical and geotechnical properties of pavement aggregates. In this research, FA was used in different ratios to stabilize crushed brick (CB) and reclaimed asphalt pavement (RAP) for pavement base/subbase applications. The FA stabilization of CB and RAP was targeted to improve the strength and durability of these recycled materials for pavement base/subbase applications. The Unconfined Compressive Strength (UCS) and resilient modulus (MR) development of the stabilized CB and RAP aggregates was studied under room temperature and at an elevated temperatures of 40°C, and results compared with unbound CB and RAP. Analysis of atomic silica content showed that when the amount of silica and alumina crystalline was increased, the soil structure matrix deteriorated, resulting in strength reduction. The results of UCS and MR testing of FA stabilized CB and RAP aggregates indicated that FA was a viable binder for the stabilization of recycled CB and RAP. CB and RAP stabilized with 15% FA showed the highest UCS results at both room temperature and at 40°C. Higher temperature curing was also found to result in higher strengths.

RESUMEN

In this research, a low-carbon stabilization method was studied using Recycled Asphalt Pavement (RAP) and Fly Ash (FA) geopolymers as a sustainable pavement material. The liquid alkaline activator (L) is a mixture of sodium silicate (Na2SiO3) and sodium hydroxide (NaOH), and high calcium FA is used as a precursor to synthesize the FA-RAP geopolymers. Unconfined Compressive Strength (UCS) of RAP-FA blend and RAP-FA geopolymer are investigated and compared with the requirement of the national road authorities of Thailand. The leachability of the heavy metals is measured by Toxicity Characteristic Leaching Procedure (TCLP) and compared with international standards. The Scanning Electron Microscopy (SEM) analysis of RAP-FA blend indicates the Calcium Aluminate (Silicate) Hydrate (C-A-S-H) formation, which is due to a reaction between the high calcium in RAP and high silica and alumina in FA. The low geopolymerization products (N-A-S-H) of RAP-FA geopolymer at NaOH/Na2SiO3=100:0 are detected at the early 7days of curing, hence its UCS is lower than that of RAP-FA blend. The 28-day UCS of RAP-FA geopolymers at various NaOH/Na2SiO3 ratios are significantly higher than that of the RAP-FA blend, which can be attributed to the development of geopolymerization reactions. With the input of Na2SiO3, the highly soluble silica from Na2SiO3 reacted with leached silica and alumina from FA and RAP and with free calcium from FA and RAP; hence the coexistence of N-A-S-H gel and C-A-S-H products. Therefore, the 7-day UCS values of RAP-FA geopolymers increase with decreasing NaOH/Na2SiO3 ratio. TCLP results demonstrated that there is no environmental risk for both RAP-FA blends and RAP-FA geopolymers in road construction. The geopolymer binder reduces the leaching of heavy metal in RAP-FA mixture. The outcomes from this research will promote the move toward increased applications of recycled materials in a sustainable manner in road construction.

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RESUMEN

Background: Falls and their consequences are serious health problems among the elderly. In Thailand, temples are where the elderly often visit to pray and socialize with others. However, studies related to characteristics and severity of falls within temples are limited. Objective: To study characteristics of falls (falls, near falls, and fall-related injuries) and severity of falls among the elderly in temples. Material and Method: A cross-sectional analytic study. Subject is elderly population group (aged 60 and above) in the province of Nakhon Ratchasima (17 districts) who attend temples at least once a week (22 temples). The survey was conducted by questionnaires that required personal information, medical condition, frequency of fall, fall description, fall location, time of fall, and severity after a fall. Results: Total 742 subjects aged adult were screened through questionnaires. A number of 451 persons were reported to have fallen in temples, which was 60.8% of the population, whereas 76.1% of the population was said to have fallen or nearly fell. Most of the subjects have fallen only once in the past year by tripping (55%) and slipping (28.7%). Most of the falls occur outdoors (48.0%) rather than indoors (30.4%) and in the bathroom (21.6%). Some adults do not have any fall-related injuries (33.5%), though most of them experience muscle pain (27.3%). The rate of fractures among the elderly was 7.1%. A total of 117 subjects required hospitalization (25.9%). Upon being discharged from the hospital, 24.8% of the subjects were required to continue recovery at home. Conclusion: The number of near falls and falls among Thai older adults in temples are quite high and very concerning. Such numbers are alarming and indicate that the elderly attending services and activities in temples require appropriate facilities and close attention from accompanying and surrounding persons. This study presented fundamental yet beneficial information which is useful for the architectural, engineering, and public health development for the elderly.

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