A Guideline For Pedagogical Approaches To “Zài(?)”And “Yòu(?)” In Mandarin ChineseFor Thai University Students

The purpose of the study is to provide a guideline for the pedagogical approaches to teach Thai students the grammar of the Chinese adverbs “zài” and “yòu”.  Questionnaire results revealed that the reasons for the misuse of “zài” and “yòu” by Thai university students can be classified into three causes: (1) “zài” and “yòu” suggest repeatedness and both of them can be literally translated into the Thai /Ik/,(2) the complicated semantic characteristics of “zài” and “yòu” themselves and (3) the situation in the process of “zài” and “yòu” acquisition being not completed.  In terms of pedagogical approaches, this study presents an appropriate sequence for the learning of the adverbs “zài” and “yòu” in Mandarin Chinese according to the frequency of occurrence and the frequency of error. Furthermore, the study suggests that teachers should first teach the grammar points that are used more frequently and have more straightforward semantics familiar to most students. Those used infrequently and likely to cause errors should be taught later

Chloride ingress into marine exposed concrete: A comparison of empirical- and physically- based models

In establishing the reliability of performance-related design methods for concrete – which are relevant for resistance against chloride-induced corrosion - long-term experience of local materials and practices and detailed knowledge of the ambient and local micro-climate are critical. Furthermore, in the development of analytical models for performance-based design, calibration against test data representative of actual conditions in practice is required. To this end, the current study presents results from full-scale, concrete pier-stems under long-term exposure to a marine environment with work focussing on XS2 (below mid-tide level) in which the concrete is regarded as fully saturated and XS3 (tidal, splash and spray) in which the concrete is in an unsaturated condition. These exposures represent zones where concrete structures are most susceptible to ionic ingress and deterioration. Chloride profiles and chloride transport behaviour are studied using both an empirical model (erfc function) and a physical model (ClinConc). The time dependency of surface chloride concentration (Cs) and apparent diffusivity (Da) were established for the empirical model whereas, in the ClinConc model (originally based on saturated concrete), two new environmental factors were introduced for the XS3 environmental exposure zone. Although the XS3 is considered as one environmental exposure zone according to BS EN 206-1:2013, the work has highlighted that even within this zone, significant changes in chloride ingress are evident. This study aims to update the parameters of both models for predicting the long term transport behaviour of concrete subjected to environmental exposure classes XS2 and XS3

Probabilistic model for single and multiple action costs in maintaining both condition and safety of deteriorating reinforced concrete bridges

Single and multiple cyclic maintenance actions (called essential and preventive maintenance actions) to maintain both condition and safety of deteriorating reinforced concrete bridges exposed to chloride attack are proposed to remedy the issues in the previous studies. The essential maintenance consists of Minor concrete repair (CR) and Do nothing and rebuild (RB), whereas the preventive maintenance consists of Silane treatment (SL) and Cathodic protection (CP). For these tasks, a computational platform is developed for not only determining the interaction between condition index and safety index of deteriorating bridges with maintenance, but also calculating the present value of expected maintenance costs. From the study, the combined maintenance cost of SL, CR and RB are found similar to that of CR alone in the early age, and to that of RB alone after the early age. This occurs, because the condition index of bridges with SL alone is low in the early age, whereas their safety index with SL alone is low after the early age. Moreover, the preventive maintenance by SL not only helps improve condition and safety, but also reduce the cumulative cost of combined maintenance. For applying CR or CP alone, RB is required in case that the initial condition index is below the target value for applying CR or CP. The present value of cumulative maintenance cost for the combination of CP with CR and RB is higher than that for CP alone, because more cost is added for applying CR and RB. It is not recommended to combine CP with CR or RB, because of two reasons. First, the maintenance cost of CP, CR, or RB is very high causing high cumulative cost. Second, although CP is better than SL in reducing the probability of applying CR and RB, the maintenance cost of CP is much higher than SL. Hence, SL is more appropriate than CP in combining with CR and RB. Moreover, it is advantageous to combine maintenance actions, because of two reasons. First, bridges, which have such a low condition in the early age that CR cannot be applied, can be applied after maintenance. Second, the safety of bridges is always satisfactory by applying RB. Finally, further studies are recommended

Use of a Piezoelectric Bender Element for the Determination of Initial and Final Setting Times of Metakaolin Geopolymer Pastes, with Applications to Laterite Soils

This study proposes the use of a non-destructive testing technique, based on piezoelectric bender element tests, to determine the initial and final setting times of metakaolin geopolymer pastes. (1) Background: Metakaolin geopolymer is a new eco-friendly building material that develops strength rapidly and is high in compressive strength. (2) Methods: The initial and the final setting times were investigated via bender element and Vicat needle tests. Metakaolin powder was prepared by treating kaolin at 0, 200, 800, 1000, and 1200 °C. All metakaolin powder samples were then mixed with geopolymer solution at different mixing ratios of 0.8:1.0, 1.0:1.0, 1.2:1.0, and 1.5:1.0. The geopolymer solution was prepared by adding 10 normal concentrations of sodium hydroxide (10 N NaOH) to sodium silicate (Na2SiO3) at various solution ratios of 1.0:1.0, 1.0:1.2, 1.0:1.5, 1.0:2.0, 1.2:1.0, 1.5:1.0 and 2.0:1.0. (3) Results: The optimum temperature for treating metakaolin is established at 1000 °C, with a mixing ratio between the metakaolin powder and the geopolymer solution of 1.0:1.0, as well as a solution ratio between NaOH and Na2SiO3 of 2.0:1.0. (4) Conclusions: The use of piezoelectric bender elements to determine the initial and final setting times of metakaolin geopolymer pastes is a useful method by which to detect geopolymerization by shear wave velocity in a real-time manner. Moreover, the penetration of the Vicat apparatus can confirm the setting times at specific intervals. The relationships between the shear wave velocity and the Vicat penetration appear to be linear, with an initial setting time of 168 m/s and a final setting time of 187 m/s. Finally, the optimum metakaolin geopolymer pastes are applied to improve laterite soils, as measured by CBR tests