THE SULFURIC ACID RESISTANCE OF CONCRETE WITH BLAST FURNACE SLAG

The deterioration of concrete by sulfuric acid attack in sewage environments has become a serious problem. In this study, it was shown that the resistance to sulfuric acid of mortar and concrete can be improved by using a blast-furnace slag fine aggregate to the total amount of fine aggregate. When mortar or concrete reacts to sulfuric acid, dihydrated gypsum film is formed around the particulate of the fine aggregate. This dihydrated gypsum film could retard the penetration of sulfuric acid, thus improving the resistance to sulfuric acid. However, the resistance to sulfuric acid depends on the hardness of the dihydrated gypsum film

Strength and Durability of Concrete with Blast Furnace Slag

The properties of concrete using blast furnace as binder and fine aggregate have been investigated in this study. The experiments focus on the properties of concrete such as compressive strength and young's modulus, carbonation, diffusion of chloride ions, resistance to sulfate attack and resistance to freeze and thaw. The experimental results show that when blast furnace slag is used in concrete, it improves the durability properties of concrete. However, the combination of using both blast furnace slag as binder and fine aggregate shows a greater improvement of those properties of concrete

Effect of Blast Furnace Slag Sand to Durability of Concrete

本研究は，高炉スラグを用いたコンクリートの中性化，耐硫酸塩性および凍結融解 抵抗性の検討を行ったものである．高炉スラグを細骨材に用いることで，細骨材周辺に集 積する水酸化カルシウムがなくなり，骨材表面とペーストとの界面が強固なものとなるた め，コンクリートの中性化および耐硫酸塩性が向上する．また，結合材の一部を高炉スラ グ微粉末に置き換えるか，または，細骨材に高炉スラグ細骨材を用いたコンクリートでは， AE 剤を用いることなく，また，蒸気養生を行っても，十分な凍結融解抵抗性が得られる

Association between Household Exposure to Secondhand Smoke and Dental Caries among Japanese Young Adults: A Cross-Sectional Study

The long-term effects of secondhand smoke (SHS) on dental caries among Japanese young adults remain unclear. The purpose of this cross-sectional study was to evaluate whether household exposure to SHS is associated with dental caries in permanent dentition among Japanese young adults. The study sample included 1905 first-year university students (age range: 18-19 years) who answered a questionnaire and participated in oral examinations. The degree of household exposure to SHS was categorized into four levels according to the SHS duration: no experience (-), past, current SHS = 10 years. Dental caries are expressed as the total number of decayed, missing, and filled teeth (DMFT) score. The relationships between SHS and dental caries were determined by logistic regression analysis. DMFT scores (median (25th percentile, 75th percentile)) were significantly higher in the current SHS >= 10 years (median: 1.0 (0.0, 3.0)) than in the SHS-(median: 0.0 (0.0, 2.0)); p = 0.001). DMFT >= 1 was significantly associated with SHS >= 10 years (adjusted odds ratio: 1.50, 95% confidence interval: 1.20-1.87, p = 10 years) was associated with dental caries in permanent dentition among Japanese young adults

The level of salivary lactate dehydrogenase as an indicator of the association between gingivitis and related factors in Japanese university students

The aim of this study was to investigate the association between the presence of gingivitis estimated using the salivary level of lactate dehydrogenase (LD) and related factors in young Japanese adults. Data from 1,915 participants (21.4 ± 2.5 years) were analyzed. Unstimulated saliva was collected from each participant and the salivary LD level was evaluated using a commercially available test kit with an integer scale ranging from 1 to 10. Gingivitis was defined as the LD level of ≥8. The number of permanent teeth, the simplified oral hygiene index (OHI-S), the presence of partially erupted molars and body mass index were recorded. Additionally, participants answered a questionnaire. The percentage of male participants, the number of permanent teeth, the OHI-S and the presence of partially erupted molars were higher, whereas the proportion receiving dental check-ups was lower in the gingivitis group (n = 88, 4.6%) than in the healthy group. Logistic regression analysis showed that gingivitis was significantly associated with OHI-S (OR: 2.68, 95% CI: 1.94-3.69) and receiving dental checkups (OR: 0.31, 95% CI: 0.10-0.99). The present findings indicated that the OHI-S and receiving dental checkups were significantly associated with gingivitis, as assessed by the salivary LD level, in this cohort