In this experimental study, the characteristic of damages on GFRP rebar exposed to high temperature only and immerged in alkaline solution after the exposure to high temperature was analyzed through microscopic image analysis. The found microcrack and pores in resin matrix were quantitatively compared if there was effect of pre-exposure to high temperature. The damages, such as microcrack and pores in resin matrix, by alkali exposure were mainly found in rebar surface. On the other hand, the pores caused by high temperatures were extensively found in a section and had greater width than those caused by the alkali exposure. In results of the quantitative comparison, the accumulated length and widths of microcrack and pores in resin matrix in pre-exposed GFRP rebar to high temperature were respectively 1.5 and 1.4 times of those in the GFRP rebar only immerged in alkali solution. Therefore, the deterioration of resin matrix by the alkali exposure could be accelerated due to the pre-exposure to high temperature.

Accelerated alkali resistance test were conducted for pre-heated GFRP Rebar. The GFRP rebar specimens were heated to temperatures of 60℃, 120℃, 200℃ and 300℃ and then immerged in alkali solution for 30days. According to ACI 440.3R-12, tensile properties were measured.

In this paper, evaluation of compressive strength development of concrete cured by microwave heating system is introduced. For this evaluation, core strength tests were conducted. Test results show that the development was accelerated by microwave heating system. And two parameters in a equation for predicting initial strength development were presented when using this system.

Carrots (Daucus carota L.) are consumed as an important dietary source of provitamin A including β-carotene, α-carotene and lutein. An HPLC method was applied to determine the content of the carotenoid composition in carrot cutivars cultivated in Korea. HPLC analyses were carried out with five carrot cultivars (Socheon-5-chon, Hongsim-5-chon, Myeongju-5-chon, Seonhongbom-5-chon and Betarich) sown at April, 2007 and six cultivars (Yeoreum-5-chon, Hanyeoreum-5-chon, Sinheukjeon-5-chon, Bibariheukjeon, Manina and Betarich) sown at August of the same year. In general, the former varieties are not used for the sowing at summer because of their bolting (growth of floral axis). The former and the latter carrots were harvested after 110 and 96 days from seeding, respectively, and the carotenoids were extracted with acetone after freeze-drying. The amount of α-carotene (117.7∼205.3 μg/g・DW) was similar to that of β-carotene (113.1∼189.6 μg/g・ DW) for the carrot cultivars sown at spring, while the content (46.2∼71.1 μg/g・DW) was about a half of β-carotene content (92.5∼140.2 μg/g・DW) for the latter cultivars. In addition, the average content of lutein (25.2 μg/g・DW) in the former cultivars was eight times higher than that in the latter cultivars (3.1 μg/g・DW). Among the spring cultivation types, Socheon-5-chon and Myeongju-5-chon showed higher amount of α-carotene and β-carotene, while the higher amount was determined in Yeoreum-5-chon and Sinheukjeon-5-chon among the autumn cultivation types. Validation of the HPLC-DAD method showed good linearity (r2 > 0.997) of the three compounds analyzed in a wide concentration range (0.025∼20 μg/ml). The R.S.D. values for intra-day and inter-day precision were less than 19.2% and the mean recovery of each compound was 85.4∼104.7%.