การพัฒนากำลังอัดของมอร์ต้าร์ซีเมนต์ภายใต้การบ่มด้วยพลังงานไมโครเวฟ โดยใช้เตาชนิดสายพานลำเลียงแบบต่อเนื่อง

Abstract

       This paper presents a curing method of cement mortar with microwave energy by using a continuous belt furnace, which consists of magnetron to generate microwave in the frequency range of 2.45 ± 0.05 GHz and power limit of one magnetron equals 800 watts. There are 8 magnetrons distributive installed distributively both ends and inner wall of furnace. The oven was rectangular in shape with a size of 45 x 90 cm. and 270 cm. long. The velocity of belt can be adjusted from 0 to 0.40 m/s. The analyses emphasized on the heat and mass transfer in mortar during curing with microwave energy including early aged compressive strength of mortar comparing between mortars cured with microwave energy and water cured. The parametric variables were the ratios of fine aggregate (river sand)-to-Portland cement Type I (S/C) (2.0 and 2.75), water-to-cement ratio (W/C) based on water requirement for a constant flow of 110 ± 5 %, air content of 1 % by volume, and chemical admixture as a retarder. For microwave parameters, number of magnetron (as power transmitted) and time of microwave application were studied. The test properties were temperature rise, moisture content, and compressive strength development. From the test results, it was found that the application of microwave at power of 800 watts for 30 minutes can accelerate the early compressive strength of mortar without affecting the compressive strength of mortar at the age of 28 days, whereas the microwave at power of 2400 watts leads to a decrease in the early and long-term compressive strength due to over heating until micro-cracking in mortar took place.