Effects of Mineral Admixture and Steam Curing on the Thermal Conductivity of Mortar with Various Compositions

• Main Authors: Sue-Hao Ou, 歐書豪
• Other Authors: Ta-Peng Chang
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/16370661525244943704

碩士 === 國立臺灣科技大學 === 營建工程系 === 91 === This research used the Hot Wire Method by inserting a thermal needle probe in a drilled hole to study the effects of mineral admixture and steam curing on the thermal conductivity of mortar with various compositions. The effect of moisture content of fine aggregate on its thermal conductivity was studied first. Subsequently, under a constant water-to-cement ratio (w/c = 0.42), various sets of mortar were made with different sand-to-cement ratios by weight (s/c = 0.75, 1.75 and 2.75); and then under a constant sand-to-cement ratio (s/c = 1.75), mortars with two types of water-to-cement ratio (w/c = 0.34 and 0.5) were also produced. To study the effects of pozzolanic materials, mortars with 20% and 40% by weight of cement replaced by fly ash and slug, respectively, were fabricated. Finally, a steam curing of 50℃ and 70℃ for pure mortars and mortars with 20% and 40% by weight of cement replaced by fly ash and slug , respectively, were also conducted to study its effects on the thermal conductivity of mortar. Experimental results show that: (1) the higher the moisture content of fine aggregate is, the higher its thermal conductivity will be; (2) the mortar with a higher content of fine aggregate does not necessarily yield a higher thermal conductivity mortar. The mortar with higher content of fine aggregate reduces its amount of cement past and consequently lowers its thermal conductivity; (3) the mortar with a lower water-to-cement ratio has a higher thermal conductivity than that with a higher water-to-cement ratio, e.g., the thermal conductivity of mortar with a water-to-cement ratio of 0.34 was 2.079 W/m℃, about 31.22% higher than 1.5840 W/m℃for a mortar with a water-to-cement ratio of 0.5; (4) adding fly ash or slug into mortar will increase the thermal conductivity at age of 28 days; however, the quantity must be adequate, e.g., the test results indicate that a 20% replacement is more favorable than 40%; (5) high temperature increases the speed of hydration, but decreases the thermal conductivity of mortar also at age of 28 days. Adding fly ash or slug into mortar helps minimize the porosity and crack causing by high hydration rate and high temperature. For such case, the thermal conductivity will increase as well.