本研究製作W/B=0.6 及不同爐石取代水泥量(10％, 30％, 40％, 60％, 80％)之圓柱混凝土，試體分別受高溫(200°C, 400°C, 600°C, 800°C)作用後，探討其工程性質(容積密度、超音波速、動態彈性模數、動態剪力模數、卜松比、熱傳導係數、抗壓強度)試驗，同時，利用數值模擬分析方式，探討敲擊回音頻率分析、表面波譜分析(SASW)及多頻道表面波分析(MASW)等三種方式對於評估高溫後層狀結構物損傷程度之適用性。
研究結果顯示：(1) 當混凝土中爐石取代水泥量為30%時，在常溫狀態下抗壓強度為33.78 MPa，高於控制組約5.40%；但在800 °C之後，其抗壓強度為4.14 MPa，高於控制組約20.35%，顯示適當的爐石取代量不僅不會減少其抗壓強度，在高溫後，更有較高的抵抗能力。(2) 利用非破壞檢測方式(超音波試驗、動態共振試驗、熱傳導試驗)所獲得混凝土工程性質，隨高溫之變化與抗壓強度隨溫度之變化有正比趨勢，因此利用非破壞試驗不僅可評估高溫後混凝土之強度，更可獲得其高溫後混凝土相關之工程性質。(3) 混凝土樑受高溫作用後，其結構內部超音波速隨著深度而增加，亦即是樑結構物呈現漸層的變化，因此可將高溫後混凝土樑視作一層狀結構物，此外，由於混凝土之熱傳導係數隨溫度增加而減少，因此高溫後混凝土樑承受高溫之損傷程度將比未損傷程度來得小。(4) 利用數值模擬探討三種非破壞檢測方式對於檢測雙層混凝土版損傷程度之適用性研究中，結果顯示:利用敲擊回音之頻率分析方式雖可測得損傷及未損傷之程度(深度)，但卻無法反應出高溫後混凝土強度之漸層變化，因此若以SASW方法量測高溫後混凝土之損傷程度，便可呈現波速隨結構深度之變化，繼而利用MASW方法檢測之，不僅節省量測及分析時間，更可獲得較高品質之頻散曲線。

In this study, various concrete cylindrical specimens with water-to-binder equal to 0.6 by different replacement content of cement with slag (0%, 10%, 30%, 60%, 80%) are mixed and exposed to specific elevated temperatures (200oC, 400oC, 600oC, 800oC ) in the furnace, respectively The engineering properties of specimens, such as bulk density (ρ), ultrasonic pulse velocity (UPV), dynamic modulus of elasticity (Ed), dynamic shear modulus (Gd), Poisson’s ratio (ν), thermal conductivity (λ) and compressive strength ( ) of specimens are tested after exposure to specific elevated temperatures. In the meantime, it also discusses the feasibility assessment that estimate the damage degree of concrete slab exposed to elevated temperature by using several numerical estimation methods such as impact-echo (IE) frequency analysis, spectral analysis of surface waves (SASW), and multi-channel analysis of surface waves (MASW).
The results show as follows: (1) At room temperature, the compressive strength of replacement of cement with slag 30% is 33.78 MPa, it’s about 5.40% higher than mixture normal concrete (NC); at temperature of 800oC, the compressive strength is 4.14 MPa, it’s about 20.35% higher than NC. It indicates concrete adding with the appropriate slag replacements not only improves compressive strength but also has higher resistance at elevated temperature. (2) The engineering properties of concrete with temperature have the same trend with the compressive strength of concrete. Thus, the non-destructive testing (NDT) can not only estimate the strength of concrete but also obtain engineering properties of concrete exposed to elevated temperature. (3) The UPV of concrete beam specimens exposed to one-sided heating increases gradually with depth, so the specimen can be regarded as a graded layered structure. In addition, the reduction rate of thermal conductivity decreases with temperature such that the damage range of exposed to higher temperatures is smaller than that for lower temperatures. (4) The IE frequency analysis, SASW, and MASW methods are used to analyze on two-layered slabs. From comparing these results, although the frequency analysis can clearly identify the thickness of two layers in a slab, but it cannot accurately predict variations of P-wave velocity with depth. Consequently, measuring damage degree of concrete exposed to elevated temperature by SASW method can present the variation of p-wave velocity with depth. The MASW not only reduces measurement and analysis times but also obtains higher quality dispersive curve.

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