修復用石灰純度檢測方法之研究

Research on a Purity Testing Method for Restoration Lime

本研究乃是考量我國在古蹟灰作修復時所用石灰的品質及耐久性，在施工前應對使用於古蹟灰作修復石灰的純度加以檢測，以使修復的灰作能有充分的品質保障。本研究所研發的石灰純度（CaO的含量）檢測方法有放熱溫度檢測法及體積回脹檢測法。放熱溫度檢測法主要是根據石灰中之CaO遇水產生Ca（OH）2時會釋放熱量，依待測石灰樣本加水時所釋放熱量的多寡比例來推估該樣本中含有CaO的比例。其次體積回脹檢測法是根據石灰中的CaO遇水產生Ca（OH）2時，亦會產生體積膨脹現象，本研究擬依據待測石灰樣本在加水時的體積膨脹量的大小來推定待測石灰樣本的CaO含量比例。試驗結果主要如下：一、市售之試藥級CaO、MgO純度並非如標示所示，可能因製造時間、存放環境等因素，產生水化、碳酸化反應，使其純度逐漸下降。二、CaO的各項特徵值與純度大致上成線性正比關係，相關係數皆在0.95以上，為高度正相關。三、使用最高溫度變化、最大膨脹率進行CaO純度估算，其整體誤差較低；使用溫度歷時關係圖曲線所包含之面積、膨脹率歷時關係圖曲線的斜率進行CaO純度估算，其整體誤差較高，推測是因面積及斜率的計算較為複雜所導致。四、以最高溫度變化之純度檢量線X＝1.425×Tc－0.332以及最大膨脹率之純度檢量線X＝0.821×Sc＋7.676，可對修復用石灰中之氧化鈣成份進行初步快速估算，作為檢驗石灰中純度之參考依據。

The purpose of this research is to develop tests to assess the purity, quality and durability of lime used in the restoration of historic sites in Taiwan. In order to avoid shortcomings in previous practices, the purity of the lime used for the restoration of historic sites should be tested before construction, so that the restoration lime can have sufficient quality assurance. Testing methods for lime purity(CaO content) developed by this research institute include exothermic the temperature measurement method and a volume expansion method. The exothermic temperature method is based on the heat released when the CaO in lime reacts with water to produce Ca(OH)2. The proportion of CaO contained in the sample is estimated based on the amount of heat released when adding water to the lime sample to be tested. Secondly, the volume expansion method is based on the fact that when CaO reacts with water to produce Ca(OH)2, there is an expansion in volume. This aims to estimate this volume expansion. Measure the proportion of CaO content in lime samples. The test results are mainly as follows: The purity of commercially available, reagent-grade CaO and MgO is not as indicated on the label. Due to factors such as manufacturing time and storage environment hydration and carbonation reactions may occur, and the purity of the product may gradually decrease. The eigenvalues of CaO are roughly linearly proportional to purity, and the correlation coefficients are all above 0.95, which is a highly positive correlation. Using the maximum temperature change, and maximum expansion rate, to estimate the purity of the CaO, the overall error is relatively low. However, using the area under the temperature change vs. elapsed time curve, and the slope of the expansion rate vs. elapsed time curve to estimate the purity of CaO, the overall error is relatively high, possibly because of the complicated calculations of area and slope. Using a purity calibration curve for the maximum temperature change X = 1.425 × Tc - 0.332 and the purity calibration curve of the maximum expansion rate X = 0.821 × Sc + 7.676, the CaO content in the restoration lime can be quickly estimated as a test for its purity compared to a lime reference.