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濕排粉煤灰對混凝土性能的影響

發布時間: 2012-09-15 11:11 查看: 2218次

粉煤灰濕排混凝土
摘要：

通過實驗室模擬研究不同濕法存放時間(1～60個月)的2種低鈣粉煤灰的形貌、粒徑和用于混凝土摻合料的性能變化.粉煤灰濕排后顆粒變粗,顆粒表面出現侵蝕,但顆粒形貌基本保持不變;濕排粉煤灰礦物減水效應明顯降低,摻量為20%～40%的濕排粉煤灰混凝土坍落度比原狀粉煤灰混凝土減少約20～40 mm;摻加濕排粉煤灰的混凝土與外加劑適應性、抗滲和抗碳化無明顯變化,坍落度經時損失有所降低;濕法存放3個月的粉煤灰摻量20%時混凝土28 d和56 d抗壓強度比原狀粉煤灰混凝土分別下降5.8%和3.7%,但摻量為20%的濕法存放36個月粉煤灰混凝土抗壓強度比仍可以達到85%,濕法存放時間為3 a和5 a的粉煤灰混凝土強度無明顯差別.研究結果表明,濕排低鈣粉煤灰可以用作為混凝土摻合料.

Abstract：

Two types of wetting low-calcium fly ash were made for studying the performance under different storage time (1 to 60 months). The surface morphology, granule size distribution of the wetting fly ashes and their properties as supplementary cementitious materials in concrete were investigated. Although the granule size increased and there appeared considerable erosion on the surface, the surface morphology of wetting fly ash kept mostly unchangeable. The water reducing effect resulted from mineral properties of fly ash decreased much due to wetting. Compared with a parallel concrete with dry fly ash, slump of concretes with fly ash of 20～40% wetting for 3 months decreased by 20～40 mm while bleeding and permeability and carbonation had no change. The compressive strength of concrete in 28 day and 60 days with fly ash of 30% wetting for 3 months decreased by 5. 8% and 3. 7% respectively. However, the specific compressive strength of concrete in 56 days with fly ash of 20% wetting for 36 months still reached at 85% and there was no visible strength discrepancy of fly ash concrete wetting for 3 and 5 years. It was concluded that a wetting low-calcium fly ash could be used as supplementary cementitious material in some important concretes

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