胶凝材料性质对干混砂浆抗压强度的影响研究

Influence of the properties of cementing materials on the unconfined compressive strengths of dry-mixed mortar

为了研究胶凝材料性质对干混砂浆抗压强度的影响规律,共制备了24组样品,其中3组样品的微观形貌和孔结构采用扫描电子显微镜和压汞测孔仪(Autopore IV 9500)等测试手段进行了分析。试验结果表明:无论胶凝材料是100%水泥、50%水泥+50%矿渣粉和50%水泥+50%粉煤灰,7 d和28 d砂浆抗压强度均随胶凝材料总量增加而明显提高,增加水泥掺量对砂浆早期强度有利;与以100%水泥为胶凝材料制备的砂浆相比,当每吨干混砂浆中胶凝材料总量分别为100、150、200、250 kg时,以50%水泥+50%矿渣粉为胶凝材料制备的砂浆的抗压强度分别提高47%、55%、10%和0,而以50%水泥+50%粉煤灰为胶凝材料制备的砂浆的抗压强度分别降低77%、66%、56%和44%。与15%水泥制备的砂浆28 d硬化体相比,7.5%水泥+7.5%矿渣制备的砂浆28 d硬化体中水化产物更多或更分散、基体与骨料结合更密实、总孔隙更低及孔径更细;7.5%水泥+7.5%粉煤灰制备的砂浆28 d硬化体中水化产物更少、基体更松散、总孔隙更高及孔径更大。

24 groups of samples were made so as to investigating the influence of the properties of cementing materials on the unconfined compressive strengths（UCS）of dry-mixed mortar.The morphology and pore structure of 3 groups of 24 samples were investigated by scanning electron microscope（SEM）and mercury intrusion porosimeter（Autopore IV 9500）（MIP）.The results showed that the 7 d and28 d UCS of hardened mortars increased with the increase of the total content of cementing materials no matter what cementing materials were 100% cement and 50% cement＋50% slag powder and 50% cement＋50% fly-ash,and the increase of cement content was in favour of early strength of hardened mortar.Comparing with the hardened mortar of 100% cement as cementing material,the 28 d UCS of the hardened mortar of 50% cement＋50% slag powder as cementing material respectively increased 47%,55%,10% and 0,while the 28 d UCS of the hardened mortar of 50% cement＋50% fly-ash as cementing material respectively decreased 77%,66%,56% and 44% when the total content of cementing material in per ton dry-mixed mortar respectively was 100、150、200、250 kg.Comparing with the 28 d hardened mortar with 15% cement,the hydration product was more or more dispersing,the bond between matrix and aggregate was thicker,the total porosity was lower,and pore size was finer in the 28 d hardened mortar with 7.5% cement＋7.5% slag powder,while the hydration product was fewer,the matrix was looser,the total porosity was higher,and pore size was bigger in the 28 d hardened mortar with 7.5% cement＋7.5% fly-ash.