PERFORMANCE EVALUATION AND ANALYTICAL STUDY ON THE EFFECT OF NANO-SILICA ADDITION IN ENHANCING DURABILITY CHARACTERISTICS OF CONCRETE

This research evaluates the sorptivity, water absorption, and acid resistance of M70 grade concrete with the incorporation of nano silica. The normal M70 concrete was prepared using 10% of silica fume and 11% of fly ash as partial substitutes for cement to act as a robust reference mix. For enhanced durability, nano silica was incorporated as an additional partial substitute. Concrete cubes were cast, water-cured for 28 days, and subjected to 5% sulfuric acid (H₂SO₄) and 5% hydrochloric acid (HCl) for 30 and 90 days to assess acid resistance. To check permeability and improvement in pore structure, water absorption and sorptivity tests were also conducted following established procedures. The results indicated that, when compared to the normal mix, microsilica concrete exhibited less degradation. The weight loss in nano silica concrete following exposure to acid for 90 days was 2.12% in HCl and 2.95% in H₂SO₄, whereas the normal mix lost 4.51% and 5.75% of their weights, respectively. For nano silica concrete, the residual compressive strength was 93% of the original strength, while the normal mix had 86%. The percentage of water absorption in nano silica concrete reduced from 2.45% for the normal mix to 1.65%. Even the capillary suction and permeability decreased significantly, as noted from the sorptivity reduced from 2.13 mm to 1.39 mm. Based on the conclusions drawn from the research, incorporation of nanosilica in M70 grade concrete reduces sorptivity, reduces water absorption, and enhances acid resistance all factors that contribute to the overall durability and service life of high-strength concrete.本研究针对掺加纳米二氧化硅（nano silica）的M70等级混凝土的吸渗性、吸水率与耐酸性展开系统性评估。以10%硅灰（silica fume）与11%粉煤灰（fly ash）部分替代水泥制备基准M70混凝土，作为性能优异的对照配合比。为进一步提升混凝土耐久性，本次研究额外掺入纳米二氧化硅作为水泥的部分替代材料。成型混凝土立方体试块，经28天水中养护后，将试块分别置于5%硫酸（H₂SO₄）与5%盐酸（HCl）溶液中浸泡30天与90天，以评估其耐酸性。同时按照既定试验规程开展吸水率与吸渗性测试，以表征混凝土的渗透性及孔隙结构改善情况。研究结果表明，相较于基准配合比混凝土，硅灰混凝土的劣化程度更低。纳米二氧化硅混凝土经90天酸侵蚀后的重量损失在盐酸溶液中为2.12%，在硫酸溶液中为2.95%；而基准配合比混凝土的重量损失分别为4.51%与5.75%。纳米二氧化硅混凝土的剩余抗压强度为初始强度的93%，基准配合比混凝土则为86%。纳米二氧化硅混凝土的吸水率从基准配合比的2.45%降至1.65%。其毛细吸渗性能与渗透性亦显著降低，吸渗系数从2.13 mm降至1.39 mm。基于本研究得出的结论，在M70等级混凝土中掺入纳米二氧化硅可降低其吸渗性与吸水率，并提升耐酸性，上述效应均可提升高强混凝土的整体耐久性与服役寿命。