掺无机纳米矿粉水泥复合净浆的化学收缩与自收缩

Chemical and Autogenous Shrinkages of Cement-based Composite Paste with the Addition of Inorganic Nano-powders

依据ASTM试验标准,改良其试验方法,测量水泥复合净浆化学收缩与自收缩,研究单掺不同粒度无定型纳米二氧化硅、亲水型和表面预湿型纳米碳酸钙、不同晶型和粒度纳米二氧化钛三种无机纳米矿粉对其早期收缩的影响。研究表明：一定掺量范围内,无机纳米矿粉的掺入显著提高复合净浆化学收缩与自收缩,且随龄期增长,差异渐大,其中尤以掺纳米二氧化硅最甚,且纳米粒度越小,早期收缩越大。与不亲水但表面预湿型纳米碳酸钙相比,同掺量条件下掺亲水型纳米碳酸钙的净浆早期收缩更大。纳米氧化钛掺量3.0%~5.0%,净浆化学收缩最大,自收缩值增幅不大,远远低于掺纳米二氧化硅和掺碳酸钙的。无机纳米矿粉对水泥基材料早期收缩行为的影响与所掺纳米矿粉种类、晶型、颗粒尺度、表面状态以及掺量等密切相关。

Based on ASTM standards and modified test method, the chemical and autogenous shrinkages of cement composite paste were measured to investigate the influences of single addition of one of three inorganic nano- powder, such as amorphous nano- Si0 2 with different particle sizes, hydrophilic or surface prewetted nano-CaC0 3, or nano- Ti0 2 with various crystal forms and particle sizes on the early-age shrinkage of paste. Results show that within a certain mass proportion, the addition of inorganic nano-powder obviously increases both chemical and autogenous shrinkages of composite paste, and with time passing,the increments become more evident. The addition of nano- SiO2 exerts the most effect, especially using the smaller nano- particle. Compared to the hydrophilic or surface prewetted nano-CaCO3, the hydrophilic one leads to higher early-age shrinkage of paste under the condition of the same mass proportion. With 3.0%-5.0% of nano- TiO2 admixed, though the highest chemical shrinkage of paste is observed, there is no remarked growth for autogenous shrinkage, much less than that added with nano- SiO2 or nano-CaCO3. It can be concluded that the influence of inorganic nano-powder on the early-age shrinkage behavior of composite paste depends on the type, crystal form, particle size, surface status and mass proportion of the added inorganic nano- powder.