高弯拉强度水泥混凝土早期干缩变形性能研究

Study on High Flexural Strength Concrete Early Shrinkage Deformation

主要研究了水泥用量、胶凝材料类型、引气量、砂率等因素对混凝土干缩变形的影响。混凝土试件尺寸采用100 mm×100 mm×515mm,试验在控温控湿箱内进行,通过控温控湿箱的自动调节功能,设定目标温度和湿度过程,湿度按要求自动调节,利用千分表观察试件干湿变形值。湿度变化过程如下:从当前湿度用30 min升到相对湿度99%,恒定180 min,读取初值;用30 min降低湿度到10%,恒定180 min,读取终值;再用30 min升高湿度到99%,恒定180 min,读取初值,如此进行3个循环。试验结果表明:随水泥用量的增加,混凝土早期干缩变形增大;单掺硅灰的混凝土早期干湿变形大,单掺粉煤灰和混掺硅灰与粉煤灰的混凝土差别不大;3 d龄期的混凝土含气量越大,干湿变形也越大;28 d龄期以后,在含气量小于6.8%的情况下,干湿变形随含气量的增加而减小,而当含气量达到10%,干湿变形又呈现增大的趋势。

Shrinkage deformation of concrete in early age, which mainly varies with factors such as cement quantity, bonder type, air content and sand aggregate ratio, is studied. Test species, which sizes are 100mm×100mm×515mm, are put into temperature and humidity controlled box, Value of shrinkage deformation under different humidity is recorded by micrometer gauge, Humidity will vary automatically with need in （20 ± 1 ）℃ temperature level in the box, Humidity increases from current value to 99 percent in 30 minutes. Initial value of shrinkage deformation should be achieved after 180 minutes with humidity of 99 percent. Then humidity decreases from 99 percent to 10 percent in 30 minutes. Value of shrinkage deformation should be achieved after 180 minutes with humidity of 10 percent. It will experience three loops around. It is shown that： （ 1 ） early age shrinkage deformation of cement concrete is enlarged with increasing cement quantity; （2） early age shrinkage deformation of high flexural strength concrete （HFSC） with pure silica is larger than those with fly ash and silica and those with pure fly ash, The late two are almost with the same shrinkage deformation; （3） early age shrinkage deformation of HSFC is enlarged with increasing air content at 3 days age; （4） After 28 days age, early age shrinkage deformation of HSFC is reduced with increasing air content when it is below 6.8 percent and it will enlarge with air content when above 10 percent.