基于RSM-BBD的高原地区桥墩混凝土性能试验研究

Experimental Study on Performance of Bridge Pier Concrete in Plateau Area Based on RSM-BBD

针对高原地区桥墩混凝土服役环境的特点,探究矿物掺合料对桥墩混凝土性能的影响效果。采用Box-Behnken Design响应面法(RSM-BBD)设计了15组试验,详细研究了粉煤灰、矿渣和硅灰掺量对混凝土强度和冻融性能的影响规律。以28 d抗压强度、200次冻融循环后混凝土质量损失率和相对动弹性模量为响应值构建响应面模型,旨在揭示响应参数和目标响应值的相关关系及多目标响应值条件下桥墩混凝土的合理配合比。结果表明,与基准组混凝土相比,适量的矿物掺合料有利于提高混凝土强度,增强混凝土的耐低温冻融性能。混凝土的强度和抗冻融性能主要受单因素的影响,其中矿渣和硅灰能提高混凝土的抗压强度,粉煤灰和硅灰则可以提高混凝土的抗冻融性能。各因素的交互作用对混凝土各性能有不同程度的影响,其中矿渣和硅灰掺量的交互作用对28 d抗压强度影响显著,粉煤灰与硅灰掺量的交互作用对质量损失率影响显著,粉煤灰与矿渣掺量的交互作用对相对动弹性模量影响显著。基于目标响应值和响应优化,本试验条件下矿物掺合料的合理配合比为粉煤灰、矿渣和硅灰掺量分别为20%、15%和10%(质量分数)。

According to the service environment characteristics of bridge pier concrete in plateau area,the effect of mineral admixture on concrete performance was investigated.The Box-Behnken Design response surface method(RSM-BBD)was used to design 15 groups of tests,and the effects of fly ash,slag and silica fume content on the strength and freeze-thaw properties of concrete were studied in detail.The response surface model was built with 28 d compressive strength,mass loss rate and relative dynamic elastic modulus of concrete after 200 times freeze-thaw cycles as response values to reveal the correlation between response parameters with target response values,and the optimal ratio of bridge pier concrete under multi-target response values.The results show that,compared with the concrete of reference group,the appropriate mineral admixture is beneficial to improve the strength and enhance the freeze-thaw resistance of concrete at low temperature.The strength and freeze-thaw resistance of concrete are mainly affected by a single factor,among which slag and silica fume can improve the compressive strength,while fly ash and silica fume can enhance the freeze-thaw resistance of concrete.The interaction of various factors has different degrees of influence on the performance of concrete.The interaction between slag and silica fume content has a significant effect on 28 d compressive strength.The interaction between fly ash and silica fume content has a significant effect on mass loss rate.The interaction between fly ash and slag content has a significant effect on relative dynamic elastic modulus.Based on target response values and response optimization,the reasonable ratio of mineral admixtures under the experimental conditions is 20%,15%and 10%(mass fraction)of fly ash,slag and silica fume,respectively.