流态粉煤灰路基填料配合比设计及路用性能试验研究

Experimental Study on Mix Design and Road Performance of Fluid Fly Ash Subgrade Filler

为解决高速公路桥涵台背段路基工作面狭小而导致的压实质量无法保证等问题,兼顾环保的要求,开展了无需振捣、可自密实、容重低、价格低廉的流态粉煤灰路基填料配合比设计,进行了各项路用性能影响因素分析及性能评价。采用低标号水泥、低等级粉煤灰及聚羧酸高性能减水剂配制了流态粉煤灰,以获得高性价比并满足路用性能的配合比。基于流态粉煤灰的流动度、抗压强度、泌水率及密度确定了其初始配合比,并与使用高标号水泥的流态粉煤灰相关指标进行了对比。然后对该配合比下填料的其他路用性能及其影响因素开展了试验研究,并进行了参数敏感度分析。结果表明:采用F类Ⅲ级粉煤灰及PSA325水泥配制的流态粉煤灰的各项物理力学性能均满足工程要求;用水量对流态粉煤灰流动度、抗压强度及泌水率均有较大影响,随着用水的量增加,泌水率和流动度均不断增大,但抗压强度则减小;用水量对上述4个指标中泌水率的影响最为显著,随着外加剂掺量的增多,填料流动度、抗压强度及泌水率均增高,冻融循环系数减小;外加剂掺量为1%时,流态粉煤灰的水稳定性最佳,最终得出的满足施工及路用性能的流态粉煤灰最佳配合比为:水泥与粉煤灰质量比为10∶90,用水量为70%,外加剂掺量为1%。

In order to solve the problem that the compaction quality cannot be guaranteed due to the small working surface of the subgrade at bridge and culvert abutments of expressway and consider the requirements of environmental protection,the mix design of fluid fly ash subgrade filler that without vibrating,can self compact,have low bulk density and are cost-effective is carried out,the analysis of the factors affecting the road performance and the evaluation of the road performance are also carried out.The fluid fly ash is prepared by using low grade cement,low grade fly ash and polycarboxylic acid high-performance water reducing agent to obtain the high performance/cost ratio and the mix proportion that meet road performance requirements.The initial mix proportion is determined based on the flowability,compressive strength,bleeding rate and density of fluidized fly ash,and compared with the relevant indicators of fluid fly ash that using high-grade cement.Then,the experimental study is on the other road performance and influencing factors of the filler with this mix proportion is conducted,and the parameter sensitivity analysis is conducted as well.The result shows that(1)The physical and mechanical properties of the fluid fly ash prepared by class F grade III fly ash and PSA325 cement meet the engineering requirements.(2)The water consumption has great influence on the flowability,compressive strength and bleeding rate of fluid fly ash.As the water consumption increases,the bleeding rate and flowability continue to increase,but the compressive strength decreases.(3)The water consumption has the most significant influence on the bleeding rate among the abovementioned 4 indicators.As the dosage of additives increases,the fluidity,compressive strength and bleeding rate of the filler all increase,while the freeze-thaw cycle coefficient decreases.(4)When the admixture dosage is 1%,the water stability of fluid fly ash is the best.The optimal ratio of fluid fly ash that meets the construction and road performance is determined as follows:mass ratio of cement to fly ash is 10∶90,water consumption is 70%,and the additive dosage is 1%.