Study on the influence of solid waste fly ash on mechanical properties of cement mixing piles

Abstract

In order to solve the problems of low bearing capacity, high water content and high alkali content of saturated muddy soft soil foundation, and reasonably realize the recycling of resources and solid waste treatment, taking the soft soil foundation reinforcement project of Xiaohudao Lizhu Sluice Pump Project in Nansha District of Guangzhou as an example, fly ash and cement were used as cementitious materials to make slurry, and the influence law of compressive strength of fly ash cement mixing piles with different proportions was studied. The result show that when the water-cement ratio increases from 0.45 to 0.55,the unconfined compressive strength of the specimen increases, but when the water-cement ratio increases to 0.65,the unconfined compressive strength of the specimen decreases, and the decrease rate is less than the increase rate. When the water-cement ratio is 0.55,the compressive strength of the specimen is the largest. The unconfined compressive strength of the specimens with 20% fly ash incorporation is larger under different water-cement ratios and ages. The core section of the field test pile with 20% fly ash incorporation is relatively uniform as a whole;the compressive strength of the core sample increases first and then decreases with the increase of the sampling depth. The compressive strength of the core sample of the test pile increases by 10.74%,4.23% and 10.34% respectively in the depth of 5.0~8.4 m compared with the depth of 1.05~2.75 m, and decreases by 2.99%,3.38% and 4.69% respectively in the depth of 10.0~12.4 m compared with the depth of 5.0~8.4 m. The cement fly ash mixing pile improves the foundation bearing capacity of silty clay and muddy soil. The chemical reaction between fly ash and cement soil produces hydration products C—S—H gel and ettringite( AFt). The structure is dense, and the bonding force formed improves the mechanical strength of cement soil.

Keywords

fly ash / cement mixing pile / pile test / soft soil foundation