Abstract
In this study, an engineering characteristic test was conducted on cement milk using expansive additives during the construction of bored piles. Expansive additive mixtures with various mixing ratios were prepared according to the construction standards of the Korea Expressway Corporation. Segregation resistance, compressive strength, frictional resistance stress, scanning electron microscope images, porosity, and economic feasibility were analyzed. It was found that segregation effects due to expansive additive incorporation were insignificant, and it was confirmed that all specimens exceeded 0.5 N/mm2, the compressive strength standard of the Korea Expressway Corporation pile bearing capacity. Given a water–binder ratio of 83% mixed with 10% expansive additives, frictional resistance increased up to ~35%, skin friction force was significantly improved, and a cost-saving effect of up to ~33.24% was achieved.
Highlights
As recent buildings have become larger and taller, pile foundations have seen wider use [1,2]
Test specimens were prepared according to each mixing ratio to evaluate the segregation resistance, compressive strength, frictional resistance stress, scanning electron microscope (SEM) images, porosity, and economic feasibility of the filling material for each bored pile
The specimen with 83% W/B and 0% expansive additives had 135 mL bleeding at 3 h, and the settlement amount was maintained until 28 days of age
Summary
As recent buildings have become larger and taller, pile foundations have seen wider use [1,2]. The driven pile method, a technology introduced earlier in history, inserts piles by applying percussion or vibration [3]. It is advantageous in terms of support and material economy, the method causes social problems due to severe noise and vibration [3,4,5]. The separated doughnut auger method (55.6%) and the special auger and injected precast pile method (36.8%) are mainly used [12] among the variations. General construction using the bored pile method involves drilling the ground 100 mm larger than the diameter of the precast pile. According to previous studies conducting static load tests, the share of a pile’s skin friction force in relation to its total bearing capacity accounts for 66–97% of the capacity, making skin friction force one of the important considerations in structural foundation design [13]
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