Experimental Study of the Precracking

Abstract

Pre-cracking technique allows obtaining a controlled cracking, finer and less evolutive. The idea in reconsidering the design of precracked foundations has grown up with this technique. Studies are being developed, mainly in the field of structural analysis based on finite element methods.

Up today, a reduction in thickness compared to pre-cracked foundation thicknesses obtained without pre-cracking is not allowed and must be considered as experimental.

Tests have been conducted on precracked test boards with and without impregnation layer of cement treated base and construction on site. The execution of the microcrack has been performed three days after the start of implementation (from 48 to 72 hours after the execution of the cement treated base). It was conducted by applying 2 passes with vibration and without vibration; after that the state of microcracking has been confirmed.

Microcracking did not occur without vibration and six samples were collected each time (24 and 25 days after execution) for each of the three modes 0, 2 and 4 passes of vibrating compactors.

To confirm the reduction in strength due to microcracking observed on these samples, compression and indirect tensile tests were carried out 28 days after execution.

The results obtained show that, after inclusion of the microcrack, there is no much influence on the compressive strength of cemented treated base. Accordingly, we may consider that the inclusion of the microcrack does not affect the performance of the cemented gravel.