Impact of weathering on a cement-treated sand

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After their construction, geotechnical structures built with treated soils are subjected to weathering that can alter the effects of the treatment by degrading the cementitious bonds. Durability of treated soils needs to be considered in the design process of these structures. This study focuses on the quantification of the impact of hydric cycles on the mechanical behavior of cement-treated soils.

A class S1 sand treated with 1%, 2% and 4% cement was used. Two types of hydric cycles were performed: type I are derived from ASTM-D559 (16h of oven drying and 8h of immersion) and type II consist in 48h of immersion and then imposing suction by controlling relative humidity at 50% during 120h. Triaxial CD tests were performed after several cycles (up to 9). Stress-dilatancy approach based on Rowes theory was used to quantify the contribution of bonding on the mechanical behaviour by introducing a bond ratio, nbond.

The results showed that the main effect of the wetting/drying cycles is to alter the bonds, and consequently diminish the mechanical performance. The alteration depends on the intensity of the cycles. Indeed, the type I cycles, which are more aggressive, lead to a greater degradation than the type II-cycles. For instance, for 4% cement-treated samples, after 9 type-I cycles, the maximum deviator stress is 1160 kPa whereas it values 1380 kPa after 9 type-II cycles. The degradation rate of the performance is also a function of the cement content. For the samples treated with 2 or 4% cement, most of the degradation occurred during the very first cycles whereas the degradation was more progressive with a cement content of 1%. The evaluation of the bonding ratio permitted to quantitively assess the treatment effect and the weathering progress with cycles. The extent of the degradation also appeared to be function of the type of wetting and drying cycle.

These results show the impact of the intensity and the number of hydric cycles on the degradation of the treated soils mechanical performance considering the degree of cementation. It also highlights that the protocol of imposition of the cycles is essential to better represent on-site conditions.

8th International Symposium on Deformation Characteristics of Geomaterials (ISDCG2023)

II.6) Soil stabilisation and improvement