Unconfined compressive strength assessment of soil-cement mixtures in Hai Duong city

The unconfined compressive strength (qu) of the soil-cement mixture (S-CM) depends on many factors, in which the soil type and the cement content (%CM) are very important factors. The soil type determines the fine particle content and affects the effectiveness of soil-cement mixture. Meanwhile, %CM has a direct influence on the qu of the S-CM. The cost of foundation treatment methods for small and medium-sized constructions depends on the reasonable cement content. This paper presents the unconfined compressive strength of S-CM for five common cohesive soils in Hai Duong city (soft clay, soft clayey sand, soft sandy clay, clayey sand mud, and sandy clay mud) with four cement contents (7%, 10%, 15%, and 20%). The research results show that the clayey sand (mbQ21-2hh) has the highest improvement efficiency compared to other soils, i.e., soft sandy clay (abQ23tb), soft clay (mQ21-2hh), sandy clay mud (mbQ21-2hh), and clayey sand mud (amQ21-2hh). The clay content has a great influence on the qu of S-CM. With the required value of qu28 = (8.0÷10.0) kG/cm2 (at 28 curing days), the reasonable cement content (% CM) is varied from 8% to 13% for soft sandy clay (abQ23tb), soft clay (mQ21-2hh), sandy clay mud (mbQ21-2hh), and clayey sand mud (amQ21-2hh); with the same value of qu28, the reasonable %CM is from 7.5 to 9.0% for clayey sand (mbQ21-2hh). The results are the scientific basis for recommending a reasonable %CM for each type of soil when designing to reinforce the foundation with soil-cement columns in Hai Duong city.