New design chart for geotechnical ground improvement: characterizing cement-stabilized sand

Abstract

Cement stabilization of soil is a useful method to improve the mechanical behaviors and engineering performance of soils in geotechnical design and construction projects involving weak or liquefiable soils. Among the factors affecting the strength of cement-stabilized soils, water content and water–cement ratio are important but less well understood because of controversial views. This paper presents a systematic laboratory study to investigate the effects of water content and water–cement ratio on the unconfined compressive strength, with good control of the packing density and void ratio of the tested specimens. The effects of void ratio and cement content are also investigated. The strength of the cement-stabilized sand continuously decreased with increasing water–cement ratio within the range of 0.5 to about 3. A general equation is suggested to evaluate the unconfined compressive strength of cement-stabilized soil. Finally, a new conceptual characterization chart is proposed with consideration of the effects of cement content, water content, and water–cement ratio.

Appendix

According to the definition given by Consoli et al. [6], it is straightforward to have the following equation:

$${n \mathord{\left/ {\vphantom {n {C_{\text{vi}} }}} \right. \kern-0pt} {C_{\text{vi}} }} = \frac{{{{V_{\text{void}} } \mathord{\left/ {\vphantom {{V_{\text{void}} } {V_{\text{total}} }}} \right. \kern-0pt} {V_{\text{total}} }}}}{{{{V_{\text{cement}} } \mathord{\left/ {\vphantom {{V_{\text{cement}} } {V_{\text{total}} }}} \right. \kern-0pt} {V_{\text{total}} }}}} = \frac{{V_{\text{void}} }}{{V_{\text{cement}} }}$$

(9)

where V_void, V_cement, and V_total are the volume of voids, the volume of cement, and the total volume of the sample, respectively. The following equation can be obtained by modifying Eq. 9.

$${n \mathord{\left/ {\vphantom {n {C_{\text{vi}} }}} \right. \kern-0pt} {C_{\text{vi}} }} = \frac{{V_{\text{void}} }}{{V_{\text{solid}} }} \cdot \frac{{V_{\text{solid}} }}{{V_{\text{cement}} }} = e \cdot \left( {\frac{{V_{\text{solid}} }}{{V_{\text{cement}} }}} \right)$$

(10)

where V_solid is the volume of solids (sand particles and cement particles). Noting that V_solid = V_cement + V_sand, where V_sand is the volume of sand particles, Eq. 10 can be further derived as follows:

$${n \mathord{\left/ {\vphantom {n {C_{\text{vi}} }}} \right. \kern-0pt} {C_{\text{vi}} }} = e \cdot \left( {\frac{{V_{\text{sand}} + V_{\text{cement}} }}{{V_{\text{cement}} }}} \right) = e \cdot \left( {\frac{{{{m_{\text{sand}} } \mathord{\left/ {\vphantom {{m_{\text{sand}} } {G_{\text{s,sand}} }}} \right. \kern-0pt} {G_{\text{s,sand}} }} + {{m_{\text{cement}} } \mathord{\left/ {\vphantom {{m_{\text{cement}} } {G_{\text{s,cement}} }}} \right. \kern-0pt} {G_{\text{s,cement}} }}}}{{{{m_{\text{cement}} } \mathord{\left/ {\vphantom {{m_{\text{cement}} } {G_{\text{s,cement}} }}} \right. \kern-0pt} {G_{\text{s,cement}} }}}}} \right)$$

(11)

where m_cement and m_sand are the mass of cement and sand, respectively. Then, Eq. 6 (also Eq. 12) can be finally derived by substituting m_cement = cc·m_sand as follows:

$${n \mathord{\left/ {\vphantom {n {C_{\text{vi}} }}} \right. \kern-0pt} {C_{\text{vi}} }} = e \cdot \left( {\frac{{G_{\text{s,cement}} + {cc} \cdot G_{\text{s,sand}} }}{{{cc} \cdot G_{\text{s,sand}} }}} \right) = e \cdot \left( {1 + \frac{{G_{\text{s,cement}} }}{{{cc} \cdot G_{\text{s,sand}} }}} \right)$$

(12)