Method for modifying clay soils with gypsum

A method of reducing the swell potential of an expansive clayey soil comprising at least one expansive clay mineral, the proportion of the weight of the at least one expansive clay mineral relative to the total weight of the expansive clayey soil being PECM, the expansive clayey soil having a water content and a cation exchange capacity (CEC), the method comprising:

• (a) carrying out a forcefield-modified molecular level simulation to determine an amount of a swelling reduction agent to be incorporated into the expansive clayey soil to form a swelling reduction agent incorporated expansive clayey soil with a reduced swell potential Si(soil) that is no greater than a pre-set level T*,
• wherein the swelling reduction agent incorporated expansive clayey soil comprises a swelling reduction agent incorporated at least one expansive clay mineral having a swell potential represented by Si(ECM) and Si(soil) equals Si(ECM)×PECM,
• wherein the swelling reduction agent comprises gypsum at a first weight percent of the amount of the swelling reduction agent, and at least one exchangeable cation selected from the group consisting of Ca2+ and Mg2+ at a second weight percent of the amount of the swelling reduction agent,
• wherein the sum of the first weight percent and the second weight percent is no greater than 100%,
• wherein the forcefield-modified molecular level simulation comprises molecular mechanics, molecular dynamics, and Monte Carlo simulation techniques configured to simulate the swell potential of the swelling reduction agent incorporated at least one expansive clay mineral Si(ECM) based on the water content as an initial water content and CEC of the expansive clayey soil, the gypsum at the first weight percent of the amount of the swelling reduction agent, and/or the at least one exchangeable cation at the second weight percent of the amount of the swelling reduction agent, and
• (b) incorporating the amount of the swelling reduction agent into the expansive clayey soil to form the swelling reduction agent incorporated expansive clayey soil.