Soil–cement is an environmentally friendly road construction technique for base and
subbase materials, which allows employing soils placed in the right-of-way of the road or in the
surroundings, by improving its engineering properties. With this technique, it is possible to reduce
the over-exploitation of quarries, the necessity of landfills and the pollutant gas emission due to
the reduction of aggregate fabrication and transport. The manufacturing of soil–cement is generally
controlled by means of the Uniaxial Compressive Strength (UCS) test at seven days, according to the
regulations of each country. Nonetheless, one of the properties that best defines the performance of
soil–cement is the Flexural Strength (FS) at long term, usually at 90 days. The aim of this paper is to
develop new equations to correlate the UCS and the FS at long term and the UCS at seven days and
at 90 days. Obtained results validate the proposed models and, hence, the flexural strength can be
predicted from the Uniaxial Compressive Strength at seven days, allowing, if necessary, correcting
measures (recalculation or rejection) in early stages of the curing time to be taken.
