Consolidation mechanism of materials obtained from sodium silicate solution and silica-based aggregates

A study based on the use of sodium silicate gels as binder for cold consolidation of silica-based aggregates has been investigated. The gels used as precursor of binder were synthesized by adding hydrochloric acid to a concentrated sodium silicate solution. Consolidated materials were obtained by mixing the previous solution before gelation with granular materials (fine silica powder and sand). The study of the gel–silica–sand ternary system shows that the existence domain of materials depends on the sand size distribution. The microstructure of gel–silica–sand ternary samples reveals the presence of the three components with a partial attack of grain surface. This was confirmed by FTIR experiments during the monitoring of the synthesis. Actually, the νasSiOSi broad band resulting from the average of the contribution of the set of Q4, Q3 and Q2 units with a sharp peak located around 1078cm−1, firstly shifts to lower wavenumber until 21days and then to higher wavenumber characteristic of dissolution/precipitation reactions. On the other hand, the consolidation of the material is strong when the amount of fine silica in the material is high leading to efficient mechanical properties. Therefore, consolidation could be explained by the dissolution of small particles of silica and their precipitation into the grain boundary of sand. ► Silicate gels were used as binder to consolidate granular material in basic medium. ► The existence domains and the component reactivity depend on the size of grains. ► A dissolution/precipitation reaction occurs during the material setting. ► The mechanical properties increase with increasing fine silica content.