Superplasticized Microcement Grouts

This paper examines the rheological and mechanical behavior of superplasticized microcement grouts to be used for the consolidation of porous systems (e.g. sand deposits, masonry walls of historical buildings). Five micro cements were used: they differed in chemical composition of the clinker, type of mineral addition (natural pozzolan or silica fume), and particle size distribution. Three different superplasticizing chemical admixtures - acrylic, napthalene, and melamine bases - were used, all with an active polymer content of 0.4% by mass of cement. The following properties of the grouts were investigated: fluidity (Marsh cone), compressive strength, stability (bleeding test). The acrylic polymer proved to be more effective than the naphtalene and melamine based products in reducing the mixing water to produce a given initial fluidity. Furthermore, the grouts produced with this superplasticizer displayed a lower fluidity loss with time. The performance of a specific mixture was also strongly dependent on the fineness of the binder and on the type of mineral addition. The compressive strength of the hardened grouts was primarily affected - especially at latter ages - by the water-binder ratio, independently of the type of superplasticizer. None of the mixtures considered showed any significant bleeding. A limited number of injection tests in columns of dense sand were also performed. For a given water binder ratio, the groutability of a mixture was greatly improved using the acrylic based superplasticizer in place of the melamine- and naphtalene-based products.