Influence of superplasticizer type on the compresive strength of reactive powder mortars

Reactive powder mortar (RPM) mixtures cured at room temperature with different portland cement, silica fume and steel fibers were manufactured. The influence of the superplasticizer type on the RPM performance - in terms of w/c and compressive strength - was studied. The acrylic polymer (AP) admixture performed better than the naphthalene (SNF) or melamine (SMF) based superplasticizers in regard to lower water-cement ratio and higher compressive strength at ages after 3 days. The 1-day compressive strength of the RPM with the AP admixture was much lower than that of the corresponding mixtures with SNF or SMF when a C3A-free portland cement with a low specific surface area was used. This was due to a strong retarding effect of the early hydration when this cement was used in combination with some silica fume types. With other portland cements, the retarding in the early hydration caused by AP did not occur and therefore the 1-day compressive strength was quite high. The 28-day compressive strength of RPM specimens, cured at room temperature, were strongly dependent on the type of cement, silica fume and superplasticizer. However, the highest values obtained in this investigation (160-180 Mpa) were lower than those reported by the inventors of RPM (170230 Mpa).