Title: Modified Reactive Powder Concrete with Artificial Aggregates
Author(s): S. Monosi, G. Pignoloni, S. Collepardi, R. Troli, and M. Collepardi
Publication: Symposium Paper
Appears on pages(s): 447-460
Keywords: aggregate; concrete (fiber-reinforced); silica fume; superplasticizer
Reactive Powder Concretes (RPC) - in form of superplasticized cement mixtures with silica fume, steel fibers, quartz fine sand (100-400 um) and/or limestone coarse aggregate (0.1-8 um ) - were studied in comparison with modified RPC where artificial aggregates substituted for natural aggregates. Artificial aggregates were obtained by grinding portland clinker coarsely so that fine and coarse aggregate were obtained with approximately the same particle size distribution of natural fine quartz (100-400 um and limestone gravel (O.l-8 mm) respectively. The source of clinker-aggregate was the same as that used for portland cement as binder of RPC. The idea was to improve the bond strength between cement paste and aggregate due to some hydration of the clinker-aggregate surface. RPC specimens were cured at room temperature (2OO C) or steam-cured at low or high pressure at 90°C or 160°C respectively. Compressive strengths were measured as a function of time at 1-28 days. The 28-day compressive strength level was as high as 200 MPa. Regardless of the curing temperature, compressive strength of RPC was increased by about 20 MPa when clinker-aggregate was used instead of natural aggregates. These results indicate that the bond strength of the interface between cement paste and aggregate is improved when clinker particles are used instead of natural stones. Scanning electron microscope observations of the microstructure confirmed this hypothesis and indicated that the interface between cement paste and natural aggregate is the weak point in RPC.