Mix design of low-cement concrete with particle packing concept and superplasticizer application

Abstract

The amount of cement paste used in concrete depends on aggregate particle packing, where the denser combination among particles with different particle sizes results in a minimum volume of voids (Vv). Theoretically, cement paste volume (Vp) is required to fill the void with the combination of fine and coarse aggregate, i.e., Vp/Vv = 100%. The purpose of this paper was to propose a concrete mix design method that could maximize the particle packing of aggregates to reduce the cement content in concrete mixture, hence producing low-cement concrete (LCC). The variables proposed were the ratio between the volume of paste to the volume of voids (Vp/Vv) as opposed to the cement content and the use of superplasticizer to control the workability of the fresh concrete. The results showed that by the combination of multi-sized coarse aggregates and fine aggregate, the smallest void volume of 23.5% could be achieved. The theoretically lowest cement content needed for a mixture with w/c 0.5 was 287 kg/m3. However, after trial mixing, the cement requirement was found to be almost equal with conventional concrete, i.e., about 310 kg/m3. Workability of the mixture depended on the paste volume to void volume ratio (Vp/Vv > 100%) and was greatly influenced by the superplasticizer content. The use of excessive superplasticizer could cause bleeding due to lack of fine particles in the low cement concrete mixture. The use of cementitious material, such as fly ash by 50%, to replace cement, significantly improves the workability and reduces the cement content below the minimum cement requirement with similar compressive strength as the water to cementitious ratio mainly controls compressive strength.

Effect of micro-magnesium oxide admixture on rheological and compressive strength properties of class G well cement

“…Furthermore, the type II micro-sized magnesium oxide makes this increment more apparent than the type I micro-sized magnesium oxide. This probably arises both from the more irregular shape of MMII (the sphericities of MMII and MMI are 0.81 and 0.84 respectively, D 50 ) and the particle packing phenomenon at the early age of the OWC slurry (Antoni et al, 2019;Chateau, 2012;Kumar and Santhanam, 2003;Mooney, 1951). In addition to the particle size, other factors, like the surface morphology, will also play an important role in the initial fluidic condition of the cement slurry.…”