Self-compacting concrete using pretreatmented rice husk ash

Self-compacting concrete was obtained by partially replacing Portland cement with a previously prepared rice husk ash Preliminary preparation included the thermal treatment of the ash under various conditions. The optimum technology of preparation, allowing to receive a homogeneous concrete mix is revealed. All concrete mixtures were designed in such a way as to have a slump flow of 680 ± 30 mm in diameter, which was achieved by using different dosages of a superplasticizer based on polycarboxylate ether. All mixtures with the replacement of cement by ash to 25 % meet the requirements for rheological characteristics and resistance to segregation. The bulk density for the samples with 10 %, 15 %, 20 % and 25 % of the rice husk ash was reduced by 3.19 %, 5.18 %, 5.58 and 6.37 % respectively, compared to the samples without ash. An increase in the rice husk ash content led to a decrease in the early mechanical properties, while the final strength of self-compacting concrete containing ash was comparable to conventional samples. This was achieved due to the pozzolanic activity of the ash. Inclusion of rice husk ash reduced the amount of portlandite in the system by obtaining an additional C-S-H gel, which led to matrix compacting and blocking of networks with open porosity.