Binary and Ternary Blended Portland Cements Containing Different Types of Rice Husk Ash

Abstract

Rice husk ash (RHA) is agricultural waste with high silica content that has had proven technical feasibility as a pozzolanic material since the 1970s. Notwithstanding, its use in mortars and concrete is limited by the standards currently utilized in some countries where RHA production is high and the aforementioned pozzolanic material is not standardized. This is the case of Spain, one of the main rice producers in Europe. Nowadays, the high pressure placed on the Portland cement production sector to reduce energy use and CO2 emissions has given rise to a keen interest shown in mineral admixtures for cement manufacturing. In this research, we intend to establish the contribution of different RHA types to final blended Portland cement properties (symbol “H” was used to identify RHA in standardized cements). The experimental results demonstrated that RHA with good pozzolanic properties (large specific surface and high amorphous silica content) had to be limited to 10% cement replacement because of the severe reduction in workability at higher replacement percentages. RHA with lower reactivity, such as crystalline RHA, or fly ash (FA), can be used to prepare binary and ternary blended cements with reactive RHA. It is possible to design the following cements: CEM II/A-H and CEM II/A-(H-V) It would also be possible to design cement (CEM II/B-(H-V) with replacement values up to 30% and the same 28-day mechanical performance observed for the Portland cement without mineral addition.