Perforated cenospheres used to enhance the engineering performance of high-performance cement-slag-limestone ternary binder

Abstract

Slag-limestone-cement ternary mixed binder is a new type of cementitious material. There are 1137 published literatures on this new type of cementitious material in the Scopus database, but so far, no papers have been published on the research of reactive internal curing of this new type of cementitious material. One kind of fly ash is called a cenosphere with a very thin outer shell and a hollow center. Cenospheres generate pores through chemical etching, thereby achieving the effect of self-curing. This article conducted multiple experimental studies to ascertain the impact of perforated cenospheres regarding the execution of cement-slag-limestone binder. The mixture samples with different dosage of perforated cenospheres and cenospheres are numbered C0 (control group), P3.3 (content of perforated cenospheres in the binder is 3.3 %), P6.6 (content of perforated cenospheres in the binder is 6.6 %), and C6.6 (content of perforated cenospheres in the binder is 6.6 %). Based on the results of autogenous shrinkage and compressive strength, perforated cenospheres as an internal curing agent not only reduces the autogenous shrinkage of cement-slag-limestone concrete, but also avoids a significant decrease in strength of cement-slag-limestone concrete. In fact, because of volcanic ash reactivity of advanced cenospheres and the internal curing effect, the compressive strength of P3.3 mixed mortar increased by 0.7 and 4 MPa compared to C0 mixed mortar at 7 and 28 days of age, achieving a dual effect of reducing shrinkage and improving strength. Secondly, the experimental results of Fourier transform infrared spectroscopy and X-ray diffraction showed that perforated cenospheres can undergo volcanic ash reaction with calcium hydroxide. The scanning electron microscope images indicate that the P3.3 and P6.6 mixed paste with added perforated cenospheres exhibit better and denser bonding between the perforated cenospheres and the matrix. In summary, the microscopic reactions of perforated cenospheres can enhance concrete's macroscopic qualities, which can be utilized as reactive internal curing materials.