Chen Meizhu

Optimization of blended mortars using steel slag sand

A new kind of mortar made of ground granulated blast-furnace slag (GGBFS), gypsum, clinker and steel slag sand (<4.75 mm) was developed. The ratio of steel slag sand to GGBFS was 1:1 and the amount of gypsum was 4% by weight while the dosage of clinker ranged from 0% to 24%. The optimization formulation of such mortar was studied. The content of steel slag sand should be less than 50% according to the volume stability of blended mortar, and the dosage of clinker is about 10% based on the strength development. Besides strength, the hydration heat, pore structure and micro pattern of blended mortar were also determined. The experimental results show the application of steel slag sand may reduce the dosage of cement clinker and increase the content of industrial waste product such as GGBFS, and the clinker is also a better admixture for blended mortar using steel slag sand.

Early-age electrical resitivity and reactive capacity of mineral admixtures in mortars

A non-contacting electrical resistivity measurement device used to investigate the effect of different types and contents of mineral admixtures on the hydration performance of mortanrs during early age. The experimental results show that the changes of measured resistivity with time of hydration can be used to describe the hydration characteristics of cement-based materials, as well as the physical and chemical behavior of fly ash; blast furnance slag and silica fume at the very early ages. With an increasing replacement ratio of mineral admixtures, for the specimens blended with fly ash or slag, the resistivity increases firstly, then the following flatting period extends and after setting the resistivity increasing becomes slow and consequently a lower resistivity value at 24 hours occurs. This is due to the dilution effect and lower pozzolanic/hydraulic activity of fly ash and slag. However, for the samples incorporated with silica fume, the resistivity value through 24 hours is lower with shorter flatting period and larger slope in the resistivity curves, which is because of its particle size effect and higher pozzolanic activity of silica fume. Moreover, non-contacting resistivity measurement might provide a helpful information to predict the long term performance including the durability of cement-based materials at early ages.

Physical and Chemical Properties of Asphalt Binders Modified with Waste Engine Oil

Waste engine oil (WEO) modified asphalt was prepared by melt blending. The objective of this paper is to investigate the influence of WEO on the physical properties, chemical compositions and microstructure of asphalt. Penetration, softening point and ductility were tested to evaluate the effect of WEO on basic properties of asphalt. Then the rheological properties of modified asphalts were characterized based on rotational viscometer (RV), bending beam rheometer (BBR) and dynamic shear rheometer (DSR) tests. Finally, SARA (saturates, aromatics, resins and asphaltenes) fractions, Pyrolysis-gas chromatography (PyGC) and Fourier transform infrared spectroscopy (FTIR) tests were carried out to investigate the influence of WEO on chemical properties of asphalt. The experimental results indicate that the chemical compositions of WEO is similar to asphalt with similarity-intermiscibility characteristics, and both are mainly physical blending rather than chemical reaction. The addition of WEO can reduce the viscosity, the colloidal instability index (Ic) value, the Carbonyl (C=O) and Sulfoxide (S=O) indexes of asphalt. Moreover, the viscous components of asphalt are significantly increased in low temperature. It is beneficial to the anti-aging properties and low-temperature crack resistance of asphalt, while the temperature sensitivity and high-temperature stability of asphalt remains to be further improved.