Kai Wu

Utilization of municipal solid waste incineration fly ash for sulfoaluminate cement clinker production

The feasibility of partially substituting raw materials with municipal solid waste incineration (MSWI) fly ash in sulfoaluminate cement (SAC) clinker production was investigated by X-ray diffraction (XRD), compressive strength and free expansion ratio testing. Three different leaching tests were used to assess the environmental impact of the produced material. Experimental results show that the replacement of MSWI fly ash could be taken up to 30% in the raw mixes. The good quality SAC clinkers are obtained by controlling the compositional parameters at alkalinity modulus (C(m)) around 1.05, alumina-sulfur ratio (P) around 2.5, alumina-silica ratio (N) around 2.0~3.0 and firing the raw mixes at 1250 °C for 2h. The compressive strengths of SAC are high in early age while that develop slowly in later age. Results also show that the expansive properties of SAC are strongly depended on the gypsum content. Leaching studies of toxic elements in the hydrated SAC-based system reveal that all the investigated elements are well bounded in the clinker minerals or immobilized by the hydration products. Although some limited positive results indicate that the SAC prepared from MSWI fly ash would present no immediate thread to the environment, the long-term toxicity leaching behavior needs to be further studied.

Effects of steel slag powder on workability and durability of concrete

The workability and durability of a type of sustainable concrete made with steel slag powder were investigated. The hydrated products of cement paste with ground granulated blast furnace slag (GGBFS) alone or with a combined admixture of GGBFS-steel slag powder were investigated by X-ray diffraction (XRD). Furthermore, the mechanism of chemically activated steel slag powder was also studied. The experimental results showed that when steel slag powder was added to concrete, the slumps through the same time were lower. The initial and final setting times were slightly retarded. The dry shrinkages were lower, and the abrasion resistance was better. The chemically activated steel slag powder could improve compressive strengths, resistance to chloride permeation and water permeation, as well as carbonization resistance. XRD patterns indicated that the activators enhanced the formation of calcium silicate hydrate(C-S-H) gel and ettringite (AFt). This research contributes to sustainable disposal of wastes and has the potential to provide several important environmental benefits.

Fractal Modeling of Pore Structure and Ionic Diffusivity for Cement Paste

Pore structure in cement based composites is of paramount importance to ionic diffusivity. In this paper, pore structure in cement paste is modeled by means of the recently proposed solid mass fractal model. Moreover, an enhanced Maxwell homogenization method that incorporates the solid mass fractal model is proposed to determine the associated ionic diffusivity. Experiments are performed to validate the modeling, that is, mercury intrusion porosimetry and rapid chloride migration. Results indicate that modeling agrees well with those obtained from experiments.

Modeling of Ionic Diffusivity for Cement Paste with Solid Mass Fractal Model and Lattice Boltzmann Method

AbstractIonic diffusivity is of critical importance to the service life of cementitious composites. In this paper, ionic diffusivity of cement paste is modeled with the solid mass fractal model and...

Durability of Calcium Sulphoaluminate (CSA) Composite Cement-Based Materials Made from Municipal Solid Waste Incineration (MSWI) Fly Ash

Municipal solid waste incineration (MSWI) fly ash was successfully used as a main raw material in sintering and preparing calcium sulphoaluminate (CSA) cement in laboratory. This work focused on effects of cement additives of MSWI fly ash, lime powder (LI), fly ash (FA), and slag powder (SL) on the durability of CSA cement-based materials. Compared with the hardened cement containing 10% MSWI fly ash alone, compressive strengths of samples containing 20% combined additives was improved significantly. When 20% combined additives were added the resistance to shrinkage, carbonation and sulfate attack was strengthened while the combined additives had negative effects on the resistance to water permeability.