Chang Hui Yang

Adsorption of Calcium Lignosulphonate Water Reducer on Alkali-Activated Slag Cement Pastes

This paper shows how calcium lignosulphonate（CSL）water reducer affects the adsorption and rheological properties of alkali-activated slag cement (AASC) pastes activated by NaOH. It was concluded that the adsorption of water reducer on AASC pastes depended directly on the dosage of the water reducer and the retarder. Slag particles grounded with the retarder YP-3 adsorbed one and a half times of water reducer CSL as much as pure slag particles at 1% mass of the slag, and the absolute value increment of the zeta potential of the AASC suspension containing the retarder YP-3 is 14.00mV, compared with 9.25mV in the system without YP-3. Besides, the AASC pastes activated by NaOH containing the retarder YP-3 show better rheological properties and lower fluidity loss over time.

The Influence of pH on the Formation and Stability of Thaumasite

The samples were prepared to study the influence of pH on the formation and stability of thaumasite using Fourier transform infrared and X-ray diffraction to analyze the composition of the samples. The erosion solutions with the pH arranged from 9.5 to 13.5 prepared by sodium bicarbonate, sodium hydroxide and 5% sodium sulfate. The experimental data for three years has been given in the paper. The result of the research indicates that the value of pH at 10.5 is the optimum pH for the forming of thaumasite and when the pH comes up to 11.5, thaumastie can form but it will decompose in the solution.

Development of Alkali Activated Slag Cement Based Ecomaterial and its Environmental Coordination Evaluation

The slag is used as solid dispersing component with addition of a little amount of alkali component, a clinker free, alkali activated slag cement based ecomaterial (AASCBE) has been developed. The experiment results showed that the alkali activated slag cement based ecomaterial has excellent mechanical performances and durability, i.e., low energy consumption in manufacture, low environmental pollution, increased utilization of solid waste, enhanced efficiency of solid waste utilization, the heat from waste tyre or municipal domestic waste burning can be used for the material production, the CO2 can be recycled as a resource for the material curing and making the regeneration and recirculation possible. LCA study of this material shows that the complex environmental index of the alkali activated slag cement based ecomaterial is 2.9337×10-12 year/ton, which takes only 19.8% of that for Portland cement or 25.9% of that for slag cement, such material has certain environmental compensation function, therefore it is a new ecomaterial with excellent environmental coordination.

Adsorption of Naphthalene-Based Water Reducer on Alkali-Activated Slag Cement

In this work, the adsorption of naphthalene-based water reducer (FDN) on slag ground with or without the composite retarder YP-3 and PN (YP) in alkali-activated slag cement (AASC) activated by water glass (WG) has been studied in detail. The results show that the effect of the adsorption of water reducer on AASC depends directly on the dosage of the water reducer and on the composite retarder used. For example, mixed slag particles adsorb thrice as much water reducer FDN than pure slag particles at 1% mass of the slag, and the absolute value increment of the zeta potential of the AASC suspension containing the composite retarder is 8.61 mV, compared with 1.99 mV in the system without the composite retarder. Moreover, the AASC pastes activated by WG containing the retarder YP show better rheological properties and lower fluidity loss over time.

Adsorption Characteristics of Surfactant on Slag in Alkali Activated Slag Cement System

Alkali activated slag cement was a new green cementing material with many performances. Whereas, high viscosity and bad workability of the fresh mixture were the matters to embarrass its application. For exploring the special superplasticizer, the adsorption characteristics of surfactant on slag was studied, by UV Vis Absorption Spectrum Method. The results showed, first, the adsorbed amount of cationic surfactant [CH3(CH2)11N(CH3)3]Cl was the highest value among the five surfactants, 12.8 mg/g. Second, the effect of alkali on the adsorbed amount of surfactant was complex. Cationic surfactant had cooperativity with alkali. But, adding water glass, the adsorbed amounts of the surfactants on slag were negative, because it was both colloid property and alkali solution property. Finally, the retarder of YP-3 made the adsorbed amount of ionic surfactant to increase, due to YP-3 contracted electric double layer in the surface of slag.

Influence of New Type Water Reducer Agent YC on Properties of Alkali-Activated Slag Cement Mortar

Through test on influence of water reducer agent YC on properties of alkali activated slag cement mortar, it is shown that water reducer agent YC has favorable plasticizing effect on alkali activated slag cement. When the alkali component is NaOH, the water reducer agent YC gives a water reduction rate of 22.0% to the alkali activated slag cement mortar and the flow ability loss with time is small. The water reducer agent can be adsorbed on the surface of slag and enhance theξpotential of the alkali activated slag cement system.

Effect of Ground Phosphate Slag on the Resistance to Chloride Ion Penetration of Concrete

The permeability resistance of concrete with ground phosphate slag(GPS) against chloride ion penetration was tested according to ASTM1202 and by nitrogen adsorption method. Test results show that by adding ground phosphate slag to concrete, the chloride diffusion coefficient of concrete decreases, and the permeability resistance of concrete against chloride ion penetration increases with improvement of its pore structure. The pores in concrete are refined and the percentage of the pores with diameter less than 20nm in concrete increases. The improvement of pore structure of the concrete by ground phosphate slag is much better than that by the ground granulated blast furnace slag or fly ash, while the addition is 30 percent. The ability of additive to improve the permeability resistance of concrete against chloride ion penetration is in following order: fly ash > ground phosphate slag > ground granulated blast furnace slag.

Research on Morphology Control of PVA/Na-MMT Composite During Preparation

The morphology of PVA/Na-MMT composite under different freezing technology conditions was studied. Inlfuence of PVA content and frozen conditions on microstructure and formation mechanism of PVA/Na-MMT composite materials were analyzed using scanning electron microscopy(SEM). The experiment results show that the structure of freeze-dried PVA/Na-MMT composite is influenced by both frozen technology and PVA dosage. PVA/Na-MMT composite frozen in Low-temperature refrigerator presented honeycomb-like structure when PVA dosage was 1%, and when the dosage of PVA was 2%, 3%, 4% respectively, the composite exposed wrinkle superposition structure. In liquid nitrogen frozen, Fiber-like structure of PVA/Na-MMT composite was obtained when the PVA content more than 3%.

The Effect of Surfactant and Alkali on the Surface Tension of Simulated Solutions of Alkali Activated Slag Cement System

Alkali activated slag cement and concrete are high strength, rapid hardening, low heat of hydration, good durability and so on. Whereas, too high viscosity and bad workability of the fresh mixture is the crux of the matter to embarrass application of alkali-activated slag cement and concrete. Development of special superplasticizer for alkali activated slag cement and concrete is a worth exploring way to solve the problem, and the study on the surface tension of simulated solutions of alkali activated slag cement system is one of the basic researches about the special superplasticizer. In this paper, the surface tension of surfactant-alkali-water was studied by Wilhelmy method. The results showed, first, water-glass had the best efficacity of several alkali activators, when the modulus of water-glass was 1.5 and dosage of water-glass by Na2O was 8%, the surface tension was reduced by 33 mN/m and reduced to 39.9mN/m; second, [CH3(CH2)9]2N(CH3)2Cl had the best efficacity of several surfactants, when the concentration of [CH3(CH2)9]2N(CH3)2Cl was 50g/L, the surface tension was reduced by 35.3 mN/m and reduced to 32.5 mN/m; finally, the effect of surfactant and alkali together on the surface tension of water was complex, surfactants had hardly effective in water glass.

Study on Expansion of Cement-Based Material with Addition of Magnesium Oxide

In this paper, the influence of the types and addition dose of MgO expanding agent and the age of cement on expansion value and expansion performance of cement based material added with MgO expanding agent was systematically studied.The expansion characteristics of cement based material added with MgO expanding agent or calcium sulphoaluminate expanding agent were compared. The expansion of such material increases with the addition dose of MgO expanding agent and cement mortar age. During the test period, the expansion of cement based material increases continuously. The light-burned MgO expanding agent modified by CaO expanding agent is able to increase the 28d expansion of such material effectively. The temperature of calcination for the heavy-burned MgO expanding agent is higher than that of light-burned one, thus the heavy-burned MgO expanding agent has a rather dense structure with slow hydration rate and gives a small expansion of the cement based material at early age, showing an obvious expansion delay. The calcium sulphoaluminate expanding agent gives most expansion of the material in the early 28d and there is small expansion at middle and later age of the material.