Yu Qijun

Concrete with Highly Active Rice Husk Ash

The overall aim was to investigate the effect of highly active rice husk ash (RHA) produced by an industrial furnace on some properties of concrete. The strength, pore volume and pore distribution of concrete and the Ca(OH)2 content in concrete were investigated by JIS A 1108 (Method of test for compressive strength of concrete), a mercury instrument porosimeter, and the thermogravimetric analysis, respectively. The results show that, with RHA replacement of cement, the compressive strength of concrete is increased evidently; the average pore radius of concrete is greatly decreased, especially the portion of the pores greater than 20 nm in radius is decreased while the amount of smaller pores is increased, and the more the RHA replacement, the less the amount of Ca (OH)2 in concrete. The latter two results are the main reasons for the strength enhancement of concrete.

Solidification of municipal solid waste incineration fly ash with cement and its leaching behaviors of heavy metals

The solidifying effect of cement addition on municipal solid waste incineration fly ash (MSWFA for short, collected from the gas exhaust system of MSW incinerator), the interaction of MSWFA with cement and water and the leaching of heavy metals from cement-solidified MSWFA are investigated. The main results show that: (1) when MSWFA is mixed with cement and water, H2 evolution, the formation and volume expansion of AFt will take place, the volume expansion can be reduced by ground rice husk ash addition; (2) heavy metals do leach from cement-solidified MSWFA and at lower pH more leaching will occur; (3) compared with cement—solidified fly ash, the leachate of solidified MSWFA is with higher heavy metal contents; (4) with the increment of cement addition leached heavy metals are decreased; and (5) concentrations of Zn, Mn, Cu and Cd in all the leachates can meet the relevant Standards of Japan, but as the regulations for soil and groundwater protection of Japan are concerned, precautions against the leaching of Pb, Cl− and Cr6+ and so on are needed.

Setting and Strength Characteristics of Alkali-activated Carbonatite Cementitious Materials with Ground Slag Replacement

The effect of the ground granulated blast-furnace slag (GGBFS) addition, the modulus n (mole ratio of SiO2 to Na2 O) and the concentration of sodium silicate solution on the compressive strength of the material, i e alkali-activated carbonatite cementitious material (AACCM for short) was investigated. In addition, it is found that barium chloride has a satisfactory retarding effect on the setting of AACCM in which more than 20% (by mass) ground carbonatite was replaced by GGBFS. As a result, a cementitious material, in which ground carbonatite rock served as dominative starting material, with 3-day and 28-day compressive strength greater than 30 MPa and 60 MPa and with continuous strength gain beyond 90 days was obtained.