Chen Yimin

The Reaction Mechanism between MgO and Microsilica at Room Temperature

It was proved that MgO and MicroSilica can react at room temperature, giving a hardened product primarily comprised of Mg(OH)2 and Magnesium Silicate Hydrate (M-S-H). The reaction ratio and process and the chemical composition of M-S-H were studied and analyzed by QXRD and DTA-TG. The experimental results indicate that much Mg(OH)2 and less M-S-H was increased slowly. The chemical composion of M-S-H would vary with the mix proportion in the hydration process, but M1.32SH2.37 is finally the approximate form.

Effect of coal gangue with different kaolin contents on compressive strength and pore size of blended cement paste

The effects of activated coal gangue on compressive strength, porosity and pore size distribution of hardened cement pastes were investigated. Activated coal gangue with two different kaolin contents, one higher and one lower, were used to partially replace Portland cement at 0%, 10%, and 30% by weight. The water to binder ratio(w/b) of 0.5 was used for all the blended cement paste mixes. Experimental results indicate that the blended cement of activated coal gangue mortar with higher kaolin mineral content has a higher compressive strength than that with lower kaolin mineral content. The porosity and pore size of blended cement mortar were significantly affected by the replacement of activated coal gangue.

Microstructure and Composition of Hydration Products of Ordinary Portland Cement with Ground Steel-making Slag

The effect of ground steel-making slag on microstructure and composition of hydration products of ordinary Portland cement (OPC) was investigated by mercury intrusion porosimetry (MIP), X-ray diffraction (XRD) and differential thermal analysis (DTA). Results show that ground steel-making slag is a kind of high activity mineral additives and it can raise the longer-age strength of OPC mortar. The total porosity and average pore diameter of OPC paste with ground steel-making slag increase with the increase of the amount of ground steel-making slag replacing OPC at various ages, while after 28 days most pores in OPC paste with ground steel-making slag do not influence the strength because the diameter of those pores is in the rang of 20 to 50 nm. The hydration mechanism of ground steel-making slag is similar to that of OPC but different from that of fly ash and blast furnace slag. The hydration products of ground steel-making slag contain quite a lot of Ca(OH)2 in long age.

Analysis of pore structures and their relations with strength of hardened cement paste

Three cement samples were prepared, including OPC consisted of 100wt% portland cement, PFA consisted of 70wt% portland cement and 30wt% fly-ash, and CA consisted of 70wt% portland cement and 30wt% modified fly ash. The strength of hardened cement paste of these samples was tested and their pore structures were determined by a mercury intrusion porosimeter. Moreover, the data of the pore structures of three samples were comprehensively analyzed. The relations between the pore structures and the compressive strength of the three samples were studied. The experimental results show that the relations between the porosity determined by the mercury intrusion porosimeter and the compressive strength are not notable, and the total pore surface area, the average pore diameter and the median pore diameter could be used to explain the difference of the strength of the tested samples.