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The objective of this study was to assess the feasibility of using the plant-source polymer of the matcha powder as a composite admixture for hemihydrate gypsum. Hemihydrate gypsum was mixed with different contents of matcha powder, and then the water requirement for the normal consistency, setting times, density, strength, hydration and microstructure of the hardened mixture were evaluated. The experimental results showed that it increased the water requirement for the normal consistency, and it regulated the setting times and reduced the density. Hemihydrate gypsum with more matcha powder had the higher water requirement, longer setting times and lower density. Less than 1% matcha powder had slight impact on the strength of hardened paste, but more than 1% matcha powder had a remarkable one. Matcha powder changed the hydration process and prolonged the induction and acceleration period. Small needlelike crystals were transformed into longer, larger and thicker ones as more matcha powder was mixed. This case is closely related to the prolongation of the induction and acceleration period. Besides, more and larger pores were observed in the hardened paste with more matcha powder. It is attributed to the appearances of the tea polyphenol in matcha powder and the larger and longer crystal morphology in hardened paste as well as the high water requirement for the normal consistency. These results are important to the application of matcha powder as a composite admixture for the hemihydrate gypsum as well as the prosperity and development of the tea industry. [ABSTRACT FROM AUTHOR]

Current management for red mud is insufficient and a new method is needed. A series of experiments have been carried out to develop a new approach for effective management of red mud. Mortars without or with 3%, 6% and 9% red mud were prepared and their fresh and hardened properties were measured to access the possibility of recycling the red mud in the production of red cement-based mortar. The mechanisms corresponding to their mechanical performance variations were explored by X-ray powder diffraction and scanning electron microscopy. The results show that the fresh mortars with red mud present an increase of viscosity as compared with the control. However, little difference is found when the content of red mud is altered. It also can be seen that red mud increases flow time and reduces the slump flow of the mortar. Meanwhile, it is found that mortar with red mud is provided with higher air content. Red mud is eligible to adjust the decorative mortar colour. Compressive strength of mortar is improved when less than 6% red mud is added. However, overall it has a slightly negative effect on tensile bond strength. It decreases the Ca(OH)2 content and densifies the microstructure of hardened paste. The heavy metal concentrations in leachates of mortars with red mud are much lower than the values required in the standard, and it will not do harm to people’s health and the environment. These results are important to recycle and effectively manage red mud via the production of red cement-based mortar. [ABSTRACT FROM AUTHOR]

Current management for red brick waste is insufficient, and a new method is needed. We sought to develop a new approach for effective management. Red cement-based decorative plasters were prepared with red brick waste powder (RBWP), white Portland cement, quartz sand, redispersible emulsion powder, hydroxypropyl-methyl cellulose ethers and silicone hydrophobic agent. The colors, water absorptions and strengths of different plasters were investigated, and the mechanisms responsible for their performance variations were explored by high-resolution transmission electron microscopy, X-ray powder diffractometry and scanning electron microscopy. The relative economic and environmental benefits were also analyzed. The feasibility of recycling RBWP in the production of cement-based red decorative plaster for walls was evaluated. The resulting plaster provided appropriate color adjustment, and the water resistance of the plaster was not greatly affected. The compressive and flexural strengths of plaster were improved. However, the improvement decreased as the sand replacement ratio increased. The tensile bond strength of the plaster is related to the RBWP content. More RBWP negatively affects the tensile bond strength of the plaster. Calcium hydroxide in the hardened paste varies with RBWP content. This variation correlates with the appearance and level of pozzolanic reaction in the plaster with RBWP. Plaster with RBWP has a denser microstructure than the control. In addition to the pozzolanic reaction, this denser microstructure also contributes to performance improvements such as compressive and flexural strengths. To improve the economic and environmental efficiencies, it is also feasible to recycle RBWP in the production of cement-based red decorative plaster for walls. These results demonstrate the effective use of red brick waste. They also provide a reference strategy for the management of red brick waste in other developing countries that are carrying out or will carry out urbanization activities. [ABSTRACT FROM AUTHOR]

Abstract: The objectives of this study were to assess the feasibility of application of dry composite electroplating sludge (CEPS) into preparation of cement-based decorative mortar as green pigment, and to find a new disposal and resource approach for it. Color, water absorption, strength, hydration and leachability of cement-based decorative mortar are investigated. The results show that CEPS can adjust the mortar color well. Although CEPS leads to the increase of mortar water absorption, the water absorption of mortar prepared with 5% CEPS still meets the requirement stated in the Chinese Building Material Industry Standard JC/T 1024-2007. The mortars with CEPS are provided with nearly same compressive, flexural and tensile bond strengths as these of the control. Cement hydration products such as C–S–H gel, Ca(OH)2 and the entringite all can be observed in different specimens. The denser microstructures than that of the control are formed in the mortars with CEPS. It is found from almost similar intensity in Ca(OH)2 peak at 18.007° that CEPS has not notably influence on the cement hydration. It is also evident that heavy metal concentrations in leachates of the mortars with CEPS are far lower than recommended in the Chinese National Standard GB5085.3-2007. It is safe to people's health and environment that CEPS is recycled as green pigment to produce cement-based decorative mortar. [Copyright &y& Elsevier]

• Compressive strength of mortar with VAEC cured at 60 °C is significantly increased. • High curing temperature facilitates the formation of carboxyl-containing substances. • High curing temperature reduces the thickness of polymer film. • The pore structure relates to the content of VAEC and curing temperature. In this work, the roles of curing temperature on the mechanical performance and microstructure of cement paste/mortar modified by VAEC dispersible powder are reported. The experimental results show that as compared with mortars cured at standard condition, the strengths of mortars cured at 60 °C are enhanced, whereas the 100 °C curing temperature makes a side effect. The formation of carboxyl-containing substances is facilitated at elevated temperatures and meanwhile the pores are refined and the thickness of polymer film is reduced together with the pores in the polymer film are increased. These alterations are responsible for the changes of mechanical performances. [ABSTRACT FROM AUTHOR]

• Desulfurized ash increases the water requirement. • It decreases Zeta electrical potential and strengths. • It prolongs the setting times. • There is not any new phase in the hardened paste with desulfurized ash. • It alters the morphology and increases the pores in the hardened paste. This work aimed to investigate the feasibility of utilizing the low-quality desulfurization ash from semi-dry flue gas desulfurization by mixing with α-hemihydrate gypsum, and then the environmental issues resulted from low-quality desulfurized ash from semi-dry flue gas desulfurization can be resolved, and both economic and ecological benefits are brought to the related industries. Thus various contents of low-quality desulfurization ash were mixed into the α-hemihydrate gypsum and these pastes with desulfurization ash were prepared, and then the water requirements for the normal consistency, Zeta electrical potentials, setting times and strengths of the pastes with desulfurization ash were evaluated, also hydration products and microstructures of these mixtures were identified by Fourier transform infrared (FT-IR), X-ray diffraction (XRD) and Scanning electron microscope (SEM) respectively in this work. The results indicate that desulfurized ash increases the water requirement for the normal consistency, and it decreases Zeta electrical potential and strengths, and it prolongs the setting times. Higher water requirement for the normal consistency, lower absolute value of Zeta electrical potential, longer setting times and lower strengths will be found as more desulfurized ash is mixed into the paste. But the strengths of the pastes with 24% desulfurized ash still meet the requirement for the building. Lower absolute values of Zeta electrical potentials imply the reaction appearance of calcium oxide to calcium hydroxide. FT-IR and XRD results indicate that dihydrate gypsum is the main hydration product, and calcium sulfite, calcium carbonate and calcium hydroxide are also appeared in the hardened pastes with desulfurized ash and they do not participate in the reaction and there is not any new phase in the hardened pastes with desulfurized ash. SEM observation shows that desulfurized ash alters the dihydrate gypsum morphology and increases the pores in the hardened pastes. The crystal becomes thicker and more pores can be found in the hardened pastes as more desulfurized ash is mixed. These results will provide a reference for the desulfurized ash application into the hemihydrate gypsum and contribute to the sustainable management of low-quality desulfurized ash and find an approach for its application with a large scale. [ABSTRACT FROM AUTHOR]