The interaction effects of four chlorine-free admixtures such as calcium formate (CF), triethanolamine, (TEA), triisopropanolamine (TIPA), and sodium sulfate (SS) on the compressive strength development of Portland cement mortars were investigated based on the design of experiment (DoE). The results showed that both the addition of CF and SS contributed significantly to the strength of cement mortars at early curing age. However, the interaction of CF and SS could hinder their respective positive effect on the strength of cement at 1 d. At later curing ages, CF was still beneficial in improving the late strength of cement, but SS had a negative effect on the strength of cement at 28 d. A negative effect of TIPA on the strength of cement was found at 3 d. However, the positive interactive effect of TIPA and CF was sufficient to offset the negative effect of TIPA on the strength of mortars at 3 d if the dosage of CF exceeded 2%. In addition, TEA had a positive influence on 7 d strength until a turning point was reached and the optimum dosage of TEA was approximately 0.013%.
Ming Sun,Congtao Sun,Peng Zhang,Nazhen Liu,Yantao Li,Jizhou Duan,Baorong Hou
This study investigated the effects of carbonation on the chloride binding of mortars containing simulated marine sand. Various admixtures were added, and metakaolin (MK), fly ash (FA), nano-Al 2 O 3 (NA), and aluminum (A) were considered as supplementary cementitious materials (SCMs) for use in mortars. Changes in free chloride content, total chloride content, bound chloride content, chloride binding rates, and pH values as a function of mortar depth were analyzed, and the effects of carbonation on the hydration products were also assessed. The results indicated that in the place of cement, SCMs could significantly increase the carbonation zone depth in mortar. The chloride ions migrated outward and inward under accelerated carbonation conditions in the mortar, generating two peak values for the chloride content in the mortars. Consequently, the incorporation of SCMs was beneficial for chloride ion migration in mortars under carbonation. Additionally, the bound chloride content and chloride binding rates were initially extremely low, then gradually increased, and finally stabilized with increased depth in the mortars under carbonation. Furthermore, the incorporation of SCMs resulted in the decreased chloride binding capacity of the mortars under accelerated carbonation, and Friedel’s salt gradually decomposed with carbonation.
Basic magnesium sulfate cement (BMSC) is a new type of gas-hardening magnesium cementitious material. In this study, basic magnesium carbonate was used as the raw material to obtain different active magnesium oxides by calcination at different temperatures to prepare BMSC with MgO:MgSO4:H2O = 5:1:20. The effect of different active magnesium oxides and different mineral admixtures and their content on the compressive strength of BMSC before and after soaking was analyzed, and the influence of MgO activity on the water resistance of BMSC was explored. The experimental results show that the activity of MgO has a significant impact on the water resistance of BMSC, and the water resistance of BMSC prepared from low-activity MgO is better, mainly because the hydration products of BMSC prepared by low-activity MgO are 5•1•7 phases. The MgSO4 in the 5•1•7 phase is insoluble in water; consequently, the free MgSO4 in BMSC is scarce; thus, the phase remains unchanged. After selecting low-activity MgO (T1000) and adding mineral admixtures to study its water resistance, it was found that the BMSC softening coefficient increases with an increase in the mineral admixture content. Both fly ash and silica fume were found to improve the water resistance of BMSC and increase its water resistance.
Architecture is the precipitation of history, not only the embodiment of technical level but also the inheritance of history and culture. Excellent architecture contains high historical value and emotional factors, and it continues to deepen over time. Nanotechnology is a new technology that was born in the late 1980s and is emerging. It mainly refers to the study of the laws of motion and interactions of electrons, atoms, and molecules in the composition system of matter in the range of 0.1 to 100 nm. Nanomaterials have special properties and structures, and the composite materials made of them have the effect of strengthening and toughening the polymer by virtue of their high-quality strength and toughness. Therefore, the aim of this text is to explore the application of nanocomposite building materials in modern architectural design and analyze the advantages and development trends of new building materials. The method in this paper is to use the method of experimental comparison to analyze the performance improvement effect of nanocomposite building materials on the current main building materials of concrete. By establishing a model to study the impact on the shrinkage and mechanical properties of cement-based materials, it can also improve the environmental performance and comprehensive evaluation of building materials. Corresponding conclusions are drawn through data comparison. When the amount of nanocomposite building materials is 1.5%, the chemical shrinkage value of the cement paste will increase by 58.2%, and the shrinkage strain will increase by 15.3%. When the fly ash content is 20%, the chemical shrinkage value of cement paste is reduced by 30.5%, and the shrinkage strain of concrete is reduced by 8.8%. Therefore, adding nanocomposite building materials to cement-based materials can promote cement hydration, optimize pore structure, and to a certain extent can make up for the shortcomings of mineral admixtures and achieve better improvement effects.
危险品化学品经营许可证（带存储）