Preparation Of Nano-Cement And Its Effect On Durability Of Ordinary Portland Cement

High Belite cement is a low-calorific-heat material that can be used as a nano-sized admixture in high-performance concrete to improve the durability of the concrete.This project uses limestone?red mud?and micro-silica fume as raw materials to prepare novel nano-Belite cement?NC?and nano-Belite-ferrite cement?FCF?clinker as a blend by chemical combustion technology to improve the performance of concrete.In the study,we characterized the red mud,NC and FCF clinker by XRD and SEM.At the same time,the morphology of the hydration properties of the two nanomaterials was observed by SEM.The crystal composition of the hydration products was analyzed by XRD.The exotherm of the NC materials was studied using a cement hydration heat tester,studying the degree of hydration of C-S-H and the change of chain length of Si,the nanomaterials as admixtures added to OPC for flexural and compressive strength to mechanical properties testing,and the carbonation performance,resistance to chloride ions,and sulfate radicals were performed in terms of durability.The ion permeability and the study of the unsteady chloride ion transport?RCM?experiments of concrete.Research indicates:1,when the raw material CaO:?CaO+SiO₂?=62.5%,holding temperature is 1150°C,holding time 2 hours,the mass of foaming agent is 0.203 of the raw material,the content of C₂S in the NC material obtained is 87.2%,The best of all the experimental schemes were:the particle size of the material was about 300 nm,the specific surface area was 4.3 times that of the OPC,and the hydration degree of the 28th day was 28.7%,in which the hydration products were mainly C-S-H,Ca₅?SiO₄?₂?OH?₂ and Ca?OH?;Total heat release of the NC during the first 72 hours of hydration is much lower than OPC,and with the increase of NC,the heat release rate of OPC will decrease and the total amount of heat release will decrease;The influence of high dose SP on OPC becomes smaller;NC material is added as an admixture to the benchmark cement,and the compressive strength on the 28th day is 16.9%higher than that of the OPC test piece,indicating that the NC can improve the compressive performance of the OPC,but the fracture resistance The intensity does not change much.2.When the mass ratio of red mud to calcium carbonate is 1.5,the sintering temperature is 815°C,the holding time is 2 hours,and the foaming agent quality is 0.203 of the raw material,the obtained FCF has the best effect in all experimental schemes and has hydration.The sum of active C₄AF and C₂S is the highest?47.2%for C₄AF and 8.6%for C₂S?;the particle size of the material is around 300 nm,and its specific surface area is much larger than that of OPC?FCF is 2.5 times of OPC?;28 days of hydration product of C₄AF is C₄?A,F?H₁₃that can be clearly seen in the product morphology,and its hydration products are mainly C-S-H,?CaO?₃Al₂O₃?H₂O?₆,Ca₅?SiO₄?₂?OH?₂,Ca?OH?₂.3.In terms of durability,the porosity of 28-day-old specimens with different NC content increases with the increase of the content,and the porosity of the specimen with 5%content is the lowest,being 7.25%,which is lower than that of OPC specimens.The 56-day carbonization depth of the 5%sample is 56.5%of that of the OPC sample,indicating that its carbonization resistance is higher than that of the OPC and other additives;the sample incorporating the nano-Belite cement The amount of crystallization is lower than that of the OPC,and the more the amount of nano-Belite cement is,the less the amount of crystallization on the surface of the specimen,indicating that the nano-Belite cement material can improve the crystallization of OPC for Na₂SO₄.The unsteady chloride ion migration coefficient of the5%sample was lower than that of the OPC sample at all ages,indicating that 5%of the amount of nano-Belite cement material can significantly improve the carbonization resistance and chloride ion penetration of OPC.The main reason for the performance is that Nano Belite cement reduces the porosity of OPC and improves durability.