Study On Inorganic Whiskers Reinforcing The Performance Of Basic Magnesium Sulfate Foamed Cement

As my country’s building energy consumption increases year by year,building energy efficiency is facing a huge challenge.The use of thermal insulation materials in building walls and envelopes is one of the effective ways to save energy in buildings.Inorganic foam cement thermal insulation materials are widely used in building thermal insulation materials because of their light weight,fire resistance,flame retardant,sound insulation and shock absorption.However,foamed cement has certain defects which greatly limit its application and promotion.In order to solve the problems of low early strength,high brittleness,large drying shrinkage,and easy cracking of foamed cement,a lightweight and high-strength foamed cement thermal insulation material is prepared.In this paper,Mg Cl₂·6H₂O was used as the raw material,and MgCO₃·3H₂O whiskers were prepared by adjusting and optimizing the crystallization conditions during the precipitation crystallization reaction,and then calcined to obtain MgO whiskers.In addition,calcium sulfate whiskers（CSW）and homemade basic magnesium sulfate whiskers（MHSH-512）,MgCO₃·3H₂O whiskers（MCH）and MgO whiskers are used as toughening and reinforcing materials and added to basic magnesium sulfate Cement（Basic magnesium sulfate cement,referred to as BMSC）is a cementing material,tetradecyl dimethyl betaine（BS-14）is a foaming agent,citric acid is an admixture,and the prepared basic magnesium sulfate foamed cement(Basic magnesium sulfate foamed cement（BMSFC for short）is used to enhance overall performance.The specific research content is as follows:（1）During the preparation of MgCO₃·3H₂O whiskers,the effects of reaction time,dropping rate,stirring rate,and reaction temperature on crystal growth and morphological size were investigated.The research results show that the reaction time has a great influence on the morphology of the product.When the reaction time is about 85 minutes,the obtained MgCO₃·3H₂O crystals have better smoothness and integrity;when the dropping rate of the precipitation agent is 24ml/min,MgCO₃·3H₂O The crystal has good crystallinity and uniform size.When the stirring rate is 300～400r/min,the particles are uniform,the probability of crystal collision is not high,and the crystal growth develops well;when the reaction temperature is 40～50℃,the crystal growth of MgCO₃·3H₂O is fast,the purity is good,and the aspect ratio is high..By optimizing the above crystallization conditions through a single factor experiment,MgCO₃·3H₂O whiskers with a length of 50-80μm,an aspect ratio of 40-100 and a yield of 85%can be prepared.When the calcination temperature is 600°C and the heating rate is 5°C/min,the morphology of the precursor MgCO₃·3H₂O whiskers is not significantly damaged,and the length of the prepared MgO whiskers is 30-60μm.（2）The experiment explored the influence of CSW,MHSH-512,MCH,and MgO four kinds of inorganic whiskers on the performance of BMSFC.The study found that when the CSW content was 2%,the 3d,7d,28d compressive resistance increased by 37.5%,38.2%and 32.7%,respectively,and the best flexural strength could reach 1.48MPa.As the dosage increases,the softening coefficient of BMSFC gradually decreases,and the thermal conductivity gradually increases;MHSH-512 has a significant effect on enhancing the mechanical properties of BMSFC.With the increase of the content of MHSH-512,the density of BMSFC increased from 466.47kg/m³to526.04kg/m³.The 28d compressive and flexural strength reached its peak at6%,respectively,8.0MPa and 1.7MPa.This is because MHSH-512 can induce early hydration and promote the formation of more 5.1.7 phases.The water absorption and softening coefficient of BMSFC are obviously due to the blank group due to the introduction of MHSH-512,but the thermal insulation is slightly reduced;MCH has no obvious effect on the early compressive and flexural strength of BMSFC.The 28d compressive strength is 6 when the MCH content is 6%Increased by 24.9%,and the flexural strength was the highest when the dosage was 2%.With the increase of MCH content,the water absorption and heat preservation performance of the material decrease;the participation of MgO whiskers in the hydration process leads to the enhancement of the early flexural strength and later compressive strength of BMSFC.It also improves the water absorption and softening coefficient of BMSFC.However,due to the high thermal conductivity of MgO,the thermal insulation performance has dropped sharply.