Research On Preparation Of Porous Magnesium Sulfate Concrete By Using Millimeter-size Spherical Superabsorbent Polymers

With the continuous increase of building energy consumption,in order to implement the sustainable building energy system,various national policies have been unveiled one after another,and the research and development of new energy-saving building materials has become an urgent task.Lightweight porous concrete such as foam concrete and aerated concrete has the advantages of light weight and low thermal conductivity,which not only can achieve the traditional wall envelope function,but also can adjust the temperature difference between inside and outside so as to save temperature control and electricity and conform to sustainable development.However,in the process of preparation and curing,shrinkage and water absorption tend to be large,and the pore structure is difficult to control,which affects the quality of the product.In this paper,focusing on shortcomings of lightweight porous concrete with large shrinkage and uncontrollable pore structure,we prepared various bulk densities of porous concretes by using millimeter-size superabsorbent polymer(SAP)with spherical shape and controllable particle size and magnesium oxysulfide cement with excellent fire resistance.At the same time,we used the experience of the pore-forming principle and internal curing effect of SAP in Portland cement concrete.Firstly,the key technology for the preparation of porous magnesia oxysulfate concrete was solved.The water absorption of SAP under different solutions is studied.By comparing the influence of different time of pre-soaked SAP on the fluidity of magnesium oxysulfate cement,we found that SAP with pre-absorbed water for 13min had the least effect on the workability of the paste.Secondly,by adjusting the w/c ratio and adding fiber,the consistency was controlled to inhibit the rise of SAP in the paste,and the variation coefficient of 28d compressive strength was better used to characterize the uniformity of SAP distribution.Thirdly,the effects of SAP,polypropylene fiber,quartz sand and curing conditions on the physical and mechanical properties of porous magnesia oxysulfate concrete were studied,and the phase composition and microstructure were analyzed.Porous magnesium oxysulfate concretes with bulk density of 1120.3~2201.2 kg/m~3,28d compressive strength of 9.0~92.3MPa and 28d flexural strength of 4.0~20.2 MPa were prepared.The porosity and water absorption of the prepared porous concrete increased with the increase of SAP content,but decreased with the increase of quartz sand.The 28d compressive strength and flexural strength decreased with the SAP increase,respectively decreased and increased with the increase of quartz sand.The softening coefficient decreased with the increase of SAP content,and slightly increased with the increase of quartz sand.The expansion rate of porous magnesium oxysulfate concrete increased with the SAP increase in the early stage and decreased in the later stage.And the incorporation of quartz sand can reduce the expansion rate by 1/2.The environment humidity should be 40~54%RH,and the temperature is25~35?,which was conducive to the improvement of strength.Finally,the building energy consumption of different wall material simulation laboratories was analyzed by using Ecotect Analysis software.The results show that the thermal conductivity decreased rapidly to 0.3013 W/(m·K)as the SAP content increased and the bulk density decreased.The energy consumption of 1100 kg/m~3porous magnesium oxysulfide concrete is lower than 1700 kg/m~3solid clay brick,which is equivalent to that of 700 kg/m~3aerated concrete block.