| Gypsum as a green building material has excellent characteristics,but the poor water resistance of gypsum greatly limits the scope of use of gypsum.How to change the durability of gypsum in water has become an urgent problem.In order to improve the compactness of gypsum,reduce the porosity and improve the water resistance of gypsum specimen,cementing materials are used to add to gypsum.And the use of organic materials to isolate gypsum from water is a few more direct methods.The purpose of this paper is to study the change of performance indexes of gypsum products modified by aluminate cement.And adding other mineral admixtures or organic admixtures on the basis of cement modification to carry on the inorganic modification and the organic-inorganic compound modification to the building gypsum.In the experiment,building gypsum was used as the main material,in which various inorganic and organic admixtures were added.In order to obtain the best content of different admixtures,the gypsum composite specimens were prepared with different dosage of admixtures as variables.With CA-60 aluminate cement for building gypsum modified test,the test results show that when the cement content of aluminate cement is 25%,the compressive strength of the specimen is 6.25 MPa and the bending strength is 2.30 MPa.And it is the maximum value of each amount of content,than pure gypsum specimen 3.70 MPa compressive strength increased by 69%,than pure gypsum specimen the flexural strength of 2.30 MPa increased by43.7%;The saturated compressive strength of the composite specimen was 3.35 MPa,and the compressive strength of the saturated water was 123% higher than that of the pure gypsum,and the softening coefficient increased by 0.13 compared with that of the pure gypsum.On the basis of cement-gypsum composite,the inorganic doped fly ash and lime are added respectively.The density of the composite spcimen is greatly increased by fly ash.The optimum content of fly ash was 8%,the compressive strength value of 6.15 MPa,than pure gypsum increases the compressive strength of 2.45 MPa;And flexural strength is 2.40 MPa,than pure gypsum specimen improved the flexural strength value of 0.8 MPa;The compressive strength of saturated water increased by 2.25 MPa compared with that of pure gypsum.The softening coefficient of the sample is 0.61,which is a factor of 0.2 from the softening of pure gypsum.The optimum content of the lime was 15%,and the compressive strength of the composite specimen reached 6.65 MPa,which was 2.95 MPa higher than the compressive strength of the pure gypsum.The flexural strength was 2.70 MPa,and the flexural strength of the pure gypsum specimen increased by 1.1MPa.The saturated compressive strength is 4.4 MPA,which is 2.9MPa higher than that of pure gypsum.The softening coefficient is 0.66,which is 0.25 higher than that of pure gypsum.On the basis of cement-gypsum composite,the composite gypsum was modified by adding organic and superplasticizer respectively.The optimum dosage of superplasticizer is0.45%.The compressive strength of the composite specimen is 9 MPA,which is 5.3MPa higher than that of plain gypsum.The flexural strength is 4.35 MPa,which is 2.75 MPa higher than that of plain gypsum.The saturated compressive strength is 4.95 MPA,which is 3.55 MPA higher than that of plain gypsum.The softening coefficient is 0.55,which is 0.11 higher than that of plain gypsum.The gypsum is modified with epoxy resin.The results show that epoxy resin is not suitable for the modification of gypsum.After a series of experimental studies,it can be concluded that: The suitable amount of aluminate cement and mineral admixtures can,to a certain extent,improve water resistance of gypsum composite,while incorporating the superplasticizer further improves the mechanical strength of the gypsum materials.The modified composite gypsum material ismore widely used and has better performance.And the reuse of resources has greatly increased,reducing original resources and making some contribution to the environment protection. |
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