Study On Preparation And Fiber Reinforcement Of Geopolymer Concrete Based On Fly Ash And Slag

Ordinary portland cement（OPC）as the main cementitious material of concrete in the field of construction,which has been irreplaceable for a long time,however,the problems of high energy consumption and heavy pollution in the production process have not been properly solved.Therefore,it is urgent to seek or develop a green and energy-saving environmental protection material with cement characteristics.Geopolymer concrete（GC）is a new type of green building material without cement.The amount of CO₂ emitted by GC cementitious materials in the production process is far less than that of OPC.,there are advantages of high strength,short setting time,strong durability and corrosion resistance,wide source of raw materials and low cost for the geopolymer concrete.Therefore,it is aof great significance to study the preparation and mechanical properties of geopolymer concrete based on fly ash and slag,the following works and conclusions are done in this paper:（1）Design of mix propertions and basic mechanical properties.Fly ash（FA）and granulated blast furnace slag（GGBS）were used to prepared the geopolymer concrete,which was activated by a combination of sodium silicate and sodium hydroxide solutions and cured in ambient condition.,containing various ratio of fly ash and slag,sodium silicate modulus and the content of sodium silicate,and its macro mechanical properties were studied.It was shown that the best mechanical properties of specimen were achieved when the sodium silicate modulus was 1.2,the ratio of fly ash to slag was 4:6 and the sodium silicate solution content was 25%.Meanwhile,the relationship equation of compressive and splitting tensile strength of fly ash-slag geopolymer concrete is established.（2）Microscopic mechanism.The microstructure of at different ages and ratios was investigated by means of microscopic analysis.The study showed that:crystals such as calcium alumina were mainly observed in PCC,while the SEM microstructure of GC mainly consisted of non-crystalline phases;EDS showed that the abundant silicon content in the reaction system could make GC obtain higher strength values;XRD analysis found that the coexistence of C-S-H,C-A-S-H and N-A-S-H gels in the reaction system made GC obtain higher strength;The absorption peaks of fly ash and slag were found to be significantly different from GC at 1300-1500 cm^-1 based on FT-IR test.（3）Analysis of fiber modification and reinfrocement mechanism.Based on the properties of steel fibers and polypropylene fibers,the effects of fiber type,volume admixture and arrangement form on the mechanical properties of fiber-reinforced geopolymer concrete（GC-P,GC-S,GC-LS,GC-FR,GC-LFR）were investigated.It was found that the mixed fibers improved the mechanical properties more significantly compared with the single-fiber specimens;however,the negative mixing effect occurred when the fiber admixture was too much.In addition,the strengthening mechanism of the fibers was analyzed based on the fairlure modes and microscopic morphology of specimens,and the stress,strain and displacement of GC-LFR were analysised by using the theory of laminar elastic system.