Mix Design And Performance Study Of Glass Fiber Reinforced Concrete For Prefabricated Cabin

The modular construction of smart substation has become the main direction of the future development of the State Grid.The main mode of modular construction is to install power equipment in the prefabricated cabin and transport it to the site as a whole.Compared with traditional steel structure cabins,the glass fiber reinforced concrete(GRC)have the advantages of small proportion,high strength,good toughness,excellent fire resistance,strong ability of temperature and humidity change and good plasticity.It is of great significance for developing new high performance prefabricated cabins,carrying out factory production and realizing the construction of intelligent substations.This paper mainly studies the selection and optimization criteria of raw materials for GRC used in prefabricated cabins,the comparison of mechanical properties and test methods,the optimization design of mix ratio and preparation process,and the properties of GRC in Portland cement and Sulphoaluminate cement systems,as well as the preparation and properties of GRC with large fiber content.The conclusions are as follows:(1)Through comparative analysis of domestic and foreign literature and a large number of experimental studies,the optimum selection and optimization criteria of GRC raw materials are determined: to determine the cementitious material system by forming temperature or service environment;to select fine aggregate with silica content more than 80%,particle size less than 3 mm continuous gradation of clean river sand;to select alkali-resistant glass fiber with zirconia content more than 16%,and cluster short-cut fibers with hard texture.(2)Based on the comprehensive consideration of the performance,bleeding and mechanical properties of GRC mixtures,the mix ratio parameters and the optimum range of GRC are determined.Secondly,the actual effects of the two preparation processes were designed and compared,and the optimal preparation process was determined.The results show that the optimum range of water-binder ratio is 0.30-0.38,the optimum range of sand-binder ratio is 1:0.5-1:1.2,and the optimum content of glass fiber is 2%.The wet-dry process should be selected when preparing GRC.(3)The research on the design,preparation and hardening of Portland cement-based GRC shows that the flexural strength of GRC increases first and then decreases with the increase of water-cement ratio,decreases with the decrease of mortar ratio,and increases with the increase of fiber content.The 28-day compressive strength of GRC is 43.0-60.0 MPa,and the flexural strength is 10.6-15.0 MPa,which meet the mechanical strength requirements of GRC in prefabricated cabins.(4)The mechanical strength of Sulphoaluminate cement-based GRC is basically the same as that of Portland cement-based GRC.The alkalinity of Sulphoaluminate cement matrix is low,and the probability of corrosion and embrittlement of glass fibers caused by hydration products is low,the long-term flexural strength of prepared GRC is stable.The 28-day compressive strength is 35.0-50.0 Mpa,and the flexural strength is 12.0-15.0 Mpa,which meets the mechanical strength requirements of GRC for prefabricated cabins.(5)The influence of fibers on the properties of GRC mixtures was analyzed,and a synergistic method of drag reduction of spherical fly ash beads and viscosity reduction and dispersion of polycarboxylic acid water reducer was proposed.The key technical problems of low fluidity and easy agglomeration of GRC composites with large amount of fibers(volume content more than 3.0%)were overcome,and GRC with excellent properties were successfully prepared.The optimum content of microspheres is 30%,the maximum content of fibers can reach 4.0% or even 5.0%,and the flexural strength can be increased by 20%.