The Study And Preparation Of Load-bearing Composite Wallboard Based On Ultra-light, High Insulating Portland Cement Aerated Concrete

In need of building energy saving, building industrialization and building fire protection, this paper aims to develop a large-scale composite wallboard with flexible design concept and combining high thermal insulation, A-class fire protection, enough load-bearing function and excellent durability. This study and design concept should be able to lay a solid foundation for china’s construction engineering modernization and higher construction energy saving.Beginning from the raw materials analyzing, selection and manufacture, the paper firstly develops an optimal mix proportion of Ultra-light aerated concrete(ULAC), then, makes a deep research on the configuration process, structural and pore structure type characterization, finding that the structure forming process of ULAC should be divided into four stages: mix-stirring and pouring--- foaming molding--- meta-stable re-consolidation--- hardening consolidation; and exploring the pulverization mechanism of ULAC; establishing a pore structure model for making ULAC. Finally, through a mathematical analysis and finite element analysis, a new process of preparation and production equipment have be developed, a new type of composite bearing wall panels with density of ULAC between 100kg/m3~ 300 kg/m3, pore size adjustable and completely using Portland cement and large addition of fly ash are successfully prepared. The specific study content includes as followings:In the field of studying raw materials for ULAC, a foam-stabilizing and rapid-setting emulsion(FsRsE-A)was produced through saponification reaction with potassium hydroxide(KOH), stearic acid(C18H36O2) as the main materials. This emulsion has showed the characteristics of simple manufacturing process, low production cost, easily dispersed in cement paste, quick-setting and good foam stabilizing effect.And, with Xanthan gum as main component, a small amount of polymer as auxiliary material, a complex thickener B was developed, which can effectively increase the strength of the foam and the liquid slurry viscosity. The complex thickener B and the FsRsE-A both have good compatibility and excellent high temperature stability.Changing the traditional ULAC technology which used to utilize rapid-hardening cement as cementing materials, this study makes use completely of Portland cement as cementing materials, high proportional fly ash as assistant addition, FsRsE-A as foam stabilizer and accelerator, complex thickener B as thickening stabilizer, polypropylene fiber as reinforcing material, 27.5% concentration of hydrogen peroxide(H2O2) as gas forming agent, a systematic research targeting on ULAC with 250 kg/m3 dry density and actual production condition(foaming- height greater than 30cm) was carried out using different raw materials proportion for the ULAC producing process and performance, searching the mature production technique and the optimum performance.In the field of studying manufacture process and the product structure, the raw materials mix proportion for different densities of ULAC, foaming technology and structure characterization method have been acquired. This paper has firstly found that the gas pore feature of ULAC transits gradually from spheroids to horned polyhedron while dry density from lightweight to super-lightweight(dry density <300 kg/m3) for the reason of porosity to exceed the maximum of spheroids shape pore on condition that the pore structure is basically intact. So, a new model for the ULAC pore structure has been presented.With different content of cellulose ether and hydrogen peroxide and in the premise of other raw materials as the same, different densities of ULAC are prepared. Using SEM, EDS, stereo microscopy, and other means, the gas pore morphology and their wall structure, hydration products are all analyzed. When cellulose ether content was greater than a certain value and the size of gas pore was smaller than a certain scale, ULAC would pulverize, the strength would decrease. The reasons had been explained; a technology of controlling gas pore size had been advanced.Using computer simulations and finite element analysis, the loading and deformation rule in a vertical load and a vertical deck load of ULAC Load-bearing composite wallboard(LBCW) have been studied,demonstrating that the proposing design idea and parameters for LBCW were feasible.Based on the above studies, the production technology of a LBCW with high-strength reinforced cement mortar as load-bearing structure was designed, the manufacturing equipments were prepared, the first batch of LBCW were trial-manufactured and their performances were tested. The results have showed that these panels were super-lightweight, high-strength, of good function in out–plane bending resistance, axial compressive strength and shock resistance, which could completely meet the requirement of load-bearing outer wall of building; Also, they possessed good heat insulation performance and could well satisfied the energy-saving requirement of different climate area only with a certain thickness.