| Along with the in-depth push of construction energy conservation in our country, itsdesign standard system was established and some specific requirements about the heattransfer coefficient and thermal inertia index of external wall has been presented. In all newwall materials, aerated concrete is the only one material that could be satisfied with theenergy saving standard, but it has still some problems, such as lower strength, biggershrinkage, lower penetration resistance, etc. So, it is the urgent demand to research anddevelop the new practical wall materials which are good in thermal insulation effect andvarious technical performances, easy to use, and can be used for exterior load-bearing wall.The heat-retaining sandwich composite wall not only has the common characteristics ofexterior insulation systems, but also can protect the insulting materials and the majorstructure, improve the indoor thermal environment, suitable for the wall structures whichhave requirements in load-bearing and performance on thermal insulation, having hugetechnical economic advantages and vast future. Therefore, it has become one of the researchhot spot in construction energy saving.However, the present study and development of insulation sandwich composite wall aremainly depended on the actual experiences and existing production process in materialselection, structure design, products development. They have two obvious problems as thefollowing: firstly, its structural layer in most cases used ordinary concrete or lightweightconcrete, and arranged with steel reinforcement network and transverse steel connector forreinforcing, these all enhance greatly the self-weight and lead to the structure complicated,and go against reducing the coefficient of thermal conductivity, thermal resistance andthermal bridge effect. Previous studies pointed out that the transverse steel connector bearslittle of stress under loading and the connection arrange has little effect on the compressivestrength and elasticity modulus. Secondly, the organic materials of the insulation layer havebad performance of fire-proofing, and easy to produce dew inside of the wall. There were somany lessons before.In this thesis, based on the analysis of synthesis about various composite wall studies, anaerated all-light-weight ceramsite concrete (ALWCC) was selected for the structural layerand a foam cement mortar (FCM) was used as the insulation layer, a systematic study of theload-bearing, heat-retaining sandwich composite wall (LHSCW)from theoretically mechanicssimulation study, the preparation of the materials of structure and insulation, to the design of the composite wall structure was carried out carefully.First of all, aiming at the requirement of residential construction energy conservation ofwarm winter and hot summer area, the sandwich composite wall with the above materials anda parallel plate style structure was studied using the finite element analysis for the mechanicalperformance, a series of basic regulation of stress distribution under vertical loading and windloading were proposed. The following rules were found: the vertical compressive stress wasundertaken majorly by the structure layer; in the two corner of the wall bottom, thecompressive stress obviously increase; but in the slightly below the two sides of middle wall,the stress were comparatively lower, the tangential contact stress between two layers was alittle; under wind loading, the normal stress of the interface was the greatest respectively atthe parts of about1/4and3/4of wall height and increases with the thickening and rising ofthe wall, etc. The various mechanical performance data in different wide/height ratio wereobtained and it is proved that the load-bearing composite wall without connector could berealized. When the wall was150mm thick, insulation layer was40mm thick, the compositewall could support10MPa loading. In this case, the compression strength of ALWCC shouldbe more then13.6MPa, and that of FCM should be more than0.19MPa, the shear strengthbetween structure layer and insulation layer should be greater than3.89KN/m~2, bondingstrength must be greater than1.45KN/m~2, and so on.In order to develop the ALWCC with load bearing as well as some heat retainingperformance using for the structure layer of sandwich composite wall, air-entrainingtechnology was taken, an aerated ALWCC which density is1110kg/m3, compressive strengthof28d is18.8MPa, coefficient of thermal conductivity is0.38W/(m K) was acquired. Theeffect of rosin acid sodium air-entraining agent, poly-carboxylic acid air-entraining agent,lauryl air entraining agent to ALWCC has systematically been studied for the density, porosity,pore distribution and water absorption of the concrete. It was discovered that air entrainingeffect of poly-carboxylic acid and lauryl air-entraining agent are the better and soleair-entraining agent is better than composite one. It has been put forward that the ALWCCwith high strength, light weight and small thermal conductivity can be made by usingproperly air entraining agent.Through the experiments, then, on the effects of water-cement ratio, fly ash dosage,foaming agent types and dosage on the performance of FCM and using the animal proteintype foaming agent, the foam insulation mortar which thermal conductivity was0.18W/(m K), dry apparent density was620kg/m3, compressive strength was1.9MPa was obtained.Based on the study of above, the Author explored for the first time the new type sandwich composite wall with enough load-bearing, heat-retaining performance and allcement-based materials but without connection component. For overcoming the defect ofinsufficient cohesive force of the interface between structure layer and insulating layer, asystematic research on a tooth-type gomphoses interface design and its effect on the splittingtensile strength. It is found that reasonable tooth-type gomphoses interface structure couldsubstantially increase the interface cohesive force (splitting tensile strength≥1.2MPa,52.4%higher than that of parallel plate structure), and also raise compressive strength to a certainextent (about≥15%). So, the design thinking of no connection component is possible. Themeasurement and calculation of thermodynamic engineering performance showed that thisdesign of composite wall could satisfy not only the requirement of energy saving ofload-bearing external wall in warm winter and hot summer area, but also overcome the defectof cold or thermal bridge effects and avoid the inflammable and bad durability default. Thebasic technical parameters of acquired LHSCW are as following:ALWCC as structure layer,FCM as the insulation materials, with the tooth gomphoses interface structure of the toothwidth50-60mm, the distance of teeth150mm，insulation layer thickness40-50mm, the totalthickness of the wall150mm. The heat transfer coefficient k is about1.3W/(m~2k), thermalinertia index D is about4.15. This type of ALWCC can completely meet the requirements ofresidential building energy-saving of50%of exterior wall in hot summer and warm winterarea.This thesis has made also the elementary preparation process design for this new typecomposite wall. |
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