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活化生土基低碳节能村镇建筑材料研究

Research on the Low Carbon Emission and Energy Saving Material by Using Activated Clay Matrix for Rural Buildings

【作者】 谭晓倩

【导师】 王立久;

【作者基本信息】 大连理工大学 , 市政工程, 2011, 博士

【摘要】 村镇现有的建筑材料普遍存在生产制备及使用高能耗的弊端。要想解决这一现状,就需要充分利用农村生态资源和工业废弃物,结合被动式节能优势,制备出低碳节能的建筑材料及其制品。本文在常温常压条件下,以碱激发的方式对生土和矿渣进行活化处理作为基材,通过向基材中分别掺加相变材料、农作物秸秆、发泡等方式制备了储能相变复合建筑材料、干压及湿脱模节能小砌块、多孔屋面被动蒸发降温材料。并对材料的力学性能、耐久性能、热工以及节能性能进行了实验研究与理论推导。在常温常压条件下,以工业水玻璃为主要激发剂,对生土与矿渣进行了无有毒有害气体放出的激发活化,制备出28d胶砂抗压强度达45MPa的活化生土基材料。该材料改变了传统农村生土建筑材料强度低、脆性大、耐水耐久性差的缺点。其耐水软化系数高达0.837;浸酸强度损失率仅为9.8%;可抵抗150次以上冻融循环;耐高温;具有优异的抗氯离子渗透性能。压汞法表明其孔隙率仅为6.76%。标准养护条件对该材料的强度发展最为有利,且生土的CaO/SiO2越大,活性指数越大,配制出的基材强度越高。但该材料干缩较严重。通过XRD、SEM、IR、DTA、NH4+容量交换分析表明,活化生土基材生成产物主要为水化硅酸钙、水化铝酸钙及沸石类产物,未发现氢氧化钙晶体。并用MS软件对生成产物进行三维生成,表明生成产物具有致密的空间三维网络键接结构,沸石产物结构中形成很多空腔,形成了特定的孔道结构。以工业石蜡、膨胀珍珠岩为储能载体,通过硅酸钙外壳进行封装后掺加到活化的生土基材中,制备了储能相变复合建筑材料。其干表观密度为1674kg/m3;28d抗压强度可达23MPa;耐水软化系数为0.81。同时具有很好的热工性能:导热系数0.35W/(m·K),比热容为1.58W·h/kg·K,蓄热系数为15.52W/(m2·K),热阻为1.67(m2·K)/W,热惰性指标为25.91,热扩散系数为0.132×10-3m2/s。对该材料进行了一维和三维条件下的温度和时间响应关系研究,结果表明在外界温度升高或降低时,该材料相对于传统材料温度变化小,波动平缓,且在相变点附近出现明显的恒温阶段,升温及降温总时间大大延长。节能分析表明,该材料的使用可明显降低有效热量,节能效率达55.6%。为改善相变板冬季使用时的热导率,掺加石墨作为导热改进剂,其导热效果明显改善。设计了一套相变建筑材料-太阳能蓄电系统-聚砜高分子膜-铜网电阻系统,利用太阳能转化成电能,通过电阻产生热量再源源不断传递给相变材料以维持室内温度。聚砜膜在防止相变材料渗露的同时还由于其低的传热性防止了热量的外泄,真正实现了采暖零能耗。向活化生土基材中掺加稻草秸秆,利用自制钢模具,在加压情况下制备出活化生土基稻草秸秆空心砌块。其表观密度为1655kg/m3;28d抗压强度高达25MPa;耐水软化系数0.80。掺加石蜡珍珠岩,制备出活化生土基储能相变空心砌块。其干表观密度降至1101kg/m3,28d抗压强度为9.6MPa。测试了活化生土基稻草秸秆空心砌块、石蜡珍珠岩填孔夹心稻草砌块、及相变砌块的热工性能。结果表明相变材料夹心处理后热阻最高,传热系数最小,保温隔热能力最好。考虑农民可自助生产且结合农村建筑特点,向活化生土基材中掺加大量稻草秸杆与向日葵瓤,利用设计的小砌块湿脱模模具(尺寸为240mm×115mm×115mm,三孔60mm×60mm×60mm)制备了湿脱模(添料后10min脱模)小砌块,用于围护结构或夏季屋顶通风,根据风压原理计算其孔洞内风压为584.5Pa,平均气流速度2.15m/s。向活化生土基材中掺入发泡剂进行发泡,掺入聚丙烯纤维进行增强制备了多孔屋面材料,用于收集雨水,从而发挥被动蒸发降温功能。其干表观密度为453kg/m3,28d抗压强度可达3.3MPa。单位体积吸水质量为376kg,可经受100次以上干湿循环。聚丙烯纤维的掺加起到了承受一定的外荷及假延性,降低裂缝尖端的应力强度因子,缓和应力集中程度,从而提高抗折强度的功能。采用SEM、压汞法对致密、适中、疏松孔结构进行了研究。结果表明孔结构为孔壁上有许多小洞的连通孔,孔隙率分别为51.5%、57.3%、60.3%,孔径范围分别为20um、40um、90um。结合分形理论对孔结构进行定性评价:孔的分形维数分别为2.97、2.88、2.78。且随分形维数增大,单位体积的吸水质量增大。用气候箱测试多孔材料的被动蒸发降温性能,结果表明用一层30mm的活化生土基多孔材料覆盖在屋顶时,其室内最大降温幅度可达3℃,温度延迟时间大大延长,通过屋顶的热流显著降低。经100次干湿循环后强度明显降低,但对其吸水及蒸发性能影响不是特别显著。当干表观密度为453kg/m3时,其导热系数为0.116W/(m·K),蓄热系数为3.84W/(m2·K),热阻为5.63(m2·K)/W,比热为1.08 W·h/kg·K,热惰性指标为21.62,热扩散系数为0.237×10-3 m2/s。表明该材料即使不发挥被动蒸发降温功能,也可起到保温隔热材料的功效。建立了包含孔分形维数的多孔体水分的热湿迁移数学模型,改善了原模型中孔粗糙度难以测量的弊端。

【Abstract】 High energy consumption is always an urgent problem during the preparation and applications of building materials in rural. In order to change this condition, resource ecology, industrial waste as well as passive energy saving technology must be utilized to prepare energy saving building materials. A new form of cement was produced by mixing clay, slag and water-glass at room temperature without baking as matrix. PCM building material, dry pressure and wet demould blocks and porous roof material for passive evaporative cooling had been gained by mixed with PCM, straw and foam agent in clay matrix respectively. Mechanical properties, lasting qualities, thermal characteristics and energy conservation properties had been studied and deduced by theory.A new form of cement was produced by mixing clay, slag with prepared water-glass activator during stirring. The preparation of the material is quite different from the normal one, which is produced just at room temperature and without poisonous gas emission. The fabrication of this energy-saving material can be favorable for lowering carbon emission by using recycled industrial wastes and resource ecology in countryside. Compressive strength of 45.3MPa, water resistant coefficient of 0.837, loss factor acid etch of 9.8%, cycle of freezing and thawing for more than 150, high ability of resistant to elevated temperatures and chloride ion, the porosity of 6.76% by mercury intrusion method can be achieved after 28 days curing. Standard curing is benefit for the mechanical properties. The more CaO/SiO2 and activity coefficient, the more strength is. The hydration products were C-S-H with less Ca(OH)2, calcium aluminum and zeolite, which were characterized by XRD, SEM, IR, DTA, NH4+ capacity conversion measurements. Three dimension products model were generated by Materials Studio soft. The results showed that all the products were three dimension reticulated bond jointing structure and there were some cavities in zeolite.A new type of composite for construction named LPM was prepared by mixing clay,slag, alkaline activated agent and a suitable amount of expand perlite impregnated with paraffin as form-stable phase change and latent heat energy storage material which encapsulated with calcium silicate. The dry density of 1674kg/m3, compressive strength of 23MPa, water resistant coefficient of 0.81, thermal coefficient of 0.35 W/(m·K),specific heat of 1.58 W·h/kg-K, thermal storage coefficient of 15.52W/(m2·K), thermal resistance of 1.67 (m2·K)/W, thermal inertia index of 25.91, thermal diffusivity of 0.132×10-3m2/s had been achieved. The variation of temperature with time of LPM and the corresponding traditional material used as reference material were determined. The results indicated that when the environment temperature changed, the temperature of the LPM changed more gently, the temperature fluctuation was less and the peak temperature occurs later than the corresponding traditional material. The energy conservation efficiency can be reach up to 55.6%. In order to improve the coefficient of thermal conductivity of LPM used in winter, graphite had been filling into the clay matrix materials. The zero energy consumption system of PCM building material-polysulfone film-copper net wire-solar energy accumulator had been designed successfully. The solar energy had been converted into electric for produce heat power through copper net wire and was delivered to PCM. The room temperature can be under control in frigidity winter night. The polysulfone film can not only prevent the leakage of PCM but also countercheck the thermal power loss.Two kinds of building blocks had been prepared by putting straw and PCM respectively into the activated clay matrix under the condition of load. The straw building block with the properties of dry density of 1655kg/m3, compressive strength of 25MPa, water resistant coefficient of 0.80 had been prepared. The second one was PCM block with dry density of 1101 kg/m3 and compressive strength of 9.6 MPa. The third one was a sandwich structure with PCM in holes. Heat flow test results showed that the third one was the best with the highest heat resistance, small heat transfer coefficient and the excellent insulation properties. In the same time, a wet demould(demould after 10 minutes) building block had been prepared by a novel designing model and straw, helianthus annuus pith blending into the clay matrix. The size was 240mm×115mm×115mm, pore size was 60mmx60mmx60mm. It can be used for exterior-protected construction and roofs ventilate applications. The calculation of pressure was 584.5Pa and average speed of gas flow through the pores was 2.15m/s.A light weight porous material with suitable strength was developed as a roof material. This material was prepared by choosing slag and clay as raw material, activated by alkali agent and injected with foams. The gelled matrix was then strengthened by adding polypropylene fibers. This unique designed material can detain a significant amount of rainwater and be applied for passive evaporative cooling roof systems. Finally, the porous material with compress strength of 3.3kg/m3, dry density of 453kg/m3, water absorption of 376kg/m3, dry and wet cycle for more than 100 was gained when the W/C was 0.2. The functions of polypropylene can improve the flexural strength by decreasing the stress intensity factor of crack tip and release the stress concentration. The compact pore structure, moderate pore structure and loose pore structure had been studied by SEM and mercury intrusion method. The results showed that the pores structure were intercommunicating pores and the porosity were 51.5%,57.3% and 60.3%, the pore sizes were 20um,40um and 90um。The fractal geometry was applied to describe the pore structures of roof materials with different ingredient ratios. The fractal dimension was 2.97,2.88 and 2.78, which were discovered related to the evaporation cooling performance of the roofs. Larger fractal dimension materials show better water absorption ability. Variations of room temperature and heat flux transfer across porous material roof slab have been measured. The results showed that roof covered with porous material of 30mm can satisfactorily lower room temperature for about 3℃and reduce heat flux, as compared with OPC (ordinary Portland cement) roof layer simply. Covering porous material layer as roof surface can create a more effective cooling system by utilizing its water absorption and evaporation capability during canicule. Thermal coefficient of 0.116W/(m·K), specific heat of 1.08W·h/kg·K, thermal storage coefficient of 3.84W/(m2-K), thermal resistance of 5.63 (m2·K)/W, thermal inertia index of 21.62, thermal diffusivity of 0.237×10-3m2/s had been achieved when the dry density was 453kg/m3. A new mathematics model about the evaporation speed of water in porous materials had been builted combinig with fractal dimension of pore structure.

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