低碱度缓释型多孔植生水泥混凝土的水化特性及结构研究

Porous planting concrete is a kind of functional building materials suitable for plant growth. It is prepared with coarse aggregates wrapped by cement paste to create porous structure. It is mainly used for slope protection of highway, waterstead and dam and afforesting project. There are some main problems in porous planting concrete of high alkalinity, low porosity and low strength, which is not conducive to the growth of plants. Nutrients for plant growth is not provided by porous planting concrete itself. Fertilizer efficiency from soil surface is kept for a short time. Sulpho-aluminate cement and acid admixture with high active are used to make higher strength concrete and lower alkalinity. The fertilizer will be adsorbed in porosity of hardening cement paste during hydrating by mixing cement ,poros materials with fertilizer, and then released sustainedly to plants. Pore structure of concrete was improved through designing particle size gradations of coarse aggregates. The main research contents include: the influence of acid admixture on hydration process of sulpho-aluminate cement; the changing regulation and controlling mechanism of alkalinity during hydrating and hardening; the influence of the fertilizer components on the hydration process of cement and sustained-release regulation and effectiveness of composition and structure of hardening cement paste on fertilizer; the controlling of composition, aggregate gradation design and pore structure of concrete;compatibility and appraising of planting concrete with plant growth.

植生混凝土是在粗集料表面包覆一层水泥浆粘结而成具有多孔结构并适合植物生长的功能建筑材料，主要用于路基、河床、堤坝等工程的固土护坡，并具有绿化美化作用。其存在的主要问题是水泥混凝土的碱度高、孔隙率低、强度低，不利于植物生长。而且水泥混凝土本身不能提供肥料养分，植物生长所需肥料主要从初期表面覆肥获得，肥效保持时间短。本项目利用快硬早强硫铝酸盐水泥，并掺入高活性酸性掺合料，进一步提高混凝土强度和降低水泥碱度。通过将水泥、多孔材料与肥料复合，在水泥水化过程中使肥料吸附于硬化水泥浆体孔隙内再缓释于植物根系。通过粗集料粒径级配设计，改善混凝土孔结构。主要研究内容：酸性掺合料对硫铝酸盐水泥水化过程的影响规律；水泥水化硬化过程中液相碱度的变化规律及调控；肥料组分对水泥水化过程的影响及硬化浆体组成和结构对肥料缓释机制的影响及时效性；混凝土组成与集料级配设计及孔结构调控；植生混凝土与植物生长的适应性及评价。

植生混凝土是由水泥、粗集料和水等拌合而成的具有多孔结构和生物相容性的功能建筑材料，主要用于路基、河床、堤坝等工程的固土护坡，并具有绿化美化作用。其存在的主要问题是水泥混凝土的碱度高、孔隙率低、强度低，不利于植物生长。而且水泥混凝土本身不能提供肥料养分，植物生长所需肥料主要从初期表面覆肥获得，肥效保持时间短。本项目利用快硬早强型硫铝酸盐水泥，并掺入高活性酸性掺合料，进一步提高混凝土强度和降低水泥碱度。通过将水泥、多孔材料与肥料复合，在水泥水化过程中使肥料吸附于硬化水泥浆体孔隙内再缓释于植物根系。通过粗集料粒径级配设计，改善混凝土孔结构。主要获得以下成果：粉煤灰和矿渣改善了硫铝酸盐水泥的粒径分布，而且越接近Fuller分布在相同的水胶比条件下，水泥浆体的结构越密实，水泥水化初期的强度就越高。沸石可有效的提高硫铝酸盐水泥硬化浆体的吸水性能、孔隙率。因为沸石与水泥水化产生的CH反应生成凝胶，硫铝酸盐水泥硬化浆体孔溶液pH降低至10.4。尿素及磷酸氢二铵的加入均使硫铝酸盐水泥凝结变慢，流动度增大，归因于二者严重阻碍了硫铝酸盐水泥的水化及钙矾石的形成；掺加肥料后的硫铝酸盐水泥硬化浆体均可以产生肥效释放的效果，掺量与累积释放率成正比，氮元素的累积释放率达到22.6%-95.4%；以硫铝酸盐水泥制备的植生混凝土具有良好的吸水率和保水保肥性，在-5-18℃的冻融循环制度下植生混凝土可以承受的冻融循环次数为70-80次。