透水混凝土耐久性 

pervious_epa_demoPervious concrete pavement is a permeable pavement used to satisfy the need for both a pavement surface and stormwater management. Pervious concrete is created with narrowly graded coarse aggregate that is coated in a thin layer of cement paste or mortar. This allows for an interconnected pore structure through which water percolates. 除了设计水文(见 透水混凝土的水文设计), pervious concrete is structurally designed using normal design methods for pavements. The final key aspect to designing a pervious concrete pavement takes the durability into consideration.

混凝土的耐久性是抵抗风化作用的能力, chemical attack, and abrasion while maintaining desired engineering properties for the expected service life of the structure. 透水混凝土会被堵塞, which directly affects the hydrologic performance and may indirectly affect other aspects of durability, 如抗冻融性, 抗除冰盐结垢性, and sulfate resistance. 透水混凝土的耐磨性也值得关注, 特别是在使用扫雪机或有转弯交通的地方. Carbonation and corrosion resistance are not concerns with pervious concrete as it is neither recommended nor necessary to use reinforcing steel bars or welded wire reinforcement. 

Clogging

pervious_closeup如前所述,透水混凝土用于雨水管理. Water that flows onto the pavement flows through the pavement in an open-graded aggregate base. From there, the water either infiltrates into the subgrade or enters a conventional stormwater system. Any material that is picked up by the flowing water will also be taken into the concrete. 系统中颗粒的行为取决于孔隙系统, particle size, nature of the particles, and the flow rate. Mata (2008) found that sand particles are trapped near the surface of the pavement, but that smaller sized particles (silts and clays) are flushed through to the bottom of the system. Haselbach (2010) studied the effects of different types of clay and found that more expansive clays, such as bentonite, 也会在地表附近收集. It was also found that the clogging potential of the clays reduced drastically when the porosity of the concrete was raised from near 30 percent (typical maximum) to near 40 percent.

Sediments that collect inside the concrete can significantly reduce infiltration rates and increase the opportunity for the cement matrix to become saturated by trapping water within the concrete pore system. This may cause an increased risk for freeze-thaw damage, deicer scaling, or sulfate attack. Sediments that are trapped near the surface can be mostly extracted by vacuuming.

完全通过系统的沉积物不能被提取出来. Over time, these sediments will collect in the aggregate base and reduce the storage capacity and exfiltration rate. Knowledge of the surrounding soils is necessary for designing a pervious concrete pavement system and that knowledge can be used to avoid or mitigate infiltration of silts and clays. Barrier ribbons can be used to block soils from entering the sides of the pavement. 可用于处理低渗或膨胀土壤的选项(网球, Leming, and Akers 2004) may also help mitigate the effects of silty or clayey storm water.


Freeze-Thaw Resistance

The use of pervious concrete as a pavement began in warm climates where freeze-thaw damage was not a concern. Over time, use of pervious concrete pavements has moved into climates with increasingly severe freeze-thaw climates. This has raised significant concern among many groups, because of the high porosity of the concrete. See 透水混凝土与冻融 for a full review of the freeze-thaw and deicer scaling durability of pervious concrete pavements.

Sulfate Resistance



The presence of an open-graded aggregate base beneath a pervious concrete pavement is the best method to mitigate sulfate attack from high-sulfate soils and groundwaters. Additional isolation may be required along the edges of the pavement in the form of a barrier ribbon. The typical water-cementitious materials ratios used in pervious concrete fall between 0.27 and 0.34,这远低于建议的最大值0.非常严重的硫酸盐暴露为40. 如果由于高堵塞电位需要额外的保护, 耐硫酸盐水泥(ASTM C150类型I和V, C595 designated MS and HS, 或C1157型MS和HS)应使用.

Abrasion Resistance

Abrasion resistance of pervious concrete can be seen by observing how much and how quickly the surface aggregate particles ravel. This is of particular concern in locations with turning traffic or locations that use snow plows. The low w/cm and high porosity give pervious concrete an increased risk of surface drying before curing. If the surface dries out before developing strength, significant raveling will occur. This places a very high importance on streamlining the production process and ensuring the concrete is minimally exposed to ambient conditions. Research done by Dong and others (2010) shows that smaller aggregate sizes and the use of polypropylene fibers and latex can increase abrasion resistance as tested by ASTM C944, Standard Test Method for Abrasion Resistance of Concrete or Mortar Surfaces by the Rotating-Cutter Method (Figure 1).

References

Dong, Qiao; Wu, Hao; Huang, Baoshan; and Shu, Xiang, Development of a Simple and Fast Test Method for Measuring the Durability of Portland Cement Pervious Concrete, SN3149,冰球突破网站首页,斯科基,美国伊利诺斯州,2010,27页.

Haselbach, Liv M.,“极端条件下透水混凝土粘土堵塞的可能性”, 水文工程学报, Vol. 15, No. 2010年1月1日,第67至69页.

Mata, Luis Alexander, S透水混凝土路面系统的添加, PhD Dissertation, North Carolina State University, Raleigh, North Carolina, 2008.

Tennis, Paul, D.; Leming, Michael, L.; and Akers, David, J., 透水混凝土路面, EB302, 冰球突破网站首页, Skokie, Illinois, 以及全国预拌混凝土协会, Silver Spring, Maryland, USA, 2004, 36 pages.