A sports field construction method that uses a geotextile to support the root zone atop a synthetic drainage structure is an alternative to the common design that uses gravel drainage material to support the root zone. A study was conducted to address the concern that fine particles in the root zone may migrate under the influence of percolating water, clog geotextile pores, and restrict the amount of water drained from a sports field. In test columns, six root zone mixtures with different particle size distributions were combined with ten geotextiles with different opening sizes to produce 60 replicated treatments. Water flow through the root zone mixture-geotextile combinations in the test columns was evaluated over a six-month period. Change in permeability was assessed by monitoring the temporal distribution of drainage from a 25-mm pulse of water applied to 300-mm deep root zone mixture in the test column. Particles in drainage water were analyzed for size distribution. The study revealed that drainage rates were affected more by drainage trough the root zone mixture than through the geotextile. The amount and particle size distribution of particles in drainage water were influenced more by root zone mixture than by geotextile. It appeared that in the establishment phase of a sports field that fine particles in the root zone may present more of a problem to clogging of the root zone pores than clogging of the geotextile pores.

Recycled concrete aggregate (RCA) is often used as a replacement of virgin aggregate in road foundations (base course), embankments, hot-mix asphalt, and Portland cement concrete. However, the use of RCA in exfiltration drainage systems, such as French drains, is currently prohibited in many states of the U.S. The French drain system collects water runoff from the road pavement and transfers to slotted pipes underground and then filters through coarse aggregate and geotextile. The primary concerns with using RCA as a drainage media are the fines content and the precipitation of calcium carbonate to cause a reducing in filter fabric permittivity. Additional concerns include the potential for rehydration of RCA fines. The performance of RCA as drainage material has not been evaluated by many researchers and the limited information limits its use. A literature review has been conducted on the available information related to RCA as drainage material. A survey was issued to the Departments of Transportation across the nation in regards to using RCA particularly in French drains. Some state highway agencies have reported the use of RCA as base course; however, no state reports the use of RCA in exfiltration drainage systems. This thesis describes the investigations on the performance of RCA as backfill material in French drains. RCA was tested for its physical properties including, specific gravity, unit weight, percent voids, absorption, and abrasion resistance. RCA cleaning/washing methods were also applied to evaluate the fines removal processes. The potential for RCA rehydration was iv evaluated by means of heat of hydration, pH, compressive strength, and setting time. The permeability of RCA was tested using the No. 4 gradation. Long term permeability testing was conducted to evaluate the tendency for geotextile clogging from RCA fines. Calcium carbonate precipitation was also evaluated and a procedure to accelerate the precipitation process was developed. The results show that RCA has a high abrasion value, that is, it is very susceptible to break down from abrasion during aggregate handling such as transportation, stockpiling, or placing. The most effective cleaning method was found to be pressure washing with agitation. RCA has not demonstrated the tendency to rehydrate and harden when mixed with water. The permeability test results show that the No. 4 gradation does not restrict the flow of water; the flow rate is highly dependent on the hydraulic system itself, however excessive fines can cause large reductions in permeability over time. It has been determined that No. 4 gradation of RCA can provide a suitable drainage media providing the RCA is properly treated before its use.