Surface Gravel - EPAcharacteristic. Notice the good blend of stone, sand and . also been mixed with crushed, recycled concrete and .. dry and harden in sunny and windy weather.crushed stone harden,Flagstone Patio on Crushed Stone - Ask the BuilderInstalling flagstone on crushed stone is easy if done properly. . said the crushed line beneath the flagstones would eventually harden like concrete.
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