Abstract
A test method for resistance of waterproofing membranes to the penetration of roots at lap joints was developed on the basis of the behavior of bamboo grass tips to penetrate the membrane. The resistance of the membranes at lap joints having non adhesives and different bonding strengths was determined as a measure of its vulnerability to root penetration. Results from field tests indicated that bamboo grass tips (rhizome) easily penetrated lap joints of non-adhesive membranes. Hence it was evident that waterproofing membrane systems having non-adhesive overlapped joints do not provide adequate resistance to root penetration of the membrane. The resistance to root penetration is dependent on the adhesive strength of the lap joint. The specimens with lap joints having lower bonding strengths were readily penetrated by the rhizome. From this knowledge, a test method was developed to assess the expected resistance of membrane lap joints to the penetration of a needle. The needle, in essence, emulated the shape of bamboo grass tips. Thereafter, the test result from field test on the resistance of membrane to the penetration of roots were compared to those obtained from tests using a penetrating needle. Results from the penetrating needle test indicated that the resistance measured at a 10-mm displacement of needle was effective means of evaluating the resistance of membrane lap joints to the penetration of roots.
