 Recently the Canning Dam has been subjected to considerable cracking of the upper parts of the dam and upper gallery . Investigations have shown that cracking was due to strong AAR ( alkali aggregate reactivity ) in the concrete . AAR results in swelling of the concrete , which may cause secondary compressive stresses , localised map cracks , and , ultimately structural cracks . In addition , the concrete tensile strength and elasticity significantly decreases . Many old concrete dams are known to suffer from AAR , including Fontana Dam in Tennessee and Pian Telessio dam in Italy among others . 
 Recently the Canning Dam <a href='been_done' title='1'><mark>has</mark></a> been subjected to considerable cracking of the upper parts of the dam and upper gallery . Investigations <a href='been_done' title='2'><mark>have</mark></a> shown that cracking was due to strong AAR ( alkali aggregate reactivity ) in the concrete . AAR <a href='uninflect' title='3'><mark>results</mark></a> in swelling of the concrete , which may cause secondary compressive stresses , localised map cracks , and , ultimately structural cracks . In addition , the concrete tensile strength and elasticity significantly <a href='uninflect' title='4'><mark>decreases</mark></a> . Many old concrete dams are known to suffer from AAR , including Fontana Dam in Tennessee and Pian Telessio dam in Italy among others . 
Recently the Canning Dam done been subjected to considerable cracking of the upper parts of the dam and upper gallery . Investigations done shown that crackin was due to strong AAR ( alkali aggregate reactivity ) in da concrete . AAR result in swelling of the concrete , which may cause secondary compressive stresses , localised map cracks , and , ultimately structural cracks . In addition , the concrete tensile strength and elasticity significantly decrease . Many old concrete dams r known to suffer from AAR , including Fontana Dam in Tennessee and Pian Telessio dam in Italy among others .