Diagnosis and Control of Alkali-Aggregate Reactions in Concrete
Aggregates containing certain constituents can react with alkali hydroxides in concrete. The reactivity is potentially harmful only when it produces significant expansion.(1)** This alkali-aggregate reactivity (AAR) has two forms—alkali-silica reaction (ASR) and alkali-carbonate reaction (ACR, sometimes called alkali-carbonate rock reaction, or ACRR). ASR is of more concern than ACR because the occurrence of aggregates containing reactive silica minerals is more common. Alkali-reactive carbonate aggregates have a specific composition that is not very common. Alkali-silica reactivity has been recognized as a potential source of distress in concrete since the late 1930s.(2,3) Even though potentially reactive aggregates exist throughout North America, ASR distress in structural concrete is not common. There are a number of reasons for this:
DETERMINE INITIAL CAUSE FOR CURRENT PREMATURE PORTLAND CEMENT CONCRETE PAVEMENT DETERIORATION
ix INTRODUCTION 1 RESEARCH APPROACH 1 EQUIPMENT AND PROCEDURES 2 RESULTS AND DISCUSSION 7 Field Study 7 General Descriptions 7 Air Void Measurements 7 Petrographic Examination 15 Laboratory Study 18 Bulk Materials 18 Premature Stiffening Tests (Mortar Method) 21 Restrained Shrinkage Tests (Paste Method) 28 Unrestrained Shrinkage Tests (Paste Method) 30 Shrinkage During Setting and Hardening (Mortar Method) 35 SUMMARY AND CONCLUSIONS 35 Closing Comments 40 Recommendations 43 Recommendations for Further Research 44 ACKNOWLEDGMENTS 45 REFERENCES 46 APPENDIX A: MODIFIED ASTM C 359 TEST METHOD AND TEST RESULTS 47 APPENDIX B: CORE LOGS 51 APPENDIX C: IOWA DOT ASTM C 666 DATA 95 APPENDIX D: PETROGRAPHIC SUMMARIES AND SITE INFORMATION 104 APPENDIX E: RESULTS OF SHRINKAGE TESTING 125 APPENDIX F: HYPOTHESIS FOR PREMATURE CONCRETE DETERIORATION.....129
Bone changes in tuberous sclerosis mimicking metastases.
Sclerotic and lytic bone changes of tuberous sclerosis (TS) can mimic bone metastases. We report a case of bone metastases from bronchogenic carcinoma in a patient with TS bone changes. Bone scintigraphy and magnetic resonance imaging are useful in distinguishing the TS bone lesions from bone metastases.