ACCELERATING THE THAUMASITE FORM OF SULFATE ATTACK AND AN INVESTIGATION OF ITS EFFECTS ON SKIN FRICTION by RENÉ BRUECKNER (Dipl.-Ing.) A Thesis Submitted to The University of Birmingham for the Degree of DOCTOR OF PHILOSOPHY School of Civil Engineering University of Birmingham Edgbaston Birmingham B15 2TT December 2007 University of Birmingham Research Archive e-theses repository This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder. Synopsis The objective of the research was to accelerate the thaumasite form of sulfate attack (TSA) under laboratory conditions in order to identify its effects on skin friction at the soil/concrete interface. The experimental programme was organised into five series which investigated the formation of TSA under unrestrained and restrained conditions whereby the acceleration of TSA was observed at unrestrained conditions depending on water- cement ratio, cement content, casting face and aggressive solution. Restrained conditions simulated soil/concrete interface interactions and were applied to identify changes of the skin friction affected by the formation of thaumasite. TSA was successfully accelerated and a linear deterioration progress was monitored using a developed needle test method. Using clay-restrained conditions thaumasite formed attached to the concrete and favoured a more severe deterioration culminating in thaumasite layers of up to 25mm depending on interface pH and applied pressure. Thaumasite at the interface did not decrease the shear strength including skin friction and cohesion. Therefore it was concluded that TSA occurring at piles or foundation bases does not affect the stability of the superstructure regarding loss of friction and settlements, however, continuous loss of concrete can increase the slenderness and cause premature corrosion. Table of Contents Contents 1 Introduction .......................................................................................... 1 1.1 Background........................................................................................................1 1.2 Aims and Objectives..........................................................................................3 1.3 Scope of the Thesis............................................................................................4 2 Literature Review................................................................................. 5 2.1 Introduction .......................................................................................................5 2.1.1 Sulfate Attack ............................................................................................5 2.1.2 Thaumasite Form of Sulfate Attack...........................................................7 2.2 Occurrence of TSA..........................................................................................10 2.2.1 Mineral Thaumasite.................................................................................10 2.2.2 Consequences of TSA .............................................................................11 2.2.3 Risk Factors .............................................................................................18 2.3 Formation Mechanism.....................................................................................25 2.3.1 Formation Theories .................................................................................25 2.3.2 Reaction Products....................................................................................26 2.3.3 Stability of Thaumasite............................................................................27 2.3.4 Combined Degradation Forms ................................................................28 2.4 Identification of TSA.......................................................................................30 2.4.1 General.....................................................................................................30 2.4.2 X-ray Diffraction .....................................................................................31 2.4.3 Polarisation Microscopy..........................................................................32 2.4.4 Scanning Electron Microscopy................................................................33 2.4.5 Sampling..................................................................................................34 2.5 Thaumasite Prevention ....................................................................................35 2.5.1 General.....................................................................................................35 2.5.2 Binder ......................................................................................................35 2.5.3 Aggregate.................................................................................................36 2.5.4 Additional Preventive Measures..............................................................36 2.5.5 Guidance..................................................................................................37 2.6 Thaumasite in Laboratory Conditions – Accelerated Tests.............................37 Table of Contents 2.6.1 General.....................................................................................................37 2.6.2 Binder ......................................................................................................38 2.6.3 Aggregate.................................................................................................39 2.6.4 Mix Design ..............................................................................................40 2.6.5 Casting.....................................................................................................40 2.6.6 Curing ......................................................................................................41 2.6.7 Storage Solution ......................................................................................42 2.6.8 Storage.....................................................................................................43 2.7 Results of Comparable Field/Laboratory Trials at BRE .................................43 2.7.1 General.....................................................................................................43 2.7.2 Shipston-on-Stour....................................................................................44 2.7.3 Moreton Valence .....................................................................................46 2.8 Structural Effects .............................................................................................46 2.8.1 Pure Structural Effects.............................................................................47 2.8.2 Soil-Structure Effects ..............................................................................48 2.9 Soil/Structure Interaction.................................................................................49 2.9.1 General.....................................................................................................49 2.9.2 Types of Foundations ..............................................................................49 2.9.3 Physical Interactions................................................................................50 2.9.4 Physical Testing.......................................................................................54 2.9.5 Chemical Interactions..............................................................................60 2.9.6 Effect of TSA on the Concrete/Clay Interface ........................................62 2.10 Summary..........................................................................................................63 3 Methodology and Materials............................................................... 66 3.1 Experimental Programme and Test Specimens...............................................66 3.1.1 General.....................................................................................................66 3.1.2 Test Series ...............................................................................................68 3.1.3 Solution....................................................................................................80 3.1.4 Storage.....................................................................................................80 3.2 Test Methods ...................................................................................................81 3.2.1 Needle Test Rig .......................................................................................81 3.2.2 Consolidation of Clay..............................................................................82 3.2.3 Pressure Rig.............................................................................................83 Table of Contents 3.2.4 Shear Strength .........................................................................................84 3.2.5 Chemical Tests ........................................................................................89