Spalling Damage Research Articles

Sealer and coating systems for the protection of concrete bridge structures

Concrete bridge structures most often experience different forms of deterioration, such as surface scaling, spalling, and internal frost damage due to environmental and chemical attacks. Sealers and coatings are used to reduce these forms of concrete deterioration by limiting penetration of water and water-borne deleterious agents, such as chlorides and sulphates. Moreover, sealers and coatings are used to resist chemical attack and corrosion damage due to de-icer and anti-icer chemicals, such as NaCl, CaCl2, and MgCl2. They also facilitate moisture vapour transmission, and thus aid rapid drying and mitigate the effects of corrosion. This paper presents the key aspects of sealers and coatings used for the protection of concrete bridge structures. It highlights different types and selection criteria of sealers and coatings, surface preparation and application methods required for applying these products, and their role in protecting concrete. In addition, the different evaluation methods and performance criteria for sealers and coatings are discussed in this paper. Key words: Bridge structure, chemical attack, concrete, de-icer and anti-icer, durability, freezing and thawing, moisture vapour transmission, wetting and drying, sealer and coating, physical attack.

Lessons Learned from the Damaged Huilan Interchange in the 2008 Wenchuan Earthquake

A disastrous earthquake struck Wenchuan in China’s Sichuan province in 2008 and caused heavy casualties and structural damage to bridges and buildings. One of the two severely earthquake-damaged curved bridges in China, the Huilan interchange, had been carefully studied, including postearthquake investigation and identification of the cause of failure for this bridge. The Huilan interchange, constructed in 2004 in Mianzhu City, consisted of a viaduct and four horizontally circular ramp bridges with continuous box girders. Field investigations found that the seismic damage to the ramp bridges was especially heavy, one or two short piers in all, but one of the ramp bridges experienced severe failure, and the box girders over the failed piers were fractured. Other piers of the ramp bridges suffered minor-to-moderate damage, including concrete cover spalling, concrete cracking, and slippage damage of the rubber bearings. The viaduct suffered only slight damage, including slippage damage of the rubber bearings and pounding damage of the superstructure. The seismic performance of the bridge was evaluated by finite-element modeling and compared with field observations. It was found that the bearing on top of the shortest pier, Pier 1, was damaged first. Then, the seismic action was concentrated on the next shortest pier, Pier 2, which had the largest flexural stiffness. Pier 2 first yielded in flexure, and, as the lateral displacement increased, the ultimate response of this pier was dominated by its shear capacity, and it eventually failed in flexure-shear mode.

Selecting Construction Measures for Mitigating Early-Age Delamination in CRC Pavements Made with Gravel Aggregates

Gravel aggregates have been used extensively in the Houston District for continuously reinforced concrete (CRC) pavements construction for many years. However, some of these pavements have been subject to early-age delamination and eventual spalling damage. A series of studies since the early 1990's have been conducted to gain a better understanding of mechanisms, material properties, and construction practices related to delamination and spalling. This paper describes a systematic and methodical approach for selecting construction measures to counter the negative effects of using gravel aggregates in concrete paving as it pertains to minimizing early-age delamination distress. The approach was developed based on laboratory measures and practices, numerical approaches for assessing delamination potential, and test sections established in the Houston District, Texas. The testing programs in the laboratory and the field, as well as the analytical results, are presented in this paper. The analysis of the results leads to a step-by-step approach for evaluating and selecting construction measures.

Post mortem analysis of burned magnesia-chromite brick used in short rotary furnace of secondary lead smelting

Burned magnesia-chromite bricks are the standard product for the lining of furnaces in lead industry, where the short service life is a great problem. Used sintered magnesia-chromite brick sample from short rotary furnace lining, sent by a secondary lead manufacturer, showed parallel cracks to the hot face due to structural spalling damage. The refractory infiltrated region and slag interface were analyzed using a scanning electron microscope with an energy dispersive spectroscopy analyzer, and X-ray diffraction powder analysis. Crucible corrosion test was performed to evaluate the influence of slag attack. The results showed that the structural spalling was due to strong Pb-infiltration of the refractory microstructure by bath components of the furnace (metallic lead and lead sulphite) during the reduction process and that the slag infiltration had little contribution due to the good resistance of the magnesia-chromite bricks to FeO rich slag attack.

An analysis of wear and spalling characteristics of the wheel steel under rolling—sliding conditions

The effects of the brake force, normal load, and carbon content on friction, wear, and spalling behaviours of the wheel steel are investigated in detail in rolling—sliding contact, using a new rolling testing apparatus developed on a tension—compression hydraulic machine with a high precision. Wear scars are examined and analysed by various microscopic examinations. The results show that the friction coefficient of the wheel steel increases and the wear mechanisms would change with increasing brake force. Furthermore, an increase in the brake force and normal load would cause an increase in the wear depth of the wheel steel and aggravate the spalling damage on the wear surface. The hardness, wear, and spalling behaviours of the wheel steel depend strongly on the carbon content of the material. Decreasing carbon content of the wheel steel may alleviate spalling damage evidently, but would rapidly increase the wear depth of the specimen.

Numerical analysis of blast-induced wave propagation and spalling damage in a rock plate

The paper focuses on the numerical analysis of blast-induced stress wave propagation and related spalling damage in a rock plate or wall. Firstly, a large-scale contact explosion is simplified as a one-dimensional (1-D) strain problem, and a cross-format centered finite-difference scheme is presented. Secondly, the finite-difference code is used to explore the wave propagation in a rock plate, and compared with the commercial software LS-DYNA. Thirdly, a continuum damage constitutive model for rock is introduced and successfully incorporated into the LS-DYNA through its user-defined subroutine. Coupling with the erosion technique, the improved LS-DYNA is used to simulate the blast-induced spalling damage at the back-side of rock plate. Numerical results show that the 1-D finite difference code is convenient and accurate. Also, the user-defined subroutine can well describe the process of spalling damage.

The 2003 Canadian Geotechnical Colloquium: Mechanistic interpretation and practical application of damage and spalling prediction criteria for deep tunnelling

Spalling and strain bursting has long been recognized as a mechanism of failure in deep underground mines in hard rock and in deep infrastructure tunnels. The latter is a significant growth industry, particularly in Europe where subalpine base tunnels in excess of 10 m wide and dozens of kilometres long are being driven by tunnel boring machine (TBM) through alpine terrain at depths greater than 2 km. In more massive granitoid or gneissic ground, these tunnels have experienced significant spalling damage. En route to a practical predictive technique for this condition, the author utilizes a number of analytical and micromechanical tools to validate a simple empirical predictive model for tunnel spall initiation. The true nature of damage and of yield, as the result of extensile damage accumulation, in hard rocks is examined using these tools. Based on the resultant conceptual model, the author expands on the empirical damage threshold, using a spalling limit to differentiate stress paths that lead to crack propagation and spalling from those that incur stable microdamage prior to conventional shear failure at higher relative confinements. Finally, the composite and robust in situ yield model is applied to nonlinear modelling for support design.

Material failure modes, part III: A brief tutorial on corrosion-related material failure modes

This article is the final installment of a three-part series on material failure modes recently published in the MaterialEASE section of AMPTIAC Quarterly. Part One introduced the concept of material failure modes and covered fracture, ductile failure, elastic deformation, creep, and fatigue. Part Two continued the discussion with brief descriptions of impact, spalling, wear, brinelling, thermal shock, and radiation damage. This article completes the series on material failure modes, covering uniform, galvanic, crevice, pitting, intergranular, and erosion corrosion; selective leaching/dealloying; hydrogen damage; stress-corrosion cracking; and corrosion fatigue. The three articles taken together make a valuable desk reference for any professional making material selection and design decisions.

Material failure modes, part II: A brief tutorial on impact, spalling, wear, brinelling, thermal shock, and radiation damage

A number of material failure modes were introduced in this article, including impact, spalling, wear, brinelling, thermal shock, and radiation damage. These mechanisms can affect metals, polymers, ceramics, and composites in various applications and in many different environments. Thus, it is important to take these failure modes into consideration during the design phases of a component or system in order to make appropriate materials selection decisions.

Comparison of localised spalling and crack damage from dynamic modelling of spur gear vibrations

This paper presents a 26 degree of freedom gear dynamic model of three shafts and two pairs of spur gears in mesh for comparison of localised tooth spalling and damage. This paper details how tooth spalling and cracks can be included in the model by using the combined torsional mesh stiffness of the gears. The FEA models developed for calculation of the torsional stiffness and tooth load sharing ratio of the gears in mesh with the spalling and crack damage are also described. The dynamic simulation results of vibration from the gearbox were obtained by using Matlab and Simulink models, which were developed from the equations of motion. The simulation results were found to be consistent with results from previously published mathematical analysis and experimental investigations. The difference and comparison between the vibration signals with the tooth crack and spalling damage are discussed by investigating some of the common diagnostic functions and changes to the frequency spectra results. The result of this paper indicates that the amplitude and phase modulation of the coherent time synchronous vibration signal average can be effective in indicating the difference between localised tooth spalling and crack damage.

Sealing system selection for jointed concrete pavements – A review

Concrete pavement joints are cracks intentionally formed in the pavement to accommodate expansion and contraction due to temperature changes. Today, 98% of the agencies building and maintaining concrete roadways, and 100% of the agencies building and maintaining concrete airport pavements in the United States require the sealing of these joints for new pavements. There are two major reasons for sealing rigid pavement joints. The first is to reduce the amount of water infiltrating the pavement structure, which results in slab erosion and loss of support. The second reason is to minimize the entry of incompressible materials into the joint reservoir, resulting in point loading when slabs expand under hot temperatures and subsequent joint spalling damage. Another reason for sealing rigid pavement joints is to reduce the potential for dowel bar corrosion by reducing entrance of de-icing chemicals. The proper sealing and maintenance of concrete pavement joints thus seems to be essential for the overall performance of the rigid concrete pavement. This paper seeks to find out the factors that affect sealant life and performance and how to mitigate these to improve performance and reasonably extend sealant and thereby pavement life.

Delamination in drilling GFR-thermoset composites

Delamination is a major problem associated with drilling fiber-reinforced composite materials that, in addition to reducing the structural integrity of the material, also results in poor assembly tolerance and has the potential for long-term performance deterioration. Delamination-free in drilling different fiber reinforced thermoset composites is the main objective of the present paper. Therefore the influence of drilling and material variables on thrust force, torque and delamination of GFRP composites was investigated experimentally. Drilling variables are cutting speed and feed. Material variable include matrix type, filler and fiber shape. Drilling process was carried out on cross-winding/polyester, continuous-winding with filler/polyester, chopped/polyester, woven/polyester and woven/epoxy composites. A simple inexpensive accurate technique was developed to measure delamination size. The results show that the presence of sand filler in continuous-winding composites not only raised the values of cutting forces and push-out delamination but also increased their values with increasing cutting speed. In contrast, increasing the cutting speed in drilling cross-winding, woven and chopped composites reduces the push-out delamination as a result of decreasing the thrust force. The thrust forces in drilling continuous-winding composite are more than three orders of magnitude higher than those in the cross-winding composites. Chopped composites have lower push-out delamination than those made from woven fibers. For the same fiber shape, the peel-up and push-out delaminations of woven/epoxy composite are lower than that for woven/polyester composites. Delamination, chipping and spalling damage mechanisms were observed in drilling chopped and continuous-winding composites. In drilling woven composites the delamination was observed at different edge position angles due to the presence of the braids that made by the interlacing of two orthogonal directions of fibers tows (warp and fill). Delamination-free in drilling cross-winding composites was achieved using variable feed technique.

DELAMINATION IN DRILLING GFR-THERMOSET COMPOSITES

Delamination is a major problem associated with drilling fiber-reinforced composite materials that, in addition to reducing the structural integrity of the material, also results in poor assembly tolerance and has the potential for long-term performance deterioration. Delamination-free in drilling different fiber reinforced thermoset composites are the main objective of the present paper. Therefore the influence of drilling and material variables on thrust force, torque and delamination of GFRP composites was investigated experimentally. Drilling variables are cutting speed and feed. Material variable include matrix type, filler and fiber shape. Drilling process was carried out on cross-winding/polyester, continuous-winding with filler/polyester, chopped/polyester, woven/ polyester and woven/epoxy composites. A simple inexpensive accurate technique was developed to measure delamination size. The results show that the presence of sand filler in continuous-winding composites not only raised the values of cutting forces and push-out delamination but also increased their values with increasing cutting speed. In contrast, increasing the cutting speed in drilling cross-winding, woven and chopped composites reduces the push-out delamination as a result of decreasing the thrust force. The thrust forces in drilling continuous-winding composite are more than three orders of magnitude higher than those in the cross-winding composites. Chopped composites have lower push-out delamination than that made from woven fibers. For the same fiber shape, the peel-up and push-out delaminations of woven/epoxy composite are lower than that for woven/polyester composites. Delamination, chipping and spalling damage mechanisms were observed in drilling chopped and continuous-winding composites. In drilling woven composites the delamination was observed at different edge position angles due to the presence of the braids that made by the interlacing of two orthogonal directions of fibers tows (warp and fill). Delamination-free in drilling cross-winding composites was achieved using variable feed technique.

Assessment of the Exit Defects in Carbon Fibre-Reinforced Plastic Plates Caused by Drilling

This paper investigates the formation of the exit defects in carbon fibre-reinforced plates and characterizes their features in terms of drilling conditions. It was found that spalling and fuzzing are the major mechanisms of exit defects. The spalling, consisting of a main region and a secondary region, is caused by chisel and cutting edge actions, in which the former plays a key role. The fuzzing, however, exists in the cutting region where the included angle between the fibre direction of the surface layer and that of the cutting speed is acute. A severer spalling damage corresponds to a high spindle speed, a large feed rate and a great thrust force. Some empirical relationships, including a dimensionless formula, were developed for assessing the characteristic dimension of the spalling damage based on the known drilling conditions.

Surface mechanical strength assessment of various spray coatings on cylindrical substrates

Scratch testing is presented as evidence of the mechanical strength (adhesion and cohesion) of various spray coatings (detonation gun and plasma spraying) on cylindrical substrates from industrial suppliers. Applied to medium thick (approx. 20 μm) and thick (100 μm or more), rough and porous brittle coatings, scratch testing is presented as part of a general procedure including single and multi-pass operation at constant loads. The observed damage is essentially cohesive and acoustic emission becomes an indicator of chipping rather than spalling damage. Coating perforation can be reliably and reproducibly identified by means of on-line friction force monitoring which may also yield information about ploughing and prow formation in multi-pass operation. The critical load for the onset of through-thickness cracking is found to be inadequate for reliable quality ranking.

Deformation and failure kinetics of contacting bodies in unsymmetrical dynamic interaction

The loading is usually asymmetrical when explosive and shock loads act on metal specimens, which is of considerable practical importance in relation to the deformation and failure occurring in the microsecond range. The authors present a numerical simulation of the cratering and failure in flat obstacles, performed by the finite-element method in the two-dimensional approach. The colliding bodies are described as a compressible elastoviscoplastic medium whose behavior under dynamic loading is characterized by the sheer modulus, the dynamic yield point, and the viscosity. Dynamic failure was stimulated by means of a kinetic model of active type which has previously been used to stimulate spalling damage in axially symmetrical interaction between solids.