The concrete pavement industry is actively seeking new and innovative solutions to build more economical, more sustainable and more durable roads. Cupolex® is one innovative product that is being evaluated for use as a concrete pavement technology. This product consists of interlocking, modular, dome-shaped plastic units that serve as a permanent formwork within the concrete pavement structure. The resulting product is a concrete pavement slab with a system of interconnected vault-like voids below the surface. The dome shape is capable of providing carrying capacities equivalent to conventional slabs, but requires less concrete to do so, and also provides additional drainage and ventilation benefits. A collaborative research effort was undertaken to evaluate the feasibility of using Cupolex® in road and highway applications. As part of this study, a full-scale, instrumented trial section was designed and constructed to evaluate pavement performance in an accelerated loading scenario. This thesis presents this evaluation of the Cupolex® technology in a pavement application through the evaluation of numerous parameters during the pavement’s first year of service. Strain gauge data, pressure cell data, moisture probe data, Falling Weight Deflectometer testing results and visual condition surveys are all used to assess performance. The results obtained to date indicate that Cupolex® has great potential as a concrete pavement technology. The trial pavement sections are performing very well after one year of service, carrying heavily loaded aggregate trucks in the harsh Canadian climate. Over 1.3 million cumulative Equivalent Single Axle Loads (ESALs) have been applied to the pavement to date without any significant pavement degradation. The findings obtained also indicate that the Cupolex® technology can provide significant material and potential cost savings, when compared to conventional jointed plain concrete pavements.

Anti-icing agents are applied to road surfaces to prevent ice formation and to melt any hail or snow as it falls. The specific agent is selected to provide optimum anti-icing properties for the particular local climate in different municipalities taking into account cost, availability and properties. These anti-icing agents are generally applied in liquid form, and due to their low freezing temperatures, are able to remain liquid at the low ambient temperatures. Unfortunately, the negative aspect of the use of liquid agents is that they are able to penetrate concrete structures to a greater extent than can the solid de-icers, such as rock salt. Once the chloride solutions penetrate the concrete, they can have serious deleterious effects on both the reinforcing steel as well as the concrete [1]. It has been shown in previous studies that the cations of the solutions will tend to react with the cementitious materials to form precipitates of expansive nature. More specifically, the reaction of CaCl2 with Ca(OH)2 results in the formation of expansive calcium hydroxy-chloride [2]. The reaction of MgCl2 with Ca(OH)2 forms Mg(OH)2 in the capillary pores with CaCl2 as a by-product after which the MgCl2 can react with the calcium-silicate-hydrate to form magnesium-silicate-hydrate – a gel-like material with no inherent binding properties or strength. The calcium hydroxy-chloride and Mg(OH)2 precipitates can have a positive effect at early onset, but will eventually cause deterioration of concrete due to the internal forces applied by the precipitates as their volume increases. This can affect the strength and create notable interior strain in the concrete. There are a number of mechanical properties that can be analyzed using short-term testing that will help to determine any changes occurring due to salt solution exposure. To gain a general understanding of the effects of the salt solution exposure in this project, compressive strength, tensile strength, elastic modulus, and strain were measured using a number of exposure conditions. While the results of testing confirm that there are initial benefits beyond minimizing ice formation and bonding, there ultimately exist a number of concerns with respect to the reactions that occur between the salts and hardened cement paste. Although the formation of calcium hydroxy-chloride is known to be expansive [3], evidence of this compound was only seen indirectly through elevated strain and micro-cracking. There was no deterioration of compressive strength, tensile strength, or elastic modulus over the short-term testing. Similarly, and again due to the short testing period, the formation of magnesium-silicate-hydrate (M-S-H) is unlikely to have occurred, though its formation during long-term exposure can result in complete loss of binding strength [2]. However, the precipitation of Mg(OH)2 is believed to be responsible for the lower chloride diffusion rate as well as the increase in strength of the concrete exposed to MgCl2. The only agent which did not yield changes of concern with respect to concrete is the NaCl solution while CaCl2 produced the most deleterious effects.

In most industrialized countries, significant future activity in the construction sector will be related to repair and rehabilitation of aging infrastructure. This will require use of durable and high performance repair materials. Among various mechanisms cited for lack of durability in repairs, early-age shrinkage cracking in overlay materials is of utmost importance. Fiber-reinforcement can be used to alleviate some of the issues related to plastic shrinkage. However, quantifying the performance of cement-based composites under restrained shrinkage conditions remains an issue. Various test techniques are available to measure free and restrained shrinkage, but do not simulate the real constraint imposed by the substrate on the overlay. In this dissertation, an innovative test method called the bonded overlay technique is described. An overlay of fiber-reinforced material to be tested is cast directly on a substrate, and the entire assembly is subjected to controlled drying. Cracking in the overlay is then monitored and characterized. During the development of this test method, instrumentation was included to enable measurement of the crack propagation rate using image analysis, evaporation rate, heat development, and strain using embedded sensors. Using the above technique, the effect of mix proportion including variables such as water-cement ratio (w/c), sand-cement ratio (s/c), and coarse aggregate content were studied. An increase in w/c from 0.35 to 0.6 significantly increased the total cracking. Addition of coarse aggregates reduced shrinkage cracking, however, for the range of s/c investigated, no definite conclusions could be drawn. Mixes with 0-20% fly ash and a 7 lit/m3 dosage of shrinkage reducing admixtures indicated no significant reduction in cracking. The influence of fiber geometry on cracking in overlays was also investigated. Fiber types included different sizes of polypropylene and cellulose fibers and one type of glass fiber (volume fraction ranging between 0-0.4%). Glass fibers at a small dosage of 0.1% were the most efficient fiber and completely eliminated cracking. Of the two field projects considered: one was a plaza deck at the UBC Aquatic Center, where cellulose fibers were used, and the second at the UBC ChemBioE building, where polypropylene fibers were used in slabs-on-grade. Both overlays were instrumented with strain sensors, data from which were monitored over the Internet. Results clearly indicated that fibers reduced the strain development in fiber-reinforced overlays when compared to un-reinforced overlays. An energy-based fracture model was proposed to predict maximum crack widths and in a second study, an equation was proposed to correlate early-age shrinkage and flexural toughness of cellulose fibers. In both models, a reasonable correlation with the test data was observed. In addition, factorial design method was used and a mathematical model was proposed to correlate different variables such as w/c, s/c, and fiber dosage.

This study concerns the strength and behaviour of low-rise shear walls made from high-strength concrete under reversed cyclic loading. The response of such walls is often strongly governed by the shear effects leading to the shear induced or brittle failure. The brittle nature of high-strength concrete poses further difficulties in obtaining ductile response from shear walls. An experimental program consisting of six high-strength concrete shear walls was carried out. Specimens were tested under inplane axial load and reversed cyclic displacements with the test parameters investigated being longitudinal reinforcement ratio, transverse reinforcement ratio and axial load. Lateral loads, lateral displacements and the strains of reinforcement in edge elements and web wall were measured. The test results showed the presence of axial load has a significant effect on the strength and ductility of the shear walls. The axially loaded wall specimens exhibited a brittle behaviour regardless of reinforcement ratio whereas the specimen with no axial load had a lower strength but higher ductility. It was also found that an increase in the longitudinal reinforcement ratio gave an increase in the failure load while an increase in the transverse reinforcement ratio had no significant effect on the strength but influenced the failure mode. A non-linear finite element program based on the crack membrane model and using smeared-fixed crack approach was developed with a new aggregate interlock model incorporated into the finite element procedure. The finite element model was corroborated by experimental results of shear panels and walls. The finite element analysis of shear wall specimens indicated that while strengths can be predicted reasonably, the stiffness of edge elements has a significant effect on the deformational results for two-dimensional analyses. Therefore, to capture the deformation of walls accurately, three-dimensional finite element analyses are required. The shear wall design provisions given in the current Australian Standard and the Building Code of American Concrete Institute were compared with the experimental results. The comparison showed that the calculated strengths based on the codes are considerably conservative, specially when there exists the axial load.

This study concerns the strength and behaviour of low-rise shear walls made from high-strength concrete under reversed cyclic loading. The response of such walls is often strongly governed by the shear effects leading to the shear induced or brittle failure. The brittle nature of high-strength concrete poses further difficulties in obtaining ductile response from shear walls. An experimental program consisting of six high-strength concrete shear walls was carried out. Specimens were tested under inplane axial load and reversed cyclic displacements with the test parameters investigated being longitudinal reinforcement ratio, transverse reinforcement ratio and axial load. Lateral loads, lateral displacements and the strains of reinforcement in edge elements and web wall were measured. The test results showed the presence of axial load has a significant effect on the strength and ductility of the shear walls. The axially loaded wall specimens exhibited a brittle behaviour regardless of reinforcement ratio whereas the specimen with no axial load had a lower strength but higher ductility. It was also found that an increase in the longitudinal reinforcement ratio gave an increase in the failure load while an increase in the transverse reinforcement ratio had no significant effect on the strength but influenced the failure mode. A non-linear finite element program based on the crack membrane model and using smeared-fixed crack approach was developed with a new aggregate interlock model incorporated into the finite element procedure. The finite element model was corroborated by experimental results of shear panels and walls. The finite element analysis of shear wall specimens indicated that while strengths can be predicted reasonably, the stiffness of edge elements has a significant effect on the deformational results for two-dimensional analyses. Therefore, to capture the deformation of walls accurately, three-dimensional finite element analyses are required. The shear wall design provisions given in the current Australian Standard and the Building Code of American Concrete Institute were compared with the experimental results. The comparison showed that the calculated strengths based on the codes are considerably conservative, specially when there exists the axial load.

Geopolymer concretes synthesised from composite class F fly ashes and a mixed alkaline activator were optimised by use of Taguchi orthogonal design method. The optimised mix achieved a compressive strength at the age of 28 days of 70 and 58 MPa after initial curing at 70??C for 12 hours and at 23??C for 24 hours, respectively. The resultant Geopolymer has an amorphous aluminosilicate structure. Efflorescence and the potential risk of alkali-silica reaction for the Geopolymer used in this study are both very low. The research confirmed that the Geopolymer concrete developed in this study is far superior to Portland cement concrete when exposed in a sulphuric acid environment. The standard immersion tests finally selected for this research were in 10% sulphuric acid for 56 days and in 1% sulphuric acid for one year. Geopolymer concrete samples retained their shape without softening though they experienced a mass loss of about 5% and a strength loss of some 30%. Portland cement concrete recorded a mass loss of some 40% in a 10% sulphuric acid for 28 days. The penetration rate of sulphuric acid into the Geopolymer concrete was found to approximately follow Fick’s first law of diffusion and a linear relationship between the neutralisation depth and the square root of immersion time (in day) was established. The degradation processes of Geopolymer concrete in sulphuric acid environments were intensively studied. The first stage involved the preferential liberation of alkali ions. The tetrahedral aluminium in the Si-O-Al configuration was removed and converted to octahedral aluminium. Consequently, the original units of Si(1Al) degraded to a silica polymorph structure in the corroded Geopolymer, which continued to serve a cementitious role. In contrast, in the case of Portland cement concrete, the acid solution dissolved the hydration products of the cement paste. The residual reaction products were found to be soft and have no structural strength. Geopolymers with alkaline activators of mixed sodium hydroxide and sodium silicate did not exhibit any cracking problems. Class F fly ash with low calcium content was found to be suitable for developing a Geopolymer binder able to withstand sulphuric acid attack.

Dissertation (PhD)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Thesis (Ph. D.)--University of Canterbury, 2007. / Typescript (photocopy). "January 2007." Includes bibliographical references. Also available via the World Wide Web.

Thesis (MScIng)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Thesis (Ph. D.)--University of Adelaide, 1990. / Errata inserted. Includes bibliographical references (leaves 336-358).