In 1982 the Business Roundtable prepared several reports which investigated various aspects of construction which posed significant research opportunities. Their findings placed piping construction in the group of activities categorized as having "highest potential" for improvements based on inefficiency, or construction difficulty and proportionate costs. It was estimated that over $1 billion could be saved annually if the difficulty in the piping industry was improved to only average of other areas. Further investigation into the piping area showed that the alignment process took 20% of the cycle time for installation and ranked either first or second as compared to other task involved in pipe installation with regards to complexity, skills required and dependency on technical information. Based on the above, this research project was performed to develop a new technique to aid in the alignment process of underground gravity glow pipe. Included in the research was a detailed investigation into existing techniques for performing this task, establishment of a sample analysis to establish workable tolerances for pipe installation, the development of a laser-controlled excavation system and a cost analysis of the new technique presented. All technology used to develop this improved process consisted of currently available equipment used in other fields.

Yes / Concrete structures in sewer systems, marine engineering, underground engineering and other humid environments are easily subjected to microbial attachment, colonization and, eventually, deterioration. With careful selection and treatment, some additives including inorganic and organic antimicrobial agents were found to be able to endow concrete with excellent antimicrobial performance. This paper reviews various types of antimicrobial concrete fabricated with different types of antimicrobial agents. The classification and methods of applying antimicrobial agents into concrete are briefly introduced. The antimicrobial and mechanical properties as well as mass/weight loss of concrete incorporating antimicrobial agents are summarised. Applications reported in this field are presented and future research opportunities and challenges of antimicrobial concrete are also discussed in this review. / National Science Foundation of China (51908103 and 51978127), China Postdoctoral Science Foundation (2019M651116)

Although design codes have accepted lightweight concrete as a suitable structural material for nearly 50 years, there is still a good deal of uncertainty as to how to calculate the strength of this material when designing for shear in beams.  Design codes tend to penalize lightweight concrete due to its lower tensile strength and smoother interface along the shear cracks.  In this study, there were twelve tests on six full-scale, prestressed girders with composite decks designed to provide answers to some of those uncertainties.  The variables considered were concrete density, concrete compressive strength, effective shear depth, shear span-to-effective depth ratio, the amount of shear reinforcement, and the composite cross-sectional area.  Results show that the sand-lightweight concrete girders exceeded the expected shear strength according to the 2010 AASHTO LRFD Bridge Specifications.  Compared to normal weight concrete, sand-lightweight concrete performed reasonably well, and therefore, does not need a lightweight modifier when designing for shear.  However, a reliability analysis of the sand-lightweight girders in this study as well as twelve previous experiments indicate that there should be two different strength reduction factors for the shear design of sand-lightweight concrete depending on which shear design procedures are used in the 2010 AASHTO LRFD Bridge Design Specifications.  For the General Procedure as well as the guidelines outline in Appendix B5, the strength reduction factor should be increased from 0.70 to 1.00.  For the Simplified Procedure, that factor should be 0.75. / Ph. D.

Chloride-induced corrosion of reinforcing steel is widely accepted as the primary cause of premature deterioration in concrete bridge decks (Brown, M.C., 2002). Since linear cracking in concrete cover can potentially accelerate chloride ingress to the depth of the reinforcing steel, there is reason to believe that severity of deck cracking can significantly influence the time to first repair and/or rehabilitation of the bridge deck. Surface width, orientation, and length of cracks in 38 Virginia bridge decks were investigated in order to characterize the general distribution of deck cracking in the commonwealth of Virginia. Crack data was correlated to structural/material design parameters and environmental exposure conditions in order to determine significant predictor-response relationships. The majority of surveyed bridge decks were divided into four classifications of deck type based on superstructure type and construction era, either 1968-1971 or 1984-1991. Surveyed bridge decks that did not fit into any of the four classifications were used to form more generalized subsets. These larger subsets were used to determine if significant influence factors could be translated to broader classifications of bridge decks. Transverse beam spacing, annual average daily truck traffic (AADTT), resistivity of the deck concrete, chloride exposure, and the percentage of concrete clear cover depths less than or equal to 38mm (1.5 in) were all determined to have a significant correlation with linear deck cracking. / Master of Science

In addition to immediate elastic deformations, concrete undergoes time-dependent deformations that must be considered in design. Creep is defined as the time-dependent deformation resulting from a sustained stress. Shrinkage deformation is the time-dependent strain that occurs in the absence of an applied load. The total strain of a concrete specimen is the sum of elastic, creep, and shrinkage strains. Several test beams for the Pinner's Point Bridge have been produced by Bayshore Concrete Products Corp., in Cape Charles, VA. These beams feature high strength concrete mix designs with specified 28-day compressive strengths of 55.2 MPa (8,000 psi) and 69.0 MPa (10,000 psi). These test beams were equipped with thermocouples to track interior concrete temperatures, and vibrating wire gages placed at the center of prestressing to record changes in strain. Laboratory creep and shrinkage testing was conducted on specimens prepared with identical materials and similar mixture proportions to those used at Bayshore. The temperature profile from the test beams during steam curing was used to produce match-cured specimens for laboratory testing. Two match cure batches were produced, along with two standard cure batches. Creep specimens from each batch were placed in the creep room and loaded to 30 percent of their after-cure compressive strength. The creep room had a temperature of 23.0 ± 1.7 °C (73.4 ± 3 ºF) and relative humidity of 50 ± 4 %. Companion shrinkage specimens were also placed in the creep room. Measurements were taken on the creep and shrinkage specimens using a Whittemore gage. Four cylinders were also equipped with embedded vibrating wire gages (VWGs) so that the interior and exterior strains could be compared. The Whittemore and VWG elastic and creep strains were similar, while the VWGs recorded significantly less shrinkage. The measured creep and shrinkage strains were compared to seven different models to determine which model was the most accurate. The models considered were ACI 209, ACI 209 modified by Huo, CEB Model Code 90, AASHTO-LRFD, Gardner GL2000, Tadros, and Bazant B3. The ACI 209 modified by Huo was most accurate in predicting time-dependent strains. / Master of Science

Concrete corrosion has serious societal and economic impacts and is an important concern in a utility's overall corrosion control strategy. Though concrete based pipes and linings are only restricted to the distribution mains, they still make up a large percentage of the drinking water infrastructure at about 17% of its total length. An improved understanding of the corrosion mechanisms involved steps that can be taken to mitigate concrete corrosion are very important. This study examined the role of phosphate chemicals, water chemistry, temperature and gaseous cavitation on the degradation of cement-based pipes and linings. It also provides information for utilities to make informed decisions regarding the use, effectiveness, and application of phosphate corrosion inhibitors relative to concrete corrosion control. Under low alkalinity and low pH conditions, considered to be highly aggressive in the literature, we noticed very substantial corrosion of concrete in laboratory experiments. At high pH and high alkalinity conditions, the buildup of scale (e.g., calcium carbonate) on the inside of the pipe is the major concern. The addition of phosphate inhibitors strongly influenced both concrete corrosion and scaling. At low alkalinity the addition of zinc orthophosphate or polyphosphate reduced corrosion of concrete. The addition of orthophosphate under low alkalinity conditions increased aluminum leaching and could push aluminum concentrations above the EPA SMCL threshold. At high alkalinity conditions the addition of orthophosphate is highly effective at reducing scaling, and aluminum leaching was not a concern. The presence of high concentrations of magnesium and silicon could form magnesium aluminum oxyhydroxides and magnesium silicates which could act as a protective scale on the concrete surface. However, this precipitate forms only at pH values above 9.5. The effectiveness of this protective scale in reducing corrosion of concrete was not established unambiguously in this research. Temperature plays a key role in corrosion of concrete. Calcite solubility increases at lower temperatures however at higher temperatures corrosion of concrete increases, which implies that corrosion of concrete is not driven by calcite solubility. At higher alkalinities scaling of concrete is higher at lower temperatures. This indicates that calcite solubility controls scaling of concrete at higher alkalinities. Tests with gaseous cavitation indicate that corrosion of concrete does not increase in the presence of gaseous cavitation. Vaporous cavitation is more detrimental to concrete than gaseous cavitation. / Master of Science

No / This paper summarises the data from 1819 tests on concrete-filled steel tube columns and compares their failure load with the prediction of Eurocode 4. The full data is given on the website http://web.ukonline.co.uk/asccs2 . The comparison with Eurocode 4 is discussed and shows that Eurocode 4 can be used with confidence and generally gives good agreement with test results, the average Test/EC4 ratio for all tests being 1.11. The Eurocode 4 limitations on concrete strength could be safely extended to concrete with a cylinder strength of 75 N/mm2 for circular sections and 60 N/mm2 for rectangular sections.

A fully automated computer program is developed for the optimum design of steel space trusses acting compositely with a concrete slab placed on top. The program sizes the truss members to meet the requirements of the load and resistance factor design specification of the American Institute of Steel Construction using the load combinations of ANSI. Earthquake loading is not considered. The optimum size is based on minimum cost, regarding the amount of welding required at the joints and of the member itself. The total cost is based on all steel work in the truss. Once the truss configuration has been defined, and it has been ensured that linear elastic behavior exists, the structure is analyzed for the construction process, to make sure that no overstressing will take place in any structural element at any time during construction and service. The analysis and design principles are presented and an actual design case is solved. (Abstract shortened with permission of author.)

Adequate interfacial bond performance of Bonded Concrete Overlay (BCO) systems requires novel integration of material mixture design, compatibility model development, and interfacial bond design. This entails the use of the right materials, on the right substrate, in the right way, in order to secure the best possible composite behaviour. The overall composite performance of BCOs depends largely on achieving the right proportion of blend for the overlay material. The use of mixture experiments provides a flexible, easy, and quick way of optimizing multi-component materials of this nature. This study describes the use of optimization techniques within the concept of material mixture experiments for proportioning and designing the material constituents of a Bonded Roller Compacted Fibre Reinforced Polymer Modified Concrete (BRCFRPMC). By constraining the range of variability of the constituents, a feasible design space was created with 13 experimental points treated based on the required structural and elastic properties of the overlay. The optimum consistency-time for full consolidation and composite behaviour with the substrate ordinary Portland cement concrete (OPCC) was established between 34.05 and 34.87 seconds, while the resulting apparent maximum density achieves between 97.11% - 98.03% of the theoretical air-free density. In addition, compressive strength response at early and matured ages of 3 and 28 days were satisfied at 100% desirability. The elastic modulus response at age 3 showed 0% desirability, but attains about 99.96% of the target response by 28 days. The verification experiments conducted on each response property shows that positive correlations exist between the measured responses and the predicted values from the optimization analysis. Also, the bond capability of the optimum designed overlay material was evaluated using both tensile and shear bond strengths parameters. The overall assessment results showed that the overlay material exhibits good bonding with the substrate OPCC and would be able to withstand substantial stresses where sufficient surface texture is provided for aggregates interlocking. Other material properties included in the evaluation process of the overlay material included its tensile strength, coefficient of thermal expansion, and drying shrinkage. Stresses in the overlay, substrate, and at the interface were assessed analytically under various differential movement related conditions. Though the interface and the overlay material exhibited sufficient strength against thermal and shrinkage cracking, the theoretical shrinkage cracking in the overlay was predicted at 6.92MPa when fully restrained axially. Further, for effective fracture process description of the interface, experimentally determined parameters in shear and tension were coupled in Mixed-Mode Finite Element Analysis using differential edge deformation model between the overlay and the underlay. The results indicated that delamination in partial fracture process varied from that of complete fracture process, influenced distinctly and largely by the magnitude of the applied load. Other influencing factors in the analyses included the elastic mismatched properties, initial edge defect size, and the plane of loading. Lastly, analytical solution to the FEA problem was implemented using the proposed Modified Eigenvalue Buckling Analysis (MEBA). The result indicated that the proposed analytical method simulates and compares well with the FEA result. The proposed method also provided a good technique for predicting the Mixed-Mode Buckling failure Mode-Shape of the overlay.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Concrete water retaining structures (WRS) in South Africa are under scrutiny due to the numerous durability problems that they have experienced lately; despite the efforts by local and national authorities in conserving these structures. At the heart of these problems are the creep and shrinkage phenomena. While shrinkage is the reduction of concrete volume with time, creep is defined as the time-dependent increase of concrete strain under constant or controlled stress. Both phenomena are affected by conditions to which WRS are exposed hence their accurate prediction is required. Numerical models have been developed to calculate the extent to which concrete creeps or shrinks over time. The objective of this thesis is to identify which of these models is better equipped to be used in South African WRS design. This is achieved through a systematic method that involves an investigation into the contents of these models and a statistical comparison of model calculations to WRS representative data. In partnership with reputable universities, a pioneer experimental creep and shrinkage data base is created in this project from which the WRS related data is selected. While investigating the contents of the numerical models, their applicability to South African WRS is identified and the integrity of model contents is assessed. Indeed, a few irregularities are found in the process and are presented in this thesis. The model calculations are statistically compared to data in the form of individual experiments as well as in the form of groups of experiments with similar concretes to find the ideal prediction model for different types of concretes as well. Also pioneered in this project is a weighted criteria and point system in which the findings of the model content assessment and statistical evaluations are incorporated. It is based on this system that conclusions are drawn and the most suitable prediction model for WRS design in South Africa is selected.