Quantifying In Situ Tack Coat Performance Using the TackBond Tester for Quality Control

In light of the various quality assurance (QA) issues pertaining to tack coats that occur during construction, there is a need for a means of verifying interlayer bond quality in situ. Despite the immense use of tack coat as a constituent in paving, there are no construction specifications with provisions for the quantification of tack coat bond quality in laboratory or field settings. In this study, a construction QA process for tack coat bond performance was proposed. A novel field tack coat bond strength test device, TackBond, was developed and used for this purpose. The performance of engineered (new tack coat technologies that are tracking less) and conventional tack coats was also evaluated in the laboratory and the field using the developed TackBond test system. The TackBond device was improved in this study by adding features that render it more practical, portable, accurate, and better suited for a variety of pavement surface conditions. Engineered tack coat performance was compared with that of tack coats used conventionally on both milled and overlay surface types. The suitability of the TackBond Test device for capturing the true response of each tack coat was first evaluated by comparing results from TackBond laboratory tests with monotonic direct shear tests (DST) on laboratory-produced samples. Strong correlations between the two test types were achieved. Results of field and laboratory TackBond tests showed that the in situ QA control process developed in this study could be effectively used to improve the in situ tack coat bond performance.

Assessment of AAR and Sulfate Attack on Wadi Gravel Concrete after 4 Years in Service

Wadi gravel is a local aggregate in Qatar that could contribute to enhanced sustainability by replacing expensive imported gabbro. The material needs to be processed before use to reduce sulfate content to acceptable levels. The paper presents the performance assessment of three full-scale buildings, variously made with 50% and 100% Wadi gravel and conventional gabbro concretes. Site monitoring up to four years in service demonstrated the strength development with age and resistance to the aggressive exposure conditions in Qatar. The Wadi gravel concrete exhibited at least similar performance to the gabbro concrete, and excellent durability as defined in national construction specifications. The paper provides initial long-term assessment and builds on previous publications by the authors, for initial assessment of Wadi gravel concrete. In an earlier investigation by the authors, a difference was observed between the concrete prism expansion test results of RILEM AAR-4.1 and BS 812-123. Wadi gravel was classified as potentially reactive in the more accelerated RILEM AAR-4.1 and of low reactivity in the more realistic exposure BS 812-123. Petrographic examination of the hardened concrete after four years in service has shown no evidence of cracking or signs of distress or deterioration and confirmed the BS 812-123 interpretation of alkali-silica reactivity of Wadi gravel concrete. The results obtained in this investigation provide more confidence for the wider and efficient use of Wadi gravel in structural concrete.

Review of Agency Pavement Recycling Construction Specifications

Cold in-place recycling, cold central plant recycling, and full depth reclamation are cost-effective, environmentally conscious pavement rehabilitation or reconstruction techniques. Although these techniques are not new, they have not been widely adopted among state agencies. There has, however, been a recent resurgence in interest in these techniques. To date there are no national specification guidelines for these processes to assist in their widespread implementation, and those specifications that do exist often have a wide range of requirements. This paper presents the results of a review of state and local agency specifications for pavement recycling techniques and offers suggestions to help agencies achieve a better and longer-lasting product when specifying pavement recycling techniques.

Laboratory Evaluation of Gradation Improvement of Marginal Materials for Foamed Bitumen Stabilisation

Foamed bitumen stabilisation is an attractive technology for increasing the use of marginal materials in pavement construction and rehabilitation. However, by their very nature, marginal materials do not meet the prescriptive requirements of many standard specifications. Consequently, performance-related evaluation is required. For foamed bitumen stabilised marginal materials, the cured and saturated moduli are common performance-related parameters that are also used for characterisation during structural pavement design. In this research, the indirect tensile moduli of three foamed bitumen stabilised marginal granular materials were compared to the modulus of a standard or premium material, in both cured and saturated conditions, after 3, 7 and 14 days of accelerated laboratory curing. The results indicated that the magnitude of granular material marginality was not related to the stabilised material modulus. Furthermore, the gradations of the two most marginal materials were improved by blending with another granular material and the improved marginal materials were also stabilised and tested. The gradation improvement had a variable effect on the stabilised material modulus, with the average modulus increasing by more than 20%. The modulus increase associated with the gradation improvement was related to the basis and magnitude of granular material marginality, with the saturated modulus of the most plastic marginal material increasing by the greater amount after improvement. It was concluded that foamed bitumen stabilisation is a particularly effective treatment for marginal granular materials. Furthermore, when used in combination with gradation improvement, the resulting foamed bitumen stabilised material can perform similarly to standard materials, based on cured and soaked modulus values. However, to allow the use of foamed bitumen stabilised marginal materials in pavement construction, specifications must be more performance-related and the current limits on plasticity and gradation must be relaxed.

Automatic Selection Tool of Quality Control Specifications for Off-site Construction Manufacturing Products: A BIM-based Ontology Model Approach

Construction manufacturing specifications play an important role in assessing quality requirements on a construction project. However, working with these specifications can be overly complicated and error prone to the large amount of regulations and codes that need to be considered and their inter-dependencies. In building information modelling (BIM), the model is a digital representation of a complex construction product and contains precise product information data. The data is currently embedded into the model as properties for parametric building objects that are exchangeable among project operators. Some effort has been previously done to enhance the BIM model to obtain construction-oriented data and linking information that is crucial to manufacturing and quality control and assurance with BIM modelling still remains a challenge. This study proposes an extension to the current BIM-based product-oriented ontology model to include manufacturing processes and inspection, and quality control specifications. By automatically identifying which specifications are applicable to certain products and to extract the requirements imposed, this approach can support and enable automatic decision making in quality inspection and control tasks, which solely depend on information and knowledge from construction specifications. This approach is tested and validated using a light-gauge steel frame wall under Canadian construction standards and regulations.

Geosynthetic Reinforced Steep Slopes: Current Technology in the United States

Geosynthetics is a crucial mechanism in which the earth structures can be mechanically stabilized through strength enforcing tensile reinforcement. Moreover, geosynthetic reinforcement stabilizes steep slopes through incorporating the polymeric materials, becoming one of the most cost-effective methods in not only accommodating budgetary restrictions but also alleviating space constraints. In order to explicate on the applicability and widen the understanding of geosynthetic reinforcement technology, a synthesis study was conducted on geosynthetic reinforced steep slope. This study is very important because in not only highlighting the advantages and limitations of using geosynthetic reinforcement but also in investigating the current construction and design methods with a view to determining which best practices can be employed. Furthermore, this study also identified and assessed the optimal condition of the soil, performance measures, construction specifications, design criteria, and geometry of the slope. To further concretize the understanding of these parameters or factors, two case studies were reviewed and a summary of the best practices, existing methods, and recommendations were drawn in order to inform the employment of geosynthetics in reinforcing steep slopes.