Journal of Materials in Civil Engineering

The current method of steel bar soil nail construction is both labor intensive as well as expensive and many engineers are considering the use of new soil nail materials. In the present pilot test, an innovative soil nail is constructed by light weight high strength glass fiber-reinforced plastic (GFRP) pipe with the Tube a’ Manchette grouting technique. It is found that this new soil nail system can be handled easily on sites with difficult access. Extensive laboratory as well as field tests were carried out on the GFRP pipe nails and the grouted soil mass and numerical modeling of a field test was performed. The installation of the GFRP pipe, laboratory, and field test results that were carried out in Hong Kong and Korea are discussed in this paper.

A laboratory study was undertaken to evaluate the in situ performance of self-compacting concrete (SCC) compared to a conventional compacted concrete (CCC) of similar strength in reinforced concrete T-beams. As an additional feature, the desired SCC properties were obtained partly by the introduction of fly ash to enable a SCC, of strength similar to the conventional concrete, to be attained at little or no additional cost. The performance of SCC in the T-beam was assessed in terms of homogeneity and uniformity, uniformity of surface hardness, in situ compressive strength, and likely durability. Further, the structural responses of the T-beams in terms of initiation and propagation of structural cracks, cracking pattern, mode of failure, and load versus deflection behavior were investigated under single point loading. The study suggests that SCC performs at least as well as CCC in terms of homogeneity, uniformity of construction, and structural responses, and is likely to have improved durability.

The application of the Hoek–Brown empirical strength criterion to actively confined concrete is investigated. A large database of experimental results on hydraulically and triaxially confined concrete is reviewed and analyzed. The normalized two-parameter Hoek–Brown criterion provides a simpler and more robust fit than theoretical and empirical models previously proposed in the literature for actively confined concrete. The Hoek–Brown curved failure surface is used to predict the failure angles that are experimentally observed in the brittle mode. A residual stress lower bound is proposed based on the brittle fracture mechanism. The analysis of this residual stress lower bound allows the formal identification of the transition between the brittle and the ductile failure modes in confined concrete. The modeling results are compared with the available published data and good agreement is found between the experimental observations and the predictions of the model. Recommendations for the integration of the Hoek–Brown model in the concrete design equations are also provided.

To explore the significance and shortcomings of an environment-friendly binder using powder typed activators, 16 alkali-activated (AA) cementless mortars and a control ordinary Portland cement (OPC) mortar were mixed, cured under room temperature, and tested. Both fly ash (FA) and ground granulated blast-furnace slag (GGBS) as the source material were activated by a combination of sodium silicate and sodium hydroxide powders. The main variables examined were the mixing ratio of sodium oxide $\left({\mathrm{Na}}_2\mathrm{O}\right)$ of the activators to source material by weight, and the Blain fineness of the GGBS. The flow loss and compressive strength development of the mortars tested were examined according to the alkali quality coefficient explaining the silicon oxide-to-sodium oxide ratio $(\mathrm{Si}{\mathrm{O}}_2∕{\mathrm{Na}}_2\mathrm{O})$ in an alkaline activator, and the silicon oxide-to-aluminum oxide $(\mathrm{Si}{\mathrm{O}}_2∕{\mathrm{Al}}_2{\mathrm{O}}_3)$ ratio and calcium content in the source material. The hydration products and microstructural characteristics of the AA pastes sampled from AA mortars were also investigated to evaluate the effect of the type and fineness of source material on the compressive strength of the AA mortar. The measured compressive strength development of the AA mortars was compared with an empirical equation for OPC concrete specified in ACI 209. The test results show that the flow loss and compressive strength development of the AA mortars are significantly dependent on the alkali quality coefficient and the fineness of the source material. Although no meaningful compressive strength develops in the FA-based AA mortars, the $28\text{day}$ compressive strength of the GGBS-based AA mortars having an alkali quality coefficient of 0.023 is comparable to that of the control OPC mortar, showing that the higher the fineness of GGBS, the higher the compressive strength of AA mortars. Scanning electron microscope image and x-ray diffraction clearly shows that the surface density of the calcium silicate hydrates gel in the GGBS-based AA pastes increased with the increase of fineness of the GGBS.

The need for safe and secure landfills for disposal of solid waste will always be present. As a groundwater pollution control mechanism, the use of some type of liner on these landfills is necessary, as in the absence of any liner the leachate contained within the moving water would eventually migrate to farther distances and may contaminate water supplies. According to the Environmental Protection Agency, a geotextile may be provided for short-time prevention of infiltration of the leachate in conjunction with a clay layer, which would provide the long-term minimization of leachate infiltration. From the laboratory study presented herein, it has been anticipated that a natural geotextile from jute impregnated with rot resistant bitumen may serve the required purpose of application under consideration. Further the investigation also indicates such a treated jute fabric may be applied as a fabric form to aid interception of the groundwater contaminated with pollutants like sulfate which might otherwise seep out and cause damage to the concrete structures.