Journal of Materials in Civil Engineering

Oil sand is a generic name given to natural deposits of bituminous sand materials that are mined for crude oil production. These materials are currently used as subgrade materials of temporary and permanent roads in oil sand fields for operating large capacity haul trucks and shovels. This paper focuses on determining in laboratory the resilient behavior of three oil sand materials with bitumen contents of 8.5, 13.3, and 14.5% by weight. The resilient modulus $\left(M_R\right)$ properties were obtained using a newly established repeated load triaxial test procedure. From the test results, nonlinear $M_R$ models were successfully developed in the forms of K-theta, Witczak-Uzan, and the mechanistic empirical pavement design guide (MEPDG) models to properly characterize temperature and stress dependent resilient behavior. The modified K-theta model predicted the overall $M_R$ dependency on applied stress states and temperature quite satisfactorily for all the three oil sands when compared to the modified Witczak-Uzan and MEPDG models. The $M_R$ results presented and the models developed can be practically used to estimate the field stiffness behavior of oil sands as subgrade materials.

The effects of steel fiber alignment and high-volume mineral admixture replacement [Class C fly ash (FA) and ground granulated blast furnace slag (GGBS)] on the mechanical properties of SIFCON (Slurry Infiltrated Fiber Concrete) have been investigated. Ordinary portland cement was replaced with 50% (by weight) FA or GGBS in SIFCON slurries, and two different steel fiber alignments (random and oriented in one direction) were used. Test results showed that FA and GGBS replacement positively affected mechanical properties (compressive and flexural strength and fracture energy) and fiber alignment is an important factor for superior performance. Binary combination of improved matrices (low water/binder ratio and mineral admixture replacement) and proper fiber orientation enhances mechanical performance, particularly flexural properties of SIFCON. Flexural strength and fracture energy of this composite are 138 MPa and 195,815 N/m, respectively. Scanning electron microscope investigations revealed tobermorite-like structures having different morphology such as foiled, fibrous, and honeycomb with low Ca/Si ratio after autoclaving. Mercury porosimeter tests showed the decreasing of total porosity and pore refinement with FA or GGBS.

The uniaxial monotonic compressive behavior of tuff masonry has been studied by laboratory tests carried out along the directions parallel and orthogonal to the mortar bed joints. Based on the experimental results, different nonlinear stress-strain models have been defined for each loading direction to account for the orthotropy of masonry and to describe strain-softening behavior. Maximum likelihood, mean, and characteristic stress versus strain diagrams have been derived by means of different techniques of statistical analysis to be employed in the structural analysis of both new and existing constructions. Two different analytical models have been obtained via nonlinear regression analysis for defining stress-strain curves for tuff masonry to be used in the current design/assessment procedures. Such constitutive models require only the peak compressive strength and the relevant yielding strain as input data. The allowable strain ductility of masonry can also be explicitly taken into account. Strength, deformability, and ductility parameters have also been identified to run equivalent linear analyses. To this end, simple relationships are provided to define both Young’s and shear moduli from compressive strength.

Longitudinal joints between lanes of hot-mix asphalt (HMA) pavements are commonly susceptible to moisture damage and other failures. In 2006, the Tennessee Department of Transportation (TDOT) identified longitudinal joint failure as one of the major distresses for local HMA pavements. It was determined necessary to evaluate available practices and technologies to reduce longitudinal joint failure. This paper presents the results from a field project in Tennessee constructed with seven different longitudinal joint construction techniques. These techniques could be divided into three major categories: joint adhesives including an anionic emulsion and a polymerized emulsion commonly used by the TDOT, a hot-applied high-polymer rubber, and a high-polymer emulsion; joint sealers including a polymerized maltene emulsion and a polymerized agricultural oil; and infrared joint heater. Laboratory tests were conducted on the field cores taken from the test sections constructed with these techniques. Based on the different mechanisms of these techniques, the following laboratory tests were employed: air void content, permeability, indirect tensile (IDT) strength, and water absorption tests. Field cores were also scanned with the X-ray computed tomography to investigate the effect of infrared heating on air void distribution. The test results showed general consistency in the joint quality; i.e., the lower the air void content, the lower the permeability and the higher the IDT strength. The infrared heater exhibited the best effectiveness in improving joint quality among all the joint construction techniques used in this study.

Assessment of light-frame wood structures for wind and seismic loadings requires engineering information about the wood materials and connections in the subject building. The knowledge base can be developed by inspection and further enriched by knowledge of age effects on materials and connection properties. Nineteen wood-frame structures built between 1905 and 1970 and scheduled for demolition were located through local municipal building departments and sampled for wood materials and nail connections prior to demolition. The project plan was to evaluate the materials from the buildings while watching for trends in materials over time, calculate the expected connection capacity using the materials’ test results, and then compare the calculated allowable connection capacity to tests of single-fastener connections extracted from the same buildings. Insect damage and fungal deterioration were present in many of the structures and were avoided when sampling for test specimens. Inferences are not made regarding the effect of biological deterioration and climatic conditions on the wood material properties. The Douglas-fir studs and plank-shiplap sheathing extracted from the source structures had an average dowel bearing strength $\left(F_{\text{e}}=29\text{MPa}\right)$ that was statistically similar to the National Design Specification for Wood Construction table value for a specific gravity (SG) of 0.47 for dowels with diameters of less than 6.35 mm. The nails had average bending-yield strength of 671 MPa as compared to the contemporary reference value of 690 MPa for nails in this diameter class. No time trend was observed in the SG of the wood or the bending-yield strength of the nails. In general, the connection tests yielded good agreement between the European yield model equations and calculated connection capacity. Validation of the material conditions in older structures requires cautious inspection. The inference from this investigation as related to rehabilitation is that nailed connections without deterioration due to decay, insects, temperature, and/or moisture perform in a manner consistent with the current design standard.

Stone-on-stone contact of the coarse-aggregate fraction is one of the main characteristics of permeable friction course (PFC) asphalt mixtures that is required to provide adequate resistance to both raveling and permanent deformation. Currently, stone-on-stone contact is determined by comparing the air voids content in the coarse aggregate (VCA), assessed in both the dry-rodded condition $\left({\text{VCA}}_{\text{DRC}}\right)$ and the compacted PFC mixture $\left({\text{VCA}}_{\text{mix}}\right)$ . The underlying assumption is that the coarse aggregate of a compacted PFC mixture with ${\text{VCA}}_{\text{mix}}$ equal to ${\text{VCA}}_{\text{DRC}}$ would develop a stone-on-stone contact condition equivalent to that existing in the dry-rodded aggregate. This study focused on proposing enhancements for the quantitative determination of stone-on-stone contact of PFC mixtures. The assessment supported on both laboratory testing and application of the discrete element method and image analysis techniques, led to recommendation of a criterion to determine the breaking-sieve size. In addition, verification of stone-on-stone contact using a maximum VCA ratio of 0.9 was recommended to ensure the design and construction of PFC mixtures with fully developed stone-on-stone contact.

Concrete block paving (CBP) is one of the predominant road construction methods used in most of the developing counties due to its economic adaptability. It has emerged as a cost-effective road construction method suitable for different ground conditions but this has yet to be developed as a full fledged technique because of the dearth of technical expertise and knowledge. The aim of this research is to evaluate the state of support conditions and to discover effective patterns which can be used to improve concrete block paving technology. Development of a laboratory scale CBP model and evaluation of support conditions were mainly considered in the initial stage of this study. A developed laboratory scale CBP model was used to measure deflection basin with four different load arrangements. A three-dimensional finite-element model was built to measure elastic deflection behavior of concrete block pavement with SAP2000 structural analysis software. This finite-element model was used to simulate field conditions of a concrete block pavement and it was verified with the deflection values observed in a laboratory scale model. The verified analytical model has been used to perform a parametric study in order to determine necessary improvements for weaker support conditions and find effective laying arrangement in the concrete block paving. Developed design charts and field observations can be used to propose subgrade improvement methods for weaker support conditions. The writers recommend concrete block laying work for low volume roads with subgrade strength higher than 10% CBR. The results indicate that herringbone bond pattern performed well under effect of vertical loading and breaking action. It has the capability to develop better interlocking action in CBP work.

An experimental testing protocol was developed to compare the relative effectiveness of chemical dust palliatives. The methods and application simulate field construction using commercial spray components. The test devices were constructed to simulate wind speeds and conditions for rotary wing aircraft. Fifteen chemical dust suppressants were evaluated using this methodology. These commercial products were applied topically to prepared soil specimens and allowed to cure for one and 48 h. Effectiveness was determined from the relative mass loss of the soil samples from erosion when samples were subjected to an air impingement device. An optical dust sensor was installed in the test device to measure airborne dust concentrations as an additional method for quantifying performance. A method to disturb the treated soil surface was also introduced to simulate the effect of traffic. Select application rates of the palliatives were used in sample preparation to identify minimal quantities necessary for the desired performance. The testing equipment and processes provided a rapid screening methodology for selecting potential dust palliatives. Results indicated good correlation between erosion and airborne dust concentrations with higher application rates and complete curing of materials demonstrating reduced dust levels. The traffic simulation test identified products with a propensity to form surface crusts that may be disturbed by traffic.

This paper deals with two aspects of characterization of the fracture process zone (FPZ) in concrete beams. A comparative study is done between acoustic emission (AE) and scanning electron microscope (SEM) to understand the microlevel aspect of the FPZ in concrete beams. SEM analysis, is mainly based on the preparation and analyzing samples which are considered as being a very important part (poor preparation techniques can lead to erroneous diagnosis of the concrete study). On the other hand, an AE is a localized and quick release of strain energy in a stressed material. The released energy causes stress waves, which propagate through the specimen. These waves can be detected at the specimen surface and analyzed to evaluate the magnitude and the nature of damage. The results obtained from the two experimental studies have shown that there is a small divergence between experimental results (SEM and AE). This may be related to some details during the sample analysis.

This study investigated the use of two kinds of waste from landfills, calcium carbide residue and fly ash, as a low ${\text{CO}}_2$ emission concrete binder. Calcium carbide residue is a by-product of an acetylene gas production process, and fly ash is a by-product of a thermal power plant. Ground calcium carbide residue (CR) was mixed with original fly ash (OF) or ground fly ash (GF) at a ratio of 30:70 by weight and was used as a binder to cast concrete without portland cement. The effects of fly ash finenesses and water to binder $\left(W/B\right)$ ratios of CR-OF and CR-GF concretes on setting times, compressive strength, modulus of elasticity, and splitting tensile strength were investigated. The results indicated that CR-OF and CR-GF mixtures could not only be used as a new binder in concrete but could also help reduce environmental problems associated with ${\text{CO}}_2$ emissions. Without the use of portland cement, CR-GF concrete yielded compressive strengths of 28.4 and 33.5 MPa at 28 and 90 days, respectively. In addition, lower $W/B$ ratio and high fineness of fly ash produced higher compressive strength of the concrete. The hardened concretes produced from CR-OF and CR-GF mixtures had mechanical properties similar to those of control samples made from normal portland cement concrete.

The work presented in this paper is a part of a comprehensive research project aimed at developing and testing a system for strengthening historical buildings. The system is composed of a combination of textile mesh and mortar. Representative wall specimens were tested for their out-of-plane flexural behavior under static and cyclic loadings. The parameters investigated include the types of masonry wall (concrete block, sandstone, and brick), mortar (natural lime and cement-based), and textile (bitumen coated E-glass, basalt, or coated basalt fibers). Companion specimens, strengthened using a steel wire mesh, were also tested for comparison. All textile-mortar reinforced masonry (TRM) wall specimens failed in a combination of transverse detachment of the textile-mortar matrix due to the transverse displacement of the blocks relative to each other, and combined transverse shear-tension fracturing of the textile fibers. Regardless of the mode of failure, the TRM specimens developed a substantial increase in their out-of-plane load and displacement capacities under static loading, and low stiffness and strength degradation, and considerable displacement capacities under cyclic loading. The wire mesh-mortar reinforced masonry specimens developed the highest load capacity but were the least ductile when compared to the TRM specimens.

In this note, a number of empirical models available in the literature of the complete stress-strain curve for unconfined high-strength concrete under uniaxial compression are reviewed and investigated using the published experimental data. Based on the investigations, a new empirical model with emphasis on the softening branch is proposed to generate the complete stress-strain relationship for high-strength concrete. An application of the new empirical model to published experimental data on normal weight concretes over a wide strength range demonstrates that the present model gives a good representation of the mean behavior of the actual stress-strain response.

This paper uses the time-depth dependent chloride diffusion coefficient obtained from the analytical solution of the nonlinear chloride diffusion equation at nonsteady state to propose a new life prediction model of concrete structures exposed to a chloride environment. The proposed theoretical model treats the chloride diffusion coefficient as a variable dependent on time, depth, and chloride content of concrete rather than a constant as normally assumed. Detailed step-by-step guides to the practical application with this model are provided. Based on the illustrated example, the comparison of the service life prediction calculated by this model and the well-known LightCon model is addressed. However, the proposed model should remain to be verified by using long term field data for the potential failure impacts in the durability design of concrete structures.

Owing to their importance to the structural analysis and evaluation of cement-based materials, it is essential to determine the mechanical properties of cement paste. This paper presents a simple three-step analytical scheme for predicting the elastic moduli of hardened cement paste. In this scheme, hardened cement paste is modeled as a multiphase composite material, composed of unhydrated cement, C-S-H, CH, and capillary pores and further represented by five two-phase composite spheres. The elastic moduli of hardened cement paste are obtained in terms of the volume fractions and elastic moduli of unhydrated cement, C-S-H, CH, and capillary pores by the three-step scheme. Finally, the validity of the three-step scheme is verified with three independent sets of experimental data. The paper concludes that, when the water-cement ratio is in the range of 0.4–0.6, the simple three-step analytical scheme presented in the paper can predict the elastic moduli of hardened cement paste with an average relative error smaller than 8%.

Bamboo is viewed as a sustainable and highly renewable material that may be grown in any temperate climate zone. Interest in the engineering properties of bamboo and the use of bamboo in engineered construction is growing. Although often having superior mechanical properties than readily available sawn timber, bamboo, being largely an unidirectional fibrous material, is very susceptible to longitudinal splitting. Despite being the dominant limit state in many applications, very little previous work has addressed the characterization of bamboo splitting failure. The present research focuses on the development of a split pin test method for characterizing the splitting strength of bamboo culms. The proposed split pin test uses a full culm section test, thereby eliminating some of the complexities of partial culm tests. Results of a pilot study of the split pin test having similar specimens with different split pin diameters yielded consistent results and variations less than that of the previously standardized direct shear test. In order to demonstrate the validity of the proposed test method, a series of tests was performed on samples of Tre Gai (Bambusa stenostachya Hackel) bamboo.