Journal of Materials in Civil Engineering

High strength concrete (HSC) with highly desirable structural properties can lead to significant cost savings in heavily loaded lower story columns of concrete structures. Its use has however, been limited by a concern regarding an increased brittleness compared to normal strength concrete. It is well established that the ductility of HSC columns can be increased by confinement of the core of concrete columns by lateral steel reinforcement. Confining pressure applied by the reinforcement is a function of the lateral strain of concrete. Therefore establishing axial stress, axial strain, and lateral strain relationships is a timely concern. Based on shear failure of concrete, a simple strain-based model is proposed in this paper. It is developed using prevailing test results for HSC with active confinement.

Blended calcium sulfate (BCS), a by-product gypsum blended with lime or limestone, has been used as a base course material on some of Louisiana’s highways. Although BCS has high strength in dry conditions, its poor water resistance has largely limited its application in highway construction. A series of laboratory tests identified the factors that dictate the strength development of nonstabilized BCS. BCS was subsequently stabilized with various cementing agents to improve its water resistance. The mechanical properties of stabilized BCS, including its unconfined compressive strength, water resistance, volumetric expansion, and durability, were also evaluated. Finally, recommendations were made for the application of stabilized BCS as a base course material.

Geopolymer composites reinforced with short polyvinyl alcohol (PVA) fibers have been manufactured using the extrusion technique. The extruded products were thin plates with $6\mathrm{mm}$ thickness. It was demonstrated that short fiber reinforced geopolymer composites (SFRGCs) could be extruded without additional rheological modifier. Bending tests have been conducted with the extruded samples to investigate their mechanical properties. The fiber failure patterns in SFRGCs with various formulations were examined by scanning electron microscope and energy dispersive x-ray analysis techniques. The experimental results showed that the addition of PVA fiber could largely increase the ductility of SFRGCs, resulting in fiber failure modes changing from brittle to ductile. The effects of varying the amount of fly ash on the flexural behavior of various SFRGCs were also investigated. The SFRGCs incorporating small percentage of fly ash showed higher flexural strengths but smaller defections, while the SFRGCs incorporating a large percentage of fly ash had lower flexural strengths, but larger deflections. This could be attributed to the change of the bonding between fiber and matrix that led the change of failure mode from fiber fracture to fiber pullout.

A new simple test device is proposed to directly measure the critical temperatures for thermal cracking of asphalt binders. Using the dissimilar coefficients of thermal expansion for asphalt binders and common metals, the asphalt binder cracking device (ABCD) was developed to simulate thermal cracking of asphalt pavement in the laboratory. The ABCD consists of a metal ring, a strain gauge glued to the inner side of the ring, an environmental chamber, and a data acquisition system. Development of thermal stress within the asphalt binder during cooling is monitored by the strain gauge and the cracking temperature can be directly determined from the strain reading. A simplified theoretical analysis of the ABCD shows that the effects of thermal contraction of the asphalt binder and aggregate and the elastic properties of aggregates on thermal cracking could be reproduced in an ABCD test by adjusting the specimen and device geometries. Preliminary test data support the concept of the ABCD.

Class F fly ash cannot be used alone in soil stabilization applications as it is not self-cementing. An activator such as Portland cement or lime must be added to produce cementitious products often called pozzolan stabilized mixtures. The developed mixture must possess adequate strength and durability, should be easily compacted, and should be environmentally friendly. Roadways have a high potential for large volume use of the fly ash stabilized soils. The main objective of this study is to investigate the use of Class F fly ash amended soil–cement or soil–lime as base layers in highways. A battery of tests were performed on soil–fly ash mixtures prepared with cement and lime as activators. Unconfined compression, California bearing ratio, and resilient modulus tests were conducted. Finally, required base thicknesses were calculated using the laboratory-based strength parameters. Results of the study show that the strength of a mixture is highly dependent on the curing period, compactive energy, cement content, and water content at compaction. Lime treatment does not provide sufficient strength for designing the mixtures as highway bases. Freeze–thaw cycles do not have any detrimental effect on cement-treated mixtures. A power function in terms of bulk stress used for granular soils can accurately model the resilient moduli. Most of the factors considered have an impact on the thickness of the base layer.

The paper presents results of an investigation carried out to study the fatigue life distribution of plain and steel fiber reinforced concrete with different fiber volume fractions and aspect ratios for various levels of the applied fatigue stress. An extensive experimental investigation was planned in which 210 flexural fatigue tests and 84 complementary static flexural tests were conducted on prismatic plain concrete and fibrous concrete specimens of $100\times 100\times 500\mathrm{mm}$ size under three point loading in an MTS closed loop testing machine. Two types of crimped-type flat steel fibers with $25\times 2.0\times 0.6\mathrm{mm}$ and $50\times 2.0\times 0.6\mathrm{mm}$ , corresponding to fiber aspect ratios of 20 and 40, respectively, were used at each of the fiber volume fractions of 0, 1.0, 1.5, and 2.0%. It has been observed that the probabilistic distribution of fatigue life can be approximately modeled using the two-parameter Weibull distribution with statistical correlation coefficient exceeding 0.90. The shape parameter of the Weibull distribution for the fatigue life of concrete is different for different stress levels and fiber aspect ratios. The present study indicates that the probabilistic distribution of fatigue life of concrete depends on the level of applied fatigue stress, fiber volume fraction, and the aspect ratio of fibers. The graphical method, the method of moments, and the method of maximum likelihood estimation have been used to obtain the distribution parameters of the Weibull distribution. These three methods are shown to yield similar values of distribution parameters for the present fatigue data.

Cast-concrete hollow blocks, solid blocks, and paving stones were produced at a manufacturing plant by replacing up to 45% (by mass) of portland cement with fluidized bed combustion (FBC) coal ash and up to 9% of natural aggregates with wet-collected, low-lime, coarse coal-ash (WA). Cast-concrete product specimens of all three types exceeded the compressive strength requirements of ASTM from early ages, with the exception of one paving-stone mixture, which fell short of the requirement by less than 10%. The cast-concrete products made by replacing up to 40% of cement with FBC ash were equivalent in strength (89–113% of control) to the products without ash. The abrasion resistance of paving stones was equivalent for up to 34% FBC ash content. Partial replacement of aggregates with WA decreased strength of the products. The resistance of hollow blocks and paving stones to freezing and thawing decreased appreciably with increasing ash contents. The cast-concrete products could be used indoors in regions where freezing and thawing is a concern, and outdoors in a moderate climate.

An experimental study is reported aimed at determining stiffness and strength of laterally loaded dowel-type fastener joints in Australian grown pine. Emphasis is on joints in Radiata pine lumber or glued-laminated (glulam) timber, and Slash pine lumber. Information was collected in a manner that makes it useful for load and resistance factor design. It was found that characteristic “one-fastener” design capacities of joints are most reliably based on the yield load rather than the ultimate load, and that for practical purposes behaviors of joints in Radiata pine and Slash pine can be regarded as identical.

By using both the pseudoelasticity and strain self-sensing ability of shape memory alloy (SMA) material, an innovative smart SMA-based damper can be developed. This damper has comprehensive energy dissipation and strain self-sensing abilities (i.e., electric resistance versus applied strain relationship) simultaneously. Before shaking table test on a building installed with such SMA-based dampers, the tests were conducted on the hysteresis stress–strain-electric resistance relationship of SMA wires (diameter $1.2\mathrm{mm}$ ). These tests were carried out under sinusoidal excitations with different loading frequencies at different ambient temperatures, to investigate the energy dissipation ability and strain self-sensing property of SMA wires. The sensitivity coefficient of electric resistance versus applied strain of the SMA wires was identified to be 5.948 from the test results, which is larger than that of the conventional strain gage and is independent of loading frequency. The experimental results indicate that the pseudoelastic hysteresis loops of the SMA wires are dependent on loading frequencies, particularly in the case of lower frequency. Further tests aimed at revealing the mechanism of the strain rate dependence of pseudoelasticity of SMA wire were conducted. The results indicate that the phase transformation temperature is dependent on strain rate, i.e., both the martensitic phase transformation finish temperature and the austenitic phase transformation start temperature decrease with increasing of strain rate. Based on the results of these tests, a one-dimensional strain rate dependent constitutive model of SMA wires was developed. This model predicts pseudoelastic behavior of SMA under various loading frequencies. Finally, a numerical simulation using the proposed model was performed, and the simulated pseudoelastic hysteresis loops agree well with test results presented not only by writers but also by other researchers.

Fly ash can be effectively used as compacted or flowable fill material in the construction of structural fills for building foundations, embankments, base and subbase courses for highways and railroads, dikes, levees, bridge abutments, and landfill cover in lieu of conventional earth materials. In this study, high volume fly ash cement paste composite formed of various combinations of fly ash, cement, lime, silica fume, and chemical admixtures has been examined in terms of its physical (dry unit weight, void ratio, apparent specific gravity, linear shrinkage), mechanical (unconfined compressive strength, flexural strength), and durability properties (hydraulic conductivity, soundness by use of sodium sulphate) at 0, 100, and $200\mathrm{mm}$ slump values. The results indicate that the cement paste, providing certain advantages over conventional fill materials with its lower unit weight, higher strength, and higher volume stability can be designed for any required engineering performance for use in the construction of compacted to self-compacting structural fills and promises high volume fly ash utilization with low technology requirements avoiding scarce use of raw resources.

This paper reports on the results of the investigation on concrete specimens made with different plain (ASTM I, II, and V) and blended cements incorporating different percentages of volcanic ash (VA) up to 30% (as cement replacement). The specimens were exposed to marine environment for a period of $1\text{year}$ . A set of combinations with mixing water and initial curing conditions were studied such that cast in situ and precast conditions of concrete in marine environment were simulated. It is found that blending of Types I and II cement with VA (between 10 and 20%) has shown better resistance against seawater attack than Type V cement with low ${\mathrm{C}}_3\mathrm{A}$ . The performance of VA based concrete mixtures is assessed based on the strength reduction criteria and is supported by data from rapid chloride permeability, porosity, and differential scanning calorimetry tests. It is recommended that Type I cement with VA content between 10 and 20% would be a better choice in a marine environment. Results also showed that the use of precasting could mitigate the deleterious effect of marine environment on concrete specimens considerably rather than casting in situ.

The prediction of moisture diffusion within the cementitiously stabilized materials is essential for assessing their shrinkage and associated cracking potential. A theoretical approach was presented for modeling of moisture loss during drying of cementitiously stabilized pavement materials. The moisture loss process was characterized by isotropic nonlinear diffusion theory. Laboratory experiments were undertaken to measure the material properties and characteristics that included the coefficient of moisture diffusivity and the humidity isotherm. Independent laboratory tests were undertaken to validate the theoretical approach adopted, and the experimental and predicted results displayed close agreement. The laboratory results indicated that as the drying progressed, the rate of moisture loss became slower, which can be explained by the reduction in the coefficient of moisture diffusivity with the decrease of moisture content. The humidity isotherms measured also indicated that the stabilized pavement materials appear not to dry significantly further after they reach a pore relative humidity of about 65%.

Experiments were performed to investigate the impact on the moisture resistance of paving mixtures of the addition of hydrated lime directly to the asphalt prior to mixture preparation. Moisture resistance was evaluated on mixtures prepared using a strategic highway research program asphalt and limestone and granite aggregates by freeze–thaw cycling of the mixtures in water. Other parameters investigated in addition to hydrated lime that might affect moisture damage were oxidative aging and the addition of a model ketone to the asphalt. After the freeze–thaw cycling experiments, the specimens were subjected to selective solvent extractions to isolate the polar organic materials strongly adsorbed on the aggregate surfaces. Results of the extraction experiments indicate that the composition in the asphalt–aggregate interfacial region may change during repeated freeze–thaw cycling. Oxidative aging improved the resistance of the mixtures to moisture damage. Hydrated lime, when added to the asphalt prior to preparation of the mixtures, dramatically improved mixture resistance to moisture damage for both aggregates. The model ketone containing no additional polar chemical functionality reduced moisture damage resistance, suggesting that the apparent resistance of ketones formed in asphalt to displacement from the aggregate by water reported in previous studies resulted from strongly adsorbed, moisture resistant chemical groups contained on the same component as the ketone functional group. Results from the present study support previous work indicating that carboxylic acids play a major role in determining the moisture sensitivity of pavement mixtures.

In the use of cutoff walls, long-term stability, no gaps, and flexibility to the earth deformation are crucial to minimize the permeability $\left(k\right)$ . Soil–bentonite mixtures meet such requirements, if more than $70\mathrm{kg}$ of bentonite per $1{\mathrm{m}}^3$ of soil could be homogeneously mixed with soil in situ. When making cutoff walls by using the mixing in place method instead of the slurry trench method, bentonite should be added to soil in a slurry state for homogeneous mixing; however, $20\mathrm{kg}∕{\mathrm{m}}^3$ of bentonite would be the largest amount by bentonite–water slurry. To achieve increased bentonite content, the utilization of hydrophilic organic solvent such as ethanol is an effective option. This paper tested a large-scale model to investigate the cutoff property of bentonite wall using ethanol, and to clarify the influence of ethanol to groundwater. The wall had sufficient cutoff ability $(k=4.0\times {10}^{-10}\mathrm{m}∕\mathrm{s})$ , and pumping the groundwater properly could minimize the ethanol diffusion in the subsurface.

The bond strength between masonry units and mortar has been of considerable interest to researchers for some time. The flexural bond strength of masonry in particular is needed for the design of masonry walls subjected to horizontal forces applied normal to the face of the wall, such as wind forces. Researchers and standards have suggested different kinds of specimens and test procedures to determine the flexural bond strength. These include the test on wallettes (small walls), the bond wrench test, the Brench test, the direct tensile test, and the crossed couplet test. Each of these tests has its own drawbacks and problems. This paper presents a test method to determine the flexural bond strength, $f_{fb}$ , by bending. The test could be used for laboratory research to investigate the many factors affecting bond strength and also for deriving design values for masonry standards. The specimen is constructed from two brick units in a Z-shaped configuration, and three-point loading induces a flexural bond failure parallel to the bed joint. Three different types of clay brick, one calcium silicate brick, and three different types of mortar were used in the experimental program. The results derived show that the proposed new specimen and test procedure are capable of determining the flexural bond strength easily and accurately.

Compressive strength is considered to be the paramount property of cement. However, according to the standard test procedure, the results of a compressive strength test on cement can be known only after $7$ or $28\text{days}$ . To overcome this difficulty, a dimensional analysis method for predicting the $28\text{-}\text{day}$ compressive strength of 53-grade cements is presented in this paper. This method incorporates the modified Buckingham-pi theorem to formulate a general equation by using only two experimental results. A unique trial-and-error procedure is presented that generates the universal dimensional analysis formulation, wherein one of the experimental data sets, called the control point, generates the dimensional analysis equation, whereas the other data set, the check point, is used to validate the already formed dimensional analysis equation. The results of dimensional analysis are then compared with the available experimental results. The comparison shows the validity of the method.