Journal of Materials in Civil Engineering

Using experimental methods, this study presents the estimation of the dynamic and static (secant) elasticity modules of a prototype arch dam. These experimental methods are ambient vibration tests, uniaxial compression tests, and ultrasonic velocity tests. Implementation of the methods on a prototypical arch dam–reservoir–foundation model of the dam, constructed under laboratory conditions, allows estimation of the elasticity modules. Random impact loads excite the arch dam during ambient vibration testing, which creates response signals for measurement. Commercially available software transfers the signals, and processing those signals allows estimation of the experimental natural frequencies of the arch dam. Analysis of a three-dimensional (3D) finite element model (FEM) of the arch dam determines natural frequencies. The estimation of the elasticity modules of the arch dam arises from a comparison of the experimental and analytical frequencies. The uniaxial compression tests use several specimens of the fresh and hardened concrete of the prototype model, and those tests provide the compressive strengths and stress-strain relationships. The ultrasonic velocity tests apply several velocity measurements to the arch dam and foundation, resulting in estimation of the elasticity modulus from empirical equations related to concrete mix design, compressive strength, and velocity values. This study discusses the difficulties of the determination of the elasticity modulus and suggests that ambient vibration testing and the finite element method are useful for overcoming these difficulties.

During the past decades, in most industrialized countries, a large number of old buildings have been demolished and millions of tons of construction debris have been produced. Demolition wastes around cities have become a serious environmental issue and a threat to underground water quality and result in unpleasant views. Today, less than 5% of clay bricks taken from demolition sites are being separated and recycled, whereas the proportion of concrete waste being recycled is above 90%. This low rate of brick recycling is due to a lack of understanding about the performance of crushed brick material as aggregate in concrete or road base. In the case of concrete, the high water absorption of crushed brick and its relatively low compression strength in comparison with natural aggregate makes it difficult to meet traditional concrete specifications. The present research is an effort to investigate the properties of crushed clay bricks taken from demolition sites and experimentally evaluate the strength and durability characteristics of the concrete prepared using the crushed clay bricks. The experimental data reveal that, in spite of high porosity and absorption of recycled crushed brick, using this material as aggregate results in a semilightweight, durable, and low-permeability concrete.

Little research is available for perpendicular-to-grain connections in wood using multiple bolts. Experimental testing of single- and two-bolt connections was compared with predicted values from General Dowel Equations for Calculating Lateral Connection Values Technical Report 12. Two different laminated veneer lumber materials were tested with variable loaded-edge distances, and variable bolt sizes in both single- and two-bolt connections. Splitting failures, and crushing of main member and formation of a single plastic moment in the bolt were observed. Connection resistance increased as loaded-edge distance and number of bolts increased. Most design factors of safety representing the ratio of experimental strength to lateral design values were controlled by shear design provisions. Design factors of safety were greater at smaller loaded-edge distance with single bolt compared to other configurations. Further investigation of the design shear provisions may be needed. Yield theory overpredicted the connection strength at the lower loaded-edge distances because of splitting of the member before yielding occurred.

Previous research of structural composite lumber connections loaded perpendicular to grain has shown brittle failure by splitting. In previous testing, two different laminated veneer lumber (LVL) materials with single and two bolts in a row loaded perpendicular to grain were compared with fracture mechanics models proposed by Van der Put and Jensen and splitting capacity equations from Eurocode No. 5. Connection strength values of two-bolt connections were larger than single-bolt connections owing to the increased distance to the farthest fastener. The first LVL material (LVL-1) had significantly larger predicted capacity strength values than the other LVL material (LVL-2) for the same configuration owing to larger mode I fracture energy and tension perpendicular-to-grain strength values. A rederivation of the brittle failure constant $C_I$ specifically for LVL materials would improve performance of Eurocode No. 5 predictions. The different fracture models had improved connection prediction values when the tension perpendicular-to-grain strength of the main member was included in the models. This property appears to be more important than shear properties for splitting behavior.

The effectiveness of internal curing of high-strength self-consolidating concrete (SCC) using saturated recycled-concrete aggregates is examined in this study. Tests were performed on SCC using natural rock aggregate (NR-SCC) and recycled-concrete aggregate (RC-SCC). Fresh concrete tests included slump-flow, slump-flow with a J-ring, and L-box tests. All mixes tested were found to be highly flowable and stable. Strength tests included compression loading of cylinders and pushoff specimens. The RC-SCC was found to have superior compressive and frictional characteristics, indicating the beneficial effects of internal curing. However, the unconfined shear strength of NR-SCC was found to be superior to that of the RC-SCC. This was attributed to the fact that high-strength concretes fail in shear in planes that go through the aggregate rather than around it. The higher shear strength of the natural rock aggregate resulted in superior unconfined shear strength of the NR-SCC. However, the superior frictional characteristics of RC-SCC resulted in a reversal of this observation for the clamped (confined) specimens.

This paper presents the findings of an investigation using the finite-element method to predict the distribution of temperatures within a hydrating massive concrete element. The temperature distribution produced by the finite-element thermal analysis of the model is used in the finite-element structural analysis to quantify the maximum allowable internal temperature difference before cracking will initiate in the concrete. To verify the results obtained in the finite-element model, four different mixes of concrete, typical for use in mass concrete applications in Florida, were produced and each mix was used to make two large-scale $1.07\mathrm{m}\times 1.07\mathrm{m}\times 1.07\mathrm{m}$ ($3.5\mathrm{ft}\times 3.5\mathrm{ft}\times 3.5\mathrm{ft}$) concrete blocks. The mechanical and thermal properties of early age concrete used values obtained experimentally from the concrete used to construct the four sets of blocks. The temperature distributions produced by the model were shown to be very similar to those measured in the experimental blocks. Results suggest that reliance on a limiting maximum temperature differential to control cracking in massive concrete applications should be supplemented with a requirement for the presentation of an analysis showing the calculated stress response to the predicted temperature distribution within the concrete to ensure that the induced tensile stresses will not exceed the tensile strength of the concrete.

A life-cycle cost analysis (LCCA) was conducted on prestressed concrete bridge superstructures using carbon fiber reinforced polymer (CFRP) bars and strands. Traditional reinforcement materials of uncoated steel with cathodic protection and epoxy-coated steel were also considered for comparison. A series of deterministic LCCAs were first conducted to identify a range of expected cost outcomes for different bridge spans and traffic volumes. Then, a probabilistic LCCA was conducted on selected structures that included activity timing and cost random variables. It was found that although more expensive initially, the use of CFRP reinforcement has the potential to achieve significant reductions in life-cycle cost, having a 95% probability to be the least expensive alternative beginning at year 23–77 after initial construction, depending on the bridge case considered. In terms of life-cycle cost, the most effective use of CFRP reinforcement was found to be for an AASHTO beam bridge in a high traffic volume area.

Chloride-induced rebar corrosion is a common degradation process for concrete infrastructure, which is a practical concern for cold-climate states and coastal areas. In this work, numeric models based on the FEM are utilized to study service life of concrete structures subject to chloride ingress, where two models are utilized. The first one deals with multiple ionic species in the concrete pore solution, while the second one only accounts for the presence of chloride ions. The stochastic nature of model inputs is taken into consideration because each factor of interest is subject to random variabilities and inherent uncertainties. Specifically, the surface chloride concentrations and concrete cover depth follow the normal distribution; the diffusion coefficients obey the gamma distribution; the actual chloride threshold features the triangular distribution. The nonlinear partial differential equations (PDEs) to characterize the spatial and temporal evolution of ionic species are numerically solved, the results of which were utilized to elucidate the influence of various factors on concrete service life, such as mix design, surface chloride concentrations, cracking level, and coarse aggregate and concrete cover depth.

The assessment of pozzolanic activity is essential for estimating the reaction of a material as pozzolan. Natural pozzolans can be activated and condensed with sodium silicate in an alkaline environment to synthesize high performance cementitious construction materials with low environmental impact. In this paper, the pozzolanic activities of five natural pozzolans are studied. The correlation between type and chemical composition of natural pozzolan, which affects the formation of the geopolymer gel phase, both for the calcined and untreated natural pozzolans, have been reviewed. The improvement in pozzolanic properties was studied following heat treatment including calcinations and/or elevated curing temperature by using alkali solubility, and compressive strength tests. A model was developed to allow prediction of the alkali-activated pozzolan strength versus their chemical compositions, alkali solubility, and crystallinity.

This paper studies a compound material using a scanning electron microscopy (SEM) technique to enlighten its physical, mechanical, and thermal characteristics at a macroscopic level. The material is made of a gypsum matrix with phase change material as an additive, which improves the thermal performance (thermal energy storage capacity). Some reinforcing elements (polypropylene fibers and melamine formaldehyde) have been added to maintain its physical and mechanical performance. First, the morphology of the different aggregates of the compound material have been analyzed (microencapsulated paraffins, gypsum crystal, and polypropylene fiber) and subsequently the morphology of the compound material. A change in the gypsum morphology and a variation of hygrothermal behavior of the cast because of the decrease of porosity has been identified. It produces several types of adhesion—mechanical and electrochemical—among different aggregates. This explains its characteristics at a macroscopic level: a high thermal performance material with an improvement in its physical and mechanical characteristics, required for working as a paneling material in construction.

In this paper, state-dependent elastic characteristics of granular subgrade materials were investigated, assuming various field conditions. For this purpose, a series of resonant column tests were conducted. The test materials were cohesionless soils consisting of clean and silty sands with different fines contents. The effects of moisture content, overconsolidation ratio, relative density, and confining stress on the elastic modulus were analyzed. From the test results, it was observed that the initial shear modulus, $G_0$, decreases with increasing moisture content because of reduced particle contact friction. Higher fines content produced a more pronounced modulus reduction at the same moisture content. It was also found that the effect of fines content on $G_0$ becomes smaller as the relative density and confining stress increase. These results indicate that the moisture effect on $G_0$ is important at shallow depths such as subgrade layers. A modulus reduction factor was proposed, which can reflect the effect of the soil parameters on elastic modulus. A resilient modulus ($M_R$) model modified on the basis of the test results was proposed and finite-element analyses were conducted. Two case examples were selected from the literature to verify the proposed $M_R$ model. Predicted $M_R$ values obtained using the proposed model showed reasonable agreement with measured values from the selected case examples.

The advantages of utilizing recycled materials/byproducts in pavement construction are numerous. The reduction in landfilling resulting from the adoption of recycled materials in large quanitites primarily promotes their usage. Most of the recycled materials are used successfully throughout the world as embankment fill or subgrade foundation material. Although the utilization of the recycled materials/byproducts as pavement bases has been gaining increased acceptance, comprehensive geotechnical characterization of these materials is still lacking. In a research project, Limestone quarry fines (QF), which are a residue deposit produced from limestone quarries, and reclaimed asphalt pavement (RAP) aggregates, obtained from milling existing hot-mix asphalt (HMA) pavement layers, were characterized in both laboratory and field conditions. Before the usage of these materials as pavement bases, a series of laboratory tests were conducted to verify their engineering behavior and suitability. Shear strength and consolidation tests were performed to evaluate both strength and compressibility characteristics. Repeated load triaxial tests were conducted to obtain the resilient behavior of these recycled materials. Because the QF material exhibited both low strength and low moduli, cement stabilization was performed to enhance the material properties. The treated materials were then used as bases in test sections built as a part of the state highway. These test sections were instrumented and monitored for approximately 3 years. However, the long-term performance of the new materials is crucial for highways. Henceforth, numerical simulations were performed to predict the-performance of the test sections. This paper presents a summary of test results obtained from the laboratory, field, and numerical studies, and the results were analysed to evaluate the efficacy of these materials as pavement bases.

A numerical model developed in previous work by the authors is extended in this paper and used to evaluate the influence of several factors on the degradation of cementitious materials under the combined effects of external sulfate attack and calcium leaching. The previous model included (1) diffusion of ions in and out of the structure under concentration gradients and chemical activity gradients, (2) chemical reactions under local equilibrium condition assumption, and (3) damage accumulation using continuum damage mechanics. This paper extends the model by incorporating a continuum micromechanics based approach for assessing changes in elastic properties and strength of the structure attributed to chemical reactions. Two homogenization schemes combined with Eshelby’s equivalent inclusion method are used to estimate the mechanical properties of the structure that change with time because of dissolution and precipitation of solids. Sensitivity analysis is performed by using the improved numerical model to evaluate the effects of several external and internal factors (e.g., pH and composition of the external solution, and porosity and tortuosity of the material) on the degradation of the structure. It is found that the damage progression rate is mostly dependent on relative rates of sulfate ingress and calcium leaching. The relations between the factors and the damage progression rate are observed to be significantly nonlinear.

Recyclable fractions such as calcium and sodium aluminosilicates including zeolite sodalite (SOD) were obtained from hydrothermal treatment of autoclaved aerated concrete (AAC) waste material under addition of sodium aluminate. Three experimental series were performed using hydrothermal conditions at temperatures of 80°C and 180°C (autogeneous pressure) and AAC aluminate mass ratios of 0.8 and 2.0. Different solvents were applied in each series; whereas the reactions were carried out in water or 1-molar NaOH, a special two-step process was developed, starting with acid leaching of AAC (1-molar citric acid), followed by alkaline treatment of the whole slurry in 1-molar NaOH. Final products were analyzed by X-ray powder diffraction. Selected samples were further investigated by scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). The results exhibit model character for new ways of resource recycling of AAC.

The utility of waste fly ash, especially class F, in agriculture, geotechnical, and geoenvironmental applications have increased manifold. In most of these cases, precise determination of water retention characteristics (WRCs) of fly ash is mandatory. The WRC is generally expressed in terms of graphical relationship between water content and suction. There are not many studies that deal with the critical evaluation of fly ash WRC and its uniqueness. With this in mind, experiments were conducted on a Class F Indian fly ash using different measurement procedures. A tensiometer has been used for measuring matric suction in fly ash. This is primarily because of the fact that a cohesionless material like fly ash with its silt dominated particle size will not exhibit a very high range of suction. The results obtained in this study clearly indicate that the near saturation and desaturation portion of WRC could be determined using tensiometer measurements. On the basis of the results, the parameters of commonly used WRC equations have been reported for the fly ash. Analysis has been done to understand the influence of compaction conditions on fly ash WRC. It has been demonstrated that the WRC of fly ash established by using different procedures may not be unique, and initial compaction state influences the fly ash WRC.

This study examines the relationship between the aesthetic parameters of color and brightness and conversely, chemical-mineralogical composition in roofing slates from different Spanish and Portuguese quarries. Chemical and mineralogical characterization of 50 commercial types of roofing slates was carried out using X-ray diffraction and fluorescence, along with petrographical microscope examination. Reflectance color measurements were made using a portable spectrophotometer and analyzed by considering the Commission Internationale de l'Eclairage Lab (CIELAB) color parameters. Brightness was measured at an angle of incidence of 60° in accordance with ASTM D 523-95. The results showed that the slates were composed of quartz, mica, chlorites, and feldspar, along with some other minerals in lesser amounts. Organic matter (graphite) was present in concentrations between 0 and 4% and was closely related to the slate’s age. A strong correlation was found between an abundance of organic matter, and CIELAB coordinates $L^{*}$, $a^{*}$, $h_{ab}$ and brightness. Organic matter is the most influencing component of aspect (color and brightness) in the Iberian roofing slates color and, in a lesser extent, chlorite abundance. Chromatic effect of the chlorite is only perceptible in absence of organic matter, being this effect is more intense for the magnesic chlorite, clinochlore. Also, other correlations were found between chlorite and the slate’s main elements by means of CIELAB parameters. Thus, color quantification in roofing slates can be used as a first step to learning about their mineralogical composition.

Despite the fact that polymer-modified mortar can be widely used as a material for major construction projects, the extensive use of this promising material may be hampered because of not enough published data on its durability performance. This paper, based on a laboratory program, compares the engineering properties, over different aging, of three commercial polymer-modified mortars [styrene-butadiene rubber (SBR), polyacrylic ester (PAE), and vinyl acetate-ethylene (VAE)] and unmodified conventional mortar mixes exposed to different curing conditions. The results show that the SBR mixes appeared to possess better engineering properties than the PAE and VAE mixes, and a well-designed polymer-modified mortar mix can retain its engineering properties over a long period of time.

Statistical specifications for highway construction provide the means to measure important quality control attributes and ensure their compliance. The pay adjustments in these specifications reflect the amount of pay reduction and the optimized risk distributed between the owner agency and the contractor. The Kansas Department of Transportation (KDOT) has built a comprehensive database of as-constructed properties of materials for Portland cement concrete (PCC) pavements from the tests required as part of the quality control/quality assurance (QC/QA) program. Currently, KDOT pays incentives/disincentives for thickness and strength for PCC pavements. A practical performance model and composite index that include these two quality characteristics (thickness and strength) and air content for durability are needed to reflect the combined effect on the performance of PCC pavements. The main objectives of this study were to investigate the effect of levels of significance and lot size and to develop a practical performance model and composite index for PCC pavements in Kansas. Thirteen projects from four administrative districts of KDOT were selected for this study. Statistical analysis software was used for statistical analysis. Microsoft Excel was used to develop the performance models. Lot-wise comparison showed that QC means are significantly different in most of the cases. These cases increase with an increase in significance level. A practical performance model and composite index using quality characteristics (thickness, strength, and air content) have been proposed as an integral part of performance-related specifications in Kansas.

Porous metals have been used widely in aerospace and automobile industries due to their lightweight and reasonable mechanical properties. However, little research and experimental study has been carried out to explore the feasibility of extending porous metals in large-scale electromagnetic (EM) shielding applications. This paper begins with the EM modeling of the shielding effectiveness (SE) of common types of metal foams, and then the simulated results are validated experimentally. Finally, a shielded room is assembled and installed with modular metal foam panels. The SE of the installed shielded room is measured from 1–8 GHz, and promising shielding performance is demonstrated. With the comprehensive study, metal foam has been demonstrated to be an attractive option for large-scale architectural EM shielding applications without imposing structural loading issues.

Recycled aggregate (RA) obtained from crushed concrete rubble, instead of being stored, can be reused in building industry. An attempt has been made to study the possibility of reusing the recycled concrete aggregate from demolished structures in the place of fresh aggregate. Four series of mixes of control concrete with fresh aggregate and recycled concrete aggregate with three different ages of 5, 10, and 15 years were prepared for the present study and used with three different combinations, 0% fly ash, 20% fly ash, and 20% fly ash with super plasticizer. The basic properties of aggregates, such as water absorption and specific gravity, mechanical properties, such as abrasion resistance, effect, and crushing values were considered. Workability of fresh concrete and strength parameters of hardened concrete, such as compressive strength and tensile strength, were studied. The preceding properties were tested for three different periods of curing of 7, 14, and 28 days. All these mixes were designed for M25 grade of concrete. In the present work, a comparison was made between the results of a laboratory investigation on various physical properties of concrete made with recycled aggregate concrete with fresh aggregate concrete and found that the results are encouraging to use concrete with RA.