Journal of Materials in Civil Engineering

Existing methods of estimating long-term corrosion loss are almost always based on time, with separate models for different atmospheric conditions (i.e., industrial, urban, rural, marine). Such models do not account for variation in environmental conditions, even though it is known that corrosion loss varies significantly with different environmental factors. This research involved the formulation, calibration, and validation of models that show the effects of the environment on corrosion for four materials (carbon steel, zinc, copper, and aluminum) and two types of specimens (flat and helix). The models were formulated with a structure that yields rational effects for four environmental variables: time-of-wetness, sulfur dioxide, salinity, and temperature. ISO CORRAG data obtained from 51 test sites in 13 countries was used to calibrate the coefficients of the eight models. The prediction accuracy of the models was assessed using goodness-of-fit statistics. The correlation coefficients ranged from 0.532 to 0.834 for the models. Using data independent of the calibration data, the models were validated. The results of validation indicate that the models are reliable for use in a broad range of conditions or locations. The temporal variation in corrosion loss for each of the four environmental factors is also discussed. Both calibration and validation suggest that the environmental components of the models can be used with other time-dependent corrosion models to assess the effects of variation in environmental conditions.

Slender recycled plastic pins (RPPs) can be used to stabilize earthen slopes by driving the RPPs into the face of the slope to intercept the sliding surface and “pin” the slope. The RPPs will be subjected to lateral (bending) forces, and their ability to resist deformation will strongly influence the success of the RPPs for stabilizing slopes. Arrhenius modeling was used to predict the time for the RPPs to reach creep failure. Engineering properties and strain rate effect of four different types of RPPs were evaluated and are reported in this paper. Arrhenius modeling showed creep failure ranged from $50\text{to}\mathrm{3,900}\text{years}$ at field temperature and stress levels. Compressive strengths ranged from $11\text{to}20\mathrm{MPa}$ and compressive moduli from $580\text{to}\mathrm{1,280}\mathrm{MPa}$ at 1% strain, while flexural strengths ranged from $9\text{to}25\mathrm{MPa}$ and flexural moduli from $620\text{to}1675\mathrm{MPa}$ at 1% strain.

Large numbers of soil-cement block masonry buildings exist in India and many other countries. The paper deals with an experimental study on the influence of soil grading on the characteristics of soil-cement blocks and shear-bond strength of soil-cement block masonry triplets. Influence of clay content of the soil-cement block on strength, absorption and durability characteristics, and interfacial mortar-block bond strength has been examined. Some of the major conclusions of the study are: (1) optimum clay content leading to maximum strength is in the range of 14–16%; (2) saturated water content of the blocks increases with increase in clay content of the block; (3) initial rate of absorption decreases with increase in clay content of the block; (4) weight loss after ASTM wire scratch test is minimum when the clay content of the block is about 16%; and (5) optimum clay content for the highest modulus for the blocks and for highest shear-bond strength is about 16%.

This study attempts to develop a recyclable, high strength, ecological soil material that does not consist of cement and is unpolluted, named high-strength ecological soil material (HSESM). The production of HSESM involves calcinating soil minerals to very high temperatures, adding active minerals, using concentrated alkali to disintegrate silicate and aluminate monomers, and, using ${\mathrm{Na}}_2{\mathrm{SiO}}_4$ to repolymerize the soil material to a polymer that resembles the structure of zeolite. The results of the study show that the 28-day compressive strength of high strength ecological soil material exceeds $20\mathrm{MPa}$ , with flexural strength in the order of 10% of the compressive strength. The permeability of this material is categorized as moderate level according to ASTM C 1202-97. Discarded HSESM can be reverted back to powder using jaw crushers and mechanical grinding facilities. Through the four steps described previously, the recycled HSESM can be reused again.

Corrosion of concrete sewer pipes by sulfuric acid attack is a problem of global scope, leading to multibillion dollar losses each year. However, research is still needed to better understand the mechanisms of sulfuric acid attack on concrete and the related effects of concrete mixture design parameters. In this paper, the combined effect of wetting-drying cycles and concrete mixture design parameters including cement content, water/cement (w/c) ratio, and coarse aggregate content on the resistance of concrete to sulfuric acid was investigated. Specimens from various concrete mixtures were soaked in sulfuric acid solutions with pH of 0.3, 0.6, 1.0, 1.5, 2.0, 2.5, and 3.0. The mass loss of concrete specimens due to immersion in sulfuric acid and wetting-drying cycles was used as a measure of concrete degradation. For specimens that experienced no mass loss due to low concentration of sulfuric acid, the thickness of the gypsum layer that formed on specimens’ surface was measured on thin sections using transmitted light microscopy. The effect of exposure area/volume ratio of concrete specimens on their mass loss was also investigated. Results show that the mass loss of concrete specimens immersed in sulfuric acid solutions with $\mathrm{pH}<1.5$ increased as the cement content of the mixture increased and as the w/c ratio of the mixture decreased. Moreover, the coarse aggregate content was directly proportional to the mass loss of concrete specimens immersed in sulfuric acid solutions with pH of 0.3 and 0.6, whereas its effect was minor for specimens immersed in the sulfuric acid solution with a pH of 1.0.

Soil-cement blocks are used for the load bearing masonry of 2–3-story buildings. Flexural and shear strength of such walls greatly depend upon the bond strength between the block and the mortar. This paper deals with the methods of improving the shear-bond strength of soil-cement block masonry (without altering the mortar characteristics) and the influence of shear-bond strength on masonry compressive strength. Altering the texture of bed faces of the block, size and area of the frog, and certain surface coatings have been attempted to enhance the shear-bond strength. The results indicate that: (1) rough textured bed face of the blocks yields higher shear-bond strength than the plain surface; (2) use of fresh cement-slurry coating on the bed faces improves the shear-bond strength considerably; (3) no significant changes are noticed in the compressive strength and stress-strain characteristics of soil-cement block masonry due to changes in shear-bond strength; and (4) masonry has a higher straining capacity than that of the block and the mortar.

This study aims at determining the durability of mortar and concrete, including aggregate of discarded car tires under environmental conditions. These conditions are freeze-thaw, seawater, and high temperature. Concrete specimens produced with a cement dosage of 300, a 0.5 water-cement ratio, and 0, 10, 20, and 30% rubber aggregate in volume, where the grain size is $1–4\mathrm{mm}$ instead of fine aggregate, and portland compose cement (CEM II/B 32.5) are used for freeze-thaw. The effect of seawater on specimens produced with 10, 20, 30, and 40% rubber aggregate in volume instead of sand was investigated. For specimens produced with 10, 20, and 30% rubber aggregate in volume, the effect of high temperature was investigated. During this research physical, mechanical, and durability experiments were performed on mortar and concrete specimens. As a result it was determined that in the regions where the environmental conditions are not harsh, use of concrete produced with 10% rubber aggregate is appropriate as it is economical and an effective way of recycling the discarded tires.

Mixtures of rigid sand particles and soft fine-grained rubber particles are tested to investigate their small and large-strain responses. Mixtures are prepared with different volumetric sand fraction sf to identify the transition from a rigid to a soft granular skeleton using wave propagation, $k_0$ loading, and triaxial testing. Deformation moduli at small, middle, and large strains do not change linearly with the volume fraction of rigid particles; instead, deformation moduli increase dramatically when the sand fraction exceeds a threshold value between $\mathrm{sf}=0.6$ –0.8 that marks the formation of a percolating network of stiff particles. The friction angle increases with the volume fraction of rigid particles. Conversely, the axial strain at peak strength increases with the content of soft particles, and no apparent peak strength is observed in specimens with low sand fraction $(\mathrm{sf}⩽0.6)$ . The presence of soft particles alters the formation of force chains. Although soft particles are not part of high-load carrying chains, they play the important role of preventing the buckling of stiff particle chains.

The gradation chart approach is based on the two parameters of Fuller’s model (i.e., maximum size diameter and shape factor) which are obtained by fitting well-graded structures like those of Superpave or Covenin. ASTM mathematical definitions for gravel and sand, and Fuller’s model are used to develop an analytical expression for a gravel-to-sand ratio used here to transform gradation into a numerical that may be correlated to HMA performance parameters. The gradation chart is a Cartesian plot conformed by shape factor and maximum size diameter and thus gradations, specification bands, gravel-to-sand ratios, and response parameters can be represented. Experimental results from recent research works performed by the National Center for Asphalt Technology on the mechanical and hydraulic performance of Superpave mixes are analyzed here. Based on these analyses, the writer resolved the controversy between below the restricted zone and above the restricted zone behavior, and found evidence that gradation specification bands (based on structure and maximum size diameter) would make no sense. Instead, the writer promotes “free design” in which a designer uses available aggregate, supported by a gradation-chart approach, to meet HMA performance parameters required by pavement design.

Many engineering wooden components in our nation’s infrastructure are deteriorating and are in need of repair and strengthening. Timber piles, timber poles, timber posts, and naval fender systems are examples of timber infrastructure elements that are experiencing significant deterioration due to moisture, extreme temperatures, and weathering and are in need of repair and upgrade. The use of fiber-reinforced polymer composites (FRPC) has proven to be effective in rehabilitating and upgrading infrastructure elements. FRPC are also now being considered for new structures to improve strength, ductility, predictability, and durability. This note describes an experimental investigation of circular columns made of poplar wood confined with carbon fibers in an inorganic matrix and subjected to axial compression. Results from this study showed that carbon fiber confinement increased strength, stiffness, ductility, and reduced the variability in timber column behavior under axial loads. The study showed that the full fiber wrap and full fabric wrap confinement were more effective than spirals and hoops and will make the timber column behavior much more reliable and provide protective coating.