Journal of Materials in Civil Engineering

Natural processes, such as weathering, faults, land subsidence, earthquakes, and human activities, create fractures and fissures in concrete structures that can reduce the service life of the structures. A novel strategy to restore or remediate such structures is biomineralization of calcium carbonate using microbes, such as those in the genus of the Bacillus species. The present study investigated the effects of Bacillus sp. CT-5, isolated from cement, on compressive strength and water-absorption tests. The results showed a 36% increase in compressive strength of cement mortar with the addition of bacterial cells. Treated cubes absorbed six times less water than control cubes as a result of microbial calcite deposition. The current work demonstrated that production of “microbial concrete” by Bacillus sp. on constructed facilities could enhance the durability of building materials.

Air pollution control (APC) residues generated from cleaning gaseous emissions at energy-from-waste (EfW) plants burning municipal solid waste are classified as hazardous waste and are a significant disposal issue in the UK. APC residues have been combined with glass-forming additives and treated using direct current (DC) plasma technology. This reduces the waste volume and produces an inert black glass (APC glass) that has potential to be used beneficially. In this work, APC glass has been characterized and used to form geopolymers. Metakaolin and ground granulated blast furnace slag (GGBFS) geopolymers have also been prepared. The compressive strengths, density, water absorption, and porosity of APC glass geopolymers were evaluated. Samples were also characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscropy (FTIR). Results show that APC glass geopolymers have excellent mechanical properties compared with other geopolymer materials with high density, low porosity, and particularly high compressive strength. The work has demonstrated that the glass from DC plasma treatment of APC residues can be used to form geopolymers with appropriate properties to be used in a range of construction applications.

The storage of ${\mathrm{CO}}_2$ is an expected solution by the oil industry: using petroleum wells as geological reservoirs is a very important and new research field. The durability of such storage has an importance to be predicted. The carbonation of oil-well cement (Class G type) under temperature (90°C) is evaluated in this paper. In the first part of the paper, the fabrication protocol for samples is explained, and the test conditions are described. The evolution of cement carbonation over time is then presented. In the second part of the paper, the results obtained by triaxial mechanical tests with permeability measurements at 90°C are discussed. Mechanical evolutions obtained for different confinement pressures show a remarkable decrease in permeability and an important increase of multiaxial strengths, which may exceed 100%. Long-term tests of carbonation will be necessary to evaluate the effect of carbonic acid on the chemical stability of carbonated cement.

In this paper the results of an experiment on the granulation of nonmetallic automotive shredder residues to produce aggregates for cementitious or asphalt mixes are presented and discussed. In a preliminary separation step, a fraction containing mainly inert and nonmetallic materials was sieved to obtain the required grading and analyzed for the metal content. In the following granulation step, performed in a pilot-scale granulator, the sieved fraction was mixed with binding materials and a superplasticizer agent, to produce granules of up to $2,000\mathrm{kg}/{\mathrm{m}}^3$ specific weight. The size of the produced granules, between 2 and 40 mm, proved to be a function of water content; increasing the water/solids ratio, the diameter of the particles also increased. The granules were then used as artificial lightweight aggregate for concrete mixes. Concrete samples showed a specific weight up to approximately $2,000\mathrm{kg}/{\mathrm{m}}^3$ and a compressive strength up to approximately 30 MPa, depending on the fluff content of the mixes and on the nature of the binder and the other components used. Leaching tests performed on the concrete samples showed that a good immobilization of metals and ions was achieved.

Electrokinetic nanoparticle (EN) treatments were employed to mitigate corrosion in reinforced concrete. In this approach an electric field was used to drive pozzolanic nanoparticles through the capillary pores of concrete and directly to the reinforcement. The intent was to use the nanoparticles as pore-blocking agents to prevent the ingress of chlorides. Treatment effectiveness was examined for both freshly batched and relatively mature concrete. Cylindrical reinforced concrete specimens were subjected to EN treatment immediately after batching and then exposed to chlorides for a period of two years. The EN-treated specimens exhibited a reduction in corrosion rates by a factor of 74 as compared to the untreated controls. Another set of specimens was subjected to chlorides for a period of two years prior to EN treatment application. Electrochemical chloride extraction and EN treatments were performed on these mature specimens for one week. These specimens were placed back into saltwater exposure for an additional year. The mature controls exhibited severe corrosion cracking as compared with the mature treated specimens after 1 year of saltwater exposure. The corrosion rates were 8 times that of the treated specimens. Microstructural and chemical analysis was conducted using scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. This study demonstrated that microstructural changes attributable to treatment were effective in mitigating reinforcement corrosion in both young and mature concrete.

In this study, traditional reaction equations (based on the theory of Powers) are applied to the hydration reactions of portland cement and the pozzolanic reaction of fly ash separately. Moreover, portland clinker is considered as a mixture of four minerals, each with its own sensitivity to the presence of fly ash. The kinetics of the reactions of each clinker mineral have been analyzed by fitting generally known models such as the Avrami and Jander equations to isothermal heat measurements on pastes of cement, fly ash, and water. The proposed model therefore consists of different stages, in which nucleation, phase-boundary, and diffusion reactions become rate controlling. The kinetics of the pozzolanic reactions have been described with similar equations, implementing parameter values based on measured selective dissolution data. Fly ash may accelerate the reaction of a clinker mineral, while at the same time it can decelerate another mineral. Depending on the relative proportions of the clinker minerals, the method can explain the apparent contradiction found in literature related to the acceleration or deceleration effect of fly ash on the cement hydration.

This paper discusses the applicability of new controlled low-strength materials (CLSM) that include incinerated sewage sludge ash. The incinerated sewage sludge ash was used as a replacement for fly ash, which is the main component of CLSM. A dust powder made during crushed-stone production was used as a fine aggregate. This new type of green CLSM is a promising sustainable cementitious material with the capability to reduce ${\mathrm{CO}}_2$ emissions. The test results show that adequate strength development and reasonable flowability can be achieved if the mixture proportion is carefully designed. The leachate characteristics of the new CLSM are evaluated in this paper, and the test results show acceptable leachate levels. The test results also confirm that a wide range of municipal solid wastes could be used as materials in the new green CLSM. Finally, backfill construction was conducted with this new CLSM, and the excellent performance was confirmed.

Paper mill sludge is often incinerated for heat recovery and volume reduction. In Italy, about 600,000 t of paper mill sludge is produced yearly. About 6 kg of sludge is produced per ton of paper produced. The paper mill sludge is recovered from a primary mechanical separation process. When it is combusted as a single fuel source, it produces paper mill sludge ash (PA). In this project, PA was studied to evaluate its use as a supplementary cementitious material in mortars and concrete manufacturing. On the basis of the data collected, it was concluded that PA, if used to replace up to 10% of the portland cement, shows a positive effect on the mechanical performance of mortars. On the other hand, because of its high fineness and consequently high water absorption, it required a higher amount of water. It was concluded that the use of PA should not be higher than 10% by weight of the cement replaced, unless mortar mixtures are judiciously proportioned.

The present study aims to investigate the effects of porous ceramic waste aggregate (PCA) coarse aggregate as an internal curing material on the compressive strength, porosity, and shrinkage of portland blast furnace cement type B concretes (BB) with a water-to-cement ratio (W/C) of 0.55, in which the replacement ratios of conventional coarse aggregate by PCA were 10 and 20% in volume and the specimens were exposed to drying at the ages of 3 and 7 days and cured under sealed condition. The results showed that internal curing using PCA to replace coarse aggregate by 10 and 20% in volume was effective in improving the compressive strength of BB compared with ordinary portland cement concrete and BB at the age of 28 days, independent of the exposure conditions. Moreover, 10% replacement by PCA was more effective than 20% replacement. Internal curing for BB was found to be effective in decreasing pore volume for specimens exposed to drying at the age of 3 days. However, the total pore volume of BB cured internally was almost unaffected by the starting age of drying as well as the replacement ratio of coarse aggregate by PCA. In specimens exposed to drying at 3 and 7 days and measured at 28 days, the compressive strength was increased by internal curing, corresponding to the decrease in pore volume for sizes larger than 0.02μm. However, in specimens subjected to sealed curing, both the compressive strength and pore volume for sizes larger than 0.02μm, which were measured at 28 days, were found to be increased by the internal curing. The internal curing was not effective in reducing autogenous shrinkage owing to the comparatively high W/C of 0.55 of the present concrete.

In India, the generation of electricity is overwhelmingly dependent on the combustion of high-ash coal. The present availability of fly ash has already exceeded 130 million tons, and its generation is likely to reach 170 million tons by 2011–2012. Although the present gainful use of fly ash is close to 50% of the quantity generated, a countrywide directive has been established to effectively use the entire quantity generated in 2011–2012. This objective can be met only if one looks for newer avenues of bulk use that have not been tried successfully. To achieve this target, several technological endeavours are in progress in India to enhance the quality and reactivity of fly ashes through mechanochemical activation. The regular and experimental technologies of comminution and size classification have not resulted in producing submicrocrystalline or nanocrystalline particles from the crystalline fly ashes; and hence, no quantum jumps in their reactivity have been realized. Therefore, the need for converting the fly ash grains to submicrocrystalline particles is critical if the performance of fly ashes has to approach that of silica fume or silica gel.

Precast, prestressed concrete is used to construct a variety of structures. The primary Milwaukee area precast supplier chooses to make its product without using any fly ash. The argument is that using fly ash would reduce the early release strength of the concrete mix. This paper shows research to dispute that claim and then illustrates the monetary and environmental savings that could be achieved if fly ash is used as a cement substitute.

The knowledge of high temperature thermal properties is critical for evaluating the fire response of concrete structures. This paper presents the effect of temperature on the thermal properties of different types of high-strength concrete (HSC). Specific heat, thermal conductivity, and thermal expansion are measured for three concrete types, namely, HSC, self-consolidating concrete (SCC), and fly ash concrete (FAC), in the temperature range from 20–800°C. The effect of steel, polypropylene, and hybrid fibers on thermal properties of HSC and SCC is also investigated. Results from experiments show that SCC possesses higher thermal conductivity, specific heat, and thermal expansion than HSC and FAC in the 20–800°C temperature range. Data generated from tests is utilized to develop simplified relationships for expressing different thermal properties as a function of temperature. The proposed thermal property relationships can be used as input data for evaluating the response of concrete structures under fire conditions.

Moisture damage in hot-mix asphalt (HMA) occurs because of a loss of adhesion and/or cohesion, resulting in the reduced strength or stiffness of the HMA and the development of various forms of pavement distress. There are several different approaches for improving adhesion and reducing moisture sensitivity in asphalt mixtures. One convenient approach is coating the aggregate surface with a suitable agent to reverse the predominant electrical charges at the surface and reduce the surface energy of the aggregate. In this research, the effects of two types of polyethylene (PE), namely high-density polyethylene (HDPE) and low-density polyethylene (LDPE), were added to coat the aggregate, and the moisture damage to the asphalt mixtures was evaluated. Three types of aggregates representing a considerable range in mineralogy (limestone, granite, and quartzite) were evaluated during the course of this study. This paper explains the theoretical and experimental concept of predicting moisture damage in asphalt concrete mixes using the surface free energy (SFE) concept and laboratory testing analysis, respectively. It also shows the effects of polymeric aggregate treatment on moisture damage within the mixes. SFE measurements were used to compute the work of adhesion between the aggregates, asphalt, and the cohesive bond strength in the asphalt binder and aggregate. The SFE characteristics of three types of aggregate with and without PE treatment and asphalt were evaluated for moisture-damage susceptibility using a universal sorption device (USD) and dynamic Wilhelmy plate method, respectively. To validate these results, a dynamic modulus test was used to apply a repeated unconfined, compressive load to the sample in a controlled stress mode. The results of the SFE method indicate that PE increases the wettability of asphalt binder on the aggregate and the adhesion between the asphalt binder and aggregate. The same results were achieved using the values obtained by laboratory testing analysis. The aggregates treated with HDPE showed better resistance against moisture damage in both methods of study.

This study investigated the effect of exposure to elevated temperature on the yield strength of single-shear nail connections when subjected to lateral loading. Solid sawn lumber and laminated veneer lumber were used as framing members and two different thicknesses of both oriented strand board and plywood were used as the sheathing members. The connection geometries evaluated were typical of those encountered in lateral force resisting systems such as shear walls or roof diaphragms. The connection geometries were (1) edge connection—nail positioned 19 mm from the panel edge, loaded parallel to the grain of the main member, and (2) plate connection—nail positioned 19 mm from the panel end, loaded perpendicular to grain of the main member. Data collected from monotonic tests on 480 nail connections, after exposure to elevated temperatures, were analyzed for yield strength. In addition, 210 dowel bearing strengths were evaluated for the same treatments. The results indicated that exposure to elevated temperature caused significant degradation in lateral yield strength after exposure. The highest degradation occurred when exposed to 200°C for 2 h. For example, for plywood (11.2 mm) and solid lumber connections, the decrease in yield strength after exposure to 200°C for 2 h was 26% for edge connections and 56% for plate connections. The results further indicated that, given thermal degradation of the dowel bearing capacity of a material, the existing yield models stipulated in National Design Specifications (NDS) can predict yield load values for nailed connections for a given sheathing and framing member combination under those thermal degradation conditions. Additionally, the yield models predicted a predominant yield mode (${\mathrm{III}}_s$), consisting of a single plastic hinge being formed just beneath the surface of the thicker member. These predictions were consistent with observed yield modes.

A new idea is investigated in this study to reduce the cover spalling of high-strength concrete columns: installing relatively cheap materials such as household fly screen and wire mesh in the formwork of RC columns. Three materials were chosen in this study: fiberglass fly mesh (FGFM), standard aluminum fly mesh (SAFM), and $12.7\times 12.7$ galvanized steel wire mesh (S12.7 WM). A total of 16 cylindrical specimens with a length of 925 mm and a diameter of 205 mm were cast and tested under concentric, eccentric, and pure bending loading. The testing results showed that S12.7 WM significantly improved the load-carrying capacity under both concentric and eccentric loading but did not significantly increase the ductility of the columns for each load case. FGFM and SAFM significantly improved the ductility of columns under concentric loading, but the significance decreased with the increase in eccentricity.

The present paper deals with the procedure for modification of $80/100$-paving grade asphalt cement using reclaimed polyethylene (PE) derived from low-density polyethylene carry bags collected from domestic waste. The details of the preparation of the PE-modified binder and the results on variation of binder properties with blending temperature and blending time are presented. Results of various tests carried out on the different PE blends indicated enhanced binder properties like improved storage stability, resistance to aging, degradation, and temperature susceptibility. It is observed that viscosity at a given temperature increases with the addition of PE in the binder. Dynamic shear rheometer test results revealed that PE-modified binders (when subjected to the same stress) experienced lower strains than the neat asphalt; in addition, $\tan \delta$ values of PE-modified binders considerably decreased as the PE content was increased. It was found that 5% PE content in modified asphalt by weight is adequate in terms of enhanced binder properties studied.

An experimental campaign supports a model named TransChlor for bringing liquid water moved by capillary suction and chloride ions into concrete. The principal objective of the experimental campaign is to represent conventional concretes under real conditions of a local microclimate. Capillarity tests were performed on specimens of three different types of concrete dried at different levels of relative humidity at low temperatures (to $-20°\mathrm{C}$) to represent the effect of a real climate in winter. This article shows that low temperatures decrease water absorption by capillarity. The use of TransChlor to simulate liquid water and chloride ion penetration into concrete is presented with an emphasis on the faster transport mode of chloride ions by convection when water is in contact with concrete.

This article assesses the use of sewage sludge as a raw material in the ceramic industry, specifically in the manufacture of soft-mud bricks, to determine the maximum incorporation of sludge that results in technically sound and environmentally friendly bricks. The results obtained confirm that there was no alteration in the odor of the bricks, even at high proportions of sludge; however, high concentrations of sludge had a negative influence on certain properties, such as mechanical strength and absorption. Compressive strength was significantly diminished with the addition of sludge: the bricks with 5% sludge lost an average of 45% of the strength obtained by the control brick; the bricks manufactured with 15 and 20% lost around 70% of maximum strength; however, they still met minimum strength standards. For the specified conditions of this study, it was concluded that 20% was the maximum proportion of sludge that could be incorporated into a ceramic mass and still meet technical and environmental requirements.

The bond behavior at the polymer cement mortar (PCM)-concrete interface particularly affects the structural behavior of overlay-strengthened slabs or beams, and the debonding of the PCM overlay was one of the major failure modes. The design procedure of PCM overlay to strengthen an RC element should avoid these premature debonding failures. Because no reliable design method for retrofitting with the PCM overlay is currently available for the practitioner, a need exists to understand the mechanism of the PCM overlay debonding process to prevent failure. This paper presents an analytical approach for a PCM overlay-strengthened beam failed by intermediate crack (IC) debonding. The limit of transferred shear force along the PCM-concrete interface to avoid any occurrence of debonding is analytically provided. The reliability and accuracy of the proposed analytical procedure have been successfully verified by knowing the ratio of analytical and experimental strength of the PCM-strengthened beams compiled in a bending test database, which has a mean value of 1.10 and a standard deviation of 0.14.

The building industry accounts for up to 40% of the earth’s energy usage from material extraction through building operation; housing constitutes roughly 30% of energy use in North America. Owners and consumers are looking for more efficient building systems that would decrease this use of energy. The material chosen to construct the structure of a building has the potential to reduce the building’s initial environmental impact and its life cycle energy use. However, this is rarely considered during conceptual design. Sustainable construction materials that have low embodied energy include earthen construction and straw bale construction. However, these materials are not widely accepted alternatives in North America because they are included only in select building codes in North America and around the world. In this paper, an extensive review of the current construction practice of sustainable construction materials is summarized. Durability concerns and limitations of the methods of construction are discussed, and areas of future research are identified.

Desiccation cracking in drying soil is a common natural phenomenon, and it significantly impacts the soil’s mechanical and hydraulic behavior. In this study, experimental desiccation tests were conducted on an initially saturated soil layer. Several aspects of the behavior of the soil—water evaporation, volume shrinkage, crack initiation, and propagation—were investigated. By applying image processing techniques, the geometric or morphological characteristics of the crack patterns were quantitatively described. The results show that cracking occurred during the constant evaporation rate stage, when the soil was still fully saturated at a water content of 41%. A growing crack obeys certain objective laws, and it finally splits the soil surface into relatively regular patterns: The first crack generally occurs on surface defects at the bottom of “potholes” and at the fringe of aggregates. Cracks intersect with one another at right angles, and the final crack pattern is dominated by square shapes. Most cracks develop before the air entry point ($w=14.5\%$), and surface desiccation cracking tends to terminate after the shrinkage limit ($w=9.5\%$) is reached. In addition, this paper discusses the suction and tensile strength development involved in desiccation cracking initiation, and some explanations for various phenomena are also presented.

This paper reports a laboratory study investigating the use of granulated copper slag as a fine aggregate in hot-mix asphalt concrete. Marshall-mix design was performed on different blends of aggregate containing up to 40% copper slag. The dynamic modulus $|E^{*}|$ test, as a primary material property input in the Mechanistic-Empirical Pavement Design Guide (ME-PDG), was conducted at different frequencies (0.1 to 16 Hz) and temperatures (25 to 60°C). $|E^{*}|$ master curves and shift factors were developed for the control and slag mixes. The developed curves were compared with the Witczak predictive $|E^{*}|$ model for Levels 2 and 3 of the ME-PDG. The results indicated strength reduction as slag content increases in the mixes compared to the control mix. The developed master curves and shift factors were compared with the Witczak predictive model. The results of stripping potential evaluated by the indirect tensile strength indicated a reduction in strength, but the tensile-strength ratio was superior to that of the control mix. The results indicated a good potential for using copper slag as an aggregate in asphalt mixes and provided the essential material characterization for using the material in the ME-PDG method.

The water content and lightweight aggregate proportions in lightweight alkali-activated (AA) concrete need to be carefully managed to control the quick slump loss of fresh concrete and to meet the mechanical properties that are required for structural concrete. This study tested 10 lightweight AA slag concrete specimens to evaluate the effect of the water content on the workability and various mechanical properties of the concrete. The source material, ground granulated blast furnace slag, was activated by using sodium silicate and calcium hydroxide powders to produce a cementless binder. The rate of development of the compressive strength and the shrinkage strain measured from the concrete specimens were compared with empirical models proposed by American Concrete Institute (ACI) 209 for normal-weight portland cement concrete. To examine the practical applicability of the lightweight AA slag concrete, the splitting tensile strength and the moduli of elasticity and rupture recorded from the concrete specimens were compared with empirical equations and a database for lightweight ordinary portland cement (OPC) concrete, whenever possible. The test results showed that an increase of water content alleviated the quick slump loss of the fresh concrete and slightly increased the compressive strength of the hardened lightweight AA slag concrete. Additionally, the rate of development of the compressive strength of lightweight AA slag concrete cured under room temperature was comparable with that of steam-cured early strength portland cement concrete. The splitting tensile strength and the moduli of rupture and elasticity of lightweight AA slag concrete were comparatively better than those of lightweight OPC concrete. As a result, they can be conservatively evaluated by using the empirical models that are recommended for lightweight OPC concrete. Moreover, the extent of shrinkage strain of lightweight AA slag concrete was larger than that predicted from the empirical model specified in ACI 209 at an early age and after 40 days, regardless of the water content.

Several specimen geometries have been used to assess restrained shrinkage-cracking behavior of concrete materials. This paper used a series of restrained slab tests to illustrate the importance of specimen geometry on the restrained shrinkage cracking behavior. While restraint was provided along the base of the slab, a portion of the slab was left unbonded to the base in the center of the specimen. The length of this unbonded portion was varied to demonstrate its impact on the age of cracking and crack width that occurred. The age of cracking was measured using visual analysis, image analysis, conductive surface coating, and acoustic emission. Whereas image analysis and conductive paint detect cracks only after they appear on the surface, acoustic emission also provides information on damage development before the cracks were visible. Cracking occurred in a less stable fashion in slabs with a larger unbonded region. The larger unbonded length in a slab caused wider cracks to appear at an earlier age than in a slab with a smaller unbonded region.

The Adhesive-Applied Roofing System (AARS) is a new generation of built-up roofs gaining popularity in North American low-slope application. AARS uses no fasteners, and all components (e.g., steel deck, vapor barrier, insulation board, cover board, and membrane) are integrated by application of adhesives. Although AARS has been in use, existing standards address only mechanically attached or bonded roof assemblies. To quantify the wind-uplift performance of the AARS, an industry–university–government collaborative research project, Development of Wind Uplift Standard for Adhesive-Applied Low-Slope Roofing System, has been initiated. The project has three major tasks: experimental investigation, formulation of a numerical model, and development of wind design guide and standards. Task 1 developed test protocols to quantify the uplift and peel resistance of small-scale AARS specimens respectively subjected to tensile and shear loading. Using the standardized tensile test parameters, this paper identifies the effect of material combinations and variation in the adhesive applications on the uplift resistance of AARS subjected to tensile loading. This parametric study not only verified the applicability of the developed tensile test method for variations in the configurations, but it also identified the weakest link in AARS. Data from this small-scale testing can facilitate industries to optimize the material combinations such that it can be correlated with the systems wind uplift resistance.

The construction of some maritime structures (e.g., reinforced concrete caissons) is cheaper and easier when made on floating docks. In this case, concrete is submerged just hours after casting, is cured in contact with seawater and remains submerged for its whole service life. Most international standards do not allow this type of curing for reinforced concrete, although there are not many experimental results on its final effects on concrete properties. A research program has been developed to determine the effect of seawater curing on reinforced concrete properties. Different tests (density, compressive strength, porosity, absorption, capillarity and chloride penetration rate) have been carried out on different quality concretes, cured with tap water or seawater. The results show that differences are found in concrete properties in the short term in seawater-cured concretes, but these differences dissipate at later stages for standard quality submerged concretes [water-cement ratio $(\mathrm{w}/\mathrm{c})=0.45$]. Small differences remain for high-quality concretes ($\mathrm{w}/\mathrm{c}=0.40$ and silica fume admixture), where chlorides penetrate deep inside, attributable to seawater curing (7 mm for ordinary portland cement and 6 mm for silica fume concretes, approximately).