Journal of Materials in Civil Engineering

Application of crushed recycled glass in concrete materials can offer significant economical and environmental benefits provided that the alkali-silica reaction (ASR) of glass in concrete is properly controlled. Previous work on the use of glass sand in mortars shows that the reactivity of glass is influenced by its particle size as mortars containing finer glass sand show reduced ASR expansions. This may be counterintuitive since ASR is considered to be a surface reaction and should accelerate by increasing the surface area (i.e., reducing the size) of reactive aggregates. This paper presents a more in-depth investigation of the size-effect phenomena using scanning electron microscopy (SEM)/energy dispersive spectroscopy imaging of mortars containing different size glass particles. The SEM micrographs reveal that ASR does not occur at the glass-paste interface; rather, it occurs inside microcracks that exist inside glass particles which were generated during the glass bottle crushing operations. Larger size glass particles show larger and more active microcracks which render their high alkali-silica reactivity. At its interface with cement paste, glass shows evidence of pozzolanic reaction which leads to the formation of nonexpansive CSH. For particles smaller than #30 sieve (0.6 mm), the intraparticle ASR is minimal and only the interfacial pozzolanic reaction proceeds. This agrees well with the results of ASTM C1260 tests showing that mixed color glass aggregate smaller than #30 sieve does not produce deleterious ASR expansions in mortars even when no ASR suppressant (e.g., fly ash) is used.

Fly ashes were collected from 14 thermal power stations located in different parts of India and were characterized using simple tests like fineness modulus, specific gravity, Rigden voids, German filler test and methylene blue value test, and advanced tests like X-ray diffractometer, scanning electron microscope, and chemical analysis. These fly ashes were divided into four groups based on the above tests and then used as filler in bituminous concrete (BC) mixes. The stone dust, a conventional filler in India, was also used for comparing the results. Rheological properties of filler-bitumen (F/B) mastic prepared at different F/B ratios were determined from softening point test, viscosity test, and dynamic shear rheometer test. Strength and durability tests like Marshall stability, retained stability, tensile strength ratio, and static creep tests were conducted on BC mixes with five types of fillers and the results are analyzed and compared. The study indicated that all the four groups of fly ashes are suitable for use in BC mixes with fly ashes in group 4 having the best performance. The optimum filler content is 7% and properties of fly ash BC mixes are better than those of conventional mix.

Connections are important design elements in timber engineering. Connections loaded perpendicular to grain for structural composite lumber (SCL) materials have received little attention. Connection strength can be determined as the minimum of the Technical Report 12 (TR-12) equations, a generalized form of the National Design Specification (NDS) connection equations, or a shear stress check for reduced beam section. This paper presents test results and compares the 5% offset yield and capacity of double-shear single bolt connections with steel side plates loaded perpendicular to grain to TR-12 equations for solid-sawn lumber and two SCL products. Testing considered three different span/depth ratios and three different loaded edge distances. Splitting failures were observed at the 4D loaded edge distance and mixed mode failures contained splitting at the 7D and 10D loaded edges. The allowable shear stress values dominated the connection at the 4D loaded edge distance and were conservative in some cases. Comparing the TR-12 equations to experimental connection strength, there was little difference for the span/depth ratios and main member materials. Different loaded edge distances demonstrated significant differences between the TR-12 equations and experimental values. The choice of displacement limit for the capacity dowel bearing strength was identified as an important factor in the TR-12 equations.

Splitting failure modes of perpendicular to grain bolted connections have received little attention when compared to splitting modes in parallel to grain connections. Previous research by the authors tested a series of single bolt, double shear perpendicular to grain connections of machine stress rated (MSR) lumber, laminated veneer lumber (LVL), and parallel strand lumber (PSL). Many of the experimental tests resulted in failure by splitting. Two fracture mechanics based models for connections proposed elsewhere were applied. Input parameters for the models were generated by testing matched sections to the connection strength samples. Input properties for the Van der Put model included shear modulus and Mode I fracture energy. Inputs for the Jensen model included shear modulus, modulus of elasticity, Mode I fracture energy, and tension perpendicular to grain strength. Mode I fracture energy of PSL was markedly greater than the energy associated with MSR Lumber and LVL. The Van der Put model overpredicted the experimental connection strength by at least 77%. The Jensen model was found to most accurately predict the connection strength over the entire range of configurations tested. Comparing the Van der Put and Jensen models to the previous work using the national design specification, the Jensen model performed the best in terms of accuracy. The tension perpendicular to grain strength and the method of fracture energy calculation may be important parameters for the capacity of perpendicular to grain loaded wood members.

This paper describes the structural performance of an innovative wood plastic composite (WPC) sheet piling. Tensile coupon tests were performed to determine tensile strength and modulus over a range of strain rates for both WPC and specimens cut from commercially available vinyl sheet piles. Full scale four-point bending tests were conducted up to failure on 20 sets of joined pairs of WPC Z-piles with four different span lengths. For comparison, bending and coupon-level tension tests were also conducted on commercially available vinyl Z-piles and coupons cut from them. The coupon-level tests indicated that WPC had on average a 14% greater modulus than the vinyl specimens in the initial linear range, defined as between 10 and 40% of the respective material’s ultimate tensile strength. However, if the modulus is computed over the same stress range of 10–40% of the WPC ultimate tensile strength, both materials have a similar modulus. The vinyl had a tensile strength 3.6 times that of the WPC. During the bending tests, the hollow cross section WPC Z-piles failed primarily in bending-induced tension, while the solid vinyl Z-piles exhibited buckling of the compression flange. Creep rupture testing was conducted for pair of WPC Z-piles in a four-point bending setup to determine long-term load-carrying capacity. No loss of load-carrying capacity was observed during the 90-day test and creep rates generally decreased during the test. However, creep deflections were larger than what would normally be exhibited by wood structural members. While additional studies are needed to address the effects of water absorption on WPC properties, the findings show promise for wood plastic composite light duty sheet piling retaining wall structures.

This paper investigates the effect of friction angle and flow ratio on stress-strain relationship of high performance concrete (HPC) subjected to dynamic load. The simulation reveals that ultimate compressive strength of HPC shows a discrepancy from 111 to 139 MPa for friction angles between 30° and 50° at a loading rate of 800 GPa/s compared to 87 MPa under static loading. The influence of friction angle on strain is found to be nearly constant, that is, at 0.004. Lower value of flow ratio leads to larger deformation. In turn, the strength is lower. The results show that both friction angle and flow ratio exhibit some degree of sensitivity on either the stress or strain or both. The dynamic strength dependencies on friction angle and flow ratio are correlated. The equation contributes in defining material model parameters in the analysis of HPC dynamic behavior.

High-strength concrete (HSC) has undergone many developments based on the studies of influence of cement type and cement dosages, type and proportions of mineral admixtures, type of superplasticizer, and the mineralogical composition of coarse aggregates. Most studies were carried out using natural sand. In practice, lightweight aggregates from various sources are frequently used in concrete. In the study, concrete mixtures with varying expanded perlite aggregate (EPA) ratios were subjected to dry and wet curing conditions. The variables for the mixtures were 0, 7.5, 15, 22.5, and 30% EPA ratios, in replacement of fine aggregate, in dry and wet curing conditions. The 28-day compressive strengths varied from 40 to 57 and 54 to 81 MPa for dry and wet curing conditions, respectively. The research results show that both EPA ratios and dry curing condition induced the reductions in compressive strength. The reductions due to the dry curing condition were 30, 33, 35, 40, and 26% for 0, 7.5, 15, 22.5, and 30% EPA ratios, respectively. EPA ratios of 0, 7.5, 15, 22.5, and 30% also reduced compressive strengths of 11, 12, 17, and 33% for wet cured samples. The results also show for the mixtures developed in the study that up to a total EPA content of 30% is able to provide HSC for wet curing condition and only 7.5% EPA is also adequate to achieve the HSC threshold, 50 MPa, in dry curing condition. In addition, ultrasound pulse velocity (UPV), thermal conductivity, and oven dry density of samples at both wet and dry curing conditions were determined, and relationship between thermal conductivity and oven dry density, compressive strength, and UPV were exponential for both wet and dry curing conditions.

The objective of the research was to assess the structural capacity of reclaimed asphalt pavement (RAP) as a base layer and to investigate the effect of RAP content, moisture content (MC), freeze-thaw (F-T) conditioning, and dry density (DD) on the resilient modulus of untreated RAP as a base layer. The resilient modulus test was conducted in the laboratory for specimens containing different ratios of RAP and aggregate. All samples containing RAP had higher resilient modulus and lower permanent deformation compared to virgin aggregate. Resilient modulus of RAP decreased as the MC increased. At low MCs there was no clear effect of MC on permanent deformation. However, as moisture increased to the wet side of the optimum MC curve, loss of stability was clear. F-T conditioning did not have a negative impact on the stiffness of RAP; this was explained by the low ability of RAP/aggregate blends to hold moisture. DD effect on the resilient modulus was dependent on the level of MC, but developed models showed that increasing DD would increase $M_R$ at the same degree of saturation.

This paper presents a predictive model for compressive creep behavior of high-density polyethylene (HDPE) commonly used to manufacture polymeric piling and geosynthetics. Accelerated methods to predict the tensile creep of polymers are already available. In this paper, a method to predict the compressive creep of viscoelastic polymers is proposed based on the equivalence of strain energy density (SED) between conventional constant-stress creep tests and strain-controlled stress-strain (ramp loading at different constant strain rates) tests. There is good agreement between the creep behaviors obtained from conventional tests and SED predictions when two stress-strain experiments with strain rates differing by two or more orders of magnitude are used. SED was also used as a basis for predicting the onset of tertiary creep. Finally, onset of tertiary creep was used for rational selection of the ultimate strength of viscoelastic materials, whose strength is inversely proportional to duration of loading.

With low modulus of elasticity, high strength, excellent ductility, excellent durability, and low price, polypropylene fiber is often used in cement-based materials to improve the toughness and anticracking performance of the matrix composite. The aim of this study was to investigate the flexural properties of cement-stabilized macadam reinforced with polypropylene fiber. Four different fiber volume fractions (0.04, 0.06, 0.08, and 0.1%) and four different cement contents (4, 5, 6, and 7%) were used. Besides, a series of tests without mixing fibers was also carried out. By means of four-point loading method, the flexural strength and flexural modulus of elasticity of cement-stabilized macadam were measured. The results indicate that polypropylene fiber can increase the flexural strength and decrease the flexural modulus of elasticity of cement-stabilized macadam. The flexural strength and flexural elastic modulus are increasing with the increase in specimen curing period. When the fiber volume fraction is not beyond 0.1%, the flexural strength is gradually increasing and the flexural modulus of elasticity is gradually decreasing with the increase in fiber volume fraction. Besides, with the increase in cement content, there is a tendency to increase both in the flexural strength and flexural elastic modulus. Furthermore, polypropylene fiber appears to be highly effective in improving the nondeformability of cement-stabilized macadam.

The main objective of this study was to establish the relationship between asphalt binder deformation properties at intermediate and low temperatures, its molecular compositions, and mix performance. To achieve this objective, nine straight binders obtained from two asphalt suppliers were tested using the ductility and the direct tensile tests. To assess the results of these tests, selected asphalt binders were evaluated using high pressure gel permeation chromatography (HP-GPC), differential scanning calorimetry (DSC), and dynamic mechanical analysis. Measurements showed that an inverse correlation exists between binder ductility at intermediate temperatures and failure strain at low temperatures. In other words, a binder that provides high ductility at intermediate temperatures would be characterized by poor elongation properties at low temperatures. This trend was related to the binder molecular compositions as characterized by HP-GPC. An increase in the binder content of low molecular weight results in an increase in its ductility at intermediate temperatures. However, an increase in paraffinic maltene content results in the binder tending to crystallize at higher temperatures as it approaches the glassy region. This was confirmed through DSC measurements, which showed that an increase in crystalline fractions may have a negative impact on the binder stiffness at low temperatures. In general, physical properties of the binder can be strongly linked to its molecular constituents. In addition, there was a positive correlation between the binder ductility and the measured tensile strength of the mixture as well as its strain at failure. Using a binder with a high ductility resulted in a mixture with greater indirect tensile strength and a stronger ability to resist cracking at intermediate temperatures.

This study explores the response of spiral-reinforced lightweight concrete to short-term compression by conducting an experimental program. The response includes deformation capacity, compressive strength, concrete strain at compressive strength, modulus of elasticity, and failure mode. The response is explored by varying the pitch of spiral reinforcement, diameter of spiral wire, compressive strength of plain concrete, and specimen size. Test results show that deformation capacity of spiral-reinforced lightweight concrete decreases with an increase in compressive strength of plain lightweight concrete. Nevertheless, deformation capacity can be increased by reducing the pitch of spiral reinforcement and by increasing the diameter of spiral wire. This study also suggests the mathematical expressions to estimate the compressive strength of spiral-reinforced lightweight concrete, concrete strain at compressive strength, and modulus of elasticity of plain lightweight concrete. Understanding of the concrete response gained from the present study would be beneficial in analysis and design of lightweight concrete structural members.

This paper examines a cast-in-place composite polymer liner used in retrofitting cracked cast iron pressure water pipes. The installation of the liner can result in the formation of geometric imperfections (wrinkles) of different patterns and sizes if the external circumference of the liner exceeds the internal circumference of the host pipe. A series of split-disk tests were conducted on 25-mm wide ring samples of the polymer liner to examine the effects of the presence of three different wrinkle configurations, the loading rate, and cyclic loading on the circumferential strength of the liner. In all the test samples, cracking of the resin occurred at the wrinkle, but ultimate capacity was always greater than the cracking load. A reduction in the ultimate hoop strength of up to 23% occurred, depending on the wrinkle pattern. Cyclic loading corresponding to 50-year service life was applied, leading the resin in some samples to crack at the wrinkle. At a very slow loading rate of 0.1 mm/min, the ultimate strength of the liner was reduced by 16%.

In order to understand the engineering properties of soil reinforced by short polypropylene fiber, a series of tests were carried out to study the effect of fiber content and fiber length on the strength of the fiber-reinforced soil, as well as the effect of aggregate size and fiber additives on the engineering properties of the fiber-reinforced soil. It was shown from test results that the unconfined compressive strength (UCS), cohesion, and internal friction angle of fiber-reinforced soil were greater than those of the parent soil; the UCS, cohesion, and internal friction angle of fiber-reinforced soil exhibited an initial increase followed by a rapid decrease with increasing fiber content and fiber length, and hence the optimal fiber content and fiber length were found as 0.3% by weight of the parent soil and 15 mm, respectively, in this investigation. Similar trends were found in the parent soil and the fiber-reinforced soil that the strength declined with an increase in aggregate size and there was a critical size for aggregate breakage between 3.5 and 7.5 mm in average diameter; the presence of polypropylene fiber could effectively contribute to the increases in the strength and stability of the parent soil.

In this research, the feasibility of using embedded cement-based piezoelectric sensors to detect the acoustic emission (AE) activities in concrete has been studied. A sensor is presented that is made with the 0–3 cement-based piezoelectric composite as sensing element. The composite is formed by pressing mixed cement-piezoelectric powder into a penny-shaped thin plate. In the terminology of 0–3, 0 represents the dimension of the piezoelectric particle and 3 stands for the dimensions of the matrix. By adjusting the dosage of the piezoelectric ceramic powder, the properties of the composite can be tailored to suit designated applications. Sensors made of the composite (0–3 sensor) are able to be embedded into concrete and have broadband frequency response. It is shown by a four-point bending test on a concrete beam that the sensors have excellent ability in AE activity detection. High sensitivity is also observed for the embedded sensors.