Journal of Materials in Civil Engineering

This paper examines the short-term resistance ability of two different cementitious systems prepared using silty clay as a major component against 5 wt% sodium sulfate and 5 wt% magnesium sulfate solutions. The two cementitious systems are clay–portland cement and clay-high calcium fly ash (FA) geopolymer. The 28-day strength of the clay-FA geopolymer is up to 1.2 times higher than that of clay-cement. The results show that the physical performance of clay-FA geopolymer when exposed to sulfate solution is better than that of clay-cement. While the geopolymer phase is prominent in the clay-FA geopolymer system, gypsum, and ettringite phases are present in both systems especially in the clay-cement system. The strength reduction in clay-cement with duration of sulfate exposure is caused by the formation of ettringite and crystallization of gypsum (observed by scanning electron microscope and X-ray diffraction) as well as the decalcification of CSH phases. There is no major change in the microstructure and pH of clay-FA geopolymer when exposed to sulfate solutions, and hence the strength reduction is insignificant. The exposure to magnesium sulfate solution causes more degradation in both clay-FA geopolymer and clay-cement system than the exposure to sodium sulfate because the CSH phases react with magnesium sulfate solution to form ettringite. The disappearance of CSH phases in both systems is observed by XRD analysis. Overall, clay-FA geopolymer show better resistance to sulfate attack than clay-cement. The clay-FA geopolymer can be considered as a green construction and building material in sulfate-rich areas.

Compared with ordinary concrete, the segregation resistance of self-consolidating concrete (SCC) are more sensitive to small variations of mix proportions such as dosage of superplasticizer, and the size, volume, and gradation, as well as moisture content of the fine and coarse aggregates. To design a SCC mixture, which is robust against small variations in raw materials, it is critical to understand the mechanism of how mix proportions affect robustness. In this paper, modified segregation probe was used to study the effects of various mixture properties on static stability robustness of SCC. It was found that a static segregation rate equation is helpful to explain how paste rheology and aggregate properties affect robustness. Mixture properties, such as higher paste volume, lower superplasticizer % by weight of cement, lower slump flow, smaller aggregate size, better gradation, and higher aggregate packing density may improve robustness. Among the aggregate properties, smaller aggregate size and better gradation seem to have more significant effects than higher aggregate packing density. As expected, no obvious relationship was observed between concrete rheology and robustness in this study.

The scaling resistance of concrete with strength grades of 30 MPa (C30) and 50 MPa (C50) subjected to different types (A and B) and concentrations (3, 5, and 20%) of deicing salt solution were studied using an accelerated freezing-thawing test. Deicing Salt A was composed of about 80% sodium chloride and 20% calcium chloride, B was composed of 70% sodium chloride, 25% magnesium chloride and 5% calcium chloride. The changes in strength, mass loss and relative dynamic modulus of elasticity of concrete were examined during the testing. The results showed that the salt scaling resistance of C50 was better than that of C30. The former could pass 160 freezing-thawing cycles while the latter could pass only 95 cycles. Specimens showed the largest deterioration when subjected to 5% solution, and the smallest deterioration when subjected to 20% solution after 200 cycles. Deicing salts with a higher percentage of NaCl and ${\mathrm{CaCl}}_2$ demonstrated a more obvious deterioration effect on concrete. The incorporation of 5% silica fume (by the mass of binder) or 1% high-efficiency air entraining agent significantly improved the salt scaling resistance of the concrete, even no visible deterioration was observed after 200 cycles. The main scaling deterioration features of concrete include surface spalling and cracking. Microstructural examinations indicated that formation of Friedel’s salt resulting from chemical reaction between NaCl or ${\mathrm{CaCl}}_2$ and calcium aluminate hydrates could lead to the deterioration of concrete during salt scaling testing.

The use of tiles in Portuguese façade coatings began in the nineteenth century with industrialized production of tiles. Nowadays, many nineteenth century façades are degraded and in urgent need of maintenance. New bonding mortars must be developed in order to substitute the existing ones. Compatibility, durability, and reversibility with the old materials must be respected. The tile/mortar adhesion strength is a very important characteristic in old tiles reattachment. It mostly depends on characteristics of mortars, porosity, and moisture content of tiles. Mortar in contact with a wet tile will have different binding characteristics than that in contact with a dry tile. This work studies the adhesion of lime-based mortars to old tiles and the influence of moisture and open porosity in the tile/mortar interface. New tiles with similar porous characteristics as nineteenth century tiles were used. A newly designed test was used to test the tile/mortar adhesion strength. The composition of mortars and moisture content of tiles was varied. Some trends of variation of mortar compositions and moisture conditions of tiles were observed in tile/mortar adhesion strength. The increase of moisture in tiles causes the increase of mortars’ open porosity. Mortars applied in wet tiles have higher values of adhesive strength than mortars applied in dry tiles. The tile/mortar adhesive strength increases with increasing open porosity of the mortar in the interface.

Since its introduction, warm mix asphalt (WMA) has garnered a lot of attention and interest from the pavement industry as a promising technology to replace the conventional hot mix asphalt (HMA). Despite its many benefits, including reducing emissions and fuel usage, definitive answers on the feasibility of replacing HMA pavements with WMA are yet to be answered. A major concern for WMA is susceptibility to moisture-induced damage. In this research study, mixtures prepared using three WMA technologies- viz. Sasobit, Advera WMA and the Foamer were evaluated for their moisture susceptibility and permanent deformation in comparison with an HMA mixture. Tensile strength ratio (TSR) and asphalt pavement analyzer (APA) tests were conducted on these mixtures. Results show that moisture-based WMA technologies (Advera and Foamer) are more susceptible to moisture damage. However, rut depths evaluated using APA, even for moisture-conditioned specimens, indicated WMA performance on par with that of HMA. Even though the TSR values do not meet specifications, APA test results indicate good potential for the widespread use of WMA.

Because of the increasing difficulty in obtaining natural aggregate, alternative aggregates have been considered in the construction industry. One of the feasible alternatives is to reuse construction and demolition waste as aggregates, called recycled aggregate, to make new concrete called recycled aggregate concrete (RAC). However, the compressive strength of RAC is usually poor due primarily to the high water absorption capacity, high porosity, and weaker bond of interfacial transition zone between recycled aggregate and new cement mortar. This paper presents the results of a comprehensive experimental study on RACs made of 100% recycled coarse aggregate. Three different mixing approaches, several surface pretreatment methods with two different pretreatment materials were used to improve the compressive strength of RAC. The experimental results showed that proper surface pretreatments and mixing approaches can improve the quality of RAC significantly. The water-cement ratio of pretreatment materials is very important. The compressive strength of an optimized RAC with 100% recycled coarse aggregate can reach as high as 43.3 MPa (6,277 psi) on 28 days.

The coefficient of thermal expansion (CTE) of portland cement concrete (PCC) is a significant factor affecting the performance of concrete pavements. It is also required as a direct input in the mechanistic-empirical pavement design guide (MEPDG). The primary objective of this study was to determine CTE values of PCC mixes used in Hawaiian pavements. A secondary objective was to study the effect of curing time on the CTE. To achieve these objectives, 45 concrete specimens were prepared on-site at three Hawaiian concrete companies using local basaltic aggregates. For each site, 15 replicate test specimens (five sets of three) were cured in a 100% humidity room for 3, 7, 14, 28, and 56 days before determining their CTEs following AASHTO T 336. It was found that CTE values vary significantly with curing time. It was also observed that the CTEs at 28 days computed in this study, ranging from $6.1\times {10}^{-6}/°\mathrm{F}$ to $6.6\times {10}^{-6}/°\mathrm{F}$ ($11.0\times {10}^{-6}/°\mathrm{C}$ to $11.9\times {10}^{-6}/°\mathrm{C}$), differ significantly from the value recommended in the MEPDG manual of practice for concrete specimens with basaltic rock as a constituent ($5.2\times {10}^{-6}/°\mathrm{F}$, $9.4\times {10}^{-6}/°\mathrm{C}$), which can lead to designs with overestimated performance. The variation caused by curing time is similar in magnitude to the variation caused by the use of different mixes for a given curing time. Thus, the study results support the need to establish a standard curing time when determining an appropriate CTE for design. Furthermore, use of a nonrepresentative default value can have a higher effect than that produced by differences between mixes or curing times, which highlights the importance of performing research to establish local CTE values. Based on the results, it is recommended to use the CTE obtained after 28 days of curing for design. Possible implications of the results obtained in this study are illustrated with a particular jointed plain concrete pavement (JPCP) design with the MEPDG.

The use of fly ash in concrete has received significant attention during recent years, owing to environmental concerns regarding its disposal and to its potential use as a supplementary cementitious material owing to its ability to improve concrete performance. Although a fly ash content of less than 25% of the total cementitious content is routinely used in concrete, high-volume fly ash (HVFA) concrete is not commonly used because of perceived lower early age strengths. The objective of this research was to use maturity based modeling to demonstrate that the beneficial effects of high temperatures observed in structural elements such as slabs and concrete beams during the hydration process associated with the mass features of such elements may compensate for the slower rate of strength gain of fly ash concrete that is typically observed in standard laboratory cured cylinders. Match cured cylinders were used during this process to estimate the early age in-place strength of HVFA concrete and to confirm the predicted mature strengths. The results have shown that standard and field cured cylinder strengths underestimate the in-place concrete strength. High in-place temperatures owing to the mass characteristics of structural elements result in increased and satisfactory in-place early age strengths for construction, measured by match cured cylinders and pullout testing, and predicted by maturity modeling.

Motivated by the need to improve oil well integrity for potential carbon capture and storage through ${\mathrm{CO}}_2$ sequestration, nanosilica was hypothesized capable of improving the quality of oil well cement (OWC) in medium and deep oil wells. In this study, OWC was mixed with 1 and 3% nanosilica by weight to produce OWC pastes with water to binder ratio ($w/b$) of 0.45. The specimens were cured under high temperature and pressure, simulating what occurs in oil wells. A method of analysis combining ${}^{29}\mathrm{Si}$ nuclear magnetic resonance (NMR) and nanoindentation is proposed. The results are compared with observations extracted from nanoindentation in which classification of hydration products is based on the elastic modulus of the different categories of calcium silicate hydrate (C-S-H). The results show that the degree of hydration, the degree of reactivity, and silicate polymerization increase under the elevated curing condition compared with the ambient condition. It seems that C-S-H generated by the pozzolanic reaction of nanosilica in OWC paste has not only different composition but also different packing density sensitive to curing conditions.

A hybrid adaptive neuro-fuzzy interfacial systems–imperialist competitive algorithm (ANFIS-ICA) was presented to determine the effect of concentration of alkali solution, alkali binder to alkali solution weight ratio, alkali activator to ordinary portland cement (OPC) weight ratio, oven curing temperature, and age of curing on the compressive strength of OPC-based geopolymers. Optimization of the type and number of membership functions was carried out by ICA while the training, testin,g and validating of the collected data sets was conducted by ANFIS. The obtained results indicated that the proposed ANFIS-ICA model is capable to predict the compressive strength of geopolymeric specimens well and suitably determine the effect of each parameter on this property. A parametric study is presented to show the effect of each parameter predicted by the model on compressive strength of the specimens.

With the rise in the adoption of recycled aggregate for construction, investigation on ways to improve its quality has been wide spread. The major factor that affects the quality of recycled aggregate is the large amount of cement mortar that remains on the surface of the recycled aggregate. This attached mortar results in higher porosity, higher water absorption rates, and thus a weaker interfacial zone between new cement mortar and aggregates, weakening the strength and mechanical performance of concrete made from recycled aggregate. This paper attempts to compare the effect of chemical as well as mechanical treatment approaches in reducing the mortar attached to aggregate. Six series of concrete mixtures are prepared using natural aggregate, recycled aggregate, recycled aggregate treated with HCl and ${\mathrm{H}}_2{\mathrm{SO}}_4$, recycled aggregate obtained after scrubbing treatment, and heating and scrubbing treatment. The physical and mechanical properties of these aggregates, and their strength and performance of recycled aggregate concrete are determined. The results show that treatment with ${\mathrm{H}}_2{\mathrm{SO}}_4$, and heating and scrubbing yield, aggregate with reduced water absorption and other desired properties of natural aggregate. The concrete made out of these treated aggregates are able to achieve strength and performance characteristics on par with natural aggregate concrete.

The need for quality control in the ready-mixed concrete industry is increasingly emerging as a tool for ensuring the achievement of the highest possible quality in the produced concrete with the lowest practical price. In typical construction projects, the compressive concrete strength is the most important criterion in judging the acceptability of a produced concrete batch from a given plant. Variability in the compressive strength of the concrete batches of any plant is inevitable. Such variability has led researchers in the field of quality control to analyze the statistics of these results in order to draw conclusions about the quality of the concrete plant and ways to improve it. Ultimately, the goal of the owner of a structure being constructed, the engineer in charge of its construction, and hence the quality control professionals is the safety of the structure that the concrete is intended to be used for constructing. The quality of the concrete can be viewed as a means for the end goal, the structural safety. Therefore, a more informed decision could be made regarding the quality of the concrete if the structural safety is used as an indicator. Structural reliability theory and tools are commonly used nowadays for the quantification of structural safety under uncertainty. In this study, an approach for classifying the quality of ready-mixed concrete using structural reliability as a metric will be proposed. The influence of the statistical parameters of concrete on the structural reliability of the structural elements constructed with this concrete is investigated. Classification charts for classifying the quality of concrete based on the values of its statistical parameters and with reference to the attained structural reliability are proposed.

The effects of three superabsorbent polymers (SAPs) on variations in the cement hydration process were studied by calorimetric measurements and the X-ray scanning technique. It was concluded that the influence of superabsorbent polymers on workability and autogenous shrinkage strongly depends on SAP water absorption/desorption kinetics. Gradual release of additional water stored by a SAP facilitated the formation of a denser and more homogenous cementitious matrix. The addition of fly ash to portland cement had a notable influence on the hydration process and microstructure development in mortars regardless of modifications by the SAP. Characteristic patterns attributed to pozzolanic reactions appeared to be related to the mortar densification measured by the X-ray absorption and quasi-adiabatic calorimetry techniques during the first 48 h.

Conventional asphalt binder material strongly absorbs solar energy due to its black color. The consequent high surface temperature of asphalt pavement during the summer accelerates rutting, impairs long-term durability, and causes undesirable environmental impacts (i.e., heat island effects and volatile gas emissions). The black surface of asphalt also leads to high thermal emissivity and a fast rate of temperature drop under severe cold weather conditions. Thermochromic materials are substances that can reversibly change their colors in response to temperature variations. This study presents innovative, multifunctional thermochromic asphalt binder that is designed to modulate the surface temperature of asphalt pavement, i.e., to reduce the surface temperature of pavement during hot summers and to increase the surface temperature during cold winters. Optical measurements are conducted on the thermochromic asphalt binder, which is found to be more reflective than conventional asphalt binders, and the reflectance additionally increases with temperature. Such properties were found to significantly reduce the pavement surface temperature at a typical summer day in Cleveland, Ohio. To study the effects of thermochromic materials on the mechanical performance of the asphalt binder, the thermochromic asphalts are characterized using Superpave binder performance tests. Typical testing methods have been conducted on the asphalt binders at three stages: unaged, rolling thin-film oven (RTFO) residues, and RTFO + pressure aging vessel residuals. Experimental results indicated that the penetration, phase angle, and creep rate of asphalt binder was decreased, while the softening point, viscosity, complex modulus, rutting parameter, fatigue parameter, and stiffness of the asphalt binder was increased when thermochromic powder was added into conventional asphalt binder. Furthermore, increasing the content of thermochromic powder leads to reduction in the penetration depth and creep rate and an increase of the softening point, viscosity, complex shear modulus, rutting parameter, fatigue parameter, and stiffness. Additionally, the high-temperature performance grades of the asphalt binder were enhanced with blending 3–6% black, 6% blue and red thermochromic powders. Therefore, the incorporation of thermochromic materials into asphalt pavement will potentially improve its performance and durability, especially in hot regions.

Limiting the presence of water inside an asphalt concrete (AC) pavement can slow down the process involved in water diffusion, hydration, adhesion loss, and other mechanisms of moisture damage. In the past, numerous studies have been conducted on the topic of moisture damage and permeability, but very few studies have related permeability with moisture damage in AC. This study evaluates whether such relation exists. In essence, a field survey is conducted to identify a set of pavements (bad) that suffer from moisture damage and a set of pavements (good) that do not exhibit moisture damage. Field permeability tests and coring are conducted on the pavements. Laboratory permeability tests are performed on the field cores. An indirect tensile strength ratio (TSR) of wet- to dry-conditioned core samples is determined in the laboratory and used as a moisture damage potential parameter. Wet conditioning is performed by using a recently developed moisture-induced sensitivity test (MIST) device and a well-known AASHTO test method. Average field permeability of good pavements ($k=56\times {10}^{-5}\mathrm{cm}/\mathrm{s}$) is found to be less than the average field permeability of bad pavements ($k=87\times {10}^{-5}\mathrm{cm}/\mathrm{s}$). Both MIST and the AASHTO test method show a reduction in TSR value, which means moisture damage occurred during both conditioning methods. However, MIST showed a poor correlation, whereas the AASHTO test method showed a fair correlation between permeability and TSR. This study concludes that moisture damage is related to the permeability of AC.

This work introduced a novel method to prepare activated crumb rubber by using ultrasonic focusing apparatus, which could more significantly improve the compatibility between the activated crumb rubber and virgin asphalt compared with ordinary crumb rubber. The obtained activated crumb rubber was used for the synthesis of activated crumb rubber modified asphalt (ACRMA) by blending virgin asphalt, activated crumb rubber, and certain additives (e.g., SBS, antiaging agent, filler). The performance test results indicated that ACRMA had better performance than the ordinary crumb rubber modified asphalt, in terms of high-temperature property, low-temperature stiffness, ductility, especially fatigue resistance, and aging resistance. In this case, the application of novel method of activated crumb rubber synthesis could accelerate the material acceptance rate in pavement engineering.

This study aims to establish the influence of curing time and the amount of lime and porosity in the assessment of the Mohr-Coulomb failure envelope of fly ash–lime-treated soils based on unconfined compressive strength (${\sigma }_c$) and splitting tensile strength (${\sigma }_t$) of such materials. Founded on the concept that the ${\sigma }_t/{\sigma }_c$ relationship is unique for each specific fine-grained soil, fly ash, and lime blends, it is shown that the angle of shearing resistance of a given lime-treated soil is independent of the porosity and the amount of lime of the specimen and that cohesion intercept is a direct function of ${\sigma }_c$ (or ${\sigma }_t$) of the improved soil, which depends of the porosity and volumetric amount of lime of the soil–fly ash–lime blends. Finally, the concepts are tested with success for a sandy soil treated with fly ash and lime at distinct curing time periods, considering moderate to strong cementation levels.

This study describes an experimental investigation of the methylene blue test to determine the methylene blue value (MBV) and quantitatively generate the soil-water characteristic curve (SWCC) for unbound aggregate material based on the predicted percent fines content (PFC). The traditional methylene blue test has been improved significantly in terms of time, sample size, and method for analyzing the results. These improvements enable the methylene blue test to be not only a laboratory test but also a field test. This improved methylene blue test methodology is used to generate the SWCC for unbound aggregate material. The relationship between the MBV and the PFC value is established. The principles of unsaturated soil mechanics are taken into account to develop regression models for determining the four fitting parameters in a previously developed SWCC equation by using the predicted PFC value, which are then used to generate the SWCC for the unbound aggregates. The proposed method is validated by a comparison between the measured and predicted suction values for various unbound aggregate materials. This method is capable of generating the SWCC far more efficiently than any previous laboratory method, and it can even be used in field investigations because the methylene blue test requires limited portable test equipment. These improvements widen methylene blue test applications and allow for the development of the SWCC without requiring difficult laboratory experiments. Finally, the slope parameter, $b_f$, in the SWCC equations is found to be associated with the moisture susceptibility of flexible base materials. A higher $b_f$ value indicates that the material is more moisture susceptible. This finding is successfully validated by the results from the permanent deformation test.

In order to reduce costs and prevent environmental pollution in the fabrication process of straws fibrosis, a simple and efficient method of straw reinforcing asphalt concrete is proposed, which means to add short-thin straw pieces (STSP) into asphalt mixture directly by matching the size distribution of STSP and the aggregate spacing of asphalt mixtures. The road performances were testified in terms of the properties of bending, rutting and Marshall stability of the prepared straw asphalt concrete (SAC) samples. The results show that the flexural strength of asphalt mixture increased by 6%, the dynamic stability increased by 54% (reached 1,592 times) while the rut depth decreased by 24%. In addition, based on the analysis of the adhesion, shear lag and bridging effect of STSP, etc., a mechanism of enhancement is illustrated.

A completely recyclable concrete (CRC) is designed to have a chemical composition equivalent to the one of general raw materials for cement production. By doing so, this CRC can be used at the end of its service life in the cement clinkering process without need for ingredient adjustments, and with improvement of the resource efficiency of cement and concrete production. Copper slag is interesting as an iron source for the production of such a CRC and can be added to concrete, either as alternative binder or as aggregate. By isothermal calorimetry and compressive strength tests it was found that the addition of copper slag as cement replacement is of minor interest. But a study toward the compressive strength and durability of concrete with copper slag as aggregate replacement had promising results. The performance of these concretes was comparable with or even better than the reference concrete, regarding strength and most durability aspects such as porosity and permeability, and resistance against carbonation and chloride ingress. Only the resistance to freeze-thaw attack with deicing agents was inferior.