Mix Design Characteristics Research Articles

Effect of Antistripping Additives on the Cohesion, Adhesion, and Performance of Different Asphalt Mixtures in Dry and Wet Conditions

Most available tests of asphalt mixture performance against moisture damage or the effect of additives examined the asphalt mixture’s overall performance. Considering the different mechanisms of moisture damage, studying antistripping additives’ effect on failure mechanisms might provide a better view of the asphalt mixture’s performance against moisture. Accordingly, herein, the effects of various antistripping additives, including a liquid antistripping additive (dodecylamine) and a nano-magnesium hydroxide additive, each at two bitumen weight percentages, with two types of aggregates with different mineralogical properties and a PG 64-16 bitumen on moisture damage mechanism were investigated. The cohesion and adhesion mechanisms of moisture damage were examined using the pull off test, and the asphalt mixture’s overall performance was assessed using the indirect tensile strength (ITS) test in multiple dry and wet conditions (1, 2, and 3 freeze-thaw cycles) according to the modified Lottman test. The results revealed that the use of 0.4% dodecylamine and 1% nano-magnesium hydroxide in the mixtures made with lime aggregates increases the tensile strength ratio (TSR) from 62.67% to 85.4% and 84.8%, respectively. In mixtures made with granite aggregates, TSR increased from 54.45% to 72.49% and 71.35%, respectively. The failure mechanisms’ assessment showed that the use of 1% nano-magnesium hydroxide in mixtures made with granite aggregate elevated the pull off in the adhesion failure mechanism by 80%, and the pull off increased by 70% in the cohesion failure mechanism. Moreover, the pull off increased by 63% for limestone mixtures in the cohesion failure mechanism and by 56% in the adhesion failure mechanism. The dodecylamine additive with the highest pull off and ITS ratio in all freeze-thaw cycles was more suitable than nano-magnesium hydroxide to promote the asphalt mixtures’ overall performance against moisture. The statistical analysis also indicated the significant effect of dodecylamine and nano-magnesium hydroxide additives on asphalt mixtures’ moisture sensitivity reduction at a 95% confidence level. The findings show that some additives have a stronger effect on adhesion strength and some effect on cohesion strength, but the additive that better improves the overall asphalt mix performance depends on mix design characteristics and aggregate and bitumen type.

Influence of Industrial By-Product Materials on Bituminous Concrete Mixes

In this research work, laboratory studies are aimed at using copper slag and foundry sand as mineral fillers and fine aggregates as partial replacement of traditional mineral fillers and fine aggregate particles and will help in building sustainable roadways. The aggregate gradation corresponding to the bituminous concrete mid-limit grading-2 was adopted in accordance with Section 500 of Table No. 500-18 of MORT&H's Fourth Amendment Specifications in order to examine the mix design characteristics. From the laboratory investigation it is observed that the stability, tensile strength, water resistivity, dynamic stability, resistance to rut depth, resistance to proportional rut depth, and resistance to wheel tracking slope of the bituminous concrete mixtures improved with increasing CSMF, FSMF, and CSFAMF content in BC-2 mixture. However, the poor interlocking property of FSFAMF reduces its strength. Thus, the research study has indicated that the application of copper slag and foundry sand would minimize the quantity of traditional aggregate required in highway construction.

Concrete in a severe freezing environment: a meteorological characterization

When comparing the different test methods for concrete resistance to scaling and the crucial lack of correlation between laboratory test results and field results, the representativeness of these methods can be questioned. Many researchers have tried to clarify most of the mechanisms involved in the damage due to scaling, as well as thermal parameters influencing damage intensity. However, what can be noted is that predicting the degradation in relation to the mix design characteristics remains unreliable and seems to be disconnected from the performance on site. Moreover, the interpretation of the test results also presents difficulties, appearing to contradict the first-order parameters (e.g., minimum freezing temperature or freezing rate). These considerations have led us to undertake measurement campaigns to characterize the temperature response of concrete to a severe freezing environment, this environment being itself fully characterized by a set of relevant meteorological parameters measured on a field site, very close to the samples. In this paper, we present the results of 3 years of meteorological measurements (2013–2016) from two concrete blocks placed in a complete meteorological station located in a severe freezing environment. The temperature measurements were taken from an XF4 concrete block equipped with thermocouples, placed at a depth of 2 and 8.5 cm, and from the temperature of the air mass coming from a Stevenson shelter with double shelf in opposite orientation, both compared to the laboratory thermal cycle according to CEN/TC12390-9 (Slab test). While the latter gives a very symmetrical and periodic temperature signal, the former tends to be characterized by a strong asymmetry and irregularity in profile and full amplitude. We show that the natural conditions are very far from the laboratory conditions in terms of full amplitude, freezing rates and the frequency of freezing–thawing cycles. In addition, we show that these field conditions are representative of a severe freezing environment according to the EN 206 standard, in the French Alps as well as in the Nordic conditions such as can be found in Norway, Sweden and Finland.

In-Place Density of Asphalt Pavements: Case Study during Cold Weather Paving

Late-season paving is common and often performed in colder temperatures, which is the most challenging environment for attaining optimal in-place density and compaction. The in-place density of asphalt pavement greatly affects the life span of the pavement. This case study aims to evaluate and compare the effectiveness of different compaction, delivery, and mix design characteristics to ensure the optimization of in-place asphalt pavement density. To this end, four test sections were constructed over four separate days of paving during cold weather conditions. The in-place density was measured using four methods: (1) conventional or traditional cut roadway cores, (2) combination of infrared continuous thermal scanning (ICTS) with conventional or traditional cut roadway cores, (3) nonnuclear density gauge (NNDG), and (4) rolling density meter (RDM) utilizing ground-penetrating radar (GPR). The results revealed that during cold weather paving, the material transfer vehicles (MTVs) provide an effective method to minimize thermal segregation and therefore provide improved temperature and density consistency. In addition, the combination roller provided a consistent improvement compared to the standard three double-drum steel roller compaction method. It was shown that ICTS is an effective measuring technique, especially for paving in cold weather conditions, since it provides real-time information to the producer for improving temperature consistency that will result in more uniform densities. The use of nondestructive testing equipment can also strengthen the acceptance procedure in a more rigorous way by increasing the testing frequency.

Mechanical properties of Cold Recycled Bituminous Mixes with Crumb Rubber

Cold mix recycling technologies based on asphalt emulsion have been acknowledged for allowing to reduce the environmental burdens associated with road pavement maintenance and rehabilitation. In fact, mixing and placement are conducted at lower temperatures leading to energy savings, a reduction of asphalt aging, fume and odour releasing, and a general decrease of airborne emissions. However, there are still several concerns related to the high variability of reclaimed asphalt pavement (RAP), the lack of standard mix-design procedures and the fair/low mechanical performance often achieved especially due to poor moisture resistance. On other side, the addition of crumb rubber into hot mix asphalts is considered an environmentally-friendly and cost-effective practice in several countries. Producing bituminous cold mixes containing crumb rubber to develop a “greener” paving material with a performance level comparable to that of conventional materials, represents a great challenge to materials engineering. This paper presents the results of a laboratory investigation concerning the mixdesign characteristics of cold 100%-recycled asphalt emulsion mixes, using crumb rubber to improve cold recycling engineered properties. Mechanical and volumetric properties were assessed through dynamic modulus and indirect tensile strength on dry and water-conditioned specimens.

An Experimental Investigation on the Effect of Addition of Ternary Blend on the Mix Design Characteristics of High Strength Concrete using Steel Fibre

This paper presents the results of M60 grade of concrete. M60 grade of concrete is achieved by maximum density technique. Concrete is brittle and weak in tension and develops cracks during curing and due to thermal expansion / contraction over a period ot time. Thus the effect of addition of 1% steel fibre is studied. For ages, concrete has been one of the widely used materials for construction. When cement is manufactured, every one ton of cement produces around one ton of carbon dioxide leading to global warming and also as natural resources are finishing, so use of supplementary cementitious material like alccofine and flyash is used as partial replacement of cement is considered. The effect of binary and ternary blend on the strength characteristics is studied. The results indicate that the concrete made with alccofine and flyash generally show excellent fresh and hardened properties. The ternary system that is Portland cement-fly ash-Alccofine concrete was found to increase the strength of concrete when compared to concrete made with Portland cement or even from Portland cement and fly ash.

Superpave evaluation of higher RAP contents using WMA technologies

In this study, the objective was to conduct an investigation of Superpave mix design characteristics of WMA technologies in terms of various high percentages of reclaimed asphalt pavements (RAPs). One PG 58-28 binder, two PG 64-22 binders, and two RAP sources were selected from South Carolina. In addition, three mix technologies (e.g. hot mix asphalt (HMA), foaming technology, and Evotherm additive) were employed to produce the mixtures. Meanwhile, four RAP contents of 20%, 30%, 40%, and 50% (by weight of total mixture) were utilized to blend with virgin materials. 36 Superpave mix designs were conducted to explore the volumetric characteristics of various mixtures. In this study, the results indicated that, all mixtures have an optimum asphalt content (OAC) less than 5.0%, and most of these values are close to a minimum OAC value of 4.5% set by South Carolina Department of Transportation (SCDOT). No noticeable increases at the mixing and compaction temperatures for these mixtures containing a higher percentage of RAP (i.e., over 40%) were found in this study. In addition, the voids in mineral aggregate (VMA), voids filled with asphalt (VFA), dust/asphalt ratios, and moisture susceptibility meet the requirements of SCDOT’s specifications. Therefore, these specific mix designs could be used as the guidelines for developing a set of specifications for a higher percentage of RAP in terms of warm mix asphalt technology.

Statistical Modeling of Carbonation in Concrete Incorporating Recycled Aggregates

Durability and recycling are two major concerns in the construction industry. Concrete carbonation may impair reinforced concrete durability as it favors the onset of reinforcement corrosion. The use of recycled aggregates, as a replacement for natural aggregates, in construction applications is a feasible way of recycling given materials from construction and demolition waste. The aim of this study is to quantify the contribution of potential conditioning factors to the carbonation rate of concrete incorporating recycled aggregates. For this purpose, a multiple linear regression technique was used, considering the mix design characteristics, environmental conditions, and recycled aggregates’ properties as explanatory variables, capable of predicting the coefficient of carbonation. The investigation was founded on ample experimental data, collated from several studies. This study proposes a general model, in which the carbonation in concrete depends on the 28-day compressive strength, clinker content, environment’s CO₂ content, and aggregates’ equivalent water absorption. The models are statistically significant, with determination coefficients suggesting high correlation between the coefficients of accelerated carbonation of concrete in the experimental data and values predicted by the proposed models.

English

In the post globalization era, India is witnessing significant growth in every sector which is evident by rapid growth in infrastructure developments. The country is building a huge network of expressways, national highways and rural roads and improvement programs involving large investments. The durability of the road surfaces depends largely on the type and quality of bitumen used and quality control exercised in the production, transportation, mixing, and compaction, to cope up with ever changing rapid growth of laden vehicles with time posing heavy stresses on roads. It is the prime responsibility of researchers, contractors to use such material which modifies the properties of Bitumen and imparts additional strength, elasticity and other beneficial properties to make it better able to withstand high traffic loads, extreme weather conditions and other forms of stresses. Previous studies on CRMB 55 for moderate climatic areas suggest that use of it leads to excellent pavement life, driving comfort and low maintenance. In this present study, initially paper deals with scientific analyses physical properties for crushed stone aggregate for Dense Bituminous Macadam (As Per MoRTH Table: 500-8). Properties are carefully accessed of CRMB 55 with and without addition in small doses of Chemical Zycosoil to fulfill the basic requirements of standard codes. Different mix design characteristics were determined out using Marshall Method for Dense Bituminous Macadam using CRMB 55 with and without addition in small doses of Chemical Zycosoil.

Effect of Using Polymers on Bituminous Mixtures Characteristics in Egypt

Attention has been increasing towards the use of polymer modified asphalt, because conventional asphalt mixtures cannot resist the high axle loads and tire pressures. Several classes of modified binders have been used in asphalt pavements. The main objective of this research was to evaluate the effect of adding several types of polymers on asphalt cement and asphalt concrete mixtures. Experimental program involved two phases. The first phase was modifying the asphalt using six types of polymers then evaluating the properties of the modified asphalt. The second phase was evaluating the effect of binder modification on Marshall mix design characteristics and indirect tensile strength of the asphalt concrete mixtures. It was found that the optimum percentage of PVC, plastic bags and novolac was 4%, and the optimum percentage of HDPE was 5% by weight of asphalt. These percentages caused increase in kinematic viscosity, stability, and indirect tensile strength and caused reduction in penetration.

Relationship between Material Characteristics of Asphalt Mixtures and Highway Noise

Traffic noise is a main source of total environmental noise. The major component of traffic noise is the interaction between tire and pavement. One way of reducing traffic noise is to engineer pavements such that tire–pavement noise is minimized. The objective of this research was to investigate the relationship between the tire–pavement noise generation (and absorption) and the material characteristics of asphalt pavements. This paper presents the impact of material mix design characteristics, as well as linear viscoelastic properties on sound absorption. To focus on the relationship between the noise and the internal material characteristics, a novel laboratory tire–pavement noise measurement system was developed. Although the individual material characteristics did not have an appreciable influence on the damping of sound, a strong correlation between the sound pressure level and a combination of several material characteristics was observed.

Mixing of concrete or mortars: Distributive aspects

This article describes an experimental methodology offering efficiency criteria for granular materials in terms of their mixing distributive capability. The methodology is based on analyzing the distribution kinetics of colored tracer particles which were demonstrated to respond similar to cement particles during mixing. The effect of certain critical parameters such as the mixer type, the volume and the mixer speed are investigated. The influence of mix design characteristics on distribution is also presented for several mixer types. Finally, a comparison of the dispersive versus the distributive capability is achieved for several (mixer, mix design) systems, which opens opportunities for defining rules for transfer and extrapolation.

Effect of Construction Quality, Temperature, and Rutting on Initiation of Top-Down Cracking

Top-down cracking (TDC) is a flexible pavement distress caused by a number of factors, including high contact stresses from truck tires, mix design characteristics (e.g., binder type and aggregate gradation), and poor construction quality (e.g., segregation and compaction methods). This paper presents the findings of a study seeking to quantify the effect of those factors on TDC. The study consists of a laboratory component involving an accelerated wheel-tracking device and a modeling component involving a 3-D nonlinear viscoelastic finite element model. The laboratory component of the study involved 17 asphalt bituminous slabs constructed to simulate the variation in material properties observed in the field as part of an earlier forensic TDC study. The effect on TDC of air voids, bitumen content and type, aggregate gradation, and segregation were studied under three temperature conditions. Air voids, segregation, and binder content were found to have a significant effect on TDC for all temperatures tested. Modeling the TDC involved laboratory testing to establish the viscoelastic and tensile strength properties of the asphalt mixtures tested. It was found that the rutted surface contributes significantly to TDC initiation.

Effect of Construction Quality, Temperature, and Rutting on Initiation of Top-Down Cracking

Top-down cracking (TDC) is a flexible pavement distress caused by a number of factors, including high contact stresses from truck tires, mix design characteristics (e.g., binder type and aggregate gradation), and poor construction quality (e.g., segregation and compaction methods). This paper presents the findings of a study seeking to quantify the effect of those factors on TDC. The study consists of a laboratory component involving an accelerated wheel-tracking device and a modeling component involving a 3-D nonlinear viscoelastic finite element model. The laboratory component of the study involved 17 asphalt bituminous slabs constructed to simulate the variation in material properties observed in the field as part of an earlier forensic TDC study. The effect on TDC of air voids, bitumen content and type, aggregate gradation, and segregation were studied under three temperature conditions. Air voids, segregation, and binder content were found to have a significant effect on TDC for all temperatures tested. Modeling the TDC involved laboratory testing to establish the viscoelastic and tensile strength properties of the asphalt mixtures tested. It was found that the rutted surface contributes significantly to TDC initiation.