Penetration Resistance Test Research Articles

Effect of Waste PET Fiber on the Mechanical Properties and Chloride Ion Penetration of Emergency Repair Concrete for Road Pavement.

This study evaluated the effects of adding waste PET fibers on the mechanical properties and chloride ion penetration of latex-modified ultra-rapid hardening cement concrete used for emergency road pavement repairs. The primary experimental variable was the content of waste PET fibers. The mechanical properties of the concrete were evaluated through compressive strength, flexural strength, and splitting tensile strength tests. Its durability was evaluated through chloride ion penetration, surface resistivity, and abrasion resistance tests. The experimental results were compared with the quality standards for emergency repair concrete set by the Korea Expressway Corporation. As a result, this study has enhanced the strength and resistance to chloride ions of latex-modified concrete by incorporating waste PET fibers. In the mixture with 3.84 kg/m3 of waste PET fibers, the compressive strength was 29.9 MPa at 4 h and 42.5 MPa at 28 curing days. The flexural strength was 6.0 MPa at 4 curing hours and 7.0 MPa at 28 days, and the splitting tensile strength was 4.5 MPa at 28 days of curing. The chloride ion permeability amount and abrasion depth were 1081C and 0.82 mm, respectively. The mixture with 3.84 kg/m3 of waste PET fibers has superior compressive strength, flexural strength, splitting tensile strength, chloride ion penetration, and surface resistivity compared to the mixture with 7.68 kg/m3. This result means that the waste PET fibers caused poor dispersion and fiber-balling within the concrete, leading to loose internal void structures when incorporated at 3.84 kg/m3. However, the abrasion resistance test showed better results for the mixture with 7.68 kg/m3 of waste PET fibers than the 3.84 kg/m3 mixture. Therefore, the test results indicated that 3.84 kg/m3 of waste PET fibers is the most effective for latex-modified concrete used in emergency road pavement repairs.

Experimental Research on the Performance of Recycled Waste Concrete Powder (RWCP) on Concrete.

Waste concrete is a large amount of solid waste produced in the process of urban construction and renewal in China. Its resource utilization is of great significance for saving mineral resources and improving urban environmental quality. The present study was designed to investigate the effects of mechanical grinding time on the particle size distribution and activity of recycled waste concrete powder (RWCP). Combined with unconfined compressive strength, slump, electric flux and chloride ion penetration resistance tests, the effects of RWCP on the mechanical properties, working performance and impermeability of concrete were analyzed, and the phase and microstructure of concrete containing RWCP were analyzed by XRD and SEM. The results showed that the RWCP is mainly composed of quartz, gismondine, C2S, cancrinite and portlandite. The optimum activity of RWCP obtained by ball milling for 45 min was 44.41%. RWCP can improve the fluidity of concrete and shorten the initial setting time of concrete. When the blast furnace slag in the concrete was replaced by the RWCP, the early strength and impermeability of the concrete decreased. When RWCP replaced blast furnace slag by 69.1%, the UCS of the concrete at 1, 3, 7, and 14 d decreased from 9.56, 22.1, 34.1, and 41.2 MPa to 5.9, 14.5, 22.7, and 33.2 MPa, respectively. While RWCP replaced fly ash, the normal strength of concrete increased with the increase in fly ash replacement amount. When RWCP completely replaced FA in concrete, the 28-day strength of the concrete increased from 45.2 MPa to 50.8 MPa. The impermeability results showed that the appropriate substitution of RWCP for fly ash was beneficial to increase the impermeability of concrete while excessive substitution reduced. Based on these results, the RWCP has the potential for large-scale application in the preparation of concrete.

Influence of chemical admixtures on buildability and deformation of concrete for additive manufacturing

In this study, the buildability of three-dimensionally (3D) printed (3DP) concrete that uses coarse aggregate was evaluated in the fresh state according to the contents of three chemical admixtures (high-range water-reducing agent (HRWRA), viscosity-modifying agent (VMA), and setting-time modifying agent), and the correlation between fluidity changes and buildability was analyzed. Polycarboxylate HRWRA and VMA contents were varied to control the flowability and static yield stress, which affect the workability. In addition, the SMA content was varied, and slump tests and table flow tests were performed at 30-minute intervals up to 6.5 h after mixing to measure flowability. Simultaneously, static yield stress was measured to analyze rheological changes, and penetration resistance and green strength tests were performed to analyze the main factors influencing buildability over time. The highest buildability was observed when the VMA content was 1.5 %. The static yield stress of fresh concrete could be ≤3000 Pa to guarantee adequate 3DP concrete transport performance while that at 1 h after mixing could be ≥2000 Pa to secure buildability. When the penetration resistance of fresh concrete is ≥80 kPa, the deflection of concrete may be <10 %. Through this, buildability can be approximately judged based on penetration resistance.

The Usefulness of Soil Penetration Resistance Measurements for Improving the Efficiency of Cultivation Technologies

The research results of soil penetration resistance (SPR) tests carried out on sandy clay using four cone probes with different dimensions of the measuring tip are presented in this study. It was indicated that the values of SPR can be used to diagnose the cultivation layer and, on this basis, determine whether it is necessary to cultivate it and select tools for the required treatment. Tests were carried out on three levels of soil density, 1.37, 1.43 and 1.51 g∙cm−3, and two moisture contents, 7.64% and 10.4%. The results show that the probe with the smallest cone with apex angles of 30° and 60° on the least dense soil indicated higher SPR by over 50% more than other probes with the highest cone and the same opening angles. The change in cone opening angle from 30° to 60° led to an increase in probe indications in the range of 10–25%, depending on the diameter of the cone tip. The statistical analysis shows that values of probe indications were statistically significant and were influenced by soil density, probe cone tip dimensions, the surface of the base and the apex angle. The values of SPR are fundamental in diagnosing the quality of the soil’s top layer, determining the necessity of breaking it up, and selecting the optimal tools for this procedure. To improve the efficiency of agricultural crop cultivation technologies. This is particularly important when carrying out cultivation procedures in an environmentally friendly manner. The measurements will help support the introduction of sustainable farming practices, including direct seeding, no-till cultivation, or precision agriculture, reducing soil degradation and increasing environmental benefits.

Effects of early vibration and resistant strategies on bond performances between high-strength concrete and rebar

The local bond performances between rebar and high-strength concrete (HSC) exposed to early vibration were experimentally investigated in this study. In addition, three vibration-resistant strategies, including additions of special rapid-hardening cement(calcium sulphoaluminate cement, CSA), shrinkage compensation admixture (expansion agent, EA), and toughening metallic fibers (steel fiber), were verified through penetration resistance, compressive, and central pull-out tests, respectively. Finally, two-way ANOVA tests were conducted to understand the significance of each strategy from a statistical perspective. The results demonstrated that early disturbances compromise bond performances by weakening chemical adherence and mechanical interlocking effects, which considerably degrade bond strength and stiffness. The presence of EA delayed the setting and hydration of concrete and prolonged vibration-sensitive duration. However, the later expansive hydrate products effectively strengthen the bond performances and compensate for early-stage vibration-induced damage. In comparison, the synergetic effects between CSA and Portland markedly enhance the hydration reactivity of blends at early stages, which can achieve threshold maturity and vibration resistance within hours. However, excessive CSA (10%) severely compromises the construction time of mixtures and amplifies the cracking potentials of HSC under the constraints of steel bars. The synergetic effects of steel fibers and aggregates formed disordered networks to enhance the vibration resistance and rigid skeletons for bridging cracks of HSC. The two-way ANOVA results indicate that EA significantly improves the mechanical performances of HSC, followed by steel fibers. The additions of expansive agents and steel fibers are highly recommended in engineering with vibration scenarios. In contrast, the dosages of CSA (or similar early-strength agents) should be carefully controlled unless with a robust shrinkage compensation strategy.

Mechanical properties of polyolefin and polypropylene fibers-reinforced concrete–An experimental study

Concrete, a widely used construction material, exhibits inherent brittleness and limited tensile strength. To address these shortcomings, the incorporation of fibers has gained prominence, with polyolefin and polypropylene fibers emerging as promising reinforcements. This study experimentally conducted and examined the mechanical characteristics of polyolefin and polypropylene fibers-reinforced concrete. The study involved conducting compressive strength tests and durability tests, including sulfate resistance, acid resistance, chloride ion penetration resistance, and abrasion tests. The results demonstrated a notable enhancement in the compressive strength of both cubic and cylindrical specimens with varying dimensions, owing to the inclusion of polyolefin fibers. Polyolefin fibers exhibited a greater reinforcing effect compared to polypropylene fibers, especially in larger cubic specimens and cylindrical specimens. The quantitative results show that specimens with polypropylene fibers exhibited a 9.67 % improvement in compressive strength, while those with polyolefin fibers showed a 30.47 % enhancement compared to specimens without fibers. The acid resistance test revealed that both types of fiber-reinforced specimens exhibited higher compressive strength in acidic environments compared to plain concrete specimens. In the chloride ion penetration resistance test, the polyolefin fiber-reinforced specimen demonstrated the highest resistance to degradation, while the plain concrete specimen exhibited the lowest resistance. Polyolefin demonstrated superior reinforcement compared to polypropylene, with a 35 % increase in acid resistance and better chloride ion resistance. In contrast, specimens without fibers weakened by 35.36 % in a chloride environment. The sulfate resistance test showed that the polyolefin fiber-reinforced specimen had the highest compressive strength in a sulfate environment, while the plain concrete specimen had the lowest. In sulfate and abrasion tests, polyolefin-fiber-reinforced specimens displayed the highest resistance and the lowest abrasion rate of 34.6 %. These findings highlight the potential of polyolefin fiber-reinforced concrete for enhancing mechanical properties and durability in various applications.

Development of cementitious capillary crystalline waterproofing agents and durability study of concrete in the presence of chloride with sulfate in aqueous environment

In this study, the chemical composition of cementitious capillary crystalline waterproofing agents (CCCW) was developed by using the water penetration resistance test method. Response to impermeability by first permeability and self-healing properties by second permeability, five effective single components were obtained: Ethylene diamine tetraacetic acid (EDTA), l-aspartic acid, sodium sulfate, sodium silicate and nano-silica. With the help of chloride ion diffusion coefficient measurement and sulfate attack resistance test, it investigates the effect of five components on the durability of the concrete matrix. According to the differential thermogravimetric analysis (TG), X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis methods, the waterproof mechanism of each component acting in the matrix was proposed. Finally, also combined with the results of macroscopic performance and microscopic analysis designed orthogonal experiments, the results show that the optimal blending of five waterproofing agent components up to 300% increase in substrate impermeability. The optimal amount of each component is 0.5% EDTA, 2% l-aspartic acid, 3% sodium sulfate, 2% sodium silicate, and 2% nano-silica.

Effect of artificial interior stone sludge on physicomechanical properties of mortars

Artificial interior stone is a decorative building material, which mostly consists of quartz. Sludge is generated during the stone manufacturing process, and the amount of sludge is increasing due to the high demand; however, most of the generated sludge is disposed of in landfills. In the present study, the effects of the sludge addition on the physicomechanical properties of mortars were investigated via flowability, penetration resistance, mercury intrusion, and compressive strength tests. The independent variable was the replacement ratio of the sludge to the fine aggregate. The test results showed that the addition of the sludge reduced the flowability, and initial and final setting times, while the percentage of the pores involved in the hydrates increased. The compressive strength of mortars with the sludge was improved compared to that of the mortars without the sludge. Quantum chemistry simulations were conducted to understand the strength enhancement mechanism of the specimens, and a straightforward machine learning-based model equation was proposed by applying the experimental variables and measurement results.

Evaluation of Setting Times of Concrete Using Electro-Mechanical Impedance Sensing Technique.

This study presents a novel approach to assessing the setting time of concrete using the electro-mechanical impedance (EMI) sensing technique. The proposed method involves the continuous monitoring of EMI changes by embedding a piezoelectric (PZT) sensor directly in the concrete. A comparative analysis was conducted with the conventional penetration resistance test, which utilizes mortar samples extracted from the concrete. As a result of the experiment, the time deviation rate of the setting time was more than 10% in the penetration resistance test using the mortar sample extracted from the same concrete, whereas the time deviation rate of the setting time was up to 1.77% in the EMI sensing technique using the same concrete specimen. This highlights the effectiveness and potential of the EMI sensing technique for an improved evaluation of concrete setting time.

Early-Age Cracking Behavior of Concrete Slabs with GFRP Reinforcement.

This paper reports on a combined experimental and numerical modeling investigation of cracking of concrete slabs with GFRP reinforcement. At this stage of the project, attention is given to early-age cracking driven by plastic shrinkage, preceding longer term considerations of cracking resistance over the service life of field applications. Of interest is the effectiveness of GFRP reinforcement in restricting plastic shrinkage cracking. Nine small-scale slab specimens were subjected to controlled evaporation rates. Images of crack development were acquired periodically, from which crack width estimations were made. Comparisons were made between slabs reinforced with conventional steel and those reinforced with GFRP, along with control specimens lacking reinforcement. During the period of plastic shrinkage, the time of crack initiation and subsequent crack openings do not appear to be influenced by the presence of the reinforcing bars. To understand this behavior, six early-age bond tests were conducted for both types of the bars after 1, 2, and 3 h exposure to the controlled evaporation rate. In addition, concrete strength development and time of settings were measured using penetration resistance tests on a representative mortar. The numerical modeling component of this research is based on a Voronoi cell lattice model; in this approach, the relative humidity, temperature, and displacement fields are discretized in three-dimensions, allowing for a comprehensive investigation of material behavior within the controlled environment. Based on the measured bond properties, our simulations confirm that the reinforcing bars restrict crack development, though they do not prevent it entirely.

Enzyme induced carbonate precipitation with fibers for the improvement of clay soil slopes against rainfall and surface runoff erosions

In order to improve the erosion resistance of the highway embankment slopes against rainfall and surface runoff erosions, the enzyme induced calcium carbonate precipitation (EICP) technology combined with different types of fibers, including steel, glass, and Polypropylene (PP) fibers, was studied for the treatment of the cohesive soil slope surface. The treatments were applied by a two-step method. In the first step, the treatment solutions were sprayed to the soil surface. In the second step, after the cracks were fully developed, quartz sand was filled into the cracks and another round of EICP spray treatment was applied in order to repair the cracks. Soil crack image analysis, crack repair test, rainfall and surface runoff erosion test, surface penetration resistance test, moisture content measurement, and soil microstructure analysis were carried out. The results show that the EICP technology can effectively cement the soil and improve the mechanical strength and erosion resistance of the cohesive soil slope. The average penetration resistance is about 10 times that of the untreated samples. The strength and erosion resistance of the fiber-added samples were further improved after EICP treatment with the addition of fibers. Both the glass fiber- and steel fiber-added samples exhibited excellent erosion resistance under rainfall and surface runoff erosion, with the amounts of eroded particles 35.78% and 1.89%, respectively, as compared with the sample treated with EICP only. The additions of fibers did not have any negative impact on the conversion efficiency of calcium. Meanwhile, the fibers could function together with calcium carbonate to form a net structure inside the soil so as to increase the strength and the durability, and reduce the water infiltration into soil. Therefore, the EICP treated samples with steel fibers and glass fibers have better treatment effects and are recommended for further applications.

Preparation and characterisation study of water hyacinth briquettes

Biomass-based briquetting is widely used to improve waste combustion efficiency, management, and treatment. This work focused on the novel utilisation of water hyacinth found in Kerala freshwater lakes for briquetting. Water hyacinth is an aquatic weed considered an environmental challenge to Kerala's aquatic life and social life. This study uses water hyacinth to create a novel mixture for commercial briquette manufacture, which is then compared to more traditional biomass-based briquettes made from sawdust, coffee husk, paper, and wood chips. The prepared briquettes were subjected to mechanical and thermophysical characterisation research for a comparison study. Moisture content test, shatter resistance test, water penetration resistance test, impact resistance test, calorific value, and water boiling tests were conducted. Water hyacinth briquette showed the lowest moisture content of 2.95 % and comparatively significant impact resistance and shatter resistance. The characterisation study confirmed that water hyacinth could be used as the primary biomass in a briquetting process, yielding a viable alternative fuel.

Mechanical properties and energy absorption capacity of plain and fiber-reinforced single- and multi-layer cellular concrete

Cellular concrete has been widely used in geotechnical, non-structural, and structural applications because of its low density and easiness of handling. Due to its high energy absorption capacity, the material is also viable for applicants, such as the engineering material arrested system (EMAS) and emergency escape ramp (EER). However, commonly used single-layer or uniform cellular concrete often does not exhibit desirable structural functionality and efficiency under loading, as the material tends not capable of withstanding load after peak load is reached. Multi-layer cellular concrete (MLCC) could possess the solution by withstanding increasing loads at different layers as the MLCC failed or compressed layer by layer. Moreover, fibers can strengthen and improve cellular concrete's structural integrity by bridging the initial cracks. This paper evaluates the compression, push-in penetration, impact resistance, and flexural performance of plain and fiber-reinforced single-layer cellular concrete and MLCC. Results show that MLCC can maintain structural integrity under compression even after completely fracturing the weaker layers. Similarly, results from push-in (penetration) resistance tests also exhibit multiple peak loads when the penetrator reaches different layers, indicating the potential to respond effectively to varying levels of stress. For impact resistance, MLCC exhibits higher absorption capacity and better structural integrity with fewer cracks observed. While plain MLCC showed similar peak acceleration to the lower-density cellular concrete (400 kg/m3) used in this study, fiber-reinforced MLCC exhibited approximately 27% lower peak acceleration compared to the lower-density fiber-reinforced cellular concrete. The study also demonstrated significant structural integrity improvement in cellular concrete when fibers are incorporated, with peak loads and maximum displacements improved by approximately 82%, and 470%, respectively, when MLCC is placed under flexure load.

CPT-based design method for helical piles in sand

Helical piles are used extensively for low and medium rise developments and are a popular foundation solution in cases where resistance to significant uplift loads is required. The ability to re-use helical piles and recent interest in their use as foundations in offshore wind and solar energy applications has renewed interest in improving existing design methods. This paper presents the results from field investigations in medium dense and dense sand that examine effects on the axial tension and compression capacity of varying the helix pitch, shaft diameter, advancement ratio and shaft tip geometry. The results from the 20 pile tests conducted (many of which included instrumentation) indicate low sensitivity to a range of the investigated parameters and a strong correlation of the capacity to the cone penetration test resistance. A design method based on these findings is proposed for typical helical pile geometries and is shown to provide predictions that are generally within 10 to 15% of the axial capacities reported for 30 other well documented pile tests reported in the literature. The method, referred to as UWASP-22, incorporates a simple means of estimating the load-displacement response of a helical pile as well as a formulation enabling prediction of the installation torque which is a common quality control measure for helical piles.

A PCA-Based Approach for Very Early-Age Hydration Monitoring of Self-Compacting Concrete Using Embedded PZT Sensors.

This work proposed a novel approach based on principal component analyses (PCAs) to monitor the very early-age hydration of self-compacting concrete (SCC) with varying replacement ratios of fly ash (FA) to cement at 0%, 15%, 30%, 45%, and 60%, respectively. Based on the conductance signatures obtained from electromechanical impedance (EMI) tests, the effect of the FA content on the very early-age hydration of SCCs was indicated by the predominant resonance shifts, the statistical metrics, and the contribution ratios of principal components, quantitatively. Among the three, the PCA-based approach not only provided robust indices to predict the setting times with physical implications but also captured the liquid-solid transition elongation (1.5 h) during the hydration of SCC specimens with increasing FA replacement ratios from 0% to 45%. The results demonstrated that the PCA-based approach was more accurate and robust for quantitative hydration monitoring than the conventional penetration resistance test and the other two counterpart indices based on EMI tests.

An Analytical Study on Penetration and Pore Pressure Dissipation of Piezocone Test in Typical Normally and Over-Consolidated Silty Clays

The degree of the over-consolidation ratio (OCR) of silty clay affects the soil’s mechanical properties and in situ test results. The present study utilized numerical analysis to investigate the behavior of cone penetration and pore pressure dissipation in typical silty clay soils, while also taking into account the impact of the over-consolidation ratio (OCR). Effective stress finite-element analyses, which accounted for considerable deformation, were carried out at various OCRs. The model assumed the soil as a homogeneous material obeying the modified Cam Clay (MCC) model. The significant advance of this work is the evaluation of the effect of OCR on penetration resistance and pore pressure test data and the calculation formula of OCR and ch in typical silty clay. An inversion method based on the results of piezocone penetration tests was proposed in terms of strength and the over-consolidation ratio of the silty clay, which is of great importance for the inversion of soil parameters in the Yellow River Delta region. This paper presents a consolidation coefficient inversion method of typical normally and over-consolidated silty clays and corrected the disadvantage that traditional conversion methods could not take OCR effects into account.

Evaluating the Influence of Carbon Fiber on the Mechanical Characteristics and Electrical Conductivity of Roller-Compacted Concrete Containing Waste Ceramic Aggregates Exposed to Freeze-Thaw Cycling

Traditional methods of removing snow and ice from pavements using chemicals are combined with mechanical removal that involves a lot of manpower, advanced machinery, chemicals that are harmful to the environment, and damage to pavements. Furthermore, annually, large quantities of ceramic materials become waste due to their fragile nature during processing, transport, and installation, and their accumulation in the nature has brought about environmental and health-related concerns. Therefore, the study aims to investigate the effect of using waste ceramic as a replacement for fine aggregate in roller compacted concrete (RCC) and the application of carbon fiber to improve the mechanical properties and electrical conductivity of RCC. To achieve this goal, several tests such as compressive strength, indirect tensile strength, electrical resistance, chloride ion penetration, specific gravity, and skid resistance tests were carried out on the fabricated samples before and after freeze-thaw cycling exposure. The experimental results illustrated that replacing waste ceramics with fine-grained aggregate increased the compressive strength and tensile strength of RCC. Furthermore, carbon fiber increased tensile strength but had no noticeable influence on compressive strength. Freeze-thaw conditioning led to a reduction in the compressive and tensile strength regardless of the aggregate type and carbon fiber utilization. In the samples containing waste ceramic aggregate, the electrical conductivity was reduced, and by adding carbon fiber, its electrical conductivity was increased. Exposure to freeze-thaw cycling resulted in an increase in electrical resistance and the passing charge. Waste ceramic incorporation created a similar mixture in terms of skid resistance, while in contrast, the carbon fiber slightly reduced the skid resistance. In addition, freeze-thaw conditioning resulted in an increase in the skid resistance. Besides, in this study, kernelized support vector regression (KSVR) and radial bias function (RBF) neural network models were proposed to estimate the indirect tensile strength (ITS) and compressive strength (CS) values. The results showed that both models have high performance in estimating these values, but RBF was a more efficient model.

Durability evaluation of PP-ECC with local superfine sand (SSPP-ECC) serviced in seasonal frozen region

The recently developed engineered cementitious composites with local superfine sand and polypropylene fiber (SSPP-ECC) has been proved to be a kind of high ductility and toughness material with wide applicability. In view of the durability challenges to concrete structures serviced in seasonal frozen region, a series of experiments including the carbonation, freeze–thaw, coupling of carbonation and freeze–thaw, coupling of salt solution and freeze–thaw, chloride ion penetration resistance and impact resistance tests of SSPP-ECC and normal concrete were carried out to fully evaluate their durability and environmental adaptability. The test results showed that SSPP-ECC is significantly superior to normal concrete in frost resistance, and can more effectively resist the coupling effects of carbonation and salt solution on freeze–thaw, so that the specimens can maintain higher levels of integrity, dynamic elastic modulus and flexural strength. The resistances of SSPP-ECC to carbonation and chloride ion are also better than that of normal concrete, and the SSPP-ECC specimens showed ultra-high toughness under repeated impact load, while the normal concrete specimens showed obvious brittle failure. Furthermore, the comprehensive evaluations on durability of SSPP-ECC and normal concrete were in terms of fuzzy analytic hierarchy process, and it was concluded that SSPP-ECC is more durable than normal concrete suffered to multiple adverse environments, especially when serviced in seasonal frozen region.

Monitoramento do período de pega de misturas de concreto com ultrassom

Abstract The setting behavior of concrete mixtures can be indirectly monitored by the penetration resistance test given by ASTM C 403. Arbitrary values of penetration resistance are associated to the initial and final set times. This test is carried out on the previously sieved mortar portion of the concrete mixture, which makes its practical use rare. Alternatively, ultrasound testing can be used to characterize this transition period, since the propagation of ultrasonic waves is greatly affected by the formation of cement hydration products and the extent of microstructure development. In this research, the propagation of ultrasonic waves in fresh concrete during the setting period was studied. In addition to the ultrasonic pulse velocity (UPV), other ultrasonic parameters such as group velocity, parameters related to ultrasonic energy and frequency were monitored during the setting period of various concrete mixes. It was observed that as setting progressed, there was a greater ease of ultrasonic transmission with a continuous increase of wave amplitudes. The results indicated that a combined analysis of the time domain parameters of UPV, group velocity and the time that 10% of energy has propagated (t10) could be used to improve the characterization of the microstructure development regarding the setting behavior of concrete mixtures.

Laboratory Performance Evaluation of Asphalt-Treated Cold Recycled Mixtures Using Existing Practical Tests

Agencies currently utilize several proxy tests, related to level of compaction (density) and moisture content, to assess the quality of a recycled pavement during construction. These proxy tests are not completely able to indicate sufficient quality or stability of recycled pavements under trafficking or surfacing, especially at early ages. The lack of sound and rapid tests for use in process control and acceptance during construction limits the use of the recycling techniques by agencies, therefore they do not fully benefit from the advantages that pavement recycling offers. This study evaluates the viability of currently available simple and practical stiffness tests (i.e., soil stiffness gauge and light weight deflectometer tests), deformation resistance tests (i.e., Marshall hammer test), and penetration resistance tests (i.e., dynamic cone penetration test) to characterize the properties of asphalt-treated cold recycled mixtures. The scope of the work included laboratory testing of 18 different cold recycled mixtures, prepared through different processes combining different binding agents and filler types, at different curing times via the selected tests. The collected data were analyzed to evaluate these tests in relation to their repeatability characteristics and versatility to capture the performance of recycled materials with respect to changes in curing time, type of stabilizing/recycling agent, and presence of active filler. The data obtained showed the ability of these tests to capture the effect of curing. Moreover, these tests were found to be sensitive to changes in the recycling agent type, recycling agent content, and presence of active filler.