Temperature Shrinkage Research Articles

Laboratory investigation of solid wastes combined with tunnel slag in cement stabilized base of asphalt pavement

To coordinate the disposal and resource utilization of bulk solid waste iron ore tailings sand (IOTS) and hazardous solid waste phosphogypsum (PG), this paper has carried out the research of using the two and the tunnel slag in the pavement base, including unconfined compressive strength, splitting strength, compressive resilience modulus, frost resistance, temperature shrinkage, and dry shrinkage tests. According to the characteristics of phosphogypsum (PG), the water stability, delayed compaction, and leaching of toxic substances were studied, and the mechanism was analyzed by SEM and XRD. It is concluded that tunnel slag and IOTS are great filling materials; The inclusion of PG inhibited the hydration of cement, which results in the reduction of unconfined compressive strength and splitting strength in the early stage, and the higher mean coefficient of thermal contraction; When the content of PG did not exceed 6%, the frost resistance, water stability, and drying shrinkage coefficient performed well, and the delayed forming strength had almost no loss, providing support for the continuous construction technology of the road base and the inhibition of reflective cracks. Applying a large number of solid wastes to road engineering can not only efficiently handle various waste buildup problems but also produce a new form of road materials with important social, economic, and environmental benefits.

СТІЙКІСТЬ ДО РОЗТРІСКУВАННЯ АСФАЛЬТОБЕТОНУ, НАСИЧЕНОГО ДОРОЖНЬОЮ СІЛЛЮ, ПРИ ЗАМОРОЖУВАНІ

The article deals with issues of resistance to cracking at low temperature, low-temperature characteristics of asphalt concrete, tensile strength in bending, and the ratio of tensile strength to bending deformation, which reflects the flexibility of asphalt concrete.When the temperature is relatively low, the asphalt concrete should have a certain deformation capacity, and the temperature shrinkage crack can be reduced under the low temperature condition. The ultimate flexure tensile strain at low temperature is closely related to the performance of asphalt. Increasing the viscosity of asphalt can improve the low-temperature crack resistance of pavement

Investigation on Shrinkage Characteristics of Polyester-Fiber-Reinforced Cement-Stabilized Concrete Considering Fiber Length and Content

Polyester-fiber-reinforced cement-stabilized concrete is widely adopted to prevent the shrinkage cracking in pavement engineering. However, the effects of fiber length and content on the dry shrinkage and temperature shrinkage are not clear. The relationship between shrinkage resistance and strength is also discussed scantily. Hence, five types of polyester fiber length (1 cm, 3 cm, 5 cm, 7 cm, and 9 cm) and six types of polyester fiber content (0.1‰, 0.3‰, 0.5‰, 0.7‰, 0.9‰, and 1.1‰) were selected to prepare the fiber-reinforced cement-stabilized concrete. The dry shrinkage coefficients and temperature shrinkage coefficients were used to evaluate the shrinkage resistance. Moreover, the relationships among these shrinkage coefficients, compressive strength, and splitting strength at different curing ages were investigated to realize the prediction of shrinkage resistance of polyester-fiber-reinforced cement-stabilized concrete. This study aimed to seek the optimal fiber characteristics and conveniently evaluate the shrinkage resistance for the polyester-fiber-reinforced cement-stabilized concrete. Results show that: increasing the content of polyester fiber can significantly improve the shrinkage resistance of cement-stabilized concrete, especially for the temperature shrinkage. The fiber length should not be too long, especially for dry shrinkage. The optimum fiber content and fiber length is 0.7‰ and 5 cm for the dry shrinkage resistance and 0.7‰ and 9 cm for the temperature shrinkage resistance. There was higher correlation between compressive strengths and shrinkage coefficients, while the correlation between splitting strength and shrinkage coefficients was not obvious.

Stabilization of Aeolian Sand for Pavement Subbase Applications Using Alkali-Activated Fly Ash and Slag

Using local materials to construct building elements as well as transport road facilities, including highways, intercity roads, and roads, in remote areas is a top topic of scholarly research all over the world. The main reason for that is the fact that these kinds of materials not only ease the intensity of material transportation but are also cost-efficient. In desert areas, aeolian sand is a commonly used local material and it has been investigated in unbound and cement-stabilized pavement base/subbase applications. However, the production of cement is associated with a high carbon footprint, leading this research to seek alternative low-carbon binders. This research investigated the strength properties and the carbon footprint of fly ash (FA) and a ground-granulated blast-furnace slag (S)-based geopolymer-stabilized aeolian sand. Setting time, compressive strength, California bearing ratio (CBR), and temperature shrinkage measurements of the stabilized aeolian sand were carried out in this research. The maximum strength of the stabilized aeolian sand was found at the optimal ratio of Si/Al ratio of 2.5 and Na/Al ratio of 1.0. The compressive strength increased as the geopolymer stabilizer content increased. A stabilizer content ranging between 8% and 20% is recommended in practice. The carbon footprint of the geopolymer-stabilized aeolian sand was lower than that of cement-stabilized aeolian sand. This tendency became more evident in the samples with higher strength, indicating the effectiveness of geopolymer as an alternative green soil stabilizer to traditional Portland cement.

Resurfacing Performance Evaluation of Recycled Mixture with High Content of Iron Tailings Sand

ITS is the main component of industrial solid waste, of which there are about 2 billion metric tons in China. A large number of ITS not only occupy land resources and pollute the environment but also pose major security risks. This study, based on a road resurfacing project in Shanxi Province, China, focused on the “iron tailings sand (ITS) plus reclaimed inorganic binder stabilized aggregate (RAI)” solid waste treatment method, which uses special cementitious material to stabilize ITS and RAI as a new base course material and aims to replace new aggregates by 100% to apply in the renovation project through testing the road performances of the recycled mixture. Although it does not comply with the conventional grading range, the new ITS and RAI mixture (the recycled mixture) can achieve excellent compressive performance from the material composition, and it can meet different levels of design strength under various load conditions by adjusting the mixing ratio (ITS content can reach up to 70%). The pavement performance of the recycled mixture was compared with that of cement-stabilized aggregate (the traditional base course material), and it was evaluated by testing its anti-water damage, frost resistance (dry and wet freeze), shrinkage, and fatigue characteristics. A total of 380 mixtures were tested. The results showed that, at the same strength level, the anti-water damage and frost resistance properties of the recycled mixture were better than those of cement-stabilized aggregate, whereas its shrinkage and fatigue properties were inferior. For anti-water damage properties, the water stability coefficient of the recycled mixture is about 2%~5% higher than that of cement-stabilized aggregate. For the frost resistance property, the wet frost coefficient of the recycled mixture is about 10%~15% higher, and the dry frost coefficient is about 5%~10% higher. The dry shrinkage strain of the recycled mixture is about 50 × 10−6~300 × 10−6 higher than that of cement-stabilized aggregate, and the temperature shrinkage coefficient is about 10 × 10−6~20 × 10−6 higher. Thereafter, the reduction of carbon emissions in engineering applications per kilometer was compared between the recycled mixture and cement-stabilized aggregate. The engineering application in Shanxi Province shows that the carbon reduction is approximately 18.869 t of CO2. In a word, the recycled mixture has excellent pavement performance and reduces carbon emissions.

Frost Resistance and Shrinkage Characteristics of Soil Stabilized by Carbide Slag and Coal Gangue Powder

With the increase of expressway construction in seasonal frozen soil region, the freeze-thaw problem of subgrade soil has attracted more and more attention. In addition, the comprehensive utilization of industrial solid waste has become an important measure to build a resource-saving and environment-friendly society. In order to improve the frost resistance of subgrade soil and realize the resource utilization of industrial solid waste, carbide slag (CS) and coal gangue powder (CG) were applied to the subgrade soil. The unconfined compressive strength (UCS) test, freeze-thaw cycle test, dry shrinkage test, temperature shrinkage test and scanning electron microscope (SEM) test were carried out on CS-CG stabilized soil with a ratio of CS:CG = 70:30 and dosages of 5%, 10% and 15%. The freeze-thaw cycle degradation model of CS-CG stabilized soil was constructed to show the freeze-thaw deterioration mechanism after the mechanical properties, pore structure, and durability characteristics of the stabilized soil were examined. The results showed that the CS-CG stabilized soil had good frost resistance. After 6 freeze-thaw cycles, the UCS at 7d and 28 d was 2.86 MPa and 3.79 MPa, respectively, which were 22.6% and 35.5% lower than in samples that underwent no freeze-thaw action. The CS-CG stabilized soil had good crack resistance, slightly better dry shrinkage strain than lime stabilized soil, and excellent temperature shrinkage performance. With the increase of CS-CG dosage, the hydration products increased continuously. After freeze-thaw cycles, however, large pores and cracks gradually appeared in the stabilized soil, which led to an increase of porosity and pore diameter, and a decrease of pore abundance. Due to the influence of hydration degree, the porosity change at 7 d was less than that at 28 d. There was a f(n)/f0=βexp−λΔh relationship between UCS residual ratio and porosity variation of the CS-CG stabilized soil, and it had a good correlation. The CS-CG stabilized soil had good frost resistance and shrinkage characteristics, and could replace traditional cementitious materials such as Portland cement (PC) and lime for subgrade soil improvement in regions with seasonal frozen soil. Future research needs to focus on the performance regulation of CS-CG stabilized soil, which can make it more widely used.

Exploring the Mechanical Properties, Shrinkage and Compensation Mechanism of Cement Stabilized Macadam-Steel Slag from Multiple Perspectives

Steel slag is characterized by high strength, good wear resistance and micro-expansion. This study aims at exploring the potential of steel slag in cement stabilized aggregates, mainly including mechanical properties, shrinkage and compensation mechanisms. For this purpose, the compressive strength and compressive resilient modulus of cement stabilized aggregates with different steel slag contents (CSMS) were initially investigated. Subsequently, the effects of steel slag and cement on dry shrinkage, temperature shrinkage, and total shrinkage were analyzed through a series of shrinkage test designs. Additionally, in combination with X-ray diffraction (XRD) and Scanning electron microscope (SEM), the characteristic peaks and microscopic images of cement, steel slag and cement-steel slag at different hydration ages were analyzed to identify the chemical substances causing the expansion volume of steel slag and reveal the compensation mechanism of CSMS. The results show that the introduction of 20% steel slag improved the mechanical properties of CSMS by 16.7%, reduced dry shrinkage by 21%, increased temperature shrinkage by 5.8% and reduced its total shrinkage by 19.2%. Compared with the hydration reaction of cement alone, the composite hydration reaction of steel slag with cement does not produce new hydrates. Furthermore, it is noteworthy that the volume expansion of the f-CaO hydration reaction in steel slag can compensate for the volume shrinkage of cement-stabilized macadam. This research can provide a solid theoretical basis for the application and promotion of steel slag in cement-stabilized macadam and reduce the possibility of shrinkage cracking.

Durability Performance of PVA Fiber Cement-Stabilized Macadam

To further improve the durability of cement-stabilized macadam and guarantee the use quality and sustainability of a semi-rigid base, the current study was carried out. With the help of a dry shrinkage test, temperature shrinkage test, freeze–thaw bending test, and fatigue test, the effect of incorporating PVA fiber on the deformation characteristics of cement-stabilized macadam was analyzed, and the changes in low-temperature residual toughness of the mixture before and after modification were compared. The low-temperature toughness of PVA fiber cement-stabilized macadam was evaluated with the help of the standard toughness evaluation method. The fatigue life prediction equation of PVA fiber cement-stabilized macadam was established based on the Weibull distribution. The results showed that PVA fiber can effectively improve the deformation characteristics, low-temperature toughness, and fatigue performance of cement-stabilized macadam. The low-temperature residual flexural tensile strength and low-temperature bearing capacity were increased by 10.3% and 55.3%, respectively. The residual toughness indices were increased by 58.6%, 88.1%, and 98.3% and the residual strength index was increased by more than 100%. The fatigue life was improved by 178~368% under different stress intensity ratios. The fatigue life values obeyed the two-parameter Weibull distribution, and the correlation between the fatigue life prediction equation and the measured data was significant. The fatigue life prediction error was between 0.03 and 4.9% under different stress intensity ratios.

Investigation on temperature shrinkage characteristics of the combined structure in asphalt pavement

The temperature shrinkage of materials primarily causes transverse cracking. Current research mainly focuses on the temperature shrinkage of single materials. This work aims to analyze the effect of the structural combination on temperature shrinkage. To this end, the temperature rise method was first discussed to measure the shrinkage coefficient to replace the traditional temperature drop method. Then, the temperature shrinkage coefficients of the lime–fly ash-stabilized macadam, and ATB and AC asphalt mixtures were measured. The effect of gradation types, lime–fly ash content, and nominal maximum aggregate size on the temperature shrinkage was studied. Finally, the temperature shrinkage of composite structural characteristics was analyzed. The results show that the difference between the temperature shrinkage coefficients obtained by temperature rise and drop methods was relatively small. Thus, the temperature rise method can be used to measure the temperature shrinkage coefficient. In addition, the lime–fly ash-stabilized macadam with the suspended dense gradation or a higher lime–fly ash content has the largest temperature shrinkage strain. The suspended dense gradation should be avoided, and the content of lime–fly ash should be approximately reduced to control the temperature shrinkage strain of the semi-rigid base course. As for the asphalt mixture, the temperature shrinkage strain increased with the decrease in the nominal maximum aggregate size. The asphalt mixture with a larger nominal maximum aggregate size should be given priority to control the temperature shrinkage. Finally, when combined with the base course or surface layer, the temperature shrinkage of the base course was promoted by the surface layer, while the base course inhibited the surface layer. Meanwhile, the mutual influence between the semi-rigid base course and the surface layer was more substantial than that of the mutual influence between the flexible base course and surface layer.

Study on the Causes of Highway Pavement Cracks in Desert Environment

According to relevant statistics, more than 90% of domestic high-grade asphalt pavement is semi-rigid base pavement, and semi-rigid base cracking is a congenital stubborn disease and common. In Tengger Desert section of Wuma expressway, the temperature difference is large, and the cracking of temperature shrinkage and dry shrinkage is difficult to avoid, resulting in the decline of pavement structure strength. Once the semi-rigid base is cracked, the asphalt pavement is equivalent to a flexible structure; the residual fatigue strength is greatly reduced; the long-term service performance of pavement structure can not be guaranteed; the durability is poor, the damage layer is deep; the repair is difficult and the cycle is long; maintenance costs are relatively high. This paper analyzes the causes of pavement cracks in the harsh environment in the hinterland of Tengger Desert, and studies its mechanism and treatment scheme.

Effects of coarse aggregates on the mechanical properties, durability and microscopic behaviour of mortar rubble

A new type of slope protection structure, mortar rubble arch slope protection, has good low-temperature performance, and it is mostly used in the seasonally frozen area of North China. To determine the effects of aggregate type (basalt, granite, limestone) and amount of coarse aggregate on mortar rubble, mechanical properties were measured and durability experiments were conducted. Compressive strength, bending strength, mechanical damage characteristics of the materials, freeze–thaw loss rates and temperature shrinkage coefficients were recorded. The results were verified by microscopic observations. Using the digital image correlation (DIC) test system, the main form of the bending failure of the mortar rubble was observed to be failure around the aggregate. Acoustic emission parameters were used to accurately reflect the damage characteristics of the mortar rubble during the compression test. The resistance time of basalt before failure was long, and its peak energy was high. The durability test results showed that granite mortar rubble had better frost resistance, a higher freeze–thaw resistance factor, and less temperature shrinkage deformation than the basalt and limestone rubbles, and it is more suitable for slope protection in cold areas. Scanning electron microscopy (SEM) results showed that the matrix entered the pores to form new bonds, which was the main reason for the high strength of the basalt specimens. The basalt mortar rubble interface was severely damaged after freezing and thawing. The optimal amount of added aggregate was approximately 60%-70%, which resulted in good mechanical properties and durability of the mortar rubble. When the flake aggregate content exceeded 70%, the strength and durability of the material decreased.

Study on crack resistance of cement-stabilized iron tailings

ABSTRACT Iron tailings constitute a significant type of industrial solid waste. The use of iron tailings to wholly or partly substitute natural gravel in a cement-stabilized base is an effective technique for high-quality and large-scale use. This study replaced natural gravel with iron tailings of 25%, 50%, 75%, and 100% to develop a cement-stabilized iron tailing base (IT-CSG). Additionally, the drying shrinkage, temperature shrinkage, fatigue properties, and unconfined compressive strength of IT-CSG were investigated. The results reveal that owing to the large porosity of iron tailings and adsorption of more water, the internal water content of the IT-CSG mixture increases with an increase in iron tailings content. Consequently, the cumulative water loss rate of IT-CSG increases, and the drying shrinkage strain increases. The average temperature shrinkage coefficient of IT-CSG gradually increases as the iron tailing content increases owing to the larger porosity and space for temperature shrinkage deformation in the IT-CSG. Therefore, the fatigue equation of IT-CSG is established, indicating that fatigue life decreases slightly with an increase in iron tailing content. Notably, the fatigue life of IT-CSG positively correlates with cement dosage. Furthermore, the unconfined compressive strength of IT-CSG gradually decreases as the iron tailing content increases.

Spatial Nonlinear Simulation Analysis on the Temperature Shrinkage Effect of a Super-Long Frame Structure Considering the Construction Process

The temperature shrinkage effect is a very important factor causing the cracking of super-long frame structures. Current design codes and recommendations for reinforced concrete (RC) structures consider the influence of the construction process on the temperature shrinkage effect by adopting a uniform reduction coefficient and neglect the influence of the construction method. However, different construction processes can vary the temperature stress of the structure. In this paper, under cooling action, the temperature stress of a one-layer, super-long frame structure with different quantities and indwelling times of post-cast strips is calculated with a spatial nonlinear simulation analysis program by adopting the degenerated spatial solid virtual laminated element method. With this approach, the internal force state of each construction stage during the construction process is accounted for in a nonlinear mechanical model of the structure. The results show that the quantity and the indwelling time of post-cast strips can effectively vary the temperature stress of the structure. Meanwhile, the quantity of the post-cast strips can have a more obvious effect than the indwelling time. Therefore, the construction process is an important factor affecting the temperature shrinkage effect of the structures. The research results can provide a valid reference for the design and construction of super-long frame structures.

Optimum utilization of recycled aggregate and rice husk ash stabilized base material

• The unconfined compressive strength and splitting strength of the mixture increased with adding recycled aggregate. • The flexural tensile strength decreased with the increase of RHA content. • After adding recycled aggregate, the dry shrinkage of the mixture was improved. • It is suggested that the content of RHA should not be higher than 40%. With the development of the economy and society, a huge amount of construction and biomass waste are produced every year. Improper disposal of waste will cause pollution to air, soil and groundwater. The sustainable recycling of construction and biomass waste has important benefits for environmental protection. In this paper, the influence of different rice husk ash (RHA) content on the road performance of cement stabilized base material with recycled aggregate was studied in terms of strength, frost resistance and shrinkage. The proportion of RHA replacing cement is 0%, 20%, 40%, 60%, 80% of cement quality, and construction waste recycled aggregate was used to replace 40% of natural aggregate. The main conclusions are as follows: the unconfined compressive strength and splitting strength with recycled aggregate decrease with the increase of RHA content, the compression resilience modulus and flexural tensile strength of the mixture increased obviously, but the frost resistance deteriorated. The dry shrinkage coefficient and temperature shrinkage coefficient of the mixture containing recycled aggregate increased linearly with the increase of RHA content. For the mixture mixed with recycled aggregate, it is recommended that the RHA content should not exceed 40%.

THE EFFECT OF COMBINATION VEGETABLE TANNING MATERIALS AND SULPHITED OIL ON THE PHYSICAL PROPERTIES OF JACKET LEATHER

This research was aimed to determine the combination of vegetable tanning materials and Sulphited oil on the physical properties namely tensile strength, oil content, elongation, softness and shrinkage temperature and determine the factors that affect tensile strength, oil content, elongation, softness and shrinkage temperature leather tanning results. Raw hides/skins were processed up to acidification, pH was set to be 5 then tanned with the variation of vegetable tannin 15%, 17,5% and 20% respectively. Fatliquoring process used sulphited oil with variation of 12%, 15% and 18%. The jacket leather produced were tested using SNI 4593:2011. From this combination of treatment provided 9 (nine) treatment variation, each treatment was preformed triplicate. The results showed that the combination of vegetable tanning materials, 17.5% and 12% of sulphited oil was the result of variation in the optimum treatment for the leather to produce 208.29 N/mm2 tensile strength, oil content of 10.02%, 50.39% elongation and softness 5.13 mm and meets the requirements of SNI 4593: 2011 with the temperature shrinkage was at 79 oC. From the analysis of variance showed vegetable tanning material is the dominant factor affecting the tensile strength, oil conten and shringkage temperature. Sulphited oil is a factor that affects the oil content, elongation and softness.
 Keywords: jacket leather, vegetable tanning agent, sulphited oil

Experimental Study on the Road Performance of High Content of Phosphogypsum in the Lime–Fly Ash Mixture

Phosphogypsum (PG), as a by-product of the production of phosphoric acid, faces the problems of large annual output and difficult treatment. There is a large demand for fillers in the process of road paving, which may be an effective method for the utilization of PG resources. In this study, three proportions of phosphogypsum–lime–fly ash (PLF) mixture were designed, first, according to orthogonal tests. The comprehensive performance of the PLF mixture was tested by the compression rebound modulus test, unconfined compressive strength test, flexural tensile strength test, dry shrinkage test, and temperature shrinkage test, respectively. The results show that adding crushed stone to the PLF mixture can effectively improve the compression rebound modulus, unconfined compressive strength, and flexural tensile strength. The high content of PG in the mixture can also improve the dry shrinkage and temperature shrinkage properties of the mixture. According to the road layer requirements, the optimum proportion of the PLF mixture is recommended, which may benefit the road construction and PG resources.

Utilization of Steel Slag in Road Semi-Rigid Base: A Review

Steel slag (SS) is industrial waste, and there is a large amount of SS to be treated in China. Its disposal generates severe environmental pollution. One of the best ways to use SS is as a road base material. This paper reviews the possibility of using SS in semi-rigid base and evaluates the performance of SS base course. The interaction between three stabilizers (cement, lime–fly ash, and cement–fly ash) and SS is analyzed, and the influence of modifier content on the performance of base course is evaluated. The potential laws between SS, curing time, and unconfined compressive strength, as well as drying shrinkage and temperature shrinkage, are discussed and their effects on the performance of the base course are revealed. The finite element method, discrete element method, and molecular dynamics can be used to analyze the freeze-thaw, rutting resistance, and crack development of SS base. In addition, compared with traditional macadam base, the CO2 emissions for the use of SS base are slightly more, one of the disadvantages of its use in production, transportation, and compaction. However, considering the overall mechanical, economic, and environmental benefits, it is recommended to use SS in semi-rigid base course. The future research scope of SS as base material is suggested.

Mechanical Properties, Durability and Leaching Toxicity of Cement-Stabilized Macadam Incorporating Reclaimed Clay Bricks as Fine Aggregate

The utilization of reclaimed clay brick (RCB) from construction and demolition (C&D) waste is an extremely troublesome problem, which is beneficial and necessary for environmental protection and resource conservation. The objective of this study is to evaluate the mechanical properties, durability and environmental impact of cement-stabilized macadam (CSM) incorporating RCB. The physical and chemical properties of RCB were characterized by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) technologies. RCB exhibited a porous surface micro-morphology, high water absorption and pozzolanic activity. The higher RCB substitution ratio resulted in a lower unconfined compressive strength of CSM. Meanwhile, the higher the RCB substitution ratio was, the larger the 90 d indirect tensile strength of CSM at the late curing period. The RCB substitution ratio within 50% was beneficial for the freeze-thaw resistance of CSM. Additionally, RCB had a smaller aggregate size, causing a negative influence on the anti-scouring property of CSM. CSM incorporating RCB had an overall increasing accumulative water loss rate, and average coefficients of dry shrinkage and temperature shrinkage, except that 20% RCB substitution ratio resulted in an excellent dry shrinkage property. Based on the chemical analysis of EDTA-2Na, the pozzolanic RCB reacted mainly at later curing to form the crystal structure, enhancing the interfacial transition zone. Additionally, the leaching solutions could meet the identification requirements for extraction toxicity, surface water and groundwater referring to Chinese standards. Utilizing RCB in road engineering as the substitute for natural aggregate would be a promising step forward to sustainable development and green construction.

TEMPERATURE DEFORMATIONS OF PVC WINDOW PROFILES WITH REINFORCEMENT

Modern window structures made of PVC profiles can experience significant temperature deformation during both winter and summer operation. This effect is not considered in the current engineering methods of PVC windows calculation, which causes a number of problems in their operation (freezing and blowing through the windows, the failure of fittings, etc.). The use of laboratory methods of testing windows for temperature loads is limited due to their labor intensity and the high cost of testing equipment. We propose to develop an engineering method for calculating the mechanical operation of PVC windows under the action of temperature loads, which can be used at an early stage of design. One of the stages of its creation is a theoretical description of the temperature deformation of a PVC window profile when it works together mechanically with a reinforcing core. The article describes the nature of the forces transmitted by the PVC profile on the core during thermal bending (the case of temperature deformation at negative outside temperatures is considered). It was proposed to decompose these forces into two components: longitudinal, caused by different values of temperature shrinkage of PVC profile and reinforcing core, and transverse, caused by thermal bending of PVC profile. Mathematical models have been developed to calculate both force components and temperature deformation of the profile at different numbers and spacing of attachment points. A physical model has been proposed for implementation in the numerical calculation program, which allows a more accurate description of the temperature deformation of a long profile. Calculation of the test problem according to the proposed methodology and by means of full-fledged three-dimensional finite-element modeling in the COMSOL Multiphysics program was performed. A comparison of the results showed a discrepancy of less than 10%. It was found that the key influence on the deformations of PVC window profiles with a reinforcing core will have characteristics of the outermost joints "PVC profile – reinforcing core", because the greatest forces arise in them under the action of temperature loads.

Performance evaluation and enhancement of composite cold recycled mixture based on vibration mixing

Composite cold recycled mixture is commonly used in pavement regeneration. The performance of it, including the unconfined compressive strength, splitting strength, dry shrinkage, temperature shrinkage and freeze-thaw resistance, are studied based on vibration mixing with different blending ratios of asphalt surface and cement-stabilized base. The results show that vibration mixing can effectively improve the mixing uniformity of the recycled mixture and increase the strength by up to 30 %. Besides, the change of reclaimed asphalt pavement (RAP) admixture will affect the mechanical performance and road performance of the recycled mixture. When the admixture of RAP material is 30 %, the strength is the highest, and when the admixture is 40%, the dry shrinkage is the smallest. The temperature shrinkage coefficient decreases with the increase of RAP material admixture, and the freeze-thaw resistance is enhanced with the increase of RAP material admixture.