Styrene-butadiene Rubber Latex Research Articles

Innovative early age mechanical properties of 3D printable mortar enhanced with SBR latex and kaolin

As the global population has continued to grow, the costs and environmental issues associated with traditional construction materials like cement and river sand have become increasingly problematic. This study explores the innovative enhancement of early-age mechanical properties of 3D-printable mortar through the incorporation of Styrene-Butadiene Rubber (SBR) latex and kaolin. Various sands (Lawrencepur, Chenab, and Ravi) were tested at 120 min for compressive stress, direct shear strength, Young’s Modulus, and Shear Modulus. Lawrencepur Sand exhibited the highest compressive stress (206.75 kPa) and shear strength (74.60 kPa), followed by Chenab Sand and Ravi Sand. Young’s Modulus values were highest in Lawrencepur Sand (7.93 MPa), indicating superior stiffness, while Shear Modulus was highest in Chenab Sand (3.79 MPa). Ravi Sand, despite lower mechanical strengths, was found optimal for printable mortar due to its fine particle size and desirable texture. The incorporation of SBR latex and kaolin resulted in reduced maximum deflection and enhanced load-bearing capacity over time, with Lawrencepur Sand containing 99.64% sand particles and minimal silt bearing the ultimate load effectively. This study highlights the potential of SBR latex and kaolin in improving the early-age mechanical properties and suitability of sands for 3D-printable mortar, providing a balance between mechanical performance and printability.

Study on the preparation and modification mechanism of GO/SBR composite modified emulsified asphalt

This paper employs graphene oxide (GO) and anionic styrene-butadiene rubber (SBR) latex as modifiers for road-emulsified asphalt. A silane coupling agent (KH550) is used to modify GO, resulting in the development of a novel GO/SBR composite-modified emulsified asphalt. A mathematical model was optimized to determine the optimal material ratio, which was verified through performance tests. Techniques such as Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were utilized to investigate the modification mechanism. The results indicated that both the median particle size and storage stability of the GO/SBR composite-modified asphalt were enhanced, with significant improvements in mechanical properties compared to ordinary emulsified asphalt. Microscopic analysis revealed enhanced dispersion of modified GO in asphalt, and the interaction between modified GO and emulsified asphalt was determined to be purely a physical reaction. This study provides valuable insights into the application of GO in road engineering.

Enhancing lateritic soil for sustainable pavement subbase with polymer-modified cement: A comparative study of styrene butadiene rubber and styrene acrylic latex applications

This study evaluates styrene butadiene rubber (SBR) and styrene acrylic latex (SA) as modifiers in cement-treated subbase materials (CTSB) to enhance mechanical properties and reduce cement usage sustainably. Optimal ratios for stabilizing sub-standard lateritic soils were identified, reducing water demand and increasing mechanical strength in polymer-modified cement pastes. A 10 % SA and a 15 % SBR as cement replacement by mass significantly improved bearing strength and strain capacities in CTSB, signifying enhanced flexibility and elasticity. Despite slight changes in compaction characteristics, the study identified 1.6 % SA and 2.4 % SBR as optimal binder (i.e., polymer-cement mixture) contents, compared to 3.3 % cement for conventional CTSB with similar unconfined compressive strength standards. SBR-enriched CTSB exhibited superior resilient modulus, indicating stronger inter-particle bonding. The integration of SA and SBR reduced capillary rise and enhanced moisture stability. This sustainable approach enhances pavement durability and reduces CO2 emissions by minimizing cement use. The findings emphasize the potential of polymer-modified CTSB for cost-effective and environmentally friendly road construction, offering significant implications for advancing pavement engineering materials and promoting eco-friendly practices within the industry.

Vat photopolymerization of silica reinforced styrene-butadiene rubber elastomeric nanocomposites

Compared to their unfilled counterparts, elastomeric nanocomposites offer tailorable combinations of properties, including improved mechanical properties, increased durability, and enhanced thermal and electrical conductivity. However, the high viscosity caused by the presence of both the high molecular weight elastomer and the inclusion of fillers complicates additive manufacturing (AM) of elastomeric nanocomposites. This is especially challenging in vat photopolymerization (VP) AM, which requires resins that possess low viscosity (< 10 Pa·s) and exhibit sufficient storage modulus (∼ 104 Pa) when photocured. To address this process limitation, the authors have previously demonstrated decoupling the relationship between viscosity and molecular weight via VP of a photocurable composite latex resin. In this approach, a photocurable matrix is photocured as a scaffold around the latex particles, which provides sufficient modulus for the printed "green" part. Following a dehydration post-processing step, the latex particles coalesce to provide the final elastomeric mechanical properties without compromising feature resolution.In this work, the authors explore the effects of the addition of silica nanoparticles (10, 15, and 20 wt.%) on (i) the printability of photocurable styrene-butadiene rubber (SBR) latex resin and (ii) the mechanical properties of the resultant printed composites. The printable photocurable silica-SBR colloidal resin is realized by balancing the viscosity of the resin, the modulus of the cured green body, the silica nanoparticles content for reinforcement, and the high SBR content for elastomeric behavior. Specifically, the photocurable colloidal resin's viscosity is controlled by formulation design, while high silica nanoparticle content in the final part is achieved through evaporation of unreactive diluent. Characterization of the printed SBR nanocomposites with 20 wt.% silica reinforcement elucidated significant enhancements in the tensile strength (53 % increase), Young's modulus (671 % increase), and Shore A hardness (108 % increase) compared to printed SBR without filler reinforcement. To the authors' knowledge, this is the first report of 3D printing rubber nanocomposite using VP.

Effect of waste engine oil and warm mix additive on the physical, rheological, and short-term aging attributes of Styrene–Butadiene Rubber-modified asphalt binders

Styrene-butadiene rubber (SBR) latex is used widely to increase the low-temperature resistance of asphalt binders. However, the high content of butadiene copolymer in SBR-treated asphalt causes oxidation and aging. Furthermore, following the SBR modification, the compatibility and thermal storage stability of SBR-modified asphalt is not satisfactory. Therefore, the best approach to improve the quality of short-term aged SBR-modified asphalt is to lower the manufacturing temperatures of the SBR-modified asphalt mixture. In this study, to reduce the preparation temperatures of SBR-modified asphalt mixes and improve their performance after short-term aging, several additives i.e., waste engine oil (WEO), warm mix agent i.e., ZycoTherm, and WEO/ZycoTherm combination (WEO+ ZycoTherm) were selected. The rheological properties and aging performance of binder samples were evaluated through the rational viscosity, dynamic shear rheometer, bending beam rheometer and Fourier transform infrared spectroscopy tests. The results showed that adding WEO together with ZycoTherm into an SBR-modified binder contributed to reducing the compaction and mixing temperatures. The chemical analysis showed that the three additives i.e., WEO, ZycoTherm, and ZycoTherm/WEO declined the aromaticity and chemical aging indicators of aged SBR-modified binders. Furthermore, it was demonstrated that both the ZycoTherm and WEO/ZycoTherm improved the asphalt resistance to rutting at elevated temperatures in both conditions i.e., before and after short-term aging. In addition, the findings revealed ZycoTherm /WEO compound yielded the best performance to improve the minimal-temperature cracking resistance of the SBR-modified binder, resulting in lower short-term aging temperatures. In summary, this study highlights the necessity of lowering preparation temperatures in asphalt mixes containing SBR to enhance binder resistance to rutting and cracking and reduce susceptibility to oxidation during short-term aging.

Synergic Effects of Recycled Concrete Aggregate and Styrene Butadiene Rubber (SBR) Latex on Mechanical Properties of Concrete

These days Sustainable advancement is picking up notoriety all around the globe. To hold characteristic assets, reuse and reusing of development and annihilation squander is the clearest approach to achieve manageability in the development division. Presently, reused aggregate RA is been generating and CDW is its source. As of late, these squanders are reused in present day reusing offices, under great quality control arrangements which could prompt enhance its execution. An investigation is completed about the characteristics of Recycled Aggregate Concrete RAC by utilizing squashing and breaking of concrete waste got from various obliteration locales &amp; junkyard. With the end goal to upgrade the characteristics of RAC there are a few additives called as super plasticizer which are adjoined with concrete. Fixings utilized in particularly this investigation were ordinary sand, common &amp; reused aggregate &amp; additive namely Styrene Butadiene Rubber latex (SBR). Those aggregates are acquired from various assets. Sum of 144 concrete molds in system of 4 collections was framed. Gatherings were structured in such a route along these lines, to the point that the impact of reused coarse aggregate (half, 75 percent, and 100 percent), cement dose and expansion of latex of SBR in factor amounts by the cement weight of (0.5 percent, l percent, 1.5 percent) ought to be appropriately decided. For compressive quality and rupture modulus MOR, tests were done. Prior to the tests performance in the research center a diminishing pattern of twenty five (25) percent in compressive quality was taken note. An impressive decrease was seen in the properties of RAC by utilizing 100% reused aggregate when contrasted with Natural Aggregate Concrete NAC. There was negligible change in Recycled Aggregate Concrete RAC made of 75 percent (%) NA and 25 percent (%) RCA. Yet, there was ideal properties differences of concrete ended with the blend of half NA and half RCA. It was seen in the outcomes that concrete squanders might be used in arrangement of concrete subsequent to reusing them which at that point can be utilized in many concrete structures.

Study on the properties and microstructure of polymer modified waste printed circuit board cement-based materials

Waste printed circuit boards (WPCB) are solid waste, and the current disposal of WPCB in landfills has raised environmental concern. Existing studies used ground WPCB as a replacement of fine aggregate in cement-based materials, but the performances of those materials were notably decreased. This paper aims to improve the performance of WPCB-bearing cementitious materials using styrene butadiene rubber (SBR) latex and chloroprene rubber (CR) latex. For this purpose, cement-based materials with ground WPCB as fine aggregates were prepared, and the effects of SBR latex and CR latex on the mechanical properties of WPCB-bearing samples with varying dosages were studied. The influence mechanism was studied using SEM, hydration heat, XRD, and FTIR tests. The results showed that the incorporation of ground WPCB tends to significantly reduce the compressive strength of cement-based materials, while the addition of SBR and CR latex can prevent the strength loss. For instance, with the optimal dosage of 5 % for SBR latex or 7.5 % for CR, the 28-d compressive strength of the latex-modified sample was 42.6 MPa and 45.3 MPa, which was 26.78 % and 34.82 % higher than that of the unmodified samples. Through microstructure analysis, it was found that the incorporation of WPCB had a negative impact on the densification of cement-based materials. SBR latex and CR latex promoted the hydration reaction and formed continuous film products inside the structure, which improved the bonding performance of WPCB cement-based materials.

A Study on the Properties of Composite Modified Mortar with Styrene-Butadiene Rubber Latex and Silica Fume.

To solve the problem of the poor abrasion resistance of concrete pavement surface mortar, this study substituted cement with equal amounts of styrene-butadiene rubber (SBR) latex and silica fume (SF) to investigate the effects of organic/inorganic material composite modification on the fluidity, drying shrinkage, mechanical properties, and abrasion resistance of cement mortar. Also in this study, the microstructure, product, and pore structure characteristics of the composite modified cement mortar were investigated using scanning electron microscope (SEM), X-Ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and the Brunauer-Emmett-Teller (BET) method. This research found that the sole substitution of SF negatively impacted the mortar's fluidity and drying shrinkage yet enhanced its mechanical strength and abrasion resistance; the incorporation of SBR latex improved fluidity, reduced shrinkage, and increased flexural strength but adversely affected the compressive strength of the mortar. Additionally, the enhancement of the mortar's abrasion resistance with SBR latex was significantly greater than that with SF. When SBR latex and SF were used together as substitutes, the latex struggled to offset the negative impact of SF on mortar fluidity but effectively reduced shrinkage; SF compensated for the detrimental effect of the latex on compressive strength. Moreover, the primary role in enhancing the mortar's abrasion resistance was played by the latex. Microscopic tests showed that SBR latex and SF could increase the content of calcium silicate hydrate (C-S-H) gel, inhibit the formation of ettringite (AFt) and reduce carbonation, refine the pore size of cement mortar, and effectively improve the microstructure of mortar.

Suspension electrospinning of SBR latex combined with photo-induced crosslinking: control of nanofiber composition, morphology, and properties

Suspension electrospinning of a styrene-butadiene rubber (SBR) latex coupled with photo-induced crosslinking in ambient conditions is proposed as a rapid method to prepare ultrafine shape-stable rubber fibrous membranes. Polyethylene oxide (PEO) is used as template polymer and can eventually be removed from the nanostructured membrane by a simple water treatment. A multifunctional thiol crosslinker and an appropriate photo-initiating system are added to the latex to allow the fast and efficient photo-induced crosslinking of the nanofibers, based on thiol addition to the SBR double bonds, as demonstrated by real-time Infrared spectroscopy analyses. It is proved that by varying the PEO template polymer and the thiol crosslinker content, a fine control of the chemical composition, morphology, water solubility, and thermal properties of the nanofibrous membranes is ensured. Moreover, comparable mechanical properties to those of fibrous membranes produced by conventional electrospinning of organic solvent-based solutions are obtained, clearly showing the attractiveness of the present method, especially in terms of process sustainability.Graphical abstract

Compatibility evaluation between waterborne epoxy resin and SBR latex modified asphalt emulsion

Good compatibility between waterborne epoxy resin (WER) modifier and styrene-butadiene rubber (SBR) latex modified asphalt emulsion (SBRE) is an essential premise for good pavement performance of WER and SBR latex compositely modified asphalt emulsion (WSAE). This study aims to explore the compatibility between WER modifier and SBRE. To achieve the goal, several WER modifiers produced by two methods were first selected to modify SBRE, thus the WSAEs were prepared. Next, storage stability and workability of the WSAEs themselves, and high-temperature performance, rheological behavior and temperature sensitivity of their evaporated residues were compared and evaluated via performing a series of experiments, respectively, thus the WER modifier possessing an optimal modification effect was recommended. Results show that the storage stability of WSAEs is sensitive to the amount of WERs. The incorporation of 1% WERs by the mass of SBRE improves the storage stability of SBRE, while WERs that exceed 1% weaken its storage stability. When the WERs reach 3% and 4%, the 5 d storage stability of prepared WSAEs will be beyond the limitation of specification. Incorporating WERs into SBRE negatively affects the workability of SBRE, and the workability of WSAEs is adversely influenced by the WERs content and the storage time. To ensure the construction, the WSAEs with 3% and 4% WERs should not be stored for more than 36 h and 48 h, respectively. The WERs effectively improve the high-temperature performance of SBRE residue, especially the 3% WERs. Besides, the WERs notably enhance the rheological property and thermal stability of SBRE residue. In contrast, the WER modifier produced by chemically modified method has a smaller adverse impact on the storage stability and workability of WSAE, and a larger enhancement on the high-temperature performance, rheological property and thermal stability of SBRE residue, which is thus recommended to modify SBRE.

Properties of the cement containing hybrid micro-fibers and polymer latex using the orthogonal test: A comparative study of freshwater and seawater curing conditions

The enhancement of cement properties through the integration of composite materials has become a prevailing topic, as it offers a solution to the limitations associated with single-material approaches. Our study aims to explore the synergistic potential of calcium carbonate whiskers (CWs), multi-wall carbon nanotubes (MWCMTs), and carboxylated styrene-butadiene rubber latex (XSBRL) in cement under seawater curing conditions, and freshwater conditions are added as the control group. The laboratory tests including fluidity, mechanical strength, and porosity were measured using the orthogonal test design method, and the weight matrix analysis method was used to determine the optimal mix proportion. The results showed that incorporating 5%, 10%, and 15% of XSBRL increased the fluidity by 17.87%, 48.55%, and 133.09%, respectively. On the contrary, the mechanical strength decreased by 8.33%, 10.85%, and 10.09% for seawater conditions at 28d, respectively, accompanied by an increase in porosity. CWs enhanced the mechanical strength by 7.69%, 10.92%, and 12.84%, respectively, and the pore structure was densified. MWCNTs first increased and then decreased the strength, and it may be due to the agglomerative effect. The optimal mix proportions were 3% CWs content, 0.2% MWCNTs, and 10% XSBRL for freshwater conditions, while 3% CWs, 0.3% MWCNTs, and 15% XSBRL for seawater conditions. X-ray diffusion (XRD) and scanning electron microscope (SEM) were used to characterize the phase composition, mineralogy, and microstructure. Results illustrated that CWs, MWCNTs, and XSBRL would not change the mineral phases of cement, and some Friedel’s salt and more ettringite were found under seawater conditions. The crack deflection, bridging effect, whisker breaking, and pull-out effect of CWs, the nucleating effect for hydration products and the crack control ability of MWCNTs, and the three-dimensional network structures of XSBRL were responsible for the considerable modification.

Effect of polymeric fiber coating on the mechanical performance, water absorption, and interfacial bond with cement-based matrices

The performance of sisal fibers in cement-based matrices is highly dependent on the interface efficiency between the fiber and the matrix. This behavior in turn is directly related to two main factors: the sisal fiber swelling tendency and fiber alkaline degradation. To enhance these properties and consequently the fiber–matrix adhesion, this study proposed the use of carboxylate styrene-butadiene rubber latex (XSBR) as a coating for sisal fibers. Different XSBR polymers and emulsions concentrations were adopted. The effects of this treatment on various properties of the fibers such as physical, chemical, and mechanical properties were studied. The physical properties of the modified fibers were investigated by means of scanning electron microscopy (SEM) and atomic force microscope (AFM) analyses. Also, changes in the moisture absorption capacity of the coated fibers were evaluated. To study the chemical influence of the polymer coating in the modified fibers, thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) techniques were adopted. Direct tensile and pullout tests were also assessed in natural and coated sisal fibers, to mechanically evaluate the modification in terms of fiber strength and adherence, respectively. The results evidenced the formation of a new polymeric layer around the fiber, responsible to reduce the water absorption tendency of the natural fiber. The increase in the fiber–matrix adhesion obtained in the pullout evaluation was attributed to the rougher superficial aspect of the modified fibers and increased chemical interaction between the polymer and the cementitious matrix. Moreover, it was proven that the polymeric layer reduced the fiber's alkaline degradation susceptibility resulting in a more stable sisal fiber.

Modification and mechanism of polymer in high-performance concrete with full aeolian sand: An integrated macro-to-micro perspective

Producing high-performance concrete with full aeolian sand (FA-HPC) can achieve efficient utilization of desert resources to combat the shortage issue of aggregates. However, low water–cement ratio and high fine content result in a high risk of brittleness and durability in this concrete. Herein, polyacrylamide (PAM) and styrene-butadiene rubber latex (SBR) were incorporated into the FA-HPC to optimize its performance. Effects and mechanisms modifying the FA-HPC with polymers were compared and studied from macro-to-micro perspectives, with respect to workability, mechanical properties, durability, adsorption, and hydration. The results revealed a negative correlation with the PAM content (contrary to the SBR content) in fluidity and the content-dependent extension in setting time. For strength and shrinkage, the best performance was observed in the PAM-modified FA-HPC at 0.05% content presenting the substantial mitigation in brittleness. Moreover, regarding chloride resistance, SBR showed a more positive effect than PAM, with a 40.9% improvement at 10% content. From the micro-perspective observation, the retarding effect at early stages and acceleration during the late hydration process were verified by phase analysis. The polymer film and polymer bridge as well as the refined pore structure were the primary contributing factors to the performance improvement. Overall, compared to SBR modification, PAM modification with stronger adsorption capacity balances the comprehensive performance improvement of FA-HPC better at 0.05% content. Additionally, the specificity of the FA-HPC and the difference in modification behavior were discussed. This research allows the material-composition optimization of FA-HPC and further promotes the wide application of aeolian sand-based cementitious materials.

Biodegradable composite films based on mucilage from Opuntia ficus-indica (Cactaceae): Microstructural, functional and thermal properties

This study evaluated the feasibility of using cactus mucilage (CM) to elaborate biobased composite films blended with styrene-butadiene rubber latex (SBL). The CM was extracted and precipitated with ethanol (CMET) and isopropanol (CMIS). Mucilage-based films were formulated using three levels of mucilage (4, 6, and 8 wt%). The microstructure, thickness, moisture content, density, water contact angle, water vapor permeability, film solubility, thermal stability, and toughness of mucilage films blended with SBL (SBL/CMET and SBL/CMIS) were measured. The properties of mucilage-based films varied systematically, depending on the concentration of mucilage. The addition of SBL to CM film produces compatible, hydrophobic, flexible, and stiffer films with low moisture contents and good barrier properties. The mucilage film incorporated with 6 wt% CMET and CMIS reached the highest Young's modulus of 1512 ± 21 and 1988 ± 55 MPa, respectively. The DSC of produced films reveals that the Tg of SBL/CMIS is lower than that of SBL/CMIS. The synthesized films were structurally stable at high temperatures. The biodegradability of the composite films buried in the ground shows that the produced films are 100 % biodegradable after 40 days. Thus, CM blended with SBL can benefit specific applications, especially food packaging.

Hardened properties and microstructure change of sulphoaluminate cement modified with different doses of styrene-butadiene rubber latex

The composite of sulphoaluminate cement (SAC) and styrene-butadiene rubber (SBR) latex is expected to possess rapid strength development and adjustable elastic modulus, mainly used in rush repair engineering. This paper investigates the mechanical strength and drying shrinkage of SBR-SAC composites with different proportions. The change of pore structure, phase composition, and microtopography behind the composites was further revealed. Results indicate that, when the SBR/SAC ratio increases from 0/10 to 3/10, the flexural strength of the composite is increased by 343% and its compressive strength is increased by 14.7%, the drying shrinkage is almost not considered, below 0.1%. Besides, at the SBR/SAC ratio of 5/10, the composite loses brittleness, with no obvious peak value of load–displacement curves, and the drying shrinkage of composite at 23 d is 1.496%. This is because dehydrated polymer occupies the location of SAC hydrates, and the polymer film gradually and continuously covers the surface of the cement and becomes thickened. With the increasing SBR/SAC ratio, the continuous phase of composite probably transforms from inorganic cement phase to organic polymer phase.

Influence of polypropylene fiber with Styrene-Butadiene Rubber Latex bonding agent in prevention of early crack of concrete

We have fabricated the concrete reinforced polypropylene fiber with styrene-butadiene rubber latex bonding agent of concrete in different ratio. The prepared concrete employed with structural studies using FTIR and XRD spectra. An FTIR spectrum shows the important characteristics peaks of polypropylene fiber and styrene-butadiene rubber along with silica peaks. XRD pattern indicates that concrete crystal structure of three polymorphs such orthorhombic, triclinic and monoclinic phase. SEM image indicates that the above 10 wt % of polypropylene fiber causes small hairline cracks on its surface. It is found that the tensile strength increases with increase in different weight percentage of polypropylene fiber up to 10 wt %. This is may be due to the high compactness and reduction in porosity of the concrete block. It is also important to note that the water reduce admixture such as Polycarboxylates in required ratio’s significantly effects on capillary threshold by reducing 8-12 % of water results higher density of the concrete.

Development of Sustainable Concrete from Hypo Sludge Combined with Basalt Fibre and Latex

Cement production is a major source of carbon dioxide pollution. An environmentally friendly concrete needs to be developed in order to overcome the adverse environmental impacts of cement production and the continuing depletion of natural resources. Paper waste (hypo sludge) from the paper industry is becoming a challenge due to its extensive area requirements for disposal and continually increasing adverse environmental effects. To reduce paper waste and pollution, it might be beneficial to use it as hypo sludge in concrete mixes. In the present investigation, hypo sludge was used as a partial replacement in varied proportions (5, 10, 15, 20, 25, and 30%) of cement in concrete of M30 grade to be assessed. Styrene–butadiene rubber (SBR) latex and basalt fibre (BF) were added to hypo sludge concrete to improve its durability and post-cracking behaviour. From the test results, the optimum dosage of hypo sludge, basalt fibre, and SBR latex was found to be 15%, 0.3%, and 10%, respectively. From the mechanical properties testing compared with the control concrete, latex-added hypo sludge basalt fibre showed an increase in compressive strength by 17.08%, flexural strength by 14.55% and tensile strength by 14.29%. Microstructural results showed that SBR latex created greater consistency in the interaction of the concrete stages. Results of the tests indicate that the performance of the concrete in terms of its strength was improved by partially replacing the cement in the concrete with hypo sludge.

Preparation and performance optimization of eco-friendly geopolymers prepared from coarser lignite-based waste fly ash

Fly ash (FA) is generated in massive quantities by burning coal in power plants. The quality of the FA depends on the origin and type of coal. In developing countries, FA produced is relatively low quality and coarser. It does not meet the criteria to be used as a construction material and requires modifications. The waste lignite-based FA generated from a power plant was used in this investigation to produce geopolymer. The raw FA-based geopolymer was tested for normal consistency, initial setting time, fluidity, and compressive strength at different molarities of sodium hydroxide (SH, 8 to 14 M). The effect of different sodium silicate to NaOH (S/N) ratios (1 to 2.5) on the properties of geopolymer was also determined. However, maximum compressive strength of 14.1 MPa was achieved using S/N ratio of 2.5 and 12 M SH solution. Then different techniques were applied to increase the compressive strength of geopolymer, including high-temperature treatment, adding polymers and chemical admixtures. Heat curing the plain geopolymers in an oven at elevated temperatures, from 60 to 80 °C at 10 °C intervals for 2 h, yielded better compressive strengths. At 80 °C, the samples achieved a 71.2% increase in strength. Superplasticizers, i.e., polynaphthalene sulfonate and polycarboxylate ether-based, remained slightly effective for geopolymers. It was also corroborated that styrene-butadiene rubber latex (SBR) latex and polyvinyl alcohol (PVA) enhance fluidity and compressive strength of geopolymer. SBR and PVA can be used as superplasticizers and strength enhancers in geopolymer. Samples with SBR and PVA as polymeric admixtures provided 72.7% and 72.8% higher compressive strength than the control sample. Furthermore, grinding FA by ball and disc milling increased the fineness of FA. The ground FA also provided a 71.3% increase in compressive strength as compared sieved control geopolymer. This study provides a new approach for the high-value utilization of coarser lignite-based waste FA, and develops a new strategy for the performance improvement of low-quality FA-based geopolymers.

Effect of competitive adsorption between specialty admixtures and superplasticizer on structural build-up and hardened property of mortar phase of ultra-high-performance concrete

This study aims to enhance structural build-up of ultra-high-performance concrete (UHPC) without influencing the initial flowability, which is critical in repair applications (e.g., use of UHPC in thin bonded overlays for bridge deck rehabilitation). Specialty admixtures, such as a viscosity-modifying admixture (VMA), have been used to enhance the structural build-up at rest. However, the use of specialty admixtures can increase superplasticizer (SP) demand to maintain proper flowability; the synergistic effect of these admixtures on structural build-up is not well understood as the coupled admixture content can reverse the net effect on yield stress, viscosity, and thixotropy. In this study, VMAs including welan gum (WG), diutan gum (DG), and cellulose ether (CE) were used. Styrene-butadiene rubber (SBR) and acrylic ester (AE) latex polymers (LPs) that can enhance structural build-up and bond strength were also incorporated. The competitive adsorption between these specialty admixtures and SP and its effect on structural build-up, early-age hydration, compressive and pull-off strengths, porosity and entrapped air content of UHPC mortar (i.e., without fiber) were systematically investigated. Test results indicated that the incorporation of anionic WG and DG that exhibited high competitive adsorption with SP led to a 275%–450% enhancement in structural build-up despite the 55%–135% increase of SP demand. Such increase was limited to 130% when using CE, SBR, or AE that cannot effectively adsorb onto cement particles in the presence of SP. This was because the high competitive adsorption between specialty admixtures and SP strengthened the particle flocculation and promoted the cement hydration in the first hour; the latter resulted in 20%–40% enhancement in non-reversible component of structural build-up. Furthermore, the use of LP at low and moderate dosages secured high bond strength to normal strength mortar despite 8%–33% decrease in compressive strength given the increased capillary porosity. The use of VMAs increased the entrapped air and resulting 5%–15% lower compressive strength, while the bond strength was not influenced.

Effect of Evaporation Methods on Modified Emulsified Asphalt Residues from Rheological and Chemical Characteristics

Accurately evaluating and characterizing the performance of emulsified asphalt is the basis of its application. The rheological properties of modified emulsified asphalt residues and its material action mechanism were studied. To achieve this goal, styrene butadiene styrene (SBS)- and styrene butadiene rubber (SBR)-modified emulsified asphalt were prepared, and modified emulsified asphalt residues were prepared by the direct heating method (DHM) and two low-temperature evaporation methods (EN13074 and ASTM D7497-09). Then, the rheological properties and fatigue resistance of the modified emulsified asphalt residues were characterized through dynamic shear rheometry tests. Finally, Fourier transform infrared spectroscopy and elemental analysis were conducted to monitor the curing behavior of modified emulsified asphalt residues. The results indicated that the incorporation of SBS and SBR latex into emulsified asphalt significantly improved its viscoelastic properties, high-temperature properties, and fatigue life, and reduced its temperature sensitivity. Under different evaporation conditions, the unmodified emulsified asphalt residues and SBS-modified emulsified asphalt residues obtained by the ASTM D7497-09 evaporation method had the best rutting resistance and recovery percentage, followed by the emulsified asphalt residues obtained by EN13074 and DHM. However, the rutting resistance of SBR-modified emulsified asphalt residues was not greatly affected by the evaporation method. Though prepared with different evaporation methods, unmodified emulsified asphalt residues had similar fatigue life, and the fatigue life of modified emulsified asphalt residues were ranked as Nf (ASTM D7497-09) >Nf (EN13074) >Nf (DHM). The emulsified asphalt residues obtained by DHM and EN13074 still contain moisture, and it is recommended to use the ASTM D7497-09 evaporation method to obtain emulsified asphalt residues for performance evaluation.