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The introduction of superabsorbent polymers into cement increases the number of macroscopic pores, resulting in reduction of compressive strength. These limitations can be addressed by incorporated nano silica in polymer structure. Herein, a series of composite microgels containing nano silica were prepared and incorporated into cement paste. The effect of composite microgels on the hydration degree, compressive strength of cement paste was investigated. The microstructure and affected zone of cement paste were characterized by nitrogen adsorption desorption (NAD), backscattering (BSE), thermogravimetry (TGA) and microhardness techniques. The equilibrium absorptivity and water release rate of the composite microgels can be improved by proper crosslinking density and silica content. The addition of low crosslinking density composite microgels accelerated the formation of hydration products, which encouraged to filling formed voids. More dense arch structure was observed in vicinity of formed void. These further suggested that the reduction in the compressive strength of cement paste can be offset by composite microgels with proper crosslinking density, thus providing important application prospects in internal curing. [ABSTRACT FROM AUTHOR]

For the preventive maintenance engineering of special pavements such as ultra-thin friction courses and bridge deck pavements, the performance requirements of the utilized high-viscosity asphalt, including the resistance to permanent deformation, cracking ability, durability, and recyclability, are becoming increasingly stringent. In this study, based on the click reaction principle of carbon-carbon double (C C) bond, hydroxyl-terminated polybutadiene (HTPB) and isophorone diisocyanate (IPDI) were selected as the raw materials to synthesize thermoplastic polyurethane (TPU), and then 4,4'-disulfanediyldiphenol (DSDDP) was introduced as the chain extender to design a high-viscosity thermoplastic polyurethane modified asphalt (PUA). Subsequently, the mechanical and rheological properties of PUA under different types of chain extenders and polyurethane (PU) contents were tested, and the microstructure and modification mechanism were investigated at multiple scales. The results indicated that after the introduction of DSDDP, the basic physical properties and viscosity of PUA were greatly enhanced, the fluidity was significantly reduced, and excellent deformation and cracking resistance were achieved at various temperatures. The microscopic tests revealed that the viscosity enhancement effect mainly originated from the click reaction between the disulfide (S-S) bonds in DSDDP and the C C bonds on the soft segments of PU, which can further crosslink the linear PU molecular chain and form a dense spatial network structure to restrict the flow of macromolecules. The dynamic exchange of some S-S bonds facilitates the repetitive opening of the PUA network structure at high temperatures, so the PUA still exhibits thermoplasticity at high temperatures, which verifies the feasibility of the proposed design. Moreover, the addition of DSDDP reduced the degree of microphase separation of PUA, so the designed PUA can effectively adapt to various temperature environments. Overall, the findings of this study can boost the application of this novel PUA in the thin surface layers of high-performance pavements. [Display omitted] • The click reaction principle is applied to polyurethane modified asphalt (PUA) system. • Formed carbon-sulfur bonds provide PUA with high viscosity and excellent mechanical properties. • The PUA has a thermoplastic three-dimensional network structure that is partially reversible. • The designed PUA is a suitable material for high-performance pavement surface thin layer. [ABSTRACT FROM AUTHOR]

[Display omitted] • A CR/polyurethane modified asphalt sealant was prepared by the in-situ polymerization method. • The high and low temperature rheological properties of sealant were all excellent. • The PU phase was uniformly dispersed in asphalt quantified by fluorescence images. • The sealant has achieved great effects in the treatment of pavement cracks on site. Under the long-term effect of loads and climate conditions, various diseases can appear on the surface of asphalt pavement, causing deterioration in its performance. To address the pavement surface cracks during service, the present study developed a crumb rubber/polyurethane (CR/PU) compound as the modified asphalt sealant with excellent properties. The optimal material proportion, ensuring the best asphalt compatibility was selected to meet the requirements of standard hot-poured sealants for pavement. Additionally, the fineness and content of CR were determined. The research investigated rheological properties, aging performance, microstructure, and modification mechanism of the CR/PU sealant was then applied in an engineering project to evaluate its effectiveness in treating pavement cracks, and suitable construction techniques were summarized. The results revealed that the in-situ polymerization method is an appropriate approach for preparing the CR/PU sealant, demonstrating good high-temperature deformation resistance and low-temperature crack resistance, indicating synergistic interactions between CR and PU. Among various compositions, the sealant with 30 %PU and 15 %CR content exhibited the best thermal oxygen and UV aging properties. Microscopic tests indicated that CR was physically blended with asphalt, while PU underwent chemical modification and formed a cross-linked network structure with asphalt, resulting in CR dispersion around it, enhancing the thermal stability of the system. Furthermore, the test section displayed an ideal crack treatment effect, demonstrating the sealant's excellent sealing, durability, and watertight capacity. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel kind of microgel has been synthesized by inverse suspension polymerization. • The microgel showed a desired absorption and water retention in cement filtrate. • The drying shrinkage and compressive strength of modified mortar were improved. In this paper, three kinds of P(AM- co -MAA) microgels with different anion contents were synthesized by inverse suspension polymerization with acrylamide (AM) and methacrylic acid (MAA). The modified mortar was prepared by cement and sand as fillers and P(AM- co -MAA) as internal curing agent. The swelling behavior of P(AM- co -MAA) microgels with different anion contents in aqueous solutions was studied. The effects of P(AM- co -MAA) and commercial superabsorbent polymer (SAP) on the flowability, mechanical properties, drying shrinkage and microstructure of mortar were investigated. The results showed that the presence of multivalent cations (mainly Ca2+) weakened the absorption capacity of microgels in cement filtrate. Spherical microgels had no negative effects on the flowability and mechanical properties of cementitious materials. The compressive strength of modified mortar can be significantly improved at later curing stage due to dome structure and internal curing. Furthermore, the water content of modified mortar with 0.1% additions of microgel decreased, and the drying shrinkage rate of the modified mortar was about 36% lower than that of cement mortar without microgels. It can also be observed that a large amount of macro pores were not formed around the microgels. [ABSTRACT FROM AUTHOR]