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Brittle fracture is a typical mechanical characteristic of high-strength self-compacting concrete, and the research on its toughening modification remains the highlight in the engineering field. To understand the effect of toughening materials (including polymer latex powders, rubber particles, and polyethylene fibers) on the mechanical behavior of C80 high-strength self-compacting concrete under static loading, the failure mode, mechanical strength, strain field, and crack opening displacement (COD) of prepared high-strength self-compacting concrete under compressive, splitting, and flexural loads were studied based on digital image technology (DIC). The corresponding mechanism is also discussed. The results show that the hybrid of polymer latex powders, rubber particles, and polyethylene fibers can increase the crack path and inhibit the development of macrocracks in concrete, thus turning the fracture behavior of concrete from brittle to ductile. The addition of toughening materials reduced the compressive and flexural strengths of high-strength self-compacting concrete, but it increased the splitting strength. DIC showed that the incorporation of toughening materials promoted the redistribution of strain and reduced the degree of strain concentration in high-strength self-compacting concrete. The evolution of COD in high-strength self-compacting concrete can be divided into two stages, including the linear growth stage and the plastic yield stage. The linear growth stage can be extended by incorporating toughening materials. The COD and energy absorption capacity of concrete were enhanced with the addition of toughening materials, and the best enhancement was observed with the hybrid of polymer latex powders, rubber particles, and polyethylene fibers. Overall, this research provides a reference for exploring effective technical measures to improve the toughness of high-strength self-compacting concrete.

In order to solve the problems of the sudden loss of fluidity and low expansion rate of CAM I (cement asphalt mortar type I) in a construction site with high environmental temperature, this paper studies the effect of temperature on the fluidity, expansion ratio and pH value of CAM I. The mechanism of action was analyzed by IR (infrared spectrometry), SEM (scanning electron microscopy) and other test methods. The results showed that a high temperature accelerates aluminate formation in cement paste. Aluminate adsorbs emulsifiers leading to demulsification of emulsified asphalt, and wrapped on the surface of cement particles, this causes CAM I to lose its fluidity rapidly. The aluminum powder gasification reaction is inhibited, resulting in an abnormal change in the expansion ratio. Based on findings, the application of an appropriate amount of superplasticizers can effectively improve the workability and expansion characteristics of CAM I at a high temperature.

Effective foundation reinforcement treatment is essential for modern large and complex infrastructure, while it is significant for developing new green high-performance materials for foundation reinforcement. This study investigates a new green concrete by using high volume fly-ash and coal gangue aggregates, which is expected to apply for foundation treatment of modern infrastructure with high loading-bear ability. In this experiment, 12 mix proportions of fly ash coal gangue mixture (the material name, abbreviated FGM) were designed, and its mechanical properties and durability performance were investigated. The mechanical properties of FGM include compressive strength, dynamic elastic modulus, dynamic shear modulus, Poisson&rsquo, s ratio, and the stress&ndash, strain behaviors. The durability performance was evaluated by the parameters of acid resistance, which simulated an acid circumstance. After that, the environmental effects about carbon emission of this material were also investigated. Results show that the FGM with 84.6% wastes utilizing rate is a cost-effective material for foundation reinforcing treatment. Its compressive strength at 28 days and 60 days can reach more than 8 MPa and 10 MPa, respectively. After being immersed in the acid environment for 140 days, the mass loss (%) of the material could be under 3.5%. The greenness shows that the e-CO2 indices of FGM are lower than 20 kg/MPa&middot, m3, and the e-energy indices are at below 150 MJ/MPa&middot, m3. FGM has the advantages of acid resistance, waste recycling, and lower carbon emissions than the previous methods for foundation improvement.

Rheological curves of cement&ndash, fly ash (C&ndash, FA) paste incorporating nanomaterials including nano-SiO2 (NS), nano-CaCO3 (NC) and nano-Al2O3 (NA) at different resting times (hydration time of 5 min, 60 min, and 120 min) were tested with a rheometer. The rheological behaviors were described by the Herschel&ndash, Bulkley (H&ndash, B) model, and the influences of these nanomaterials on rheological properties of C&ndash, FA paste were compared. Results show that the types, content of nanomaterials and resting time have great influences on the rheological properties of C&ndash, FA paste. Incorporating NS and NA increases yield stress and plastic viscosity, and decreases the rheological index of C&ndash, FA paste. When the content of NS and NA were 2 wt%, the rheological index of C&ndash, FA paste was less than 1, indicating rheological behavior changes from shear thickening to shear thinning. Meanwhile, with rising resting time, yield stress and plastic viscosity increased significantly, but the rheological index decreased evidently, showing paste takes on shear thinning due to the rise of resting time. However, incorporating 3 wt% NC and the rising of resting time did not change the rheological properties of C&ndash, FA paste. These differences are mainly that the specific surface area (SSA) of NS (150 m2/g) and NA (120 m2/g) are much larger than that of NC (40 m2/g). The huge SSA of NS and NA consume lots of free water and these tiny particles accelerate the hydration process during resting time.