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As the most widely used building material, cement has attracted the attention of scholars because of its large carbon emission. To alleviate the problems of carbon emission and limited resource use caused by cement production, this study focuses on the performance of mortar after carbonization curing by regulating the composition of ternary binders. Testing involved mechanical parameters, carbon shrinkage, water absorption, hydration product, microstructure, adsorption of carbon dioxide, calcium carbonate content, and carbonization degree of mortar, as well as comparisons with the effect of calcium carbide slag and sintered red mud. We carried out several studies which demonstrated that carbonization curing and adjusting the content of calcium carbide slag and sintered red mud were beneficial to improve the mechanical properties, peak load displacement, slope, elastic energy, plastic energy, carbon shrinkage, carbon dioxide adsorption, calcium carbonate content, and carbonization degree of mortar, while the addition of calcium carbide slag and sintered red mud increased the water absorption of mortar, and the greater the dosage, the greater the water absorption. Meanwhile, adding 25%–50% calcium carbide slag and sintered red mud still had negative effects on the mechanical properties of mortar. But carbonation curing and the addition of calcium carbide slag and sintered red mud could promote the hydration reaction and consume calcium hydroxide formed by hydration to form calcium carbonate. When the dosage was 50%, the carbon dioxide adsorption capacity, calcium carbonate content, and carbonization degree of calcium carbide slag mortar were higher than those of sintered red mud mortar, which increased by 29.56%, 102.73%, and 28.84%, respectively. By comparison, calcium carbide slag and sintered red mud still showed superior carbon sequestration capacity, which was higher than fly ash and Bayer red mud. From the experiment, we came to realize that adjusting the composition of cementitious materials could realize the carbon sequestration of cement-based materials and promote the road toward low-carbon sustainable development of cement. [ABSTRACT FROM AUTHOR]

It discusses the influence of fly ash, vitrified beads and fine sand of aerated concrete as aggregate, straw leaf fiber, straw rod fiber, bamboo fiber and polypropylene fiber as fiber on the performance of aerated concrete with manganese slag. The experimental results show that: The replacement of silica sand with fly ash, vitrified beads and aerated concrete fine sand can not only reduce the dry density of aerated concrete with manganese slag, but also greatly reduce its compressive strength. With the addition of straw leaf fiber, straw rod fiber, bamboo fiber and polypropylene fiber, dry density of aerated concrete with manganese slag decreased by 1.8%~16%, compressive strength increased by 9%~44%, tensile strength increased by 2%~38%, and water absorption increased by 0.79%~13.3%. [ABSTRACT FROM AUTHOR]

The influences of aerating agent content, glass fiber content, activator content, foam stabilizing agent content, water reducing agent content, fly ash content and water-to-binder ratio on the properties of sedimentary fly ash aerated concrete are studied. The higher flexural strength is the principle of the preferred mixing ratio when complying with the compressive strength and dry density specified in the code GB 11968--2006 "Autoclaved aerated concrete block". The results show that the optimal mixing ratio is cement 50%, fly ash 50%, dosage of the aerating agent, glass fiber, activator, foam stabilizing agent and water reducing agent is 0.7%, 0.3%, 0.9%, 0.2% and 1.1% of total mass of cement and fly ash, and water-to-binder ratio is 0.23. [ABSTRACT FROM AUTHOR]

Concrete structure is usually affected by sulfate and magnesium salt in soil water environmental. In order to explore anti-erosion properties of cement concrete and high-performance concrete mixed with slag powder after immersed in solution with sulfate and magnesium salt, the study designed three water-binder ratio treatments and two slag powder content treatments. After mixing with water, 1050 specimens (10 mm×10 mm×60 mm) were prepared and incubated in conditions of 20°C and moisture≥9.5% for 28 d. Then, they were immersed in five different solutions with different sulfate and magnesium concentrations for determine anti-erosion coefficient and microstructure of the specimens during erosion. The results showed that: The cement had many pores with large pore size when water-binder ratio was 0.50, and the maximum diameter of pore reached 372.5 μm. The improvement of the pore structure was not obvious when the water-binder ratio decreased to 0.35. When the pure cement concrete specimens was immersed in solution with 2500 mg/L SO42- and 1400 mg/L magnesium2- for 4 months. The pores of specimens were full of hydration products such as CaSO4·2H2O, 3CaO·Al2O3·3CaSO4·32H2O (AFt), and a small amount of Mg(OH)2 and MgO·SiO2·H2O, which could lead to cracks in concrete, peeling off the side parts, even being crisp and surface slurry loss seriously. After 2 months, the erosion coefficient showed a downward trend with erosion duration and was below 0.85, indicating a limited anti-erosion capacity of silicon concrete. When the concrete was added with slag powder, the pore numbers became small and pore size was small. The largest pore size of concrete with water-binder ratio of 0.35 and 0.30 was only 1/7 and 1/8 times as that of concrete with water-binder ratio of 0.50. Meanwhile, the content of Ca(OH)2 was reduced. The concrete structure became loose, which was more obvious for specimens with low water-binder ratio. After 12 months of erosion in solution of sulfate and magnesium salt (20250mg/L SO42- and 2800mg/L Mg2+), the edge of specimen did not have erosion products and crystals of MgSO4·7H2O, Na2SO4·10H2O, Mg2(OH)3Cl·H2O, and the corrosion resistance coefficient was still more than 0.85. It suggested that slag powder can significantly improve the anti-erosion properties of high performance concrete formulated by 32.5 silicate cement. Therefore, when cements were used for environment with solutions including 13000 mg/L SO42- and 1400 mg/L Mg2+, or 20250 mg/L SO42- and 2800 mg/L Mg2+, the water-binder ratio of concrete should not be greater than 0.35 and 0.30, respectively, while slag powder content was appropriate from 40% to 45%.The study could provide data support and theoretical basis for concrete preparation and application in irrigation engineering (dam foundation, gates infrastructure and channels etc.) and greenhouse concrete foundation engineering. [ABSTRACT FROM AUTHOR]

In order to evaluate long-term seepage stability and service life of plastic concrete that are made of bentonite, clay, cement, soil aggregate, water, superplasticizer, etc., we studied incomplete or contain holes of plastic concrete's long-term seepage stability and service life. Specimens of plastic concrete were molded after many times of tests, and their compressive strength of 28 days was 1.25 MPa, and meet requirements impermeability grade was S1 which was test code for hydraulic concrete because water pressure measured was 0.2 MPa by step by step method. The preparation of plastic concrete permeability test required to a round-shaped specimen (top diameter is 175 mm, basal diameter is 185 mm, height is 150 mm). Type I was complete specimens of concrete impermeability; and Type II specimens were high in the direction parallel to the reserved five through holes with a diameter of 3.5 mm, plum-shaped layout was on the plane. It was found after long-term corrosion test plastic concrete can produce shear cracks and tensile cracks and even had lager plastic deformation after long-term seepage dissolution by pure water, which led to damage of the plastic concrete. This resulted in an increase of maximum displacement values of top surface of the specimen by 38.5 mm on average. The permeability coefficient was changed in the early (30 to 40 days) penetration test, but they were in 10-7 cm/s orders of magnitude. The permeability coefficient was increased to 3.0×10-7 cm/s and then tended to be stable during 150-180 days. Ca2+ were dissolved from the concrete and leached out after long-term seepage dissolution, the amount of Ca2+ removed from concrete specimens were linearly decreasing as dissolution time (<150 days). The concentration of Ca2+ in the specimen water seepage fell below 110 mg/L after 180 days of dissolution. Through dissolution experiment, calculating plastic concrete's coefficient of permeability and content of CaO were done based on the formula of diaphragm wall's durable years, the calculated service life was 37.1-60.7 years. Drench experiment showed that flows may create preferential erosion in holes in concrete, and Ca(OH)2 in concrete were dissolved and carried away by the flow which led to decrease in weight of plastic concrete. The flow of constant pressure through holes of concrete was relatively weak, and few Ca in concrete were dissolved and carried away. Even after drench 197 d, there was less quality loss compare with the original, the relative loss was not more than 1%. However the concrete strength loss was larger (up to 25.4%). The white precipitates in the hole were CaCO3, and some Na+, trace clay and bentonite particles after laboratory analysis. The studies showed that the features of plastic concrete made of clay and bentonite had a low-intensity, high impermeability and long service life which met the requirement of impervious wall of earth-rock fill dam. Thus, it can be used for embankment dam for seepage prevention. [ABSTRACT FROM AUTHOR]