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The independently designed and manufactured ultra-high-strength aluminum alloy Al-12.18Zn-3.31Mg-1.43Cu-0.20Zr-0.04Sr was investigated via scanning electron microscopy observations, X-ray diffraction analysis, hardness tests, electrical conductivity tests, tensile tests, intergranular corrosion tests, and exfoliation corrosion tests. The effect of pre-recovery on the microstructure and mechanical properties of this aluminum alloy was also studied. The results show that the pre-recovery heat treatment releases deformation energy, inhibits recrystallization, and decreases the dislocation density. Although the pre-recovery heat treatment has little effect on the hardness, electrical conductivity, and elongation of this aluminum alloy, it can dramatically improve the alloy’s tensile strength (the maximum tensile strength increased from 785.0 MPa to 809.2 MPa). Moreover, the tensile properties of this aluminum alloy have a certain degree of isotropy, and the pre-recovery heat treatment does not affect this property. In addition, the rolled aluminum alloy exhibits good corrosion resistance, but the effect of the pre-recovery heat treatment on the alloy’s resistance to intergranular and exfoliation corrosion is negligible.

The microstructure and mechanical properties of independently designed and manufactured Al-12.51Zn-2.85Mg-2.83Cu-0.18Zr-0.06Sr high strength aluminum alloy was investigated and the effect of pre-recovery on the alloy's performance was also studied. The results show that pre-recovery heat treatment has little effect on the alloy's crystal orientation, but it can consume deformation energy, reduce recrystallization driving force, inhibit recrystallization and decrease dislocation density ( the dislocation density decreased from 0.501 to 0.320×1014m-2). Moreover, pre-recovery heat treatment can dramatically increase the electrical conductivity of this alloy (the maximum electrical conductivity increased from 28.55% IACS to 34.01% IACS), however, the hardness all decreased after pre-recovery treatment, but the drop is very small. In addition, pre-recovery heat treatment can significantly improve the alloy's resistance to intergranular corrosion (the minimum intergranular corrosion depth decreased from 62.67?m to 47.43?m), however, the effect of pre-recovery heat treatment on the alloy's resistance to exfoliation corrosion is negligible.

Ultra-high-strength grade self-compacting concrete used for steel-tube confined concrete bridge pier structure was designed and prepared. To enhance the performance of the hardened concrete and the cohesiveness of the fresh concrete, fly ash and silica fume combined with polycarboxylic super-plasticiser were used. The mechanical properties and workability of the concrete were investigated in experiments. With the selected mixture from the experimental mixture series, the ultra-high-strength grade concrete was produced at industrial scale and used in bridge pier structures. Self-compacting concrete was cast into the steel tube by the high-drop method. The experiment results and the practical application show that ultra-high-strength self-compacting concrete with excellent performance can be produced with common raw materials.

The permeability of lightweight aggregate concrete was studied. Some efforts were taken to increase the resistance of lightweight aggregate concrete (LC) to water penetration by using the mineral admixtures of fly ash, granulated blast furnace slag or silica fume. Accelerated chloride penetrability test and liquid atmosphere press method were used to study the anti-permeability of lightweight aggregate concrete. The experimental results show that fly ash, granulated blast furnace slag and silica fune can decrease the permeability of lightweight aggregate concrete, but the effect of granulated blast furnace slag is poor. According to the SEM and pore structure analyzing results, an interface self-reinforcing effect model was presented and the reinforced mechanism of mineral mixture on LC was discussed according to the model described by authors.

The influence of polymer addition on microstructure, performance and mechanical properties of lightweight aggregate concrete was investigated. It was found that the addition of polymer improved the performance and mechanical properties of lightweight aggregate concrete. It was ascertained that the modification of microstructural uniformity and densification with the addition of polymer is responsible for the enhancement of mechanical properties. With respect to compressive strength and bending strength, the lightweight aggregate concrete added with 13% ethylene-acetate ethylene interpolymer (EVA) exhibits preferred mechanical properties.

The hydration process, hydration product and hydration heat of blended cement paste mixed with mineral admixture and expansive agent at low W/B ratio are studied by XRD, thermo analysis, and calorimetry instrument, and they were compared with those of pure cement paste. The results show that pure cement and blended cement at low W/B ratio have the same types of hydration products, but their respective amounts of hydration products of various blended cements at same ages and the variation law of the amount of same hydration products with ages are different; The joint effect of tumefaction of gel-ettringite due to water absorption and the expansive pressure on the pore and rift caused by the crystalloid ettringite is the impetus of the volume expansion of cement paste, and the former effect is much greater than the latter one.

The hydration characteristics and expansion impetus of three kinds of cement paste under free-and confined-curing conditions were investigated, which were respectively mixed with three different kinds of expansive agent at low W/B ratio. The results show that the hydration products of pure cement paste and paste mixed with expansive agent are same, but the amount of hydration products, un-hydrated C3S and C2S are obviously different at the same hydration age. At 3 d age, the amount of CH in pure cement paste is less than that of paste mixed with expansive agent, but it is reverse when at 28 d age. The amount of AFt at 3d and 28d age in pure cement paste is less than those of paste mixed with expansive agent. Regardless of under free- or confined-curing condition, the amount of ettringite produced varies little since 3d age. The joint effect of the tumefaction of gel-ettringite due to water absorption and the expansive pressure on the pore caused by the crystalloid ettringite is the cause of the volume expansion of cement paste, and the former effect is much greater than the latter.

The effects of mineral admixtures on fluidity, mechanical and hydrational exothermic behavior were studied. The results show that, double-adding ways, i e, fly ash and slag were added at the same time, not only improves the fluidity of fresh concrete with low W/B and compensates the lower early compressive strength of harden concrete caused by high adding amount of fly ash, but also greatly reduces the highest temperature rise, exothermic rate and total heat liberation of 3 day of binder pastes in HLPC, and postponed the arrival time of the highest temperature rise. HLPC was prepared and applied to project practice successfully.

A kind of high impermeable and crack-resistance chemical admixture (HICRCA) was prepared, which is a compound chemical admixture composed of an expansion ingredient, density ingredient, and organic hydrophobic poreblocking ingredient. The results of the experiments indicate that the addition of HICRCA improves mortar and concrete in the following performances: (1) perfect workability: slump is more than 22cm, the slump after 3h is about 16cm; (2) high impermeability: for the mortor, the pervious height under a water pressure of 1.5 MPa is 1.5cm, for the concrete, the pervious height under a water pressure of 5.0 MPa is 2.2cm; (3) high crack-resistance: there is a micro-expansion at the age of 90d; (4) high compressivestrength: compared with the controlled concrete, the compressive strengths at the age of 3d and 28d are improved by 66.4% and 62. 0%, respectively. At the same time, the effects of different curing condition on mortar and concrete expansive and shrinkage performance were studied. In addition, the impermeable and crack-resistance mechanism was investigated in the present paper.

Hydration heat evolution, non-evaporative water, setting time and SEM tests were performed to investigate the effect of fine steel slag powder on the hydration process of Portland cement and its mechanism. The results show that the effect of fine steel slag powder on the hydration process of Portland cement is closely related to its chemical composition, mineral phases, fineness, etc. Fine steel slag powder retards the hydration of portland cement at early age. The major reason for this phenomenon is the relative high content of MgO, MnO2, P2 O5 in steel slag, and MgO solid solved in C3 S contained in steel slag.

The characteristic of autogenous shrinkage (AS) and its effect on high strength lightweight aggregate concrete (HSIAC) were studied. The experimental results show that the main shrinkage of high strength concrete is AS and the amount of cement can affect the AS of HSLAC remarkably. At the early stage the AS of HSIAC is lower than that of high strength normal concrete, but it has a large growth at the later stage. The AS of high strength normal concrete becomes stable at 90 d age, but HSIAC still has a high AS growth. It is found that adjusting the volume rate of lightweight aggregate, mixing with a proper dosage of fly ash and raising the water saturation degree of lightweight aggregate can markedly reduce the AS rate of HSIAC.

A new-type underwater non-dispersible concrete admixture NDA was prepared, its function mechanism was analyzed, and C40 high performance non-dispersible underwater concrete was manufactured by applying NDA. The results indicate that NDA has a suitable workability, low strength loss, and excellent anti-dispersion; the fresh non-dispersible underwater concrete with NDA has high anti-dispersion, excellent workability such as self-compacting and not bleeding; hardened non-dispersible underwater concrete with NDA has a high strength, high durability such as high anti — abrasion, impermeability and anticorrosion.

By means of “Mortar Bar Method”, the ratio of cement to aggregate was kept as a constant 1∶2,25 the water-cement ratio of the mixture was 0.40, and six prism specimens were prepared for each batch of mixing proportions with dimensions of 10×10×60mm3 at 38±2°C and RH≧95%, the influences of content and particle size of active aggregate, sort and content of alkali component and type of slag on the expansion ratios of alkali-activated slag cement (ASC) mortars due to alkali aggregate reaction (AAR) were studied. According to atomic absorption spectrometry, the amount of free alkali was measured in ASC mortars at 90d. The results show above factors affect AAR remarkably, but no dangerous AAR will occur in ASC system when the amount of active aggregate is below 15% and the mass fraction of alkali is not more than 5% (Na2O). Alkali participated in reaction as an independent component, and some hydrates containing alkali cations were produced, free alkalis in ASC system can be reduced enormously. Moreover, slag is an effective inhibitor, the possibility of generating dangerous AAR in ASC system is much lower at same conditions than that in ordinary Portland cement system.