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This research indicates that the gradient of internal relative humidity (IRH) decreases rapidly within 1-day curing age in HPC. The amount of water imported by pre-wetted light-weight aggregate can regulate IRH of concrete. By importing a proper amount of water, the process of the decline of IRH can be delayed and the autogenous shrinkage can be reduced. The relationship among the amount of water imported by pre-wetted lightweight aggregate, IRH and AS was established. The result provides a new method of reducing early AS and enhancing early cracking resistance of HPC.

Using the laser granularity survey technology, X-ray powder diffraction, scanning electron microscopy (SEM) and infrared spectrum analysis methods, we studied the microscopic structure and chemical bonds changes of β-C2 S monomineral under the high energy ball grinding function. The result indicates that, continuously under the mechanical power, β-C2 S crystal size would decrease, the micro strain and the effective Beff parameter would increase, and the amorphous phases would be presented. Furthermore, the mechanical power would cause Si-O bond broken and reorganized, the specific surface area would increase, the energy of micro-powder agglomeration vibration would be enhanced and the crystal would be disordered. Finally, β-C2S was caused to have the mechanochemical change and the activity enhancement.

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 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.

Used as flame retardant of tunnel asphalt pavement, organic bromides produce a large amount of poisons and smoke in construction and flame retardation stage. The alkaline filler was found to replace mineral filler, and the flame-retarded asphalt mixtures were produced. Experimental results show that these asphalt mixtures are smoke restrained; the performances and construction technology of asphalt pavement are not influenced; also the alkaline filler is of low-price. So this kind of flame-retarded asphalt mixtures is suitable for tunnel pavement.

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.