DISSERTATION SUMMARY

Title: “Investigation and Evaluation of some Factors Affecting Operation Quality of Concrete Pavement of Highways and Airport in Vietnam’s Conditions”

Department       : Transport Engineering

Code                   : 9.58.02.05

Candidate’s full name:         Pham Duy Linh

Supervisors:

               1. PhD Vu Duc Sy - University of Transport and Communications

                        2. Prof.PhD Pham Cao Thang - Military Technical Academy

Institution: University of Transport and Communications.

Summary of New Findings of the Dissertation:

1.      The dissertation has analyzed the theoretical grounds, set up the calculation basis for influence of insulating layers on redistribution of internal force among courses, building a calculation software by limited difference method in calculating multi-layer concrete pavement (MLCP). The calculation method allows calculation, investigation and evaluation of influence of thickness and strength of the insulating layer on deflection and redistribution of internal force among courses. The calculation result has ensured reliability, can be used in calculation of 2-course rigid pavement structure with insulating layer of any thickness and any strength.

From the research result for one representative type of pavement structure, in Vietnamese’s conditions, it shows that thickness of the insulating layer has great influence on redistribution of internal force among courses, resulting in increase in bending and tensile stresses of the Concrete Pavement course. Through initial calculation, it is recommended to use insulating layer in multi-layer concrete pavement, it is advisable to choose an insulating layer according to required construction structure to avoid increased stress on the upper course, either below option should be chosen:

+       Material from oil canvas, 1-2 layers.

+       Using bitumen- sand layer of 0.5-0.7cm thickness;

+       Using SAMI of not more than 1.5cm thickness;

            +   When using compacted asphalt concrete of not more than 4cm thickness.

In case of improvement of the existing Concrete Pavement, to level the damaged locations, deflections and concave on the existing pavement, one should avoid to use asphalt concrete material both as insulating layer  and to fill up damaged, which increases thickness of the insulating layer.

2.      The dissertation has built up a temperature calculation software package in concrete pavement (TPCP- Temperature Profile in Concrete Pavement) for calculating temperature profile in concrete pavement of thickness, in different temperature areas, it is only required to state thickness and surface temperature of the pavement in different hours in a day, serving calculation of thermal stress in the Concrete Pavement and calculation of gap of concrete expansion joints in Vietnam’s conditions. The calculation results suggest a retrospective formula in Hanoi city’s climatic conditions and similar areas’:

  Calculation of temperature at the bottom of the concrete pavement and temperature gradient between the surface and bottom of the pavement in Hanoi city and similar areas, to apply in calculate cambered bending stress caused by temperature in the concrete pavement, depending on the pavement thickness:

                                        T_h=-12,3226ln(0,2h+1)+T_bm.

                                         ∆_t=-12,3226.ln(0,2.h+1).

Calculation of average temperature by depth in the concrete pavement, applying calculation of necessity of expansion joint, and calculation of gap of expansion joint of concrete pavement row:

                                                T_tb=-17,8388.ln(0,04 h+1)+T_bm.

3.      The dissertation has presented the bases for calculation of necessity of expansion joint on concrete pavement in Vietnam’s conditions, and the calculation method of appropriate gaps of expansion joints on concrete pavement depending on thickness of the concrete pavement and climatic conditions of each region, and the application to calculate the necessity of expansion joint and gaps of expansion joints for concrete pavement slab row of highways and airports in Hanoi climatic conditions.