Construction robots are considered to be an useful measure for changing construction industry from labor intensive industry to knowledge intensive one. Although sudden public attention of construction robots is gone, we believe practical use of construction robots is just started now. This paper reports on the state-of-the-art of construction robots in concrete work which is the most basic element of construction work.

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The life prediction of reinforced concrete structure is one of very useful technique to estimate durability of the structure. It needs quantitative evaluation of deterioration which progresses with the passing of the years and of the influences of various factors on deterioration. Herein, the life prediction method of reinforced concrete member is introduced based on the reinforcement corrosion due to action of chloride. The life of reinforced concrete member can be defined as the span that the structure needs to be a certain limit state from its construction. Two evaluation models, that is, physical model for reinforcement corrosion in concrete and reliability-based model for reduction of member resistance are conducted concerning two limit state, that is, cracking longitudinally due to reinforcement corrosion and the ultimate limit state for flexural resistance of member, respectively. These models enable us to predict the life of reinforced concrete member.

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Few prestressed concrete pavements having the length beyond 100 m have been constructed in order to avoid the development of cracking at early ages as well as to get design prestress. If the prestressed concrete slab is paved as long as possible, both shortening period and lower cost for construction can be accomplished. This paper reports the results of investigation carried out to prevent from crack development at early ages mainly due to hydration heat of cement as well as to keep the design value of prestress in the prestressed concrete pavement with length of 151 m constructed at New Tokyo International Airport. The following results are obtained from this investigation. (1) According to numerical examinations before the start of construction, there is high possibility of crack development at early ages when the usual curing is adopted. The prevention from crack occurrence can be, however, performed by careful curing for controlling the concrete temperature. (2) The thermal cracking was not observed in concrete slab, because the curing adopted based on the numerical examinations succeeded to control the immediate drop of concrete temperature from peak value. (3) The first pretensioning, which vanishes friction between base and concrete slab, is effective to prevent the development of cracking. (4) The degree of restraint become large toward the center of concrete slab. Once concrete slab is prestressed, the degree of restraint in concrete slab becomes small gradually by the repeating expansion and contraction of concrete slab due to temperature change. As the degrees of restraint just after the second pretensioning as well as main prestressing increase again up to the noticeable values, the design value of prestress must be obtained for a several days just after prestressing, which suggests that traffic just after main prestressing results in the damage of the pavement. (5) The design prestress is successfully given to concrete slab having the long length of 150 m without development of cracking by improving the curing method.

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The 41-story appartment building nicknamed “MKO” in Sakuranomiya-River-City will be the highest structure in Japan. This building with Tube-in-Tube system as a most efficient struct ural system is under construction using OHRC-21 (OBAYASHI Hirise Reinforced Concrete for 21st Century) Procedure and characterized by : (1) steel-plate external reinforcement to confine concrete for first story's columns subject to highaxial load, (2) “diagonally reinforced concrete beam to increase shear resistance, (3) high strength concrete of 420 kgf/cm2. In this paper, outline of the building and special concrete work and quality control for 420 kgf/cm2 high strength concrete are reported.

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