奥村組技術研究年報 No.49 2023 年 9 月■土木系■（材料）

Analytical and Experimental Study on Estimating the Compressive
Strength of Early Age Concrete by the Maturity Method
Biswas Rajib Kumar＊ Takahiro Saito＊ Ryutaro Matsumoto＊

OBJECTIVESIn order to expedite the construction process, it might be essential to estimate the early age (less than 1 day) strength of concrete subjected
to various temperatures and curing methods for the construction of mountain tunnels. However, the relationship between various curing
temperatures and the strength development of concrete at a very early stage is not completely understood, and the current approaches might
not be able to predict the compressive strength of concrete at an early age. The objective of this study is to establish a relationship between
early age compressive strength of concrete and concrete maturity considering varied temperature histories of concrete. Both numerical andexperimental study has been carried out in this study.

OVERVIEW
Estimation of strength of concrete (in situ) at an early age canbe critical for many reasons such as removal of the formwork,
post-tensioning, handling precast members, etc. In this study,
the maturity function of concrete at early age (less than 1 day)was established using different water cement ratio (W/C ) andvarious temparature historis for concrete curing. For,
W/C=0.5, the number of experimental cases were 10, whereinitial concrete temperature ranged between 10 to 30°C and thecuring temperature ranged between 10 to 50°C. The concrete
maturity function obtained from the experimental study(W/C=0.5) can be seen in Figure 1. To predict the structural
behaviour of concrete subjected to different W/C ratio andcuring condition, numerical analysis was carried out in thesoftware package LINK 3D. The software can incorporate themodelling of microscopic behavior of concrete, such as theFigure 1: Concrete maturity function for W/C=0.5
progress of cement hydration reaction, the formation of void
structures in hardened bodies, internal moisture state, and the macroscopic view of reinforced concrete. It can be seen from Figure 2 and3 that there is an excellent correlation between the experimental study and FEM analysis. FEM analysis could predict the strength gain of
the concrete specimens with high precision. The numerical study slightly underestimated the experimental data. However, the numericallyobtained data can be considered safe in the case of field construction.

RESULTS

Figure 2: Comparison of experimental and numericalFigure 3: Comparison of experimental and numericalresults for W/C = 0.5

results for W/C = 0.4

From the experimental and numerical analysis, the relationship between compressive strength and concrete maturity at an early age (lessthan 1 day) was established. It was understood that for W/C=0.5, concrete can gain compressive strength of 2 MPa within 16 hours, when
it is subjected to a curing temperature of 20°C or more and an initial temperature of 15°C or more. For W/C=0.4, concrete can gain
compressive strength of 2 MPa within 12 hours, when it is subjected to curing temperature of 20°C or more and initial temperature of 20°Cor more. Datum temperature may change depending on the concrete mix property. Appropriate datum temperature should be evaluated forimprovement of the maturity method.
＊

技術本部技術研究所土木研究グループ-4-4-