The influence of temperature on the cracking of plastic concrete

Abstract

High early age concrete temperatures can lead to many problems such as an increased rate of cement hydration, as well as an increased rate of moisture loss from fresh concrete which can ultimately lead to the occurrence of plastic shrinkage cracking. Concrete is also batched and cast at various ambient temperatures which greatly influences the temperature development of the concrete after placement. There is a need to understand the influence of concrete temperature on the plastic cracking of concrete. This study investigated the temperature development over the thickness of a concrete slab when exposed to different initial concrete and ambient temperatures as well as the effect these factors have on plastic shrinkage cracking. This was achieved by experiments on concrete samples at varying temperatures while measuring the concrete temperature, pore water evaporation, shrinkage, settlement, setting times and plastic shrinkage cracking magnitude. These tests were conducted in a climate controlled chamber. It was concluded that exposure to higher initial concrete and ambient temperatures significantly increases the average temperature over the thickness of the concrete. The evaporation of pore water was higher when exposed to higher evaporation conditions. The plastic shrinkage, settlement and plastic shrinkage cracking were more severe in the presence of higher initial concrete and ambient temperatures even though the critical period and setting times were reduced due to an increase in the concrete temperature. Finally, the surface temperature of the concrete as tested in slabs up to 100 mm in thickness can be used as a good indication of the temperature development in the lower layers of the concrete.

An investigation of cracks caused by concrete shrinkage and temperature difference in common reinforced concrete bridge structures.

“…This occurrence is observable in Fig. 1 and has been reported in various research studies [19][20][21][22][23][24][25][26][27][28][29][30]. The phenomenon has garnered significant attention globally, with the cause of cracking believed to be attributed to the effects of concrete shrinkage and temperature differences, particularly during the early stages when these effects are most pronounced [4][5][6][7][8][9][10][11][12][13][14][15].…”

“…The temperature difference also plays a crucial role in influencing crack formation in immature concrete [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Either the heat of hydration of concrete or variations in outdoor temperature cause the temperature differences [3,[4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. In the context of hydration heat, temperatures recorded in laboratory environments or actual construction sites, especially for larger structures, can reach up to 90°C [4][5][6][7][8]…”

“…When a structure is subjected to a large load, cracks appear, and the accumulated deformations in the concrete due to shrinkage and temperature differences between steel and concrete are released, affecting the crack width. The progression of cracks over time is also influenced by several factors, including the configuration of steel and concrete structures and the characteristics of the structural shape and sizes [19][20][21][22]30]. Nowadays, research on crack development has shifted its focus towards specific structures, such as reinforced concrete pavement structures, retaining walls as well as some bridge parts [23][24][25][26][27][28][29][30].…”

Phân tích vết nứt do co ngót bê tông và nhiệt độ thay đổi trong các kết cấu cầu bê tông cốt thép phổ biến tại Việt Nam

“…Tuy vậy, trên thực tế, hiện tượng nứt vẫn xảy ra phổ biến như Hình 1 và ở các công trình nghiên cứu khác [7,8] cho dù kết cấu được coi là đáp ứng được yêu cầu chống nứt theo tiêu chuẩn thiết kế. Trên thế giới, hiện tượng này được quan tâm nhiều gần đây và nguyên nhân nứt được cho rằng do tác động của co ngót bê tông và nhiệt độ chênh lệch, đặc biệt là lúc bê tông còn non tuổi khi các hiệu ứng nói trên phát triển mạnh nhất [9][10][11][12][13][14][15][16][17][18].…”