Influence of Cement Types on Concrete Properties of Double-Block Ballastless Track Bed

Taking double-block ballastless track bed concrete as the object, the influences of low-heat Portland cement (P·LH) and normal Portland cement (P·O) on mechanical properties, adiabatic temperature rise, dry-shrinkage and cracking sensitivity of track bed concrete are studied. The results show that, the track bed concrete prepared with two types of cement can meet the design requirements of C40 concrete. It is also noticed that the strength development of the two is different. That is, the early strength development of track bed concrete with P·LH is lower and the lately strength development is slightly higher than that of concrete with P·O, the 3d and 56d compressive strength of track bed concrete with P·LH is 41% and 9% lower than that of the latter, and 5% higher than that of the latter at age 90d. P·LH can reduces the adiabatic temperature rise of track bed concrete, the 1d, 3d and 7d adiabatic temperature rise of track bed concrete with P·LH is 34%, 24% and 20% lower than that of concrete with P·O, respectively. P·LH can reduce the dry-shrinkage of track bed concrete significantly, the 1d and 3d dry-shrinkage value is 70% and 30% lower than that of concrete with P·O, respectively, and even at shrinkage development stable age with 180d, the dry-shrinkage of former is also slightly lower than the latter. Cracking sensitivity evaluated by the concrete ring test shows that, the cracking sensitivity of track bed concrete with P·LH is significantly decrease and no cracking occurred within 28d, but the concrete with P·O was cracked at age 10d.