Research on the improvement of early strength of cement underlow temperature conditions
Cementing in deep water areas is facing the problem of low seabed temperature and a serious slowdown in the growth of ce-ment strength during cementing.This apaper mainly studied the improvement of early strength of cement at low temperature of 6℃from multiple aspects such as different types of cement mixtures,early strength agents,ultrafine cement,specific surface area,and ball milling methods.The results show that the compound silica fume has no effect on improving the early strength of cement at low tempera-ture.The reasonable combination of early strength accelerators such as sulphoalu minate cement,calcium sulphoalu minate(CSA)and lithium carbonate with Portland cement of a specific surface area of 500 kg/m2 can improve the compressive strength of cement at low temperature for 24 h to some extent,but the amount of addition or the price of added materials is high.The self-made early strength agent is used,the low-temperature early strength can achieve the same strengthening effect when the external dosage is between 2‰and 3‰.Adding ultra-fine cement or grinding cement to cement with different specific surface areas to improve its low-temperature strength depends on the cement fine particles content in the entire system.When the proportion of fine particles with the particle size below 3 μm reaches over 20%,the compressive strength of cement can reach 9 MPa at a low temperature of 6℃for 24 h.Compared to steel forging,it is easier to obtain the particle of the size below 3 μm using steel balls for grinding,but at the same time,the particles are prone to agglomeration,resulting in the 45 μm residue on the sieve will be much higher.
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