Hydration, Hardening And Compressive Strength Of Class G Oil Well Cemnet Under High Temperature

Based on foundational theory and researching results of Portland cement, hydration process, composition of hydration products, morphology and microstructure of hydration products in hardening cement paste and strength property of Jiahua Class G Oilwell Cement are tested and studied systematically and intensively for the range of temperature from 25℃ to 200 ℃ , by using DSC, XRD, SEM, Static Gel Strength Analyzer, High-Temperature-High-Pressure Curing Chamber etc.. Nature and feature of hydration and compressive strength which are affected by temperature, additives and added amount of additives are analyzed and evaluated in detail. Conclusions such as hydration rate and hydration process can be accelerated with the increase of temperature, and at higher temperatures there are the trend to overlap the exothermic peaks of C3A, C3S and C2S one another are given. And revealed the nature and characteristics of the changes of main hydration products which vary with temperature and silica sand. When temperatures exceed 110℃ there are a lot of C2H products for pure cement slurry and when added some silica sand to cement slurry there are products C5S6H5 below 150℃ and products C6S6H above 150℃. Varying characteristics of morphology, microstructure and binding form of hydration products in hardening cement paste are given. Revealed relations among acting characteristics of silica sand, changing characteristics of porosity and conditions such as temperature, additives etc. Nature of the influence of temperature, silica sand and its amount on hydration process, hydration products and microstructure is presented. Critical temperatures which the strength begins to decline have been determined to be 110℃ and 150℃ respectively. Reasonable amounts of silica sand which will be added to cement slurry to enhance the strength of hardening paste are determined to be 30~45%. For pure cement slurry when the temperatures exceed 110℃ there are decreasing tendency on the later strength development curve. And for slurries containing silica sand there are increasing tendency for 110~150℃ in form of two stage and for exceeding 150℃ in only one stage form. And temperature limits for proper applications of vary kinds of additives are assessed. The characteristics of the influence of additives on the compressive strength are given. The nature relationships among temperature, additives, hydration process and the change of strength properties are revealed.