Mechanical And Shrinkage Properties Of Acid Activated Cement-based Materials

Reducing the consumption of energy and resources and carbon emissions in the cement industry,and increasing the utilization of industrial waste slag have become the key to achieving energy-saving,emission reduction,low-carbon economy and sustainable development in China.Acid-activated cement-based materials can not only reduce the amount of cement,lower the cost,but also increase the utilization of new building materials.This is of great significance for saving resources and energy.Based on the physical and chemical properties of raw materials,this paper derives the best mix ratio by analyzing the factors that influence the strength of acid-activated cement-based materials.The hydration mechanism of acid-activated cement-based materials was analyzed by means of microscopic detection and hydration heat tests.The effect of adding fibers on the strength of the acid-activated cementitious materials leads to the best type of fiber and the best method of addition.Based on the above studies,the influence factors such as the amount of acetic acid and curing methods on the shrinkage performance of acid-activated cement-based materials are analyzed.The study of the mechanical properties of acid-activated cement-based materials shows that the effect of acetic acid is better than hydrochloric acid or sulfuric acid.When the content of acetic acid is 5%,the compressive strength of acid-activated cement-based material can reach 61.14 MPa for 28 days,which meets the requirement of P·O52.5 cement against compressive strength;When the content of acetic acid is 5% and the content of fly ash with slag is 50%,the compressive strength of acid-activated cement-based material can reach47.16 MPa for 28 days,which meets the requirement of P·O42.5 cement compressive strength.The results of microscopic examination of acid-activated cement-based materials show that when acetic acid is added,the cement hydration reaction is intense,the hydration temperature of the cement rises sharply,the heat release increases,and the rate of heat release increases.On 7th day,almost no cracks can be found in the cement stone mixed with acetic acid,and the compactness is high,the porosity is low,and the harmful pores are greatly reduced.The study of the mechanical properties of fiber-reinforced acid-activated cement-based materials shows that the enhancement effect of the double-doped system is higher than that of the single doped system.When single fiber is added,the reinforcing effect of glass fiber is better than that of carbon fiber;when the content of glass fiber is 2%,the flexural strength ofacid-activated cement-based specimen can reach 10.92 Mpa for 28 days,and the compressive strength can reach 66.28 Mpa for 28 days.The study of shrinkage performance of acid-activated cement-based materials shows that the shrinkage-deformation curve is divided into two phases.In the first phase,the curve growth speed is fast,approximately linear growth,but in the second phase the growth rate of the curve slows down;Acetic acid has an inhibitory effect on the shrinkage of cement stone.With the increase of acetic acid content,the inhibitory effect is better.The glass fiber also has an inhibitory effect on the shrinkage of the cement stone,and the addition of double-doped glass fiber is more effective than the single-doped glass fiber.