Green Concrete Performance Prediction Model And Its Application Research

With the widespread use of mineral admixtures green concrete,the demand and requirements for the performance prediction model of green concrete in the field of building engineering are greatly increased.Therefore,the establishment of accurate and comprehensive concrete performance prediction model accords with the development law of modern mineral admixtures green concrete.Based on the theory of mineral admixtures concrete compressible accumulation and activity effect analysis,this paper proposes the relevant factors about concrete working property and mechanical property,and through the analysis of the performance impact experiment and exhaustive search method and the parameter estimation method to modify the performance factors,thus the green mineral admixtures concrete work and mechanical performance prediction model are established.At the same time,the prediction model established in this paper is verified by experiment and compared with other prediction models.Finally,a reliable design method of green concrete mix design is proposed.The main research contents of this paper are summarized as follows:(1)Performance prediction factor that can represent pure cement concrete’s working performance—Free water factor(FW),which is the ratio of mixing water to the void volume of solid particle of concrete,is proposed.At the same time,it is proposed to modify FW by the working characteristic factor Cm of mineral admixture,to establish the Equivalent free water factor(EW)of mineral admixture concrete to quantitatively reflect the influence of mineral admixture’s own characteristics on concrete working performance.(2)Performance prediction factor that can represent the mechanical properties of concrete—Cement initial void factor(CIVF)is proposed,which reflects the dense distribution state of cement particles.Considering that physical packing and activity of mineral admixtures,the equivalent activity factor of mineral admixtures Aeq is proposed to modify CIVF,to establish Binder equivalent void factor(BEVF),and Cement equivalent void factor(CEVF)involving both physical packing and the effect of mineral admixtures activity;(3)When the water-cement ratio is between 0.4 and 0.55,FW is highly correlated with the pure cement concrete slump by 0.9969,and the bigger FW is,the bigger the concrete slump will be;In pure cement concrete,CEVF of cement particles is also highly correlated with the compressive strength of concrete by 0.9955,and the larger CEVF is,the smaller the compressive strength of concrete is.(4)By determining working characteristics factor Cm function in EW of the single mixing Fly ash(FA),ground granulated blast slag(GGBS),and mixed FA+GGBS concrete,EW which is a predictable only mixing and mixed concrete slump is established,and slump prediction model of mineral admixtures concrete(including pure cement concrete)is built.The correlation is 0.9515,and the slump prediction model is more comprehensive;(5)By determining the equivalent activity factor of mineral admixtures Aeq of the single mixing FA,GGBS and mixed FA+GGBS concrete,BEVF is established to predict concrete compressive strength of single and mixed mixtures,and compressive strength prediction model of mineral admixtures concrete(including pure cement concrete)is built.The correlation is 0.9780,the compressive strength prediction model to predict a more comprehensive;(6)When the concrete water-binder ratio and dosage of mineral admixtures are in a certain range,slump prediction model established by EW the average error is about 10%,and the comprehensive consideration of the variety of mineral admixtures,dosage and water-binder ratio many variable factors,avoid the single factor limitations of slump prediction established by the volume surplus coefficient;The average error of the compressive strength prediction model established based on BEVF is about 4%.Moreover,the compressive strength prediction model established by the modified specific strength method is simpler,more convenient to calculate,and easier to be popularized in practical engineering applications.(7)Based on the packing void factor φc*/φc,optimal sand ratio’s interval of 0.35～0.45 and optimal binder aggregate ratio’s interval of 0.12～0.18 are obtained.A mixing design method for green concrete with mineral admixtures is proposed in combination with the prediction model of concrete slump and compressive strength.