Experimental Study On The Performance And Nondestructive Testing Of High-flowing Concrete With Compound Admixtures

The high-flowing concrete due to its good workability, higher strength grade, andexcellent durability, have been developed very quickly in China. Mineral admixture hasbecome a necessary component of the preparation of high-flowing concrete. Compounddifferent kinds of admixtures can play complementary advantages and the superimposedeffect in concrete, whose research has become a hot topic at present. The compoundmineral admixture research has mainly focused on the performance of common mineraladmixture. As a new type of mineral admixture, ground fine fluidized bed combustionashes compound with common admixture has basically blank research on the influence ofconcrete performance. As people pay more attention to the quality of engineering, thenondestructive testing technology is more and more mature. Owing to the characteristics oflarge dosage of cementitious materials and admixtures of high-flowing concrete withcompound admixtures, whether the national unified strength-detecting curve of ordinaryconcrete (or pumpable concrete) can be used for the strength-detecting in compoundmineral admixture high-flowing concrete or not, it still needs further experimentalverification.This paper employ three three kinds of admixture included fly ash, slag powder,ground fine fluidized bed combustion ashes. Influence on workability, mechanical property,anti-carbonization and anti-chloride ion penetration is experimentally studied by the type,compound mode and dosage of admixture. Based on those researches, the correlationbetween the ultrasonic-velocity and rebound value, ultrasonic-velocity value and reboundvalue with the measured compressive strength are regressed by the rebound method,ultrasonic method and ultrasonic-rebound method of three kinds of nondestructive strengthtesting method. The main conclusions are as follows:(1) Under the condition of compound admixtures,①The slump of high-flowingconcrete mixture increases with increasing the dosage of slag powder. However, while theslump flow increase first and then decrease, peak in the slag powder dosage of30%;②Ithas a negative effect on the slump and slump flow of high-flowing concrete withincreasing the dosage of fly ash (or ground fine fluidized bed combustion ashes).(2) Under the condition of ground fine fluidized bed combustion ashes compoundwith fly ash and slag powder, the influence of compound mineral admixture on thecompressive strength of high-flowing concrete has basically similar law:①At the sametotal dosage of admixture, the compressive strength decrease is not obvious with thewater-binder ratio increasing at the range of0.4to0.5;②At the same water-binder ratio,the compressive strength of high-flowing concrete decrease with increasing the dosage ofadmixture.(3) In view of three kinds of relations included ultrasonic-velocity and rebound valueto compressive strength, ultrasonic-velocity value to compressive strength, and reboundvalue to compressive strength at different ages of high-flowing concrete. Under reboundmethod and ultrasonic-rebound method by the corresponding function relationships, the fitting of special strength-detecting curve is regressed to meet the accuracy requirements ofcurrent relative regulation.(4) Under the condition of ground fine fluidized bed combustion ashes compoundwith fly ash and slag powder, the influence of compound mineral admixture on theanti-carbonization and anti-chloride ion penetration of high-flowing concrete has basicallysimilar law:①Under the condition of three-combined with ground fine fluidized bedcombustion ashes, fly ash and slag powder, double-combined with fly ash and slag powder,double-combined with ground fine fluidized bed combustion ashes and fly ash, thehigh-flowing concrete respectively containing the water-binder ratio of0.45,0.5and0.55,whose admixture dosage should be respectively controlled within50%,50%and30%tomeet the requirements of slab’s minimum protective layer thickness of15mm in code forstructural design;②The negative influence of early and late anti-carbonation onhigh-flowing concrete from big to small order are slag powder(or fly ash), ground finefluidized bed combustion ashes, and ground fine fluidized bed combustion ashes, fly ash,slag powderp;③The regression correlation of carbonation depth and age of high-flowingconcrete, and are in good agreement with the measured values;④According to the testresults and the current related technical specifications and standards,15groups ofhigh-flowing concrete mostly meet the role of the environment50years F level, and themost belong to low permeability concrete level;⑤adding the dosage of admixture is themain technical measure to improve the anti-chloride ion penetration for high-flowingconcrete.