| During the manufacture of the concrete, a large amount of natural sands would beconsumed.And about20%chips which do not merely take up the land but also pollute theenvironment would be produced during the process of quarrying. Thus, the study on how touse chips to produce the concrete has two practical significances. Thus, the study on how touse chips to produce the concrete has both the technical and social significances: on the onehand, it could contributes to reducing the comsumption of non-renewable resources; On theother hand, it could transform the waste into useful materials and protect environment.On the basis of a lot of experiments in which the natural sands were replaced by chips,this thesis aims to analyze the influencing rule of chips on the formabilities and the strengthsof the specimen of cement mortar and concrete, study the feasibility and the optimal contentof chips used to replace the natural sands in specimens of cement mortar and concreterespectively as well as the appropriate way to mix chips and natural sands. The specificexperimental content are as follows: the reasonable amount of chips used to replace thenatural sands in specimens of cement and the appropriate way to mix chips and natural sandswere studied; Mountain flour considered as a kind of mineral admixture was mixed into theconcrete to study its effect on the workability and mechanical property of the concrete.Through the exoeriments, the thesis got the following major findings:1) The chips can be used as a kind of material which is suitable for replacing the naturalsands. As long as the proportion is proper, the mixing of chips has little effect on thereduction of strengths of the specimen of cement mortar and concrete.2) The optimal rate of substitution (substitute chips for natural sands) is15%.Compared with the reference specimen of cement mortar, the decreases in strength ofspecimen in which the natural sands were replaced by chips enhance as the chips increase,while when the mixing amount is15%，the decreases of both the28d bending strength and thecompressive strength diminish.3) The necessary treatment of the chips, water-reducing agent and fly ash couldimprove the strength of chips-cement mortar specimens. With the same rate of substitution,the28d bending strength and the compressive strength of the chips-cement mortar specimenswhich the chips that are less than0.15mm in diamete have been removed are increased by13.1%and12.3%respectively compared with the basic specimens.And the rate will increaseby17.1%and6.0%respectively after mixing with0.7%water-reducing agent and15%flyash.4) The necessary treatment of the chips, water-reducing agent and fly ash could alsoimprove the strength of chips-concrete specimens. The mixing of chips could improve theworkability of the concrete but the compressive strength of the concrete will decrease with theincorporation of chips. When the rate of substitution (substitute chips for natural sands) is 15%, the early and late compressive strength of the concrete will reduce to the minimum;After the necessary treatment, the7d and the28d compressive strength will increase by4.0%and2.6%respectivly and the rate will increase by19.5%and18.6%respectively throughadding the water-reducing agent and fly ash.5) Mountain flour could improve both the working performance and the compressivestrength of the concrete. Mountain flour could be considered as a kind of mineral admixtureand could be mixed into the concrete with water-reducing agent. When their mixing amount is20%, the early and late strength of the concrete will increase to the maximum which are25.5%and13.4%respectively compared with the basic specimens.6) The strength of the concrete could not be guaranteed by merely substituting mountainflour for equivalent cement Compared with the basic spicemen, the workability and thestrength of the concrete will decrease when substituting mountain flour for equivalent cement.At the same time, the decreases of the strength of the concrete will increase with theincorporation of mountain flour. |
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