Experimental Study On Composite Mixing Process Of Cement Concrete And Their Effects

Mixing is the most basic preparation method of concrete production, and differentmixing processes result in different structures and performance of cement concrete.Thisresearch studied the effects of several composite mixing technologies for pavementperformance and coarse aggregates’ structures of cement concrete, in hopes that, determine anoptimal mixing process of cement concrete construction to improve its performance.The mechanism analysis of composite mixing process showed that secondary compositemixing techniques cause the gradient of water cement ratio of interfacial transition zone,improve the dispersion degree and hydration of cement particles, slowdown the phenomena ofmoisture migration to the aggregate interface, accordingly improve the mixing quality andenhance the strength of concrete. But to the interlocking-dense cement concrete, the coarseaggregates enveloped with cement paste and the cement wrapped sandstones are difficult toform a complete “shell” and the concrete mixing nonuniformly, result in the reduce ofstrength.Determine the optimal first water addition of the coarse aggregates enveloped withcement paste and the cement wrapped sandstones. The experimental results of the mixingquality and pavement performance showed that secondary composite mixing techniques,especially the coarse aggregates enveloped with cement paste and the cement wrappedsandstones, can improve the uniformity, strength and wear resistance of normal concrete; theprimary mixing of mortar have especially significant effects on the uniformity, strength andwear resistance of the interlocking-dense cement concrete, but the coarse aggregatesenveloped with cement paste and the cement wrapped sandstones make the reduce of itsperformance.The concrete meso-structure’s analysis based on the CT technology showed thatsecondary composite mixing techniques can improve the distribution of the coarse aggregatesof normal concrete, especially the coarse aggregates enveloped with cement paste and thecement wrapped sandstones. The primary mixing of mortar can improve the distribution ofthe coarse aggregates of the interlocking-dense cement concrete, make it more uniform andincrease surface contact of coarse aggregates, improve the interlocking effects; but the coarseaggregates enveloped with cement paste and the cement wrapped sandstones cause the unevendistribution of coarse aggregates, difficult to form interlocking structure. Put forward thequantitative indexes of coarse aggregates contact degree, and establish the relationshipbetween these indexes and the compressive strength.