Rheology of grout for preplaced aggregate concrete. Investigation on the effect of different materials on the rheology of Portland cement based grouts and their role in the production of preplaced aggregate concrete.

摘要

Preplaced aggregate concrete (PAC) is produced by grouting high workability cementudbased grouts among the voids of compacted coarse aggregate mass. Because of its lowudshrinkage, PAC has been used for many repair jobs like; tunnel lines, dams and bridgeudpiers. Moreover, it has been used for underwater construction.udGrout has a major effect on the properties of produced PAC and well defined groutudcontrols the properties of resulted PAC. The effect of types and amount of powderudmaterials, admixtures, sand and water content on the properties of fresh and hardenedudgrout for the production of PAC have been investigated. Tests on hardened grout andudPAC properties have also been carried out to investigate the most important effects. Audcorrelation between hardened properties of grout and PAC has also been analyzed.udGrout rheology using four different gradation sands at two different cement-sand and atuddifferent w/c ratios ratios has been identified experimentally; no added chemicaludadmixtures or mineral additives had first employed, then superplasticizer (SP) wasudadded at 2% and 1%, and finally a combination of 1% SP and pulverized fuel ash (Pfa)udat 20% of the cement weight was employed for all mixes. Grout tests have included twoudpoint workability tests by the Viskomat NT, flow time funnel test, Colcrete flow meterudtest, and water bleeding test. After that, eighteen grout mixes with high workability wereudproduced using three different sands at three w/c ratios and two c/s ratios with 1% SPudand Pfa at 20% of the cement weight were designed. Eighteen hardened grout and PACudthen produced and their compressive strength and sorptivity were tested.udGrout rheology can be defined by the rheology of cement paste employed and theudinternal distance between sand particles. The effect of sand surface texture on groutudrheology is important at very low internal distances. Fresh grout yield stress is the mostudimportant property which gives the same degree of sensitivity for all grouts regardlessudthe material type and content used in the mix. There are strong relations betweenudcompressive strength of grout and PAC, but less correlation between them in sorptivityudtest because of the effect high quantity of coarse aggregate of PAC. Sorptivity of PAC isudlow comparing with different kinds of concrete suggesting its advantage for underwaterudconstruction.