A set of four commercially available multifilament glass-rovings with 320, 640, 1200, and 2400 tex embedded in concrete was investigated using pull-out tests and scanning electron microscopy. The increasing roving cross-section within this set arose from two geometrical factors, namely the number of filaments and the filament diameter. In general, pull-out loads and the pullout work increase with increasing roving cross-section, while the pull-out stress, the efficacy, and the roving penetration decrease. An attempt to separate the two geometrical factors revealed that an increase in the filament diameter reduced the mechanical performance of a roving to a much greater extent than an increase in the number of filaments. Consequently, effective textiles used for reinforced concrete should be made from a larger number of finer rovings such as the 640 tex rather than 2400 tex rovings.

ABSTRACT:The rheological behavior of a series of poly (ethylene oxide) melts containing nonhydrated cement is investigated using stress-sweep measurements. The influence of the polymer end-group-diol, monomethyl ether, and dimethyl ether-, molecular weight, and the particle volume fraction is examined. The data suggests that monomethyl ethers adsorb with their single OH group head-on on the cement surface, which reduces the interparticle friction and the viscosity, but mixtures based on monomethyl ethers exhibit shear-thickening behavior. The diols cause the formation of hydrogen-bonded particle networks leading to high viscosities, but these mixtures exhibit shear-thinning behavior due to the collapse of the network upon shearing. On increasing the particle volume fraction, the samples feature a nonlinear increase in viscosity. Fitting these data indicated that the maximum particle volume fraction is close to the random packing density of spheres and decreases with decreasing shear stress. As coating for glass rovings, the mixtures match the reinforcing performance of solventbased systems despite lower cement content.

Cement-in-polymer (c/p) dispersions allow the full utilisation of the reinforcing abilities of multifilament rovings in concrete. In this work the role of the polymer properties on the performance of the c/p dispersions is investigated and discussed. Two model polymers are chosen and c/p dispersions made with these are investigated regarding the water ingress velocity (NMR), the phase development during cement hydration (XRD), and the microstructure after cement hydration (SEM). Best mechanical performance is achieved with the hydrophobic poly(vinyl acetate) which regulates the water ingress and causes a slow hydration of the cement.