The Flow Properties of Some Chemical Additives Used in Modification of Natural Zeolite for Cement Concrete

Aim: To assess the effectiveness of water-reducing additives in relation compressive strength of cement pastes.

Methodology: Experimental study, Materials used were natural zeolite from Egypt, with a grain size up to 0.08 mm, containing zeolite (clinoptilolite) - 75%, and ratio Si / Al content is 4.8-5.4; Portland cement CEM I 42.5 R., and a modified viscometer with an internal diameter of 25 mm and 50 mm height was used. Changes in water demand was evaluated by value of flowing on the border of gravity spread test.

Results: Natural zeolites with low W/S ratio (water solid ratio) equals to 0.4 was well plasticized at low dosages (0.25%) of additive Melflux. The most effective form of chemical additives was SP-3, which at the dosage of 0.6% reduces the W/S ratio of zeolite pastes by 20%. In addition, Melflux was chosen as the most effective in cement systems, although it is less efficient in natural zeolite, but the amount accepted is 5%, also Melflux was compared with pure cement paste in range from 0.1 to 0.75% by weight of solids, which determines need of concrete with high strength.

Conclusion: Cement paste containing natural zeolite exhibit improved resistance to water requirement by using chemical additives. However, adding natural zeolite in presence of additive Melflux decreases water demand of mixtures which directly increase the compressive strength of cement paste.