Hydroxypropyl methyl cellulose (HPMC) has excellent thickening and can be used as an excellent concrete anti-dispersant.HPMC has been widely used in the construction industry. Anti-dispersion test Anti-dispersant is an important technical index to measure the quality of anti-dispersant.
HPMC is a water soluble polymer compound, also known as water soluble resin or water soluble polymer, is to increase the consistency of the mixing water by increasing the viscosity of the mixture, is a hydrophilic polymer material, can dissolve in water and form a solution or dispersion.It can be seen that when the amount of naphthalene series efficient water reducing agent increases, the incorporation of water reducing agent will reduce the anti-dispersion of newly mixed cement mortar.
This is because the naphthalene system efficient water reducing agent belongs to the surfactant, when the water reducer added to the mortar, water reducing agent in the surface of the cement particles surface with the same charge, the electric repulsion makes the cement particles form flocculation structure is separated, the water released in the structure, will cause part of the loss of cement water.At the same time, with the increase of HPMC mixing, the dispersion of new cement mortar is better and better.
Strength characteristics of the concrete HPMC underwater non-dispersed concrete admixture is applied in the bridge foundation engineering of Dantong Line (Dandong to Tonghua) expressway, and the design strength grade is C25. After the basic test, the dosage of cement is 400kg, composite silica cement is 25 kg/m3, HPMC is 06% of cement dosage, water-ash ratio is 042, sand rate is 40%, 8%, air concrete test 28d strength is 426 MPa, underwater pouring height of 60mm is 364MPa, the strength ratio of water formed concrete and air is 84.8%, with significant effect.it is thus clear that
(1) The addition of HPMC has obvious retarding effect on the mortar mixture. With the increase of HPMC mixing amount, the condensation time of mortar is extended.
(2) Newly mixed cement mortar mixed with hydroxypropyl methyl cellulose has good cohesion properties and almost no bleeding phenomenon.
(3) HPMC mixing amount and mortar water demand are first reduced and then significantly increased.
(4) The incorporation of water-reducing agent improves the problem of increasing water demand for mortar, but its incorporation must be reasonably controlled.Otherwise, there is (4) the incorporation of water-reducing agent improves the problem of increasing the water demand of mortar, but its mixing amount must be reasonably controlled, otherwise there is The underwater anti-dispersion of newly mixed cement mortar will be reduced
(5) There is little structural difference between the cement clean slurry specimen mixed with HPMC and the blank specimen, pouring in water and in air The difference between the structure and the density of the poured cement net slurry specimen is not.