What is the effect of adding hydroxypropyl methylcellulose to concrete materials?

Hydroxypropyl methylcellulose (HPMC for short) has excellent thickening properties and can be used as an excellent concrete anti-dispersion agent. In recent years, with the continuous development of external wall insulation technology and the continuous progress of cellulose production technology , and the excellent characteristics of HPMC itself, HPMC has been widely used in the construction industry.

1. Strength characteristics of concrete

       Hydroxypropyl methylcellulose underwater non-dispersible concrete admixture is used in the bridge foundation engineering of expressway, and the design strength level is C25. According to the basic test, the amount of cement is 400 kg, the compounded silica fume is 25 kg/m3, the optimal amount of hydroxypropyl methylcellulose is 0.6% of the cement amount, the water-cement ratio is 0.42, and the sand rate is 40%. The output of naphthalene-based high-efficiency superplasticizer is 8% of the amount of cement. The average strength of concrete specimens in the air for 28 days is 42.6 MPa. The strength ratio of formed concrete to air-formed is 84.8%, and the effect is remarkable.

2. Anti-dispersion test

Anti-dispersion is an important technical index to measure the quality of anti-dispersion agent. Hydroxypropyl methylcellulose is a water-soluble polymer compound, also known as water-soluble resin or water-soluble polymer. It increases the consistency of the mixture by increasing the viscosity of the mixing water. It is a hydrophilic polymer material. It can be dissolved in water to form a solution or dispersion. Experiments show that when the amount of naphthalene-based high-efficiency superplasticizer increases, the addition of superplasticizer will reduce the dispersion resistance of freshly mixed cement mortar. This is because the naphthalene-based high-efficiency water reducer is a surfactant. When the water reducer is added to the mortar, the water reducer will be oriented on the surface of the cement particles to make the surface of the cement particles have the same charge. This electric repulsion makes the cement particles form The flocculation structure of the cement is dismantled, and the water wrapped in the structure is released, which will cause the loss of part of the cement. At the same time, it was found that with the increase of HPMC content, the dispersion resistance of fresh cement mortar was getting better and better.