JPH0255254A - Improvement of adhesive strength between aggregate and cement paste - Google Patents

Abstract

PURPOSE:To enhance the breaking strength of an adhesion layer and obtain highly strong concrete by preliminarily adding a surfactant having good lubricating and penetrating functions to water to be mixed when the concrete is kneaded. CONSTITUTION:When cement and aggregate are mixed with each other and the mixture is further mixed with water to knead the concrete, a surfactant having good lubricating and penetrating functions is preliminarily added to the water. The surfactant includes an anionic penetrating agent such as sodium dodecylbenzene sulfonate or a nonionic penetrating agent such as nonylphenol ethylene oxide adduct.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for improving the adhesive strength between aggregate and cement paste to obtain high strength concrete.

(Prior Art) In order to make concrete with high compressive strength, it is hard mixed with a small proportion of water, and the lower the water-cement ratio, the higher the compressive strength can be in a linearly proportional relationship.

Additionally, in order to satisfy the required strength and slump, water reducing agents and AE agents are also mixed.

If we can reduce the water to a water-cement ratio of around 2526, we can predict that we will be able to produce concrete with a compressive strength of 1000 kg f/d, so we can increase the strength of cement paste and create high-quality concrete with a strength equal to or higher than this. aggregate was selected.

(Problem to be Solved by the Invention) However, even if high-strength cement paste and aggregate are used, if the bonding force between the two is insufficient, as shown in Figure 1, the aggregate 1 will bond with the load. Surrounding cement matrix 2
A minute gap 3 is grown between the two, and when subjected to a compressive load from above and below, inside the gap 3, as shown by the arrow in the figure,
Compression is applied from above and below, and at the same time a force is applied to bulge on both sides, and adhesive failure occurs at the interface between the aggregate 1 and cement matrix 2 before the aggregate 1 and cement matrix 2 are destroyed, making it impossible to maintain the desired strength.

FIG. 2 shows details of the joint surface between the cement paste 4 and the aggregate 1 after hardening. The bonding surface consists of amorphous calcium silicate hydrate mixed between a porous adhesive film 5 made of calcium hydroxide (Ca(OH)2) adhered to the surface of the aggregate 1 and scattered calcium hydroxide crystal plates 6. and an intermediate layer consisting of material 8.

Ettringite (3CaO-
AL O・3CaSOφ3ZH2o)9 is mixed.

It is known that even after concrete hardens, the porous adhesive film 5 made of calcium hydroxide is formed on the surface of the aggregate 1, which reduces the adhesive strength between the aggregate 1 and the cement paste 4. was.

The present invention has been made in view of the above-mentioned circumstances, and its object is to provide a method that can uniformly and uniformly make the joint surface thinner by reducing the thickness of the joint surface.

(Means for Solving the Problems) In order to achieve the above object, the method for improving the adhesive strength between aggregate and cement paste according to the present invention is to mix cement and aggregate, further add water, and knead concrete. When doing this, a surfactant having a lubricating or penetrating action is mixed in advance into the kneading water.

(Function) The surface tension of the mixed pure water is reduced by the action of the surfactant, and so-called "leakage" to cement particles and aggregates is improved.

As a result, the water film between the cement particles and the aggregate becomes thinner, resulting in dense concrete with a thin intermediate layer or adhesive film during curing, and a high adhesive strength.

(Example) Hereinafter, preferred embodiments of the present invention will be described in detail.

First, a surfactant having a lubricating or penetrating action is mixed into the kneading water.

Such surfactants include anionic penetrants. Examples include aerosol OT type, sodium dodecylbenzene sulfonate, sodium lauryl sulfate, sodium alkylnaphthalene sulfonate, butyl oleate sulfate, sulfonate, sulfate ester salt, and the like.

Alternatively, a nonionic penetrant may be used, such as an ethylene oxide adduct of nonylphenol or octyphenol.

Next, cement and aggregate are kneaded using the kneading water mixed with the surfactant.

The surface tension of the mixing water is very low due to the action of the surfactant, so it leaks easily to the cement particles and aggregates, and the water film of the mixing water that adheres to these surfaces becomes quite thin. ing.

(Effects) As explained in detail above, the present invention mixes a surfactant into water in advance to reduce the surface tension of the kneading water itself, and then mixes this into a mixture of cement and aggregate. Since water is poured in and kneaded, the influence of the kneading method and kneading time is small, and it is easy to maintain a uniformly good condition without any leakage between the cement paste and aggregate.Also, the AE agent mainly has foaming properties, and the water reducing agent While the main purpose of this is to reduce the unit water volume, the present invention uses a surfactant to reduce the surface tension of the mixing water in order to improve leakage between cement particles and between cement particles and aggregate. This has the effect of increasing the breaking strength of the adhesive layer due to its dense adhesive structure.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the stress distribution around the aggregate during compressive loading, and FIG. 2 is an explanatory diagram showing a model of the bonding surface between the cement paste and the aggregate. 1... Aggregate 2... Cement matrix 3... Voids 4... Cement paste 5... Adhesive film 6... ...Calcium hydroxide crystal plate 8...
Amorphous calcium silicate hydrate 9...Etrin guide Figure η

Claims (1)

[Claims] (1) When cement and aggregate are mixed and further water is added to mix concrete, a surfactant having a lubricating or penetrating action is mixed in advance in the mixing water. A method for improving the adhesive strength between wood and cement paste.